linux-kernel - Re: Immediate values

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Message-ID: <20090925085119.2b77ea04@infradead.org>
Date:	Fri, 25 Sep 2009 08:51:19 +0200
From:	Arjan van de Ven <arjan@...radead.org>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	"H. Peter Anvin" <hpa@...or.com>,
	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>,
	Jason Baron <jbaron@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Steven Rostedt <rostedt@...dmis.org>, Andi Kleen <ak@...e.de>,
	linux-kernel@...r.kernel.org
Subject: Re: Immediate values

On Thu, 24 Sep 2009 21:34:22 +0200
Ingo Molnar <mingo@...e.hu> wrote:

> 
> * H. Peter Anvin <hpa@...or.com> wrote:
> 
> > I would like to get an official ACK or NAK for this patching
> > technique from inside Intel, and preferrably from AMD as well.  If
> > it does work as described it would provide a very clean way to do
> > one-shot alternative functions, which probably would be higher
> > value than immediate data values.
> 
> Sounds tempting. Things like the CONFIG_SECURITY hookery could use it?
> 
> But ... since it's patched under stopmachine, is there any reason why 
> this wouldnt work?
> 

stopmachine is fine.

more aggressive tricks are rather dicey.

(cross modifying code that's being executed in ring 0 is ... not
something CPU designers had in mind)

-- 
Arjan van de Ven 	Intel Open Source Technology Centre
For development, discussion and tips for power savings, 
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