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

From: Sasha Levin
Date: Sat Oct 05 2019 - 19:02:43 EST


On Sun, Sep 29, 2019 at 11:08:52AM -0700, Nathan Chancellor wrote:
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).

I've dropped it from 4.14 and older, thanks!

--
Thanks,
Sasha