linux-kernel - Re: [PATCH v2] [x86] detect and report lack of NX protections

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Message-ID: <4ADD1E03.4070200@zytor.com>
Date:	Tue, 20 Oct 2009 11:18:43 +0900
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 v2] [x86] detect and report lack of NX protections

On 10/20/2009 11:04 AM, Kees Cook wrote:
> It is possible for x86_64 systems to lack the NX bit (see check_efer())
> either due to the hardware lacking support or the BIOS having turned
> off the CPU capability, so NX status should be reported.  Additionally,
> anyone booting NX-capable CPUs in 32bit mode without PAE will lack NX
> functionality, so this change provides feedback for that case as well.
>
> v2: use "Alert:" instead of "Warning:" to avoid confusiong with WARN_ON()
>

They're both wrong.  Both imply that the user needs to take an action, 
which is wrong because the kernel is working as intended.  If you need 
to use any kind of alert word, it should be something like "Notice:", 
and it should be KERN_NOTICE or even KERN_INFO.

	-hpa
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