powerpc/kconfig: make _etext and data areas alignment configurable on Book3s 32

Depending on the number of available BATs for mapping the different
kernel areas, it might be needed to increase the alignment of _etext
and/or of data areas.

This patchs allows the user to do it via Kconfig.

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 2544dae471e10ffef8b008362091d5a64be37212..81df0dbc8a9a35bb280e59841d62441588bca2c9 100644 (file)
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -721,16 +721,44 @@ config THREAD_SHIFT
          Used to define the stack size. The default is almost always what you
          want. Only change this if you know what you are doing.
 
+config ETEXT_SHIFT_BOOL
+       bool "Set custom etext alignment" if STRICT_KERNEL_RWX && PPC_BOOK3S_32
+       depends on ADVANCED_OPTIONS
+       help
+         This option allows you to set the kernel end of text alignment. When
+         RAM is mapped by blocks, the alignment needs to fit the size and
+         number of possible blocks. The default should be OK for most configs.
+
+         Say N here unless you know what you are doing.
+
 config ETEXT_SHIFT
-       int
+       int "_etext shift" if ETEXT_SHIFT_BOOL
+       range 17 28 if STRICT_KERNEL_RWX && PPC_BOOK3S_32
        default 17 if STRICT_KERNEL_RWX && PPC_BOOK3S_32
        default PPC_PAGE_SHIFT
+       help
+         On Book3S 32 (603+), IBATs are used to map kernel text.
+         Smaller is the alignment, greater is the number of necessary IBATs.
+
+config DATA_SHIFT_BOOL
+       bool "Set custom data alignment" if STRICT_KERNEL_RWX && PPC_BOOK3S_32
+       depends on ADVANCED_OPTIONS
+       help
+         This option allows you to set the kernel data alignment. When
+         RAM is mapped by blocks, the alignment needs to fit the size and
+         number of possible blocks. The default should be OK for most configs.
+
+         Say N here unless you know what you are doing.
 
 config DATA_SHIFT
-       int
+       int "Data shift" if DATA_SHIFT_BOOL
        default 24 if STRICT_KERNEL_RWX && PPC64
+       range 17 28 if STRICT_KERNEL_RWX && PPC_BOOK3S_32
        default 22 if STRICT_KERNEL_RWX && PPC_BOOK3S_32
        default PPC_PAGE_SHIFT
+       help
+         On Book3S 32 (603+), DBATs are used to map kernel text and rodata RO.
+         Smaller is the alignment, greater is the number of necessary DBATs.
 
 config FORCE_MAX_ZONEORDER
        int "Maximum zone order"