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SubjectRe: [PATCH 1/2] tracing: kprobes: Prohibit probing on notrace functions
On Fri, 13 Jul 2018 08:18:03 -0400
Steven Rostedt <rostedt@goodmis.org> wrote:

> On Fri, 13 Jul 2018 11:53:01 +0900
> Masami Hiramatsu <mhiramat@kernel.org> wrote:
>
> > On Thu, 12 Jul 2018 13:54:12 -0400
> > Francis Deslauriers <francis.deslauriers@efficios.com> wrote:
> >
> > > From: Masami Hiramatsu <mhiramat@kernel.org>
> > >
> > > Prohibit kprobe-events probing on notrace function.
> > > Since probing on the notrace function can cause recursive
> > > event call. In most case those are just skipped, but
> > > in some case it falls into infinite recursive call.
> >
> > BTW, I'm considering to add an option to allow putting
> > kprobes on notrace function - just for debugging
> > ftrace by kprobes. That is "developer only" option
> > so generally it should be disabled, but for debugging
> > the ftrace, we still need it. Or should I introduce
> > another kprobes module for debugging it?
>
> No, I think the former is better (to add an option to allow putting
> kprobes on notrace functions). By default we let people protect
> themselves. But if then provide a switch that lets you do things that
> might let you shoot yourself in the foot.

I'm adding CONFIG_KPROBE_EVENTS_ON_NOTRACE kconfig which allows
kprobes on notrace function. I think we don't need to make it
online switchable, since it is only good for ftrace developers.

Thank you,

>
> BTW, I'm now leaving on vacation. I'll be back on the 23rd and will be
> looking for patches that I should be pulling in then.
>
> Thanks!
>
> -- Steve


--
Masami Hiramatsu <mhiramat@kernel.org>

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