Re: [PATCH v2] bpf: Fix BTF_ID symbol generation collision

[Alexei Starovoitov]

On Fri, Sep 15, 2023 at 10:18 AM Nathan Chancellor <nathan@xxxxxxxxxx> 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 same
> > 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__ happens to
> > be the same for the same symbol in two different translation units,
> > which is already quite unlikely to happen.
> >
> > Add __LINE__ number suffix to make BTF_ID symbol more unique, which is
> > not a complete fix, but it would help for now and meanwhile we can work
> > on better solution as suggested by Andrii.
> >
> > Cc: stable@xxxxxxxxxxxxxxx
> > Reported-by: Satya Durga Srinivasu Prabhala <quic_satyap@xxxxxxxxxxx>
> > Reported-by: Marcus Seyfarth <m.seyfarth@xxxxxxxxx>
> > Closes: https://github.com/ClangBuiltLinux/linux/issues/1913
> > Tested-by: Marcus Seyfarth <m.seyfarth@xxxxxxxxx>
> > Debugged-by: Nathan Chancellor <nathan@xxxxxxxxxx>
> > Co-developed-by: Jiri Olsa <jolsa@xxxxxxxxxx>
> > Link: https://lore.kernel.org/bpf/CAEf4Bzb5KQ2_LmhN769ifMeSJaWfebccUasQOfQKaOd0nQ51tw@xxxxxxxxxxxxxx/
> > Signed-off-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
> > ---
> >  tools/include/linux/btf_ids.h | 2 +-
>
> Shouldn't this diff be in include/linux/btf_ids.h as well? Otherwise, I
> don't think it will be used by the kernel build.

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.