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Date: Tue, 24 Nov 2009 03:20:00 -0000
From: Frederic Weisbecker <fweisbec@gmail.com>
To: Masami Hiramatsu <mhiramat@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>, 	Ananth N Mavinakayanahalli <ananth@in.ibm.com>, 	lkml <linux-kernel@vger.kernel.org>, 	"H. Peter Anvin" <hpa@zytor.com>, 	Jim Keniston <jkenisto@us.ibm.com>, 	Srikar Dronamraju <srikar@linux.vnet.ibm.com>, 	Christoph Hellwig <hch@infradead.org>, 	Steven Rostedt <rostedt@goodmis.org>, 	Anders Kaseorg <andersk@ksplice.com>, 	Tim Abbott <tabbott@ksplice.com>, Andi Kleen <andi@firstfloor.org>, 	Jason Baron <jbaron@redhat.com>, 	Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>, 	systemtap <systemtap@sources.redhat.com>, 	DLE <dle-develop@lists.sourceforge.net>
Subject: Re: [PATCH -tip v5 00/10] kprobes: Kprobes jump optimization 	support
Message-ID: <20091124032008.GD6752@nowhere>
References: <20091123232115.22071.71558.stgit@dhcp-100-2-132.bos.redhat.com> <20091124020315.GA6221@nowhere>
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On Tue, Nov 24, 2009 at 03:03:19AM +0100, Frederic Weisbecker wrote:
> On Mon, Nov 23, 2009 at 06:21:16PM -0500, Masami Hiramatsu wrote:
> >   When the optimized-kprobe is hit before optimization, its handler
> >  changes IP(instruction pointer) to copied code and exits. So, the
> >  instructions which were copied to detour buffer are executed on the detour
> >  buffer.
> 
> 
> 
> Hm, why is it playing such hybrid game there?
> If I understand well, we have executed int 3, executed the
> handler and we jump back to the detour buffer?
> 


I got it, I think. We have instructions to patch. And the above
turn this area into dead code, safe to patch.

But still, stop_machine() seem to make it not necessary anymore.