Re: [PATCH v15 13/25] x86/reboot: Add ljmp instructions to stacktool whitelist

From: Josh Poimboeuf
Date: Wed Jan 20 2016 - 01:10:06 EST


On Tue, Jan 19, 2016 at 09:50:31PM -0800, H. Peter Anvin wrote:
> On 01/19/16 21:42, Josh Poimboeuf wrote:
> >>>>
> >>>> Apparently(?) xen treats the ud2 special when it's followed by "78 65
> >>>> 6e". This is confusing for stacktool because ud2 is normally a dead
> >>>> end, and it thinks the instructions after it will never run.
> >>>>
>
> Cute. UD2 followed by three ASCII characters. I guess that becomes
> really fun when using UD2 + a string for error reporting. Of course, no
> software does that...

Ah, I completely missed the fact that they're ASCII. And it spells
"xen" of course :-)

--
Josh