Message-ID: <40BF501D.5080402@redhat.com>
Date: Thu, 03 Jun 2004 09:21:49 -0700
From: Ulrich Drepper <drepper@redhat.com>
Organization: Red Hat, Inc.
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To: Ingo Molnar <mingo@elte.hu>
CC: linux-kernel@vger.kernel.org
Subject: Re: [announce] [patch] NX (No eXecute) support for x86, 2.6.7-rc2-bk2
References: <20040602205025.GA21555@elte.hu> <Pine.LNX.4.58.0406021411030.3403@ppc970.osdl.org> <20040603072146.GA14441@elte.hu>
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Ingo Molnar wrote:
> gcc's
> PT_GNU_STACK mechanism is very conservative - e.g. if an application
> does an asm() then gcc assumes that it might rely on stack executability
> and emits the X flag. 

Actually, this isn't the case.  asm() alone don't trigger this.  There
are far too many of them in use.  And there never has been a reported
problem.  Only trampolines etc cause gcc to automatically request the X
flag to be set.  In case an asm() indeed causes problems the user can
pass the --execstack option to the linker.

It's all explained in

  http://people.redhat.com/drepper/nonselsec.pdf

-- 
➧ Ulrich Drepper ➧ Red Hat, Inc. ➧ 444 Castro St ➧ Mountain View, CA ❖
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