From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S1758162AbcATGKA (ORCPT <rfc822;w@1wt.eu>);
	Wed, 20 Jan 2016 01:10:00 -0500
Received: from mx1.redhat.com ([209.132.183.28]:39552 "EHLO mx1.redhat.com"
	rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
	id S1758149AbcATGJq (ORCPT <rfc822;linux-kernel@vger.kernel.org>);
	Wed, 20 Jan 2016 01:09:46 -0500
Date: Wed, 20 Jan 2016 00:09:43 -0600
From: Josh Poimboeuf <jpoimboe@redhat.com>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@kernel.org>, Borislav Petkov <bp@alien8.de>,
        Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>,
        x86@kernel.org, linux-kernel@vger.kernel.org,
        live-patching@vger.kernel.org, Michal Marek <mmarek@suse.cz>,
        Peter Zijlstra <peterz@infradead.org>,
        Andy Lutomirski <luto@kernel.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Andi Kleen <andi@firstfloor.org>, Pedro Alves <palves@redhat.com>,
        Namhyung Kim <namhyung@gmail.com>,
        Bernd Petrovitsch <bernd@petrovitsch.priv.at>,
        Chris J Arges <chris.j.arges@canonical.com>,
        Andrew Morton <akpm@linux-foundation.org>, Jiri Slaby <jslaby@suse.cz>,
        Arnaldo Carvalho de Melo <acme@kernel.org>
Subject: Re: [PATCH v15 13/25] x86/reboot: Add ljmp instructions to stacktool
 whitelist
Message-ID: <20160120060943.GA16574@treble.redhat.com>
References: <cover.1450442274.git.jpoimboe@redhat.com>
 <c0c1a92df921961cae5cce208247bb8d8a975d6d.1450442274.git.jpoimboe@redhat.com>
 <20160112164711.GD22699@pd.tnic>
 <20160112174301.GD310@treble.redhat.com>
 <20160113105503.GB11575@gmail.com>
 <20160115060652.GA16760@treble.redhat.com>
 <20160115104145.GC25104@pd.tnic>
 <20160115110000.GB25002@gmail.com>
 <20160120054256.GA31495@treble.redhat.com>
 <569F2027.1070502@zytor.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Disposition: inline
In-Reply-To: <569F2027.1070502@zytor.com>
User-Agent: Mutt/1.5.23.1-rc1 (2014-03-12)
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

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