linux-kernel - Re: [PATCH] MIPS: vdso: Wrap -mexplicit-relocs in cc-option

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Message-ID: <5e4d8618.1c69fb81.7b7a.12f1@mx.google.com>
Date:   Wed, 19 Feb 2020 11:01:38 -0800
From:   Paul Burton <paulburton@...nel.org>
To:     Nathan Chancellor <natechancellor@...il.com>
CC:     linux-mips@...r.kernel.org
Subject: Re: [PATCH] MIPS: vdso: Wrap -mexplicit-relocs in cc-option

Hello,

Nathan Chancellor wrote:
> Clang does not support this option and errors out:
> 
> clang-11: error: unknown argument: '-mexplicit-relocs'
> 
> Clang does not appear to need this flag like GCC does because the jalr
> check that was added in commit 976c23af3ee5 ("mips: vdso: add build
> time check that no 'jalr t9' calls left") passes just fine with
> 
> $ make ARCH=mips CC=clang CROSS_COMPILE=mipsel-linux-gnu- malta_defconfig arch/mips/vdso/
> 
> even before commit d3f703c4359f ("mips: vdso: fix 'jalr t9' crash in
> vdso code").
> 
> -mrelax-pic-calls has been supported since clang 9, which is the
> earliest version that could build a working MIPS kernel, and it is the
> default for clang so just leave it be.

Applied to mips-fixes.

> commit 72cf3b3df423
> https://git.kernel.org/mips/c/72cf3b3df423
> 
> Fixes: d3f703c4359f ("mips: vdso: fix 'jalr t9' crash in vdso code")
> Link: https://github.com/ClangBuiltLinux/linux/issues/890
> Signed-off-by: Nathan Chancellor <natechancellor@...il.com>
> Reviewed-by: Nick Desaulniers <ndesaulniers@...gle.com>
> Tested-by: Nick Desaulniers <ndesaulniers@...gle.com>
> Signed-off-by: Paul Burton <paulburton@...nel.org>

Thanks,
    Paul

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