linux-kernel - Re: [PATCH] kmemcheck: lazy checking for MOVS instructions

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Date:	Sun, 14 Sep 2008 17:21:36 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Vegard Nossum <vegard.nossum@...il.com>
Cc:	linux-kernel@...r.kernel.org,
	Pekka Enberg <penberg@...helsinki.fi>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] kmemcheck: lazy checking for MOVS instructions


* Vegard Nossum <vegard.nossum@...il.com> wrote:

> On Fri, Sep 12, 2008 at 11:06 AM, Ingo Molnar <mingo@...e.hu> wrote:
> >> From: Vegard Nossum <vegard.nossum@...il.com>
> >> Date: Thu, 11 Sep 2008 17:31:07 +0200
> >> Subject: [PATCH] kmemcheck: lazy checking for MOVS instructions
> >>
> >> This patch adds the support for lazy (as opposed to eager) checking
> >> for [REP] MOVS instructions (mostly used in memcpy()). This means that
> >> if both the source and destination addresses are tracked by kmemcheck,
> >> we copy the shadow memory instead of checking that it is initialized.
> >>
> >> In this way, we get rid of a few more false positives.
> >
> > looks good to me. I've applied it to tip/kmemcheck - but can zap it and
> > pull your for-tip branch as well.
> 
> Please zap, I believe it contains an error :-)
> 
> In short, when reading/writing the shadow memory of the second page in 
> a page-boundary-crossing memory access, the offsets into the second 
> shadow page will be wrong (off by up to 8 bytes). It's a pretty 
> obscure case, but it would be nice to have it fixed. Will send a pull 
> request later.

ok, zapped it.

	Ingo
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