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From:   Andrii Nakryiko <andrii.nakryiko@gmail.com>
Date:   Thu, 17 Mar 2022 15:03:33 -0700
Message-ID: <CAEf4BzaN_HnyAkVYeUmYoxvW01cFKR2FW0MwZJBL3gvkRw0TYg@mail.gmail.com>
Subject: Re: [for-next][PATCH 03/13] fprobe: Add ftrace based probe APIs
To:     Steven Rostedt <rostedt@goodmis.org>
Cc:     open list <linux-kernel@vger.kernel.org>,
        Ingo Molnar <mingo@kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Jiri Olsa <jolsa@kernel.org>,
        Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Andrii Nakryiko <andrii@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>,
        "Naveen N . Rao" <naveen.n.rao@linux.ibm.com>,
        Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>,
        "David S . Miller" <davem@davemloft.net>,
        Masami Hiramatsu <mhiramat@kernel.org>
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On Thu, Mar 17, 2022 at 8:25 AM Steven Rostedt <rostedt@goodmis.org> wrote:
>
> From: Masami Hiramatsu <mhiramat@kernel.org>
>
> The fprobe is a wrapper API for ftrace function tracer.
> Unlike kprobes, this probes only supports the function entry, but this
> can probe multiple functions by one fprobe. The usage is similar, user
> will set their callback to fprobe::entry_handler and call
> register_fprobe*() with probed functions.
> There are 3 registration interfaces,
>
>  - register_fprobe() takes filtering patterns of the functin names.
>  - register_fprobe_ips() takes an array of ftrace-location addresses.
>  - register_fprobe_syms() takes an array of function names.
>
> The registered fprobes can be unregistered with unregister_fprobe().
> e.g.
>
> struct fprobe fp = { .entry_handler = user_handler };
> const char *targets[] = { "func1", "func2", "func3"};
> ...
>
> ret = register_fprobe_syms(&fp, targets, ARRAY_SIZE(targets));
>
> ...
>
> unregister_fprobe(&fp);
>
> Link: https://lkml.kernel.org/r/164735283857.1084943.1154436951479395551.stgit@devnote2
>
> Cc: Jiri Olsa <jolsa@kernel.org>
> Cc: Alexei Starovoitov <ast@kernel.org>
> Cc: Andrii Nakryiko <andrii.nakryiko@gmail.com>
> Cc: Daniel Borkmann <daniel@iogearbox.net>
> Cc: Andrii Nakryiko <andrii@kernel.org>
> Cc: Martin KaFai Lau <kafai@fb.com>
> Cc: Song Liu <songliubraving@fb.com>
> Cc: Yonghong Song <yhs@fb.com>
> Cc: John Fastabend <john.fastabend@gmail.com>
> Cc: KP Singh <kpsingh@chromium.org>
> Cc: "Naveen N . Rao" <naveen.n.rao@linux.ibm.com>
> Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
> Cc: "David S . Miller" <davem@davemloft.net>
> Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
> ---

Hey Steven!

Do I understand correctly that this patch set was applied in your
tree? I was under the impression that we agreed to route this through
the bpf-next tree earlier (see [0]), but I might have misunderstood
something, sorry.

Either way, the reason it matters is because Jiri's multi-attach
kprobe patch set ([1]) is depending on Masami's patches and having
fprobe patches in bpf-next tree would simplify logistics
significantly.

So I wonder if it's still possible to route it through bpf-next?

If not, we'd need a way to get these changes into the bpf-next tree
somehow. Having it in a separate branch that we can merge would be a
way to go about this, I presume? But it's certainly a more complicated
way, so it would be preferable to back it out and land through
bpf-next.

Please let me know how we should proceed. Thanks!

  [0] https://lore.kernel.org/bpf/CAEf4BzaugZWf6f_0JzA-mqaGfp52tCwEp5dWdhpeVt6GjDLQ3Q@mail.gmail.com/
  [1] https://lore.kernel.org/bpf/20220316122419.933957-1-jolsa@kernel.org/

>  include/linux/fprobe.h |  87 +++++++++++++++++
>  kernel/trace/Kconfig   |  12 +++
>  kernel/trace/Makefile  |   1 +
>  kernel/trace/fprobe.c  | 211 +++++++++++++++++++++++++++++++++++++++++
>  4 files changed, 311 insertions(+)
>  create mode 100644 include/linux/fprobe.h
>  create mode 100644 kernel/trace/fprobe.c
>

[...]