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[bpf] bpf: Fix BTF_ID symbol generation

Message ID 20230915103228.1196234-1-jolsa@kernel.org (mailing list archive)
State Changes Requested
Delegated to: BPF
Headers show
Series [bpf] bpf: Fix BTF_ID symbol generation | expand

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Commit Message

Jiri Olsa Sept. 15, 2023, 10:32 a.m. UTC 
Marcus and Nick reported issue where BTF_ID macro generates same
symbol in separate objects and that breaks final vmlinux link.

Adding __LINE__ number suffix to make BTF_ID symbol more unique,
which is not real fix, but it would help for now and meanwhile
we can work on better solution as suggested by Andrii in [2].

[1] https://github.com/ClangBuiltLinux/linux/issues/1913
[2] https://lore.kernel.org/bpf/ZQQVr35crUtN1quS@krava/T/#m64d7c29c407d6adf0e7b420359958b3aafa7bf69
Reported-by: Marcus Seyfarth <m.seyfarth@gmail.com>
Reported-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
 include/linux/btf_ids.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Comments

Nick Desaulniers Sept. 15, 2023, 4:25 p.m. UTC | #1 
On Fri, Sep 15, 2023 at 3:32 AM Jiri Olsa <jolsa@kernel.org> wrote:
>
> Marcus and Nick reported issue where BTF_ID macro generates same
> symbol in separate objects and that breaks final vmlinux link.
>
> Adding __LINE__ number suffix to make BTF_ID symbol more unique,
> which is not real fix, but it would help for now and meanwhile
> we can work on better solution as suggested by Andrii in [2].
>
> [1] https://github.com/ClangBuiltLinux/linux/issues/1913
> [2] https://lore.kernel.org/bpf/ZQQVr35crUtN1quS@krava/T/#m64d7c29c407d6adf0e7b420359958b3aafa7bf69
> Reported-by: Marcus Seyfarth <m.seyfarth@gmail.com>
> Reported-by: Nick Desaulniers <ndesaulniers@google.com>
> Signed-off-by: Jiri Olsa <jolsa@kernel.org>
> ---
>  include/linux/btf_ids.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/include/linux/btf_ids.h b/include/linux/btf_ids.h
> index a3462a9b8e18..a9cb10b0e2e9 100644
> --- a/include/linux/btf_ids.h
> +++ b/include/linux/btf_ids.h
> @@ -49,7 +49,7 @@ word                                                  \
>         ____BTF_ID(symbol, word)
>
>  #define __ID(prefix) \
> -       __PASTE(prefix, __COUNTER__)
> +       __PASTE(__PASTE(prefix, __COUNTER__), __LINE__)

I think __COUNTER__ and __LINE__ both expand to string literals; you
can avoid another expansion via __PASTE by just putting them adjacent,
like so:
https://github.com/ClangBuiltLinux/linux/issues/1913#issuecomment-1710794319
I'll send that as a v2 and link back to your v1.

>
>  /*
>   * The BTF_ID defines unique symbol for each ID pointing
> --
> 2.41.0
>
Nick Desaulniers Sept. 15, 2023, 5:27 p.m. UTC | #2 
On Fri, Sep 15, 2023 at 9:25 AM Nick Desaulniers
<ndesaulniers@google.com> wrote:
>
> On Fri, Sep 15, 2023 at 3:32 AM Jiri Olsa <jolsa@kernel.org> wrote:
> >
> > Marcus and Nick reported issue where BTF_ID macro generates same
> > symbol in separate objects and that breaks final vmlinux link.
> >
> > Adding __LINE__ number suffix to make BTF_ID symbol more unique,
> > which is not real fix, but it would help for now and meanwhile
> > we can work on better solution as suggested by Andrii in [2].
> >
> > [1] https://github.com/ClangBuiltLinux/linux/issues/1913
> > [2] https://lore.kernel.org/bpf/ZQQVr35crUtN1quS@krava/T/#m64d7c29c407d6adf0e7b420359958b3aafa7bf69
> > Reported-by: Marcus Seyfarth <m.seyfarth@gmail.com>
> > Reported-by: Nick Desaulniers <ndesaulniers@google.com>
> > Signed-off-by: Jiri Olsa <jolsa@kernel.org>
> > ---
> >  include/linux/btf_ids.h | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/include/linux/btf_ids.h b/include/linux/btf_ids.h
> > index a3462a9b8e18..a9cb10b0e2e9 100644
> > --- a/include/linux/btf_ids.h
> > +++ b/include/linux/btf_ids.h
> > @@ -49,7 +49,7 @@ word                                                  \
> >         ____BTF_ID(symbol, word)
> >
> >  #define __ID(prefix) \
> > -       __PASTE(prefix, __COUNTER__)
> > +       __PASTE(__PASTE(prefix, __COUNTER__), __LINE__)
>
> I think __COUNTER__ and __LINE__ both expand to string literals; you

ah, no I was wrong.

But this change needs to go into tools/include/linux/btf_ids.h, too.

I'll wrap that up in my v3.

> can avoid another expansion via __PASTE by just putting them adjacent,
> like so:
> https://github.com/ClangBuiltLinux/linux/issues/1913#issuecomment-1710794319
> I'll send that as a v2 and link back to your v1.
>
> >
> >  /*
> >   * The BTF_ID defines unique symbol for each ID pointing
> > --
> > 2.41.0
> >
>
>
> --
> Thanks,
> ~Nick Desaulniers
diff mbox series

Patch

diff --git a/include/linux/btf_ids.h b/include/linux/btf_ids.h
index a3462a9b8e18..a9cb10b0e2e9 100644
--- a/include/linux/btf_ids.h
+++ b/include/linux/btf_ids.h
@@ -49,7 +49,7 @@  word							\
 	____BTF_ID(symbol, word)
 
 #define __ID(prefix) \
-	__PASTE(prefix, __COUNTER__)
+	__PASTE(__PASTE(prefix, __COUNTER__), __LINE__)
 
 /*
  * The BTF_ID defines unique symbol for each ID pointing