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Date: Fri, 28 May 2010 12:05:56 +1000
From: Paul Mackerras <paulus@samba.org>
To: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Subject: Re: [RFC PATCH] powerpc: Emulate nop too
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On Thu, May 27, 2010 at 07:42:03PM +0530, Ananth N Mavinakayanahalli wrote:

> While we are at it, can we also add nop to the list of emulated
> instructions?

I have a patch in development that emulates most of the arithmetic,
logical and shift/rotate instructions, including ori.

While you're here (in a virtual sense at least :), could you explain
what's going on with the emulate_step() call in resume_execution() in
arch/powerpc/kernel/kprobes.c?  It looks like, having decided that
emulate_step() can't handle the instruction, you single-step the
instruction out of line and then call emulate_step again on the same
instruction, in resume_execution().  Why on earth is it trying to
emulate the instruction when it has already been executed at this
point?  Is there any reason why we can't just remove the emulate_step
call from resume_execution()?

Paul.