linux-kernel - Re: [PATCH] Support for unconditional page sanitization

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Date:	Sun, 24 May 2009 09:38:51 -0700
From:	Arjan van de Ven <arjan@...radead.org>
To:	pageexec@...email.hu
Cc:	"Larry H." <research@...reption.com>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Ingo Molnar <mingo@...e.hu>, Rik van Riel <riel@...hat.com>,
	linux-kernel@...r.kernel.org, Linus Torvalds <torvalds@...l.org>,
	linux-mm@...ck.org, Ingo Molnar <mingo@...hat.com>
Subject: Re: [PATCH] Support for unconditional page sanitization

On Sun, 24 May 2009 12:19:48 +0200
pageexec@...email.hu wrote:

> On 23 May 2009 at 14:05, Arjan van de Ven wrote:
> 
> > On Sat, 23 May 2009 11:21:41 -0700
> > "Larry H." <research@...reption.com> wrote:
> > 
> > > +static inline void sanitize_highpage(struct page *page)
> > 
> > any reason we're not reusing clear_highpage() for this?
> > (I know it's currently slightly different, but that is fixable)
> 
> KM_USER0 users are not supposed to be called from soft/hard irq
> contexts for high memory pages, something that cannot be guaranteed
> at this low level of page freeing (i.e., we could be interrupting
> a clear_highmem and overwrite its KM_USER0 mapping, leaving it dead
> in the water when we return there). in other words, sanitization
> must be able to nest within KM_USER*, so that pretty much calls for
> its own slot.

no arguement that current clear_highpage isn't a fit. I was more
thinking about using the content of sanitize_highpage(), and just
calling that clear_highpage(). (or in other words, improve
clear_highpage to be usable in more situations)


-- 
Arjan van de Ven 	Intel Open Source Technology Centre
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