From: Steven Rostedt <rostedt@goodmis.org>
To: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>,
Jiri Olsa <jolsa@redhat.com>, Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>,
Network Development <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>, Jiri Olsa <olsajiri@gmail.com>
Subject: Re: [PATCH 0/8] bpf: Add fprobe link
Date: Thu, 3 Feb 2022 21:19:54 -0500 [thread overview]
Message-ID: <20220203211954.67c20cd3@gandalf.local.home> (raw)
In-Reply-To: <CAADnVQJfq_10H0V+u0w0rzyZ9uy7vq=T-3BMDANjEN8A3-prsQ@mail.gmail.com>
On Thu, 3 Feb 2022 18:12:11 -0800
Alexei Starovoitov <alexei.starovoitov@gmail.com> wrote:
> > No, fprobe is NOT kprobe on ftrace, kprobe on ftrace is already implemented
> > transparently.
>
> Not true.
> fprobe is nothing but _explicit_ kprobe on ftrace.
> There was an implicit optimization for kprobe when ftrace
> could be used.
> All this new interface is doing is making it explicit.
> So a new name is not warranted here.
>
> > from that viewpoint, fprobe and kprobe interface are similar but different.
>
> What is the difference?
> I don't see it.
IIUC, a kprobe on a function (or ftrace, aka fprobe) gives some extra
abilities that a normal kprobe does not. Namely, "what is the function
parameters?"
You can only reliably get the parameters at function entry. Hence, by
having a probe that is unique to functions as supposed to the middle of a
function, makes sense to me.
That is, the API can change. "Give me parameter X". That along with some
BTF reading, could figure out how to get parameter X, and record that.
-- Steve
next prev parent reply other threads:[~2022-02-04 2:20 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-02 13:53 [PATCH 0/8] bpf: Add fprobe link Jiri Olsa
2022-02-02 13:53 ` [PATCH 1/8] bpf: Add support to attach kprobe program with fprobe Jiri Olsa
2022-02-07 18:59 ` Andrii Nakryiko
2022-02-08 8:56 ` Jiri Olsa
2022-02-02 13:53 ` [PATCH 2/8] bpf: Add bpf_get_func_ip kprobe helper for fprobe link Jiri Olsa
2022-02-07 18:59 ` Andrii Nakryiko
2022-02-07 21:01 ` Alexei Starovoitov
2022-02-09 15:01 ` Jiri Olsa
2022-02-09 16:05 ` Andrii Nakryiko
2022-02-09 19:14 ` Jiri Olsa
2022-02-02 13:53 ` [PATCH 3/8] bpf: Add bpf_cookie support to fprobe Jiri Olsa
2022-02-07 18:59 ` Andrii Nakryiko
2022-02-08 9:07 ` Jiri Olsa
2022-02-08 23:35 ` Andrii Nakryiko
2022-02-08 23:46 ` Jiri Olsa
2022-02-08 23:53 ` Andrii Nakryiko
2022-02-02 13:53 ` [PATCH 4/8] libbpf: Add libbpf__kallsyms_parse function Jiri Olsa
2022-02-07 18:59 ` Andrii Nakryiko
2022-02-08 9:08 ` Jiri Olsa
2022-02-02 13:53 ` [PATCH 5/8] libbpf: Add bpf_link_create support for multi kprobes Jiri Olsa
2022-02-02 13:53 ` [PATCH 6/8] libbpf: Add bpf_program__attach_kprobe_opts " Jiri Olsa
2022-02-07 18:59 ` Andrii Nakryiko
2022-02-08 9:12 ` Jiri Olsa
2022-02-02 13:53 ` [PATCH 7/8] selftest/bpf: Add fprobe attach test Jiri Olsa
2022-02-02 13:53 ` [PATCH 8/8] selftest/bpf: Add fprobe test for bpf_cookie values Jiri Olsa
2022-02-07 18:59 ` Andrii Nakryiko
2022-02-08 9:15 ` Jiri Olsa
2022-02-08 23:24 ` Andrii Nakryiko
2022-02-02 17:09 ` [PATCH 0/8] bpf: Add fprobe link Alexei Starovoitov
2022-02-02 17:24 ` Jiri Olsa
2022-02-02 17:30 ` Alexei Starovoitov
2022-02-03 15:06 ` Jiri Olsa
2022-02-04 0:46 ` Masami Hiramatsu
2022-02-04 1:34 ` Alexei Starovoitov
2022-02-04 2:07 ` Masami Hiramatsu
2022-02-04 2:12 ` Alexei Starovoitov
2022-02-04 2:19 ` Steven Rostedt [this message]
2022-02-04 2:42 ` Alexei Starovoitov
2022-02-04 3:17 ` Masami Hiramatsu
2022-02-04 3:59 ` Masami Hiramatsu
2022-02-15 13:21 ` Jiri Olsa
2022-02-16 18:27 ` Andrii Nakryiko
2022-02-17 14:03 ` Masami Hiramatsu
2022-02-17 22:01 ` Andrii Nakryiko
2022-02-18 4:07 ` Masami Hiramatsu
2022-02-18 19:46 ` Andrii Nakryiko
2022-02-19 2:10 ` Alexei Starovoitov
2022-02-21 7:18 ` Masami Hiramatsu
2022-02-22 12:42 ` Jiri Olsa
2022-02-04 3:14 ` Masami Hiramatsu
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