linux-kernel - Re: [PATCH v7 1/2] Kbuild: make DWARF version a choice

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Date:   Wed, 3 Feb 2021 22:13:22 -0800
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Nathan Chancellor <nathan@...nel.org>
Cc:     Masahiro Yamada <masahiroy@...nel.org>,
        Nathan Chancellor <natechancellor@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Sedat Dilek <sedat.dilek@...il.com>,
        LKML <linux-kernel@...r.kernel.org>,
        clang-built-linux <clang-built-linux@...glegroups.com>,
        Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        linux-arch <linux-arch@...r.kernel.org>,
        Jakub Jelinek <jakub@...hat.com>,
        Fangrui Song <maskray@...gle.com>,
        Caroline Tice <cmtice@...gle.com>,
        Nick Clifton <nickc@...hat.com>, Yonghong Song <yhs@...com>,
        Jiri Olsa <jolsa@...nel.org>,
        Andrii Nakryiko <andrii@...nel.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Arvind Sankar <nivedita@...m.mit.edu>
Subject: Re: [PATCH v7 1/2] Kbuild: make DWARF version a choice

On Fri, Jan 29, 2021 at 5:52 PM Nathan Chancellor <nathan@...nel.org> wrote:
>
> On Fri, Jan 29, 2021 at 04:44:00PM -0800, Nick Desaulniers wrote:
> > Modifies CONFIG_DEBUG_INFO_DWARF4 to be a member of a choice which is
> > the default. Does so in a way that's forward compatible with existing
> > configs, and makes adding future versions more straightforward.
> >
> > GCC since ~4.8 has defaulted to this DWARF version implicitly.
> >
> > Suggested-by: Arvind Sankar <nivedita@...m.mit.edu>
> > Suggested-by: Fangrui Song <maskray@...gle.com>
> > Suggested-by: Nathan Chancellor <nathan@...nel.org>
> > Suggested-by: Masahiro Yamada <masahiroy@...nel.org>
> > Signed-off-by: Nick Desaulniers <ndesaulniers@...gle.com>
>
> One comment below:
>
> Reviewed-by: Nathan Chancellor <nathan@...nel.org>
>
> > ---
> >  Makefile          |  5 ++---
> >  lib/Kconfig.debug | 16 +++++++++++-----
> >  2 files changed, 13 insertions(+), 8 deletions(-)
> >
> > diff --git a/Makefile b/Makefile
> > index 95ab9856f357..d2b4980807e0 100644
> > --- a/Makefile
> > +++ b/Makefile
> > @@ -830,9 +830,8 @@ ifneq ($(LLVM_IAS),1)
> >  KBUILD_AFLAGS        += -Wa,-gdwarf-2
>
> It is probably worth a comment somewhere that assembly files will still
> have DWARF v2.

Such a comment should have gone on
commit b8a9092330da ("Kbuild: do not emit debug info for assembly with
LLVM_IAS=1")

It's also more complicated than "assembly files will still have DWARF
v4," due to the LLVM_IAS check.

Further, such a comment would be inappropriate for patch 1 of the
series, which simply changes a Kconfig option into a choice.  I will
add a note to the commit message of patch 2, and carry your reviewed
by tag.  Please nack v8 (which I plan to send imminently) if you
disagree.
-- 
Thanks,
~Nick Desaulniers