linux-kernel - Re: 2.6.22-rc1-mm1

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Message-ID: <4660A7E0.6070600@zytor.com>
Date:	Fri, 01 Jun 2007 16:12:32 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Andy Whitcroft <apw@...dowen.org>
CC:	Mel Gorman <mel@....ul.ie>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Steve Fox <drfickle@...ibm.com>
Subject: Re: 2.6.22-rc1-mm1

Andy Whitcroft wrote:
> 
> I think that my debugging says that newsetup got the compressed kernel
> and decompressor into memory ok and execution passed to it normally.
> But I cannot figure out where the corruption is coming from.  I tried
> annotating the gzip decompressor to see if the input and output buffers
> were overlapping at any time and that debug said no (unsure how reliable
> that is).  And yet at some point the output image is munched up.
> 
> One last piece of information.  The decompressor also always seems to
> get to the end of the input stream in exactly the right place without
> reporting any kind of error, that is with exactly 8 bytes left over for
> the length and crc checks.  Which given the context sensitive nature of
> the algorithm tends to imply the input stream was ok for the whole
> duration of the decompress.  Yet the output stream is badly broken.
> 
> Anyone got any wacky suggestions ...
> 

It definitely sounds like a memory clobber of some sort.

Usual suspects, in addition to the input/output buffers you already
looked at, would be the heap and the stack.  Finding where the stack
pointer lives would be my first, instinctive guess.

	-hpa
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