linux-kernel - Re: [PATCH 2/2] kprobe: fix: Add ftrace_ops_assist

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Date:   Sat, 17 Mar 2018 09:13:34 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Cc:     rostedt <rostedt@...dmis.org>,
        Francis Deslauriers <francis.deslauriers@...icios.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH 2/2] kprobe: fix: Add ftrace_ops_assist_func to kprobe
 blacklist

On Fri, 16 Mar 2018 13:53:01 -0400 (EDT)
Mathieu Desnoyers <mathieu.desnoyers@...icios.com> wrote:

> ----- On Mar 16, 2018, at 12:48 PM, rostedt rostedt@...dmis.org wrote:
> 
> > On Fri, 16 Mar 2018 12:41:34 -0400
> > Steven Rostedt <rostedt@...dmis.org> wrote:
> > 
> >> Yes, kprobes are dangerous. I'm not saying it shouldn't be fixed, I'm
> >> saying that I don't have time to fix it now, but would be happy to
> >> accept patches if someone else does so.
> > 
> > And looking at what I replied before for the original patch. It would
> > probably be a good idea to blacklist directories. Like we do with
> > function tracing. We probably should black list both kernel/tracing and
> > kernel/events from being probed.
> > 
> > Did this come up at plumbers? You were there too, I don't remember
> > discussing it there.
> 
> I don't remember this coming up last Plumbers nor KS neither, given
> that we were focused on other topics.
> 
> Would the general approach you envision be based on emitting all code
> generated by compilation of all objects under kernel/tracing and
> kernel/events into a specific "nokprobes" text section of the kernel ?
> Perhaps we could create a specific linker scripts for those directories,
> or do you have in mind a neater way to do this ?

.kprobes.text section still exists. As I pointed in previous mail, I don't
think we have to put all those code into that section. But if you want,
it is acceptable to have a kconfig which push most of those ftrace related
code into .kprobes.text section.

Thank,

> 
> Thanks,
> 
> Mathieu
> 
> > 
> > -- Steve
> 
> -- 
> Mathieu Desnoyers
> EfficiOS Inc.
> http://www.efficios.com


-- 
Masami Hiramatsu <mhiramat@...nel.org>