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Date:   Thu, 28 Apr 2022 20:09:45 -0400
From:   Steven Rostedt <>
To:     Andrii Nakryiko <>
Cc:     Alexei Starovoitov <>,
        Masami Hiramatsu <>,
        Jiri Olsa <>,
        Alexei Starovoitov <>,
        Daniel Borkmann <>,
        Andrii Nakryiko <>,
        Networking <>, bpf <>,
        lkml <>,
        Martin KaFai Lau <>,
        Song Liu <>, Yonghong Song <>,
        John Fastabend <>,
        KP Singh <>
Subject: Re: [RFC bpf-next 4/4] selftests/bpf: Add attach bench test

On Thu, 28 Apr 2022 19:53:03 -0400
Steven Rostedt <> wrote:

> > But that __fentry__ call is not part of __bpf_tramp_exit, actually.
> > Whether to call it a bug or limitation is secondary. It marks
> > __bpf_tramp_exit as attachable through kprobe/ftrace while it really
> > isn't.  
> I'm confused by what you mean by "marks __bpf_tramp_exit as attachable"?
> What does? Where does it get that information? Does it read
> available_filter_functions?

OK, I think I see the issue you have. Because the functions shown in
available_filter_functions which uses the simple "%ps" to show the function

And the code that does the actual matching uses kallsyms_lookup()

Which appears not to match the function for the address, you can't pass in
__bpf_tramp_exit because it wont match the symbol returned by

This does indeed look like a bug in %ps.

But in the mean time, I could open code %ps and see if that fixes it. I'll
give it try.

-- Steve

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