From: Andrea Righi <righi.andrea@gmail.com>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>,
Ingo Molnar <mingo@redhat.com>,
peterz@infradead.org,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 0/2] kprobes: Fix kretprobe incorrect stacking order problem
Date: Mon, 7 Jan 2019 22:34:39 +0100 [thread overview]
Message-ID: <20190107213439.GD5966@xps-13> (raw)
In-Reply-To: <20190107162833.1e034fc7@gandalf.local.home>
On Mon, Jan 07, 2019 at 04:28:33PM -0500, Steven Rostedt wrote:
> On Mon, 7 Jan 2019 22:19:04 +0100
> Andrea Righi <righi.andrea@gmail.com> wrote:
>
> > > > If we put a kretprobe to raw_spin_lock_irqsave() it looks like
> > > > kretprobe is going to call kretprobe...
> > >
> > > Right, but we should be able to add some recursion protection to stop
> > > that. I have similar protection in the ftrace code.
> >
> > If we assume that __raw_spin_lock/unlock*() are always inlined a
>
> I wouldn't assume that.
>
> > possible way to prevent this recursion could be to use directly those
> > functions to do locking from the kretprobe trampoline.
> >
> > But I'm not sure if that's a safe assumption... if not I'll see if I can
> > find a better solution.
>
> All you need to do is have a per_cpu variable, where you just do:
>
> preempt_disable_notrace();
> if (this_cpu_read(kprobe_recursion))
> goto out;
> this_cpu_inc(kprobe_recursion);
> [...]
> this_cpu_dec(kprobe_recursion);
> out:
> preempt_enable_notrace();
>
> And then just ignore any kprobes that trigger while you are processing
> the current kprobe.
>
> Something like that. If you want (or if it already happens) replace
> preempt_disable() with local_irq_save().
Oh.. definitely much better. I'll work on that and send a new patch.
Thanks for the suggestion!
-Andrea
next prev parent reply other threads:[~2019-01-07 21:34 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-07 13:31 [PATCH 0/2] kprobes: Fix kretprobe incorrect stacking order problem Masami Hiramatsu
2019-01-07 13:32 ` [PATCH 1/2] x86/kprobes: Verify stack frame on kretprobe Masami Hiramatsu
2019-01-07 13:32 ` [PATCH 2/2] kprobes: Mark ftrace mcount handler functions nokprobe Masami Hiramatsu
2019-01-07 14:55 ` Andrea Righi
2019-01-07 17:29 ` Steven Rostedt
2019-01-08 2:41 ` Masami Hiramatsu
2019-01-08 2:40 ` Masami Hiramatsu
2019-01-07 17:23 ` kbuild test robot
2019-01-07 17:38 ` kbuild test robot
2019-01-07 17:28 ` [PATCH 0/2] kprobes: Fix kretprobe incorrect stacking order problem Andrea Righi
2019-01-07 18:34 ` Andrea Righi
2019-01-07 19:27 ` Steven Rostedt
2019-01-07 19:52 ` Andrea Righi
2019-01-07 19:59 ` Steven Rostedt
2019-01-07 21:19 ` Andrea Righi
2019-01-07 21:28 ` Steven Rostedt
2019-01-07 21:34 ` Andrea Righi [this message]
2019-01-08 2:56 ` Masami Hiramatsu
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20190107213439.GD5966@xps-13 \
--to=righi.andrea@gmail.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mathieu.desnoyers@efficios.com \
--cc=mhiramat@kernel.org \
--cc=mingo@redhat.com \
--cc=peterz@infradead.org \
--cc=rostedt@goodmis.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).