diff options
| author | Arnd Bergmann | 2022-04-04 11:52:31 +0200 |
|---|---|---|
| committer | Arnd Bergmann | 2022-04-08 17:20:54 +0200 |
| commit | 5d6f52671e76ca2d55d74e676ac4c38ceb14a2d3 (patch) | |
| tree | 7eb2ac50db50a924718ae5bd99641f3e4879150d /arch/arm/mm/Kconfig | |
| parent | a3102fafdce6f150e5a46e1725bb1732f8953a01 (diff) | |
ARM: rework endianess selection
Choosing big-endian vs little-endian kernels in Kconfig has not worked
correctly since the introduction of CONFIG_ARCH_MULTIPLATFORM a long
time ago.
The problems is that CONFIG_BIG_ENDIAN depends on
ARCH_SUPPORTS_BIG_ENDIAN, which can set by any one platform
in the config, but would actually have to be supported by all
of them.
This was mostly ok for ARMv6/ARMv7 builds, since these are BE8 and
tend to just work aside from problems in nonportable device drivers.
For ARMv4/v5 machines, CONFIG_BIG_ENDIAN and CONFIG_ARCH_MULTIPLATFORM
were never set together, so this was disabled on all those machines
except for IXP4xx.
As IXP4xx can now become part of ARCH_MULTIPLATFORM, it seems better to
formalize this logic: all ARMv4/v5 platforms get an explicit dependency
on being either big-endian (ixp4xx) or little-endian (the rest). We may
want to fix ixp4xx in the future to support both, but it does not work
in LE mode at the moment.
For the ARMv6/v7 platforms, there are two ways this could be handled
a) allow both modes only for platforms selecting
'ARCH_SUPPORTS_BIG_ENDIAN' today, but only LE mode for the
others, given that these were added intentionally at some
point.
b) allow both modes everwhere, given that it was already possible
to build that way by e.g. selecting ARCH_VIRT, and that the
list is not an accurate reflection of which platforms may or
may not work.
Out of these, I picked b) because it seemed slighly more logical
to me.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Diffstat (limited to 'arch/arm/mm/Kconfig')
| -rw-r--r-- | arch/arm/mm/Kconfig | 28 |
1 files changed, 18 insertions, 10 deletions
diff --git a/arch/arm/mm/Kconfig b/arch/arm/mm/Kconfig index d30ee26ccc87..a3a4589ec73b 100644 --- a/arch/arm/mm/Kconfig +++ b/arch/arm/mm/Kconfig @@ -738,15 +738,29 @@ config SWP_EMULATE If unsure, say Y. +choice + prompt "CPU Endianess" + default CPU_LITTLE_ENDIAN + +config CPU_LITTLE_ENDIAN + bool "Built little-endian kernel" + help + Say Y if you plan on running a kernel in little-endian mode. + This is the default and is used in practically all modern user + space builds. + config CPU_BIG_ENDIAN bool "Build big-endian kernel" - depends on ARCH_SUPPORTS_BIG_ENDIAN depends on !LD_IS_LLD help Say Y if you plan on running a kernel in big-endian mode. - Note that your board must be properly built and your board - port must properly enable any big-endian related features - of your chipset/board/processor. + This works on many machines using ARMv6 or newer processors + but requires big-endian user space. + + The only ARMv5 platform with big-endian support is + Intel IXP4xx. + +endchoice config CPU_ENDIAN_BE8 bool @@ -1122,12 +1136,6 @@ config ARM_DMA_MEM_BUFFERABLE config ARM_HEAVY_MB bool -config ARCH_SUPPORTS_BIG_ENDIAN - bool - help - This option specifies the architecture can support big endian - operation. - config DEBUG_ALIGN_RODATA bool "Make rodata strictly non-executable" depends on STRICT_KERNEL_RWX |