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SubjectRe: [PATCH] kmemcheck: lazy checking for MOVS instructions
On Fri, Sep 12, 2008 at 11:06 AM, Ingo Molnar <> wrote:
>> From: Vegard Nossum <>
>> 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.



"The animistic metaphor of the bug that maliciously sneaked in while
the programmer was not looking is intellectually dishonest as it
disguises that the error is the programmer's own creation."
-- E. W. Dijkstra, EWD1036

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