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Re: [Qemu-devel] [PATCH 4/7] target-i386: Dump illegal opcodes with -d u


From: Richard Henderson
Subject: Re: [Qemu-devel] [PATCH 4/7] target-i386: Dump illegal opcodes with -d unimp
Date: Thu, 3 Mar 2016 11:06:42 -0800
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.6.0

On 03/03/2016 02:08 AM, Paolo Bonzini wrote:
Do you want LOG_UNIMP or LOG_GUEST_ERROR?

I would actually use LOG_IN_ASM.  As you noticed, guests sometimes use
illegal opcodes; another example is Xen's hypercall interface.

On 03/03/2016 07:57, Hervé Poussineau wrote:
This patch is not quiet on some operating systems:
OS/2:
ILLOPC: 000172e1: 0f a6

Windows XP:
ILLOPC: 00020d1a: c4 c4

And very verbose in Windows 3.11, Windows 9x:
ILLOPC: 000ffb17: 63
ILLOPC: 000ffb17: 63

Is it normal?

Yes, it is.  As usual, Raymond Chen explains what's going on:

https://blogs.msdn.microsoft.com/oldnewthing/20041215-00/?p=37003

Wow.  That's... interesting.

I think maybe I'll re-do the patch to distinguish between those opcodes that are completely unrecognized (which is what I was expecting to find) and those that raise #UD due to cpu state (e.g. this arpl in vm86 mode).


r~



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