linux-kernel - Re: [RFC bpf-next 4/4] selftests/bpf: Add attach bench test

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Message-ID: <CAEf4BzaA+vr6V24dG7JCHHmedp2TcJv4ZnuKB=zXzuOpi-QYFg@mail.gmail.com>
Date:   Wed, 13 Apr 2022 09:45:52 -0700
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Masami Hiramatsu <mhiramat@...nel.org>,
        Jiri Olsa <jolsa@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        lkml <linux-kernel@...r.kernel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...omium.org>
Subject: Re: [RFC bpf-next 4/4] selftests/bpf: Add attach bench test

On Wed, Apr 13, 2022 at 9:44 AM Steven Rostedt <rostedt@...dmis.org> wrote:
>
> On Tue, 12 Apr 2022 09:49:23 +0900
> Masami Hiramatsu <mhiramat@...nel.org> wrote:
>
> > > I'm really curious how did you manage to attach to everything in
> > > available_filter_functions because when I'm trying to do that I fail.
> > > available_filter_functions has a bunch of functions that should not be
> > > attachable (e.g., notrace functions). Look just at __bpf_tramp_exit:
> > >
> > >   void notrace __bpf_tramp_exit(struct bpf_tramp_image *tr);
>
> Did you only use the "notrace" on the prototype? I see the semicolon at
> the end of your comment. It only affects the actual function itself,
> not the prototype.

notrace is both on declaration and on definition, see kernel/bpf/trampoline.c:

void notrace __bpf_tramp_exit(struct bpf_tramp_image *tr)
{
        percpu_ref_put(&tr->pcref);
}


>
> -- Steve