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    SubjectRe: [RFC bpf-next 4/4] selftests/bpf: Add attach bench test
    On Thu, 28 Apr 2022 20:09:45 -0400
    Steven Rostedt <rostedt@goodmis.org> wrote:

    > 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
    > name:
    >
    > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/kernel/trace/ftrace.c#n3692
    >
    > And the code that does the actual matching uses kallsyms_lookup()
    >
    > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/kernel/trace/ftrace.c#n4017
    >
    > 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
    > kallsyms_lookup.

    Never mind, in testing this I had marked the weak function as notrace,
    which was the reason I couldn't add it to the set_ftrace_notrace.

    After removing the notrace, kallsyms_lookup() doesn't make a difference. It
    appears that kallsyms will include overridden weak functions into the size
    of the function before it. I tried:

    ret = kallsyms_lookup(rec->ip, &size, &offset, &modname, str);
    if (!ret || offset > size) {
    seq_printf(m, "no function at %lx", rec->ip);
    } else {
    seq_printf(m, "%s", str);
    if (modname)
    seq_printf(m, " [%s]", modname);
    }

    And it made no difference.

    >
    > This does indeed look like a bug in %ps.
    >

    Yes, this does appear to be a issue with kallsyms in general.

    -- Steve

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