linux-kernel - Re: vm86 segfaults with NX bit

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Date:	Thu, 20 Nov 2008 18:05:51 +0100
From:	Takashi Iwai <tiwai@...e.de>
To:	Arjan van de Ven <arjan@...radead.org>
Cc:	linux-kernel@...r.kernel.org, Luc Verhaegen <lverhaegen@...e.de>,
	Egbert Eich <eich@...e.de>
Subject: Re: vm86 segfaults with NX bit

At Thu, 20 Nov 2008 18:01:08 +0100,
I wrote:
> 
> At Thu, 20 Nov 2008 08:58:44 -0800,
> Arjan van de Ven wrote:
> > 
> > On Thu, 20 Nov 2008 16:39:06 +0100
> > Takashi Iwai <tiwai@...e.de> wrote:
> > 
> > > Hi,
> > > 
> > > X guys reported that VESA driver segfaults in vm86 mode with a kernel
> > > with CONFIG_X86_PAE, and it turned to be the NX bit.  See Novell
> > > bugzilla #443440:
> > > 	https://bugzilla.novell.com/show_bug.cgi?id=443440
> > > 
> > > I can confirm that the latest 2.6.28-rc still causes the same problem,
> > > and it disappears when booted with noexec=off option.
> > > 
> > > Also, when NX bit is reset for the first 1MB (or smaller) in
> > > do_sys_vm86(), it also works as expected.  But I have little clue
> > > where to restore the bit again.
> > > 
> > > Any good suggestions / solutions?
> > > 
> > 
> > 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...


thanks,

Takashi
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