Hi!
> 2. Prior to writing any of the image, also set up new 4k page tables
> such that an attempt to make a change to any of the pages we're about to
> write to disk will result in a page fault, giving us an opportunity to
> flag the page as needing an atomic copy later. Once this is done, write
> protection for the page can be disabled and the write that caused the
> fault allowed to proceed.
Tricky.
page faulting code touches memory, too...
--
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(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
Hi.
On 30/05/10 15:25, Pavel Machek wrote:
> Hi!
>
>> 2. Prior to writing any of the image, also set up new 4k page tables
>> such that an attempt to make a change to any of the pages we're about to
>> write to disk will result in a page fault, giving us an opportunity to
>> flag the page as needing an atomic copy later. Once this is done, write
>> protection for the page can be disabled and the write that caused the
>> fault allowed to proceed.
>
> Tricky.
>
> page faulting code touches memory, too...
Yeah. I realise we'd need to make the pages that are used to record the
faults be unprotected themselves. I'm imagining a bitmap for that.
Do you see any reason that it could be inherently impossible? That's
what I really want to know before (potentially) wasting time trying it.
Regards,
Nigel