linux-kernel - Re: [PATCH v4] [x86] detect and report lack of NX protections

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Message-ID: <4AF99F0C.2050806@zytor.com>
Date:	Tue, 10 Nov 2009 09:12:44 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Kees Cook <kees.cook@...onical.com>
CC:	Arjan van de Ven <arjan@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, x86@...nel.org,
	Pekka Enberg <penberg@...helsinki.fi>,
	Jan Beulich <jbeulich@...ell.com>,
	Vegard Nossum <vegardno@....uio.no>,
	Yinghai Lu <yinghai@...nel.org>,
	Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4] [x86] detect and report lack of NX protections

On 11/10/2009 08:57 AM, Kees Cook wrote:
> 
> 64-bit does not set nx_enabled to "1" by default anywhere.  And setting
> the default to 1 in check_efer() seemed out of place to me.
> 

If it doesn't set nx_enabled anywhere, you'll end up with the message

+	printk(KERN_NOTICE "Notice: NX (Execute Disable) protection "
+	       "missing in CPU or disabled in BIOS!\n");

which seems obviously wrong... no?

	-hpa

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.

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