[PATCH v5 14/16] powerpc/kconfig: make _etext and data areas alignment configurable on Book3s 32

Christophe Leroy
2019-02-21T19:08:59Z

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>
---
arch/powerpc/Kconfig | 32 ++++++++++++++++++++++++++++++--
1 file changed, 30 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 640a7cfba9d0..20c4e3a62b90 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -725,16 +725,44 @@ 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"
--
2.13.3