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Re: [Xen-devel] garbage registers when domain killed by xen

  • To: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
  • From: Kip Macy <kip.macy@xxxxxxxxx>
  • Date: Sat, 7 May 2005 07:23:24 -0700
  • Cc: xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>
  • Delivery-date: Sat, 07 May 2005 14:23:00 +0000
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  • List-id: Xen developer discussion <xen-devel.lists.xensource.com>

There is an odd relationship between hitting the send button and epiphanies.

Show_guest_stack says the eip is 0 and the stack has eflags, eip, and
CS over and over and over again. That would indicate that I'm running
off my stack by trapping over and over again. However, I don't have
traps or callback handlers installed. What may be happening is xen
setting up a trapframe and then jumping to failsafe callback - over
and over again because jumping to failsafe callback itself causes a
page fault. In this case the eip is legitimately 0 - but not because
of me but because xen isn't checking that I've actually set my
failsafe_callback. I'll go look at FLT14 again to see if I'm on the
right track.


On 5/7/05, Kip Macy <kip.macy@xxxxxxxxx> wrote:
> I'm not sure about ecx/edx but I know eip is bad. There are legitimate
> cases of trying to call a null function pointer, but I know from the
> context that that isn't the case. It appears to be a page fault - but
> I don't have trap handlers installed yet.
>                                                   -Kip
> On 5/7/05, Keir Fraser <Keir.Fraser@xxxxxxxxxxxx> wrote:
> >
> > On 7 May 2005, at 02:26, Kip Macy wrote:
> >
> > > Is it really necessary for xen to overwrite part of a domain's context
> > > on a fatal trap?
> >
> > Which ones are overwritten -- ecx/edx? I'm not sure how that could
> > happen but it's clearly a bug rather than intentional.
> >
> >   -- Keir
> >
> >

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