linux-kernel - Re: Immediate values

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Message-ID: <OF19654CE4.D069FD43-ON8025763C.0037FB4D-8025763C.00389751@uk.ibm.com>
Date:	Fri, 25 Sep 2009 11:18:07 +0100
From:	Richard J Moore <richardj_moore@...ibm.com>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
Cc:	Andi Kleen <ak@...e.de>,
	Anton Massoud <anton.massoud@...csson.com>,
	Arjan van de Ven <arjan@...radead.org>,
	Dominique Toupin <dominique.toupin@...csson.com>,
	"H. Peter Anvin" <hpa@...or.com>, Jason Baron <jbaron@...hat.com>,
	Jim Keniston <jkenisto@...ibm.com>,
	linux-kernel@...r.kernel.org,
	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>,
	Masami Hiramatsu <mhiramat@...hat.com>,
	Ingo Molnar <mingo@...e.hu>,
	Nathan Sidwell <nathan@...esourcery.com>,
	Prasanna S Panchamukhi <prasanna@...ibm.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Rusty Lynch <rusty.lynch@...el.com>,
	Suparna Bhattacharya <suparna@...ibm.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Vamsi Krishna S <vamsi_krishna@...ibm.com>
Subject: Re: Immediate values



Alan Cox <alan@...rguk.ukuu.org.uk> wrote on 25/09/2009 11:02:06:


>
> There was considerable discussion abut this when the kprobe stuff went
> in. If I remember rightly it was stated by someone @intel.com then that
> int3 was ok (even though its not strictly documented as such). The same
> is not true for all instructions on all x86 processors unfortunately.
>
> Alan

Alan, I had that discussion with Intel, and yes int3 is a special case
because of the interrupt processing associated with it. The discussion
went along this lines: int3 is practically useless in an MP environment
if it's trouble by the cross-modifying erratum.

I suppose it is possible the more recent microarchitectures have
changed things. And yes, we might need to have that conversation again.

Richard



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