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Re: [Xen-devel] [PATCH] x86_emulate: Always truncate %eip out of long mode

>>> On 11.12.15 at 12:12, <andrew.cooper3@xxxxxxxxxx> wrote:
> On 11/12/15 10:47, Jan Beulich wrote:
>> Furthermore, doesn't this make the wrapping-inside-an-insn
>> situation worse (i.e. what looks broken for 32- and 64-bit modes
>> now gets broken also for 16-bit mode)?
> I don't understand which "broken" you are referring to here.

The (u8) cast on the difference of the two eip values in the
subsequent instruction check hides wraps, and hence an
instruction crossing (not ending at) the 4G or 16E boundary
already goes undetected without your change, but your
change extends the issue to a 16-bit instruction crossing the
64k boundary.


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