linux-kernel - Re: Re: [PATCH 1/5] ftrace: Synchronize variable setting with breakpoints

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Message-ID: <4FC78B45.9060806@hitachi.com>
Date:	Fri, 01 Jun 2012 00:16:21 +0900
From:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	"H. Peter Anvin" <hpa@...or.com>, Dave Jones <davej@...hat.com>,
	Andi Kleen <ak@...ux.intel.com>
Subject: Re: Re: [PATCH 1/5] ftrace: Synchronize variable setting with
 breakpoints

(2012/05/31 23:08), Steven Rostedt wrote:
> Now Masami said he thinks the text_poke should also do the change of
> kernel protection as well, and not do the FIXMAP mapping. At least for
> bulk changes. The added breakpoint code that we have can be shared
> between ftrace and text_poke. That is something we want to do. After we
> get ftrace working, we'll go ahead and make it work for text_poke as
> well ;-)

Indeed, ftrace can be a better test case for breakpoint-based self-
modifying. So after we can make sure that is safely work on x86
widely, it is better to rewrite text_poke with that method.

Perhaps, kprobes-*jump*-optimization may be better to handle it
because the target probe is simultaneously working while
optimizing (modifying code). This means that if someone hits
breakpoint of such kprobe, it must be handled by kprobes, not
only just tweaking IP address.

Thank you,

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