linux-kernel - Re: [PATCH 7/8] s390/boot: do not emit debug info for assembly with llvm's IAS

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Message-ID: <CAKwvOdn3Mdn9ek-7EotHmd6Wb7C5rzZnOxAQVtbQEd2LBBZGRg@mail.gmail.com>
Date:   Wed, 11 May 2022 12:40:07 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Heiko Carstens <hca@...ux.ibm.com>
Cc:     Vasily Gorbik <gor@...ux.ibm.com>,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        Jonas Paulsson <paulsson@...ux.vnet.ibm.com>,
        Ulrich Weigand <ulrich.weigand@...ibm.com>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Alexander Egorenkov <egorenar@...ux.ibm.com>,
        Sven Schnelle <svens@...ux.ibm.com>,
        Andreas Krebbel <krebbel@...ux.ibm.com>,
        Nathan Chancellor <natechancellor@...il.com>,
        linux-kernel@...r.kernel.org, linux-s390@...r.kernel.org
Subject: Re: [PATCH 7/8] s390/boot: do not emit debug info for assembly with
 llvm's IAS

On Wed, May 11, 2022 at 5:05 AM Heiko Carstens <hca@...ux.ibm.com> wrote:
>
> Commit ee6d777d3e93 ("s390/decompressor: support extra debug flags")
> added extra debug flags, in particular debug info is created,
> depending on config options.
>
> With llvm's IAS this causes this compile warning:
>
> arch/s390/boot/head.S:38:1: warning: DWARF2 only supports one section per compilation unit
> .section ".head.text","ax"
> ^
>
> This is a known problem and was addressed with a commit b8a9092330da
> ("Kbuild: do not emit debug info for assembly with LLVM_IAS=1").
> Just do the same for s390 to get rid of this warning.
>
> Signed-off-by: Heiko Carstens <hca@...ux.ibm.com>
> ---
>  arch/s390/Makefile | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/arch/s390/Makefile b/arch/s390/Makefile
> index c59efc83f020..d73611b35164 100644
> --- a/arch/s390/Makefile
> +++ b/arch/s390/Makefile
> @@ -20,7 +20,9 @@ LDFLAGS_vmlinux       := -pie
>  endif
>  aflags_dwarf   := -Wa,-gdwarf-2

^ or can we use a more modern variant of dwarf, like at least dwarf-4?

>  KBUILD_AFLAGS_DECOMPRESSOR := $(CLANG_FLAGS) -m64 -D__ASSEMBLY__
> +ifndef CONFIG_AS_IS_LLVM
>  KBUILD_AFLAGS_DECOMPRESSOR += $(if $(CONFIG_DEBUG_INFO),$(aflags_dwarf))
> +endif
>  KBUILD_CFLAGS_DECOMPRESSOR := $(CLANG_FLAGS) -m64 -O2 -mpacked-stack
>  KBUILD_CFLAGS_DECOMPRESSOR += -DDISABLE_BRANCH_PROFILING -D__NO_FORTIFY
>  KBUILD_CFLAGS_DECOMPRESSOR += -fno-delete-null-pointer-checks -msoft-float -mbackchain
> --
> 2.32.0
>


-- 
Thanks,
~Nick Desaulniers