run a null modem to a second machine and capture the output there
using your favourite communication program. Minicom works well.
-(3) Use Kdump (see Documentation/kdump/kdump.rst),
+(3) Use Kdump (see Documentation/admin-guide/kdump/kdump.rst),
extract the kernel ring buffer from old memory with using dmesg
- gdbmacro in Documentation/kdump/gdbmacros.txt.
+ gdbmacro in Documentation/admin-guide/kdump/gdbmacros.txt.
Finding the bug's location
--------------------------
ramoops
dynamic-debug-howto
init
+ kdump/index
perf/index
This is the beginning of a section with information of interest to
--- /dev/null
+#
+# This file contains a few gdb macros (user defined commands) to extract
+# useful information from kernel crashdump (kdump) like stack traces of
+# all the processes or a particular process and trapinfo.
+#
+# These macros can be used by copying this file in .gdbinit (put in home
+# directory or current directory) or by invoking gdb command with
+# --command=<command-file-name> option
+#
+# Credits:
+# Alexander Nyberg <alexn@telia.com>
+# V Srivatsa <vatsa@in.ibm.com>
+# Maneesh Soni <maneesh@in.ibm.com>
+#
+
+define bttnobp
+ set $tasks_off=((size_t)&((struct task_struct *)0)->tasks)
+ set $pid_off=((size_t)&((struct task_struct *)0)->thread_group.next)
+ set $init_t=&init_task
+ set $next_t=(((char *)($init_t->tasks).next) - $tasks_off)
+ set var $stacksize = sizeof(union thread_union)
+ while ($next_t != $init_t)
+ set $next_t=(struct task_struct *)$next_t
+ printf "\npid %d; comm %s:\n", $next_t.pid, $next_t.comm
+ printf "===================\n"
+ set var $stackp = $next_t.thread.sp
+ set var $stack_top = ($stackp & ~($stacksize - 1)) + $stacksize
+
+ while ($stackp < $stack_top)
+ if (*($stackp) > _stext && *($stackp) < _sinittext)
+ info symbol *($stackp)
+ end
+ set $stackp += 4
+ end
+ set $next_th=(((char *)$next_t->thread_group.next) - $pid_off)
+ while ($next_th != $next_t)
+ set $next_th=(struct task_struct *)$next_th
+ printf "\npid %d; comm %s:\n", $next_t.pid, $next_t.comm
+ printf "===================\n"
+ set var $stackp = $next_t.thread.sp
+ set var $stack_top = ($stackp & ~($stacksize - 1)) + stacksize
+
+ while ($stackp < $stack_top)
+ if (*($stackp) > _stext && *($stackp) < _sinittext)
+ info symbol *($stackp)
+ end
+ set $stackp += 4
+ end
+ set $next_th=(((char *)$next_th->thread_group.next) - $pid_off)
+ end
+ set $next_t=(char *)($next_t->tasks.next) - $tasks_off
+ end
+end
+document bttnobp
+ dump all thread stack traces on a kernel compiled with !CONFIG_FRAME_POINTER
+end
+
+define btthreadstack
+ set var $pid_task = $arg0
+
+ printf "\npid %d; comm %s:\n", $pid_task.pid, $pid_task.comm
+ printf "task struct: "
+ print $pid_task
+ printf "===================\n"
+ set var $stackp = $pid_task.thread.sp
+ set var $stacksize = sizeof(union thread_union)
+ set var $stack_top = ($stackp & ~($stacksize - 1)) + $stacksize
+ set var $stack_bot = ($stackp & ~($stacksize - 1))
+
+ set $stackp = *((unsigned long *) $stackp)
+ while (($stackp < $stack_top) && ($stackp > $stack_bot))
+ set var $addr = *(((unsigned long *) $stackp) + 1)
+ info symbol $addr
+ set $stackp = *((unsigned long *) $stackp)
+ end
+end
+document btthreadstack
+ dump a thread stack using the given task structure pointer
+end
+
+
+define btt
+ set $tasks_off=((size_t)&((struct task_struct *)0)->tasks)
+ set $pid_off=((size_t)&((struct task_struct *)0)->thread_group.next)
+ set $init_t=&init_task
+ set $next_t=(((char *)($init_t->tasks).next) - $tasks_off)
+ while ($next_t != $init_t)
+ set $next_t=(struct task_struct *)$next_t
+ btthreadstack $next_t
+
+ set $next_th=(((char *)$next_t->thread_group.next) - $pid_off)
+ while ($next_th != $next_t)
+ set $next_th=(struct task_struct *)$next_th
+ btthreadstack $next_th
+ set $next_th=(((char *)$next_th->thread_group.next) - $pid_off)
+ end
+ set $next_t=(char *)($next_t->tasks.next) - $tasks_off
+ end
+end
+document btt
+ dump all thread stack traces on a kernel compiled with CONFIG_FRAME_POINTER
+end
+
+define btpid
+ set var $pid = $arg0
+ set $tasks_off=((size_t)&((struct task_struct *)0)->tasks)
+ set $pid_off=((size_t)&((struct task_struct *)0)->thread_group.next)
+ set $init_t=&init_task
+ set $next_t=(((char *)($init_t->tasks).next) - $tasks_off)
+ set var $pid_task = 0
+
+ while ($next_t != $init_t)
+ set $next_t=(struct task_struct *)$next_t
+
+ if ($next_t.pid == $pid)
+ set $pid_task = $next_t
+ end
+
+ set $next_th=(((char *)$next_t->thread_group.next) - $pid_off)
+ while ($next_th != $next_t)
+ set $next_th=(struct task_struct *)$next_th
+ if ($next_th.pid == $pid)
+ set $pid_task = $next_th
+ end
+ set $next_th=(((char *)$next_th->thread_group.next) - $pid_off)
+ end
+ set $next_t=(char *)($next_t->tasks.next) - $tasks_off
+ end
+
+ btthreadstack $pid_task
+end
+document btpid
+ backtrace of pid
+end
+
+
+define trapinfo
+ set var $pid = $arg0
+ set $tasks_off=((size_t)&((struct task_struct *)0)->tasks)
+ set $pid_off=((size_t)&((struct task_struct *)0)->thread_group.next)
+ set $init_t=&init_task
+ set $next_t=(((char *)($init_t->tasks).next) - $tasks_off)
+ set var $pid_task = 0
+
+ while ($next_t != $init_t)
+ set $next_t=(struct task_struct *)$next_t
+
+ if ($next_t.pid == $pid)
+ set $pid_task = $next_t
+ end
+
+ set $next_th=(((char *)$next_t->thread_group.next) - $pid_off)
+ while ($next_th != $next_t)
+ set $next_th=(struct task_struct *)$next_th
+ if ($next_th.pid == $pid)
+ set $pid_task = $next_th
+ end
+ set $next_th=(((char *)$next_th->thread_group.next) - $pid_off)
+ end
+ set $next_t=(char *)($next_t->tasks.next) - $tasks_off
+ end
+
+ printf "Trapno %ld, cr2 0x%lx, error_code %ld\n", $pid_task.thread.trap_no, \
+ $pid_task.thread.cr2, $pid_task.thread.error_code
+
+end
+document trapinfo
+ Run info threads and lookup pid of thread #1
+ 'trapinfo <pid>' will tell you by which trap & possibly
+ address the kernel panicked.
+end
+
+define dump_log_idx
+ set $idx = $arg0
+ if ($argc > 1)
+ set $prev_flags = $arg1
+ else
+ set $prev_flags = 0
+ end
+ set $msg = ((struct printk_log *) (log_buf + $idx))
+ set $prefix = 1
+ set $newline = 1
+ set $log = log_buf + $idx + sizeof(*$msg)
+
+ # prev & LOG_CONT && !(msg->flags & LOG_PREIX)
+ if (($prev_flags & 8) && !($msg->flags & 4))
+ set $prefix = 0
+ end
+
+ # msg->flags & LOG_CONT
+ if ($msg->flags & 8)
+ # (prev & LOG_CONT && !(prev & LOG_NEWLINE))
+ if (($prev_flags & 8) && !($prev_flags & 2))
+ set $prefix = 0
+ end
+ # (!(msg->flags & LOG_NEWLINE))
+ if (!($msg->flags & 2))
+ set $newline = 0
+ end
+ end
+
+ if ($prefix)
+ printf "[%5lu.%06lu] ", $msg->ts_nsec / 1000000000, $msg->ts_nsec % 1000000000
+ end
+ if ($msg->text_len != 0)
+ eval "printf \"%%%d.%ds\", $log", $msg->text_len, $msg->text_len
+ end
+ if ($newline)
+ printf "\n"
+ end
+ if ($msg->dict_len > 0)
+ set $dict = $log + $msg->text_len
+ set $idx = 0
+ set $line = 1
+ while ($idx < $msg->dict_len)
+ if ($line)
+ printf " "
+ set $line = 0
+ end
+ set $c = $dict[$idx]
+ if ($c == '\0')
+ printf "\n"
+ set $line = 1
+ else
+ if ($c < ' ' || $c >= 127 || $c == '\\')
+ printf "\\x%02x", $c
+ else
+ printf "%c", $c
+ end
+ end
+ set $idx = $idx + 1
+ end
+ printf "\n"
+ end
+end
+document dump_log_idx
+ Dump a single log given its index in the log buffer. The first
+ parameter is the index into log_buf, the second is optional and
+ specified the previous log buffer's flags, used for properly
+ formatting continued lines.
+end
+
+define dmesg
+ set $i = log_first_idx
+ set $end_idx = log_first_idx
+ set $prev_flags = 0
+
+ while (1)
+ set $msg = ((struct printk_log *) (log_buf + $i))
+ if ($msg->len == 0)
+ set $i = 0
+ else
+ dump_log_idx $i $prev_flags
+ set $i = $i + $msg->len
+ set $prev_flags = $msg->flags
+ end
+ if ($i == $end_idx)
+ loop_break
+ end
+ end
+end
+document dmesg
+ print the kernel ring buffer
+end
--- /dev/null
+
+================================================================
+Documentation for Kdump - The kexec-based Crash Dumping Solution
+================================================================
+
+This document includes overview, setup and installation, and analysis
+information.
+
+.. toctree::
+ :maxdepth: 1
+
+ kdump
+ vmcoreinfo
+
+.. only:: subproject and html
+
+ Indices
+ =======
+
+ * :ref:`genindex`
--- /dev/null
+================================================================
+Documentation for Kdump - The kexec-based Crash Dumping Solution
+================================================================
+
+This document includes overview, setup and installation, and analysis
+information.
+
+Overview
+========
+
+Kdump uses kexec to quickly boot to a dump-capture kernel whenever a
+dump of the system kernel's memory needs to be taken (for example, when
+the system panics). The system kernel's memory image is preserved across
+the reboot and is accessible to the dump-capture kernel.
+
+You can use common commands, such as cp and scp, to copy the
+memory image to a dump file on the local disk, or across the network to
+a remote system.
+
+Kdump and kexec are currently supported on the x86, x86_64, ppc64, ia64,
+s390x, arm and arm64 architectures.
+
+When the system kernel boots, it reserves a small section of memory for
+the dump-capture kernel. This ensures that ongoing Direct Memory Access
+(DMA) from the system kernel does not corrupt the dump-capture kernel.
+The kexec -p command loads the dump-capture kernel into this reserved
+memory.
+
+On x86 machines, the first 640 KB of physical memory is needed to boot,
+regardless of where the kernel loads. Therefore, kexec backs up this
+region just before rebooting into the dump-capture kernel.
+
+Similarly on PPC64 machines first 32KB of physical memory is needed for
+booting regardless of where the kernel is loaded and to support 64K page
+size kexec backs up the first 64KB memory.
+
+For s390x, when kdump is triggered, the crashkernel region is exchanged
+with the region [0, crashkernel region size] and then the kdump kernel
+runs in [0, crashkernel region size]. Therefore no relocatable kernel is
+needed for s390x.
+
+All of the necessary information about the system kernel's core image is
+encoded in the ELF format, and stored in a reserved area of memory
+before a crash. The physical address of the start of the ELF header is
+passed to the dump-capture kernel through the elfcorehdr= boot
+parameter. Optionally the size of the ELF header can also be passed
+when using the elfcorehdr=[size[KMG]@]offset[KMG] syntax.
+
+
+With the dump-capture kernel, you can access the memory image through
+/proc/vmcore. This exports the dump as an ELF-format file that you can
+write out using file copy commands such as cp or scp. Further, you can
+use analysis tools such as the GNU Debugger (GDB) and the Crash tool to
+debug the dump file. This method ensures that the dump pages are correctly
+ordered.
+
+
+Setup and Installation
+======================
+
+Install kexec-tools
+-------------------
+
+1) Login as the root user.
+
+2) Download the kexec-tools user-space package from the following URL:
+
+http://kernel.org/pub/linux/utils/kernel/kexec/kexec-tools.tar.gz
+
+This is a symlink to the latest version.
+
+The latest kexec-tools git tree is available at:
+
+- git://git.kernel.org/pub/scm/utils/kernel/kexec/kexec-tools.git
+- http://www.kernel.org/pub/scm/utils/kernel/kexec/kexec-tools.git
+
+There is also a gitweb interface available at
+http://www.kernel.org/git/?p=utils/kernel/kexec/kexec-tools.git
+
+More information about kexec-tools can be found at
+http://horms.net/projects/kexec/
+
+3) Unpack the tarball with the tar command, as follows::
+
+ tar xvpzf kexec-tools.tar.gz
+
+4) Change to the kexec-tools directory, as follows::
+
+ cd kexec-tools-VERSION
+
+5) Configure the package, as follows::
+
+ ./configure
+
+6) Compile the package, as follows::
+
+ make
+
+7) Install the package, as follows::
+
+ make install
+
+
+Build the system and dump-capture kernels
+-----------------------------------------
+There are two possible methods of using Kdump.
+
+1) Build a separate custom dump-capture kernel for capturing the
+ kernel core dump.
+
+2) Or use the system kernel binary itself as dump-capture kernel and there is
+ no need to build a separate dump-capture kernel. This is possible
+ only with the architectures which support a relocatable kernel. As
+ of today, i386, x86_64, ppc64, ia64, arm and arm64 architectures support
+ relocatable kernel.
+
+Building a relocatable kernel is advantageous from the point of view that
+one does not have to build a second kernel for capturing the dump. But
+at the same time one might want to build a custom dump capture kernel
+suitable to his needs.
+
+Following are the configuration setting required for system and
+dump-capture kernels for enabling kdump support.
+
+System kernel config options
+----------------------------
+
+1) Enable "kexec system call" in "Processor type and features."::
+
+ CONFIG_KEXEC=y
+
+2) Enable "sysfs file system support" in "Filesystem" -> "Pseudo
+ filesystems." This is usually enabled by default::
+
+ CONFIG_SYSFS=y
+
+ Note that "sysfs file system support" might not appear in the "Pseudo
+ filesystems" menu if "Configure standard kernel features (for small
+ systems)" is not enabled in "General Setup." In this case, check the
+ .config file itself to ensure that sysfs is turned on, as follows::
+
+ grep 'CONFIG_SYSFS' .config
+
+3) Enable "Compile the kernel with debug info" in "Kernel hacking."::
+
+ CONFIG_DEBUG_INFO=Y
+
+ This causes the kernel to be built with debug symbols. The dump
+ analysis tools require a vmlinux with debug symbols in order to read
+ and analyze a dump file.
+
+Dump-capture kernel config options (Arch Independent)
+-----------------------------------------------------
+
+1) Enable "kernel crash dumps" support under "Processor type and
+ features"::
+
+ CONFIG_CRASH_DUMP=y
+
+2) Enable "/proc/vmcore support" under "Filesystems" -> "Pseudo filesystems"::
+
+ CONFIG_PROC_VMCORE=y
+
+ (CONFIG_PROC_VMCORE is set by default when CONFIG_CRASH_DUMP is selected.)
+
+Dump-capture kernel config options (Arch Dependent, i386 and x86_64)
+--------------------------------------------------------------------
+
+1) On i386, enable high memory support under "Processor type and
+ features"::
+
+ CONFIG_HIGHMEM64G=y
+
+ or::
+
+ CONFIG_HIGHMEM4G
+
+2) On i386 and x86_64, disable symmetric multi-processing support
+ under "Processor type and features"::
+
+ CONFIG_SMP=n
+
+ (If CONFIG_SMP=y, then specify maxcpus=1 on the kernel command line
+ when loading the dump-capture kernel, see section "Load the Dump-capture
+ Kernel".)
+
+3) If one wants to build and use a relocatable kernel,
+ Enable "Build a relocatable kernel" support under "Processor type and
+ features"::
+
+ CONFIG_RELOCATABLE=y
+
+4) Use a suitable value for "Physical address where the kernel is
+ loaded" (under "Processor type and features"). This only appears when
+ "kernel crash dumps" is enabled. A suitable value depends upon
+ whether kernel is relocatable or not.
+
+ If you are using a relocatable kernel use CONFIG_PHYSICAL_START=0x100000
+ This will compile the kernel for physical address 1MB, but given the fact
+ kernel is relocatable, it can be run from any physical address hence
+ kexec boot loader will load it in memory region reserved for dump-capture
+ kernel.
+
+ Otherwise it should be the start of memory region reserved for
+ second kernel using boot parameter "crashkernel=Y@X". Here X is
+ start of memory region reserved for dump-capture kernel.
+ Generally X is 16MB (0x1000000). So you can set
+ CONFIG_PHYSICAL_START=0x1000000
+
+5) Make and install the kernel and its modules. DO NOT add this kernel
+ to the boot loader configuration files.
+
+Dump-capture kernel config options (Arch Dependent, ppc64)
+----------------------------------------------------------
+
+1) Enable "Build a kdump crash kernel" support under "Kernel" options::
+
+ CONFIG_CRASH_DUMP=y
+
+2) Enable "Build a relocatable kernel" support::
+
+ CONFIG_RELOCATABLE=y
+
+ Make and install the kernel and its modules.
+
+Dump-capture kernel config options (Arch Dependent, ia64)
+----------------------------------------------------------
+
+- No specific options are required to create a dump-capture kernel
+ for ia64, other than those specified in the arch independent section
+ above. This means that it is possible to use the system kernel
+ as a dump-capture kernel if desired.
+
+ The crashkernel region can be automatically placed by the system
+ kernel at run time. This is done by specifying the base address as 0,
+ or omitting it all together::
+
+ crashkernel=256M@0
+
+ or::
+
+ crashkernel=256M
+
+ If the start address is specified, note that the start address of the
+ kernel will be aligned to 64Mb, so if the start address is not then
+ any space below the alignment point will be wasted.
+
+Dump-capture kernel config options (Arch Dependent, arm)
+----------------------------------------------------------
+
+- To use a relocatable kernel,
+ Enable "AUTO_ZRELADDR" support under "Boot" options::
+
+ AUTO_ZRELADDR=y
+
+Dump-capture kernel config options (Arch Dependent, arm64)
+----------------------------------------------------------
+
+- Please note that kvm of the dump-capture kernel will not be enabled
+ on non-VHE systems even if it is configured. This is because the CPU
+ will not be reset to EL2 on panic.
+
+Extended crashkernel syntax
+===========================
+
+While the "crashkernel=size[@offset]" syntax is sufficient for most
+configurations, sometimes it's handy to have the reserved memory dependent
+on the value of System RAM -- that's mostly for distributors that pre-setup
+the kernel command line to avoid a unbootable system after some memory has
+been removed from the machine.
+
+The syntax is::
+
+ crashkernel=<range1>:<size1>[,<range2>:<size2>,...][@offset]
+ range=start-[end]
+
+For example::
+
+ crashkernel=512M-2G:64M,2G-:128M
+
+This would mean:
+
+ 1) if the RAM is smaller than 512M, then don't reserve anything
+ (this is the "rescue" case)
+ 2) if the RAM size is between 512M and 2G (exclusive), then reserve 64M
+ 3) if the RAM size is larger than 2G, then reserve 128M
+
+
+
+Boot into System Kernel
+=======================
+
+1) Update the boot loader (such as grub, yaboot, or lilo) configuration
+ files as necessary.
+
+2) Boot the system kernel with the boot parameter "crashkernel=Y@X",
+ where Y specifies how much memory to reserve for the dump-capture kernel
+ and X specifies the beginning of this reserved memory. For example,
+ "crashkernel=64M@16M" tells the system kernel to reserve 64 MB of memory
+ starting at physical address 0x01000000 (16MB) for the dump-capture kernel.
+
+ On x86 and x86_64, use "crashkernel=64M@16M".
+
+ On ppc64, use "crashkernel=128M@32M".
+
+ On ia64, 256M@256M is a generous value that typically works.
+ The region may be automatically placed on ia64, see the
+ dump-capture kernel config option notes above.
+ If use sparse memory, the size should be rounded to GRANULE boundaries.
+
+ On s390x, typically use "crashkernel=xxM". The value of xx is dependent
+ on the memory consumption of the kdump system. In general this is not
+ dependent on the memory size of the production system.
+
+ On arm, the use of "crashkernel=Y@X" is no longer necessary; the
+ kernel will automatically locate the crash kernel image within the
+ first 512MB of RAM if X is not given.
+
+ On arm64, use "crashkernel=Y[@X]". Note that the start address of
+ the kernel, X if explicitly specified, must be aligned to 2MiB (0x200000).
+
+Load the Dump-capture Kernel
+============================
+
+After booting to the system kernel, dump-capture kernel needs to be
+loaded.
+
+Based on the architecture and type of image (relocatable or not), one
+can choose to load the uncompressed vmlinux or compressed bzImage/vmlinuz
+of dump-capture kernel. Following is the summary.
+
+For i386 and x86_64:
+
+ - Use vmlinux if kernel is not relocatable.
+ - Use bzImage/vmlinuz if kernel is relocatable.
+
+For ppc64:
+
+ - Use vmlinux
+
+For ia64:
+
+ - Use vmlinux or vmlinuz.gz
+
+For s390x:
+
+ - Use image or bzImage
+
+For arm:
+
+ - Use zImage
+
+For arm64:
+
+ - Use vmlinux or Image
+
+If you are using an uncompressed vmlinux image then use following command
+to load dump-capture kernel::
+
+ kexec -p <dump-capture-kernel-vmlinux-image> \
+ --initrd=<initrd-for-dump-capture-kernel> --args-linux \
+ --append="root=<root-dev> <arch-specific-options>"
+
+If you are using a compressed bzImage/vmlinuz, then use following command
+to load dump-capture kernel::
+
+ kexec -p <dump-capture-kernel-bzImage> \
+ --initrd=<initrd-for-dump-capture-kernel> \
+ --append="root=<root-dev> <arch-specific-options>"
+
+If you are using a compressed zImage, then use following command
+to load dump-capture kernel::
+
+ kexec --type zImage -p <dump-capture-kernel-bzImage> \
+ --initrd=<initrd-for-dump-capture-kernel> \
+ --dtb=<dtb-for-dump-capture-kernel> \
+ --append="root=<root-dev> <arch-specific-options>"
+
+If you are using an uncompressed Image, then use following command
+to load dump-capture kernel::
+
+ kexec -p <dump-capture-kernel-Image> \
+ --initrd=<initrd-for-dump-capture-kernel> \
+ --append="root=<root-dev> <arch-specific-options>"
+
+Please note, that --args-linux does not need to be specified for ia64.
+It is planned to make this a no-op on that architecture, but for now
+it should be omitted
+
+Following are the arch specific command line options to be used while
+loading dump-capture kernel.
+
+For i386, x86_64 and ia64:
+
+ "1 irqpoll maxcpus=1 reset_devices"
+
+For ppc64:
+
+ "1 maxcpus=1 noirqdistrib reset_devices"
+
+For s390x:
+
+ "1 maxcpus=1 cgroup_disable=memory"
+
+For arm:
+
+ "1 maxcpus=1 reset_devices"
+
+For arm64:
+
+ "1 maxcpus=1 reset_devices"
+
+Notes on loading the dump-capture kernel:
+
+* By default, the ELF headers are stored in ELF64 format to support
+ systems with more than 4GB memory. On i386, kexec automatically checks if
+ the physical RAM size exceeds the 4 GB limit and if not, uses ELF32.
+ So, on non-PAE systems, ELF32 is always used.
+
+ The --elf32-core-headers option can be used to force the generation of ELF32
+ headers. This is necessary because GDB currently cannot open vmcore files
+ with ELF64 headers on 32-bit systems.
+
+* The "irqpoll" boot parameter reduces driver initialization failures
+ due to shared interrupts in the dump-capture kernel.
+
+* You must specify <root-dev> in the format corresponding to the root
+ device name in the output of mount command.
+
+* Boot parameter "1" boots the dump-capture kernel into single-user
+ mode without networking. If you want networking, use "3".
+
+* We generally don't have to bring up a SMP kernel just to capture the
+ dump. Hence generally it is useful either to build a UP dump-capture
+ kernel or specify maxcpus=1 option while loading dump-capture kernel.
+ Note, though maxcpus always works, you had better replace it with
+ nr_cpus to save memory if supported by the current ARCH, such as x86.
+
+* You should enable multi-cpu support in dump-capture kernel if you intend
+ to use multi-thread programs with it, such as parallel dump feature of
+ makedumpfile. Otherwise, the multi-thread program may have a great
+ performance degradation. To enable multi-cpu support, you should bring up an
+ SMP dump-capture kernel and specify maxcpus/nr_cpus, disable_cpu_apicid=[X]
+ options while loading it.
+
+* For s390x there are two kdump modes: If a ELF header is specified with
+ the elfcorehdr= kernel parameter, it is used by the kdump kernel as it
+ is done on all other architectures. If no elfcorehdr= kernel parameter is
+ specified, the s390x kdump kernel dynamically creates the header. The
+ second mode has the advantage that for CPU and memory hotplug, kdump has
+ not to be reloaded with kexec_load().
+
+* For s390x systems with many attached devices the "cio_ignore" kernel
+ parameter should be used for the kdump kernel in order to prevent allocation
+ of kernel memory for devices that are not relevant for kdump. The same
+ applies to systems that use SCSI/FCP devices. In that case the
+ "allow_lun_scan" zfcp module parameter should be set to zero before
+ setting FCP devices online.
+
+Kernel Panic
+============
+
+After successfully loading the dump-capture kernel as previously
+described, the system will reboot into the dump-capture kernel if a
+system crash is triggered. Trigger points are located in panic(),
+die(), die_nmi() and in the sysrq handler (ALT-SysRq-c).
+
+The following conditions will execute a crash trigger point:
+
+If a hard lockup is detected and "NMI watchdog" is configured, the system
+will boot into the dump-capture kernel ( die_nmi() ).
+
+If die() is called, and it happens to be a thread with pid 0 or 1, or die()
+is called inside interrupt context or die() is called and panic_on_oops is set,
+the system will boot into the dump-capture kernel.
+
+On powerpc systems when a soft-reset is generated, die() is called by all cpus
+and the system will boot into the dump-capture kernel.
+
+For testing purposes, you can trigger a crash by using "ALT-SysRq-c",
+"echo c > /proc/sysrq-trigger" or write a module to force the panic.
+
+Write Out the Dump File
+=======================
+
+After the dump-capture kernel is booted, write out the dump file with
+the following command::
+
+ cp /proc/vmcore <dump-file>
+
+
+Analysis
+========
+
+Before analyzing the dump image, you should reboot into a stable kernel.
+
+You can do limited analysis using GDB on the dump file copied out of
+/proc/vmcore. Use the debug vmlinux built with -g and run the following
+command::
+
+ gdb vmlinux <dump-file>
+
+Stack trace for the task on processor 0, register display, and memory
+display work fine.
+
+Note: GDB cannot analyze core files generated in ELF64 format for x86.
+On systems with a maximum of 4GB of memory, you can generate
+ELF32-format headers using the --elf32-core-headers kernel option on the
+dump kernel.
+
+You can also use the Crash utility to analyze dump files in Kdump
+format. Crash is available on Dave Anderson's site at the following URL:
+
+ http://people.redhat.com/~anderson/
+
+Trigger Kdump on WARN()
+=======================
+
+The kernel parameter, panic_on_warn, calls panic() in all WARN() paths. This
+will cause a kdump to occur at the panic() call. In cases where a user wants
+to specify this during runtime, /proc/sys/kernel/panic_on_warn can be set to 1
+to achieve the same behaviour.
+
+Contact
+=======
+
+- Vivek Goyal (vgoyal@redhat.com)
+- Maneesh Soni (maneesh@in.ibm.com)
+
+GDB macros
+==========
+
+.. include:: gdbmacros.txt
+ :literal:
--- /dev/null
+==========
+VMCOREINFO
+==========
+
+What is it?
+===========
+
+VMCOREINFO is a special ELF note section. It contains various
+information from the kernel like structure size, page size, symbol
+values, field offsets, etc. These data are packed into an ELF note
+section and used by user-space tools like crash and makedumpfile to
+analyze a kernel's memory layout.
+
+Common variables
+================
+
+init_uts_ns.name.release
+------------------------
+
+The version of the Linux kernel. Used to find the corresponding source
+code from which the kernel has been built. For example, crash uses it to
+find the corresponding vmlinux in order to process vmcore.
+
+PAGE_SIZE
+---------
+
+The size of a page. It is the smallest unit of data used by the memory
+management facilities. It is usually 4096 bytes of size and a page is
+aligned on 4096 bytes. Used for computing page addresses.
+
+init_uts_ns
+-----------
+
+The UTS namespace which is used to isolate two specific elements of the
+system that relate to the uname(2) system call. It is named after the
+data structure used to store information returned by the uname(2) system
+call.
+
+User-space tools can get the kernel name, host name, kernel release
+number, kernel version, architecture name and OS type from it.
+
+node_online_map
+---------------
+
+An array node_states[N_ONLINE] which represents the set of online nodes
+in a system, one bit position per node number. Used to keep track of
+which nodes are in the system and online.
+
+swapper_pg_dir
+--------------
+
+The global page directory pointer of the kernel. Used to translate
+virtual to physical addresses.
+
+_stext
+------
+
+Defines the beginning of the text section. In general, _stext indicates
+the kernel start address. Used to convert a virtual address from the
+direct kernel map to a physical address.
+
+vmap_area_list
+--------------
+
+Stores the virtual area list. makedumpfile gets the vmalloc start value
+from this variable and its value is necessary for vmalloc translation.
+
+mem_map
+-------
+
+Physical addresses are translated to struct pages by treating them as
+an index into the mem_map array. Right-shifting a physical address
+PAGE_SHIFT bits converts it into a page frame number which is an index
+into that mem_map array.
+
+Used to map an address to the corresponding struct page.
+
+contig_page_data
+----------------
+
+Makedumpfile gets the pglist_data structure from this symbol, which is
+used to describe the memory layout.
+
+User-space tools use this to exclude free pages when dumping memory.
+
+mem_section|(mem_section, NR_SECTION_ROOTS)|(mem_section, section_mem_map)
+--------------------------------------------------------------------------
+
+The address of the mem_section array, its length, structure size, and
+the section_mem_map offset.
+
+It exists in the sparse memory mapping model, and it is also somewhat
+similar to the mem_map variable, both of them are used to translate an
+address.
+
+page
+----
+
+The size of a page structure. struct page is an important data structure
+and it is widely used to compute contiguous memory.
+
+pglist_data
+-----------
+
+The size of a pglist_data structure. This value is used to check if the
+pglist_data structure is valid. It is also used for checking the memory
+type.
+
+zone
+----
+
+The size of a zone structure. This value is used to check if the zone
+structure has been found. It is also used for excluding free pages.
+
+free_area
+---------
+
+The size of a free_area structure. It indicates whether the free_area
+structure is valid or not. Useful when excluding free pages.
+
+list_head
+---------
+
+The size of a list_head structure. Used when iterating lists in a
+post-mortem analysis session.
+
+nodemask_t
+----------
+
+The size of a nodemask_t type. Used to compute the number of online
+nodes.
+
+(page, flags|_refcount|mapping|lru|_mapcount|private|compound_dtor|compound_order|compound_head)
+-------------------------------------------------------------------------------------------------
+
+User-space tools compute their values based on the offset of these
+variables. The variables are used when excluding unnecessary pages.
+
+(pglist_data, node_zones|nr_zones|node_mem_map|node_start_pfn|node_spanned_pages|node_id)
+-----------------------------------------------------------------------------------------
+
+On NUMA machines, each NUMA node has a pg_data_t to describe its memory
+layout. On UMA machines there is a single pglist_data which describes the
+whole memory.
+
+These values are used to check the memory type and to compute the
+virtual address for memory map.
+
+(zone, free_area|vm_stat|spanned_pages)
+---------------------------------------
+
+Each node is divided into a number of blocks called zones which
+represent ranges within memory. A zone is described by a structure zone.
+
+User-space tools compute required values based on the offset of these
+variables.
+
+(free_area, free_list)
+----------------------
+
+Offset of the free_list's member. This value is used to compute the number
+of free pages.
+
+Each zone has a free_area structure array called free_area[MAX_ORDER].
+The free_list represents a linked list of free page blocks.
+
+(list_head, next|prev)
+----------------------
+
+Offsets of the list_head's members. list_head is used to define a
+circular linked list. User-space tools need these in order to traverse
+lists.
+
+(vmap_area, va_start|list)
+--------------------------
+
+Offsets of the vmap_area's members. They carry vmalloc-specific
+information. Makedumpfile gets the start address of the vmalloc region
+from this.
+
+(zone.free_area, MAX_ORDER)
+---------------------------
+
+Free areas descriptor. User-space tools use this value to iterate the
+free_area ranges. MAX_ORDER is used by the zone buddy allocator.
+
+log_first_idx
+-------------
+
+Index of the first record stored in the buffer log_buf. Used by
+user-space tools to read the strings in the log_buf.
+
+log_buf
+-------
+
+Console output is written to the ring buffer log_buf at index
+log_first_idx. Used to get the kernel log.
+
+log_buf_len
+-----------
+
+log_buf's length.
+
+clear_idx
+---------
+
+The index that the next printk() record to read after the last clear
+command. It indicates the first record after the last SYSLOG_ACTION
+_CLEAR, like issued by 'dmesg -c'. Used by user-space tools to dump
+the dmesg log.
+
+log_next_idx
+------------
+
+The index of the next record to store in the buffer log_buf. Used to
+compute the index of the current buffer position.
+
+printk_log
+----------
+
+The size of a structure printk_log. Used to compute the size of
+messages, and extract dmesg log. It encapsulates header information for
+log_buf, such as timestamp, syslog level, etc.
+
+(printk_log, ts_nsec|len|text_len|dict_len)
+-------------------------------------------
+
+It represents field offsets in struct printk_log. User space tools
+parse it and check whether the values of printk_log's members have been
+changed.
+
+(free_area.free_list, MIGRATE_TYPES)
+------------------------------------
+
+The number of migrate types for pages. The free_list is described by the
+array. Used by tools to compute the number of free pages.
+
+NR_FREE_PAGES
+-------------
+
+On linux-2.6.21 or later, the number of free pages is in
+vm_stat[NR_FREE_PAGES]. Used to get the number of free pages.
+
+PG_lru|PG_private|PG_swapcache|PG_swapbacked|PG_slab|PG_hwpoision|PG_head_mask
+------------------------------------------------------------------------------
+
+Page attributes. These flags are used to filter various unnecessary for
+dumping pages.
+
+PAGE_BUDDY_MAPCOUNT_VALUE(~PG_buddy)|PAGE_OFFLINE_MAPCOUNT_VALUE(~PG_offline)
+-----------------------------------------------------------------------------
+
+More page attributes. These flags are used to filter various unnecessary for
+dumping pages.
+
+
+HUGETLB_PAGE_DTOR
+-----------------
+
+The HUGETLB_PAGE_DTOR flag denotes hugetlbfs pages. Makedumpfile
+excludes these pages.
+
+x86_64
+======
+
+phys_base
+---------
+
+Used to convert the virtual address of an exported kernel symbol to its
+corresponding physical address.
+
+init_top_pgt
+------------
+
+Used to walk through the whole page table and convert virtual addresses
+to physical addresses. The init_top_pgt is somewhat similar to
+swapper_pg_dir, but it is only used in x86_64.
+
+pgtable_l5_enabled
+------------------
+
+User-space tools need to know whether the crash kernel was in 5-level
+paging mode.
+
+node_data
+---------
+
+This is a struct pglist_data array and stores all NUMA nodes
+information. Makedumpfile gets the pglist_data structure from it.
+
+(node_data, MAX_NUMNODES)
+-------------------------
+
+The maximum number of nodes in system.
+
+KERNELOFFSET
+------------
+
+The kernel randomization offset. Used to compute the page offset. If
+KASLR is disabled, this value is zero.
+
+KERNEL_IMAGE_SIZE
+-----------------
+
+Currently unused by Makedumpfile. Used to compute the module virtual
+address by Crash.
+
+sme_mask
+--------
+
+AMD-specific with SME support: it indicates the secure memory encryption
+mask. Makedumpfile tools need to know whether the crash kernel was
+encrypted. If SME is enabled in the first kernel, the crash kernel's
+page table entries (pgd/pud/pmd/pte) contain the memory encryption
+mask. This is used to remove the SME mask and obtain the true physical
+address.
+
+Currently, sme_mask stores the value of the C-bit position. If needed,
+additional SME-relevant info can be placed in that variable.
+
+For example::
+
+ [ misc ][ enc bit ][ other misc SME info ]
+ 0000_0000_0000_0000_1000_0000_0000_0000_0000_0000_..._0000
+ 63 59 55 51 47 43 39 35 31 27 ... 3
+
+x86_32
+======
+
+X86_PAE
+-------
+
+Denotes whether physical address extensions are enabled. It has the cost
+of a higher page table lookup overhead, and also consumes more page
+table space per process. Used to check whether PAE was enabled in the
+crash kernel when converting virtual addresses to physical addresses.
+
+ia64
+====
+
+pgdat_list|(pgdat_list, MAX_NUMNODES)
+-------------------------------------
+
+pg_data_t array storing all NUMA nodes information. MAX_NUMNODES
+indicates the number of the nodes.
+
+node_memblk|(node_memblk, NR_NODE_MEMBLKS)
+------------------------------------------
+
+List of node memory chunks. Filled when parsing the SRAT table to obtain
+information about memory nodes. NR_NODE_MEMBLKS indicates the number of
+node memory chunks.
+
+These values are used to compute the number of nodes the crashed kernel used.
+
+node_memblk_s|(node_memblk_s, start_paddr)|(node_memblk_s, size)
+----------------------------------------------------------------
+
+The size of a struct node_memblk_s and the offsets of the
+node_memblk_s's members. Used to compute the number of nodes.
+
+PGTABLE_3|PGTABLE_4
+-------------------
+
+User-space tools need to know whether the crash kernel was in 3-level or
+4-level paging mode. Used to distinguish the page table.
+
+ARM64
+=====
+
+VA_BITS
+-------
+
+The maximum number of bits for virtual addresses. Used to compute the
+virtual memory ranges.
+
+kimage_voffset
+--------------
+
+The offset between the kernel virtual and physical mappings. Used to
+translate virtual to physical addresses.
+
+PHYS_OFFSET
+-----------
+
+Indicates the physical address of the start of memory. Similar to
+kimage_voffset, which is used to translate virtual to physical
+addresses.
+
+KERNELOFFSET
+------------
+
+The kernel randomization offset. Used to compute the page offset. If
+KASLR is disabled, this value is zero.
+
+arm
+===
+
+ARM_LPAE
+--------
+
+It indicates whether the crash kernel supports large physical address
+extensions. Used to translate virtual to physical addresses.
+
+s390
+====
+
+lowcore_ptr
+-----------
+
+An array with a pointer to the lowcore of every CPU. Used to print the
+psw and all registers information.
+
+high_memory
+-----------
+
+Used to get the vmalloc_start address from the high_memory symbol.
+
+(lowcore_ptr, NR_CPUS)
+----------------------
+
+The maximum number of CPUs.
+
+powerpc
+=======
+
+
+node_data|(node_data, MAX_NUMNODES)
+-----------------------------------
+
+See above.
+
+contig_page_data
+----------------
+
+See above.
+
+vmemmap_list
+------------
+
+The vmemmap_list maintains the entire vmemmap physical mapping. Used
+to get vmemmap list count and populated vmemmap regions info. If the
+vmemmap address translation information is stored in the crash kernel,
+it is used to translate vmemmap kernel virtual addresses.
+
+mmu_vmemmap_psize
+-----------------
+
+The size of a page. Used to translate virtual to physical addresses.
+
+mmu_psize_defs
+--------------
+
+Page size definitions, i.e. 4k, 64k, or 16M.
+
+Used to make vtop translations.
+
+vmemmap_backing|(vmemmap_backing, list)|(vmemmap_backing, phys)|(vmemmap_backing, virt_addr)
+--------------------------------------------------------------------------------------------
+
+The vmemmap virtual address space management does not have a traditional
+page table to track which virtual struct pages are backed by a physical
+mapping. The virtual to physical mappings are tracked in a simple linked
+list format.
+
+User-space tools need to know the offset of list, phys and virt_addr
+when computing the count of vmemmap regions.
+
+mmu_psize_def|(mmu_psize_def, shift)
+------------------------------------
+
+The size of a struct mmu_psize_def and the offset of mmu_psize_def's
+member.
+
+Used in vtop translations.
+
+sh
+==
+
+node_data|(node_data, MAX_NUMNODES)
+-----------------------------------
+
+See above.
+
+X2TLB
+-----
+
+Indicates whether the crashed kernel enabled SH extended mode.
[KNL, x86_64] select a region under 4G first, and
fall back to reserve region above 4G when '@offset'
hasn't been specified.
- See Documentation/kdump/kdump.rst for further details.
+ See Documentation/admin-guide/kdump/kdump.rst for further details.
crashkernel=range1:size1[,range2:size2,...][@offset]
[KNL] Same as above, but depends on the memory
in the running system. The syntax of range is
start-[end] where start and end are both
a memory unit (amount[KMG]). See also
- Documentation/kdump/kdump.rst for an example.
+ Documentation/admin-guide/kdump/kdump.rst for an example.
crashkernel=size[KMG],high
[KNL, x86_64] range could be above 4G. Allow kernel
Specifies physical address of start of kernel core
image elf header and optionally the size. Generally
kexec loader will pass this option to capture kernel.
- See Documentation/kdump/kdump.rst for details.
+ See Documentation/admin-guide/kdump/kdump.rst for details.
enable_mtrr_cleanup [X86]
The kernel tries to adjust MTRR layout from continuous
+++ /dev/null
-#
-# This file contains a few gdb macros (user defined commands) to extract
-# useful information from kernel crashdump (kdump) like stack traces of
-# all the processes or a particular process and trapinfo.
-#
-# These macros can be used by copying this file in .gdbinit (put in home
-# directory or current directory) or by invoking gdb command with
-# --command=<command-file-name> option
-#
-# Credits:
-# Alexander Nyberg <alexn@telia.com>
-# V Srivatsa <vatsa@in.ibm.com>
-# Maneesh Soni <maneesh@in.ibm.com>
-#
-
-define bttnobp
- set $tasks_off=((size_t)&((struct task_struct *)0)->tasks)
- set $pid_off=((size_t)&((struct task_struct *)0)->thread_group.next)
- set $init_t=&init_task
- set $next_t=(((char *)($init_t->tasks).next) - $tasks_off)
- set var $stacksize = sizeof(union thread_union)
- while ($next_t != $init_t)
- set $next_t=(struct task_struct *)$next_t
- printf "\npid %d; comm %s:\n", $next_t.pid, $next_t.comm
- printf "===================\n"
- set var $stackp = $next_t.thread.sp
- set var $stack_top = ($stackp & ~($stacksize - 1)) + $stacksize
-
- while ($stackp < $stack_top)
- if (*($stackp) > _stext && *($stackp) < _sinittext)
- info symbol *($stackp)
- end
- set $stackp += 4
- end
- set $next_th=(((char *)$next_t->thread_group.next) - $pid_off)
- while ($next_th != $next_t)
- set $next_th=(struct task_struct *)$next_th
- printf "\npid %d; comm %s:\n", $next_t.pid, $next_t.comm
- printf "===================\n"
- set var $stackp = $next_t.thread.sp
- set var $stack_top = ($stackp & ~($stacksize - 1)) + stacksize
-
- while ($stackp < $stack_top)
- if (*($stackp) > _stext && *($stackp) < _sinittext)
- info symbol *($stackp)
- end
- set $stackp += 4
- end
- set $next_th=(((char *)$next_th->thread_group.next) - $pid_off)
- end
- set $next_t=(char *)($next_t->tasks.next) - $tasks_off
- end
-end
-document bttnobp
- dump all thread stack traces on a kernel compiled with !CONFIG_FRAME_POINTER
-end
-
-define btthreadstack
- set var $pid_task = $arg0
-
- printf "\npid %d; comm %s:\n", $pid_task.pid, $pid_task.comm
- printf "task struct: "
- print $pid_task
- printf "===================\n"
- set var $stackp = $pid_task.thread.sp
- set var $stacksize = sizeof(union thread_union)
- set var $stack_top = ($stackp & ~($stacksize - 1)) + $stacksize
- set var $stack_bot = ($stackp & ~($stacksize - 1))
-
- set $stackp = *((unsigned long *) $stackp)
- while (($stackp < $stack_top) && ($stackp > $stack_bot))
- set var $addr = *(((unsigned long *) $stackp) + 1)
- info symbol $addr
- set $stackp = *((unsigned long *) $stackp)
- end
-end
-document btthreadstack
- dump a thread stack using the given task structure pointer
-end
-
-
-define btt
- set $tasks_off=((size_t)&((struct task_struct *)0)->tasks)
- set $pid_off=((size_t)&((struct task_struct *)0)->thread_group.next)
- set $init_t=&init_task
- set $next_t=(((char *)($init_t->tasks).next) - $tasks_off)
- while ($next_t != $init_t)
- set $next_t=(struct task_struct *)$next_t
- btthreadstack $next_t
-
- set $next_th=(((char *)$next_t->thread_group.next) - $pid_off)
- while ($next_th != $next_t)
- set $next_th=(struct task_struct *)$next_th
- btthreadstack $next_th
- set $next_th=(((char *)$next_th->thread_group.next) - $pid_off)
- end
- set $next_t=(char *)($next_t->tasks.next) - $tasks_off
- end
-end
-document btt
- dump all thread stack traces on a kernel compiled with CONFIG_FRAME_POINTER
-end
-
-define btpid
- set var $pid = $arg0
- set $tasks_off=((size_t)&((struct task_struct *)0)->tasks)
- set $pid_off=((size_t)&((struct task_struct *)0)->thread_group.next)
- set $init_t=&init_task
- set $next_t=(((char *)($init_t->tasks).next) - $tasks_off)
- set var $pid_task = 0
-
- while ($next_t != $init_t)
- set $next_t=(struct task_struct *)$next_t
-
- if ($next_t.pid == $pid)
- set $pid_task = $next_t
- end
-
- set $next_th=(((char *)$next_t->thread_group.next) - $pid_off)
- while ($next_th != $next_t)
- set $next_th=(struct task_struct *)$next_th
- if ($next_th.pid == $pid)
- set $pid_task = $next_th
- end
- set $next_th=(((char *)$next_th->thread_group.next) - $pid_off)
- end
- set $next_t=(char *)($next_t->tasks.next) - $tasks_off
- end
-
- btthreadstack $pid_task
-end
-document btpid
- backtrace of pid
-end
-
-
-define trapinfo
- set var $pid = $arg0
- set $tasks_off=((size_t)&((struct task_struct *)0)->tasks)
- set $pid_off=((size_t)&((struct task_struct *)0)->thread_group.next)
- set $init_t=&init_task
- set $next_t=(((char *)($init_t->tasks).next) - $tasks_off)
- set var $pid_task = 0
-
- while ($next_t != $init_t)
- set $next_t=(struct task_struct *)$next_t
-
- if ($next_t.pid == $pid)
- set $pid_task = $next_t
- end
-
- set $next_th=(((char *)$next_t->thread_group.next) - $pid_off)
- while ($next_th != $next_t)
- set $next_th=(struct task_struct *)$next_th
- if ($next_th.pid == $pid)
- set $pid_task = $next_th
- end
- set $next_th=(((char *)$next_th->thread_group.next) - $pid_off)
- end
- set $next_t=(char *)($next_t->tasks.next) - $tasks_off
- end
-
- printf "Trapno %ld, cr2 0x%lx, error_code %ld\n", $pid_task.thread.trap_no, \
- $pid_task.thread.cr2, $pid_task.thread.error_code
-
-end
-document trapinfo
- Run info threads and lookup pid of thread #1
- 'trapinfo <pid>' will tell you by which trap & possibly
- address the kernel panicked.
-end
-
-define dump_log_idx
- set $idx = $arg0
- if ($argc > 1)
- set $prev_flags = $arg1
- else
- set $prev_flags = 0
- end
- set $msg = ((struct printk_log *) (log_buf + $idx))
- set $prefix = 1
- set $newline = 1
- set $log = log_buf + $idx + sizeof(*$msg)
-
- # prev & LOG_CONT && !(msg->flags & LOG_PREIX)
- if (($prev_flags & 8) && !($msg->flags & 4))
- set $prefix = 0
- end
-
- # msg->flags & LOG_CONT
- if ($msg->flags & 8)
- # (prev & LOG_CONT && !(prev & LOG_NEWLINE))
- if (($prev_flags & 8) && !($prev_flags & 2))
- set $prefix = 0
- end
- # (!(msg->flags & LOG_NEWLINE))
- if (!($msg->flags & 2))
- set $newline = 0
- end
- end
-
- if ($prefix)
- printf "[%5lu.%06lu] ", $msg->ts_nsec / 1000000000, $msg->ts_nsec % 1000000000
- end
- if ($msg->text_len != 0)
- eval "printf \"%%%d.%ds\", $log", $msg->text_len, $msg->text_len
- end
- if ($newline)
- printf "\n"
- end
- if ($msg->dict_len > 0)
- set $dict = $log + $msg->text_len
- set $idx = 0
- set $line = 1
- while ($idx < $msg->dict_len)
- if ($line)
- printf " "
- set $line = 0
- end
- set $c = $dict[$idx]
- if ($c == '\0')
- printf "\n"
- set $line = 1
- else
- if ($c < ' ' || $c >= 127 || $c == '\\')
- printf "\\x%02x", $c
- else
- printf "%c", $c
- end
- end
- set $idx = $idx + 1
- end
- printf "\n"
- end
-end
-document dump_log_idx
- Dump a single log given its index in the log buffer. The first
- parameter is the index into log_buf, the second is optional and
- specified the previous log buffer's flags, used for properly
- formatting continued lines.
-end
-
-define dmesg
- set $i = log_first_idx
- set $end_idx = log_first_idx
- set $prev_flags = 0
-
- while (1)
- set $msg = ((struct printk_log *) (log_buf + $i))
- if ($msg->len == 0)
- set $i = 0
- else
- dump_log_idx $i $prev_flags
- set $i = $i + $msg->len
- set $prev_flags = $msg->flags
- end
- if ($i == $end_idx)
- loop_break
- end
- end
-end
-document dmesg
- print the kernel ring buffer
-end
+++ /dev/null
-:orphan:
-
-================================================================
-Documentation for Kdump - The kexec-based Crash Dumping Solution
-================================================================
-
-This document includes overview, setup and installation, and analysis
-information.
-
-.. toctree::
- :maxdepth: 1
-
- kdump
- vmcoreinfo
-
-.. only:: subproject and html
-
- Indices
- =======
-
- * :ref:`genindex`
+++ /dev/null
-================================================================
-Documentation for Kdump - The kexec-based Crash Dumping Solution
-================================================================
-
-This document includes overview, setup and installation, and analysis
-information.
-
-Overview
-========
-
-Kdump uses kexec to quickly boot to a dump-capture kernel whenever a
-dump of the system kernel's memory needs to be taken (for example, when
-the system panics). The system kernel's memory image is preserved across
-the reboot and is accessible to the dump-capture kernel.
-
-You can use common commands, such as cp and scp, to copy the
-memory image to a dump file on the local disk, or across the network to
-a remote system.
-
-Kdump and kexec are currently supported on the x86, x86_64, ppc64, ia64,
-s390x, arm and arm64 architectures.
-
-When the system kernel boots, it reserves a small section of memory for
-the dump-capture kernel. This ensures that ongoing Direct Memory Access
-(DMA) from the system kernel does not corrupt the dump-capture kernel.
-The kexec -p command loads the dump-capture kernel into this reserved
-memory.
-
-On x86 machines, the first 640 KB of physical memory is needed to boot,
-regardless of where the kernel loads. Therefore, kexec backs up this
-region just before rebooting into the dump-capture kernel.
-
-Similarly on PPC64 machines first 32KB of physical memory is needed for
-booting regardless of where the kernel is loaded and to support 64K page
-size kexec backs up the first 64KB memory.
-
-For s390x, when kdump is triggered, the crashkernel region is exchanged
-with the region [0, crashkernel region size] and then the kdump kernel
-runs in [0, crashkernel region size]. Therefore no relocatable kernel is
-needed for s390x.
-
-All of the necessary information about the system kernel's core image is
-encoded in the ELF format, and stored in a reserved area of memory
-before a crash. The physical address of the start of the ELF header is
-passed to the dump-capture kernel through the elfcorehdr= boot
-parameter. Optionally the size of the ELF header can also be passed
-when using the elfcorehdr=[size[KMG]@]offset[KMG] syntax.
-
-
-With the dump-capture kernel, you can access the memory image through
-/proc/vmcore. This exports the dump as an ELF-format file that you can
-write out using file copy commands such as cp or scp. Further, you can
-use analysis tools such as the GNU Debugger (GDB) and the Crash tool to
-debug the dump file. This method ensures that the dump pages are correctly
-ordered.
-
-
-Setup and Installation
-======================
-
-Install kexec-tools
--------------------
-
-1) Login as the root user.
-
-2) Download the kexec-tools user-space package from the following URL:
-
-http://kernel.org/pub/linux/utils/kernel/kexec/kexec-tools.tar.gz
-
-This is a symlink to the latest version.
-
-The latest kexec-tools git tree is available at:
-
-- git://git.kernel.org/pub/scm/utils/kernel/kexec/kexec-tools.git
-- http://www.kernel.org/pub/scm/utils/kernel/kexec/kexec-tools.git
-
-There is also a gitweb interface available at
-http://www.kernel.org/git/?p=utils/kernel/kexec/kexec-tools.git
-
-More information about kexec-tools can be found at
-http://horms.net/projects/kexec/
-
-3) Unpack the tarball with the tar command, as follows::
-
- tar xvpzf kexec-tools.tar.gz
-
-4) Change to the kexec-tools directory, as follows::
-
- cd kexec-tools-VERSION
-
-5) Configure the package, as follows::
-
- ./configure
-
-6) Compile the package, as follows::
-
- make
-
-7) Install the package, as follows::
-
- make install
-
-
-Build the system and dump-capture kernels
------------------------------------------
-There are two possible methods of using Kdump.
-
-1) Build a separate custom dump-capture kernel for capturing the
- kernel core dump.
-
-2) Or use the system kernel binary itself as dump-capture kernel and there is
- no need to build a separate dump-capture kernel. This is possible
- only with the architectures which support a relocatable kernel. As
- of today, i386, x86_64, ppc64, ia64, arm and arm64 architectures support
- relocatable kernel.
-
-Building a relocatable kernel is advantageous from the point of view that
-one does not have to build a second kernel for capturing the dump. But
-at the same time one might want to build a custom dump capture kernel
-suitable to his needs.
-
-Following are the configuration setting required for system and
-dump-capture kernels for enabling kdump support.
-
-System kernel config options
-----------------------------
-
-1) Enable "kexec system call" in "Processor type and features."::
-
- CONFIG_KEXEC=y
-
-2) Enable "sysfs file system support" in "Filesystem" -> "Pseudo
- filesystems." This is usually enabled by default::
-
- CONFIG_SYSFS=y
-
- Note that "sysfs file system support" might not appear in the "Pseudo
- filesystems" menu if "Configure standard kernel features (for small
- systems)" is not enabled in "General Setup." In this case, check the
- .config file itself to ensure that sysfs is turned on, as follows::
-
- grep 'CONFIG_SYSFS' .config
-
-3) Enable "Compile the kernel with debug info" in "Kernel hacking."::
-
- CONFIG_DEBUG_INFO=Y
-
- This causes the kernel to be built with debug symbols. The dump
- analysis tools require a vmlinux with debug symbols in order to read
- and analyze a dump file.
-
-Dump-capture kernel config options (Arch Independent)
------------------------------------------------------
-
-1) Enable "kernel crash dumps" support under "Processor type and
- features"::
-
- CONFIG_CRASH_DUMP=y
-
-2) Enable "/proc/vmcore support" under "Filesystems" -> "Pseudo filesystems"::
-
- CONFIG_PROC_VMCORE=y
-
- (CONFIG_PROC_VMCORE is set by default when CONFIG_CRASH_DUMP is selected.)
-
-Dump-capture kernel config options (Arch Dependent, i386 and x86_64)
---------------------------------------------------------------------
-
-1) On i386, enable high memory support under "Processor type and
- features"::
-
- CONFIG_HIGHMEM64G=y
-
- or::
-
- CONFIG_HIGHMEM4G
-
-2) On i386 and x86_64, disable symmetric multi-processing support
- under "Processor type and features"::
-
- CONFIG_SMP=n
-
- (If CONFIG_SMP=y, then specify maxcpus=1 on the kernel command line
- when loading the dump-capture kernel, see section "Load the Dump-capture
- Kernel".)
-
-3) If one wants to build and use a relocatable kernel,
- Enable "Build a relocatable kernel" support under "Processor type and
- features"::
-
- CONFIG_RELOCATABLE=y
-
-4) Use a suitable value for "Physical address where the kernel is
- loaded" (under "Processor type and features"). This only appears when
- "kernel crash dumps" is enabled. A suitable value depends upon
- whether kernel is relocatable or not.
-
- If you are using a relocatable kernel use CONFIG_PHYSICAL_START=0x100000
- This will compile the kernel for physical address 1MB, but given the fact
- kernel is relocatable, it can be run from any physical address hence
- kexec boot loader will load it in memory region reserved for dump-capture
- kernel.
-
- Otherwise it should be the start of memory region reserved for
- second kernel using boot parameter "crashkernel=Y@X". Here X is
- start of memory region reserved for dump-capture kernel.
- Generally X is 16MB (0x1000000). So you can set
- CONFIG_PHYSICAL_START=0x1000000
-
-5) Make and install the kernel and its modules. DO NOT add this kernel
- to the boot loader configuration files.
-
-Dump-capture kernel config options (Arch Dependent, ppc64)
-----------------------------------------------------------
-
-1) Enable "Build a kdump crash kernel" support under "Kernel" options::
-
- CONFIG_CRASH_DUMP=y
-
-2) Enable "Build a relocatable kernel" support::
-
- CONFIG_RELOCATABLE=y
-
- Make and install the kernel and its modules.
-
-Dump-capture kernel config options (Arch Dependent, ia64)
-----------------------------------------------------------
-
-- No specific options are required to create a dump-capture kernel
- for ia64, other than those specified in the arch independent section
- above. This means that it is possible to use the system kernel
- as a dump-capture kernel if desired.
-
- The crashkernel region can be automatically placed by the system
- kernel at run time. This is done by specifying the base address as 0,
- or omitting it all together::
-
- crashkernel=256M@0
-
- or::
-
- crashkernel=256M
-
- If the start address is specified, note that the start address of the
- kernel will be aligned to 64Mb, so if the start address is not then
- any space below the alignment point will be wasted.
-
-Dump-capture kernel config options (Arch Dependent, arm)
-----------------------------------------------------------
-
-- To use a relocatable kernel,
- Enable "AUTO_ZRELADDR" support under "Boot" options::
-
- AUTO_ZRELADDR=y
-
-Dump-capture kernel config options (Arch Dependent, arm64)
-----------------------------------------------------------
-
-- Please note that kvm of the dump-capture kernel will not be enabled
- on non-VHE systems even if it is configured. This is because the CPU
- will not be reset to EL2 on panic.
-
-Extended crashkernel syntax
-===========================
-
-While the "crashkernel=size[@offset]" syntax is sufficient for most
-configurations, sometimes it's handy to have the reserved memory dependent
-on the value of System RAM -- that's mostly for distributors that pre-setup
-the kernel command line to avoid a unbootable system after some memory has
-been removed from the machine.
-
-The syntax is::
-
- crashkernel=<range1>:<size1>[,<range2>:<size2>,...][@offset]
- range=start-[end]
-
-For example::
-
- crashkernel=512M-2G:64M,2G-:128M
-
-This would mean:
-
- 1) if the RAM is smaller than 512M, then don't reserve anything
- (this is the "rescue" case)
- 2) if the RAM size is between 512M and 2G (exclusive), then reserve 64M
- 3) if the RAM size is larger than 2G, then reserve 128M
-
-
-
-Boot into System Kernel
-=======================
-
-1) Update the boot loader (such as grub, yaboot, or lilo) configuration
- files as necessary.
-
-2) Boot the system kernel with the boot parameter "crashkernel=Y@X",
- where Y specifies how much memory to reserve for the dump-capture kernel
- and X specifies the beginning of this reserved memory. For example,
- "crashkernel=64M@16M" tells the system kernel to reserve 64 MB of memory
- starting at physical address 0x01000000 (16MB) for the dump-capture kernel.
-
- On x86 and x86_64, use "crashkernel=64M@16M".
-
- On ppc64, use "crashkernel=128M@32M".
-
- On ia64, 256M@256M is a generous value that typically works.
- The region may be automatically placed on ia64, see the
- dump-capture kernel config option notes above.
- If use sparse memory, the size should be rounded to GRANULE boundaries.
-
- On s390x, typically use "crashkernel=xxM". The value of xx is dependent
- on the memory consumption of the kdump system. In general this is not
- dependent on the memory size of the production system.
-
- On arm, the use of "crashkernel=Y@X" is no longer necessary; the
- kernel will automatically locate the crash kernel image within the
- first 512MB of RAM if X is not given.
-
- On arm64, use "crashkernel=Y[@X]". Note that the start address of
- the kernel, X if explicitly specified, must be aligned to 2MiB (0x200000).
-
-Load the Dump-capture Kernel
-============================
-
-After booting to the system kernel, dump-capture kernel needs to be
-loaded.
-
-Based on the architecture and type of image (relocatable or not), one
-can choose to load the uncompressed vmlinux or compressed bzImage/vmlinuz
-of dump-capture kernel. Following is the summary.
-
-For i386 and x86_64:
-
- - Use vmlinux if kernel is not relocatable.
- - Use bzImage/vmlinuz if kernel is relocatable.
-
-For ppc64:
-
- - Use vmlinux
-
-For ia64:
-
- - Use vmlinux or vmlinuz.gz
-
-For s390x:
-
- - Use image or bzImage
-
-For arm:
-
- - Use zImage
-
-For arm64:
-
- - Use vmlinux or Image
-
-If you are using an uncompressed vmlinux image then use following command
-to load dump-capture kernel::
-
- kexec -p <dump-capture-kernel-vmlinux-image> \
- --initrd=<initrd-for-dump-capture-kernel> --args-linux \
- --append="root=<root-dev> <arch-specific-options>"
-
-If you are using a compressed bzImage/vmlinuz, then use following command
-to load dump-capture kernel::
-
- kexec -p <dump-capture-kernel-bzImage> \
- --initrd=<initrd-for-dump-capture-kernel> \
- --append="root=<root-dev> <arch-specific-options>"
-
-If you are using a compressed zImage, then use following command
-to load dump-capture kernel::
-
- kexec --type zImage -p <dump-capture-kernel-bzImage> \
- --initrd=<initrd-for-dump-capture-kernel> \
- --dtb=<dtb-for-dump-capture-kernel> \
- --append="root=<root-dev> <arch-specific-options>"
-
-If you are using an uncompressed Image, then use following command
-to load dump-capture kernel::
-
- kexec -p <dump-capture-kernel-Image> \
- --initrd=<initrd-for-dump-capture-kernel> \
- --append="root=<root-dev> <arch-specific-options>"
-
-Please note, that --args-linux does not need to be specified for ia64.
-It is planned to make this a no-op on that architecture, but for now
-it should be omitted
-
-Following are the arch specific command line options to be used while
-loading dump-capture kernel.
-
-For i386, x86_64 and ia64:
-
- "1 irqpoll maxcpus=1 reset_devices"
-
-For ppc64:
-
- "1 maxcpus=1 noirqdistrib reset_devices"
-
-For s390x:
-
- "1 maxcpus=1 cgroup_disable=memory"
-
-For arm:
-
- "1 maxcpus=1 reset_devices"
-
-For arm64:
-
- "1 maxcpus=1 reset_devices"
-
-Notes on loading the dump-capture kernel:
-
-* By default, the ELF headers are stored in ELF64 format to support
- systems with more than 4GB memory. On i386, kexec automatically checks if
- the physical RAM size exceeds the 4 GB limit and if not, uses ELF32.
- So, on non-PAE systems, ELF32 is always used.
-
- The --elf32-core-headers option can be used to force the generation of ELF32
- headers. This is necessary because GDB currently cannot open vmcore files
- with ELF64 headers on 32-bit systems.
-
-* The "irqpoll" boot parameter reduces driver initialization failures
- due to shared interrupts in the dump-capture kernel.
-
-* You must specify <root-dev> in the format corresponding to the root
- device name in the output of mount command.
-
-* Boot parameter "1" boots the dump-capture kernel into single-user
- mode without networking. If you want networking, use "3".
-
-* We generally don't have to bring up a SMP kernel just to capture the
- dump. Hence generally it is useful either to build a UP dump-capture
- kernel or specify maxcpus=1 option while loading dump-capture kernel.
- Note, though maxcpus always works, you had better replace it with
- nr_cpus to save memory if supported by the current ARCH, such as x86.
-
-* You should enable multi-cpu support in dump-capture kernel if you intend
- to use multi-thread programs with it, such as parallel dump feature of
- makedumpfile. Otherwise, the multi-thread program may have a great
- performance degradation. To enable multi-cpu support, you should bring up an
- SMP dump-capture kernel and specify maxcpus/nr_cpus, disable_cpu_apicid=[X]
- options while loading it.
-
-* For s390x there are two kdump modes: If a ELF header is specified with
- the elfcorehdr= kernel parameter, it is used by the kdump kernel as it
- is done on all other architectures. If no elfcorehdr= kernel parameter is
- specified, the s390x kdump kernel dynamically creates the header. The
- second mode has the advantage that for CPU and memory hotplug, kdump has
- not to be reloaded with kexec_load().
-
-* For s390x systems with many attached devices the "cio_ignore" kernel
- parameter should be used for the kdump kernel in order to prevent allocation
- of kernel memory for devices that are not relevant for kdump. The same
- applies to systems that use SCSI/FCP devices. In that case the
- "allow_lun_scan" zfcp module parameter should be set to zero before
- setting FCP devices online.
-
-Kernel Panic
-============
-
-After successfully loading the dump-capture kernel as previously
-described, the system will reboot into the dump-capture kernel if a
-system crash is triggered. Trigger points are located in panic(),
-die(), die_nmi() and in the sysrq handler (ALT-SysRq-c).
-
-The following conditions will execute a crash trigger point:
-
-If a hard lockup is detected and "NMI watchdog" is configured, the system
-will boot into the dump-capture kernel ( die_nmi() ).
-
-If die() is called, and it happens to be a thread with pid 0 or 1, or die()
-is called inside interrupt context or die() is called and panic_on_oops is set,
-the system will boot into the dump-capture kernel.
-
-On powerpc systems when a soft-reset is generated, die() is called by all cpus
-and the system will boot into the dump-capture kernel.
-
-For testing purposes, you can trigger a crash by using "ALT-SysRq-c",
-"echo c > /proc/sysrq-trigger" or write a module to force the panic.
-
-Write Out the Dump File
-=======================
-
-After the dump-capture kernel is booted, write out the dump file with
-the following command::
-
- cp /proc/vmcore <dump-file>
-
-
-Analysis
-========
-
-Before analyzing the dump image, you should reboot into a stable kernel.
-
-You can do limited analysis using GDB on the dump file copied out of
-/proc/vmcore. Use the debug vmlinux built with -g and run the following
-command::
-
- gdb vmlinux <dump-file>
-
-Stack trace for the task on processor 0, register display, and memory
-display work fine.
-
-Note: GDB cannot analyze core files generated in ELF64 format for x86.
-On systems with a maximum of 4GB of memory, you can generate
-ELF32-format headers using the --elf32-core-headers kernel option on the
-dump kernel.
-
-You can also use the Crash utility to analyze dump files in Kdump
-format. Crash is available on Dave Anderson's site at the following URL:
-
- http://people.redhat.com/~anderson/
-
-Trigger Kdump on WARN()
-=======================
-
-The kernel parameter, panic_on_warn, calls panic() in all WARN() paths. This
-will cause a kdump to occur at the panic() call. In cases where a user wants
-to specify this during runtime, /proc/sys/kernel/panic_on_warn can be set to 1
-to achieve the same behaviour.
-
-Contact
-=======
-
-- Vivek Goyal (vgoyal@redhat.com)
-- Maneesh Soni (maneesh@in.ibm.com)
-
-GDB macros
-==========
-
-.. include:: gdbmacros.txt
- :literal:
+++ /dev/null
-==========
-VMCOREINFO
-==========
-
-What is it?
-===========
-
-VMCOREINFO is a special ELF note section. It contains various
-information from the kernel like structure size, page size, symbol
-values, field offsets, etc. These data are packed into an ELF note
-section and used by user-space tools like crash and makedumpfile to
-analyze a kernel's memory layout.
-
-Common variables
-================
-
-init_uts_ns.name.release
-------------------------
-
-The version of the Linux kernel. Used to find the corresponding source
-code from which the kernel has been built. For example, crash uses it to
-find the corresponding vmlinux in order to process vmcore.
-
-PAGE_SIZE
----------
-
-The size of a page. It is the smallest unit of data used by the memory
-management facilities. It is usually 4096 bytes of size and a page is
-aligned on 4096 bytes. Used for computing page addresses.
-
-init_uts_ns
------------
-
-The UTS namespace which is used to isolate two specific elements of the
-system that relate to the uname(2) system call. It is named after the
-data structure used to store information returned by the uname(2) system
-call.
-
-User-space tools can get the kernel name, host name, kernel release
-number, kernel version, architecture name and OS type from it.
-
-node_online_map
----------------
-
-An array node_states[N_ONLINE] which represents the set of online nodes
-in a system, one bit position per node number. Used to keep track of
-which nodes are in the system and online.
-
-swapper_pg_dir
---------------
-
-The global page directory pointer of the kernel. Used to translate
-virtual to physical addresses.
-
-_stext
-------
-
-Defines the beginning of the text section. In general, _stext indicates
-the kernel start address. Used to convert a virtual address from the
-direct kernel map to a physical address.
-
-vmap_area_list
---------------
-
-Stores the virtual area list. makedumpfile gets the vmalloc start value
-from this variable and its value is necessary for vmalloc translation.
-
-mem_map
--------
-
-Physical addresses are translated to struct pages by treating them as
-an index into the mem_map array. Right-shifting a physical address
-PAGE_SHIFT bits converts it into a page frame number which is an index
-into that mem_map array.
-
-Used to map an address to the corresponding struct page.
-
-contig_page_data
-----------------
-
-Makedumpfile gets the pglist_data structure from this symbol, which is
-used to describe the memory layout.
-
-User-space tools use this to exclude free pages when dumping memory.
-
-mem_section|(mem_section, NR_SECTION_ROOTS)|(mem_section, section_mem_map)
---------------------------------------------------------------------------
-
-The address of the mem_section array, its length, structure size, and
-the section_mem_map offset.
-
-It exists in the sparse memory mapping model, and it is also somewhat
-similar to the mem_map variable, both of them are used to translate an
-address.
-
-page
-----
-
-The size of a page structure. struct page is an important data structure
-and it is widely used to compute contiguous memory.
-
-pglist_data
------------
-
-The size of a pglist_data structure. This value is used to check if the
-pglist_data structure is valid. It is also used for checking the memory
-type.
-
-zone
-----
-
-The size of a zone structure. This value is used to check if the zone
-structure has been found. It is also used for excluding free pages.
-
-free_area
----------
-
-The size of a free_area structure. It indicates whether the free_area
-structure is valid or not. Useful when excluding free pages.
-
-list_head
----------
-
-The size of a list_head structure. Used when iterating lists in a
-post-mortem analysis session.
-
-nodemask_t
-----------
-
-The size of a nodemask_t type. Used to compute the number of online
-nodes.
-
-(page, flags|_refcount|mapping|lru|_mapcount|private|compound_dtor|compound_order|compound_head)
--------------------------------------------------------------------------------------------------
-
-User-space tools compute their values based on the offset of these
-variables. The variables are used when excluding unnecessary pages.
-
-(pglist_data, node_zones|nr_zones|node_mem_map|node_start_pfn|node_spanned_pages|node_id)
------------------------------------------------------------------------------------------
-
-On NUMA machines, each NUMA node has a pg_data_t to describe its memory
-layout. On UMA machines there is a single pglist_data which describes the
-whole memory.
-
-These values are used to check the memory type and to compute the
-virtual address for memory map.
-
-(zone, free_area|vm_stat|spanned_pages)
----------------------------------------
-
-Each node is divided into a number of blocks called zones which
-represent ranges within memory. A zone is described by a structure zone.
-
-User-space tools compute required values based on the offset of these
-variables.
-
-(free_area, free_list)
-----------------------
-
-Offset of the free_list's member. This value is used to compute the number
-of free pages.
-
-Each zone has a free_area structure array called free_area[MAX_ORDER].
-The free_list represents a linked list of free page blocks.
-
-(list_head, next|prev)
-----------------------
-
-Offsets of the list_head's members. list_head is used to define a
-circular linked list. User-space tools need these in order to traverse
-lists.
-
-(vmap_area, va_start|list)
---------------------------
-
-Offsets of the vmap_area's members. They carry vmalloc-specific
-information. Makedumpfile gets the start address of the vmalloc region
-from this.
-
-(zone.free_area, MAX_ORDER)
----------------------------
-
-Free areas descriptor. User-space tools use this value to iterate the
-free_area ranges. MAX_ORDER is used by the zone buddy allocator.
-
-log_first_idx
--------------
-
-Index of the first record stored in the buffer log_buf. Used by
-user-space tools to read the strings in the log_buf.
-
-log_buf
--------
-
-Console output is written to the ring buffer log_buf at index
-log_first_idx. Used to get the kernel log.
-
-log_buf_len
------------
-
-log_buf's length.
-
-clear_idx
----------
-
-The index that the next printk() record to read after the last clear
-command. It indicates the first record after the last SYSLOG_ACTION
-_CLEAR, like issued by 'dmesg -c'. Used by user-space tools to dump
-the dmesg log.
-
-log_next_idx
-------------
-
-The index of the next record to store in the buffer log_buf. Used to
-compute the index of the current buffer position.
-
-printk_log
-----------
-
-The size of a structure printk_log. Used to compute the size of
-messages, and extract dmesg log. It encapsulates header information for
-log_buf, such as timestamp, syslog level, etc.
-
-(printk_log, ts_nsec|len|text_len|dict_len)
--------------------------------------------
-
-It represents field offsets in struct printk_log. User space tools
-parse it and check whether the values of printk_log's members have been
-changed.
-
-(free_area.free_list, MIGRATE_TYPES)
-------------------------------------
-
-The number of migrate types for pages. The free_list is described by the
-array. Used by tools to compute the number of free pages.
-
-NR_FREE_PAGES
--------------
-
-On linux-2.6.21 or later, the number of free pages is in
-vm_stat[NR_FREE_PAGES]. Used to get the number of free pages.
-
-PG_lru|PG_private|PG_swapcache|PG_swapbacked|PG_slab|PG_hwpoision|PG_head_mask
-------------------------------------------------------------------------------
-
-Page attributes. These flags are used to filter various unnecessary for
-dumping pages.
-
-PAGE_BUDDY_MAPCOUNT_VALUE(~PG_buddy)|PAGE_OFFLINE_MAPCOUNT_VALUE(~PG_offline)
------------------------------------------------------------------------------
-
-More page attributes. These flags are used to filter various unnecessary for
-dumping pages.
-
-
-HUGETLB_PAGE_DTOR
------------------
-
-The HUGETLB_PAGE_DTOR flag denotes hugetlbfs pages. Makedumpfile
-excludes these pages.
-
-x86_64
-======
-
-phys_base
----------
-
-Used to convert the virtual address of an exported kernel symbol to its
-corresponding physical address.
-
-init_top_pgt
-------------
-
-Used to walk through the whole page table and convert virtual addresses
-to physical addresses. The init_top_pgt is somewhat similar to
-swapper_pg_dir, but it is only used in x86_64.
-
-pgtable_l5_enabled
-------------------
-
-User-space tools need to know whether the crash kernel was in 5-level
-paging mode.
-
-node_data
----------
-
-This is a struct pglist_data array and stores all NUMA nodes
-information. Makedumpfile gets the pglist_data structure from it.
-
-(node_data, MAX_NUMNODES)
--------------------------
-
-The maximum number of nodes in system.
-
-KERNELOFFSET
-------------
-
-The kernel randomization offset. Used to compute the page offset. If
-KASLR is disabled, this value is zero.
-
-KERNEL_IMAGE_SIZE
------------------
-
-Currently unused by Makedumpfile. Used to compute the module virtual
-address by Crash.
-
-sme_mask
---------
-
-AMD-specific with SME support: it indicates the secure memory encryption
-mask. Makedumpfile tools need to know whether the crash kernel was
-encrypted. If SME is enabled in the first kernel, the crash kernel's
-page table entries (pgd/pud/pmd/pte) contain the memory encryption
-mask. This is used to remove the SME mask and obtain the true physical
-address.
-
-Currently, sme_mask stores the value of the C-bit position. If needed,
-additional SME-relevant info can be placed in that variable.
-
-For example::
-
- [ misc ][ enc bit ][ other misc SME info ]
- 0000_0000_0000_0000_1000_0000_0000_0000_0000_0000_..._0000
- 63 59 55 51 47 43 39 35 31 27 ... 3
-
-x86_32
-======
-
-X86_PAE
--------
-
-Denotes whether physical address extensions are enabled. It has the cost
-of a higher page table lookup overhead, and also consumes more page
-table space per process. Used to check whether PAE was enabled in the
-crash kernel when converting virtual addresses to physical addresses.
-
-ia64
-====
-
-pgdat_list|(pgdat_list, MAX_NUMNODES)
--------------------------------------
-
-pg_data_t array storing all NUMA nodes information. MAX_NUMNODES
-indicates the number of the nodes.
-
-node_memblk|(node_memblk, NR_NODE_MEMBLKS)
-------------------------------------------
-
-List of node memory chunks. Filled when parsing the SRAT table to obtain
-information about memory nodes. NR_NODE_MEMBLKS indicates the number of
-node memory chunks.
-
-These values are used to compute the number of nodes the crashed kernel used.
-
-node_memblk_s|(node_memblk_s, start_paddr)|(node_memblk_s, size)
-----------------------------------------------------------------
-
-The size of a struct node_memblk_s and the offsets of the
-node_memblk_s's members. Used to compute the number of nodes.
-
-PGTABLE_3|PGTABLE_4
--------------------
-
-User-space tools need to know whether the crash kernel was in 3-level or
-4-level paging mode. Used to distinguish the page table.
-
-ARM64
-=====
-
-VA_BITS
--------
-
-The maximum number of bits for virtual addresses. Used to compute the
-virtual memory ranges.
-
-kimage_voffset
---------------
-
-The offset between the kernel virtual and physical mappings. Used to
-translate virtual to physical addresses.
-
-PHYS_OFFSET
------------
-
-Indicates the physical address of the start of memory. Similar to
-kimage_voffset, which is used to translate virtual to physical
-addresses.
-
-KERNELOFFSET
-------------
-
-The kernel randomization offset. Used to compute the page offset. If
-KASLR is disabled, this value is zero.
-
-arm
-===
-
-ARM_LPAE
---------
-
-It indicates whether the crash kernel supports large physical address
-extensions. Used to translate virtual to physical addresses.
-
-s390
-====
-
-lowcore_ptr
------------
-
-An array with a pointer to the lowcore of every CPU. Used to print the
-psw and all registers information.
-
-high_memory
------------
-
-Used to get the vmalloc_start address from the high_memory symbol.
-
-(lowcore_ptr, NR_CPUS)
-----------------------
-
-The maximum number of CPUs.
-
-powerpc
-=======
-
-
-node_data|(node_data, MAX_NUMNODES)
------------------------------------
-
-See above.
-
-contig_page_data
-----------------
-
-See above.
-
-vmemmap_list
-------------
-
-The vmemmap_list maintains the entire vmemmap physical mapping. Used
-to get vmemmap list count and populated vmemmap regions info. If the
-vmemmap address translation information is stored in the crash kernel,
-it is used to translate vmemmap kernel virtual addresses.
-
-mmu_vmemmap_psize
------------------
-
-The size of a page. Used to translate virtual to physical addresses.
-
-mmu_psize_defs
---------------
-
-Page size definitions, i.e. 4k, 64k, or 16M.
-
-Used to make vtop translations.
-
-vmemmap_backing|(vmemmap_backing, list)|(vmemmap_backing, phys)|(vmemmap_backing, virt_addr)
---------------------------------------------------------------------------------------------
-
-The vmemmap virtual address space management does not have a traditional
-page table to track which virtual struct pages are backed by a physical
-mapping. The virtual to physical mappings are tracked in a simple linked
-list format.
-
-User-space tools need to know the offset of list, phys and virt_addr
-when computing the count of vmemmap regions.
-
-mmu_psize_def|(mmu_psize_def, shift)
-------------------------------------
-
-The size of a struct mmu_psize_def and the offset of mmu_psize_def's
-member.
-
-Used in vtop translations.
-
-sh
-==
-
-node_data|(node_data, MAX_NUMNODES)
------------------------------------
-
-See above.
-
-X2TLB
------
-
-Indicates whether the crashed kernel enabled SH extended mode.
the default calculated size. Use this option if default
boot memory size is not sufficient for second kernel to
boot successfully. For syntax of crashkernel= parameter,
- refer to Documentation/kdump/kdump.rst. If any offset is
+ refer to Documentation/admin-guide/kdump/kdump.rst. If any offset is
provided in crashkernel= parameter, it will be ignored
as fadump uses a predefined offset to reserve memory
for boot memory dump preservation in case of a crash.
（2）用串口终端启动（请参看Documentation/admin-guide/serial-console.rst），运行一个null
modem到另一台机器并用你喜欢的通讯工具获取输出。Minicom工作地很好。
-（3）使用Kdump（请参看Documentation/kdump/kdump.rst），
-使用在Documentation/kdump/gdbmacros.txt中定义的dmesg gdb宏，从旧的内存中提取内核
+（3）使用Kdump（请参看Documentation/admin-guide/kdump/kdump.rst），
+使用在Documentation/admin-guide/kdump/gdbmacros.txt中定义的dmesg gdb宏，从旧的内存中提取内核
环形缓冲区。
完整信息
L: kexec@lists.infradead.org
W: http://lse.sourceforge.net/kdump/
S: Maintained
-F: Documentation/kdump/
+F: Documentation/admin-guide/kdump/
KEENE FM RADIO TRANSMITTER DRIVER
M: Hans Verkuil <hverkuil@xs4all.nl>
kdump/kexec. The crash dump kernel must be compiled to a
memory address not used by the main kernel
- For more details see Documentation/kdump/kdump.rst
+ For more details see Documentation/admin-guide/kdump/kdump.rst
config AUTO_ZRELADDR
bool "Auto calculation of the decompressed kernel image address"
reserved region and then later executed after a crash by
kdump/kexec.
- For more details see Documentation/kdump/kdump.rst
+ For more details see Documentation/admin-guide/kdump/kdump.rst
config XEN_DOM0
def_bool y
to a memory address not used by the main kernel using
PHYSICAL_START.
- For more details see Documentation/kdump/kdump.rst
+ For more details see Documentation/admin-guide/kdump/kdump.rst
config KEXEC_JUMP
bool "kexec jump (EXPERIMENTAL)"
to a memory address not used by the main kernel or BIOS using
PHYSICAL_START, or it must be built as a relocatable image
(CONFIG_RELOCATABLE=y).
- For more details see Documentation/kdump/kdump.rst
+ For more details see Documentation/admin-guide/kdump/kdump.rst
config KEXEC_JUMP
bool "kexec jump"
the reserved region. In other words, it can be set based on
the "X" value as specified in the "crashkernel=YM@XM"
command line boot parameter passed to the panic-ed
- kernel. Please take a look at Documentation/kdump/kdump.rst
+ kernel. Please take a look at Documentation/admin-guide/kdump/kdump.rst
for more details about crash dumps.
Usage of bzImage for capturing the crash dump is recommended as
projects / openwrt / staging / blogic.git / commitdiff