linux-kernel - Re: Valgrinding the kernel?

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Date:	Fri, 06 Jul 2007 12:51:27 -0700
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	Jeff Dike <jdike@...toit.com>
CC:	Dan Kegel <dank@...el.com>, linux-kernel@...r.kernel.org,
	Robert Walsh <rjwalsh@...ables.org>
Subject: Re: Valgrinding the kernel?

Jeff Dike wrote:
> On Fri, Jul 06, 2007 at 10:30:19AM -0700, Dan Kegel wrote:
>   
>> Could you give it a shot?
>>     
>
> OK, after ripping out the code that broke valgrind last time (patch
> below), I get this:
>
> ==27590== Warning: set address range perms: large range 516194304, a 0, v 0
>   

Hm, wonder what that is...

> vex x86->IR: unhandled instruction bytes: 0xF3 0xAF 0x74 0x9
> ==27590== Your program just tried to execute an instruction that Valgrind
> ==27590== did not recognise.  There are two possible reasons for this.
> ==27590== 1. Your program has a bug and erroneously jumped to a non-code
> ==27590==    location.  If you are running Memcheck and you just saw a
> ==27590==    warning about a bad jump, it's probably your program's fault.
> ==27590== 2. The instruction is legitimate but Valgrind doesn't handle it,
> ==27590==    i.e. it's Valgrind's fault.  If you think this is the case or
> ==27590==    you are not sure, please let us know.
> ==27590== Either way, Valgrind will now raise a SIGILL signal which will
> ==27590== probably kill your program.
> ==27590== 
>
>   
>> Maybe the problems after that will be more pedestrian.
>>     
>
> Doesn't look like it.
>
> FWIW, that instruction is repz scas.  In an earlier valgrind effort in
> 2002, I hit repe scas
> (http://www.goop.org/~jeremy/valgrind/76-repe-scas.patch), so maybe
> something similar is needed here.
>   

The virtual CPU code has been competely rewritten since then.  If its a 
non-gcc generated instruction, its possible the new code 
parser/generator hasn't been taught to deal with it.

>> I'm willing to focus a little effort on this.
>>     
>
> I guess you'll have to fix valgrind's various bugs.  See, simple :)
>   

Exactly ;)

    J
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