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From:   Alexei Starovoitov <alexei.starovoitov@gmail.com>
Date:   Fri, 15 Sep 2023 10:28:32 -0700
Message-ID: <CAADnVQKJbTM-1n8YKvpC9XN7=tZuJi9mhnmmZSTVFOeBDv+SGA@mail.gmail.com>
Subject: Re: [PATCH v2] bpf: Fix BTF_ID symbol generation collision
To:     Nick Desaulniers <ndesaulniers@google.com>
Cc:     Nathan Chancellor <nathan@kernel.org>,
        Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Andrii Nakryiko <andrii@kernel.org>,
        LKML <linux-kernel@vger.kernel.org>, bpf <bpf@vger.kernel.org>,
        Martin KaFai Lau <kafai@fb.com>,
        Song Liu <songliubraving@fb.com>, Yonghong Song <yhs@fb.com>,
        John Fastabend <john.fastabend@gmail.com>,
        KP Singh <kpsingh@chromium.org>,
        Stanislav Fomichev <sdf@google.com>,
        Hao Luo <haoluo@google.com>, stable <stable@vger.kernel.org>,
        Satya Durga Srinivasu Prabhala <quic_satyap@quicinc.com>,
        Marcus Seyfarth <m.seyfarth@gmail.com>,
        Jiri Olsa <jolsa@kernel.org>
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On Fri, Sep 15, 2023 at 10:27=E2=80=AFAM Alexei Starovoitov
<alexei.starovoitov@gmail.com> wrote:
>
> On Fri, Sep 15, 2023 at 10:24=E2=80=AFAM Nick Desaulniers
> <ndesaulniers@google.com> wrote:
> >
> > On Fri, Sep 15, 2023 at 10:22=E2=80=AFAM Alexei Starovoitov
> > <alexei.starovoitov@gmail.com> wrote:
> > >
> > > On Fri, Sep 15, 2023 at 10:18=E2=80=AFAM Nathan Chancellor <nathan@ke=
rnel.org> wrote:
> > > >
> > > > On Fri, Sep 15, 2023 at 09:42:20AM -0700, Nick Desaulniers wrote:
> > > > > Marcus and Satya reported an issue where BTF_ID macro generates s=
ame
> > > > > symbol in separate objects and that breaks final vmlinux link.
> > > > >
> > > > >   ld.lld: error: ld-temp.o <inline asm>:14577:1: symbol
> > > > >   '__BTF_ID__struct__cgroup__624' is already defined
> > > > >
> > > > > This can be triggered under specific configs when __COUNTER__ hap=
pens to
> > > > > be the same for the same symbol in two different translation unit=
s,
> > > > > which is already quite unlikely to happen.
> > > > >
> > > > > Add __LINE__ number suffix to make BTF_ID symbol more unique, whi=
ch is
> > > > > not a complete fix, but it would help for now and meanwhile we ca=
n work
> > > > > on better solution as suggested by Andrii.
> > > > >
> > > > > Cc: stable@vger.kernel.org
> > > > > Reported-by: Satya Durga Srinivasu Prabhala <quic_satyap@quicinc.=
com>
> > > > > Reported-by: Marcus Seyfarth <m.seyfarth@gmail.com>
> > > > > Closes: https://github.com/ClangBuiltLinux/linux/issues/1913
> > > > > Tested-by: Marcus Seyfarth <m.seyfarth@gmail.com>
> > > > > Debugged-by: Nathan Chancellor <nathan@kernel.org>
> > > > > Co-developed-by: Jiri Olsa <jolsa@kernel.org>
> > > > > Link: https://lore.kernel.org/bpf/CAEf4Bzb5KQ2_LmhN769ifMeSJaWfeb=
ccUasQOfQKaOd0nQ51tw@mail.gmail.com/
> > > > > Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
> > > > > ---
> > > > >  tools/include/linux/btf_ids.h | 2 +-
> > > >
> > > > Shouldn't this diff be in include/linux/btf_ids.h as well? Otherwis=
e, I
> > > > don't think it will be used by the kernel build.
> >
> > D'oh!
> >
> > >
> > > argh.
> > > Let's do this patch as-is and another patch to update everything
> > > in tools/../btf_ids.h, since it got out of sync quite a bit.
> >
> > I think I can do both in a v3? I don't see the issue (in mainline, are
> > they out of sync in -next?)
>
> Yes. Pls send v3 with two patches.
> We'll apply and flush bpf trees, so both will have all fixes in a day or =
so.

And please use [PATCH bpf v3] in subject, so that BPF CI can test it proper=
ly.