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Re: [Xen-devel] [PATCH] x86: emulate lea with two register operands correctly

  • To: Tim Deegan <tim@xxxxxxx>
  • From: Keir Fraser <keir@xxxxxxx>
  • Date: Thu, 05 Jan 2012 19:03:09 +0000
  • Cc: xen-devel@xxxxxxxxxxxxxxxxxxx, David Vrabel <david.vrabel@xxxxxxxxxx>
  • Delivery-date: Thu, 05 Jan 2012 19:03:52 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xensource.com>
  • Thread-index: AczL3KndLXDU6P7SUE+ABNSrlChYtA==
  • Thread-topic: [Xen-devel] [PATCH] x86: emulate lea with two register operands correctly

On 05/01/2012 16:06, "Tim Deegan" <tim@xxxxxxx> wrote:

> At 15:49 +0000 on 05 Jan (1325778595), Keir Fraser wrote:
>> On 05/01/2012 15:03, "David Vrabel" <david.vrabel@xxxxxxxxxx> wrote:
>>> An lea instruction with two register operands should raise an
>>> undefined instruction exception.
>>> Skype does such a instruction and will crash when starting if it does
>>> not get the exception.
>> Thanks. I think it is a little nicer to check ea.type != OP_MEM, so I made
>> that change before committing this patch. It's now in xen-unstable staging.
>> It's a bit concerning that we're emulating LEA at all, perhaps. I wonder if
>> a pagetable page has been reused as a code page and we didn't notice yet? Or
>> is there some other reason that skype is getting emulated? :-)
> #UD exceptions in HVM are passed to the emulator (IIRC as part of the
> cross-vendor migration patches, so SYSENTER & friends could be managed).

Duh, good point.

 -- Keir

> Tim.

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