Re: [PATCH] kmemcheck: lazy checking for MOVS instructions

From: Ingo Molnar
Date: Sun Sep 14 2008 - 11:21:59 EST

* Vegard Nossum <vegard.nossum@xxxxxxxxx> wrote:

> On Fri, Sep 12, 2008 at 11:06 AM, Ingo Molnar <mingo@xxxxxxx> wrote:
> >> From: Vegard Nossum <vegard.nossum@xxxxxxxxx>
> >> 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.

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