[<prev] [next>] [<thread-prev] [day] [month] [year] [list]
Message-ID: <20230427114643.1e3e52aa@gandalf.local.home>
Date: Thu, 27 Apr 2023 11:46:43 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: Yafang Shao <laoar.shao@...il.com>
Cc: Alexei Starovoitov <alexei.starovoitov@...il.com>,
Alexei Starovoitov <ast@...nel.org>,
Daniel Borkmann <daniel@...earbox.net>,
Andrii Nakryiko <andrii@...nel.org>,
Martin KaFai Lau <kafai@...com>,
Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
John Fastabend <john.fastabend@...il.com>,
KP Singh <kpsingh@...nel.org>,
Stanislav Fomichev <sdf@...gle.com>,
Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>,
Masami Hiramatsu <mhiramat@...nel.org>,
bpf <bpf@...r.kernel.org>, linux-trace-kernel@...r.kernel.org,
LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH bpf-next 5/6] bpf: Improve tracing recursion prevention
mechanism
On Thu, 27 Apr 2023 23:43:35 +0800
Yafang Shao <laoar.shao@...il.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
Powered by blists - more mailing lists