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

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Date:	Fri, 13 Dec 2013 15:06:06 +0900
From:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To:	Ingo Molnar <mingo@...nel.org>
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: Re: Re: [PATCH -tip v4 0/6] kprobes: introduce NOKPROBE_SYMBOL()
 and fixes crash bugs

(2013/12/13 14:34), Masami Hiramatsu wrote:
>> Lets assume we allow a probe to be inserted in the single-step path. 
>> Such a probe will be an INT3 instruction and if it hits we get a 
>> recursive INT3 invocation. In that case the INT3 handler should simply
>> restore the original instruction and _leave it so_. There's no 
>> single-stepping needed - the probe is confused and must be discarded.
> 
> But how can we restore the protected kernel text?
> If we use text_poke, we also need to prohibit probing on the text_poke
> and functions called in the text_poke too. That just shifts the annotated
> area to the text_poke. :(

BTW, currently we mark the text_poke as nokprobe_symbol, but it should be
removed. We don't call it from kprobes int3/debug handlers.

The patches which removes __kprobes in this series are only for kprobe
related files (arch/x86/kernel/kprobes/* or kernel/kprobes.c.) I think
we should do it for other parts.
Is it better to do that on this series?

Thank you,

-- 
Masami HIRAMATSU
IT Management Research Dept. Linux Technology Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@...achi.com


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