linux-kernel - Re: 32bit binaries on x86_64/Xen segfaults in syscall-vdso

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Date:	Fri, 04 Sep 2009 09:56:54 -0700
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	Bastian Blank <waldi@...ian.org>, linux-kernel@...r.kernel.org,
	xen-devel@...ts.xensource.com, 544145@...s.debian.org,
	Keir Fraser <keir.fraser@...citrix.com>
Subject: Re: 32bit binaries on x86_64/Xen segfaults in syscall-vdso

On 09/04/09 09:20, Bastian Blank wrote:
> On Fri, Sep 04, 2009 at 09:07:39AM -0700, Jeremy Fitzhardinge wrote:
>   
>> But for some reason that's triggering a failsafe callback, which invokes
>> a GP.
>>     
> Hmm, not in my tests. It always returned to userspace correctly and died
> some operations later, usually the "ret". This then produced either a
> segfault (unreadable address), sigill (if it managed to reach the ELF
> header of the ld.so) or a GPF.

Hm, I may have misdiagnosed it then.  Your symptoms are odd; either its
landing back in userspace in the right place but then stumbles on for a
while before crashing (wrong processor mode?) or the eip is wrong and
its just landing in the wrong place and crashing immediately. 

How non-deterministic is it?  Does it differ every time, or from boot to
boot, build to build?

    J

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