From: Masami Hiramatsu <mhiramat@kernel.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
x86@kernel.org, Jiri Olsa <jolsa@kernel.org>,
Alexei Starovoitov <ast@kernel.org>,
Andrii Nakryiko <andrii.nakryiko@gmail.com>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>,
netdev@vger.kernel.org, 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>,
Steven Rostedt <rostedt@goodmis.org>,
"Naveen N . Rao" <naveen.n.rao@linux.ibm.com>,
Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>,
"David S . Miller" <davem@davemloft.net>
Subject: Re: [PATCH v13 bpf-next 1/1] rethook: x86: Add rethook x86 implementation
Date: Thu, 24 Mar 2022 00:14:48 +0900 [thread overview]
Message-ID: <20220324001448.c39861064d776973f7811578@kernel.org> (raw)
In-Reply-To: <20220323123454.GW8939@worktop.programming.kicks-ass.net>
On Wed, 23 Mar 2022 13:34:54 +0100
Peter Zijlstra <peterz@infradead.org> wrote:
> On Wed, Mar 23, 2022 at 08:41:19PM +0900, Masami Hiramatsu wrote:
>
> > > Also, what's rethook for anyway?
> >
> > Rethook is a feature which hooks the function return. Most of the
> > logic came from the kretprobe. Simply to say, 'kretprobe - kprobe' is
> > the rethook :)
>
> I got that far, but why did you take the bother to do these patches? Why
> wasn't 'use kretprobe' a good enough option?
Ah, sorry about lacking the background story.
Actually this came from Jiri's request of multiple kprobe for bpf[1].
He tried to solve an issue that starting bpf with multiple kprobe will
take a long time because bpf-kprobe will wait for RCU grace period for
sync rcu events.
Jiri wanted to attach a single bpf handler to multiple kprobes and
he tried to introduce multiple-probe interface to kprobe. So I asked
him to use ftrace and kretprobe-like hook if it is only for the
function entry and exit, instead of adding ad-hoc interface
to kprobes. So I introduced fprobe (kprobe like interface for ftrace)
and rethook (this is a generic return hook feature for fprobe exit handler)[2].
[1] https://lore.kernel.org/all/20220104080943.113249-1-jolsa@kernel.org/T/#u
[2] https://lore.kernel.org/all/164191321766.806991.7930388561276940676.stgit@devnote2/T/#u
This is the reason why I need to split the kretprobe's trampoline as
rethook. Kretprobe is only for probing a single function entry/exit,
thus it does not suit for this purpose.
Thank you,
--
Masami Hiramatsu <mhiramat@kernel.org>
next prev parent reply other threads:[~2022-03-23 15:15 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-23 2:34 [PATCH v13 bpf-next 0/1] fprobe: Introduce fprobe function entry/exit probe Masami Hiramatsu
2022-03-23 2:34 ` [PATCH v13 bpf-next 1/1] rethook: x86: Add rethook x86 implementation Masami Hiramatsu
2022-03-23 8:05 ` Peter Zijlstra
2022-03-23 11:41 ` Masami Hiramatsu
2022-03-23 12:34 ` Peter Zijlstra
2022-03-23 15:14 ` Masami Hiramatsu [this message]
2022-03-25 2:03 ` Alexei Starovoitov
2022-03-25 2:21 ` Masami Hiramatsu
2022-03-25 2:41 ` Alexei Starovoitov
2022-03-23 5:42 ` [PATCH v13 bpf-next 0/1] fprobe: Introduce fprobe function entry/exit probe Masami Hiramatsu
2022-03-23 14:18 ` Mark Rutland
2022-03-23 14:55 ` Masami Hiramatsu
2022-03-23 16:47 ` Mark Rutland
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