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From:   Nick Desaulniers <ndesaulniers@google.com>
Date:   Wed, 3 Feb 2021 17:31:05 -0800
Message-ID: <CAKwvOdmniAMZD0LiFdr5N8eOwHqNFED2Pd=pwOFF2Y8eSRXUHA@mail.gmail.com>
Subject: Re: [PATCH v5 0/3] Kbuild: DWARF v5 support
To:     Arnaldo Carvalho de Melo <acme@kernel.org>,
        Yonghong Song <yhs@fb.com>,
        Andrii Nakryiko <andrii@kernel.org>,
        Jiri Olsa <jolsa@kernel.org>
Cc:     Sedat Dilek <sedat.dilek@gmail.com>,
        Masahiro Yamada <masahiroy@kernel.org>,
        Nathan Chancellor <natechancellor@gmail.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Clang-Built-Linux ML <clang-built-linux@googlegroups.com>,
        Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>,
        linux-arch <linux-arch@vger.kernel.org>,
        Jakub Jelinek <jakub@redhat.com>,
        Fangrui Song <maskray@google.com>,
        Caroline Tice <cmtice@google.com>,
        Nick Clifton <nickc@redhat.com>, dwarves@vger.kernel.org,
        bpf <bpf@vger.kernel.org>
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Precedence: bulk

On Sun, Jan 17, 2021 at 12:14 PM Arnaldo Carvalho de Melo
<acme@kernel.org> wrote:
>
> Em Fri, Jan 15, 2021 at 03:43:06PM -0800, Yonghong Song escreveu:
> >
> >
> > On 1/15/21 3:34 PM, Nick Desaulniers wrote:
> > > On Fri, Jan 15, 2021 at 3:24 PM Yonghong Song <yhs@fb.com> wrote:
> > > >
> > > >
> > > >
> > > > On 1/15/21 1:53 PM, Sedat Dilek wrote:
> > > > > En plus, I encountered breakage with GCC v10.2.1 and LLVM=1 and
> > > > > CONFIG_DEBUG_INFO_DWARF4.
> > > > > So might be good to add a "depends on !DEBUG_INFO_BTF" in this combination.
> > >
> > > Can you privately send me your configs that repro? Maybe I can isolate
> > > it to a set of configs?
> > >
> > > >
> > > > I suggested not to add !DEBUG_INFO_BTF to CONFIG_DEBUG_INFO_DWARF4.
> > > > It is not there before and adding this may suddenly break some users.
> > > >
> > > > If certain combination of gcc/llvm does not work for
> > > > CONFIG_DEBUG_INFO_DWARF4 with pahole, this is a bug bpf community
> > > > should fix.
> > >
> > > Is there a place I should report bugs?
> >
> > You can send bug report to Arnaldo Carvalho de Melo <acme@kernel.org>,
> > dwarves@vger.kernel.org and bpf@vger.kernel.org.
>
> I'm coming back from vacation, will try to read the messages and see if
> I can fix this.

IDK about DWARF v4; that seems to work for me.  I was previously observing
https://bugzilla.redhat.com/show_bug.cgi?id=1922698
with DWARF v5.  I just re-pulled the latest pahole, rebuilt, and no
longer see that warning.

I now observe a different set.  I plan on attending "BPF office hours
tomorrow morning," but if anyone wants a sneak peak of the errors and
how to reproduce:
https://gist.github.com/nickdesaulniers/ae8c9efbe4da69b1cf0dce138c1d2781


(FWIW: some other folks are hitting issues now with kernel's lack of
DWARF v5 support: https://bugzilla.redhat.com/show_bug.cgi?id=1922707)
-- 
Thanks,
~Nick Desaulniers