linux-kernel - Re: [PATCH v9 0/3] Kbuild: DWARF v5 support

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Date:   Sat, 6 Feb 2021 13:28:34 +0100
From:   Sedat Dilek <sedat.dilek@...il.com>
To:     Masahiro Yamada <masahiroy@...nel.org>
Cc:     Nick Desaulniers <ndesaulniers@...gle.com>,
        Nathan Chancellor <natechancellor@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Clang-Built-Linux ML <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>,
        Chris Murphy <bugzilla@...orremedies.com>,
        Mark Wielaard <mark@...mp.org>
Subject: Re: [PATCH v9 0/3] Kbuild: DWARF v5 support

On Sat, Feb 6, 2021 at 1:05 PM Masahiro Yamada <masahiroy@...nel.org> wrote:
>
> On Sat, Feb 6, 2021 at 6:00 AM Sedat Dilek <sedat.dilek@...il.com> wrote:
> >
> > On Fri, Feb 5, 2021 at 9:22 PM Nick Desaulniers <ndesaulniers@...gle.com> wrote:
> > >
> > > DWARF v5 is the latest standard of the DWARF debug info format.
> > >
> > > DWARF5 wins significantly in terms of size and especially so when mixed
> > > with compression (CONFIG_DEBUG_INFO_COMPRESSED).
> > >
> > > Link: http://www.dwarfstd.org/doc/DWARF5.pdf
> > >
> > > Patch 1 places the DWARF v5 sections explicitly in the kernel linker
> > > script.
> > > Patch 2 modifies Kconfig for DEBUG_INFO_DWARF4 to be used as a fallback.
> > > Patch 3 adds an explicit Kconfig for DWARF v5 for clang and older GCC
> > > where the implicit default DWARF version is not 5.
> > >
> > > Changes from v8:
> > > * Separate out the linker script changes (from v7 0002). Put those
> > >   first. Carry Reviewed by and tested by tags.  Least contentious part
> > >   of the series. Tagged for stable; otherwise users upgrading to GCC 11
> > >   may find orphan section warnings from the implicit default DWARF
> > >   version changing and generating the new debug info sections.
> > > * Add CONFIG_DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT in 0002, make it the
> > >   default rather than CONFIG_DEBUG_INFO_DWARF4, as per Mark, Jakub,
> > >   Arvind.
> > > * Drop reviewed by and tested by tags for 0002 and 0003; sorry
> > >   reviewers/testers, but I view that as a big change. I will buy you
> > >   beers if you're fatigued, AND for the help so far. I appreciate you.
> >
> > All 3 patches NACKed - I drink no beer.
>
> LoL.
> Other than beer, I am fine with v9.
>
> Personally, I thought v8 (no CONFIG_DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT)
> was good too, but I do not have a strong opinion about
> leaving the compiler's freedom to choose the dwarf version.
>
> Unless somebody has an objection, I will pick up v9 for the next MW.
>
>
> Meanwhile, if you want to give reviewed-by / tested-by
> please do so.
>

Fine with me.

I have no opinion towards distro-handling of toolchain-default(s).

Feel free to add my:
Tested-by: Sedat Dilek <sedat.dilek@...il.com> # LLVM/Clang v12.0.0-rc1 x86-64

Thanks to all involved people - I enjoyed the evolution of this patchset.

- Sedat -

P.S.: /me drinking right now an Earl Grey tea - drink whatever you prefer :-).