linux-kernel - Re: [PATCH] powerpc/vdso: Filter clang's auto var init zero enabler when linking

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Message-ID: <CAK7LNAThyrFRH22f8pdKyh0ypgCkEhnF9kUJ3XM3C=B2XGF-9A@mail.gmail.com>
Date:   Thu, 26 Jan 2023 13:23:53 +0900
From:   Masahiro Yamada <masahiroy@...nel.org>
To:     Nathan Chancellor <nathan@...nel.org>
Cc:     ndesaulniers@...gle.com, nicolas@...sle.eu, mpe@...erman.id.au,
        npiggin@...il.com, christophe.leroy@...roup.eu, trix@...hat.com,
        linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, llvm@...ts.linux.dev
Subject: Re: [PATCH] powerpc/vdso: Filter clang's auto var init zero enabler
 when linking

On Wed, Jan 25, 2023 at 1:20 AM Nathan Chancellor <nathan@...nel.org> wrote:
>
> After commit 7bbf02b875b5 ("kbuild: Stop using '-Qunused-arguments' with
> clang"), the PowerPC vDSO shows the following error with clang-13 and
> older when CONFIG_INIT_STACK_ALL_ZERO is enabled:
>
>   clang: error: argument unused during compilation: '-enable-trivial-auto-var-init-zero-knowing-it-will-be-removed-from-clang' [-Werror,-Wunused-command-line-argument]
>
> clang-14 added a change to make sure this flag never triggers
> -Wunused-command-line-argument, so it is fixed with newer releases. For
> older releases that the kernel still supports building with, just filter
> out this flag, as has been done for other flags.
>
> Fixes: b174f4c26aa3 ("powerpc/vdso: Improve linker flags")
> Fixes: 7bbf02b875b5 ("kbuild: Stop using '-Qunused-arguments' with clang")
> Link: https://github.com/llvm/llvm-project/commit/ca6d5813d17598cd180995fb3bdfca00f364475f
> Signed-off-by: Nathan Chancellor <nathan@...nel.org>
> ---
> This should be the last flag that needs to be filtered (famous last
> words...) but if any more come up, we should really just explore
> switching the PowerPC vDSO to linking with $(LD) like every other part
> of the kernel; for now, I hope this is fine.
>
> Cheers,
> Nathan


Applied to linux-kbuild. Thanks.

Since I rebased the branch, the tags have been updated
accordingly.





    powerpc/vdso: Filter clang's auto var init zero enabler when linking

    After commit 8d9acfce3332 ("kbuild: Stop using '-Qunused-arguments' with
    clang"), the PowerPC vDSO shows the following error with clang-13 and
    older when CONFIG_INIT_STACK_ALL_ZERO is enabled:

      clang: error: argument unused during compilation:
'-enable-trivial-auto-var-init-zero-knowing-it-will-be-removed-from-clang'
[-Werror,-Wunused-command-line-argument]

    clang-14 added a change to make sure this flag never triggers
    -Wunused-command-line-argument, so it is fixed with newer releases. For
    older releases that the kernel still supports building with, just filter
    out this flag, as has been done for other flags.

    Fixes: f0a42fbab447 ("powerpc/vdso: Improve linker flags")
    Fixes: 8d9acfce3332 ("kbuild: Stop using '-Qunused-arguments' with clang")
    Link: https://github.com/llvm/llvm-project/commit/ca6d5813d17598cd180995fb3bdfca00f364475f
    Signed-off-by: Nathan Chancellor <nathan@...nel.org>
    Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>



-- 
Best Regards
Masahiro Yamada