linux-kernel - Re: [RFC][PATCH] x86: make text

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Message-ID: <20090302183617.GA25105@Krystal>
Date:	Mon, 2 Mar 2009 13:36:17 -0500
From:	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
To:	Arjan van de Ven <arjan@...radead.org>
Cc:	Masami Hiramatsu <mhiramat@...hat.com>,
	Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Nick Piggin <npiggin@...e.de>,
	Steven Rostedt <rostedt@...dmis.org>,
	Andi Kleen <andi@...stfloor.org>, linux-kernel@...r.kernel.org,
	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Rusty Russell <rusty@...tcorp.com.au>,
	"H. Peter Anvin" <hpa@...or.com>,
	Steven Rostedt <srostedt@...hat.com>
Subject: Re: [RFC][PATCH] x86: make text_poke() atomic

* Arjan van de Ven (arjan@...radead.org) wrote:
> > 
> > Use map_vm_area() instead of vmap() in text_poke() for avoiding page
> > allocation and delayed unmapping, and call vunmap_page_range() and
> > local_flush_tlb() directly because this mapping is temporary and
> > local.
> > 
> > At the result of above change, text_poke() becomes atomic and can be
> > called from stop_machine() etc.
> 
> .... but text_poke() realistically needs to call stop_machine() since
> you can't poke live code.... so that makes me wonder how useful this
> is...

Hi Arjan,

Stop machine is not required when inserting a breakpoint. And cleverly
using this breakpoint technique can permit modifying other instructions
as well.

Mathieu

-- 
Mathieu Desnoyers
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F  BA06 3F25 A8FE 3BAE 9A68
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