From 5d6f52671e76ca2d55d74e676ac4c38ceb14a2d3 Mon Sep 17 00:00:00 2001 From: Arnd Bergmann Date: Mon, 4 Apr 2022 11:52:31 +0200 Subject: 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 --- arch/arm/mm/Kconfig | 28 ++++++++++++++++++---------- 1 file changed, 18 insertions(+), 10 deletions(-) (limited to 'arch/arm/mm/Kconfig') 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 -- cgit v1.2.3