From: Steven Rostedt <rostedt@goodmis.org>
To: Yafang Shao <laoar.shao@gmail.com>
Cc: Alexei Starovoitov <alexei.starovoitov@gmail.com>,
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@kernel.org>,
Stanislav Fomichev <sdf@google.com>, Hao Luo <haoluo@google.com>,
Jiri Olsa <jolsa@kernel.org>,
Masami Hiramatsu <mhiramat@kernel.org>, bpf <bpf@vger.kernel.org>,
linux-trace-kernel@vger.kernel.org,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH bpf-next 5/6] bpf: Improve tracing recursion prevention mechanism
Date: Thu, 27 Apr 2023 11:46:43 -0400 [thread overview]
Message-ID: <20230427114643.1e3e52aa@gandalf.local.home> (raw)
In-Reply-To: <CALOAHbCvZP1-x7Uc39zUFgLdxxvZUVPY9Eh6bL2vjDx_BZSyug@mail.gmail.com>
On Thu, 27 Apr 2023 23:43:35 +0800
Yafang Shao <laoar.shao@gmail.com> wrote:
> > > I thought that the whole point of this exercise was because the
> > > migrate_disable() itself could be traced (or call something that can), and
> > > that's outside of prog->active protection. Which the test_recursion_*()
> > > code was created for.
> >
> > Not sure where did this come from.
> > migrate_enable/disable were added to deny list back in 2021.
>
> Hi Alexei,
>
> Don't be uneasy. It is not good to play word games.
> What Steven really meant is the preempt_count_{sub, add}.
> Anyway thanks Steven for the help with this exercise.
Right, it was the "(or call something that can)" part that this came from.
As Yafang said, migrate_disable() calls preempt_count_add() (on some
configs) which is traced by ftrace, and thus traced by bpf. Or was that
added to the deny list? I think that was one of the solutions as well.
-- Steve
next prev parent reply other threads:[~2023-04-27 15:46 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-04-17 15:47 [PATCH bpf-next 0/6] bpf: Tracing recursion prevention mechanism improvement Yafang Shao
2023-04-17 15:47 ` [PATCH bpf-next 1/6] bpf: Add __rcu_read_{lock,unlock} into btf id deny list Yafang Shao
2023-04-17 15:47 ` [PATCH bpf-next 2/6] tracing: Add generic test_recursion_try_acquire() Yafang Shao
2023-04-20 6:51 ` Masami Hiramatsu
2023-04-17 15:47 ` [PATCH bpf-next 3/6] tracing: Add the comment for allowing one single recursion in process context Yafang Shao
2023-04-17 15:47 ` [PATCH bpf-next 4/6] selftests/bpf: Allow one single recursion in fentry recursion test Yafang Shao
2023-04-17 15:47 ` [PATCH bpf-next 5/6] bpf: Improve tracing recursion prevention mechanism Yafang Shao
2023-04-17 20:14 ` Alexei Starovoitov
2023-04-18 1:49 ` Yafang Shao
2023-04-18 15:38 ` Alexei Starovoitov
2023-04-19 11:46 ` Yafang Shao
[not found] ` <CAADnVQ+FO-+1OALTtgVkcpH3Adc6xS9qjzORyq2vwVtwY2UoxQ@mail.gmail.com>
2023-04-24 21:40 ` Steven Rostedt
2023-04-27 9:57 ` Yafang Shao
2023-04-27 12:15 ` Yafang Shao
2023-04-27 12:35 ` Yafang Shao
2023-04-17 23:29 ` kernel test robot
2023-04-27 13:26 ` Steven Rostedt
2023-04-27 14:22 ` Yafang Shao
2023-04-27 15:18 ` Steven Rostedt
2023-04-27 15:23 ` Yafang Shao
2023-04-27 15:36 ` Steven Rostedt
2023-04-27 15:39 ` Alexei Starovoitov
2023-04-27 15:43 ` Yafang Shao
2023-04-27 15:46 ` Steven Rostedt [this message]
2023-04-17 15:47 ` [PATCH bpf-next 6/6] bpf: Remove some denied functions from the btf id deny list Yafang Shao
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