From: Mauro Carvalho Chehab Date: Wed, 12 Jun 2019 17:52:48 +0000 (-0300) Subject: docs: kbuild: convert docs to ReST and rename to *.rst X-Git-Url: http://git.lede-project.org./?a=commitdiff_plain;h=cd238effefa28fac177e51dcf5e9d1a8b59c3c6b;p=openwrt%2Fstaging%2Fblogic.git docs: kbuild: convert docs to ReST and rename to *.rst The kbuild documentation clearly shows that the documents there are written at different times: some use markdown, some use their own peculiar logic to split sections. Convert everything to ReST without affecting too much the author's style and avoiding adding uneeded markups. The conversion is actually: - add blank lines and identation in order to identify paragraphs; - fix tables markups; - add some lists markups; - mark literal blocks; - adjust title markups. At its new index.rst, let's add a :orphan: while this is not linked to the main index.rst file, in order to avoid build warnings. Signed-off-by: Mauro Carvalho Chehab Signed-off-by: Jonathan Corbet --- diff --git a/Documentation/admin-guide/README.rst b/Documentation/admin-guide/README.rst index a582c780c3bd..cc6151fc0845 100644 --- a/Documentation/admin-guide/README.rst +++ b/Documentation/admin-guide/README.rst @@ -227,7 +227,7 @@ Configuring the kernel "make tinyconfig" Configure the tiniest possible kernel. You can find more information on using the Linux kernel config tools - in Documentation/kbuild/kconfig.txt. + in Documentation/kbuild/kconfig.rst. - NOTES on ``make config``: diff --git a/Documentation/kbuild/headers_install.rst b/Documentation/kbuild/headers_install.rst new file mode 100644 index 000000000000..1ab7294e41ac --- /dev/null +++ b/Documentation/kbuild/headers_install.rst @@ -0,0 +1,51 @@ +============================================= +Exporting kernel headers for use by userspace +============================================= + +The "make headers_install" command exports the kernel's header files in a +form suitable for use by userspace programs. + +The linux kernel's exported header files describe the API for user space +programs attempting to use kernel services. These kernel header files are +used by the system's C library (such as glibc or uClibc) to define available +system calls, as well as constants and structures to be used with these +system calls. The C library's header files include the kernel header files +from the "linux" subdirectory. The system's libc headers are usually +installed at the default location /usr/include and the kernel headers in +subdirectories under that (most notably /usr/include/linux and +/usr/include/asm). + +Kernel headers are backwards compatible, but not forwards compatible. This +means that a program built against a C library using older kernel headers +should run on a newer kernel (although it may not have access to new +features), but a program built against newer kernel headers may not work on an +older kernel. + +The "make headers_install" command can be run in the top level directory of the +kernel source code (or using a standard out-of-tree build). It takes two +optional arguments:: + + make headers_install ARCH=i386 INSTALL_HDR_PATH=/usr + +ARCH indicates which architecture to produce headers for, and defaults to the +current architecture. The linux/asm directory of the exported kernel headers +is platform-specific, to see a complete list of supported architectures use +the command:: + + ls -d include/asm-* | sed 's/.*-//' + +INSTALL_HDR_PATH indicates where to install the headers. It defaults to +"./usr". + +An 'include' directory is automatically created inside INSTALL_HDR_PATH and +headers are installed in 'INSTALL_HDR_PATH/include'. + +The command "make headers_install_all" exports headers for all architectures +simultaneously. (This is mostly of interest to distribution maintainers, +who create an architecture-independent tarball from the resulting include +directory.) You also can use HDR_ARCH_LIST to specify list of architectures. +Remember to provide the appropriate linux/asm directory via "mv" or "ln -s" +before building a C library with headers exported this way. + +The kernel header export infrastructure is maintained by David Woodhouse +. diff --git a/Documentation/kbuild/headers_install.txt b/Documentation/kbuild/headers_install.txt deleted file mode 100644 index f0153adb95e2..000000000000 --- a/Documentation/kbuild/headers_install.txt +++ /dev/null @@ -1,50 +0,0 @@ -Exporting kernel headers for use by userspace -============================================= - -The "make headers_install" command exports the kernel's header files in a -form suitable for use by userspace programs. - -The linux kernel's exported header files describe the API for user space -programs attempting to use kernel services. These kernel header files are -used by the system's C library (such as glibc or uClibc) to define available -system calls, as well as constants and structures to be used with these -system calls. The C library's header files include the kernel header files -from the "linux" subdirectory. The system's libc headers are usually -installed at the default location /usr/include and the kernel headers in -subdirectories under that (most notably /usr/include/linux and -/usr/include/asm). - -Kernel headers are backwards compatible, but not forwards compatible. This -means that a program built against a C library using older kernel headers -should run on a newer kernel (although it may not have access to new -features), but a program built against newer kernel headers may not work on an -older kernel. - -The "make headers_install" command can be run in the top level directory of the -kernel source code (or using a standard out-of-tree build). It takes two -optional arguments: - - make headers_install ARCH=i386 INSTALL_HDR_PATH=/usr - -ARCH indicates which architecture to produce headers for, and defaults to the -current architecture. The linux/asm directory of the exported kernel headers -is platform-specific, to see a complete list of supported architectures use -the command: - - ls -d include/asm-* | sed 's/.*-//' - -INSTALL_HDR_PATH indicates where to install the headers. It defaults to -"./usr". - -An 'include' directory is automatically created inside INSTALL_HDR_PATH and -headers are installed in 'INSTALL_HDR_PATH/include'. - -The command "make headers_install_all" exports headers for all architectures -simultaneously. (This is mostly of interest to distribution maintainers, -who create an architecture-independent tarball from the resulting include -directory.) You also can use HDR_ARCH_LIST to specify list of architectures. -Remember to provide the appropriate linux/asm directory via "mv" or "ln -s" -before building a C library with headers exported this way. - -The kernel header export infrastructure is maintained by David Woodhouse -. diff --git a/Documentation/kbuild/index.rst b/Documentation/kbuild/index.rst new file mode 100644 index 000000000000..42d4cbe4460c --- /dev/null +++ b/Documentation/kbuild/index.rst @@ -0,0 +1,27 @@ +:orphan: + +=================== +Kernel Build System +=================== + +.. toctree:: + :maxdepth: 1 + + kconfig-language + kconfig-macro-language + + kbuild + kconfig + makefiles + modules + + headers_install + + issues + +.. only:: subproject and html + + Indices + ======= + + * :ref:`genindex` diff --git a/Documentation/kbuild/issues.rst b/Documentation/kbuild/issues.rst new file mode 100644 index 000000000000..9fdded4b681c --- /dev/null +++ b/Documentation/kbuild/issues.rst @@ -0,0 +1,11 @@ +Recursion issue #1 +------------------ + + .. include:: Kconfig.recursion-issue-01 + :literal: + +Recursion issue #2 +------------------ + + .. include:: Kconfig.recursion-issue-02 + :literal: diff --git a/Documentation/kbuild/kbuild.rst b/Documentation/kbuild/kbuild.rst new file mode 100644 index 000000000000..e774e760522d --- /dev/null +++ b/Documentation/kbuild/kbuild.rst @@ -0,0 +1,265 @@ +====== +Kbuild +====== + + +Output files +============ + +modules.order +------------- +This file records the order in which modules appear in Makefiles. This +is used by modprobe to deterministically resolve aliases that match +multiple modules. + +modules.builtin +--------------- +This file lists all modules that are built into the kernel. This is used +by modprobe to not fail when trying to load something builtin. + +modules.builtin.modinfo +-------------------------------------------------- +This file contains modinfo from all modules that are built into the kernel. +Unlike modinfo of a separate module, all fields are prefixed with module name. + + +Environment variables +===================== + +KCPPFLAGS +--------- +Additional options to pass when preprocessing. The preprocessing options +will be used in all cases where kbuild does preprocessing including +building C files and assembler files. + +KAFLAGS +------- +Additional options to the assembler (for built-in and modules). + +AFLAGS_MODULE +------------- +Additional module specific options to use for $(AS). + +AFLAGS_KERNEL +------------- +Additional options for $(AS) when used for assembler +code for code that is compiled as built-in. + +KCFLAGS +------- +Additional options to the C compiler (for built-in and modules). + +CFLAGS_KERNEL +------------- +Additional options for $(CC) when used to compile +code that is compiled as built-in. + +CFLAGS_MODULE +------------- +Additional module specific options to use for $(CC). + +LDFLAGS_MODULE +-------------- +Additional options used for $(LD) when linking modules. + +HOSTCFLAGS +---------- +Additional flags to be passed to $(HOSTCC) when building host programs. + +HOSTCXXFLAGS +------------ +Additional flags to be passed to $(HOSTCXX) when building host programs. + +HOSTLDFLAGS +----------- +Additional flags to be passed when linking host programs. + +HOSTLDLIBS +---------- +Additional libraries to link against when building host programs. + +KBUILD_KCONFIG +-------------- +Set the top-level Kconfig file to the value of this environment +variable. The default name is "Kconfig". + +KBUILD_VERBOSE +-------------- +Set the kbuild verbosity. Can be assigned same values as "V=...". + +See make help for the full list. + +Setting "V=..." takes precedence over KBUILD_VERBOSE. + +KBUILD_EXTMOD +------------- +Set the directory to look for the kernel source when building external +modules. + +Setting "M=..." takes precedence over KBUILD_EXTMOD. + +KBUILD_OUTPUT +------------- +Specify the output directory when building the kernel. + +The output directory can also be specified using "O=...". + +Setting "O=..." takes precedence over KBUILD_OUTPUT. + +KBUILD_DEBARCH +-------------- +For the deb-pkg target, allows overriding the normal heuristics deployed by +deb-pkg. Normally deb-pkg attempts to guess the right architecture based on +the UTS_MACHINE variable, and on some architectures also the kernel config. +The value of KBUILD_DEBARCH is assumed (not checked) to be a valid Debian +architecture. + +ARCH +---- +Set ARCH to the architecture to be built. + +In most cases the name of the architecture is the same as the +directory name found in the arch/ directory. + +But some architectures such as x86 and sparc have aliases. + +- x86: i386 for 32 bit, x86_64 for 64 bit +- sh: sh for 32 bit, sh64 for 64 bit +- sparc: sparc32 for 32 bit, sparc64 for 64 bit + +CROSS_COMPILE +------------- +Specify an optional fixed part of the binutils filename. +CROSS_COMPILE can be a part of the filename or the full path. + +CROSS_COMPILE is also used for ccache in some setups. + +CF +-- +Additional options for sparse. + +CF is often used on the command-line like this:: + + make CF=-Wbitwise C=2 + +INSTALL_PATH +------------ +INSTALL_PATH specifies where to place the updated kernel and system map +images. Default is /boot, but you can set it to other values. + +INSTALLKERNEL +------------- +Install script called when using "make install". +The default name is "installkernel". + +The script will be called with the following arguments: + - $1 - kernel version + - $2 - kernel image file + - $3 - kernel map file + - $4 - default install path (use root directory if blank) + +The implementation of "make install" is architecture specific +and it may differ from the above. + +INSTALLKERNEL is provided to enable the possibility to +specify a custom installer when cross compiling a kernel. + +MODLIB +------ +Specify where to install modules. +The default value is:: + + $(INSTALL_MOD_PATH)/lib/modules/$(KERNELRELEASE) + +The value can be overridden in which case the default value is ignored. + +INSTALL_MOD_PATH +---------------- +INSTALL_MOD_PATH specifies a prefix to MODLIB for module directory +relocations required by build roots. This is not defined in the +makefile but the argument can be passed to make if needed. + +INSTALL_MOD_STRIP +----------------- +INSTALL_MOD_STRIP, if defined, will cause modules to be +stripped after they are installed. If INSTALL_MOD_STRIP is '1', then +the default option --strip-debug will be used. Otherwise, +INSTALL_MOD_STRIP value will be used as the options to the strip command. + +INSTALL_HDR_PATH +---------------- +INSTALL_HDR_PATH specifies where to install user space headers when +executing "make headers_*". + +The default value is:: + + $(objtree)/usr + +$(objtree) is the directory where output files are saved. +The output directory is often set using "O=..." on the commandline. + +The value can be overridden in which case the default value is ignored. + +KBUILD_SIGN_PIN +--------------- +This variable allows a passphrase or PIN to be passed to the sign-file +utility when signing kernel modules, if the private key requires such. + +KBUILD_MODPOST_WARN +------------------- +KBUILD_MODPOST_WARN can be set to avoid errors in case of undefined +symbols in the final module linking stage. It changes such errors +into warnings. + +KBUILD_MODPOST_NOFINAL +---------------------- +KBUILD_MODPOST_NOFINAL can be set to skip the final link of modules. +This is solely useful to speed up test compiles. + +KBUILD_EXTRA_SYMBOLS +-------------------- +For modules that use symbols from other modules. +See more details in modules.txt. + +ALLSOURCE_ARCHS +--------------- +For tags/TAGS/cscope targets, you can specify more than one arch +to be included in the databases, separated by blank space. E.g.:: + + $ make ALLSOURCE_ARCHS="x86 mips arm" tags + +To get all available archs you can also specify all. E.g.:: + + $ make ALLSOURCE_ARCHS=all tags + +KBUILD_ENABLE_EXTRA_GCC_CHECKS +------------------------------ +If enabled over the make command line with "W=1", it turns on additional +gcc -W... options for more extensive build-time checking. + +KBUILD_BUILD_TIMESTAMP +---------------------- +Setting this to a date string overrides the timestamp used in the +UTS_VERSION definition (uname -v in the running kernel). The value has to +be a string that can be passed to date -d. The default value +is the output of the date command at one point during build. + +KBUILD_BUILD_USER, KBUILD_BUILD_HOST +------------------------------------ +These two variables allow to override the user@host string displayed during +boot and in /proc/version. The default value is the output of the commands +whoami and host, respectively. + +KBUILD_LDS +---------- +The linker script with full path. Assigned by the top-level Makefile. + +KBUILD_VMLINUX_OBJS +------------------- +All object files for vmlinux. They are linked to vmlinux in the same +order as listed in KBUILD_VMLINUX_OBJS. + +KBUILD_VMLINUX_LIBS +------------------- +All .a "lib" files for vmlinux. KBUILD_VMLINUX_OBJS and KBUILD_VMLINUX_LIBS +together specify all the object files used to link vmlinux. diff --git a/Documentation/kbuild/kbuild.txt b/Documentation/kbuild/kbuild.txt deleted file mode 100644 index 9c230ea71963..000000000000 --- a/Documentation/kbuild/kbuild.txt +++ /dev/null @@ -1,248 +0,0 @@ -Output files - -modules.order --------------------------------------------------- -This file records the order in which modules appear in Makefiles. This -is used by modprobe to deterministically resolve aliases that match -multiple modules. - -modules.builtin --------------------------------------------------- -This file lists all modules that are built into the kernel. This is used -by modprobe to not fail when trying to load something builtin. - -modules.builtin.modinfo --------------------------------------------------- -This file contains modinfo from all modules that are built into the kernel. -Unlike modinfo of a separate module, all fields are prefixed with module name. - - -Environment variables - -KCPPFLAGS --------------------------------------------------- -Additional options to pass when preprocessing. The preprocessing options -will be used in all cases where kbuild does preprocessing including -building C files and assembler files. - -KAFLAGS --------------------------------------------------- -Additional options to the assembler (for built-in and modules). - -AFLAGS_MODULE --------------------------------------------------- -Additional module specific options to use for $(AS). - -AFLAGS_KERNEL --------------------------------------------------- -Additional options for $(AS) when used for assembler -code for code that is compiled as built-in. - -KCFLAGS --------------------------------------------------- -Additional options to the C compiler (for built-in and modules). - -CFLAGS_KERNEL --------------------------------------------------- -Additional options for $(CC) when used to compile -code that is compiled as built-in. - -CFLAGS_MODULE --------------------------------------------------- -Additional module specific options to use for $(CC). - -LDFLAGS_MODULE --------------------------------------------------- -Additional options used for $(LD) when linking modules. - -HOSTCFLAGS --------------------------------------------------- -Additional flags to be passed to $(HOSTCC) when building host programs. - -HOSTCXXFLAGS --------------------------------------------------- -Additional flags to be passed to $(HOSTCXX) when building host programs. - -HOSTLDFLAGS --------------------------------------------------- -Additional flags to be passed when linking host programs. - -HOSTLDLIBS --------------------------------------------------- -Additional libraries to link against when building host programs. - -KBUILD_KCONFIG --------------------------------------------------- -Set the top-level Kconfig file to the value of this environment -variable. The default name is "Kconfig". - -KBUILD_VERBOSE --------------------------------------------------- -Set the kbuild verbosity. Can be assigned same values as "V=...". -See make help for the full list. -Setting "V=..." takes precedence over KBUILD_VERBOSE. - -KBUILD_EXTMOD --------------------------------------------------- -Set the directory to look for the kernel source when building external -modules. -Setting "M=..." takes precedence over KBUILD_EXTMOD. - -KBUILD_OUTPUT --------------------------------------------------- -Specify the output directory when building the kernel. -The output directory can also be specified using "O=...". -Setting "O=..." takes precedence over KBUILD_OUTPUT. - -KBUILD_DEBARCH --------------------------------------------------- -For the deb-pkg target, allows overriding the normal heuristics deployed by -deb-pkg. Normally deb-pkg attempts to guess the right architecture based on -the UTS_MACHINE variable, and on some architectures also the kernel config. -The value of KBUILD_DEBARCH is assumed (not checked) to be a valid Debian -architecture. - -ARCH --------------------------------------------------- -Set ARCH to the architecture to be built. -In most cases the name of the architecture is the same as the -directory name found in the arch/ directory. -But some architectures such as x86 and sparc have aliases. -x86: i386 for 32 bit, x86_64 for 64 bit -sh: sh for 32 bit, sh64 for 64 bit -sparc: sparc32 for 32 bit, sparc64 for 64 bit - -CROSS_COMPILE --------------------------------------------------- -Specify an optional fixed part of the binutils filename. -CROSS_COMPILE can be a part of the filename or the full path. - -CROSS_COMPILE is also used for ccache in some setups. - -CF --------------------------------------------------- -Additional options for sparse. -CF is often used on the command-line like this: - - make CF=-Wbitwise C=2 - -INSTALL_PATH --------------------------------------------------- -INSTALL_PATH specifies where to place the updated kernel and system map -images. Default is /boot, but you can set it to other values. - -INSTALLKERNEL --------------------------------------------------- -Install script called when using "make install". -The default name is "installkernel". - -The script will be called with the following arguments: - $1 - kernel version - $2 - kernel image file - $3 - kernel map file - $4 - default install path (use root directory if blank) - -The implementation of "make install" is architecture specific -and it may differ from the above. - -INSTALLKERNEL is provided to enable the possibility to -specify a custom installer when cross compiling a kernel. - -MODLIB --------------------------------------------------- -Specify where to install modules. -The default value is: - - $(INSTALL_MOD_PATH)/lib/modules/$(KERNELRELEASE) - -The value can be overridden in which case the default value is ignored. - -INSTALL_MOD_PATH --------------------------------------------------- -INSTALL_MOD_PATH specifies a prefix to MODLIB for module directory -relocations required by build roots. This is not defined in the -makefile but the argument can be passed to make if needed. - -INSTALL_MOD_STRIP --------------------------------------------------- -INSTALL_MOD_STRIP, if defined, will cause modules to be -stripped after they are installed. If INSTALL_MOD_STRIP is '1', then -the default option --strip-debug will be used. Otherwise, -INSTALL_MOD_STRIP value will be used as the options to the strip command. - -INSTALL_HDR_PATH --------------------------------------------------- -INSTALL_HDR_PATH specifies where to install user space headers when -executing "make headers_*". -The default value is: - - $(objtree)/usr - -$(objtree) is the directory where output files are saved. -The output directory is often set using "O=..." on the commandline. - -The value can be overridden in which case the default value is ignored. - -KBUILD_SIGN_PIN --------------------------------------------------- -This variable allows a passphrase or PIN to be passed to the sign-file -utility when signing kernel modules, if the private key requires such. - -KBUILD_MODPOST_WARN --------------------------------------------------- -KBUILD_MODPOST_WARN can be set to avoid errors in case of undefined -symbols in the final module linking stage. It changes such errors -into warnings. - -KBUILD_MODPOST_NOFINAL --------------------------------------------------- -KBUILD_MODPOST_NOFINAL can be set to skip the final link of modules. -This is solely useful to speed up test compiles. - -KBUILD_EXTRA_SYMBOLS --------------------------------------------------- -For modules that use symbols from other modules. -See more details in modules.txt. - -ALLSOURCE_ARCHS --------------------------------------------------- -For tags/TAGS/cscope targets, you can specify more than one arch -to be included in the databases, separated by blank space. E.g.: - - $ make ALLSOURCE_ARCHS="x86 mips arm" tags - -To get all available archs you can also specify all. E.g.: - - $ make ALLSOURCE_ARCHS=all tags - -KBUILD_ENABLE_EXTRA_GCC_CHECKS --------------------------------------------------- -If enabled over the make command line with "W=1", it turns on additional -gcc -W... options for more extensive build-time checking. - -KBUILD_BUILD_TIMESTAMP --------------------------------------------------- -Setting this to a date string overrides the timestamp used in the -UTS_VERSION definition (uname -v in the running kernel). The value has to -be a string that can be passed to date -d. The default value -is the output of the date command at one point during build. - -KBUILD_BUILD_USER, KBUILD_BUILD_HOST --------------------------------------------------- -These two variables allow to override the user@host string displayed during -boot and in /proc/version. The default value is the output of the commands -whoami and host, respectively. - -KBUILD_LDS --------------------------------------------------- -The linker script with full path. Assigned by the top-level Makefile. - -KBUILD_VMLINUX_OBJS --------------------------------------------------- -All object files for vmlinux. They are linked to vmlinux in the same -order as listed in KBUILD_VMLINUX_OBJS. - -KBUILD_VMLINUX_LIBS --------------------------------------------------- -All .a "lib" files for vmlinux. KBUILD_VMLINUX_OBJS and KBUILD_VMLINUX_LIBS -together specify all the object files used to link vmlinux. diff --git a/Documentation/kbuild/kconfig-language.rst b/Documentation/kbuild/kconfig-language.rst new file mode 100644 index 000000000000..2bc8a7803365 --- /dev/null +++ b/Documentation/kbuild/kconfig-language.rst @@ -0,0 +1,689 @@ +================ +Kconfig Language +================ + +Introduction +------------ + +The configuration database is a collection of configuration options +organized in a tree structure:: + + +- Code maturity level options + | +- Prompt for development and/or incomplete code/drivers + +- General setup + | +- Networking support + | +- System V IPC + | +- BSD Process Accounting + | +- Sysctl support + +- Loadable module support + | +- Enable loadable module support + | +- Set version information on all module symbols + | +- Kernel module loader + +- ... + +Every entry has its own dependencies. These dependencies are used +to determine the visibility of an entry. Any child entry is only +visible if its parent entry is also visible. + +Menu entries +------------ + +Most entries define a config option; all other entries help to organize +them. A single configuration option is defined like this:: + + config MODVERSIONS + bool "Set version information on all module symbols" + depends on MODULES + help + Usually, modules have to be recompiled whenever you switch to a new + kernel. ... + +Every line starts with a key word and can be followed by multiple +arguments. "config" starts a new config entry. The following lines +define attributes for this config option. Attributes can be the type of +the config option, input prompt, dependencies, help text and default +values. A config option can be defined multiple times with the same +name, but every definition can have only a single input prompt and the +type must not conflict. + +Menu attributes +--------------- + +A menu entry can have a number of attributes. Not all of them are +applicable everywhere (see syntax). + +- type definition: "bool"/"tristate"/"string"/"hex"/"int" + Every config option must have a type. There are only two basic types: + tristate and string; the other types are based on these two. The type + definition optionally accepts an input prompt, so these two examples + are equivalent:: + + bool "Networking support" + + and:: + + bool + prompt "Networking support" + +- input prompt: "prompt" ["if" ] + Every menu entry can have at most one prompt, which is used to display + to the user. Optionally dependencies only for this prompt can be added + with "if". + +- default value: "default" ["if" ] + A config option can have any number of default values. If multiple + default values are visible, only the first defined one is active. + Default values are not limited to the menu entry where they are + defined. This means the default can be defined somewhere else or be + overridden by an earlier definition. + The default value is only assigned to the config symbol if no other + value was set by the user (via the input prompt above). If an input + prompt is visible the default value is presented to the user and can + be overridden by him. + Optionally, dependencies only for this default value can be added with + "if". + + The default value deliberately defaults to 'n' in order to avoid bloating the + build. With few exceptions, new config options should not change this. The + intent is for "make oldconfig" to add as little as possible to the config from + release to release. + + Note: + Things that merit "default y/m" include: + + a) A new Kconfig option for something that used to always be built + should be "default y". + + b) A new gatekeeping Kconfig option that hides/shows other Kconfig + options (but does not generate any code of its own), should be + "default y" so people will see those other options. + + c) Sub-driver behavior or similar options for a driver that is + "default n". This allows you to provide sane defaults. + + d) Hardware or infrastructure that everybody expects, such as CONFIG_NET + or CONFIG_BLOCK. These are rare exceptions. + +- type definition + default value:: + + "def_bool"/"def_tristate" ["if" ] + + This is a shorthand notation for a type definition plus a value. + Optionally dependencies for this default value can be added with "if". + +- dependencies: "depends on" + This defines a dependency for this menu entry. If multiple + dependencies are defined, they are connected with '&&'. Dependencies + are applied to all other options within this menu entry (which also + accept an "if" expression), so these two examples are equivalent:: + + bool "foo" if BAR + default y if BAR + + and:: + + depends on BAR + bool "foo" + default y + +- reverse dependencies: "select" ["if" ] + While normal dependencies reduce the upper limit of a symbol (see + below), reverse dependencies can be used to force a lower limit of + another symbol. The value of the current menu symbol is used as the + minimal value can be set to. If is selected multiple + times, the limit is set to the largest selection. + Reverse dependencies can only be used with boolean or tristate + symbols. + + Note: + select should be used with care. select will force + a symbol to a value without visiting the dependencies. + By abusing select you are able to select a symbol FOO even + if FOO depends on BAR that is not set. + In general use select only for non-visible symbols + (no prompts anywhere) and for symbols with no dependencies. + That will limit the usefulness but on the other hand avoid + the illegal configurations all over. + +- weak reverse dependencies: "imply" ["if" ] + This is similar to "select" as it enforces a lower limit on another + symbol except that the "implied" symbol's value may still be set to n + from a direct dependency or with a visible prompt. + + Given the following example:: + + config FOO + tristate + imply BAZ + + config BAZ + tristate + depends on BAR + + The following values are possible: + + === === ============= ============== + FOO BAR BAZ's default choice for BAZ + === === ============= ============== + n y n N/m/y + m y m M/y/n + y y y Y/n + y n * N + === === ============= ============== + + This is useful e.g. with multiple drivers that want to indicate their + ability to hook into a secondary subsystem while allowing the user to + configure that subsystem out without also having to unset these drivers. + +- limiting menu display: "visible if" + This attribute is only applicable to menu blocks, if the condition is + false, the menu block is not displayed to the user (the symbols + contained there can still be selected by other symbols, though). It is + similar to a conditional "prompt" attribute for individual menu + entries. Default value of "visible" is true. + +- numerical ranges: "range" ["if" ] + This allows to limit the range of possible input values for int + and hex symbols. The user can only input a value which is larger than + or equal to the first symbol and smaller than or equal to the second + symbol. + +- help text: "help" or "---help---" + This defines a help text. The end of the help text is determined by + the indentation level, this means it ends at the first line which has + a smaller indentation than the first line of the help text. + "---help---" and "help" do not differ in behaviour, "---help---" is + used to help visually separate configuration logic from help within + the file as an aid to developers. + +- misc options: "option" [=] + Various less common options can be defined via this option syntax, + which can modify the behaviour of the menu entry and its config + symbol. These options are currently possible: + + - "defconfig_list" + This declares a list of default entries which can be used when + looking for the default configuration (which is used when the main + .config doesn't exists yet.) + + - "modules" + This declares the symbol to be used as the MODULES symbol, which + enables the third modular state for all config symbols. + At most one symbol may have the "modules" option set. + + - "allnoconfig_y" + This declares the symbol as one that should have the value y when + using "allnoconfig". Used for symbols that hide other symbols. + +Menu dependencies +----------------- + +Dependencies define the visibility of a menu entry and can also reduce +the input range of tristate symbols. The tristate logic used in the +expressions uses one more state than normal boolean logic to express the +module state. Dependency expressions have the following syntax:: + + ::= (1) + '=' (2) + '!=' (3) + '<' (4) + '>' (4) + '<=' (4) + '>=' (4) + '(' ')' (5) + '!' (6) + '&&' (7) + '||' (8) + +Expressions are listed in decreasing order of precedence. + +(1) Convert the symbol into an expression. Boolean and tristate symbols + are simply converted into the respective expression values. All + other symbol types result in 'n'. +(2) If the values of both symbols are equal, it returns 'y', + otherwise 'n'. +(3) If the values of both symbols are equal, it returns 'n', + otherwise 'y'. +(4) If value of is respectively lower, greater, lower-or-equal, + or greater-or-equal than value of , it returns 'y', + otherwise 'n'. +(5) Returns the value of the expression. Used to override precedence. +(6) Returns the result of (2-/expr/). +(7) Returns the result of min(/expr/, /expr/). +(8) Returns the result of max(/expr/, /expr/). + +An expression can have a value of 'n', 'm' or 'y' (or 0, 1, 2 +respectively for calculations). A menu entry becomes visible when its +expression evaluates to 'm' or 'y'. + +There are two types of symbols: constant and non-constant symbols. +Non-constant symbols are the most common ones and are defined with the +'config' statement. Non-constant symbols consist entirely of alphanumeric +characters or underscores. +Constant symbols are only part of expressions. Constant symbols are +always surrounded by single or double quotes. Within the quote, any +other character is allowed and the quotes can be escaped using '\'. + +Menu structure +-------------- + +The position of a menu entry in the tree is determined in two ways. First +it can be specified explicitly:: + + menu "Network device support" + depends on NET + + config NETDEVICES + ... + + endmenu + +All entries within the "menu" ... "endmenu" block become a submenu of +"Network device support". All subentries inherit the dependencies from +the menu entry, e.g. this means the dependency "NET" is added to the +dependency list of the config option NETDEVICES. + +The other way to generate the menu structure is done by analyzing the +dependencies. If a menu entry somehow depends on the previous entry, it +can be made a submenu of it. First, the previous (parent) symbol must +be part of the dependency list and then one of these two conditions +must be true: + +- the child entry must become invisible, if the parent is set to 'n' +- the child entry must only be visible, if the parent is visible:: + + config MODULES + bool "Enable loadable module support" + + config MODVERSIONS + bool "Set version information on all module symbols" + depends on MODULES + + comment "module support disabled" + depends on !MODULES + +MODVERSIONS directly depends on MODULES, this means it's only visible if +MODULES is different from 'n'. The comment on the other hand is only +visible when MODULES is set to 'n'. + + +Kconfig syntax +-------------- + +The configuration file describes a series of menu entries, where every +line starts with a keyword (except help texts). The following keywords +end a menu entry: + +- config +- menuconfig +- choice/endchoice +- comment +- menu/endmenu +- if/endif +- source + +The first five also start the definition of a menu entry. + +config:: + "config" + + +This defines a config symbol and accepts any of above +attributes as options. + +menuconfig:: + "menuconfig" + + +This is similar to the simple config entry above, but it also gives a +hint to front ends, that all suboptions should be displayed as a +separate list of options. To make sure all the suboptions will really +show up under the menuconfig entry and not outside of it, every item +from the list must depend on the menuconfig symbol. +In practice, this is achieved by using one of the next two constructs:: + + (1): + menuconfig M + if M + config C1 + config C2 + endif + + (2): + menuconfig M + config C1 + depends on M + config C2 + depends on M + +In the following examples (3) and (4), C1 and C2 still have the M +dependency, but will not appear under menuconfig M anymore, because +of C0, which doesn't depend on M:: + + (3): + menuconfig M + config C0 + if M + config C1 + config C2 + endif + + (4): + menuconfig M + config C0 + config C1 + depends on M + config C2 + depends on M + +choices:: + + "choice" [symbol] + + + "endchoice" + +This defines a choice group and accepts any of the above attributes as +options. A choice can only be of type bool or tristate. If no type is +specified for a choice, its type will be determined by the type of +the first choice element in the group or remain unknown if none of the +choice elements have a type specified, as well. + +While a boolean choice only allows a single config entry to be +selected, a tristate choice also allows any number of config entries +to be set to 'm'. This can be used if multiple drivers for a single +hardware exists and only a single driver can be compiled/loaded into +the kernel, but all drivers can be compiled as modules. + +A choice accepts another option "optional", which allows to set the +choice to 'n' and no entry needs to be selected. +If no [symbol] is associated with a choice, then you can not have multiple +definitions of that choice. If a [symbol] is associated to the choice, +then you may define the same choice (i.e. with the same entries) in another +place. + +comment:: + + "comment" + + +This defines a comment which is displayed to the user during the +configuration process and is also echoed to the output files. The only +possible options are dependencies. + +menu:: + + "menu" + + + "endmenu" + +This defines a menu block, see "Menu structure" above for more +information. The only possible options are dependencies and "visible" +attributes. + +if:: + + "if" + + "endif" + +This defines an if block. The dependency expression is appended +to all enclosed menu entries. + +source:: + + "source" + +This reads the specified configuration file. This file is always parsed. + +mainmenu:: + + "mainmenu" + +This sets the config program's title bar if the config program chooses +to use it. It should be placed at the top of the configuration, before any +other statement. + +'#' Kconfig source file comment: + +An unquoted '#' character anywhere in a source file line indicates +the beginning of a source file comment. The remainder of that line +is a comment. + + +Kconfig hints +------------- +This is a collection of Kconfig tips, most of which aren't obvious at +first glance and most of which have become idioms in several Kconfig +files. + +Adding common features and make the usage configurable +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +It is a common idiom to implement a feature/functionality that are +relevant for some architectures but not all. +The recommended way to do so is to use a config variable named HAVE_* +that is defined in a common Kconfig file and selected by the relevant +architectures. +An example is the generic IOMAP functionality. + +We would in lib/Kconfig see:: + + # Generic IOMAP is used to ... + config HAVE_GENERIC_IOMAP + + config GENERIC_IOMAP + depends on HAVE_GENERIC_IOMAP && FOO + +And in lib/Makefile we would see:: + + obj-$(CONFIG_GENERIC_IOMAP) += iomap.o + +For each architecture using the generic IOMAP functionality we would see:: + + config X86 + select ... + select HAVE_GENERIC_IOMAP + select ... + +Note: we use the existing config option and avoid creating a new +config variable to select HAVE_GENERIC_IOMAP. + +Note: the use of the internal config variable HAVE_GENERIC_IOMAP, it is +introduced to overcome the limitation of select which will force a +config option to 'y' no matter the dependencies. +The dependencies are moved to the symbol GENERIC_IOMAP and we avoid the +situation where select forces a symbol equals to 'y'. + +Adding features that need compiler support +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +There are several features that need compiler support. The recommended way +to describe the dependency on the compiler feature is to use "depends on" +followed by a test macro:: + + config STACKPROTECTOR + bool "Stack Protector buffer overflow detection" + depends on $(cc-option,-fstack-protector) + ... + +If you need to expose a compiler capability to makefiles and/or C source files, +`CC_HAS_` is the recommended prefix for the config option:: + + config CC_HAS_STACKPROTECTOR_NONE + def_bool $(cc-option,-fno-stack-protector) + +Build as module only +~~~~~~~~~~~~~~~~~~~~ +To restrict a component build to module-only, qualify its config symbol +with "depends on m". E.g.:: + + config FOO + depends on BAR && m + +limits FOO to module (=m) or disabled (=n). + +Kconfig recursive dependency limitations +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +If you've hit the Kconfig error: "recursive dependency detected" you've run +into a recursive dependency issue with Kconfig, a recursive dependency can be +summarized as a circular dependency. The kconfig tools need to ensure that +Kconfig files comply with specified configuration requirements. In order to do +that kconfig must determine the values that are possible for all Kconfig +symbols, this is currently not possible if there is a circular relation +between two or more Kconfig symbols. For more details refer to the "Simple +Kconfig recursive issue" subsection below. Kconfig does not do recursive +dependency resolution; this has a few implications for Kconfig file writers. +We'll first explain why this issues exists and then provide an example +technical limitation which this brings upon Kconfig developers. Eager +developers wishing to try to address this limitation should read the next +subsections. + +Simple Kconfig recursive issue +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Read: Documentation/kbuild/Kconfig.recursion-issue-01 + +Test with:: + + make KBUILD_KCONFIG=Documentation/kbuild/Kconfig.recursion-issue-01 allnoconfig + +Cumulative Kconfig recursive issue +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Read: Documentation/kbuild/Kconfig.recursion-issue-02 + +Test with:: + + make KBUILD_KCONFIG=Documentation/kbuild/Kconfig.recursion-issue-02 allnoconfig + +Practical solutions to kconfig recursive issue +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Developers who run into the recursive Kconfig issue have two options +at their disposal. We document them below and also provide a list of +historical issues resolved through these different solutions. + + a) Remove any superfluous "select FOO" or "depends on FOO" + b) Match dependency semantics: + + b1) Swap all "select FOO" to "depends on FOO" or, + + b2) Swap all "depends on FOO" to "select FOO" + +The resolution to a) can be tested with the sample Kconfig file +Documentation/kbuild/Kconfig.recursion-issue-01 through the removal +of the "select CORE" from CORE_BELL_A_ADVANCED as that is implicit already +since CORE_BELL_A depends on CORE. At times it may not be possible to remove +some dependency criteria, for such cases you can work with solution b). + +The two different resolutions for b) can be tested in the sample Kconfig file +Documentation/kbuild/Kconfig.recursion-issue-02. + +Below is a list of examples of prior fixes for these types of recursive issues; +all errors appear to involve one or more select's and one or more "depends on". + +============ =================================== +commit fix +============ =================================== +06b718c01208 select A -> depends on A +c22eacfe82f9 depends on A -> depends on B +6a91e854442c select A -> depends on A +118c565a8f2e select A -> select B +f004e5594705 select A -> depends on A +c7861f37b4c6 depends on A -> (null) +80c69915e5fb select A -> (null) (1) +c2218e26c0d0 select A -> depends on A (1) +d6ae99d04e1c select A -> depends on A +95ca19cf8cbf select A -> depends on A +8f057d7bca54 depends on A -> (null) +8f057d7bca54 depends on A -> select A +a0701f04846e select A -> depends on A +0c8b92f7f259 depends on A -> (null) +e4e9e0540928 select A -> depends on A (2) +7453ea886e87 depends on A > (null) (1) +7b1fff7e4fdf select A -> depends on A +86c747d2a4f0 select A -> depends on A +d9f9ab51e55e select A -> depends on A +0c51a4d8abd6 depends on A -> select A (3) +e98062ed6dc4 select A -> depends on A (3) +91e5d284a7f1 select A -> (null) +============ =================================== + +(1) Partial (or no) quote of error. +(2) That seems to be the gist of that fix. +(3) Same error. + +Future kconfig work +~~~~~~~~~~~~~~~~~~~ + +Work on kconfig is welcomed on both areas of clarifying semantics and on +evaluating the use of a full SAT solver for it. A full SAT solver can be +desirable to enable more complex dependency mappings and / or queries, +for instance on possible use case for a SAT solver could be that of handling +the current known recursive dependency issues. It is not known if this would +address such issues but such evaluation is desirable. If support for a full SAT +solver proves too complex or that it cannot address recursive dependency issues +Kconfig should have at least clear and well defined semantics which also +addresses and documents limitations or requirements such as the ones dealing +with recursive dependencies. + +Further work on both of these areas is welcomed on Kconfig. We elaborate +on both of these in the next two subsections. + +Semantics of Kconfig +~~~~~~~~~~~~~~~~~~~~ + +The use of Kconfig is broad, Linux is now only one of Kconfig's users: +one study has completed a broad analysis of Kconfig use in 12 projects [0]_. +Despite its widespread use, and although this document does a reasonable job +in documenting basic Kconfig syntax a more precise definition of Kconfig +semantics is welcomed. One project deduced Kconfig semantics through +the use of the xconfig configurator [1]_. Work should be done to confirm if +the deduced semantics matches our intended Kconfig design goals. + +Having well defined semantics can be useful for tools for practical +evaluation of depenencies, for instance one such use known case was work to +express in boolean abstraction of the inferred semantics of Kconfig to +translate Kconfig logic into boolean formulas and run a SAT solver on this to +find dead code / features (always inactive), 114 dead features were found in +Linux using this methodology [1]_ (Section 8: Threats to validity). + +Confirming this could prove useful as Kconfig stands as one of the the leading +industrial variability modeling languages [1]_ [2]_. Its study would help +evaluate practical uses of such languages, their use was only theoretical +and real world requirements were not well understood. As it stands though +only reverse engineering techniques have been used to deduce semantics from +variability modeling languages such as Kconfig [3]_. + +.. [0] http://www.eng.uwaterloo.ca/~shshe/kconfig_semantics.pdf +.. [1] http://gsd.uwaterloo.ca/sites/default/files/vm-2013-berger.pdf +.. [2] http://gsd.uwaterloo.ca/sites/default/files/ase241-berger_0.pdf +.. [3] http://gsd.uwaterloo.ca/sites/default/files/icse2011.pdf + +Full SAT solver for Kconfig +~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Although SAT solvers [4]_ haven't yet been used by Kconfig directly, as noted +in the previous subsection, work has been done however to express in boolean +abstraction the inferred semantics of Kconfig to translate Kconfig logic into +boolean formulas and run a SAT solver on it [5]_. Another known related project +is CADOS [6]_ (former VAMOS [7]_) and the tools, mainly undertaker [8]_, which +has been introduced first with [9]_. The basic concept of undertaker is to +exract variability models from Kconfig, and put them together with a +propositional formula extracted from CPP #ifdefs and build-rules into a SAT +solver in order to find dead code, dead files, and dead symbols. If using a SAT +solver is desirable on Kconfig one approach would be to evaluate repurposing +such efforts somehow on Kconfig. There is enough interest from mentors of +existing projects to not only help advise how to integrate this work upstream +but also help maintain it long term. Interested developers should visit: + +http://kernelnewbies.org/KernelProjects/kconfig-sat + +.. [4] http://www.cs.cornell.edu/~sabhar/chapters/SATSolvers-KR-Handbook.pdf +.. [5] http://gsd.uwaterloo.ca/sites/default/files/vm-2013-berger.pdf +.. [6] https://cados.cs.fau.de +.. [7] https://vamos.cs.fau.de +.. [8] https://undertaker.cs.fau.de +.. [9] https://www4.cs.fau.de/Publications/2011/tartler_11_eurosys.pdf diff --git a/Documentation/kbuild/kconfig-language.txt b/Documentation/kbuild/kconfig-language.txt deleted file mode 100644 index 864e740811da..000000000000 --- a/Documentation/kbuild/kconfig-language.txt +++ /dev/null @@ -1,669 +0,0 @@ -Introduction ------------- - -The configuration database is a collection of configuration options -organized in a tree structure: - - +- Code maturity level options - | +- Prompt for development and/or incomplete code/drivers - +- General setup - | +- Networking support - | +- System V IPC - | +- BSD Process Accounting - | +- Sysctl support - +- Loadable module support - | +- Enable loadable module support - | +- Set version information on all module symbols - | +- Kernel module loader - +- ... - -Every entry has its own dependencies. These dependencies are used -to determine the visibility of an entry. Any child entry is only -visible if its parent entry is also visible. - -Menu entries ------------- - -Most entries define a config option; all other entries help to organize -them. A single configuration option is defined like this: - -config MODVERSIONS - bool "Set version information on all module symbols" - depends on MODULES - help - Usually, modules have to be recompiled whenever you switch to a new - kernel. ... - -Every line starts with a key word and can be followed by multiple -arguments. "config" starts a new config entry. The following lines -define attributes for this config option. Attributes can be the type of -the config option, input prompt, dependencies, help text and default -values. A config option can be defined multiple times with the same -name, but every definition can have only a single input prompt and the -type must not conflict. - -Menu attributes ---------------- - -A menu entry can have a number of attributes. Not all of them are -applicable everywhere (see syntax). - -- type definition: "bool"/"tristate"/"string"/"hex"/"int" - Every config option must have a type. There are only two basic types: - tristate and string; the other types are based on these two. The type - definition optionally accepts an input prompt, so these two examples - are equivalent: - - bool "Networking support" - and - bool - prompt "Networking support" - -- input prompt: "prompt" ["if" ] - Every menu entry can have at most one prompt, which is used to display - to the user. Optionally dependencies only for this prompt can be added - with "if". - -- default value: "default" ["if" ] - A config option can have any number of default values. If multiple - default values are visible, only the first defined one is active. - Default values are not limited to the menu entry where they are - defined. This means the default can be defined somewhere else or be - overridden by an earlier definition. - The default value is only assigned to the config symbol if no other - value was set by the user (via the input prompt above). If an input - prompt is visible the default value is presented to the user and can - be overridden by him. - Optionally, dependencies only for this default value can be added with - "if". - - The default value deliberately defaults to 'n' in order to avoid bloating the - build. With few exceptions, new config options should not change this. The - intent is for "make oldconfig" to add as little as possible to the config from - release to release. - - Note: - Things that merit "default y/m" include: - - a) A new Kconfig option for something that used to always be built - should be "default y". - - b) A new gatekeeping Kconfig option that hides/shows other Kconfig - options (but does not generate any code of its own), should be - "default y" so people will see those other options. - - c) Sub-driver behavior or similar options for a driver that is - "default n". This allows you to provide sane defaults. - - d) Hardware or infrastructure that everybody expects, such as CONFIG_NET - or CONFIG_BLOCK. These are rare exceptions. - -- type definition + default value: - "def_bool"/"def_tristate" ["if" ] - This is a shorthand notation for a type definition plus a value. - Optionally dependencies for this default value can be added with "if". - -- dependencies: "depends on" - This defines a dependency for this menu entry. If multiple - dependencies are defined, they are connected with '&&'. Dependencies - are applied to all other options within this menu entry (which also - accept an "if" expression), so these two examples are equivalent: - - bool "foo" if BAR - default y if BAR - and - depends on BAR - bool "foo" - default y - -- reverse dependencies: "select" ["if" ] - While normal dependencies reduce the upper limit of a symbol (see - below), reverse dependencies can be used to force a lower limit of - another symbol. The value of the current menu symbol is used as the - minimal value can be set to. If is selected multiple - times, the limit is set to the largest selection. - Reverse dependencies can only be used with boolean or tristate - symbols. - Note: - select should be used with care. select will force - a symbol to a value without visiting the dependencies. - By abusing select you are able to select a symbol FOO even - if FOO depends on BAR that is not set. - In general use select only for non-visible symbols - (no prompts anywhere) and for symbols with no dependencies. - That will limit the usefulness but on the other hand avoid - the illegal configurations all over. - -- weak reverse dependencies: "imply" ["if" ] - This is similar to "select" as it enforces a lower limit on another - symbol except that the "implied" symbol's value may still be set to n - from a direct dependency or with a visible prompt. - - Given the following example: - - config FOO - tristate - imply BAZ - - config BAZ - tristate - depends on BAR - - The following values are possible: - - FOO BAR BAZ's default choice for BAZ - --- --- ------------- -------------- - n y n N/m/y - m y m M/y/n - y y y Y/n - y n * N - - This is useful e.g. with multiple drivers that want to indicate their - ability to hook into a secondary subsystem while allowing the user to - configure that subsystem out without also having to unset these drivers. - -- limiting menu display: "visible if" - This attribute is only applicable to menu blocks, if the condition is - false, the menu block is not displayed to the user (the symbols - contained there can still be selected by other symbols, though). It is - similar to a conditional "prompt" attribute for individual menu - entries. Default value of "visible" is true. - -- numerical ranges: "range" ["if" ] - This allows to limit the range of possible input values for int - and hex symbols. The user can only input a value which is larger than - or equal to the first symbol and smaller than or equal to the second - symbol. - -- help text: "help" or "---help---" - This defines a help text. The end of the help text is determined by - the indentation level, this means it ends at the first line which has - a smaller indentation than the first line of the help text. - "---help---" and "help" do not differ in behaviour, "---help---" is - used to help visually separate configuration logic from help within - the file as an aid to developers. - -- misc options: "option" [=] - Various less common options can be defined via this option syntax, - which can modify the behaviour of the menu entry and its config - symbol. These options are currently possible: - - - "defconfig_list" - This declares a list of default entries which can be used when - looking for the default configuration (which is used when the main - .config doesn't exists yet.) - - - "modules" - This declares the symbol to be used as the MODULES symbol, which - enables the third modular state for all config symbols. - At most one symbol may have the "modules" option set. - - - "allnoconfig_y" - This declares the symbol as one that should have the value y when - using "allnoconfig". Used for symbols that hide other symbols. - -Menu dependencies ------------------ - -Dependencies define the visibility of a menu entry and can also reduce -the input range of tristate symbols. The tristate logic used in the -expressions uses one more state than normal boolean logic to express the -module state. Dependency expressions have the following syntax: - - ::= (1) - '=' (2) - '!=' (3) - '<' (4) - '>' (4) - '<=' (4) - '>=' (4) - '(' ')' (5) - '!' (6) - '&&' (7) - '||' (8) - -Expressions are listed in decreasing order of precedence. - -(1) Convert the symbol into an expression. Boolean and tristate symbols - are simply converted into the respective expression values. All - other symbol types result in 'n'. -(2) If the values of both symbols are equal, it returns 'y', - otherwise 'n'. -(3) If the values of both symbols are equal, it returns 'n', - otherwise 'y'. -(4) If value of is respectively lower, greater, lower-or-equal, - or greater-or-equal than value of , it returns 'y', - otherwise 'n'. -(5) Returns the value of the expression. Used to override precedence. -(6) Returns the result of (2-/expr/). -(7) Returns the result of min(/expr/, /expr/). -(8) Returns the result of max(/expr/, /expr/). - -An expression can have a value of 'n', 'm' or 'y' (or 0, 1, 2 -respectively for calculations). A menu entry becomes visible when its -expression evaluates to 'm' or 'y'. - -There are two types of symbols: constant and non-constant symbols. -Non-constant symbols are the most common ones and are defined with the -'config' statement. Non-constant symbols consist entirely of alphanumeric -characters or underscores. -Constant symbols are only part of expressions. Constant symbols are -always surrounded by single or double quotes. Within the quote, any -other character is allowed and the quotes can be escaped using '\'. - -Menu structure --------------- - -The position of a menu entry in the tree is determined in two ways. First -it can be specified explicitly: - -menu "Network device support" - depends on NET - -config NETDEVICES - ... - -endmenu - -All entries within the "menu" ... "endmenu" block become a submenu of -"Network device support". All subentries inherit the dependencies from -the menu entry, e.g. this means the dependency "NET" is added to the -dependency list of the config option NETDEVICES. - -The other way to generate the menu structure is done by analyzing the -dependencies. If a menu entry somehow depends on the previous entry, it -can be made a submenu of it. First, the previous (parent) symbol must -be part of the dependency list and then one of these two conditions -must be true: -- the child entry must become invisible, if the parent is set to 'n' -- the child entry must only be visible, if the parent is visible - -config MODULES - bool "Enable loadable module support" - -config MODVERSIONS - bool "Set version information on all module symbols" - depends on MODULES - -comment "module support disabled" - depends on !MODULES - -MODVERSIONS directly depends on MODULES, this means it's only visible if -MODULES is different from 'n'. The comment on the other hand is only -visible when MODULES is set to 'n'. - - -Kconfig syntax --------------- - -The configuration file describes a series of menu entries, where every -line starts with a keyword (except help texts). The following keywords -end a menu entry: -- config -- menuconfig -- choice/endchoice -- comment -- menu/endmenu -- if/endif -- source -The first five also start the definition of a menu entry. - -config: - - "config" - - -This defines a config symbol and accepts any of above -attributes as options. - -menuconfig: - "menuconfig" - - -This is similar to the simple config entry above, but it also gives a -hint to front ends, that all suboptions should be displayed as a -separate list of options. To make sure all the suboptions will really -show up under the menuconfig entry and not outside of it, every item -from the list must depend on the menuconfig symbol. -In practice, this is achieved by using one of the next two constructs: - -(1): -menuconfig M -if M - config C1 - config C2 -endif - -(2): -menuconfig M -config C1 - depends on M -config C2 - depends on M - -In the following examples (3) and (4), C1 and C2 still have the M -dependency, but will not appear under menuconfig M anymore, because -of C0, which doesn't depend on M: - -(3): -menuconfig M - config C0 -if M - config C1 - config C2 -endif - -(4): -menuconfig M -config C0 -config C1 - depends on M -config C2 - depends on M - -choices: - - "choice" [symbol] - - - "endchoice" - -This defines a choice group and accepts any of the above attributes as -options. A choice can only be of type bool or tristate. If no type is -specified for a choice, its type will be determined by the type of -the first choice element in the group or remain unknown if none of the -choice elements have a type specified, as well. - -While a boolean choice only allows a single config entry to be -selected, a tristate choice also allows any number of config entries -to be set to 'm'. This can be used if multiple drivers for a single -hardware exists and only a single driver can be compiled/loaded into -the kernel, but all drivers can be compiled as modules. - -A choice accepts another option "optional", which allows to set the -choice to 'n' and no entry needs to be selected. -If no [symbol] is associated with a choice, then you can not have multiple -definitions of that choice. If a [symbol] is associated to the choice, -then you may define the same choice (i.e. with the same entries) in another -place. - -comment: - - "comment" - - -This defines a comment which is displayed to the user during the -configuration process and is also echoed to the output files. The only -possible options are dependencies. - -menu: - - "menu" - - - "endmenu" - -This defines a menu block, see "Menu structure" above for more -information. The only possible options are dependencies and "visible" -attributes. - -if: - - "if" - - "endif" - -This defines an if block. The dependency expression is appended -to all enclosed menu entries. - -source: - - "source" - -This reads the specified configuration file. This file is always parsed. - -mainmenu: - - "mainmenu" - -This sets the config program's title bar if the config program chooses -to use it. It should be placed at the top of the configuration, before any -other statement. - -'#' Kconfig source file comment: - -An unquoted '#' character anywhere in a source file line indicates -the beginning of a source file comment. The remainder of that line -is a comment. - - -Kconfig hints -------------- -This is a collection of Kconfig tips, most of which aren't obvious at -first glance and most of which have become idioms in several Kconfig -files. - -Adding common features and make the usage configurable -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -It is a common idiom to implement a feature/functionality that are -relevant for some architectures but not all. -The recommended way to do so is to use a config variable named HAVE_* -that is defined in a common Kconfig file and selected by the relevant -architectures. -An example is the generic IOMAP functionality. - -We would in lib/Kconfig see: - -# Generic IOMAP is used to ... -config HAVE_GENERIC_IOMAP - -config GENERIC_IOMAP - depends on HAVE_GENERIC_IOMAP && FOO - -And in lib/Makefile we would see: -obj-$(CONFIG_GENERIC_IOMAP) += iomap.o - -For each architecture using the generic IOMAP functionality we would see: - -config X86 - select ... - select HAVE_GENERIC_IOMAP - select ... - -Note: we use the existing config option and avoid creating a new -config variable to select HAVE_GENERIC_IOMAP. - -Note: the use of the internal config variable HAVE_GENERIC_IOMAP, it is -introduced to overcome the limitation of select which will force a -config option to 'y' no matter the dependencies. -The dependencies are moved to the symbol GENERIC_IOMAP and we avoid the -situation where select forces a symbol equals to 'y'. - -Adding features that need compiler support -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ - -There are several features that need compiler support. The recommended way -to describe the dependency on the compiler feature is to use "depends on" -followed by a test macro. - -config STACKPROTECTOR - bool "Stack Protector buffer overflow detection" - depends on $(cc-option,-fstack-protector) - ... - -If you need to expose a compiler capability to makefiles and/or C source files, -CC_HAS_ is the recommended prefix for the config option. - -config CC_HAS_STACKPROTECTOR_NONE - def_bool $(cc-option,-fno-stack-protector) - -Build as module only -~~~~~~~~~~~~~~~~~~~~ -To restrict a component build to module-only, qualify its config symbol -with "depends on m". E.g.: - -config FOO - depends on BAR && m - -limits FOO to module (=m) or disabled (=n). - -Kconfig recursive dependency limitations -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ - -If you've hit the Kconfig error: "recursive dependency detected" you've run -into a recursive dependency issue with Kconfig, a recursive dependency can be -summarized as a circular dependency. The kconfig tools need to ensure that -Kconfig files comply with specified configuration requirements. In order to do -that kconfig must determine the values that are possible for all Kconfig -symbols, this is currently not possible if there is a circular relation -between two or more Kconfig symbols. For more details refer to the "Simple -Kconfig recursive issue" subsection below. Kconfig does not do recursive -dependency resolution; this has a few implications for Kconfig file writers. -We'll first explain why this issues exists and then provide an example -technical limitation which this brings upon Kconfig developers. Eager -developers wishing to try to address this limitation should read the next -subsections. - -Simple Kconfig recursive issue -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ - -Read: Documentation/kbuild/Kconfig.recursion-issue-01 - -Test with: - -make KBUILD_KCONFIG=Documentation/kbuild/Kconfig.recursion-issue-01 allnoconfig - -Cumulative Kconfig recursive issue -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ - -Read: Documentation/kbuild/Kconfig.recursion-issue-02 - -Test with: - -make KBUILD_KCONFIG=Documentation/kbuild/Kconfig.recursion-issue-02 allnoconfig - -Practical solutions to kconfig recursive issue -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ - -Developers who run into the recursive Kconfig issue have two options -at their disposal. We document them below and also provide a list of -historical issues resolved through these different solutions. - - a) Remove any superfluous "select FOO" or "depends on FOO" - b) Match dependency semantics: - b1) Swap all "select FOO" to "depends on FOO" or, - b2) Swap all "depends on FOO" to "select FOO" - -The resolution to a) can be tested with the sample Kconfig file -Documentation/kbuild/Kconfig.recursion-issue-01 through the removal -of the "select CORE" from CORE_BELL_A_ADVANCED as that is implicit already -since CORE_BELL_A depends on CORE. At times it may not be possible to remove -some dependency criteria, for such cases you can work with solution b). - -The two different resolutions for b) can be tested in the sample Kconfig file -Documentation/kbuild/Kconfig.recursion-issue-02. - -Below is a list of examples of prior fixes for these types of recursive issues; -all errors appear to involve one or more select's and one or more "depends on". - -commit fix -====== === -06b718c01208 select A -> depends on A -c22eacfe82f9 depends on A -> depends on B -6a91e854442c select A -> depends on A -118c565a8f2e select A -> select B -f004e5594705 select A -> depends on A -c7861f37b4c6 depends on A -> (null) -80c69915e5fb select A -> (null) (1) -c2218e26c0d0 select A -> depends on A (1) -d6ae99d04e1c select A -> depends on A -95ca19cf8cbf select A -> depends on A -8f057d7bca54 depends on A -> (null) -8f057d7bca54 depends on A -> select A -a0701f04846e select A -> depends on A -0c8b92f7f259 depends on A -> (null) -e4e9e0540928 select A -> depends on A (2) -7453ea886e87 depends on A > (null) (1) -7b1fff7e4fdf select A -> depends on A -86c747d2a4f0 select A -> depends on A -d9f9ab51e55e select A -> depends on A -0c51a4d8abd6 depends on A -> select A (3) -e98062ed6dc4 select A -> depends on A (3) -91e5d284a7f1 select A -> (null) - -(1) Partial (or no) quote of error. -(2) That seems to be the gist of that fix. -(3) Same error. - -Future kconfig work -~~~~~~~~~~~~~~~~~~~ - -Work on kconfig is welcomed on both areas of clarifying semantics and on -evaluating the use of a full SAT solver for it. A full SAT solver can be -desirable to enable more complex dependency mappings and / or queries, -for instance on possible use case for a SAT solver could be that of handling -the current known recursive dependency issues. It is not known if this would -address such issues but such evaluation is desirable. If support for a full SAT -solver proves too complex or that it cannot address recursive dependency issues -Kconfig should have at least clear and well defined semantics which also -addresses and documents limitations or requirements such as the ones dealing -with recursive dependencies. - -Further work on both of these areas is welcomed on Kconfig. We elaborate -on both of these in the next two subsections. - -Semantics of Kconfig -~~~~~~~~~~~~~~~~~~~~ - -The use of Kconfig is broad, Linux is now only one of Kconfig's users: -one study has completed a broad analysis of Kconfig use in 12 projects [0]. -Despite its widespread use, and although this document does a reasonable job -in documenting basic Kconfig syntax a more precise definition of Kconfig -semantics is welcomed. One project deduced Kconfig semantics through -the use of the xconfig configurator [1]. Work should be done to confirm if -the deduced semantics matches our intended Kconfig design goals. - -Having well defined semantics can be useful for tools for practical -evaluation of depenencies, for instance one such use known case was work to -express in boolean abstraction of the inferred semantics of Kconfig to -translate Kconfig logic into boolean formulas and run a SAT solver on this to -find dead code / features (always inactive), 114 dead features were found in -Linux using this methodology [1] (Section 8: Threats to validity). - -Confirming this could prove useful as Kconfig stands as one of the the leading -industrial variability modeling languages [1] [2]. Its study would help -evaluate practical uses of such languages, their use was only theoretical -and real world requirements were not well understood. As it stands though -only reverse engineering techniques have been used to deduce semantics from -variability modeling languages such as Kconfig [3]. - -[0] http://www.eng.uwaterloo.ca/~shshe/kconfig_semantics.pdf -[1] http://gsd.uwaterloo.ca/sites/default/files/vm-2013-berger.pdf -[2] http://gsd.uwaterloo.ca/sites/default/files/ase241-berger_0.pdf -[3] http://gsd.uwaterloo.ca/sites/default/files/icse2011.pdf - -Full SAT solver for Kconfig -~~~~~~~~~~~~~~~~~~~~~~~~~~~ - -Although SAT solvers [0] haven't yet been used by Kconfig directly, as noted in -the previous subsection, work has been done however to express in boolean -abstraction the inferred semantics of Kconfig to translate Kconfig logic into -boolean formulas and run a SAT solver on it [1]. Another known related project -is CADOS [2] (former VAMOS [3]) and the tools, mainly undertaker [4], which has -been introduced first with [5]. The basic concept of undertaker is to exract -variability models from Kconfig, and put them together with a propositional -formula extracted from CPP #ifdefs and build-rules into a SAT solver in order -to find dead code, dead files, and dead symbols. If using a SAT solver is -desirable on Kconfig one approach would be to evaluate repurposing such efforts -somehow on Kconfig. There is enough interest from mentors of existing projects -to not only help advise how to integrate this work upstream but also help -maintain it long term. Interested developers should visit: - -http://kernelnewbies.org/KernelProjects/kconfig-sat - -[0] http://www.cs.cornell.edu/~sabhar/chapters/SATSolvers-KR-Handbook.pdf -[1] http://gsd.uwaterloo.ca/sites/default/files/vm-2013-berger.pdf -[2] https://cados.cs.fau.de -[3] https://vamos.cs.fau.de -[4] https://undertaker.cs.fau.de -[5] https://www4.cs.fau.de/Publications/2011/tartler_11_eurosys.pdf diff --git a/Documentation/kbuild/kconfig-macro-language.rst b/Documentation/kbuild/kconfig-macro-language.rst new file mode 100644 index 000000000000..35b3263b7e40 --- /dev/null +++ b/Documentation/kbuild/kconfig-macro-language.rst @@ -0,0 +1,247 @@ +====================== +Kconfig macro language +====================== + +Concept +------- + +The basic idea was inspired by Make. When we look at Make, we notice sort of +two languages in one. One language describes dependency graphs consisting of +targets and prerequisites. The other is a macro language for performing textual +substitution. + +There is clear distinction between the two language stages. For example, you +can write a makefile like follows:: + + APP := foo + SRC := foo.c + CC := gcc + + $(APP): $(SRC) + $(CC) -o $(APP) $(SRC) + +The macro language replaces the variable references with their expanded form, +and handles as if the source file were input like follows:: + + foo: foo.c + gcc -o foo foo.c + +Then, Make analyzes the dependency graph and determines the targets to be +updated. + +The idea is quite similar in Kconfig - it is possible to describe a Kconfig +file like this:: + + CC := gcc + + config CC_HAS_FOO + def_bool $(shell, $(srctree)/scripts/gcc-check-foo.sh $(CC)) + +The macro language in Kconfig processes the source file into the following +intermediate:: + + config CC_HAS_FOO + def_bool y + +Then, Kconfig moves onto the evaluation stage to resolve inter-symbol +dependency as explained in kconfig-language.txt. + + +Variables +--------- + +Like in Make, a variable in Kconfig works as a macro variable. A macro +variable is expanded "in place" to yield a text string that may then be +expanded further. To get the value of a variable, enclose the variable name in +$( ). The parentheses are required even for single-letter variable names; $X is +a syntax error. The curly brace form as in ${CC} is not supported either. + +There are two types of variables: simply expanded variables and recursively +expanded variables. + +A simply expanded variable is defined using the := assignment operator. Its +righthand side is expanded immediately upon reading the line from the Kconfig +file. + +A recursively expanded variable is defined using the = assignment operator. +Its righthand side is simply stored as the value of the variable without +expanding it in any way. Instead, the expansion is performed when the variable +is used. + +There is another type of assignment operator; += is used to append text to a +variable. The righthand side of += is expanded immediately if the lefthand +side was originally defined as a simple variable. Otherwise, its evaluation is +deferred. + +The variable reference can take parameters, in the following form:: + + $(name,arg1,arg2,arg3) + +You can consider the parameterized reference as a function. (more precisely, +"user-defined function" in contrast to "built-in function" listed below). + +Useful functions must be expanded when they are used since the same function is +expanded differently if different parameters are passed. Hence, a user-defined +function is defined using the = assignment operator. The parameters are +referenced within the body definition with $(1), $(2), etc. + +In fact, recursively expanded variables and user-defined functions are the same +internally. (In other words, "variable" is "function with zero argument".) +When we say "variable" in a broad sense, it includes "user-defined function". + + +Built-in functions +------------------ + +Like Make, Kconfig provides several built-in functions. Every function takes a +particular number of arguments. + +In Make, every built-in function takes at least one argument. Kconfig allows +zero argument for built-in functions, such as $(fileno), $(lineno). You could +consider those as "built-in variable", but it is just a matter of how we call +it after all. Let's say "built-in function" here to refer to natively supported +functionality. + +Kconfig currently supports the following built-in functions. + + - $(shell,command) + + The "shell" function accepts a single argument that is expanded and passed + to a subshell for execution. The standard output of the command is then read + and returned as the value of the function. Every newline in the output is + replaced with a space. Any trailing newlines are deleted. The standard error + is not returned, nor is any program exit status. + + - $(info,text) + + The "info" function takes a single argument and prints it to stdout. + It evaluates to an empty string. + + - $(warning-if,condition,text) + + The "warning-if" function takes two arguments. If the condition part is "y", + the text part is sent to stderr. The text is prefixed with the name of the + current Kconfig file and the current line number. + + - $(error-if,condition,text) + + The "error-if" function is similar to "warning-if", but it terminates the + parsing immediately if the condition part is "y". + + - $(filename) + + The 'filename' takes no argument, and $(filename) is expanded to the file + name being parsed. + + - $(lineno) + + The 'lineno' takes no argument, and $(lineno) is expanded to the line number + being parsed. + + +Make vs Kconfig +--------------- + +Kconfig adopts Make-like macro language, but the function call syntax is +slightly different. + +A function call in Make looks like this:: + + $(func-name arg1,arg2,arg3) + +The function name and the first argument are separated by at least one +whitespace. Then, leading whitespaces are trimmed from the first argument, +while whitespaces in the other arguments are kept. You need to use a kind of +trick to start the first parameter with spaces. For example, if you want +to make "info" function print " hello", you can write like follows:: + + empty := + space := $(empty) $(empty) + $(info $(space)$(space)hello) + +Kconfig uses only commas for delimiters, and keeps all whitespaces in the +function call. Some people prefer putting a space after each comma delimiter:: + + $(func-name, arg1, arg2, arg3) + +In this case, "func-name" will receive " arg1", " arg2", " arg3". The presence +of leading spaces may matter depending on the function. The same applies to +Make - for example, $(subst .c, .o, $(sources)) is a typical mistake; it +replaces ".c" with " .o". + +In Make, a user-defined function is referenced by using a built-in function, +'call', like this:: + + $(call my-func,arg1,arg2,arg3) + +Kconfig invokes user-defined functions and built-in functions in the same way. +The omission of 'call' makes the syntax shorter. + +In Make, some functions treat commas verbatim instead of argument separators. +For example, $(shell echo hello, world) runs the command "echo hello, world". +Likewise, $(info hello, world) prints "hello, world" to stdout. You could say +this is _useful_ inconsistency. + +In Kconfig, for simpler implementation and grammatical consistency, commas that +appear in the $( ) context are always delimiters. It means:: + + $(shell, echo hello, world) + +is an error because it is passing two parameters where the 'shell' function +accepts only one. To pass commas in arguments, you can use the following trick:: + + comma := , + $(shell, echo hello$(comma) world) + + +Caveats +------- + +A variable (or function) cannot be expanded across tokens. So, you cannot use +a variable as a shorthand for an expression that consists of multiple tokens. +The following works:: + + RANGE_MIN := 1 + RANGE_MAX := 3 + + config FOO + int "foo" + range $(RANGE_MIN) $(RANGE_MAX) + +But, the following does not work:: + + RANGES := 1 3 + + config FOO + int "foo" + range $(RANGES) + +A variable cannot be expanded to any keyword in Kconfig. The following does +not work:: + + MY_TYPE := tristate + + config FOO + $(MY_TYPE) "foo" + default y + +Obviously from the design, $(shell command) is expanded in the textual +substitution phase. You cannot pass symbols to the 'shell' function. + +The following does not work as expected:: + + config ENDIAN_FLAG + string + default "-mbig-endian" if CPU_BIG_ENDIAN + default "-mlittle-endian" if CPU_LITTLE_ENDIAN + + config CC_HAS_ENDIAN_FLAG + def_bool $(shell $(srctree)/scripts/gcc-check-flag ENDIAN_FLAG) + +Instead, you can do like follows so that any function call is statically +expanded:: + + config CC_HAS_ENDIAN_FLAG + bool + default $(shell $(srctree)/scripts/gcc-check-flag -mbig-endian) if CPU_BIG_ENDIAN + default $(shell $(srctree)/scripts/gcc-check-flag -mlittle-endian) if CPU_LITTLE_ENDIAN diff --git a/Documentation/kbuild/kconfig-macro-language.txt b/Documentation/kbuild/kconfig-macro-language.txt deleted file mode 100644 index 07da2ea68dce..000000000000 --- a/Documentation/kbuild/kconfig-macro-language.txt +++ /dev/null @@ -1,242 +0,0 @@ -Concept -------- - -The basic idea was inspired by Make. When we look at Make, we notice sort of -two languages in one. One language describes dependency graphs consisting of -targets and prerequisites. The other is a macro language for performing textual -substitution. - -There is clear distinction between the two language stages. For example, you -can write a makefile like follows: - - APP := foo - SRC := foo.c - CC := gcc - - $(APP): $(SRC) - $(CC) -o $(APP) $(SRC) - -The macro language replaces the variable references with their expanded form, -and handles as if the source file were input like follows: - - foo: foo.c - gcc -o foo foo.c - -Then, Make analyzes the dependency graph and determines the targets to be -updated. - -The idea is quite similar in Kconfig - it is possible to describe a Kconfig -file like this: - - CC := gcc - - config CC_HAS_FOO - def_bool $(shell, $(srctree)/scripts/gcc-check-foo.sh $(CC)) - -The macro language in Kconfig processes the source file into the following -intermediate: - - config CC_HAS_FOO - def_bool y - -Then, Kconfig moves onto the evaluation stage to resolve inter-symbol -dependency as explained in kconfig-language.txt. - - -Variables ---------- - -Like in Make, a variable in Kconfig works as a macro variable. A macro -variable is expanded "in place" to yield a text string that may then be -expanded further. To get the value of a variable, enclose the variable name in -$( ). The parentheses are required even for single-letter variable names; $X is -a syntax error. The curly brace form as in ${CC} is not supported either. - -There are two types of variables: simply expanded variables and recursively -expanded variables. - -A simply expanded variable is defined using the := assignment operator. Its -righthand side is expanded immediately upon reading the line from the Kconfig -file. - -A recursively expanded variable is defined using the = assignment operator. -Its righthand side is simply stored as the value of the variable without -expanding it in any way. Instead, the expansion is performed when the variable -is used. - -There is another type of assignment operator; += is used to append text to a -variable. The righthand side of += is expanded immediately if the lefthand -side was originally defined as a simple variable. Otherwise, its evaluation is -deferred. - -The variable reference can take parameters, in the following form: - - $(name,arg1,arg2,arg3) - -You can consider the parameterized reference as a function. (more precisely, -"user-defined function" in contrast to "built-in function" listed below). - -Useful functions must be expanded when they are used since the same function is -expanded differently if different parameters are passed. Hence, a user-defined -function is defined using the = assignment operator. The parameters are -referenced within the body definition with $(1), $(2), etc. - -In fact, recursively expanded variables and user-defined functions are the same -internally. (In other words, "variable" is "function with zero argument".) -When we say "variable" in a broad sense, it includes "user-defined function". - - -Built-in functions ------------------- - -Like Make, Kconfig provides several built-in functions. Every function takes a -particular number of arguments. - -In Make, every built-in function takes at least one argument. Kconfig allows -zero argument for built-in functions, such as $(fileno), $(lineno). You could -consider those as "built-in variable", but it is just a matter of how we call -it after all. Let's say "built-in function" here to refer to natively supported -functionality. - -Kconfig currently supports the following built-in functions. - - - $(shell,command) - - The "shell" function accepts a single argument that is expanded and passed - to a subshell for execution. The standard output of the command is then read - and returned as the value of the function. Every newline in the output is - replaced with a space. Any trailing newlines are deleted. The standard error - is not returned, nor is any program exit status. - - - $(info,text) - - The "info" function takes a single argument and prints it to stdout. - It evaluates to an empty string. - - - $(warning-if,condition,text) - - The "warning-if" function takes two arguments. If the condition part is "y", - the text part is sent to stderr. The text is prefixed with the name of the - current Kconfig file and the current line number. - - - $(error-if,condition,text) - - The "error-if" function is similar to "warning-if", but it terminates the - parsing immediately if the condition part is "y". - - - $(filename) - - The 'filename' takes no argument, and $(filename) is expanded to the file - name being parsed. - - - $(lineno) - - The 'lineno' takes no argument, and $(lineno) is expanded to the line number - being parsed. - - -Make vs Kconfig ---------------- - -Kconfig adopts Make-like macro language, but the function call syntax is -slightly different. - -A function call in Make looks like this: - - $(func-name arg1,arg2,arg3) - -The function name and the first argument are separated by at least one -whitespace. Then, leading whitespaces are trimmed from the first argument, -while whitespaces in the other arguments are kept. You need to use a kind of -trick to start the first parameter with spaces. For example, if you want -to make "info" function print " hello", you can write like follows: - - empty := - space := $(empty) $(empty) - $(info $(space)$(space)hello) - -Kconfig uses only commas for delimiters, and keeps all whitespaces in the -function call. Some people prefer putting a space after each comma delimiter: - - $(func-name, arg1, arg2, arg3) - -In this case, "func-name" will receive " arg1", " arg2", " arg3". The presence -of leading spaces may matter depending on the function. The same applies to -Make - for example, $(subst .c, .o, $(sources)) is a typical mistake; it -replaces ".c" with " .o". - -In Make, a user-defined function is referenced by using a built-in function, -'call', like this: - - $(call my-func,arg1,arg2,arg3) - -Kconfig invokes user-defined functions and built-in functions in the same way. -The omission of 'call' makes the syntax shorter. - -In Make, some functions treat commas verbatim instead of argument separators. -For example, $(shell echo hello, world) runs the command "echo hello, world". -Likewise, $(info hello, world) prints "hello, world" to stdout. You could say -this is _useful_ inconsistency. - -In Kconfig, for simpler implementation and grammatical consistency, commas that -appear in the $( ) context are always delimiters. It means - - $(shell, echo hello, world) - -is an error because it is passing two parameters where the 'shell' function -accepts only one. To pass commas in arguments, you can use the following trick: - - comma := , - $(shell, echo hello$(comma) world) - - -Caveats -------- - -A variable (or function) cannot be expanded across tokens. So, you cannot use -a variable as a shorthand for an expression that consists of multiple tokens. -The following works: - - RANGE_MIN := 1 - RANGE_MAX := 3 - - config FOO - int "foo" - range $(RANGE_MIN) $(RANGE_MAX) - -But, the following does not work: - - RANGES := 1 3 - - config FOO - int "foo" - range $(RANGES) - -A variable cannot be expanded to any keyword in Kconfig. The following does -not work: - - MY_TYPE := tristate - - config FOO - $(MY_TYPE) "foo" - default y - -Obviously from the design, $(shell command) is expanded in the textual -substitution phase. You cannot pass symbols to the 'shell' function. -The following does not work as expected. - - config ENDIAN_FLAG - string - default "-mbig-endian" if CPU_BIG_ENDIAN - default "-mlittle-endian" if CPU_LITTLE_ENDIAN - - config CC_HAS_ENDIAN_FLAG - def_bool $(shell $(srctree)/scripts/gcc-check-flag ENDIAN_FLAG) - -Instead, you can do like follows so that any function call is statically -expanded. - - config CC_HAS_ENDIAN_FLAG - bool - default $(shell $(srctree)/scripts/gcc-check-flag -mbig-endian) if CPU_BIG_ENDIAN - default $(shell $(srctree)/scripts/gcc-check-flag -mlittle-endian) if CPU_LITTLE_ENDIAN diff --git a/Documentation/kbuild/kconfig.rst b/Documentation/kbuild/kconfig.rst new file mode 100644 index 000000000000..88129af7e539 --- /dev/null +++ b/Documentation/kbuild/kconfig.rst @@ -0,0 +1,300 @@ +=================== +Kconfig make config +=================== + +This file contains some assistance for using `make *config`. + +Use "make help" to list all of the possible configuration targets. + +The xconfig ('qconf'), menuconfig ('mconf'), and nconfig ('nconf') +programs also have embedded help text. Be sure to check that for +navigation, search, and other general help text. + +General +------- + +New kernel releases often introduce new config symbols. Often more +important, new kernel releases may rename config symbols. When +this happens, using a previously working .config file and running +"make oldconfig" won't necessarily produce a working new kernel +for you, so you may find that you need to see what NEW kernel +symbols have been introduced. + +To see a list of new config symbols, use:: + + cp user/some/old.config .config + make listnewconfig + +and the config program will list any new symbols, one per line. + +Alternatively, you can use the brute force method:: + + make oldconfig + scripts/diffconfig .config.old .config | less + +---------------------------------------------------------------------- + +Environment variables for `*config` + +KCONFIG_CONFIG +-------------- +This environment variable can be used to specify a default kernel config +file name to override the default name of ".config". + +KCONFIG_OVERWRITECONFIG +----------------------- +If you set KCONFIG_OVERWRITECONFIG in the environment, Kconfig will not +break symlinks when .config is a symlink to somewhere else. + +`CONFIG_` +--------- +If you set `CONFIG_` in the environment, Kconfig will prefix all symbols +with its value when saving the configuration, instead of using the default, +`CONFIG_`. + +---------------------------------------------------------------------- + +Environment variables for '{allyes/allmod/allno/rand}config' + +KCONFIG_ALLCONFIG +----------------- +(partially based on lkml email from/by Rob Landley, re: miniconfig) + +-------------------------------------------------- + +The allyesconfig/allmodconfig/allnoconfig/randconfig variants can also +use the environment variable KCONFIG_ALLCONFIG as a flag or a filename +that contains config symbols that the user requires to be set to a +specific value. If KCONFIG_ALLCONFIG is used without a filename where +KCONFIG_ALLCONFIG == "" or KCONFIG_ALLCONFIG == "1", `make *config` +checks for a file named "all{yes/mod/no/def/random}.config" +(corresponding to the `*config` command that was used) for symbol values +that are to be forced. If this file is not found, it checks for a +file named "all.config" to contain forced values. + +This enables you to create "miniature" config (miniconfig) or custom +config files containing just the config symbols that you are interested +in. Then the kernel config system generates the full .config file, +including symbols of your miniconfig file. + +This 'KCONFIG_ALLCONFIG' file is a config file which contains +(usually a subset of all) preset config symbols. These variable +settings are still subject to normal dependency checks. + +Examples:: + + KCONFIG_ALLCONFIG=custom-notebook.config make allnoconfig + +or:: + + KCONFIG_ALLCONFIG=mini.config make allnoconfig + +or:: + + make KCONFIG_ALLCONFIG=mini.config allnoconfig + +These examples will disable most options (allnoconfig) but enable or +disable the options that are explicitly listed in the specified +mini-config files. + +---------------------------------------------------------------------- + +Environment variables for 'randconfig' + +KCONFIG_SEED +------------ +You can set this to the integer value used to seed the RNG, if you want +to somehow debug the behaviour of the kconfig parser/frontends. +If not set, the current time will be used. + +KCONFIG_PROBABILITY +------------------- +This variable can be used to skew the probabilities. This variable can +be unset or empty, or set to three different formats: + + ======================= ================== ===================== + KCONFIG_PROBABILITY y:n split y:m:n split + ======================= ================== ===================== + unset or empty 50 : 50 33 : 33 : 34 + N N : 100-N N/2 : N/2 : 100-N + [1] N:M N+M : 100-(N+M) N : M : 100-(N+M) + [2] N:M:L N : 100-N M : L : 100-(M+L) + ======================= ================== ===================== + +where N, M and L are integers (in base 10) in the range [0,100], and so +that: + + [1] N+M is in the range [0,100] + + [2] M+L is in the range [0,100] + +Examples:: + + KCONFIG_PROBABILITY=10 + 10% of booleans will be set to 'y', 90% to 'n' + 5% of tristates will be set to 'y', 5% to 'm', 90% to 'n' + KCONFIG_PROBABILITY=15:25 + 40% of booleans will be set to 'y', 60% to 'n' + 15% of tristates will be set to 'y', 25% to 'm', 60% to 'n' + KCONFIG_PROBABILITY=10:15:15 + 10% of booleans will be set to 'y', 90% to 'n' + 15% of tristates will be set to 'y', 15% to 'm', 70% to 'n' + +---------------------------------------------------------------------- + +Environment variables for 'syncconfig' + +KCONFIG_NOSILENTUPDATE +---------------------- +If this variable has a non-blank value, it prevents silent kernel +config updates (requires explicit updates). + +KCONFIG_AUTOCONFIG +------------------ +This environment variable can be set to specify the path & name of the +"auto.conf" file. Its default value is "include/config/auto.conf". + +KCONFIG_TRISTATE +---------------- +This environment variable can be set to specify the path & name of the +"tristate.conf" file. Its default value is "include/config/tristate.conf". + +KCONFIG_AUTOHEADER +------------------ +This environment variable can be set to specify the path & name of the +"autoconf.h" (header) file. +Its default value is "include/generated/autoconf.h". + + +---------------------------------------------------------------------- + +menuconfig +---------- + +SEARCHING for CONFIG symbols + +Searching in menuconfig: + + The Search function searches for kernel configuration symbol + names, so you have to know something close to what you are + looking for. + + Example:: + + /hotplug + This lists all config symbols that contain "hotplug", + e.g., HOTPLUG_CPU, MEMORY_HOTPLUG. + + For search help, enter / followed by TAB-TAB (to highlight + ) and Enter. This will tell you that you can also use + regular expressions (regexes) in the search string, so if you + are not interested in MEMORY_HOTPLUG, you could try:: + + /^hotplug + + When searching, symbols are sorted thus: + + - first, exact matches, sorted alphabetically (an exact match + is when the search matches the complete symbol name); + - then, other matches, sorted alphabetically. + + For example: ^ATH.K matches: + + ATH5K ATH9K ATH5K_AHB ATH5K_DEBUG [...] ATH6KL ATH6KL_DEBUG + [...] ATH9K_AHB ATH9K_BTCOEX_SUPPORT ATH9K_COMMON [...] + + of which only ATH5K and ATH9K match exactly and so are sorted + first (and in alphabetical order), then come all other symbols, + sorted in alphabetical order. + +---------------------------------------------------------------------- + +User interface options for 'menuconfig' + +MENUCONFIG_COLOR +---------------- +It is possible to select different color themes using the variable +MENUCONFIG_COLOR. To select a theme use:: + + make MENUCONFIG_COLOR= menuconfig + +Available themes are:: + + - mono => selects colors suitable for monochrome displays + - blackbg => selects a color scheme with black background + - classic => theme with blue background. The classic look + - bluetitle => a LCD friendly version of classic. (default) + +MENUCONFIG_MODE +--------------- +This mode shows all sub-menus in one large tree. + +Example:: + + make MENUCONFIG_MODE=single_menu menuconfig + +---------------------------------------------------------------------- + +nconfig +------- + +nconfig is an alternate text-based configurator. It lists function +keys across the bottom of the terminal (window) that execute commands. +You can also just use the corresponding numeric key to execute the +commands unless you are in a data entry window. E.g., instead of F6 +for Save, you can just press 6. + +Use F1 for Global help or F3 for the Short help menu. + +Searching in nconfig: + + You can search either in the menu entry "prompt" strings + or in the configuration symbols. + + Use / to begin a search through the menu entries. This does + not support regular expressions. Use or for + Next hit and Previous hit, respectively. Use to + terminate the search mode. + + F8 (SymSearch) searches the configuration symbols for the + given string or regular expression (regex). + +NCONFIG_MODE +------------ +This mode shows all sub-menus in one large tree. + +Example:: + make NCONFIG_MODE=single_menu nconfig + +---------------------------------------------------------------------- + +xconfig +------- + +Searching in xconfig: + + The Search function searches for kernel configuration symbol + names, so you have to know something close to what you are + looking for. + + Example: + Ctrl-F hotplug + or + Menu: File, Search, hotplug + + lists all config symbol entries that contain "hotplug" in + the symbol name. In this Search dialog, you may change the + config setting for any of the entries that are not grayed out. + You can also enter a different search string without having + to return to the main menu. + + +---------------------------------------------------------------------- + +gconfig +------- + +Searching in gconfig: + + There is no search command in gconfig. However, gconfig does + have several different viewing choices, modes, and options. diff --git a/Documentation/kbuild/kconfig.txt b/Documentation/kbuild/kconfig.txt deleted file mode 100644 index 68c82914c0f3..000000000000 --- a/Documentation/kbuild/kconfig.txt +++ /dev/null @@ -1,272 +0,0 @@ -This file contains some assistance for using "make *config". - -Use "make help" to list all of the possible configuration targets. - -The xconfig ('qconf'), menuconfig ('mconf'), and nconfig ('nconf') -programs also have embedded help text. Be sure to check that for -navigation, search, and other general help text. - -====================================================================== -General --------------------------------------------------- - -New kernel releases often introduce new config symbols. Often more -important, new kernel releases may rename config symbols. When -this happens, using a previously working .config file and running -"make oldconfig" won't necessarily produce a working new kernel -for you, so you may find that you need to see what NEW kernel -symbols have been introduced. - -To see a list of new config symbols, use - - cp user/some/old.config .config - make listnewconfig - -and the config program will list any new symbols, one per line. - -Alternatively, you can use the brute force method: - - make oldconfig - scripts/diffconfig .config.old .config | less - -______________________________________________________________________ -Environment variables for '*config' - -KCONFIG_CONFIG --------------------------------------------------- -This environment variable can be used to specify a default kernel config -file name to override the default name of ".config". - -KCONFIG_OVERWRITECONFIG --------------------------------------------------- -If you set KCONFIG_OVERWRITECONFIG in the environment, Kconfig will not -break symlinks when .config is a symlink to somewhere else. - -CONFIG_ --------------------------------------------------- -If you set CONFIG_ in the environment, Kconfig will prefix all symbols -with its value when saving the configuration, instead of using the default, -"CONFIG_". - -______________________________________________________________________ -Environment variables for '{allyes/allmod/allno/rand}config' - -KCONFIG_ALLCONFIG --------------------------------------------------- -(partially based on lkml email from/by Rob Landley, re: miniconfig) --------------------------------------------------- -The allyesconfig/allmodconfig/allnoconfig/randconfig variants can also -use the environment variable KCONFIG_ALLCONFIG as a flag or a filename -that contains config symbols that the user requires to be set to a -specific value. If KCONFIG_ALLCONFIG is used without a filename where -KCONFIG_ALLCONFIG == "" or KCONFIG_ALLCONFIG == "1", "make *config" -checks for a file named "all{yes/mod/no/def/random}.config" -(corresponding to the *config command that was used) for symbol values -that are to be forced. If this file is not found, it checks for a -file named "all.config" to contain forced values. - -This enables you to create "miniature" config (miniconfig) or custom -config files containing just the config symbols that you are interested -in. Then the kernel config system generates the full .config file, -including symbols of your miniconfig file. - -This 'KCONFIG_ALLCONFIG' file is a config file which contains -(usually a subset of all) preset config symbols. These variable -settings are still subject to normal dependency checks. - -Examples: - KCONFIG_ALLCONFIG=custom-notebook.config make allnoconfig -or - KCONFIG_ALLCONFIG=mini.config make allnoconfig -or - make KCONFIG_ALLCONFIG=mini.config allnoconfig - -These examples will disable most options (allnoconfig) but enable or -disable the options that are explicitly listed in the specified -mini-config files. - -______________________________________________________________________ -Environment variables for 'randconfig' - -KCONFIG_SEED --------------------------------------------------- -You can set this to the integer value used to seed the RNG, if you want -to somehow debug the behaviour of the kconfig parser/frontends. -If not set, the current time will be used. - -KCONFIG_PROBABILITY --------------------------------------------------- -This variable can be used to skew the probabilities. This variable can -be unset or empty, or set to three different formats: - KCONFIG_PROBABILITY y:n split y:m:n split - ----------------------------------------------------------------- - unset or empty 50 : 50 33 : 33 : 34 - N N : 100-N N/2 : N/2 : 100-N - [1] N:M N+M : 100-(N+M) N : M : 100-(N+M) - [2] N:M:L N : 100-N M : L : 100-(M+L) - -where N, M and L are integers (in base 10) in the range [0,100], and so -that: - [1] N+M is in the range [0,100] - [2] M+L is in the range [0,100] - -Examples: - KCONFIG_PROBABILITY=10 - 10% of booleans will be set to 'y', 90% to 'n' - 5% of tristates will be set to 'y', 5% to 'm', 90% to 'n' - KCONFIG_PROBABILITY=15:25 - 40% of booleans will be set to 'y', 60% to 'n' - 15% of tristates will be set to 'y', 25% to 'm', 60% to 'n' - KCONFIG_PROBABILITY=10:15:15 - 10% of booleans will be set to 'y', 90% to 'n' - 15% of tristates will be set to 'y', 15% to 'm', 70% to 'n' - -______________________________________________________________________ -Environment variables for 'syncconfig' - -KCONFIG_NOSILENTUPDATE --------------------------------------------------- -If this variable has a non-blank value, it prevents silent kernel -config updates (requires explicit updates). - -KCONFIG_AUTOCONFIG --------------------------------------------------- -This environment variable can be set to specify the path & name of the -"auto.conf" file. Its default value is "include/config/auto.conf". - -KCONFIG_TRISTATE --------------------------------------------------- -This environment variable can be set to specify the path & name of the -"tristate.conf" file. Its default value is "include/config/tristate.conf". - -KCONFIG_AUTOHEADER --------------------------------------------------- -This environment variable can be set to specify the path & name of the -"autoconf.h" (header) file. -Its default value is "include/generated/autoconf.h". - - -====================================================================== -menuconfig --------------------------------------------------- - -SEARCHING for CONFIG symbols - -Searching in menuconfig: - - The Search function searches for kernel configuration symbol - names, so you have to know something close to what you are - looking for. - - Example: - /hotplug - This lists all config symbols that contain "hotplug", - e.g., HOTPLUG_CPU, MEMORY_HOTPLUG. - - For search help, enter / followed by TAB-TAB (to highlight - ) and Enter. This will tell you that you can also use - regular expressions (regexes) in the search string, so if you - are not interested in MEMORY_HOTPLUG, you could try - - /^hotplug - - When searching, symbols are sorted thus: - - first, exact matches, sorted alphabetically (an exact match - is when the search matches the complete symbol name); - - then, other matches, sorted alphabetically. - For example: ^ATH.K matches: - ATH5K ATH9K ATH5K_AHB ATH5K_DEBUG [...] ATH6KL ATH6KL_DEBUG - [...] ATH9K_AHB ATH9K_BTCOEX_SUPPORT ATH9K_COMMON [...] - of which only ATH5K and ATH9K match exactly and so are sorted - first (and in alphabetical order), then come all other symbols, - sorted in alphabetical order. - -______________________________________________________________________ -User interface options for 'menuconfig' - -MENUCONFIG_COLOR --------------------------------------------------- -It is possible to select different color themes using the variable -MENUCONFIG_COLOR. To select a theme use: - - make MENUCONFIG_COLOR= menuconfig - -Available themes are: - mono => selects colors suitable for monochrome displays - blackbg => selects a color scheme with black background - classic => theme with blue background. The classic look - bluetitle => a LCD friendly version of classic. (default) - -MENUCONFIG_MODE --------------------------------------------------- -This mode shows all sub-menus in one large tree. - -Example: - make MENUCONFIG_MODE=single_menu menuconfig - - -====================================================================== -nconfig --------------------------------------------------- - -nconfig is an alternate text-based configurator. It lists function -keys across the bottom of the terminal (window) that execute commands. -You can also just use the corresponding numeric key to execute the -commands unless you are in a data entry window. E.g., instead of F6 -for Save, you can just press 6. - -Use F1 for Global help or F3 for the Short help menu. - -Searching in nconfig: - - You can search either in the menu entry "prompt" strings - or in the configuration symbols. - - Use / to begin a search through the menu entries. This does - not support regular expressions. Use or for - Next hit and Previous hit, respectively. Use to - terminate the search mode. - - F8 (SymSearch) searches the configuration symbols for the - given string or regular expression (regex). - -NCONFIG_MODE --------------------------------------------------- -This mode shows all sub-menus in one large tree. - -Example: - make NCONFIG_MODE=single_menu nconfig - - -====================================================================== -xconfig --------------------------------------------------- - -Searching in xconfig: - - The Search function searches for kernel configuration symbol - names, so you have to know something close to what you are - looking for. - - Example: - Ctrl-F hotplug - or - Menu: File, Search, hotplug - - lists all config symbol entries that contain "hotplug" in - the symbol name. In this Search dialog, you may change the - config setting for any of the entries that are not grayed out. - You can also enter a different search string without having - to return to the main menu. - - -====================================================================== -gconfig --------------------------------------------------- - -Searching in gconfig: - - There is no search command in gconfig. However, gconfig does - have several different viewing choices, modes, and options. - -### diff --git a/Documentation/kbuild/makefiles.rst b/Documentation/kbuild/makefiles.rst new file mode 100644 index 000000000000..9274cdcc9bd2 --- /dev/null +++ b/Documentation/kbuild/makefiles.rst @@ -0,0 +1,1509 @@ +====================== +Linux Kernel Makefiles +====================== + +This document describes the Linux kernel Makefiles. + +.. Table of Contents + + === 1 Overview + === 2 Who does what + === 3 The kbuild files + --- 3.1 Goal definitions + --- 3.2 Built-in object goals - obj-y + --- 3.3 Loadable module goals - obj-m + --- 3.4 Objects which export symbols + --- 3.5 Library file goals - lib-y + --- 3.6 Descending down in directories + --- 3.7 Compilation flags + --- 3.8 Command line dependency + --- 3.9 Dependency tracking + --- 3.10 Special Rules + --- 3.11 $(CC) support functions + --- 3.12 $(LD) support functions + + === 4 Host Program support + --- 4.1 Simple Host Program + --- 4.2 Composite Host Programs + --- 4.3 Using C++ for host programs + --- 4.4 Controlling compiler options for host programs + --- 4.5 When host programs are actually built + --- 4.6 Using hostprogs-$(CONFIG_FOO) + + === 5 Kbuild clean infrastructure + + === 6 Architecture Makefiles + --- 6.1 Set variables to tweak the build to the architecture + --- 6.2 Add prerequisites to archheaders: + --- 6.3 Add prerequisites to archprepare: + --- 6.4 List directories to visit when descending + --- 6.5 Architecture-specific boot images + --- 6.6 Building non-kbuild targets + --- 6.7 Commands useful for building a boot image + --- 6.8 Custom kbuild commands + --- 6.9 Preprocessing linker scripts + --- 6.10 Generic header files + --- 6.11 Post-link pass + + === 7 Kbuild syntax for exported headers + --- 7.1 no-export-headers + --- 7.2 generic-y + --- 7.3 generated-y + --- 7.4 mandatory-y + + === 8 Kbuild Variables + === 9 Makefile language + === 10 Credits + === 11 TODO + +1 Overview +========== + +The Makefiles have five parts:: + + Makefile the top Makefile. + .config the kernel configuration file. + arch/$(ARCH)/Makefile the arch Makefile. + scripts/Makefile.* common rules etc. for all kbuild Makefiles. + kbuild Makefiles there are about 500 of these. + +The top Makefile reads the .config file, which comes from the kernel +configuration process. + +The top Makefile is responsible for building two major products: vmlinux +(the resident kernel image) and modules (any module files). +It builds these goals by recursively descending into the subdirectories of +the kernel source tree. +The list of subdirectories which are visited depends upon the kernel +configuration. The top Makefile textually includes an arch Makefile +with the name arch/$(ARCH)/Makefile. The arch Makefile supplies +architecture-specific information to the top Makefile. + +Each subdirectory has a kbuild Makefile which carries out the commands +passed down from above. The kbuild Makefile uses information from the +.config file to construct various file lists used by kbuild to build +any built-in or modular targets. + +scripts/Makefile.* contains all the definitions/rules etc. that +are used to build the kernel based on the kbuild makefiles. + + +2 Who does what +=============== + +People have four different relationships with the kernel Makefiles. + +*Users* are people who build kernels. These people type commands such as +"make menuconfig" or "make". They usually do not read or edit +any kernel Makefiles (or any other source files). + +*Normal developers* are people who work on features such as device +drivers, file systems, and network protocols. These people need to +maintain the kbuild Makefiles for the subsystem they are +working on. In order to do this effectively, they need some overall +knowledge about the kernel Makefiles, plus detailed knowledge about the +public interface for kbuild. + +*Arch developers* are people who work on an entire architecture, such +as sparc or ia64. Arch developers need to know about the arch Makefile +as well as kbuild Makefiles. + +*Kbuild developers* are people who work on the kernel build system itself. +These people need to know about all aspects of the kernel Makefiles. + +This document is aimed towards normal developers and arch developers. + + +3 The kbuild files +================== + +Most Makefiles within the kernel are kbuild Makefiles that use the +kbuild infrastructure. This chapter introduces the syntax used in the +kbuild makefiles. +The preferred name for the kbuild files are 'Makefile' but 'Kbuild' can +be used and if both a 'Makefile' and a 'Kbuild' file exists, then the 'Kbuild' +file will be used. + +Section 3.1 "Goal definitions" is a quick intro, further chapters provide +more details, with real examples. + +3.1 Goal definitions +-------------------- + + Goal definitions are the main part (heart) of the kbuild Makefile. + These lines define the files to be built, any special compilation + options, and any subdirectories to be entered recursively. + + The most simple kbuild makefile contains one line: + + Example:: + + obj-y += foo.o + + This tells kbuild that there is one object in that directory, named + foo.o. foo.o will be built from foo.c or foo.S. + + If foo.o shall be built as a module, the variable obj-m is used. + Therefore the following pattern is often used: + + Example:: + + obj-$(CONFIG_FOO) += foo.o + + $(CONFIG_FOO) evaluates to either y (for built-in) or m (for module). + If CONFIG_FOO is neither y nor m, then the file will not be compiled + nor linked. + +3.2 Built-in object goals - obj-y +--------------------------------- + + The kbuild Makefile specifies object files for vmlinux + in the $(obj-y) lists. These lists depend on the kernel + configuration. + + Kbuild compiles all the $(obj-y) files. It then calls + "$(AR) rcSTP" to merge these files into one built-in.a file. + This is a thin archive without a symbol table. It will be later + linked into vmlinux by scripts/link-vmlinux.sh + + The order of files in $(obj-y) is significant. Duplicates in + the lists are allowed: the first instance will be linked into + built-in.a and succeeding instances will be ignored. + + Link order is significant, because certain functions + (module_init() / __initcall) will be called during boot in the + order they appear. So keep in mind that changing the link + order may e.g. change the order in which your SCSI + controllers are detected, and thus your disks are renumbered. + + Example:: + + #drivers/isdn/i4l/Makefile + # Makefile for the kernel ISDN subsystem and device drivers. + # Each configuration option enables a list of files. + obj-$(CONFIG_ISDN_I4L) += isdn.o + obj-$(CONFIG_ISDN_PPP_BSDCOMP) += isdn_bsdcomp.o + +3.3 Loadable module goals - obj-m +--------------------------------- + + $(obj-m) specifies object files which are built as loadable + kernel modules. + + A module may be built from one source file or several source + files. In the case of one source file, the kbuild makefile + simply adds the file to $(obj-m). + + Example:: + + #drivers/isdn/i4l/Makefile + obj-$(CONFIG_ISDN_PPP_BSDCOMP) += isdn_bsdcomp.o + + Note: In this example $(CONFIG_ISDN_PPP_BSDCOMP) evaluates to 'm' + + If a kernel module is built from several source files, you specify + that you want to build a module in the same way as above; however, + kbuild needs to know which object files you want to build your + module from, so you have to tell it by setting a $(-y) + variable. + + Example:: + + #drivers/isdn/i4l/Makefile + obj-$(CONFIG_ISDN_I4L) += isdn.o + isdn-y := isdn_net_lib.o isdn_v110.o isdn_common.o + + In this example, the module name will be isdn.o. Kbuild will + compile the objects listed in $(isdn-y) and then run + "$(LD) -r" on the list of these files to generate isdn.o. + + Due to kbuild recognizing $(-y) for composite objects, + you can use the value of a `CONFIG_` symbol to optionally include an + object file as part of a composite object. + + Example:: + + #fs/ext2/Makefile + obj-$(CONFIG_EXT2_FS) += ext2.o + ext2-y := balloc.o dir.o file.o ialloc.o inode.o ioctl.o \ + namei.o super.o symlink.o + ext2-$(CONFIG_EXT2_FS_XATTR) += xattr.o xattr_user.o \ + xattr_trusted.o + + In this example, xattr.o, xattr_user.o and xattr_trusted.o are only + part of the composite object ext2.o if $(CONFIG_EXT2_FS_XATTR) + evaluates to 'y'. + + Note: Of course, when you are building objects into the kernel, + the syntax above will also work. So, if you have CONFIG_EXT2_FS=y, + kbuild will build an ext2.o file for you out of the individual + parts and then link this into built-in.a, as you would expect. + +3.4 Objects which export symbols +-------------------------------- + + No special notation is required in the makefiles for + modules exporting symbols. + +3.5 Library file goals - lib-y +------------------------------ + + Objects listed with obj-* are used for modules, or + combined in a built-in.a for that specific directory. + There is also the possibility to list objects that will + be included in a library, lib.a. + All objects listed with lib-y are combined in a single + library for that directory. + Objects that are listed in obj-y and additionally listed in + lib-y will not be included in the library, since they will + be accessible anyway. + For consistency, objects listed in lib-m will be included in lib.a. + + Note that the same kbuild makefile may list files to be built-in + and to be part of a library. Therefore the same directory + may contain both a built-in.a and a lib.a file. + + Example:: + + #arch/x86/lib/Makefile + lib-y := delay.o + + This will create a library lib.a based on delay.o. For kbuild to + actually recognize that there is a lib.a being built, the directory + shall be listed in libs-y. + + See also "6.4 List directories to visit when descending". + + Use of lib-y is normally restricted to `lib/` and `arch/*/lib`. + +3.6 Descending down in directories +---------------------------------- + + A Makefile is only responsible for building objects in its own + directory. Files in subdirectories should be taken care of by + Makefiles in these subdirs. The build system will automatically + invoke make recursively in subdirectories, provided you let it know of + them. + + To do so, obj-y and obj-m are used. + ext2 lives in a separate directory, and the Makefile present in fs/ + tells kbuild to descend down using the following assignment. + + Example:: + + #fs/Makefile + obj-$(CONFIG_EXT2_FS) += ext2/ + + If CONFIG_EXT2_FS is set to either 'y' (built-in) or 'm' (modular) + the corresponding obj- variable will be set, and kbuild will descend + down in the ext2 directory. + Kbuild only uses this information to decide that it needs to visit + the directory, it is the Makefile in the subdirectory that + specifies what is modular and what is built-in. + + It is good practice to use a `CONFIG_` variable when assigning directory + names. This allows kbuild to totally skip the directory if the + corresponding `CONFIG_` option is neither 'y' nor 'm'. + +3.7 Compilation flags +--------------------- + + ccflags-y, asflags-y and ldflags-y + These three flags apply only to the kbuild makefile in which they + are assigned. They are used for all the normal cc, as and ld + invocations happening during a recursive build. + Note: Flags with the same behaviour were previously named: + EXTRA_CFLAGS, EXTRA_AFLAGS and EXTRA_LDFLAGS. + They are still supported but their usage is deprecated. + + ccflags-y specifies options for compiling with $(CC). + + Example:: + + # drivers/acpi/acpica/Makefile + ccflags-y := -Os -D_LINUX -DBUILDING_ACPICA + ccflags-$(CONFIG_ACPI_DEBUG) += -DACPI_DEBUG_OUTPUT + + This variable is necessary because the top Makefile owns the + variable $(KBUILD_CFLAGS) and uses it for compilation flags for the + entire tree. + + asflags-y specifies options for assembling with $(AS). + + Example:: + + #arch/sparc/kernel/Makefile + asflags-y := -ansi + + ldflags-y specifies options for linking with $(LD). + + Example:: + + #arch/cris/boot/compressed/Makefile + ldflags-y += -T $(srctree)/$(src)/decompress_$(arch-y).lds + + subdir-ccflags-y, subdir-asflags-y + The two flags listed above are similar to ccflags-y and asflags-y. + The difference is that the subdir- variants have effect for the kbuild + file where they are present and all subdirectories. + Options specified using subdir-* are added to the commandline before + the options specified using the non-subdir variants. + + Example:: + + subdir-ccflags-y := -Werror + + CFLAGS_$@, AFLAGS_$@ + CFLAGS_$@ and AFLAGS_$@ only apply to commands in current + kbuild makefile. + + $(CFLAGS_$@) specifies per-file options for $(CC). The $@ + part has a literal value which specifies the file that it is for. + + Example:: + + # drivers/scsi/Makefile + CFLAGS_aha152x.o = -DAHA152X_STAT -DAUTOCONF + CFLAGS_gdth.o = # -DDEBUG_GDTH=2 -D__SERIAL__ -D__COM2__ \ + -DGDTH_STATISTICS + + These two lines specify compilation flags for aha152x.o and gdth.o. + + $(AFLAGS_$@) is a similar feature for source files in assembly + languages. + + Example:: + + # arch/arm/kernel/Makefile + AFLAGS_head.o := -DTEXT_OFFSET=$(TEXT_OFFSET) + AFLAGS_crunch-bits.o := -Wa,-mcpu=ep9312 + AFLAGS_iwmmxt.o := -Wa,-mcpu=iwmmxt + + +3.9 Dependency tracking +----------------------- + + Kbuild tracks dependencies on the following: + 1) All prerequisite files (both `*.c` and `*.h`) + 2) `CONFIG_` options used in all prerequisite files + 3) Command-line used to compile target + + Thus, if you change an option to $(CC) all affected files will + be re-compiled. + +3.10 Special Rules +------------------ + + Special rules are used when the kbuild infrastructure does + not provide the required support. A typical example is + header files generated during the build process. + Another example are the architecture-specific Makefiles which + need special rules to prepare boot images etc. + + Special rules are written as normal Make rules. + Kbuild is not executing in the directory where the Makefile is + located, so all special rules shall provide a relative + path to prerequisite files and target files. + + Two variables are used when defining special rules: + + $(src) + $(src) is a relative path which points to the directory + where the Makefile is located. Always use $(src) when + referring to files located in the src tree. + + $(obj) + $(obj) is a relative path which points to the directory + where the target is saved. Always use $(obj) when + referring to generated files. + + Example:: + + #drivers/scsi/Makefile + $(obj)/53c8xx_d.h: $(src)/53c7,8xx.scr $(src)/script_asm.pl + $(CPP) -DCHIP=810 - < $< | ... $(src)/script_asm.pl + + This is a special rule, following the normal syntax + required by make. + + The target file depends on two prerequisite files. References + to the target file are prefixed with $(obj), references + to prerequisites are referenced with $(src) (because they are not + generated files). + + $(kecho) + echoing information to user in a rule is often a good practice + but when execution "make -s" one does not expect to see any output + except for warnings/errors. + To support this kbuild defines $(kecho) which will echo out the + text following $(kecho) to stdout except if "make -s" is used. + + Example:: + + #arch/blackfin/boot/Makefile + $(obj)/vmImage: $(obj)/vmlinux.gz + $(call if_changed,uimage) + @$(kecho) 'Kernel: $@ is ready' + + +3.11 $(CC) support functions +---------------------------- + + The kernel may be built with several different versions of + $(CC), each supporting a unique set of features and options. + kbuild provides basic support to check for valid options for $(CC). + $(CC) is usually the gcc compiler, but other alternatives are + available. + + as-option + as-option is used to check if $(CC) -- when used to compile + assembler (`*.S`) files -- supports the given option. An optional + second option may be specified if the first option is not supported. + + Example:: + + #arch/sh/Makefile + cflags-y += $(call as-option,-Wa$(comma)-isa=$(isa-y),) + + In the above example, cflags-y will be assigned the option + -Wa$(comma)-isa=$(isa-y) if it is supported by $(CC). + The second argument is optional, and if supplied will be used + if first argument is not supported. + + cc-ldoption + cc-ldoption is used to check if $(CC) when used to link object files + supports the given option. An optional second option may be + specified if first option are not supported. + + Example:: + + #arch/x86/kernel/Makefile + vsyscall-flags += $(call cc-ldoption, -Wl$(comma)--hash-style=sysv) + + In the above example, vsyscall-flags will be assigned the option + -Wl$(comma)--hash-style=sysv if it is supported by $(CC). + The second argument is optional, and if supplied will be used + if first argument is not supported. + + as-instr + as-instr checks if the assembler reports a specific instruction + and then outputs either option1 or option2 + C escapes are supported in the test instruction + Note: as-instr-option uses KBUILD_AFLAGS for $(AS) options + + cc-option + cc-option is used to check if $(CC) supports a given option, and if + not supported to use an optional second option. + + Example:: + + #arch/x86/Makefile + cflags-y += $(call cc-option,-march=pentium-mmx,-march=i586) + + In the above example, cflags-y will be assigned the option + -march=pentium-mmx if supported by $(CC), otherwise -march=i586. + The second argument to cc-option is optional, and if omitted, + cflags-y will be assigned no value if first option is not supported. + Note: cc-option uses KBUILD_CFLAGS for $(CC) options + + cc-option-yn + cc-option-yn is used to check if gcc supports a given option + and return 'y' if supported, otherwise 'n'. + + Example:: + + #arch/ppc/Makefile + biarch := $(call cc-option-yn, -m32) + aflags-$(biarch) += -a32 + cflags-$(biarch) += -m32 + + In the above example, $(biarch) is set to y if $(CC) supports the -m32 + option. When $(biarch) equals 'y', the expanded variables $(aflags-y) + and $(cflags-y) will be assigned the values -a32 and -m32, + respectively. + Note: cc-option-yn uses KBUILD_CFLAGS for $(CC) options + + cc-disable-warning + cc-disable-warning checks if gcc supports a given warning and returns + the commandline switch to disable it. This special function is needed, + because gcc 4.4 and later accept any unknown -Wno-* option and only + warn about it if there is another warning in the source file. + + Example:: + + KBUILD_CFLAGS += $(call cc-disable-warning, unused-but-set-variable) + + In the above example, -Wno-unused-but-set-variable will be added to + KBUILD_CFLAGS only if gcc really accepts it. + + cc-ifversion + cc-ifversion tests the version of $(CC) and equals the fourth parameter + if version expression is true, or the fifth (if given) if the version + expression is false. + + Example:: + + #fs/reiserfs/Makefile + ccflags-y := $(call cc-ifversion, -lt, 0402, -O1) + + In this example, ccflags-y will be assigned the value -O1 if the + $(CC) version is less than 4.2. + cc-ifversion takes all the shell operators: + -eq, -ne, -lt, -le, -gt, and -ge + The third parameter may be a text as in this example, but it may also + be an expanded variable or a macro. + + cc-cross-prefix + cc-cross-prefix is used to check if there exists a $(CC) in path with + one of the listed prefixes. The first prefix where there exist a + prefix$(CC) in the PATH is returned - and if no prefix$(CC) is found + then nothing is returned. + Additional prefixes are separated by a single space in the + call of cc-cross-prefix. + This functionality is useful for architecture Makefiles that try + to set CROSS_COMPILE to well-known values but may have several + values to select between. + It is recommended only to try to set CROSS_COMPILE if it is a cross + build (host arch is different from target arch). And if CROSS_COMPILE + is already set then leave it with the old value. + + Example:: + + #arch/m68k/Makefile + ifneq ($(SUBARCH),$(ARCH)) + ifeq ($(CROSS_COMPILE),) + CROSS_COMPILE := $(call cc-cross-prefix, m68k-linux-gnu-) + endif + endif + +3.12 $(LD) support functions +---------------------------- + + ld-option + ld-option is used to check if $(LD) supports the supplied option. + ld-option takes two options as arguments. + The second argument is an optional option that can be used if the + first option is not supported by $(LD). + + Example:: + + #Makefile + LDFLAGS_vmlinux += $(call ld-option, -X) + + +4 Host Program support +====================== + +Kbuild supports building executables on the host for use during the +compilation stage. +Two steps are required in order to use a host executable. + +The first step is to tell kbuild that a host program exists. This is +done utilising the variable hostprogs-y. + +The second step is to add an explicit dependency to the executable. +This can be done in two ways. Either add the dependency in a rule, +or utilise the variable $(always). +Both possibilities are described in the following. + +4.1 Simple Host Program +----------------------- + + In some cases there is a need to compile and run a program on the + computer where the build is running. + The following line tells kbuild that the program bin2hex shall be + built on the build host. + + Example:: + + hostprogs-y := bin2hex + + Kbuild assumes in the above example that bin2hex is made from a single + c-source file named bin2hex.c located in the same directory as + the Makefile. + +4.2 Composite Host Programs +--------------------------- + + Host programs can be made up based on composite objects. + The syntax used to define composite objects for host programs is + similar to the syntax used for kernel objects. + $(-objs) lists all objects used to link the final + executable. + + Example:: + + #scripts/lxdialog/Makefile + hostprogs-y := lxdialog + lxdialog-objs := checklist.o lxdialog.o + + Objects with extension .o are compiled from the corresponding .c + files. In the above example, checklist.c is compiled to checklist.o + and lxdialog.c is compiled to lxdialog.o. + + Finally, the two .o files are linked to the executable, lxdialog. + Note: The syntax -y is not permitted for host-programs. + +4.3 Using C++ for host programs +------------------------------- + + kbuild offers support for host programs written in C++. This was + introduced solely to support kconfig, and is not recommended + for general use. + + Example:: + + #scripts/kconfig/Makefile + hostprogs-y := qconf + qconf-cxxobjs := qconf.o + + In the example above the executable is composed of the C++ file + qconf.cc - identified by $(qconf-cxxobjs). + + If qconf is composed of a mixture of .c and .cc files, then an + additional line can be used to identify this. + + Example:: + + #scripts/kconfig/Makefile + hostprogs-y := qconf + qconf-cxxobjs := qconf.o + qconf-objs := check.o + +4.4 Controlling compiler options for host programs +-------------------------------------------------- + + When compiling host programs, it is possible to set specific flags. + The programs will always be compiled utilising $(HOSTCC) passed + the options specified in $(KBUILD_HOSTCFLAGS). + To set flags that will take effect for all host programs created + in that Makefile, use the variable HOST_EXTRACFLAGS. + + Example:: + + #scripts/lxdialog/Makefile + HOST_EXTRACFLAGS += -I/usr/include/ncurses + + To set specific flags for a single file the following construction + is used: + + Example:: + + #arch/ppc64/boot/Makefile + HOSTCFLAGS_piggyback.o := -DKERNELBASE=$(KERNELBASE) + + It is also possible to specify additional options to the linker. + + Example:: + + #scripts/kconfig/Makefile + HOSTLDLIBS_qconf := -L$(QTDIR)/lib + + When linking qconf, it will be passed the extra option + "-L$(QTDIR)/lib". + +4.5 When host programs are actually built +----------------------------------------- + + Kbuild will only build host-programs when they are referenced + as a prerequisite. + This is possible in two ways: + + (1) List the prerequisite explicitly in a special rule. + + Example:: + + #drivers/pci/Makefile + hostprogs-y := gen-devlist + $(obj)/devlist.h: $(src)/pci.ids $(obj)/gen-devlist + ( cd $(obj); ./gen-devlist ) < $< + + The target $(obj)/devlist.h will not be built before + $(obj)/gen-devlist is updated. Note that references to + the host programs in special rules must be prefixed with $(obj). + + (2) Use $(always) + + When there is no suitable special rule, and the host program + shall be built when a makefile is entered, the $(always) + variable shall be used. + + Example:: + + #scripts/lxdialog/Makefile + hostprogs-y := lxdialog + always := $(hostprogs-y) + + This will tell kbuild to build lxdialog even if not referenced in + any rule. + +4.6 Using hostprogs-$(CONFIG_FOO) +--------------------------------- + + A typical pattern in a Kbuild file looks like this: + + Example:: + + #scripts/Makefile + hostprogs-$(CONFIG_KALLSYMS) += kallsyms + + Kbuild knows about both 'y' for built-in and 'm' for module. + So if a config symbol evaluates to 'm', kbuild will still build + the binary. In other words, Kbuild handles hostprogs-m exactly + like hostprogs-y. But only hostprogs-y is recommended to be used + when no CONFIG symbols are involved. + +5 Kbuild clean infrastructure +============================= + +"make clean" deletes most generated files in the obj tree where the kernel +is compiled. This includes generated files such as host programs. +Kbuild knows targets listed in $(hostprogs-y), $(hostprogs-m), $(always), +$(extra-y) and $(targets). They are all deleted during "make clean". +Files matching the patterns "*.[oas]", "*.ko", plus some additional files +generated by kbuild are deleted all over the kernel src tree when +"make clean" is executed. + +Additional files can be specified in kbuild makefiles by use of $(clean-files). + + Example:: + + #lib/Makefile + clean-files := crc32table.h + +When executing "make clean", the file "crc32table.h" will be deleted. +Kbuild will assume files to be in the same relative directory as the +Makefile, except if prefixed with $(objtree). + +To delete a directory hierarchy use: + + Example:: + + #scripts/package/Makefile + clean-dirs := $(objtree)/debian/ + +This will delete the directory debian in the toplevel directory, including all +subdirectories. + +To exclude certain files from make clean, use the $(no-clean-files) variable. +This is only a special case used in the top level Kbuild file: + + Example:: + + #Kbuild + no-clean-files := $(bounds-file) $(offsets-file) + +Usually kbuild descends down in subdirectories due to "obj-* := dir/", +but in the architecture makefiles where the kbuild infrastructure +is not sufficient this sometimes needs to be explicit. + + Example:: + + #arch/x86/boot/Makefile + subdir- := compressed/ + +The above assignment instructs kbuild to descend down in the +directory compressed/ when "make clean" is executed. + +To support the clean infrastructure in the Makefiles that build the +final bootimage there is an optional target named archclean: + + Example:: + + #arch/x86/Makefile + archclean: + $(Q)$(MAKE) $(clean)=arch/x86/boot + +When "make clean" is executed, make will descend down in arch/x86/boot, +and clean as usual. The Makefile located in arch/x86/boot/ may use +the subdir- trick to descend further down. + +Note 1: arch/$(ARCH)/Makefile cannot use "subdir-", because that file is +included in the top level makefile, and the kbuild infrastructure +is not operational at that point. + +Note 2: All directories listed in core-y, libs-y, drivers-y and net-y will +be visited during "make clean". + +6 Architecture Makefiles +======================== + +The top level Makefile sets up the environment and does the preparation, +before starting to descend down in the individual directories. +The top level makefile contains the generic part, whereas +arch/$(ARCH)/Makefile contains what is required to set up kbuild +for said architecture. +To do so, arch/$(ARCH)/Makefile sets up a number of variables and defines +a few targets. + +When kbuild executes, the following steps are followed (roughly): + +1) Configuration of the kernel => produce .config +2) Store kernel version in include/linux/version.h +3) Updating all other prerequisites to the target prepare: + - Additional prerequisites are specified in arch/$(ARCH)/Makefile +4) Recursively descend down in all directories listed in + init-* core* drivers-* net-* libs-* and build all targets. + - The values of the above variables are expanded in arch/$(ARCH)/Makefile. +5) All object files are then linked and the resulting file vmlinux is + located at the root of the obj tree. + The very first objects linked are listed in head-y, assigned by + arch/$(ARCH)/Makefile. +6) Finally, the architecture-specific part does any required post processing + and builds the final bootimage. + - This includes building boot records + - Preparing initrd images and the like + + +6.1 Set variables to tweak the build to the architecture +-------------------------------------------------------- + + LDFLAGS + Generic $(LD) options + + Flags used for all invocations of the linker. + Often specifying the emulation is sufficient. + + Example:: + + #arch/s390/Makefile + LDFLAGS := -m elf_s390 + + Note: ldflags-y can be used to further customise + the flags used. See chapter 3.7. + + LDFLAGS_vmlinux + Options for $(LD) when linking vmlinux + + LDFLAGS_vmlinux is used to specify additional flags to pass to + the linker when linking the final vmlinux image. + LDFLAGS_vmlinux uses the LDFLAGS_$@ support. + + Example:: + + #arch/x86/Makefile + LDFLAGS_vmlinux := -e stext + + OBJCOPYFLAGS + objcopy flags + + When $(call if_changed,objcopy) is used to translate a .o file, + the flags specified in OBJCOPYFLAGS will be used. + $(call if_changed,objcopy) is often used to generate raw binaries on + vmlinux. + + Example:: + + #arch/s390/Makefile + OBJCOPYFLAGS := -O binary + + #arch/s390/boot/Makefile + $(obj)/image: vmlinux FORCE + $(call if_changed,objcopy) + + In this example, the binary $(obj)/image is a binary version of + vmlinux. The usage of $(call if_changed,xxx) will be described later. + + KBUILD_AFLAGS + $(AS) assembler flags + + Default value - see top level Makefile + Append or modify as required per architecture. + + Example:: + + #arch/sparc64/Makefile + KBUILD_AFLAGS += -m64 -mcpu=ultrasparc + + KBUILD_CFLAGS + $(CC) compiler flags + + Default value - see top level Makefile + Append or modify as required per architecture. + + Often, the KBUILD_CFLAGS variable depends on the configuration. + + Example:: + + #arch/x86/boot/compressed/Makefile + cflags-$(CONFIG_X86_32) := -march=i386 + cflags-$(CONFIG_X86_64) := -mcmodel=small + KBUILD_CFLAGS += $(cflags-y) + + Many arch Makefiles dynamically run the target C compiler to + probe supported options:: + + #arch/x86/Makefile + + ... + cflags-$(CONFIG_MPENTIUMII) += $(call cc-option,\ + -march=pentium2,-march=i686) + ... + # Disable unit-at-a-time mode ... + KBUILD_CFLAGS += $(call cc-option,-fno-unit-at-a-time) + ... + + + The first example utilises the trick that a config option expands + to 'y' when selected. + + KBUILD_AFLAGS_KERNEL + $(AS) options specific for built-in + + $(KBUILD_AFLAGS_KERNEL) contains extra C compiler flags used to compile + resident kernel code. + + KBUILD_AFLAGS_MODULE + Options for $(AS) when building modules + + $(KBUILD_AFLAGS_MODULE) is used to add arch-specific options that + are used for $(AS). + + From commandline AFLAGS_MODULE shall be used (see kbuild.txt). + + KBUILD_CFLAGS_KERNEL + $(CC) options specific for built-in + + $(KBUILD_CFLAGS_KERNEL) contains extra C compiler flags used to compile + resident kernel code. + + KBUILD_CFLAGS_MODULE + Options for $(CC) when building modules + + $(KBUILD_CFLAGS_MODULE) is used to add arch-specific options that + are used for $(CC). + From commandline CFLAGS_MODULE shall be used (see kbuild.txt). + + KBUILD_LDFLAGS_MODULE + Options for $(LD) when linking modules + + $(KBUILD_LDFLAGS_MODULE) is used to add arch-specific options + used when linking modules. This is often a linker script. + + From commandline LDFLAGS_MODULE shall be used (see kbuild.txt). + + KBUILD_ARFLAGS Options for $(AR) when creating archives + + $(KBUILD_ARFLAGS) set by the top level Makefile to "D" (deterministic + mode) if this option is supported by $(AR). + + ARCH_CPPFLAGS, ARCH_AFLAGS, ARCH_CFLAGS Overrides the kbuild defaults + + These variables are appended to the KBUILD_CPPFLAGS, + KBUILD_AFLAGS, and KBUILD_CFLAGS, respectively, after the + top-level Makefile has set any other flags. This provides a + means for an architecture to override the defaults. + + +6.2 Add prerequisites to archheaders +------------------------------------ + + The archheaders: rule is used to generate header files that + may be installed into user space by "make header_install" or + "make headers_install_all". In order to support + "make headers_install_all", this target has to be able to run + on an unconfigured tree, or a tree configured for another + architecture. + + It is run before "make archprepare" when run on the + architecture itself. + + +6.3 Add prerequisites to archprepare +------------------------------------ + + The archprepare: rule is used to list prerequisites that need to be + built before starting to descend down in the subdirectories. + This is usually used for header files containing assembler constants. + + Example:: + + #arch/arm/Makefile + archprepare: maketools + + In this example, the file target maketools will be processed + before descending down in the subdirectories. + See also chapter XXX-TODO that describe how kbuild supports + generating offset header files. + + +6.4 List directories to visit when descending +--------------------------------------------- + + An arch Makefile cooperates with the top Makefile to define variables + which specify how to build the vmlinux file. Note that there is no + corresponding arch-specific section for modules; the module-building + machinery is all architecture-independent. + + + head-y, init-y, core-y, libs-y, drivers-y, net-y + $(head-y) lists objects to be linked first in vmlinux. + + $(libs-y) lists directories where a lib.a archive can be located. + + The rest list directories where a built-in.a object file can be + located. + + $(init-y) objects will be located after $(head-y). + + Then the rest follows in this order: + + $(core-y), $(libs-y), $(drivers-y) and $(net-y). + + The top level Makefile defines values for all generic directories, + and arch/$(ARCH)/Makefile only adds architecture-specific + directories. + + Example:: + + #arch/sparc64/Makefile + core-y += arch/sparc64/kernel/ + libs-y += arch/sparc64/prom/ arch/sparc64/lib/ + drivers-$(CONFIG_OPROFILE) += arch/sparc64/oprofile/ + + +6.5 Architecture-specific boot images +------------------------------------- + + An arch Makefile specifies goals that take the vmlinux file, compress + it, wrap it in bootstrapping code, and copy the resulting files + somewhere. This includes various kinds of installation commands. + The actual goals are not standardized across architectures. + + It is common to locate any additional processing in a boot/ + directory below arch/$(ARCH)/. + + Kbuild does not provide any smart way to support building a + target specified in boot/. Therefore arch/$(ARCH)/Makefile shall + call make manually to build a target in boot/. + + The recommended approach is to include shortcuts in + arch/$(ARCH)/Makefile, and use the full path when calling down + into the arch/$(ARCH)/boot/Makefile. + + Example:: + + #arch/x86/Makefile + boot := arch/x86/boot + bzImage: vmlinux + $(Q)$(MAKE) $(build)=$(boot) $(boot)/$@ + + "$(Q)$(MAKE) $(build)=" is the recommended way to invoke + make in a subdirectory. + + There are no rules for naming architecture-specific targets, + but executing "make help" will list all relevant targets. + To support this, $(archhelp) must be defined. + + Example:: + + #arch/x86/Makefile + define archhelp + echo '* bzImage - Image (arch/$(ARCH)/boot/bzImage)' + endif + + When make is executed without arguments, the first goal encountered + will be built. In the top level Makefile the first goal present + is all:. + An architecture shall always, per default, build a bootable image. + In "make help", the default goal is highlighted with a '*'. + Add a new prerequisite to all: to select a default goal different + from vmlinux. + + Example:: + + #arch/x86/Makefile + all: bzImage + + When "make" is executed without arguments, bzImage will be built. + +6.6 Building non-kbuild targets +------------------------------- + + extra-y + extra-y specifies additional targets created in the current + directory, in addition to any targets specified by `obj-*`. + + Listing all targets in extra-y is required for two purposes: + + 1) Enable kbuild to check changes in command lines + + - When $(call if_changed,xxx) is used + + 2) kbuild knows what files to delete during "make clean" + + Example:: + + #arch/x86/kernel/Makefile + extra-y := head.o init_task.o + + In this example, extra-y is used to list object files that + shall be built, but shall not be linked as part of built-in.a. + + +6.7 Commands useful for building a boot image +--------------------------------------------- + + Kbuild provides a few macros that are useful when building a + boot image. + + if_changed + if_changed is the infrastructure used for the following commands. + + Usage:: + + target: source(s) FORCE + $(call if_changed,ld/objcopy/gzip/...) + + When the rule is evaluated, it is checked to see if any files + need an update, or the command line has changed since the last + invocation. The latter will force a rebuild if any options + to the executable have changed. + Any target that utilises if_changed must be listed in $(targets), + otherwise the command line check will fail, and the target will + always be built. + Assignments to $(targets) are without $(obj)/ prefix. + if_changed may be used in conjunction with custom commands as + defined in 6.8 "Custom kbuild commands". + + Note: It is a typical mistake to forget the FORCE prerequisite. + Another common pitfall is that whitespace is sometimes + significant; for instance, the below will fail (note the extra space + after the comma):: + + target: source(s) FORCE + + **WRONG!** $(call if_changed, ld/objcopy/gzip/...) + + Note: + if_changed should not be used more than once per target. + It stores the executed command in a corresponding .cmd + + file and multiple calls would result in overwrites and + unwanted results when the target is up to date and only the + tests on changed commands trigger execution of commands. + + ld + Link target. Often, LDFLAGS_$@ is used to set specific options to ld. + + Example:: + + #arch/x86/boot/Makefile + LDFLAGS_bootsect := -Ttext 0x0 -s --oformat binary + LDFLAGS_setup := -Ttext 0x0 -s --oformat binary -e begtext + + targets += setup setup.o bootsect bootsect.o + $(obj)/setup $(obj)/bootsect: %: %.o FORCE + $(call if_changed,ld) + + In this example, there are two possible targets, requiring different + options to the linker. The linker options are specified using the + LDFLAGS_$@ syntax - one for each potential target. + $(targets) are assigned all potential targets, by which kbuild knows + the targets and will: + + 1) check for commandline changes + 2) delete target during make clean + + The ": %: %.o" part of the prerequisite is a shorthand that + frees us from listing the setup.o and bootsect.o files. + + Note: + It is a common mistake to forget the "targets :=" assignment, + resulting in the target file being recompiled for no + obvious reason. + + objcopy + Copy binary. Uses OBJCOPYFLAGS usually specified in + arch/$(ARCH)/Makefile. + OBJCOPYFLAGS_$@ may be used to set additional options. + + gzip + Compress target. Use maximum compression to compress target. + + Example:: + + #arch/x86/boot/compressed/Makefile + $(obj)/vmlinux.bin.gz: $(vmlinux.bin.all-y) FORCE + $(call if_changed,gzip) + + dtc + Create flattened device tree blob object suitable for linking + into vmlinux. Device tree blobs linked into vmlinux are placed + in an init section in the image. Platform code *must* copy the + blob to non-init memory prior to calling unflatten_device_tree(). + + To use this command, simply add `*.dtb` into obj-y or targets, or make + some other target depend on `%.dtb` + + A central rule exists to create `$(obj)/%.dtb` from `$(src)/%.dts`; + architecture Makefiles do no need to explicitly write out that rule. + + Example:: + + targets += $(dtb-y) + DTC_FLAGS ?= -p 1024 + +6.8 Custom kbuild commands +-------------------------- + + When kbuild is executing with KBUILD_VERBOSE=0, then only a shorthand + of a command is normally displayed. + To enable this behaviour for custom commands kbuild requires + two variables to be set:: + + quiet_cmd_ - what shall be echoed + cmd_ - the command to execute + + Example:: + + # + quiet_cmd_image = BUILD $@ + cmd_image = $(obj)/tools/build $(BUILDFLAGS) \ + $(obj)/vmlinux.bin > $@ + + targets += bzImage + $(obj)/bzImage: $(obj)/vmlinux.bin $(obj)/tools/build FORCE + $(call if_changed,image) + @echo 'Kernel: $@ is ready' + + When updating the $(obj)/bzImage target, the line: + + BUILD arch/x86/boot/bzImage + + will be displayed with "make KBUILD_VERBOSE=0". + + +--- 6.9 Preprocessing linker scripts + + When the vmlinux image is built, the linker script + arch/$(ARCH)/kernel/vmlinux.lds is used. + The script is a preprocessed variant of the file vmlinux.lds.S + located in the same directory. + kbuild knows .lds files and includes a rule `*lds.S` -> `*lds`. + + Example:: + + #arch/x86/kernel/Makefile + always := vmlinux.lds + + #Makefile + export CPPFLAGS_vmlinux.lds += -P -C -U$(ARCH) + + The assignment to $(always) is used to tell kbuild to build the + target vmlinux.lds. + The assignment to $(CPPFLAGS_vmlinux.lds) tells kbuild to use the + specified options when building the target vmlinux.lds. + + When building the `*.lds` target, kbuild uses the variables:: + + KBUILD_CPPFLAGS : Set in top-level Makefile + cppflags-y : May be set in the kbuild makefile + CPPFLAGS_$(@F) : Target-specific flags. + Note that the full filename is used in this + assignment. + + The kbuild infrastructure for `*lds` files is used in several + architecture-specific files. + +6.10 Generic header files +------------------------- + + The directory include/asm-generic contains the header files + that may be shared between individual architectures. + The recommended approach how to use a generic header file is + to list the file in the Kbuild file. + See "7.2 generic-y" for further info on syntax etc. + +6.11 Post-link pass +------------------- + + If the file arch/xxx/Makefile.postlink exists, this makefile + will be invoked for post-link objects (vmlinux and modules.ko) + for architectures to run post-link passes on. Must also handle + the clean target. + + This pass runs after kallsyms generation. If the architecture + needs to modify symbol locations, rather than manipulate the + kallsyms, it may be easier to add another postlink target for + .tmp_vmlinux? targets to be called from link-vmlinux.sh. + + For example, powerpc uses this to check relocation sanity of + the linked vmlinux file. + +7 Kbuild syntax for exported headers +------------------------------------ + +The kernel includes a set of headers that is exported to userspace. +Many headers can be exported as-is but other headers require a +minimal pre-processing before they are ready for user-space. +The pre-processing does: + +- drop kernel-specific annotations +- drop include of compiler.h +- drop all sections that are kernel internal (guarded by `ifdef __KERNEL__`) + +All headers under include/uapi/, include/generated/uapi/, +arch//include/uapi/ and arch//include/generated/uapi/ +are exported. + +A Kbuild file may be defined under arch//include/uapi/asm/ and +arch//include/asm/ to list asm files coming from asm-generic. +See subsequent chapter for the syntax of the Kbuild file. + +7.1 no-export-headers +--------------------- + + no-export-headers is essentially used by include/uapi/linux/Kbuild to + avoid exporting specific headers (e.g. kvm.h) on architectures that do + not support it. It should be avoided as much as possible. + +7.2 generic-y +------------- + + If an architecture uses a verbatim copy of a header from + include/asm-generic then this is listed in the file + arch/$(ARCH)/include/asm/Kbuild like this: + + Example:: + + #arch/x86/include/asm/Kbuild + generic-y += termios.h + generic-y += rtc.h + + During the prepare phase of the build a wrapper include + file is generated in the directory:: + + arch/$(ARCH)/include/generated/asm + + When a header is exported where the architecture uses + the generic header a similar wrapper is generated as part + of the set of exported headers in the directory:: + + usr/include/asm + + The generated wrapper will in both cases look like the following: + + Example: termios.h:: + + #include + +7.3 generated-y +--------------- + + If an architecture generates other header files alongside generic-y + wrappers, generated-y specifies them. + + This prevents them being treated as stale asm-generic wrappers and + removed. + + Example:: + + #arch/x86/include/asm/Kbuild + generated-y += syscalls_32.h + +7.4 mandatory-y +--------------- + + mandatory-y is essentially used by include/(uapi/)asm-generic/Kbuild + to define the minimum set of ASM headers that all architectures must have. + + This works like optional generic-y. If a mandatory header is missing + in arch/$(ARCH)/include/(uapi/)/asm, Kbuild will automatically generate + a wrapper of the asm-generic one. + + The convention is to list one subdir per line and + preferably in alphabetic order. + +8 Kbuild Variables +================== + +The top Makefile exports the following variables: + + VERSION, PATCHLEVEL, SUBLEVEL, EXTRAVERSION + These variables define the current kernel version. A few arch + Makefiles actually use these values directly; they should use + $(KERNELRELEASE) instead. + + $(VERSION), $(PATCHLEVEL), and $(SUBLEVEL) define the basic + three-part version number, such as "2", "4", and "0". These three + values are always numeric. + + $(EXTRAVERSION) defines an even tinier sublevel for pre-patches + or additional patches. It is usually some non-numeric string + such as "-pre4", and is often blank. + + KERNELRELEASE + $(KERNELRELEASE) is a single string such as "2.4.0-pre4", suitable + for constructing installation directory names or showing in + version strings. Some arch Makefiles use it for this purpose. + + ARCH + This variable defines the target architecture, such as "i386", + "arm", or "sparc". Some kbuild Makefiles test $(ARCH) to + determine which files to compile. + + By default, the top Makefile sets $(ARCH) to be the same as the + host system architecture. For a cross build, a user may + override the value of $(ARCH) on the command line:: + + make ARCH=m68k ... + + + INSTALL_PATH + This variable defines a place for the arch Makefiles to install + the resident kernel image and System.map file. + Use this for architecture-specific install targets. + + INSTALL_MOD_PATH, MODLIB + $(INSTALL_MOD_PATH) specifies a prefix to $(MODLIB) for module + installation. This variable is not defined in the Makefile but + may be passed in by the user if desired. + + $(MODLIB) specifies the directory for module installation. + The top Makefile defines $(MODLIB) to + $(INSTALL_MOD_PATH)/lib/modules/$(KERNELRELEASE). The user may + override this value on the command line if desired. + + INSTALL_MOD_STRIP + If this variable is specified, it will cause modules to be stripped + after they are installed. If INSTALL_MOD_STRIP is '1', then the + default option --strip-debug will be used. Otherwise, the + INSTALL_MOD_STRIP value will be used as the option(s) to the strip + command. + + +9 Makefile language +=================== + +The kernel Makefiles are designed to be run with GNU Make. The Makefiles +use only the documented features of GNU Make, but they do use many +GNU extensions. + +GNU Make supports elementary list-processing functions. The kernel +Makefiles use a novel style of list building and manipulation with few +"if" statements. + +GNU Make has two assignment operators, ":=" and "=". ":=" performs +immediate evaluation of the right-hand side and stores an actual string +into the left-hand side. "=" is like a formula definition; it stores the +right-hand side in an unevaluated form and then evaluates this form each +time the left-hand side is used. + +There are some cases where "=" is appropriate. Usually, though, ":=" +is the right choice. + +10 Credits +========== + +- Original version made by Michael Elizabeth Chastain, +- Updates by Kai Germaschewski +- Updates by Sam Ravnborg +- Language QA by Jan Engelhardt + +11 TODO +======= + +- Describe how kbuild supports shipped files with _shipped. +- Generating offset header files. +- Add more variables to section 7? diff --git a/Documentation/kbuild/makefiles.txt b/Documentation/kbuild/makefiles.txt deleted file mode 100644 index d65ad5746f94..000000000000 --- a/Documentation/kbuild/makefiles.txt +++ /dev/null @@ -1,1369 +0,0 @@ -Linux Kernel Makefiles - -This document describes the Linux kernel Makefiles. - -=== Table of Contents - - === 1 Overview - === 2 Who does what - === 3 The kbuild files - --- 3.1 Goal definitions - --- 3.2 Built-in object goals - obj-y - --- 3.3 Loadable module goals - obj-m - --- 3.4 Objects which export symbols - --- 3.5 Library file goals - lib-y - --- 3.6 Descending down in directories - --- 3.7 Compilation flags - --- 3.8 Command line dependency - --- 3.9 Dependency tracking - --- 3.10 Special Rules - --- 3.11 $(CC) support functions - --- 3.12 $(LD) support functions - - === 4 Host Program support - --- 4.1 Simple Host Program - --- 4.2 Composite Host Programs - --- 4.3 Using C++ for host programs - --- 4.4 Controlling compiler options for host programs - --- 4.5 When host programs are actually built - --- 4.6 Using hostprogs-$(CONFIG_FOO) - - === 5 Kbuild clean infrastructure - - === 6 Architecture Makefiles - --- 6.1 Set variables to tweak the build to the architecture - --- 6.2 Add prerequisites to archheaders: - --- 6.3 Add prerequisites to archprepare: - --- 6.4 List directories to visit when descending - --- 6.5 Architecture-specific boot images - --- 6.6 Building non-kbuild targets - --- 6.7 Commands useful for building a boot image - --- 6.8 Custom kbuild commands - --- 6.9 Preprocessing linker scripts - --- 6.10 Generic header files - --- 6.11 Post-link pass - - === 7 Kbuild syntax for exported headers - --- 7.1 no-export-headers - --- 7.2 generic-y - --- 7.3 generated-y - --- 7.4 mandatory-y - - === 8 Kbuild Variables - === 9 Makefile language - === 10 Credits - === 11 TODO - -=== 1 Overview - -The Makefiles have five parts: - - Makefile the top Makefile. - .config the kernel configuration file. - arch/$(ARCH)/Makefile the arch Makefile. - scripts/Makefile.* common rules etc. for all kbuild Makefiles. - kbuild Makefiles there are about 500 of these. - -The top Makefile reads the .config file, which comes from the kernel -configuration process. - -The top Makefile is responsible for building two major products: vmlinux -(the resident kernel image) and modules (any module files). -It builds these goals by recursively descending into the subdirectories of -the kernel source tree. -The list of subdirectories which are visited depends upon the kernel -configuration. The top Makefile textually includes an arch Makefile -with the name arch/$(ARCH)/Makefile. The arch Makefile supplies -architecture-specific information to the top Makefile. - -Each subdirectory has a kbuild Makefile which carries out the commands -passed down from above. The kbuild Makefile uses information from the -.config file to construct various file lists used by kbuild to build -any built-in or modular targets. - -scripts/Makefile.* contains all the definitions/rules etc. that -are used to build the kernel based on the kbuild makefiles. - - -=== 2 Who does what - -People have four different relationships with the kernel Makefiles. - -*Users* are people who build kernels. These people type commands such as -"make menuconfig" or "make". They usually do not read or edit -any kernel Makefiles (or any other source files). - -*Normal developers* are people who work on features such as device -drivers, file systems, and network protocols. These people need to -maintain the kbuild Makefiles for the subsystem they are -working on. In order to do this effectively, they need some overall -knowledge about the kernel Makefiles, plus detailed knowledge about the -public interface for kbuild. - -*Arch developers* are people who work on an entire architecture, such -as sparc or ia64. Arch developers need to know about the arch Makefile -as well as kbuild Makefiles. - -*Kbuild developers* are people who work on the kernel build system itself. -These people need to know about all aspects of the kernel Makefiles. - -This document is aimed towards normal developers and arch developers. - - -=== 3 The kbuild files - -Most Makefiles within the kernel are kbuild Makefiles that use the -kbuild infrastructure. This chapter introduces the syntax used in the -kbuild makefiles. -The preferred name for the kbuild files are 'Makefile' but 'Kbuild' can -be used and if both a 'Makefile' and a 'Kbuild' file exists, then the 'Kbuild' -file will be used. - -Section 3.1 "Goal definitions" is a quick intro, further chapters provide -more details, with real examples. - ---- 3.1 Goal definitions - - Goal definitions are the main part (heart) of the kbuild Makefile. - These lines define the files to be built, any special compilation - options, and any subdirectories to be entered recursively. - - The most simple kbuild makefile contains one line: - - Example: - obj-y += foo.o - - This tells kbuild that there is one object in that directory, named - foo.o. foo.o will be built from foo.c or foo.S. - - If foo.o shall be built as a module, the variable obj-m is used. - Therefore the following pattern is often used: - - Example: - obj-$(CONFIG_FOO) += foo.o - - $(CONFIG_FOO) evaluates to either y (for built-in) or m (for module). - If CONFIG_FOO is neither y nor m, then the file will not be compiled - nor linked. - ---- 3.2 Built-in object goals - obj-y - - The kbuild Makefile specifies object files for vmlinux - in the $(obj-y) lists. These lists depend on the kernel - configuration. - - Kbuild compiles all the $(obj-y) files. It then calls - "$(AR) rcSTP" to merge these files into one built-in.a file. - This is a thin archive without a symbol table. It will be later - linked into vmlinux by scripts/link-vmlinux.sh - - The order of files in $(obj-y) is significant. Duplicates in - the lists are allowed: the first instance will be linked into - built-in.a and succeeding instances will be ignored. - - Link order is significant, because certain functions - (module_init() / __initcall) will be called during boot in the - order they appear. So keep in mind that changing the link - order may e.g. change the order in which your SCSI - controllers are detected, and thus your disks are renumbered. - - Example: - #drivers/isdn/i4l/Makefile - # Makefile for the kernel ISDN subsystem and device drivers. - # Each configuration option enables a list of files. - obj-$(CONFIG_ISDN_I4L) += isdn.o - obj-$(CONFIG_ISDN_PPP_BSDCOMP) += isdn_bsdcomp.o - ---- 3.3 Loadable module goals - obj-m - - $(obj-m) specifies object files which are built as loadable - kernel modules. - - A module may be built from one source file or several source - files. In the case of one source file, the kbuild makefile - simply adds the file to $(obj-m). - - Example: - #drivers/isdn/i4l/Makefile - obj-$(CONFIG_ISDN_PPP_BSDCOMP) += isdn_bsdcomp.o - - Note: In this example $(CONFIG_ISDN_PPP_BSDCOMP) evaluates to 'm' - - If a kernel module is built from several source files, you specify - that you want to build a module in the same way as above; however, - kbuild needs to know which object files you want to build your - module from, so you have to tell it by setting a $(-y) - variable. - - Example: - #drivers/isdn/i4l/Makefile - obj-$(CONFIG_ISDN_I4L) += isdn.o - isdn-y := isdn_net_lib.o isdn_v110.o isdn_common.o - - In this example, the module name will be isdn.o. Kbuild will - compile the objects listed in $(isdn-y) and then run - "$(LD) -r" on the list of these files to generate isdn.o. - - Due to kbuild recognizing $(-y) for composite objects, - you can use the value of a CONFIG_ symbol to optionally include an - object file as part of a composite object. - - Example: - #fs/ext2/Makefile - obj-$(CONFIG_EXT2_FS) += ext2.o - ext2-y := balloc.o dir.o file.o ialloc.o inode.o ioctl.o \ - namei.o super.o symlink.o - ext2-$(CONFIG_EXT2_FS_XATTR) += xattr.o xattr_user.o \ - xattr_trusted.o - - In this example, xattr.o, xattr_user.o and xattr_trusted.o are only - part of the composite object ext2.o if $(CONFIG_EXT2_FS_XATTR) - evaluates to 'y'. - - Note: Of course, when you are building objects into the kernel, - the syntax above will also work. So, if you have CONFIG_EXT2_FS=y, - kbuild will build an ext2.o file for you out of the individual - parts and then link this into built-in.a, as you would expect. - ---- 3.4 Objects which export symbols - - No special notation is required in the makefiles for - modules exporting symbols. - ---- 3.5 Library file goals - lib-y - - Objects listed with obj-* are used for modules, or - combined in a built-in.a for that specific directory. - There is also the possibility to list objects that will - be included in a library, lib.a. - All objects listed with lib-y are combined in a single - library for that directory. - Objects that are listed in obj-y and additionally listed in - lib-y will not be included in the library, since they will - be accessible anyway. - For consistency, objects listed in lib-m will be included in lib.a. - - Note that the same kbuild makefile may list files to be built-in - and to be part of a library. Therefore the same directory - may contain both a built-in.a and a lib.a file. - - Example: - #arch/x86/lib/Makefile - lib-y := delay.o - - This will create a library lib.a based on delay.o. For kbuild to - actually recognize that there is a lib.a being built, the directory - shall be listed in libs-y. - See also "6.4 List directories to visit when descending". - - Use of lib-y is normally restricted to lib/ and arch/*/lib. - ---- 3.6 Descending down in directories - - A Makefile is only responsible for building objects in its own - directory. Files in subdirectories should be taken care of by - Makefiles in these subdirs. The build system will automatically - invoke make recursively in subdirectories, provided you let it know of - them. - - To do so, obj-y and obj-m are used. - ext2 lives in a separate directory, and the Makefile present in fs/ - tells kbuild to descend down using the following assignment. - - Example: - #fs/Makefile - obj-$(CONFIG_EXT2_FS) += ext2/ - - If CONFIG_EXT2_FS is set to either 'y' (built-in) or 'm' (modular) - the corresponding obj- variable will be set, and kbuild will descend - down in the ext2 directory. - Kbuild only uses this information to decide that it needs to visit - the directory, it is the Makefile in the subdirectory that - specifies what is modular and what is built-in. - - It is good practice to use a CONFIG_ variable when assigning directory - names. This allows kbuild to totally skip the directory if the - corresponding CONFIG_ option is neither 'y' nor 'm'. - ---- 3.7 Compilation flags - - ccflags-y, asflags-y and ldflags-y - These three flags apply only to the kbuild makefile in which they - are assigned. They are used for all the normal cc, as and ld - invocations happening during a recursive build. - Note: Flags with the same behaviour were previously named: - EXTRA_CFLAGS, EXTRA_AFLAGS and EXTRA_LDFLAGS. - They are still supported but their usage is deprecated. - - ccflags-y specifies options for compiling with $(CC). - - Example: - # drivers/acpi/acpica/Makefile - ccflags-y := -Os -D_LINUX -DBUILDING_ACPICA - ccflags-$(CONFIG_ACPI_DEBUG) += -DACPI_DEBUG_OUTPUT - - This variable is necessary because the top Makefile owns the - variable $(KBUILD_CFLAGS) and uses it for compilation flags for the - entire tree. - - asflags-y specifies options for assembling with $(AS). - - Example: - #arch/sparc/kernel/Makefile - asflags-y := -ansi - - ldflags-y specifies options for linking with $(LD). - - Example: - #arch/cris/boot/compressed/Makefile - ldflags-y += -T $(srctree)/$(src)/decompress_$(arch-y).lds - - subdir-ccflags-y, subdir-asflags-y - The two flags listed above are similar to ccflags-y and asflags-y. - The difference is that the subdir- variants have effect for the kbuild - file where they are present and all subdirectories. - Options specified using subdir-* are added to the commandline before - the options specified using the non-subdir variants. - - Example: - subdir-ccflags-y := -Werror - - CFLAGS_$@, AFLAGS_$@ - - CFLAGS_$@ and AFLAGS_$@ only apply to commands in current - kbuild makefile. - - $(CFLAGS_$@) specifies per-file options for $(CC). The $@ - part has a literal value which specifies the file that it is for. - - Example: - # drivers/scsi/Makefile - CFLAGS_aha152x.o = -DAHA152X_STAT -DAUTOCONF - CFLAGS_gdth.o = # -DDEBUG_GDTH=2 -D__SERIAL__ -D__COM2__ \ - -DGDTH_STATISTICS - - These two lines specify compilation flags for aha152x.o and gdth.o. - - $(AFLAGS_$@) is a similar feature for source files in assembly - languages. - - Example: - # arch/arm/kernel/Makefile - AFLAGS_head.o := -DTEXT_OFFSET=$(TEXT_OFFSET) - AFLAGS_crunch-bits.o := -Wa,-mcpu=ep9312 - AFLAGS_iwmmxt.o := -Wa,-mcpu=iwmmxt - - ---- 3.9 Dependency tracking - - Kbuild tracks dependencies on the following: - 1) All prerequisite files (both *.c and *.h) - 2) CONFIG_ options used in all prerequisite files - 3) Command-line used to compile target - - Thus, if you change an option to $(CC) all affected files will - be re-compiled. - ---- 3.10 Special Rules - - Special rules are used when the kbuild infrastructure does - not provide the required support. A typical example is - header files generated during the build process. - Another example are the architecture-specific Makefiles which - need special rules to prepare boot images etc. - - Special rules are written as normal Make rules. - Kbuild is not executing in the directory where the Makefile is - located, so all special rules shall provide a relative - path to prerequisite files and target files. - - Two variables are used when defining special rules: - - $(src) - $(src) is a relative path which points to the directory - where the Makefile is located. Always use $(src) when - referring to files located in the src tree. - - $(obj) - $(obj) is a relative path which points to the directory - where the target is saved. Always use $(obj) when - referring to generated files. - - Example: - #drivers/scsi/Makefile - $(obj)/53c8xx_d.h: $(src)/53c7,8xx.scr $(src)/script_asm.pl - $(CPP) -DCHIP=810 - < $< | ... $(src)/script_asm.pl - - This is a special rule, following the normal syntax - required by make. - The target file depends on two prerequisite files. References - to the target file are prefixed with $(obj), references - to prerequisites are referenced with $(src) (because they are not - generated files). - - $(kecho) - echoing information to user in a rule is often a good practice - but when execution "make -s" one does not expect to see any output - except for warnings/errors. - To support this kbuild defines $(kecho) which will echo out the - text following $(kecho) to stdout except if "make -s" is used. - - Example: - #arch/blackfin/boot/Makefile - $(obj)/vmImage: $(obj)/vmlinux.gz - $(call if_changed,uimage) - @$(kecho) 'Kernel: $@ is ready' - - ---- 3.11 $(CC) support functions - - The kernel may be built with several different versions of - $(CC), each supporting a unique set of features and options. - kbuild provides basic support to check for valid options for $(CC). - $(CC) is usually the gcc compiler, but other alternatives are - available. - - as-option - as-option is used to check if $(CC) -- when used to compile - assembler (*.S) files -- supports the given option. An optional - second option may be specified if the first option is not supported. - - Example: - #arch/sh/Makefile - cflags-y += $(call as-option,-Wa$(comma)-isa=$(isa-y),) - - In the above example, cflags-y will be assigned the option - -Wa$(comma)-isa=$(isa-y) if it is supported by $(CC). - The second argument is optional, and if supplied will be used - if first argument is not supported. - - as-instr - as-instr checks if the assembler reports a specific instruction - and then outputs either option1 or option2 - C escapes are supported in the test instruction - Note: as-instr-option uses KBUILD_AFLAGS for $(AS) options - - cc-option - cc-option is used to check if $(CC) supports a given option, and if - not supported to use an optional second option. - - Example: - #arch/x86/Makefile - cflags-y += $(call cc-option,-march=pentium-mmx,-march=i586) - - In the above example, cflags-y will be assigned the option - -march=pentium-mmx if supported by $(CC), otherwise -march=i586. - The second argument to cc-option is optional, and if omitted, - cflags-y will be assigned no value if first option is not supported. - Note: cc-option uses KBUILD_CFLAGS for $(CC) options - - cc-option-yn - cc-option-yn is used to check if gcc supports a given option - and return 'y' if supported, otherwise 'n'. - - Example: - #arch/ppc/Makefile - biarch := $(call cc-option-yn, -m32) - aflags-$(biarch) += -a32 - cflags-$(biarch) += -m32 - - In the above example, $(biarch) is set to y if $(CC) supports the -m32 - option. When $(biarch) equals 'y', the expanded variables $(aflags-y) - and $(cflags-y) will be assigned the values -a32 and -m32, - respectively. - Note: cc-option-yn uses KBUILD_CFLAGS for $(CC) options - - cc-disable-warning - cc-disable-warning checks if gcc supports a given warning and returns - the commandline switch to disable it. This special function is needed, - because gcc 4.4 and later accept any unknown -Wno-* option and only - warn about it if there is another warning in the source file. - - Example: - KBUILD_CFLAGS += $(call cc-disable-warning, unused-but-set-variable) - - In the above example, -Wno-unused-but-set-variable will be added to - KBUILD_CFLAGS only if gcc really accepts it. - - cc-ifversion - cc-ifversion tests the version of $(CC) and equals the fourth parameter - if version expression is true, or the fifth (if given) if the version - expression is false. - - Example: - #fs/reiserfs/Makefile - ccflags-y := $(call cc-ifversion, -lt, 0402, -O1) - - In this example, ccflags-y will be assigned the value -O1 if the - $(CC) version is less than 4.2. - cc-ifversion takes all the shell operators: - -eq, -ne, -lt, -le, -gt, and -ge - The third parameter may be a text as in this example, but it may also - be an expanded variable or a macro. - - cc-cross-prefix - cc-cross-prefix is used to check if there exists a $(CC) in path with - one of the listed prefixes. The first prefix where there exist a - prefix$(CC) in the PATH is returned - and if no prefix$(CC) is found - then nothing is returned. - Additional prefixes are separated by a single space in the - call of cc-cross-prefix. - This functionality is useful for architecture Makefiles that try - to set CROSS_COMPILE to well-known values but may have several - values to select between. - It is recommended only to try to set CROSS_COMPILE if it is a cross - build (host arch is different from target arch). And if CROSS_COMPILE - is already set then leave it with the old value. - - Example: - #arch/m68k/Makefile - ifneq ($(SUBARCH),$(ARCH)) - ifeq ($(CROSS_COMPILE),) - CROSS_COMPILE := $(call cc-cross-prefix, m68k-linux-gnu-) - endif - endif - ---- 3.12 $(LD) support functions - - ld-option - ld-option is used to check if $(LD) supports the supplied option. - ld-option takes two options as arguments. - The second argument is an optional option that can be used if the - first option is not supported by $(LD). - - Example: - #Makefile - LDFLAGS_vmlinux += $(call ld-option, -X) - - -=== 4 Host Program support - -Kbuild supports building executables on the host for use during the -compilation stage. -Two steps are required in order to use a host executable. - -The first step is to tell kbuild that a host program exists. This is -done utilising the variable hostprogs-y. - -The second step is to add an explicit dependency to the executable. -This can be done in two ways. Either add the dependency in a rule, -or utilise the variable $(always). -Both possibilities are described in the following. - ---- 4.1 Simple Host Program - - In some cases there is a need to compile and run a program on the - computer where the build is running. - The following line tells kbuild that the program bin2hex shall be - built on the build host. - - Example: - hostprogs-y := bin2hex - - Kbuild assumes in the above example that bin2hex is made from a single - c-source file named bin2hex.c located in the same directory as - the Makefile. - ---- 4.2 Composite Host Programs - - Host programs can be made up based on composite objects. - The syntax used to define composite objects for host programs is - similar to the syntax used for kernel objects. - $(-objs) lists all objects used to link the final - executable. - - Example: - #scripts/lxdialog/Makefile - hostprogs-y := lxdialog - lxdialog-objs := checklist.o lxdialog.o - - Objects with extension .o are compiled from the corresponding .c - files. In the above example, checklist.c is compiled to checklist.o - and lxdialog.c is compiled to lxdialog.o. - Finally, the two .o files are linked to the executable, lxdialog. - Note: The syntax -y is not permitted for host-programs. - ---- 4.3 Using C++ for host programs - - kbuild offers support for host programs written in C++. This was - introduced solely to support kconfig, and is not recommended - for general use. - - Example: - #scripts/kconfig/Makefile - hostprogs-y := qconf - qconf-cxxobjs := qconf.o - - In the example above the executable is composed of the C++ file - qconf.cc - identified by $(qconf-cxxobjs). - - If qconf is composed of a mixture of .c and .cc files, then an - additional line can be used to identify this. - - Example: - #scripts/kconfig/Makefile - hostprogs-y := qconf - qconf-cxxobjs := qconf.o - qconf-objs := check.o - ---- 4.4 Controlling compiler options for host programs - - When compiling host programs, it is possible to set specific flags. - The programs will always be compiled utilising $(HOSTCC) passed - the options specified in $(KBUILD_HOSTCFLAGS). - To set flags that will take effect for all host programs created - in that Makefile, use the variable HOST_EXTRACFLAGS. - - Example: - #scripts/lxdialog/Makefile - HOST_EXTRACFLAGS += -I/usr/include/ncurses - - To set specific flags for a single file the following construction - is used: - - Example: - #arch/ppc64/boot/Makefile - HOSTCFLAGS_piggyback.o := -DKERNELBASE=$(KERNELBASE) - - It is also possible to specify additional options to the linker. - - Example: - #scripts/kconfig/Makefile - HOSTLDLIBS_qconf := -L$(QTDIR)/lib - - When linking qconf, it will be passed the extra option - "-L$(QTDIR)/lib". - ---- 4.5 When host programs are actually built - - Kbuild will only build host-programs when they are referenced - as a prerequisite. - This is possible in two ways: - - (1) List the prerequisite explicitly in a special rule. - - Example: - #drivers/pci/Makefile - hostprogs-y := gen-devlist - $(obj)/devlist.h: $(src)/pci.ids $(obj)/gen-devlist - ( cd $(obj); ./gen-devlist ) < $< - - The target $(obj)/devlist.h will not be built before - $(obj)/gen-devlist is updated. Note that references to - the host programs in special rules must be prefixed with $(obj). - - (2) Use $(always) - When there is no suitable special rule, and the host program - shall be built when a makefile is entered, the $(always) - variable shall be used. - - Example: - #scripts/lxdialog/Makefile - hostprogs-y := lxdialog - always := $(hostprogs-y) - - This will tell kbuild to build lxdialog even if not referenced in - any rule. - ---- 4.6 Using hostprogs-$(CONFIG_FOO) - - A typical pattern in a Kbuild file looks like this: - - Example: - #scripts/Makefile - hostprogs-$(CONFIG_KALLSYMS) += kallsyms - - Kbuild knows about both 'y' for built-in and 'm' for module. - So if a config symbol evaluates to 'm', kbuild will still build - the binary. In other words, Kbuild handles hostprogs-m exactly - like hostprogs-y. But only hostprogs-y is recommended to be used - when no CONFIG symbols are involved. - -=== 5 Kbuild clean infrastructure - -"make clean" deletes most generated files in the obj tree where the kernel -is compiled. This includes generated files such as host programs. -Kbuild knows targets listed in $(hostprogs-y), $(hostprogs-m), $(always), -$(extra-y) and $(targets). They are all deleted during "make clean". -Files matching the patterns "*.[oas]", "*.ko", plus some additional files -generated by kbuild are deleted all over the kernel src tree when -"make clean" is executed. - -Additional files can be specified in kbuild makefiles by use of $(clean-files). - - Example: - #lib/Makefile - clean-files := crc32table.h - -When executing "make clean", the file "crc32table.h" will be deleted. -Kbuild will assume files to be in the same relative directory as the -Makefile, except if prefixed with $(objtree). - -To delete a directory hierarchy use: - - Example: - #scripts/package/Makefile - clean-dirs := $(objtree)/debian/ - -This will delete the directory debian in the toplevel directory, including all -subdirectories. - -To exclude certain files from make clean, use the $(no-clean-files) variable. -This is only a special case used in the top level Kbuild file: - - Example: - #Kbuild - no-clean-files := $(bounds-file) $(offsets-file) - -Usually kbuild descends down in subdirectories due to "obj-* := dir/", -but in the architecture makefiles where the kbuild infrastructure -is not sufficient this sometimes needs to be explicit. - - Example: - #arch/x86/boot/Makefile - subdir- := compressed/ - -The above assignment instructs kbuild to descend down in the -directory compressed/ when "make clean" is executed. - -To support the clean infrastructure in the Makefiles that build the -final bootimage there is an optional target named archclean: - - Example: - #arch/x86/Makefile - archclean: - $(Q)$(MAKE) $(clean)=arch/x86/boot - -When "make clean" is executed, make will descend down in arch/x86/boot, -and clean as usual. The Makefile located in arch/x86/boot/ may use -the subdir- trick to descend further down. - -Note 1: arch/$(ARCH)/Makefile cannot use "subdir-", because that file is -included in the top level makefile, and the kbuild infrastructure -is not operational at that point. - -Note 2: All directories listed in core-y, libs-y, drivers-y and net-y will -be visited during "make clean". - -=== 6 Architecture Makefiles - -The top level Makefile sets up the environment and does the preparation, -before starting to descend down in the individual directories. -The top level makefile contains the generic part, whereas -arch/$(ARCH)/Makefile contains what is required to set up kbuild -for said architecture. -To do so, arch/$(ARCH)/Makefile sets up a number of variables and defines -a few targets. - -When kbuild executes, the following steps are followed (roughly): -1) Configuration of the kernel => produce .config -2) Store kernel version in include/linux/version.h -3) Updating all other prerequisites to the target prepare: - - Additional prerequisites are specified in arch/$(ARCH)/Makefile -4) Recursively descend down in all directories listed in - init-* core* drivers-* net-* libs-* and build all targets. - - The values of the above variables are expanded in arch/$(ARCH)/Makefile. -5) All object files are then linked and the resulting file vmlinux is - located at the root of the obj tree. - The very first objects linked are listed in head-y, assigned by - arch/$(ARCH)/Makefile. -6) Finally, the architecture-specific part does any required post processing - and builds the final bootimage. - - This includes building boot records - - Preparing initrd images and the like - - ---- 6.1 Set variables to tweak the build to the architecture - - LDFLAGS Generic $(LD) options - - Flags used for all invocations of the linker. - Often specifying the emulation is sufficient. - - Example: - #arch/s390/Makefile - LDFLAGS := -m elf_s390 - Note: ldflags-y can be used to further customise - the flags used. See chapter 3.7. - - LDFLAGS_vmlinux Options for $(LD) when linking vmlinux - - LDFLAGS_vmlinux is used to specify additional flags to pass to - the linker when linking the final vmlinux image. - LDFLAGS_vmlinux uses the LDFLAGS_$@ support. - - Example: - #arch/x86/Makefile - LDFLAGS_vmlinux := -e stext - - OBJCOPYFLAGS objcopy flags - - When $(call if_changed,objcopy) is used to translate a .o file, - the flags specified in OBJCOPYFLAGS will be used. - $(call if_changed,objcopy) is often used to generate raw binaries on - vmlinux. - - Example: - #arch/s390/Makefile - OBJCOPYFLAGS := -O binary - - #arch/s390/boot/Makefile - $(obj)/image: vmlinux FORCE - $(call if_changed,objcopy) - - In this example, the binary $(obj)/image is a binary version of - vmlinux. The usage of $(call if_changed,xxx) will be described later. - - KBUILD_AFLAGS $(AS) assembler flags - - Default value - see top level Makefile - Append or modify as required per architecture. - - Example: - #arch/sparc64/Makefile - KBUILD_AFLAGS += -m64 -mcpu=ultrasparc - - KBUILD_CFLAGS $(CC) compiler flags - - Default value - see top level Makefile - Append or modify as required per architecture. - - Often, the KBUILD_CFLAGS variable depends on the configuration. - - Example: - #arch/x86/boot/compressed/Makefile - cflags-$(CONFIG_X86_32) := -march=i386 - cflags-$(CONFIG_X86_64) := -mcmodel=small - KBUILD_CFLAGS += $(cflags-y) - - Many arch Makefiles dynamically run the target C compiler to - probe supported options: - - #arch/x86/Makefile - - ... - cflags-$(CONFIG_MPENTIUMII) += $(call cc-option,\ - -march=pentium2,-march=i686) - ... - # Disable unit-at-a-time mode ... - KBUILD_CFLAGS += $(call cc-option,-fno-unit-at-a-time) - ... - - - The first example utilises the trick that a config option expands - to 'y' when selected. - - KBUILD_AFLAGS_KERNEL $(AS) options specific for built-in - - $(KBUILD_AFLAGS_KERNEL) contains extra C compiler flags used to compile - resident kernel code. - - KBUILD_AFLAGS_MODULE Options for $(AS) when building modules - - $(KBUILD_AFLAGS_MODULE) is used to add arch-specific options that - are used for $(AS). - From commandline AFLAGS_MODULE shall be used (see kbuild.txt). - - KBUILD_CFLAGS_KERNEL $(CC) options specific for built-in - - $(KBUILD_CFLAGS_KERNEL) contains extra C compiler flags used to compile - resident kernel code. - - KBUILD_CFLAGS_MODULE Options for $(CC) when building modules - - $(KBUILD_CFLAGS_MODULE) is used to add arch-specific options that - are used for $(CC). - From commandline CFLAGS_MODULE shall be used (see kbuild.txt). - - KBUILD_LDFLAGS_MODULE Options for $(LD) when linking modules - - $(KBUILD_LDFLAGS_MODULE) is used to add arch-specific options - used when linking modules. This is often a linker script. - From commandline LDFLAGS_MODULE shall be used (see kbuild.txt). - - KBUILD_ARFLAGS Options for $(AR) when creating archives - - $(KBUILD_ARFLAGS) set by the top level Makefile to "D" (deterministic - mode) if this option is supported by $(AR). - - ARCH_CPPFLAGS, ARCH_AFLAGS, ARCH_CFLAGS Overrides the kbuild defaults - - These variables are appended to the KBUILD_CPPFLAGS, - KBUILD_AFLAGS, and KBUILD_CFLAGS, respectively, after the - top-level Makefile has set any other flags. This provides a - means for an architecture to override the defaults. - - ---- 6.2 Add prerequisites to archheaders: - - The archheaders: rule is used to generate header files that - may be installed into user space by "make header_install" or - "make headers_install_all". In order to support - "make headers_install_all", this target has to be able to run - on an unconfigured tree, or a tree configured for another - architecture. - - It is run before "make archprepare" when run on the - architecture itself. - - ---- 6.3 Add prerequisites to archprepare: - - The archprepare: rule is used to list prerequisites that need to be - built before starting to descend down in the subdirectories. - This is usually used for header files containing assembler constants. - - Example: - #arch/arm/Makefile - archprepare: maketools - - In this example, the file target maketools will be processed - before descending down in the subdirectories. - See also chapter XXX-TODO that describe how kbuild supports - generating offset header files. - - ---- 6.4 List directories to visit when descending - - An arch Makefile cooperates with the top Makefile to define variables - which specify how to build the vmlinux file. Note that there is no - corresponding arch-specific section for modules; the module-building - machinery is all architecture-independent. - - - head-y, init-y, core-y, libs-y, drivers-y, net-y - - $(head-y) lists objects to be linked first in vmlinux. - $(libs-y) lists directories where a lib.a archive can be located. - The rest list directories where a built-in.a object file can be - located. - - $(init-y) objects will be located after $(head-y). - Then the rest follows in this order: - $(core-y), $(libs-y), $(drivers-y) and $(net-y). - - The top level Makefile defines values for all generic directories, - and arch/$(ARCH)/Makefile only adds architecture-specific directories. - - Example: - #arch/sparc64/Makefile - core-y += arch/sparc64/kernel/ - libs-y += arch/sparc64/prom/ arch/sparc64/lib/ - drivers-$(CONFIG_OPROFILE) += arch/sparc64/oprofile/ - - ---- 6.5 Architecture-specific boot images - - An arch Makefile specifies goals that take the vmlinux file, compress - it, wrap it in bootstrapping code, and copy the resulting files - somewhere. This includes various kinds of installation commands. - The actual goals are not standardized across architectures. - - It is common to locate any additional processing in a boot/ - directory below arch/$(ARCH)/. - - Kbuild does not provide any smart way to support building a - target specified in boot/. Therefore arch/$(ARCH)/Makefile shall - call make manually to build a target in boot/. - - The recommended approach is to include shortcuts in - arch/$(ARCH)/Makefile, and use the full path when calling down - into the arch/$(ARCH)/boot/Makefile. - - Example: - #arch/x86/Makefile - boot := arch/x86/boot - bzImage: vmlinux - $(Q)$(MAKE) $(build)=$(boot) $(boot)/$@ - - "$(Q)$(MAKE) $(build)=" is the recommended way to invoke - make in a subdirectory. - - There are no rules for naming architecture-specific targets, - but executing "make help" will list all relevant targets. - To support this, $(archhelp) must be defined. - - Example: - #arch/x86/Makefile - define archhelp - echo '* bzImage - Image (arch/$(ARCH)/boot/bzImage)' - endif - - When make is executed without arguments, the first goal encountered - will be built. In the top level Makefile the first goal present - is all:. - An architecture shall always, per default, build a bootable image. - In "make help", the default goal is highlighted with a '*'. - Add a new prerequisite to all: to select a default goal different - from vmlinux. - - Example: - #arch/x86/Makefile - all: bzImage - - When "make" is executed without arguments, bzImage will be built. - ---- 6.6 Building non-kbuild targets - - extra-y - - extra-y specifies additional targets created in the current - directory, in addition to any targets specified by obj-*. - - Listing all targets in extra-y is required for two purposes: - 1) Enable kbuild to check changes in command lines - - When $(call if_changed,xxx) is used - 2) kbuild knows what files to delete during "make clean" - - Example: - #arch/x86/kernel/Makefile - extra-y := head.o init_task.o - - In this example, extra-y is used to list object files that - shall be built, but shall not be linked as part of built-in.a. - - ---- 6.7 Commands useful for building a boot image - - Kbuild provides a few macros that are useful when building a - boot image. - - if_changed - - if_changed is the infrastructure used for the following commands. - - Usage: - target: source(s) FORCE - $(call if_changed,ld/objcopy/gzip/...) - - When the rule is evaluated, it is checked to see if any files - need an update, or the command line has changed since the last - invocation. The latter will force a rebuild if any options - to the executable have changed. - Any target that utilises if_changed must be listed in $(targets), - otherwise the command line check will fail, and the target will - always be built. - Assignments to $(targets) are without $(obj)/ prefix. - if_changed may be used in conjunction with custom commands as - defined in 6.8 "Custom kbuild commands". - - Note: It is a typical mistake to forget the FORCE prerequisite. - Another common pitfall is that whitespace is sometimes - significant; for instance, the below will fail (note the extra space - after the comma): - target: source(s) FORCE - #WRONG!# $(call if_changed, ld/objcopy/gzip/...) - - Note: if_changed should not be used more than once per target. - It stores the executed command in a corresponding .cmd - file and multiple calls would result in overwrites and - unwanted results when the target is up to date and only the - tests on changed commands trigger execution of commands. - - ld - Link target. Often, LDFLAGS_$@ is used to set specific options to ld. - - Example: - #arch/x86/boot/Makefile - LDFLAGS_bootsect := -Ttext 0x0 -s --oformat binary - LDFLAGS_setup := -Ttext 0x0 -s --oformat binary -e begtext - - targets += setup setup.o bootsect bootsect.o - $(obj)/setup $(obj)/bootsect: %: %.o FORCE - $(call if_changed,ld) - - In this example, there are two possible targets, requiring different - options to the linker. The linker options are specified using the - LDFLAGS_$@ syntax - one for each potential target. - $(targets) are assigned all potential targets, by which kbuild knows - the targets and will: - 1) check for commandline changes - 2) delete target during make clean - - The ": %: %.o" part of the prerequisite is a shorthand that - frees us from listing the setup.o and bootsect.o files. - Note: It is a common mistake to forget the "targets :=" assignment, - resulting in the target file being recompiled for no - obvious reason. - - objcopy - Copy binary. Uses OBJCOPYFLAGS usually specified in - arch/$(ARCH)/Makefile. - OBJCOPYFLAGS_$@ may be used to set additional options. - - gzip - Compress target. Use maximum compression to compress target. - - Example: - #arch/x86/boot/compressed/Makefile - $(obj)/vmlinux.bin.gz: $(vmlinux.bin.all-y) FORCE - $(call if_changed,gzip) - - dtc - Create flattened device tree blob object suitable for linking - into vmlinux. Device tree blobs linked into vmlinux are placed - in an init section in the image. Platform code *must* copy the - blob to non-init memory prior to calling unflatten_device_tree(). - - To use this command, simply add *.dtb into obj-y or targets, or make - some other target depend on %.dtb - - A central rule exists to create $(obj)/%.dtb from $(src)/%.dts; - architecture Makefiles do no need to explicitly write out that rule. - - Example: - targets += $(dtb-y) - DTC_FLAGS ?= -p 1024 - ---- 6.8 Custom kbuild commands - - When kbuild is executing with KBUILD_VERBOSE=0, then only a shorthand - of a command is normally displayed. - To enable this behaviour for custom commands kbuild requires - two variables to be set: - quiet_cmd_ - what shall be echoed - cmd_ - the command to execute - - Example: - # - quiet_cmd_image = BUILD $@ - cmd_image = $(obj)/tools/build $(BUILDFLAGS) \ - $(obj)/vmlinux.bin > $@ - - targets += bzImage - $(obj)/bzImage: $(obj)/vmlinux.bin $(obj)/tools/build FORCE - $(call if_changed,image) - @echo 'Kernel: $@ is ready' - - When updating the $(obj)/bzImage target, the line - - BUILD arch/x86/boot/bzImage - - will be displayed with "make KBUILD_VERBOSE=0". - - ---- 6.9 Preprocessing linker scripts - - When the vmlinux image is built, the linker script - arch/$(ARCH)/kernel/vmlinux.lds is used. - The script is a preprocessed variant of the file vmlinux.lds.S - located in the same directory. - kbuild knows .lds files and includes a rule *lds.S -> *lds. - - Example: - #arch/x86/kernel/Makefile - always := vmlinux.lds - - #Makefile - export CPPFLAGS_vmlinux.lds += -P -C -U$(ARCH) - - The assignment to $(always) is used to tell kbuild to build the - target vmlinux.lds. - The assignment to $(CPPFLAGS_vmlinux.lds) tells kbuild to use the - specified options when building the target vmlinux.lds. - - When building the *.lds target, kbuild uses the variables: - KBUILD_CPPFLAGS : Set in top-level Makefile - cppflags-y : May be set in the kbuild makefile - CPPFLAGS_$(@F) : Target-specific flags. - Note that the full filename is used in this - assignment. - - The kbuild infrastructure for *lds files is used in several - architecture-specific files. - ---- 6.10 Generic header files - - The directory include/asm-generic contains the header files - that may be shared between individual architectures. - The recommended approach how to use a generic header file is - to list the file in the Kbuild file. - See "7.2 generic-y" for further info on syntax etc. - ---- 6.11 Post-link pass - - If the file arch/xxx/Makefile.postlink exists, this makefile - will be invoked for post-link objects (vmlinux and modules.ko) - for architectures to run post-link passes on. Must also handle - the clean target. - - This pass runs after kallsyms generation. If the architecture - needs to modify symbol locations, rather than manipulate the - kallsyms, it may be easier to add another postlink target for - .tmp_vmlinux? targets to be called from link-vmlinux.sh. - - For example, powerpc uses this to check relocation sanity of - the linked vmlinux file. - -=== 7 Kbuild syntax for exported headers - -The kernel includes a set of headers that is exported to userspace. -Many headers can be exported as-is but other headers require a -minimal pre-processing before they are ready for user-space. -The pre-processing does: -- drop kernel-specific annotations -- drop include of compiler.h -- drop all sections that are kernel internal (guarded by ifdef __KERNEL__) - -All headers under include/uapi/, include/generated/uapi/, -arch//include/uapi/ and arch//include/generated/uapi/ -are exported. - -A Kbuild file may be defined under arch//include/uapi/asm/ and -arch//include/asm/ to list asm files coming from asm-generic. -See subsequent chapter for the syntax of the Kbuild file. - ---- 7.1 no-export-headers - - no-export-headers is essentially used by include/uapi/linux/Kbuild to - avoid exporting specific headers (e.g. kvm.h) on architectures that do - not support it. It should be avoided as much as possible. - ---- 7.2 generic-y - - If an architecture uses a verbatim copy of a header from - include/asm-generic then this is listed in the file - arch/$(ARCH)/include/asm/Kbuild like this: - - Example: - #arch/x86/include/asm/Kbuild - generic-y += termios.h - generic-y += rtc.h - - During the prepare phase of the build a wrapper include - file is generated in the directory: - - arch/$(ARCH)/include/generated/asm - - When a header is exported where the architecture uses - the generic header a similar wrapper is generated as part - of the set of exported headers in the directory: - - usr/include/asm - - The generated wrapper will in both cases look like the following: - - Example: termios.h - #include - ---- 7.3 generated-y - - If an architecture generates other header files alongside generic-y - wrappers, generated-y specifies them. - - This prevents them being treated as stale asm-generic wrappers and - removed. - - Example: - #arch/x86/include/asm/Kbuild - generated-y += syscalls_32.h - ---- 7.4 mandatory-y - - mandatory-y is essentially used by include/(uapi/)asm-generic/Kbuild - to define the minimum set of ASM headers that all architectures must have. - - This works like optional generic-y. If a mandatory header is missing - in arch/$(ARCH)/include/(uapi/)/asm, Kbuild will automatically generate - a wrapper of the asm-generic one. - - The convention is to list one subdir per line and - preferably in alphabetic order. - -=== 8 Kbuild Variables - -The top Makefile exports the following variables: - - VERSION, PATCHLEVEL, SUBLEVEL, EXTRAVERSION - - These variables define the current kernel version. A few arch - Makefiles actually use these values directly; they should use - $(KERNELRELEASE) instead. - - $(VERSION), $(PATCHLEVEL), and $(SUBLEVEL) define the basic - three-part version number, such as "2", "4", and "0". These three - values are always numeric. - - $(EXTRAVERSION) defines an even tinier sublevel for pre-patches - or additional patches. It is usually some non-numeric string - such as "-pre4", and is often blank. - - KERNELRELEASE - - $(KERNELRELEASE) is a single string such as "2.4.0-pre4", suitable - for constructing installation directory names or showing in - version strings. Some arch Makefiles use it for this purpose. - - ARCH - - This variable defines the target architecture, such as "i386", - "arm", or "sparc". Some kbuild Makefiles test $(ARCH) to - determine which files to compile. - - By default, the top Makefile sets $(ARCH) to be the same as the - host system architecture. For a cross build, a user may - override the value of $(ARCH) on the command line: - - make ARCH=m68k ... - - - INSTALL_PATH - - This variable defines a place for the arch Makefiles to install - the resident kernel image and System.map file. - Use this for architecture-specific install targets. - - INSTALL_MOD_PATH, MODLIB - - $(INSTALL_MOD_PATH) specifies a prefix to $(MODLIB) for module - installation. This variable is not defined in the Makefile but - may be passed in by the user if desired. - - $(MODLIB) specifies the directory for module installation. - The top Makefile defines $(MODLIB) to - $(INSTALL_MOD_PATH)/lib/modules/$(KERNELRELEASE). The user may - override this value on the command line if desired. - - INSTALL_MOD_STRIP - - If this variable is specified, it will cause modules to be stripped - after they are installed. If INSTALL_MOD_STRIP is '1', then the - default option --strip-debug will be used. Otherwise, the - INSTALL_MOD_STRIP value will be used as the option(s) to the strip - command. - - -=== 9 Makefile language - -The kernel Makefiles are designed to be run with GNU Make. The Makefiles -use only the documented features of GNU Make, but they do use many -GNU extensions. - -GNU Make supports elementary list-processing functions. The kernel -Makefiles use a novel style of list building and manipulation with few -"if" statements. - -GNU Make has two assignment operators, ":=" and "=". ":=" performs -immediate evaluation of the right-hand side and stores an actual string -into the left-hand side. "=" is like a formula definition; it stores the -right-hand side in an unevaluated form and then evaluates this form each -time the left-hand side is used. - -There are some cases where "=" is appropriate. Usually, though, ":=" -is the right choice. - -=== 10 Credits - -Original version made by Michael Elizabeth Chastain, -Updates by Kai Germaschewski -Updates by Sam Ravnborg -Language QA by Jan Engelhardt - -=== 11 TODO - -- Describe how kbuild supports shipped files with _shipped. -- Generating offset header files. -- Add more variables to section 7? - - - diff --git a/Documentation/kbuild/modules.rst b/Documentation/kbuild/modules.rst new file mode 100644 index 000000000000..24e763482650 --- /dev/null +++ b/Documentation/kbuild/modules.rst @@ -0,0 +1,571 @@ +========================= +Building External Modules +========================= + +This document describes how to build an out-of-tree kernel module. + +.. Table of Contents + + === 1 Introduction + === 2 How to Build External Modules + --- 2.1 Command Syntax + --- 2.2 Options + --- 2.3 Targets + --- 2.4 Building Separate Files + === 3. Creating a Kbuild File for an External Module + --- 3.1 Shared Makefile + --- 3.2 Separate Kbuild file and Makefile + --- 3.3 Binary Blobs + --- 3.4 Building Multiple Modules + === 4. Include Files + --- 4.1 Kernel Includes + --- 4.2 Single Subdirectory + --- 4.3 Several Subdirectories + === 5. Module Installation + --- 5.1 INSTALL_MOD_PATH + --- 5.2 INSTALL_MOD_DIR + === 6. Module Versioning + --- 6.1 Symbols From the Kernel (vmlinux + modules) + --- 6.2 Symbols and External Modules + --- 6.3 Symbols From Another External Module + === 7. Tips & Tricks + --- 7.1 Testing for CONFIG_FOO_BAR + + + +1. Introduction +=============== + +"kbuild" is the build system used by the Linux kernel. Modules must use +kbuild to stay compatible with changes in the build infrastructure and +to pick up the right flags to "gcc." Functionality for building modules +both in-tree and out-of-tree is provided. The method for building +either is similar, and all modules are initially developed and built +out-of-tree. + +Covered in this document is information aimed at developers interested +in building out-of-tree (or "external") modules. The author of an +external module should supply a makefile that hides most of the +complexity, so one only has to type "make" to build the module. This is +easily accomplished, and a complete example will be presented in +section 3. + + +2. How to Build External Modules +================================ + +To build external modules, you must have a prebuilt kernel available +that contains the configuration and header files used in the build. +Also, the kernel must have been built with modules enabled. If you are +using a distribution kernel, there will be a package for the kernel you +are running provided by your distribution. + +An alternative is to use the "make" target "modules_prepare." This will +make sure the kernel contains the information required. The target +exists solely as a simple way to prepare a kernel source tree for +building external modules. + +NOTE: "modules_prepare" will not build Module.symvers even if +CONFIG_MODVERSIONS is set; therefore, a full kernel build needs to be +executed to make module versioning work. + +2.1 Command Syntax +================== + + The command to build an external module is:: + + $ make -C M=$PWD + + The kbuild system knows that an external module is being built + due to the "M=" option given in the command. + + To build against the running kernel use:: + + $ make -C /lib/modules/`uname -r`/build M=$PWD + + Then to install the module(s) just built, add the target + "modules_install" to the command:: + + $ make -C /lib/modules/`uname -r`/build M=$PWD modules_install + +2.2 Options +=========== + + ($KDIR refers to the path of the kernel source directory.) + + make -C $KDIR M=$PWD + + -C $KDIR + The directory where the kernel source is located. + "make" will actually change to the specified directory + when executing and will change back when finished. + + M=$PWD + Informs kbuild that an external module is being built. + The value given to "M" is the absolute path of the + directory where the external module (kbuild file) is + located. + +2.3 Targets +=========== + + When building an external module, only a subset of the "make" + targets are available. + + make -C $KDIR M=$PWD [target] + + The default will build the module(s) located in the current + directory, so a target does not need to be specified. All + output files will also be generated in this directory. No + attempts are made to update the kernel source, and it is a + precondition that a successful "make" has been executed for the + kernel. + + modules + The default target for external modules. It has the + same functionality as if no target was specified. See + description above. + + modules_install + Install the external module(s). The default location is + /lib/modules//extra/, but a prefix may + be added with INSTALL_MOD_PATH (discussed in section 5). + + clean + Remove all generated files in the module directory only. + + help + List the available targets for external modules. + +2.4 Building Separate Files +=========================== + + It is possible to build single files that are part of a module. + This works equally well for the kernel, a module, and even for + external modules. + + Example (The module foo.ko, consist of bar.o and baz.o):: + + make -C $KDIR M=$PWD bar.lst + make -C $KDIR M=$PWD baz.o + make -C $KDIR M=$PWD foo.ko + make -C $KDIR M=$PWD ./ + + +3. Creating a Kbuild File for an External Module +================================================ + +In the last section we saw the command to build a module for the +running kernel. The module is not actually built, however, because a +build file is required. Contained in this file will be the name of +the module(s) being built, along with the list of requisite source +files. The file may be as simple as a single line:: + + obj-m := .o + +The kbuild system will build .o from .c, +and, after linking, will result in the kernel module .ko. +The above line can be put in either a "Kbuild" file or a "Makefile." +When the module is built from multiple sources, an additional line is +needed listing the files:: + + -y := .o .o ... + +NOTE: Further documentation describing the syntax used by kbuild is +located in Documentation/kbuild/makefiles.rst. + +The examples below demonstrate how to create a build file for the +module 8123.ko, which is built from the following files:: + + 8123_if.c + 8123_if.h + 8123_pci.c + 8123_bin.o_shipped <= Binary blob + +--- 3.1 Shared Makefile + + An external module always includes a wrapper makefile that + supports building the module using "make" with no arguments. + This target is not used by kbuild; it is only for convenience. + Additional functionality, such as test targets, can be included + but should be filtered out from kbuild due to possible name + clashes. + + Example 1:: + + --> filename: Makefile + ifneq ($(KERNELRELEASE),) + # kbuild part of makefile + obj-m := 8123.o + 8123-y := 8123_if.o 8123_pci.o 8123_bin.o + + else + # normal makefile + KDIR ?= /lib/modules/`uname -r`/build + + default: + $(MAKE) -C $(KDIR) M=$$PWD + + # Module specific targets + genbin: + echo "X" > 8123_bin.o_shipped + + endif + + The check for KERNELRELEASE is used to separate the two parts + of the makefile. In the example, kbuild will only see the two + assignments, whereas "make" will see everything except these + two assignments. This is due to two passes made on the file: + the first pass is by the "make" instance run on the command + line; the second pass is by the kbuild system, which is + initiated by the parameterized "make" in the default target. + +3.2 Separate Kbuild File and Makefile +------------------------------------- + + In newer versions of the kernel, kbuild will first look for a + file named "Kbuild," and only if that is not found, will it + then look for a makefile. Utilizing a "Kbuild" file allows us + to split up the makefile from example 1 into two files: + + Example 2:: + + --> filename: Kbuild + obj-m := 8123.o + 8123-y := 8123_if.o 8123_pci.o 8123_bin.o + + --> filename: Makefile + KDIR ?= /lib/modules/`uname -r`/build + + default: + $(MAKE) -C $(KDIR) M=$$PWD + + # Module specific targets + genbin: + echo "X" > 8123_bin.o_shipped + + The split in example 2 is questionable due to the simplicity of + each file; however, some external modules use makefiles + consisting of several hundred lines, and here it really pays + off to separate the kbuild part from the rest. + + The next example shows a backward compatible version. + + Example 3:: + + --> filename: Kbuild + obj-m := 8123.o + 8123-y := 8123_if.o 8123_pci.o 8123_bin.o + + --> filename: Makefile + ifneq ($(KERNELRELEASE),) + # kbuild part of makefile + include Kbuild + + else + # normal makefile + KDIR ?= /lib/modules/`uname -r`/build + + default: + $(MAKE) -C $(KDIR) M=$$PWD + + # Module specific targets + genbin: + echo "X" > 8123_bin.o_shipped + + endif + + Here the "Kbuild" file is included from the makefile. This + allows an older version of kbuild, which only knows of + makefiles, to be used when the "make" and kbuild parts are + split into separate files. + +3.3 Binary Blobs +---------------- + + Some external modules need to include an object file as a blob. + kbuild has support for this, but requires the blob file to be + named _shipped. When the kbuild rules kick in, a copy + of _shipped is created with _shipped stripped off, + giving us . This shortened filename can be used in + the assignment to the module. + + Throughout this section, 8123_bin.o_shipped has been used to + build the kernel module 8123.ko; it has been included as + 8123_bin.o:: + + 8123-y := 8123_if.o 8123_pci.o 8123_bin.o + + Although there is no distinction between the ordinary source + files and the binary file, kbuild will pick up different rules + when creating the object file for the module. + +3.4 Building Multiple Modules +============================= + + kbuild supports building multiple modules with a single build + file. For example, if you wanted to build two modules, foo.ko + and bar.ko, the kbuild lines would be:: + + obj-m := foo.o bar.o + foo-y := + bar-y := + + It is that simple! + + +4. Include Files +================ + +Within the kernel, header files are kept in standard locations +according to the following rule: + + * If the header file only describes the internal interface of a + module, then the file is placed in the same directory as the + source files. + * If the header file describes an interface used by other parts + of the kernel that are located in different directories, then + the file is placed in include/linux/. + + NOTE: + There are two notable exceptions to this rule: larger + subsystems have their own directory under include/, such as + include/scsi; and architecture specific headers are located + under arch/$(ARCH)/include/. + +4.1 Kernel Includes +------------------- + + To include a header file located under include/linux/, simply + use:: + + #include + + kbuild will add options to "gcc" so the relevant directories + are searched. + +4.2 Single Subdirectory +----------------------- + + External modules tend to place header files in a separate + include/ directory where their source is located, although this + is not the usual kernel style. To inform kbuild of the + directory, use either ccflags-y or CFLAGS_.o. + + Using the example from section 3, if we moved 8123_if.h to a + subdirectory named include, the resulting kbuild file would + look like:: + + --> filename: Kbuild + obj-m := 8123.o + + ccflags-y := -Iinclude + 8123-y := 8123_if.o 8123_pci.o 8123_bin.o + + Note that in the assignment there is no space between -I and + the path. This is a limitation of kbuild: there must be no + space present. + +4.3 Several Subdirectories +-------------------------- + + kbuild can handle files that are spread over several directories. + Consider the following example:: + + . + |__ src + | |__ complex_main.c + | |__ hal + | |__ hardwareif.c + | |__ include + | |__ hardwareif.h + |__ include + |__ complex.h + + To build the module complex.ko, we then need the following + kbuild file:: + + --> filename: Kbuild + obj-m := complex.o + complex-y := src/complex_main.o + complex-y += src/hal/hardwareif.o + + ccflags-y := -I$(src)/include + ccflags-y += -I$(src)/src/hal/include + + As you can see, kbuild knows how to handle object files located + in other directories. The trick is to specify the directory + relative to the kbuild file's location. That being said, this + is NOT recommended practice. + + For the header files, kbuild must be explicitly told where to + look. When kbuild executes, the current directory is always the + root of the kernel tree (the argument to "-C") and therefore an + absolute path is needed. $(src) provides the absolute path by + pointing to the directory where the currently executing kbuild + file is located. + + +5. Module Installation +====================== + +Modules which are included in the kernel are installed in the +directory: + + /lib/modules/$(KERNELRELEASE)/kernel/ + +And external modules are installed in: + + /lib/modules/$(KERNELRELEASE)/extra/ + +5.1 INSTALL_MOD_PATH +-------------------- + + Above are the default directories but as always some level of + customization is possible. A prefix can be added to the + installation path using the variable INSTALL_MOD_PATH:: + + $ make INSTALL_MOD_PATH=/frodo modules_install + => Install dir: /frodo/lib/modules/$(KERNELRELEASE)/kernel/ + + INSTALL_MOD_PATH may be set as an ordinary shell variable or, + as shown above, can be specified on the command line when + calling "make." This has effect when installing both in-tree + and out-of-tree modules. + +5.2 INSTALL_MOD_DIR +------------------- + + External modules are by default installed to a directory under + /lib/modules/$(KERNELRELEASE)/extra/, but you may wish to + locate modules for a specific functionality in a separate + directory. For this purpose, use INSTALL_MOD_DIR to specify an + alternative name to "extra.":: + + $ make INSTALL_MOD_DIR=gandalf -C $KDIR \ + M=$PWD modules_install + => Install dir: /lib/modules/$(KERNELRELEASE)/gandalf/ + + +6. Module Versioning +==================== + +Module versioning is enabled by the CONFIG_MODVERSIONS tag, and is used +as a simple ABI consistency check. A CRC value of the full prototype +for an exported symbol is created. When a module is loaded/used, the +CRC values contained in the kernel are compared with similar values in +the module; if they are not equal, the kernel refuses to load the +module. + +Module.symvers contains a list of all exported symbols from a kernel +build. + +6.1 Symbols From the Kernel (vmlinux + modules) +----------------------------------------------- + + During a kernel build, a file named Module.symvers will be + generated. Module.symvers contains all exported symbols from + the kernel and compiled modules. For each symbol, the + corresponding CRC value is also stored. + + The syntax of the Module.symvers file is:: + + + + 0x2d036834 scsi_remove_host drivers/scsi/scsi_mod + + For a kernel build without CONFIG_MODVERSIONS enabled, the CRC + would read 0x00000000. + + Module.symvers serves two purposes: + + 1) It lists all exported symbols from vmlinux and all modules. + 2) It lists the CRC if CONFIG_MODVERSIONS is enabled. + +6.2 Symbols and External Modules +-------------------------------- + + When building an external module, the build system needs access + to the symbols from the kernel to check if all external symbols + are defined. This is done in the MODPOST step. modpost obtains + the symbols by reading Module.symvers from the kernel source + tree. If a Module.symvers file is present in the directory + where the external module is being built, this file will be + read too. During the MODPOST step, a new Module.symvers file + will be written containing all exported symbols that were not + defined in the kernel. + +--- 6.3 Symbols From Another External Module + + Sometimes, an external module uses exported symbols from + another external module. kbuild needs to have full knowledge of + all symbols to avoid spitting out warnings about undefined + symbols. Three solutions exist for this situation. + + NOTE: The method with a top-level kbuild file is recommended + but may be impractical in certain situations. + + Use a top-level kbuild file + If you have two modules, foo.ko and bar.ko, where + foo.ko needs symbols from bar.ko, you can use a + common top-level kbuild file so both modules are + compiled in the same build. Consider the following + directory layout:: + + ./foo/ <= contains foo.ko + ./bar/ <= contains bar.ko + + The top-level kbuild file would then look like:: + + #./Kbuild (or ./Makefile): + obj-y := foo/ bar/ + + And executing:: + + $ make -C $KDIR M=$PWD + + will then do the expected and compile both modules with + full knowledge of symbols from either module. + + Use an extra Module.symvers file + When an external module is built, a Module.symvers file + is generated containing all exported symbols which are + not defined in the kernel. To get access to symbols + from bar.ko, copy the Module.symvers file from the + compilation of bar.ko to the directory where foo.ko is + built. During the module build, kbuild will read the + Module.symvers file in the directory of the external + module, and when the build is finished, a new + Module.symvers file is created containing the sum of + all symbols defined and not part of the kernel. + + Use "make" variable KBUILD_EXTRA_SYMBOLS + If it is impractical to copy Module.symvers from + another module, you can assign a space separated list + of files to KBUILD_EXTRA_SYMBOLS in your build file. + These files will be loaded by modpost during the + initialization of its symbol tables. + + +7. Tips & Tricks +================ + +7.1 Testing for CONFIG_FOO_BAR +------------------------------ + + Modules often need to check for certain `CONFIG_` options to + decide if a specific feature is included in the module. In + kbuild this is done by referencing the `CONFIG_` variable + directly:: + + #fs/ext2/Makefile + obj-$(CONFIG_EXT2_FS) += ext2.o + + ext2-y := balloc.o bitmap.o dir.o + ext2-$(CONFIG_EXT2_FS_XATTR) += xattr.o + + External modules have traditionally used "grep" to check for + specific `CONFIG_` settings directly in .config. This usage is + broken. As introduced before, external modules should use + kbuild for building and can therefore use the same methods as + in-tree modules when testing for `CONFIG_` definitions. diff --git a/Documentation/kbuild/modules.txt b/Documentation/kbuild/modules.txt deleted file mode 100644 index 80295c613e37..000000000000 --- a/Documentation/kbuild/modules.txt +++ /dev/null @@ -1,541 +0,0 @@ -Building External Modules - -This document describes how to build an out-of-tree kernel module. - -=== Table of Contents - - === 1 Introduction - === 2 How to Build External Modules - --- 2.1 Command Syntax - --- 2.2 Options - --- 2.3 Targets - --- 2.4 Building Separate Files - === 3. Creating a Kbuild File for an External Module - --- 3.1 Shared Makefile - --- 3.2 Separate Kbuild file and Makefile - --- 3.3 Binary Blobs - --- 3.4 Building Multiple Modules - === 4. Include Files - --- 4.1 Kernel Includes - --- 4.2 Single Subdirectory - --- 4.3 Several Subdirectories - === 5. Module Installation - --- 5.1 INSTALL_MOD_PATH - --- 5.2 INSTALL_MOD_DIR - === 6. Module Versioning - --- 6.1 Symbols From the Kernel (vmlinux + modules) - --- 6.2 Symbols and External Modules - --- 6.3 Symbols From Another External Module - === 7. Tips & Tricks - --- 7.1 Testing for CONFIG_FOO_BAR - - - -=== 1. Introduction - -"kbuild" is the build system used by the Linux kernel. Modules must use -kbuild to stay compatible with changes in the build infrastructure and -to pick up the right flags to "gcc." Functionality for building modules -both in-tree and out-of-tree is provided. The method for building -either is similar, and all modules are initially developed and built -out-of-tree. - -Covered in this document is information aimed at developers interested -in building out-of-tree (or "external") modules. The author of an -external module should supply a makefile that hides most of the -complexity, so one only has to type "make" to build the module. This is -easily accomplished, and a complete example will be presented in -section 3. - - -=== 2. How to Build External Modules - -To build external modules, you must have a prebuilt kernel available -that contains the configuration and header files used in the build. -Also, the kernel must have been built with modules enabled. If you are -using a distribution kernel, there will be a package for the kernel you -are running provided by your distribution. - -An alternative is to use the "make" target "modules_prepare." This will -make sure the kernel contains the information required. The target -exists solely as a simple way to prepare a kernel source tree for -building external modules. - -NOTE: "modules_prepare" will not build Module.symvers even if -CONFIG_MODVERSIONS is set; therefore, a full kernel build needs to be -executed to make module versioning work. - ---- 2.1 Command Syntax - - The command to build an external module is: - - $ make -C M=$PWD - - The kbuild system knows that an external module is being built - due to the "M=" option given in the command. - - To build against the running kernel use: - - $ make -C /lib/modules/`uname -r`/build M=$PWD - - Then to install the module(s) just built, add the target - "modules_install" to the command: - - $ make -C /lib/modules/`uname -r`/build M=$PWD modules_install - ---- 2.2 Options - - ($KDIR refers to the path of the kernel source directory.) - - make -C $KDIR M=$PWD - - -C $KDIR - The directory where the kernel source is located. - "make" will actually change to the specified directory - when executing and will change back when finished. - - M=$PWD - Informs kbuild that an external module is being built. - The value given to "M" is the absolute path of the - directory where the external module (kbuild file) is - located. - ---- 2.3 Targets - - When building an external module, only a subset of the "make" - targets are available. - - make -C $KDIR M=$PWD [target] - - The default will build the module(s) located in the current - directory, so a target does not need to be specified. All - output files will also be generated in this directory. No - attempts are made to update the kernel source, and it is a - precondition that a successful "make" has been executed for the - kernel. - - modules - The default target for external modules. It has the - same functionality as if no target was specified. See - description above. - - modules_install - Install the external module(s). The default location is - /lib/modules//extra/, but a prefix may - be added with INSTALL_MOD_PATH (discussed in section 5). - - clean - Remove all generated files in the module directory only. - - help - List the available targets for external modules. - ---- 2.4 Building Separate Files - - It is possible to build single files that are part of a module. - This works equally well for the kernel, a module, and even for - external modules. - - Example (The module foo.ko, consist of bar.o and baz.o): - make -C $KDIR M=$PWD bar.lst - make -C $KDIR M=$PWD baz.o - make -C $KDIR M=$PWD foo.ko - make -C $KDIR M=$PWD ./ - - -=== 3. Creating a Kbuild File for an External Module - -In the last section we saw the command to build a module for the -running kernel. The module is not actually built, however, because a -build file is required. Contained in this file will be the name of -the module(s) being built, along with the list of requisite source -files. The file may be as simple as a single line: - - obj-m := .o - -The kbuild system will build .o from .c, -and, after linking, will result in the kernel module .ko. -The above line can be put in either a "Kbuild" file or a "Makefile." -When the module is built from multiple sources, an additional line is -needed listing the files: - - -y := .o .o ... - -NOTE: Further documentation describing the syntax used by kbuild is -located in Documentation/kbuild/makefiles.txt. - -The examples below demonstrate how to create a build file for the -module 8123.ko, which is built from the following files: - - 8123_if.c - 8123_if.h - 8123_pci.c - 8123_bin.o_shipped <= Binary blob - ---- 3.1 Shared Makefile - - An external module always includes a wrapper makefile that - supports building the module using "make" with no arguments. - This target is not used by kbuild; it is only for convenience. - Additional functionality, such as test targets, can be included - but should be filtered out from kbuild due to possible name - clashes. - - Example 1: - --> filename: Makefile - ifneq ($(KERNELRELEASE),) - # kbuild part of makefile - obj-m := 8123.o - 8123-y := 8123_if.o 8123_pci.o 8123_bin.o - - else - # normal makefile - KDIR ?= /lib/modules/`uname -r`/build - - default: - $(MAKE) -C $(KDIR) M=$$PWD - - # Module specific targets - genbin: - echo "X" > 8123_bin.o_shipped - - endif - - The check for KERNELRELEASE is used to separate the two parts - of the makefile. In the example, kbuild will only see the two - assignments, whereas "make" will see everything except these - two assignments. This is due to two passes made on the file: - the first pass is by the "make" instance run on the command - line; the second pass is by the kbuild system, which is - initiated by the parameterized "make" in the default target. - ---- 3.2 Separate Kbuild File and Makefile - - In newer versions of the kernel, kbuild will first look for a - file named "Kbuild," and only if that is not found, will it - then look for a makefile. Utilizing a "Kbuild" file allows us - to split up the makefile from example 1 into two files: - - Example 2: - --> filename: Kbuild - obj-m := 8123.o - 8123-y := 8123_if.o 8123_pci.o 8123_bin.o - - --> filename: Makefile - KDIR ?= /lib/modules/`uname -r`/build - - default: - $(MAKE) -C $(KDIR) M=$$PWD - - # Module specific targets - genbin: - echo "X" > 8123_bin.o_shipped - - The split in example 2 is questionable due to the simplicity of - each file; however, some external modules use makefiles - consisting of several hundred lines, and here it really pays - off to separate the kbuild part from the rest. - - The next example shows a backward compatible version. - - Example 3: - --> filename: Kbuild - obj-m := 8123.o - 8123-y := 8123_if.o 8123_pci.o 8123_bin.o - - --> filename: Makefile - ifneq ($(KERNELRELEASE),) - # kbuild part of makefile - include Kbuild - - else - # normal makefile - KDIR ?= /lib/modules/`uname -r`/build - - default: - $(MAKE) -C $(KDIR) M=$$PWD - - # Module specific targets - genbin: - echo "X" > 8123_bin.o_shipped - - endif - - Here the "Kbuild" file is included from the makefile. This - allows an older version of kbuild, which only knows of - makefiles, to be used when the "make" and kbuild parts are - split into separate files. - ---- 3.3 Binary Blobs - - Some external modules need to include an object file as a blob. - kbuild has support for this, but requires the blob file to be - named _shipped. When the kbuild rules kick in, a copy - of _shipped is created with _shipped stripped off, - giving us . This shortened filename can be used in - the assignment to the module. - - Throughout this section, 8123_bin.o_shipped has been used to - build the kernel module 8123.ko; it has been included as - 8123_bin.o. - - 8123-y := 8123_if.o 8123_pci.o 8123_bin.o - - Although there is no distinction between the ordinary source - files and the binary file, kbuild will pick up different rules - when creating the object file for the module. - ---- 3.4 Building Multiple Modules - - kbuild supports building multiple modules with a single build - file. For example, if you wanted to build two modules, foo.ko - and bar.ko, the kbuild lines would be: - - obj-m := foo.o bar.o - foo-y := - bar-y := - - It is that simple! - - -=== 4. Include Files - -Within the kernel, header files are kept in standard locations -according to the following rule: - - * If the header file only describes the internal interface of a - module, then the file is placed in the same directory as the - source files. - * If the header file describes an interface used by other parts - of the kernel that are located in different directories, then - the file is placed in include/linux/. - - NOTE: There are two notable exceptions to this rule: larger - subsystems have their own directory under include/, such as - include/scsi; and architecture specific headers are located - under arch/$(ARCH)/include/. - ---- 4.1 Kernel Includes - - To include a header file located under include/linux/, simply - use: - - #include - - kbuild will add options to "gcc" so the relevant directories - are searched. - ---- 4.2 Single Subdirectory - - External modules tend to place header files in a separate - include/ directory where their source is located, although this - is not the usual kernel style. To inform kbuild of the - directory, use either ccflags-y or CFLAGS_.o. - - Using the example from section 3, if we moved 8123_if.h to a - subdirectory named include, the resulting kbuild file would - look like: - - --> filename: Kbuild - obj-m := 8123.o - - ccflags-y := -Iinclude - 8123-y := 8123_if.o 8123_pci.o 8123_bin.o - - Note that in the assignment there is no space between -I and - the path. This is a limitation of kbuild: there must be no - space present. - ---- 4.3 Several Subdirectories - - kbuild can handle files that are spread over several directories. - Consider the following example: - - . - |__ src - | |__ complex_main.c - | |__ hal - | |__ hardwareif.c - | |__ include - | |__ hardwareif.h - |__ include - |__ complex.h - - To build the module complex.ko, we then need the following - kbuild file: - - --> filename: Kbuild - obj-m := complex.o - complex-y := src/complex_main.o - complex-y += src/hal/hardwareif.o - - ccflags-y := -I$(src)/include - ccflags-y += -I$(src)/src/hal/include - - As you can see, kbuild knows how to handle object files located - in other directories. The trick is to specify the directory - relative to the kbuild file's location. That being said, this - is NOT recommended practice. - - For the header files, kbuild must be explicitly told where to - look. When kbuild executes, the current directory is always the - root of the kernel tree (the argument to "-C") and therefore an - absolute path is needed. $(src) provides the absolute path by - pointing to the directory where the currently executing kbuild - file is located. - - -=== 5. Module Installation - -Modules which are included in the kernel are installed in the -directory: - - /lib/modules/$(KERNELRELEASE)/kernel/ - -And external modules are installed in: - - /lib/modules/$(KERNELRELEASE)/extra/ - ---- 5.1 INSTALL_MOD_PATH - - Above are the default directories but as always some level of - customization is possible. A prefix can be added to the - installation path using the variable INSTALL_MOD_PATH: - - $ make INSTALL_MOD_PATH=/frodo modules_install - => Install dir: /frodo/lib/modules/$(KERNELRELEASE)/kernel/ - - INSTALL_MOD_PATH may be set as an ordinary shell variable or, - as shown above, can be specified on the command line when - calling "make." This has effect when installing both in-tree - and out-of-tree modules. - ---- 5.2 INSTALL_MOD_DIR - - External modules are by default installed to a directory under - /lib/modules/$(KERNELRELEASE)/extra/, but you may wish to - locate modules for a specific functionality in a separate - directory. For this purpose, use INSTALL_MOD_DIR to specify an - alternative name to "extra." - - $ make INSTALL_MOD_DIR=gandalf -C $KDIR \ - M=$PWD modules_install - => Install dir: /lib/modules/$(KERNELRELEASE)/gandalf/ - - -=== 6. Module Versioning - -Module versioning is enabled by the CONFIG_MODVERSIONS tag, and is used -as a simple ABI consistency check. A CRC value of the full prototype -for an exported symbol is created. When a module is loaded/used, the -CRC values contained in the kernel are compared with similar values in -the module; if they are not equal, the kernel refuses to load the -module. - -Module.symvers contains a list of all exported symbols from a kernel -build. - ---- 6.1 Symbols From the Kernel (vmlinux + modules) - - During a kernel build, a file named Module.symvers will be - generated. Module.symvers contains all exported symbols from - the kernel and compiled modules. For each symbol, the - corresponding CRC value is also stored. - - The syntax of the Module.symvers file is: - - - 0x2d036834 scsi_remove_host drivers/scsi/scsi_mod - - For a kernel build without CONFIG_MODVERSIONS enabled, the CRC - would read 0x00000000. - - Module.symvers serves two purposes: - 1) It lists all exported symbols from vmlinux and all modules. - 2) It lists the CRC if CONFIG_MODVERSIONS is enabled. - ---- 6.2 Symbols and External Modules - - When building an external module, the build system needs access - to the symbols from the kernel to check if all external symbols - are defined. This is done in the MODPOST step. modpost obtains - the symbols by reading Module.symvers from the kernel source - tree. If a Module.symvers file is present in the directory - where the external module is being built, this file will be - read too. During the MODPOST step, a new Module.symvers file - will be written containing all exported symbols that were not - defined in the kernel. - ---- 6.3 Symbols From Another External Module - - Sometimes, an external module uses exported symbols from - another external module. kbuild needs to have full knowledge of - all symbols to avoid spitting out warnings about undefined - symbols. Three solutions exist for this situation. - - NOTE: The method with a top-level kbuild file is recommended - but may be impractical in certain situations. - - Use a top-level kbuild file - If you have two modules, foo.ko and bar.ko, where - foo.ko needs symbols from bar.ko, you can use a - common top-level kbuild file so both modules are - compiled in the same build. Consider the following - directory layout: - - ./foo/ <= contains foo.ko - ./bar/ <= contains bar.ko - - The top-level kbuild file would then look like: - - #./Kbuild (or ./Makefile): - obj-y := foo/ bar/ - - And executing - - $ make -C $KDIR M=$PWD - - will then do the expected and compile both modules with - full knowledge of symbols from either module. - - Use an extra Module.symvers file - When an external module is built, a Module.symvers file - is generated containing all exported symbols which are - not defined in the kernel. To get access to symbols - from bar.ko, copy the Module.symvers file from the - compilation of bar.ko to the directory where foo.ko is - built. During the module build, kbuild will read the - Module.symvers file in the directory of the external - module, and when the build is finished, a new - Module.symvers file is created containing the sum of - all symbols defined and not part of the kernel. - - Use "make" variable KBUILD_EXTRA_SYMBOLS - If it is impractical to copy Module.symvers from - another module, you can assign a space separated list - of files to KBUILD_EXTRA_SYMBOLS in your build file. - These files will be loaded by modpost during the - initialization of its symbol tables. - - -=== 7. Tips & Tricks - ---- 7.1 Testing for CONFIG_FOO_BAR - - Modules often need to check for certain CONFIG_ options to - decide if a specific feature is included in the module. In - kbuild this is done by referencing the CONFIG_ variable - directly. - - #fs/ext2/Makefile - obj-$(CONFIG_EXT2_FS) += ext2.o - - ext2-y := balloc.o bitmap.o dir.o - ext2-$(CONFIG_EXT2_FS_XATTR) += xattr.o - - External modules have traditionally used "grep" to check for - specific CONFIG_ settings directly in .config. This usage is - broken. As introduced before, external modules should use - kbuild for building and can therefore use the same methods as - in-tree modules when testing for CONFIG_ definitions. - diff --git a/Documentation/kernel-hacking/hacking.rst b/Documentation/kernel-hacking/hacking.rst index d824e4feaff3..5891a701a159 100644 --- a/Documentation/kernel-hacking/hacking.rst +++ b/Documentation/kernel-hacking/hacking.rst @@ -718,7 +718,7 @@ make a neat patch, there's administrative work to be done: - Usually you want a configuration option for your kernel hack. Edit ``Kconfig`` in the appropriate directory. The Config language is simple to use by cut and paste, and there's complete documentation in - ``Documentation/kbuild/kconfig-language.txt``. + ``Documentation/kbuild/kconfig-language.rst``. In your description of the option, make sure you address both the expert user and the user who knows nothing about your feature. @@ -728,7 +728,7 @@ make a neat patch, there's administrative work to be done: - Edit the ``Makefile``: the CONFIG variables are exported here so you can usually just add a "obj-$(CONFIG_xxx) += xxx.o" line. The syntax - is documented in ``Documentation/kbuild/makefiles.txt``. + is documented in ``Documentation/kbuild/makefiles.rst``. - Put yourself in ``CREDITS`` if you've done something noteworthy, usually beyond a single file (your name should be at the top of the diff --git a/Documentation/process/coding-style.rst b/Documentation/process/coding-style.rst index fa864a51e6ea..f4a2198187f9 100644 --- a/Documentation/process/coding-style.rst +++ b/Documentation/process/coding-style.rst @@ -686,7 +686,7 @@ filesystems) should advertise this prominently in their prompt string:: ... For full documentation on the configuration files, see the file -Documentation/kbuild/kconfig-language.txt. +Documentation/kbuild/kconfig-language.rst. 11) Data structures diff --git a/Documentation/process/submit-checklist.rst b/Documentation/process/submit-checklist.rst index c88867b173d9..365efc9e4aa8 100644 --- a/Documentation/process/submit-checklist.rst +++ b/Documentation/process/submit-checklist.rst @@ -39,7 +39,7 @@ and elsewhere regarding submitting Linux kernel patches. 6) Any new or modified ``CONFIG`` options do not muck up the config menu and default to off unless they meet the exception criteria documented in - ``Documentation/kbuild/kconfig-language.txt`` Menu attributes: default value. + ``Documentation/kbuild/kconfig-language.rst`` Menu attributes: default value. 7) All new ``Kconfig`` options have help text. diff --git a/Documentation/translations/it_IT/kernel-hacking/hacking.rst b/Documentation/translations/it_IT/kernel-hacking/hacking.rst index 7178e517af0a..24c592852bf1 100644 --- a/Documentation/translations/it_IT/kernel-hacking/hacking.rst +++ b/Documentation/translations/it_IT/kernel-hacking/hacking.rst @@ -755,7 +755,7 @@ anche per avere patch pulite, c'è del lavoro amministrativo da fare: - Solitamente vorrete un'opzione di configurazione per la vostra modifica al kernel. Modificate ``Kconfig`` nella cartella giusta. Il linguaggio Config è facile con copia ed incolla, e c'è una completa documentazione - nel file ``Documentation/kbuild/kconfig-language.txt``. + nel file ``Documentation/kbuild/kconfig-language.rst``. Nella descrizione della vostra opzione, assicuratevi di parlare sia agli utenti esperti sia agli utente che non sanno nulla del vostro lavoro. @@ -767,7 +767,7 @@ anche per avere patch pulite, c'è del lavoro amministrativo da fare: - Modificate il file ``Makefile``: le variabili CONFIG sono esportate qui, quindi potete solitamente aggiungere una riga come la seguete "obj-$(CONFIG_xxx) += xxx.o". La sintassi è documentata nel file - ``Documentation/kbuild/makefiles.txt``. + ``Documentation/kbuild/makefiles.rst``. - Aggiungete voi stessi in ``CREDITS`` se avete fatto qualcosa di notevole, solitamente qualcosa che supera il singolo file (comunque il vostro nome diff --git a/Documentation/translations/it_IT/process/coding-style.rst b/Documentation/translations/it_IT/process/coding-style.rst index a6559d25a23d..8995d2d19f20 100644 --- a/Documentation/translations/it_IT/process/coding-style.rst +++ b/Documentation/translations/it_IT/process/coding-style.rst @@ -696,7 +696,7 @@ nella stringa di titolo:: ... Per la documentazione completa sui file di configurazione, consultate -il documento Documentation/kbuild/kconfig-language.txt +il documento Documentation/kbuild/kconfig-language.rst 11) Strutture dati diff --git a/Documentation/translations/it_IT/process/submit-checklist.rst b/Documentation/translations/it_IT/process/submit-checklist.rst index 70e65a7b3620..ea74cae958d7 100644 --- a/Documentation/translations/it_IT/process/submit-checklist.rst +++ b/Documentation/translations/it_IT/process/submit-checklist.rst @@ -43,7 +43,7 @@ sottomissione delle patch, in particolare 6) Le opzioni ``CONFIG``, nuove o modificate, non scombussolano il menu di configurazione e sono preimpostate come disabilitate a meno che non - soddisfino i criteri descritti in ``Documentation/kbuild/kconfig-language.txt`` + soddisfino i criteri descritti in ``Documentation/kbuild/kconfig-language.rst`` alla punto "Voci di menu: valori predefiniti". 7) Tutte le nuove opzioni ``Kconfig`` hanno un messaggio di aiuto. diff --git a/Documentation/translations/zh_CN/process/coding-style.rst b/Documentation/translations/zh_CN/process/coding-style.rst index 5479c591c2f7..4f6237392e65 100644 --- a/Documentation/translations/zh_CN/process/coding-style.rst +++ b/Documentation/translations/zh_CN/process/coding-style.rst @@ -599,7 +599,7 @@ Documentation/doc-guide/ 和 scripts/kernel-doc 以获得详细信息。 depends on ADFS_FS ... -要查看配置文件的完整文档，请看 Documentation/kbuild/kconfig-language.txt。 +要查看配置文件的完整文档，请看 Documentation/kbuild/kconfig-language.rst。 11) 数据结构 diff --git a/Documentation/translations/zh_CN/process/submit-checklist.rst b/Documentation/translations/zh_CN/process/submit-checklist.rst index 89061aa8fdbe..f4785d2b0491 100644 --- a/Documentation/translations/zh_CN/process/submit-checklist.rst +++ b/Documentation/translations/zh_CN/process/submit-checklist.rst @@ -38,7 +38,7 @@ Linux内核补丁提交清单 违规行为。 6) 任何新的或修改过的 ``CONFIG`` 选项都不会弄脏配置菜单，并默认为关闭，除非 - 它们符合 ``Documentation/kbuild/kconfig-language.txt`` 中记录的异常条件, + 它们符合 ``Documentation/kbuild/kconfig-language.rst`` 中记录的异常条件, 菜单属性：默认值. 7) 所有新的 ``kconfig`` 选项都有帮助文本。 diff --git a/Kconfig b/Kconfig index 990b0c390dfc..e10b3ee084d4 100644 --- a/Kconfig +++ b/Kconfig @@ -1,7 +1,7 @@ # SPDX-License-Identifier: GPL-2.0 # # For a description of the syntax of this configuration file, -# see Documentation/kbuild/kconfig-language.txt. +# see Documentation/kbuild/kconfig-language.rst. # mainmenu "Linux/$(ARCH) $(KERNELVERSION) Kernel Configuration" diff --git a/arch/arc/plat-eznps/Kconfig b/arch/arc/plat-eznps/Kconfig index 2eaecfb063a7..a376a50d3fea 100644 --- a/arch/arc/plat-eznps/Kconfig +++ b/arch/arc/plat-eznps/Kconfig @@ -1,7 +1,7 @@ # SPDX-License-Identifier: GPL-2.0 # # For a description of the syntax of this configuration file, -# see Documentation/kbuild/kconfig-language.txt. +# see Documentation/kbuild/kconfig-language.rst. # menuconfig ARC_PLAT_EZNPS diff --git a/arch/c6x/Kconfig b/arch/c6x/Kconfig index eeb0471268a0..c5e6b70e1510 100644 --- a/arch/c6x/Kconfig +++ b/arch/c6x/Kconfig @@ -1,7 +1,7 @@ # SPDX-License-Identifier: GPL-2.0 # # For a description of the syntax of this configuration file, -# see Documentation/kbuild/kconfig-language.txt. +# see Documentation/kbuild/kconfig-language.rst. # config C6X diff --git a/arch/microblaze/Kconfig.debug b/arch/microblaze/Kconfig.debug index 3a343188d86c..865527ac332a 100644 --- a/arch/microblaze/Kconfig.debug +++ b/arch/microblaze/Kconfig.debug @@ -1,6 +1,6 @@ # SPDX-License-Identifier: GPL-2.0-only # For a description of the syntax of this configuration file, -# see Documentation/kbuild/kconfig-language.txt. +# see Documentation/kbuild/kconfig-language.rst. config TRACE_IRQFLAGS_SUPPORT def_bool y diff --git a/arch/microblaze/Kconfig.platform b/arch/microblaze/Kconfig.platform index 5bf54c1d4f60..7795f90dad86 100644 --- a/arch/microblaze/Kconfig.platform +++ b/arch/microblaze/Kconfig.platform @@ -1,6 +1,6 @@ # SPDX-License-Identifier: GPL-2.0-only # For a description of the syntax of this configuration file, -# see Documentation/kbuild/kconfig-language.txt. +# see Documentation/kbuild/kconfig-language.rst. # # Platform selection Kconfig menu for MicroBlaze targets # diff --git a/arch/nds32/Kconfig b/arch/nds32/Kconfig index 3299e287a477..fd0d0639454f 100644 --- a/arch/nds32/Kconfig +++ b/arch/nds32/Kconfig @@ -1,7 +1,7 @@ # SPDX-License-Identifier: GPL-2.0-only # # For a description of the syntax of this configuration file, -# see Documentation/kbuild/kconfig-language.txt. +# see Documentation/kbuild/kconfig-language.rst. # config NDS32 diff --git a/arch/openrisc/Kconfig b/arch/openrisc/Kconfig index 7cfb20555b10..bf326f0edd2f 100644 --- a/arch/openrisc/Kconfig +++ b/arch/openrisc/Kconfig @@ -1,7 +1,7 @@ # SPDX-License-Identifier: GPL-2.0 # # For a description of the syntax of this configuration file, -# see Documentation/kbuild/kconfig-language.txt. +# see Documentation/kbuild/kconfig-language.rst. # config OPENRISC diff --git a/arch/powerpc/sysdev/Kconfig b/arch/powerpc/sysdev/Kconfig index e0dbec780fe9..d23288c4abf6 100644 --- a/arch/powerpc/sysdev/Kconfig +++ b/arch/powerpc/sysdev/Kconfig @@ -1,6 +1,6 @@ # SPDX-License-Identifier: GPL-2.0 # For a description of the syntax of this configuration file, -# see Documentation/kbuild/kconfig-language.txt. +# see Documentation/kbuild/kconfig-language.rst. # config PPC4xx_PCI_EXPRESS diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig index 0c4b12205632..be713da93946 100644 --- a/arch/riscv/Kconfig +++ b/arch/riscv/Kconfig @@ -1,7 +1,7 @@ # SPDX-License-Identifier: GPL-2.0-only # # For a description of the syntax of this configuration file, -# see Documentation/kbuild/kconfig-language.txt. +# see Documentation/kbuild/kconfig-language.rst. # config 64BIT diff --git a/drivers/auxdisplay/Kconfig b/drivers/auxdisplay/Kconfig index c52c738e554a..dd61fdd400f0 100644 --- a/drivers/auxdisplay/Kconfig +++ b/drivers/auxdisplay/Kconfig @@ -1,7 +1,7 @@ # SPDX-License-Identifier: GPL-2.0 # # For a description of the syntax of this configuration file, -# see Documentation/kbuild/kconfig-language.txt. +# see Documentation/kbuild/kconfig-language.rst. # # Auxiliary display drivers configuration. # diff --git a/drivers/firmware/Kconfig b/drivers/firmware/Kconfig index 9026df923542..35078c6f334a 100644 --- a/drivers/firmware/Kconfig +++ b/drivers/firmware/Kconfig @@ -1,7 +1,7 @@ # SPDX-License-Identifier: GPL-2.0-only # # For a description of the syntax of this configuration file, -# see Documentation/kbuild/kconfig-language.txt. +# see Documentation/kbuild/kconfig-language.rst. # menu "Firmware Drivers" diff --git a/drivers/mtd/devices/Kconfig b/drivers/mtd/devices/Kconfig index ef0e476b2525..49abbc52457d 100644 --- a/drivers/mtd/devices/Kconfig +++ b/drivers/mtd/devices/Kconfig @@ -48,7 +48,7 @@ config MTD_MS02NV If you want to compile this driver as a module ( = code which can be inserted in and removed from the running kernel whenever you want), - say M here and read . + say M here and read . The module will be called ms02-nv. config MTD_DATAFLASH diff --git a/drivers/net/ethernet/smsc/Kconfig b/drivers/net/ethernet/smsc/Kconfig index d1b6a78557ec..9e1c3752b200 100644 --- a/drivers/net/ethernet/smsc/Kconfig +++ b/drivers/net/ethernet/smsc/Kconfig @@ -49,7 +49,7 @@ config SMC91X This driver is also available as a module ( = code which can be inserted in and removed from the running kernel whenever you want). The module will be called smc91x. If you want to compile it as a - module, say M here and read . + module, say M here and read . config PCMCIA_SMC91C92 tristate "SMC 91Cxx PCMCIA support" @@ -86,7 +86,7 @@ config SMC911X This driver is also available as a module. The module will be called smc911x. If you want to compile it as a module, say M - here and read + here and read config SMSC911X tristate "SMSC LAN911x/LAN921x families embedded ethernet support" @@ -121,6 +121,6 @@ config SMSC9420 This driver is also available as a module. The module will be called smsc9420. If you want to compile it as a module, say M - here and read + here and read endif # NET_VENDOR_SMSC diff --git a/drivers/net/wireless/intel/iwlegacy/Kconfig b/drivers/net/wireless/intel/iwlegacy/Kconfig index aa01c83e0060..e329fd7b09c0 100644 --- a/drivers/net/wireless/intel/iwlegacy/Kconfig +++ b/drivers/net/wireless/intel/iwlegacy/Kconfig @@ -32,7 +32,7 @@ config IWL4965 If you want to compile the driver as a module ( = code which can be inserted in and removed from the running kernel whenever you want), - say M here and read . The + say M here and read . The module will be called iwl4965. config IWL3945 @@ -58,7 +58,7 @@ config IWL3945 If you want to compile the driver as a module ( = code which can be inserted in and removed from the running kernel whenever you want), - say M here and read . The + say M here and read . The module will be called iwl3945. menu "iwl3945 / iwl4965 Debugging Options" diff --git a/drivers/net/wireless/intel/iwlwifi/Kconfig b/drivers/net/wireless/intel/iwlwifi/Kconfig index e5528189163f..235349a33a3c 100644 --- a/drivers/net/wireless/intel/iwlwifi/Kconfig +++ b/drivers/net/wireless/intel/iwlwifi/Kconfig @@ -40,7 +40,7 @@ config IWLWIFI If you want to compile the driver as a module ( = code which can be inserted in and removed from the running kernel whenever you want), - say M here and read . The + say M here and read . The module will be called iwlwifi. if IWLWIFI diff --git a/drivers/parport/Kconfig b/drivers/parport/Kconfig index 24189c3399e0..1791830e7a71 100644 --- a/drivers/parport/Kconfig +++ b/drivers/parport/Kconfig @@ -1,7 +1,7 @@ # SPDX-License-Identifier: GPL-2.0-only # # For a description of the syntax of this configuration file, -# see Documentation/kbuild/kconfig-language.txt. +# see Documentation/kbuild/kconfig-language.rst. # # Parport configuration. # diff --git a/drivers/scsi/Kconfig b/drivers/scsi/Kconfig index 61da513fc0ed..f31b6b780eaf 100644 --- a/drivers/scsi/Kconfig +++ b/drivers/scsi/Kconfig @@ -183,7 +183,7 @@ config CHR_DEV_SCH If you want to compile this as a module ( = code which can be inserted in and removed from the running kernel whenever you want), - say M here and read and + say M here and read and . The module will be called ch.o. If unsure, say N. @@ -1474,7 +1474,7 @@ config ZFCP This driver is also available as a module. This module will be called zfcp. If you want to compile it as a module, say M here - and read . + and read . config SCSI_PMCRAID tristate "PMC SIERRA Linux MaxRAID adapter support" diff --git a/drivers/staging/sm750fb/Kconfig b/drivers/staging/sm750fb/Kconfig index fb5a086bf9b1..8c0d8a873d5b 100644 --- a/drivers/staging/sm750fb/Kconfig +++ b/drivers/staging/sm750fb/Kconfig @@ -12,4 +12,4 @@ config FB_SM750 This driver is also available as a module. The module will be called sm750fb. If you want to compile it as a module, say M - here and read . + here and read . diff --git a/drivers/usb/misc/Kconfig b/drivers/usb/misc/Kconfig index c97f270338bf..4a88e1ca25c0 100644 --- a/drivers/usb/misc/Kconfig +++ b/drivers/usb/misc/Kconfig @@ -16,7 +16,7 @@ config USB_EMI62 This code is also available as a module ( = code which can be inserted in and removed from the running kernel whenever you want). The module will be called audio. If you want to compile it as a - module, say M here and read . + module, say M here and read . config USB_EMI26 tristate "EMI 2|6 USB Audio interface support" @@ -67,7 +67,7 @@ config USB_LEGOTOWER inserted in and removed from the running kernel whenever you want). The module will be called legousbtower. If you want to compile it as a module, say M here and read - . + . config USB_LCD tristate "USB LCD driver support" diff --git a/drivers/video/fbdev/Kconfig b/drivers/video/fbdev/Kconfig index 737b86328c9e..31ba91cb916a 100644 --- a/drivers/video/fbdev/Kconfig +++ b/drivers/video/fbdev/Kconfig @@ -289,7 +289,7 @@ config FB_ARMCLCD If you want to compile this as a module (=code which can be inserted into and removed from the running kernel), say M - here and read . The module + here and read . The module will be called amba-clcd. config FB_ACORN @@ -1752,7 +1752,7 @@ config FB_PXA This driver is also available as a module ( = code which can be inserted and removed from the running kernel whenever you want). The module will be called pxafb. If you want to compile it as a module, - say M here and read . + say M here and read . If unsure, say N. @@ -1833,7 +1833,7 @@ config FB_W100 This driver is also available as a module ( = code which can be inserted and removed from the running kernel whenever you want). The module will be called w100fb. If you want to compile it as a module, - say M here and read . + say M here and read . If unsure, say N. @@ -1862,7 +1862,7 @@ config FB_TMIO This driver is also available as a module ( = code which can be inserted and removed from the running kernel whenever you want). The module will be called tmiofb. If you want to compile it as a module, - say M here and read . + say M here and read . If unsure, say N. @@ -1908,7 +1908,7 @@ config FB_S3C2410 This driver is also available as a module ( = code which can be inserted and removed from the running kernel whenever you want). The module will be called s3c2410fb. If you want to compile it as a module, - say M here and read . + say M here and read . If unsure, say N. config FB_S3C2410_DEBUG @@ -1945,7 +1945,7 @@ config FB_SM501 This driver is also available as a module ( = code which can be inserted and removed from the running kernel whenever you want). The module will be called sm501fb. If you want to compile it as a module, - say M here and read . + say M here and read . If unsure, say N. @@ -2288,7 +2288,7 @@ config FB_SM712 This driver is also available as a module. The module will be called sm712fb. If you want to compile it as a module, say M - here and read . + here and read . source "drivers/video/fbdev/omap/Kconfig" source "drivers/video/fbdev/omap2/Kconfig" diff --git a/net/bridge/netfilter/Kconfig b/net/bridge/netfilter/Kconfig index c3ad90c43801..36a98d36d339 100644 --- a/net/bridge/netfilter/Kconfig +++ b/net/bridge/netfilter/Kconfig @@ -114,7 +114,7 @@ config BRIDGE_EBT_LIMIT equivalent of the iptables limit match. If you want to compile it as a module, say M here and read - . If unsure, say `N'. + . If unsure, say `N'. config BRIDGE_EBT_MARK tristate "ebt: mark filter support" diff --git a/net/ipv4/netfilter/Kconfig b/net/ipv4/netfilter/Kconfig index 3e6494269501..69e76d677f9e 100644 --- a/net/ipv4/netfilter/Kconfig +++ b/net/ipv4/netfilter/Kconfig @@ -308,7 +308,7 @@ config IP_NF_RAW and OUTPUT chains. If you want to compile it as a module, say M here and read - . If unsure, say `N'. + . If unsure, say `N'. # security table for MAC policy config IP_NF_SECURITY diff --git a/net/ipv6/netfilter/Kconfig b/net/ipv6/netfilter/Kconfig index f7c6f5be9f76..6120a7800975 100644 --- a/net/ipv6/netfilter/Kconfig +++ b/net/ipv6/netfilter/Kconfig @@ -241,7 +241,7 @@ config IP6_NF_RAW and OUTPUT chains. If you want to compile it as a module, say M here and read - . If unsure, say `N'. + . If unsure, say `N'. # security table for MAC policy config IP6_NF_SECURITY diff --git a/net/netfilter/Kconfig b/net/netfilter/Kconfig index 21025c2c605b..dd2af7be3eea 100644 --- a/net/netfilter/Kconfig +++ b/net/netfilter/Kconfig @@ -1056,7 +1056,7 @@ config NETFILTER_XT_TARGET_TRACE the tables, chains, rules. If you want to compile it as a module, say M here and read - . If unsure, say `N'. + . If unsure, say `N'. config NETFILTER_XT_TARGET_SECMARK tristate '"SECMARK" target support' @@ -1115,7 +1115,7 @@ config NETFILTER_XT_MATCH_ADDRTYPE eg. UNICAST, LOCAL, BROADCAST, ... If you want to compile it as a module, say M here and read - . If unsure, say `N'. + . If unsure, say `N'. config NETFILTER_XT_MATCH_BPF tristate '"bpf" match support' @@ -1160,7 +1160,7 @@ config NETFILTER_XT_MATCH_COMMENT comments in your iptables ruleset. If you want to compile it as a module, say M here and read - . If unsure, say `N'. + . If unsure, say `N'. config NETFILTER_XT_MATCH_CONNBYTES tristate '"connbytes" per-connection counter match support' @@ -1171,7 +1171,7 @@ config NETFILTER_XT_MATCH_CONNBYTES number of bytes and/or packets for each direction within a connection. If you want to compile it as a module, say M here and read - . If unsure, say `N'. + . If unsure, say `N'. config NETFILTER_XT_MATCH_CONNLABEL tristate '"connlabel" match support' @@ -1237,7 +1237,7 @@ config NETFILTER_XT_MATCH_DCCP and DCCP flags. If you want to compile it as a module, say M here and read - . If unsure, say `N'. + . If unsure, say `N'. config NETFILTER_XT_MATCH_DEVGROUP tristate '"devgroup" match support' @@ -1473,7 +1473,7 @@ config NETFILTER_XT_MATCH_QUOTA byte counter. If you want to compile it as a module, say M here and read - . If unsure, say `N'. + . If unsure, say `N'. config NETFILTER_XT_MATCH_RATEEST tristate '"rateest" match support' @@ -1497,7 +1497,7 @@ config NETFILTER_XT_MATCH_REALM in tc world. If you want to compile it as a module, say M here and read - . If unsure, say `N'. + . If unsure, say `N'. config NETFILTER_XT_MATCH_RECENT tristate '"recent" match support' @@ -1519,7 +1519,7 @@ config NETFILTER_XT_MATCH_SCTP and SCTP chunk types. If you want to compile it as a module, say M here and read - . If unsure, say `N'. + . If unsure, say `N'. config NETFILTER_XT_MATCH_SOCKET tristate '"socket" match support' diff --git a/net/tipc/Kconfig b/net/tipc/Kconfig index b93bb7bdb04a..b83e16ade4d2 100644 --- a/net/tipc/Kconfig +++ b/net/tipc/Kconfig @@ -17,7 +17,7 @@ menuconfig TIPC This protocol support is also available as a module ( = code which can be inserted in and removed from the running kernel whenever you want). The module will be called tipc. If you want to compile it - as a module, say M here and read . + as a module, say M here and read . If in doubt, say N. diff --git a/scripts/Kbuild.include b/scripts/Kbuild.include index f641bb0aa63f..ee58cde8ee3b 100644 --- a/scripts/Kbuild.include +++ b/scripts/Kbuild.include @@ -68,7 +68,7 @@ endef ###### # gcc support functions -# See documentation in Documentation/kbuild/makefiles.txt +# See documentation in Documentation/kbuild/makefiles.rst # cc-cross-prefix # Usage: CROSS_COMPILE := $(call cc-cross-prefix, m68k-linux-gnu- m68k-linux-) @@ -210,7 +210,7 @@ objectify = $(foreach o,$(1),$(if $(filter /%,$(o)),$(o),$(obj)/$(o))) # if_changed_dep - as if_changed, but uses fixdep to reveal dependencies # including used config symbols # if_changed_rule - as if_changed but execute rule instead -# See Documentation/kbuild/makefiles.txt for more info +# See Documentation/kbuild/makefiles.rst for more info ifneq ($(KBUILD_NOCMDDEP),1) # Check if both arguments are the same including their order. Result is empty diff --git a/scripts/Makefile.host b/scripts/Makefile.host index b6a54bdf0965..a316d368b697 100644 --- a/scripts/Makefile.host +++ b/scripts/Makefile.host @@ -6,7 +6,7 @@ # # Both C and C++ are supported, but preferred language is C for such utilities. # -# Sample syntax (see Documentation/kbuild/makefiles.txt for reference) +# Sample syntax (see Documentation/kbuild/makefiles.rst for reference) # hostprogs-y := bin2hex # Will compile bin2hex.c and create an executable named bin2hex # diff --git a/scripts/kconfig/symbol.c b/scripts/kconfig/symbol.c index 1f9266dadedf..09fd6fa18e1a 100644 --- a/scripts/kconfig/symbol.c +++ b/scripts/kconfig/symbol.c @@ -1114,7 +1114,7 @@ static void sym_check_print_recursive(struct symbol *last_sym) } fprintf(stderr, - "For a resolution refer to Documentation/kbuild/kconfig-language.txt\n" + "For a resolution refer to Documentation/kbuild/kconfig-language.rst\n" "subsection \"Kconfig recursive dependency limitations\"\n" "\n"); diff --git a/scripts/kconfig/tests/err_recursive_dep/expected_stderr b/scripts/kconfig/tests/err_recursive_dep/expected_stderr index 84679b104655..c9f4abf9a791 100644 --- a/scripts/kconfig/tests/err_recursive_dep/expected_stderr +++ b/scripts/kconfig/tests/err_recursive_dep/expected_stderr @@ -1,38 +1,38 @@ Kconfig:11:error: recursive dependency detected! Kconfig:11: symbol B is selected by B -For a resolution refer to Documentation/kbuild/kconfig-language.txt +For a resolution refer to Documentation/kbuild/kconfig-language.rst subsection "Kconfig recursive dependency limitations" Kconfig:5:error: recursive dependency detected! Kconfig:5: symbol A depends on A -For a resolution refer to Documentation/kbuild/kconfig-language.txt +For a resolution refer to Documentation/kbuild/kconfig-language.rst subsection "Kconfig recursive dependency limitations" Kconfig:17:error: recursive dependency detected! Kconfig:17: symbol C1 depends on C2 Kconfig:21: symbol C2 depends on C1 -For a resolution refer to Documentation/kbuild/kconfig-language.txt +For a resolution refer to Documentation/kbuild/kconfig-language.rst subsection "Kconfig recursive dependency limitations" Kconfig:32:error: recursive dependency detected! Kconfig:32: symbol D2 is selected by D1 Kconfig:27: symbol D1 depends on D2 -For a resolution refer to Documentation/kbuild/kconfig-language.txt +For a resolution refer to Documentation/kbuild/kconfig-language.rst subsection "Kconfig recursive dependency limitations" Kconfig:37:error: recursive dependency detected! Kconfig:37: symbol E1 depends on E2 Kconfig:42: symbol E2 is implied by E1 -For a resolution refer to Documentation/kbuild/kconfig-language.txt +For a resolution refer to Documentation/kbuild/kconfig-language.rst subsection "Kconfig recursive dependency limitations" Kconfig:60:error: recursive dependency detected! Kconfig:60: symbol G depends on G -For a resolution refer to Documentation/kbuild/kconfig-language.txt +For a resolution refer to Documentation/kbuild/kconfig-language.rst subsection "Kconfig recursive dependency limitations" Kconfig:51:error: recursive dependency detected! Kconfig:51: symbol F2 depends on F1 Kconfig:49: symbol F1 default value contains F2 -For a resolution refer to Documentation/kbuild/kconfig-language.txt +For a resolution refer to Documentation/kbuild/kconfig-language.rst subsection "Kconfig recursive dependency limitations" diff --git a/sound/oss/dmasound/Kconfig b/sound/oss/dmasound/Kconfig index 12e42165b4a5..1a3339859840 100644 --- a/sound/oss/dmasound/Kconfig +++ b/sound/oss/dmasound/Kconfig @@ -11,7 +11,7 @@ config DMASOUND_ATARI This driver is also available as a module ( = code which can be inserted in and removed from the running kernel whenever you want). If you want to compile it as a module, say M here and read - . + . config DMASOUND_PAULA tristate "Amiga DMA sound support" @@ -25,7 +25,7 @@ config DMASOUND_PAULA This driver is also available as a module ( = code which can be inserted in and removed from the running kernel whenever you want). If you want to compile it as a module, say M here and read - . + . config DMASOUND_Q40 tristate "Q40 sound support" @@ -39,7 +39,7 @@ config DMASOUND_Q40 This driver is also available as a module ( = code which can be inserted in and removed from the running kernel whenever you want). If you want to compile it as a module, say M here and read - . + . config DMASOUND tristate