Re: [PATCH AUTOSEL 4.14 08/23] ARM: 8875/1: Kconfig: default to AEABI w/ Clang

From: Nathan Chancellor
Date: Sun Sep 29 2019 - 14:09:00 EST


On Sun, Sep 29, 2019 at 01:35:18PM -0400, Sasha Levin wrote:
> From: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
>
> [ Upstream commit a05b9608456e0d4464c6f7ca8572324ace57a3f4 ]
>
> Clang produces references to __aeabi_uidivmod and __aeabi_idivmod for
> arm-linux-gnueabi and arm-linux-gnueabihf targets incorrectly when AEABI
> is not selected (such as when OABI_COMPAT is selected).
>
> While this means that OABI userspaces wont be able to upgraded to
> kernels built with Clang, it means that boards that don't enable AEABI
> like s3c2410_defconfig will stop failing to link in KernelCI when built
> with Clang.
>
> Link: https://github.com/ClangBuiltLinux/linux/issues/482
> Link: https://groups.google.com/forum/#!msg/clang-built-linux/yydsAAux5hk/GxjqJSW-AQAJ
>
> Suggested-by: Arnd Bergmann <arnd@xxxxxxxx>
> Signed-off-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
> Reviewed-by: Arnd Bergmann <arnd@xxxxxxxx>
> Reviewed-by: Linus Walleij <linus.walleij@xxxxxxxxxx>
> Signed-off-by: Russell King <rmk+kernel@xxxxxxxxxxxxxxx>
> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
> ---
> arch/arm/Kconfig | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> index cf69aab648fbd..f0080864b9ce8 100644
> --- a/arch/arm/Kconfig
> +++ b/arch/arm/Kconfig
> @@ -1595,8 +1595,9 @@ config ARM_PATCH_IDIV
> code to do integer division.
>
> config AEABI
> - bool "Use the ARM EABI to compile the kernel" if !CPU_V7 && !CPU_V7M && !CPU_V6 && !CPU_V6K
> - default CPU_V7 || CPU_V7M || CPU_V6 || CPU_V6K
> + bool "Use the ARM EABI to compile the kernel" if !CPU_V7 && \
> + !CPU_V7M && !CPU_V6 && !CPU_V6K && !CC_IS_CLANG
> + default CPU_V7 || CPU_V7M || CPU_V6 || CPU_V6K || CC_IS_CLANG
> help
> This option allows for the kernel to be compiled using the latest
> ARM ABI (aka EABI). This is only useful if you are using a user
> --
> 2.20.1
>

Hi Sasha,

This patch will not do anything for 4.14 because CC_IS_CLANG is not
defined in this tree. The Kconfig patches that make this symbol possible
were not merged until 4.18. I would recommend dropping it (unless Nick
has an idea to make this work).

Cheers,
Nathan