linux-kernel - Re: [3/3] use vmalloc() to arrange guard pages for stacks

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Date:	Tue, 1 May 2007 09:47:02 -0700
From:	Bill Irwin <bill.irwin@...cle.com>
To:	Chuck Ebbert <cebbert@...hat.com>
Cc:	Bill Irwin <bill.irwin@...cle.com>, linux-kernel@...r.kernel.org,
	bunk@...sta.de, akpm@...l.org, gcoady@...il.com, zlynx@....org,
	dgc@....com, alan@...rguk.ukuu.org.uk, andi@...stfloor.org,
	hch@...radead.org, jengelh@...ux01.gwdg.de, zwane@...radead.org,
	neilb@...e.de, jens.axboe@...cle.com, eric@...venscaling.com,
	wli@...omorphy.com
Subject: Re: [3/3] use vmalloc() to arrange guard pages for stacks

Bill Irwin wrote:
>> It's a shame that the resource scalability implications of vmallocspace
>> allocations prevent this from being useful in production. One could, in
>> principle, establish guard pages within ZONE_NORMAL, but for 4KB stacks
>> it's somewhat awkward to dredge up 3 contigous pages, and 4 defeats the
>> purpose. Alignment with 8KB stacks wants 2 contiguous order 1 pages that
>> span an order 2 page boundary. I guess I could rewrite the page allocator
>> (again), but people seem to feel safest with the buddy allocator affairs.
>> BTW, did the original patches for this prove to be of any use to you?

On Tue, May 01, 2007 at 12:40:55PM -0400, Chuck Ebbert wrote:
> No, I never tried them. Seems like I never get to anything these days but
> answering bug reports and merging fixes... Putting the feature in-kernel
> means I might get to use it though. :)

Maybe it's a bit late for whatever bug you were hunting, but at least
it'll help smoke out whatever other stack overflows you or anyone else
might end up chasing down.


-- wli
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