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Subject: Re: Kernel oops - help interpreting partial trace info
From: Peter Zijlstra <peterz@infradead.org>
To: Samson Yeung <samson@editshare.com>
Cc: Ingo Molnar <mingo@elte.hu>, linux-kernel@vger.kernel.org
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Date: Mon, 03 Jan 2011 10:02:49 +0100
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On Thu, 2010-12-30 at 08:35 -0800, Samson Yeung wrote:
> Code: 00 44 8b 15 23 76 68 00 45 85 d2 74 32 48 8b 50 08 8b 5a 18 48
> 8b 90 90 06 00 00 48 8b 4a 50 48 85 c9 74 1b 48 63 db 48 8b 51 20 <48>
> 03 14 dd 00 fb 74 81 4c 01 32 48 8b 49 58 48 85 c9 75 e8 48
> All code
> ========
>    0:   00 44 8b 15             add    %al,0x15(%rbx,%rcx,4)
>    4:   23 76 68                and    0x68(%rsi),%esi
>    7:   00 45 85                add    %al,-0x7b(%rbp)
>    a:   d2                      (bad)
> ...
> 
> Should (bad) ever be output by decodecode? 

Don't think so, my guess is the decoder started at a non ins boundary
and got confused. "85 d2" is "test %edx, %edx" and is something that
occurs quite frequently in the code. The following 74 is "je", which
makes sense after a "test".

"8b 15 xx xx xx xx" is "movl xx,%edx"

That however does leave us with a 45 unexplained, that's usually part of
a mem argument, its x(%ebp) like stuff.

Dunno really..