linux-kernel - Re: [PATCH v3] Kbuild: do not emit debug info for assembly with LLVM

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Date:   Mon, 16 Nov 2020 15:41:42 -0800
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Masahiro Yamada <masahiroy@...nel.org>
Cc:     Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-toolchains@...r.kernel.org,
        clang-built-linux <clang-built-linux@...glegroups.com>,
        Fangrui Song <maskray@...gle.com>,
        Nathan Chancellor <natechancellor@...il.com>,
        Sedat Dilek <sedat.dilek@...il.com>,
        Dmitry Golovin <dima@...ovin.in>,
        Alistair Delva <adelva@...gle.com>,
        "# 3.4.x" <stable@...r.kernel.org>
Subject: Re: [PATCH v3] Kbuild: do not emit debug info for assembly with LLVM_IAS=1

Hi Masahiro, have you had time to review v3 of this patch?

On Mon, Nov 9, 2020 at 10:35 AM Nick Desaulniers
<ndesaulniers@...gle.com> wrote:
>
> Clang's integrated assembler produces the warning for assembly files:
>
> warning: DWARF2 only supports one section per compilation unit
>
> If -Wa,-gdwarf-* is unspecified, then debug info is not emitted for
> assembly sources (it is still emitted for C sources).  This will be
> re-enabled for newer DWARF versions in a follow up patch.
>
> Enables defconfig+CONFIG_DEBUG_INFO to build cleanly with
> LLVM=1 LLVM_IAS=1 for x86_64 and arm64.
>
> Cc: <stable@...r.kernel.org>
> Link: https://github.com/ClangBuiltLinux/linux/issues/716
> Reported-by: Dmitry Golovin <dima@...ovin.in>
> Reported-by: Nathan Chancellor <natechancellor@...il.com>
> Suggested-by: Dmitry Golovin <dima@...ovin.in>
> Suggested-by: Nathan Chancellor <natechancellor@...il.com>
> Suggested-by: Sedat Dilek <sedat.dilek@...il.com>
> Reviewed-by: Fangrui Song <maskray@...gle.com>
> Reviewed-by: Nathan Chancellor <natechancellor@...il.com>
> Signed-off-by: Nick Desaulniers <ndesaulniers@...gle.com>
> ---
>  Makefile | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/Makefile b/Makefile
> index f353886dbf44..7e899d356902 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -826,7 +826,9 @@ else
>  DEBUG_CFLAGS   += -g
>  endif
>
> +ifneq ($(LLVM_IAS),1)
>  KBUILD_AFLAGS  += -Wa,-gdwarf-2
> +endif
>
>  ifdef CONFIG_DEBUG_INFO_DWARF4
>  DEBUG_CFLAGS   += -gdwarf-4
> --
> 2.29.2.222.g5d2a92d10f8-goog
>


-- 
Thanks,
~Nick Desaulniers