From: Steven Rostedt <rostedt@goodmis.org>
To: Andrii Nakryiko <andrii.nakryiko@gmail.com>
Cc: Alexei Starovoitov <alexei.starovoitov@gmail.com>,
Masami Hiramatsu <mhiramat@kernel.org>,
Jiri Olsa <jolsa@kernel.org>, Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>,
Networking <netdev@vger.kernel.org>, bpf <bpf@vger.kernel.org>,
lkml <linux-kernel@vger.kernel.org>,
Martin KaFai Lau <kafai@fb.com>, Song Liu <songliubraving@fb.com>,
Yonghong Song <yhs@fb.com>,
John Fastabend <john.fastabend@gmail.com>,
KP Singh <kpsingh@chromium.org>
Subject: Re: [RFC bpf-next 4/4] selftests/bpf: Add attach bench test
Date: Thu, 28 Apr 2022 20:09:45 -0400 [thread overview]
Message-ID: <20220428200945.5f6a5ba2@gandalf.local.home> (raw)
In-Reply-To: <20220428195303.6295e90b@gandalf.local.home>
On Thu, 28 Apr 2022 19:53:03 -0400
Steven Rostedt <rostedt@goodmis.org> 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
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.
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
next prev parent reply other threads:[~2022-04-29 0:09 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-07 12:52 [RFC bpf-next 0/4] bpf: Speed up symbol resolving in kprobe multi link Jiri Olsa
2022-04-07 12:52 ` [RFC bpf-next 1/4] kallsyms: Add kallsyms_lookup_names function Jiri Olsa
2022-04-08 0:57 ` Masami Hiramatsu
2022-04-13 7:27 ` Jiri Olsa
2022-04-08 23:19 ` Alexei Starovoitov
2022-04-09 20:24 ` Jiri Olsa
2022-04-12 20:46 ` Jiri Olsa
2022-04-15 0:47 ` Masami Hiramatsu
2022-04-15 22:39 ` Jiri Olsa
2022-04-11 22:15 ` Andrii Nakryiko
2022-04-12 20:28 ` Jiri Olsa
2022-04-07 12:52 ` [RFC bpf-next 2/4] fprobe: Resolve symbols with kallsyms_lookup_names Jiri Olsa
2022-04-08 0:58 ` Masami Hiramatsu
2022-04-07 12:52 ` [RFC bpf-next 3/4] bpf: Resolve symbols with kallsyms_lookup_names for kprobe multi link Jiri Olsa
2022-04-08 23:26 ` Alexei Starovoitov
2022-04-09 20:24 ` Jiri Olsa
2022-04-11 22:15 ` Andrii Nakryiko
2022-04-11 22:15 ` Andrii Nakryiko
2022-04-12 18:42 ` Jiri Olsa
2022-04-07 12:52 ` [RFC bpf-next 4/4] selftests/bpf: Add attach bench test Jiri Olsa
2022-04-11 22:15 ` Andrii Nakryiko
2022-04-12 0:49 ` Masami Hiramatsu
2022-04-12 22:51 ` Andrii Nakryiko
2022-04-16 14:21 ` Masami Hiramatsu
2022-04-18 17:33 ` Steven Rostedt
2022-04-28 13:58 ` Steven Rostedt
2022-04-28 13:59 ` Steven Rostedt
2022-04-28 18:59 ` Alexei Starovoitov
2022-04-28 20:05 ` Steven Rostedt
2022-04-28 23:32 ` Andrii Nakryiko
2022-04-28 23:53 ` Steven Rostedt
2022-04-29 0:09 ` Steven Rostedt [this message]
2022-04-29 0:31 ` Steven Rostedt
2022-04-13 16:44 ` Steven Rostedt
2022-04-13 16:45 ` Andrii Nakryiko
2022-04-13 16:59 ` Steven Rostedt
2022-04-13 19:02 ` Andrii Nakryiko
2022-04-12 15:44 ` Jiri Olsa
2022-04-12 22:59 ` Andrii Nakryiko
2022-04-08 23:29 ` [RFC bpf-next 0/4] bpf: Speed up symbol resolving in kprobe multi link Alexei Starovoitov
2022-04-09 20:24 ` Jiri Olsa
2022-04-11 22:15 ` Andrii Nakryiko
2022-04-11 22:18 ` Alexei Starovoitov
2022-04-11 22:21 ` Andrii Nakryiko
2022-04-12 15:46 ` Jiri Olsa
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