From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner+w=401wt.eu-S1755986AbYKULix@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S1755986AbYKULix (ORCPT <rfc822;w@1wt.eu>);
	Fri, 21 Nov 2008 06:38:53 -0500
Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753235AbYKULip
	(ORCPT <rfc822;linux-kernel-outgoing>);
	Fri, 21 Nov 2008 06:38:45 -0500
Received: from mx1.suse.de ([195.135.220.2]:37872 "EHLO mx1.suse.de"
	rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
	id S1751909AbYKULio (ORCPT <rfc822;linux-kernel@vger.kernel.org>);
	Fri, 21 Nov 2008 06:38:44 -0500
Date: Fri, 21 Nov 2008 12:38:42 +0100
Message-ID: <s5hprkp8g1p.wl%tiwai@suse.de>
From: Takashi Iwai <tiwai@suse.de>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: Arjan van de Ven <arjan@infradead.org>, linux-kernel@vger.kernel.org,
       Luc Verhaegen <lverhaegen@suse.de>, Egbert Eich <eich@suse.de>
Subject: Re: vm86 segfaults with NX bit
In-Reply-To: <4925D596.3010304@zytor.com>
References: <s5hmyfu9zl1.wl%tiwai@suse.de>
	<20081120085844.6f158e08@infradead.org>
	<s5h3ahm9vsb.wl%tiwai@suse.de>
	<s5hzlju8h00.wl%tiwai@suse.de>
	<4925D596.3010304@zytor.com>
User-Agent: Wanderlust/2.12.0 (Your Wildest Dreams) SEMI/1.14.6 (Maruoka)
 FLIM/1.14.7 (=?ISO-8859-4?Q?Sanj=F2?=) APEL/10.6 Emacs/22.3
 (x86_64-suse-linux-gnu) MULE/5.0 (SAKAKI)
MIME-Version: 1.0 (generated by SEMI 1.14.6 - "Maruoka")
Content-Type: text/plain; charset=US-ASCII
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

At Thu, 20 Nov 2008 13:24:38 -0800,
H. Peter Anvin wrote:
> 
> Takashi Iwai wrote:
> >>>>
> >>> did the code that mapped this memory setup use PROT_EXEC ?
> >> A good question...
> >> Luc, Egbert, how does VESA driver handle it?
> > 
> > Just looking through the vesa directory of xorg-server code, PROT_EXEC
> > is passed for all mappings, at least.
> > 
> > Please correct me if I'm looking at a wrong place...
> > 
> 
> Please do an strace of the X server startup up to the point of the crash.

Well, it's not exactly a crash.  VESA driver catches SIGSEGV in its
signal handler, spews the error messages and skips the vm86
operation.  The segfault occurs during every vm86old syscall.

> I am betting that PROT_EXEC is missing from an mmap(), or that it needs 
> an additional mprotect().

PROT_EXEC seems used in every mmap.  But, VESA and int10 codes in
xorg is old and hard to follow for me.

Hopefully Egbert can give us a better insight...


Takashi