netdev - Re: [PATCH bpf-next v1 4/6] bpf: selftests: Move test_ksyms

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Message-ID: <CAPhsuW4X3L7ZZH_RfeP5xYvoMh3STthqZEFDpcqTTjbkfsh3sw@mail.gmail.com>
Date:   Thu, 7 Oct 2021 13:57:33 -0700
From:   Song Liu <song@...nel.org>
To:     Kumar Kartikeya Dwivedi <memxor@...il.com>
Cc:     bpf <bpf@...r.kernel.org>, Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Toke Høiland-Jørgensen <toke@...hat.com>,
        Networking <netdev@...r.kernel.org>
Subject: Re: [PATCH bpf-next v1 4/6] bpf: selftests: Move test_ksyms_weak test
 to lskel, add libbpf test

On Thu, Oct 7, 2021 at 1:46 PM Kumar Kartikeya Dwivedi <memxor@...il.com> wrote:
>
[...]
> > >
> > >  /* typeless symbols, default to zero. */
> > > @@ -38,7 +37,7 @@ int pass_handler(const void *ctx)
> > >         /* tests existing symbols. */
> > >         rq = (struct rq *)bpf_per_cpu_ptr(&runqueues, 0);
> > >         if (rq)
> > > -               out__existing_typed = rq->cpu;
> > > +               out__existing_typed = 0;
> >
> > Why do we need this change?
> >
>
> Since they share the same BPF object for generating skeleton, it needs to remove
> dependency on CO-RE which gen_loader does not support.
>
> If it is kept, we get this:
> ...
> libbpf: // TODO core_relo: prog 0 insn[5] rq kind 0
> libbpf: prog 'pass_handler': relo #0: failed to relocate: -95
> libbpf: failed to perform CO-RE relocations: -95
> libbpf: failed to load object 'test_ksyms_weak'

I see. Thanks for the explanation.

Song