linux-kernel - Re: [PATCH -tip v4 0/6] kprobes: introduce NOKPROBE

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Message-ID: <20131205102127.GA19923@gmail.com>
Date:	Thu, 5 Dec 2013 11:21:27 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
Cc:	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Sandeepa Prabhu <sandeepa.prabhu@...aro.org>, x86@...nel.org,
	lkml <linux-kernel@...r.kernel.org>,
	"Steven Rostedt (Red Hat)" <rostedt@...dmis.org>,
	systemtap@...rceware.org, "David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH -tip v4 0/6] kprobes: introduce NOKPROBE_SYMBOL() and
 fixes crash bugs


* Masami Hiramatsu <masami.hiramatsu.pt@...achi.com> wrote:

> > So we need both a maintainable and a sane/safe solution, and I'd 
> > like to apply the whole thing at once and be at ease that the 
> > solution is round. We should have done this years ago.
> 
> For the safeness of kprobes, I have an idea; introduce a whitelist 
> for dynamic events. AFAICS, the biggest unstable issue of kprobes 
> comes from putting *many* probes on the functions called from 
> tracers.

If the number of 'noprobe' annotations is expected to explode then 
maybe another approach should be considered.

For example in perf we detect recursion. Could kprobes do that and 
detect hitting a probe while running kprobes code, and ignore it [do 
an early return]?

That way most of the annotations could be removed and kprobes would 
become inherently safe. Is there any complication I'm missing?

Thanks,

	Ingo
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