linux-kernel - Re: [CFT] ELF Relocatable x86 and x86

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Date:	09 Aug 2006 01:36:33 +0200
From:	Andi Kleen <ak@...e.de>
To:	Don Zickus <dzickus@...hat.com>
Cc:	fastboot@...l.org, Horms <horms@...ge.net.au>,
	Jan Kratochvil <lace@...kratochvil.net>,
	"H. Peter Anvin" <hpa@...or.com>,
	Magnus Damm <magnus.damm@...il.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [CFT] ELF Relocatable x86 and x86_64 bzImages

Don Zickus <dzickus@...hat.com> writes:
> > 
> > Odd.  I wonder if I'm missing a serializing instruction somewhere,
> > to ensure the effects of ``self modifying code'' aren't a problem.
> > As I read Intels Documentation if you have a jump before you get
> > to the code there shouldn't be a problem.
> > 
> > Still that doesn't really explain bytes_out.
> > 

Sounds nasty.

> 
> So I narrowed down the problem but it isn't obvious to me why this problem
> exists.  Basically, even though bytes_out is supposed to be initialized to
> 0, it becomes -1 before entering decompress_kernel().  Of course, the
> fallout is in flush_window() bytes_out wounds up being one less than
> outcnt and hence my original problem.
> 
> Any thoughts on how to debug where this could be getting corrupted?  

Use a simulator (hopefully you can reproduce it in there) like qemu
or AMD SimNow and set a watch point on the address?

Or try to find someone who has a Intel target probe to help you out.

-Andi
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