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: <Yn1ENkc1EhHob6+x@osiris>
Date:   Thu, 12 May 2022 19:30:30 +0200
From:   Heiko Carstens <hca@...ux.ibm.com>
To:     Nick Desaulniers <ndesaulniers@...gle.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 12:40:07PM -0700, Nick Desaulniers wrote:
> 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?

For now I would like that this works the same like what you introduced
with commit b8a9092330da ("Kbuild: do not emit debug info for assembly
with LLVM_IAS=1").

I wouldn't like to have dwarf-4 enabled only for this single file, and
disabled for all other asm files (assuming that dwarf-4 works).