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Date:	Tue, 10 Nov 2009 08:47:23 -0800
From:	"H. Peter Anvin" <>
To:	Kees Cook <>
CC:	Arjan van de Ven <>,
	Thomas Gleixner <>,
	Ingo Molnar <>,,
	Pekka Enberg <>,
	Jan Beulich <>,
	Vegard Nossum <>,
	Yinghai Lu <>,
	Jeremy Fitzhardinge <>,
Subject: Re: [PATCH v4] [x86] detect and report lack of NX protections

On 11/10/2009 07:49 AM, Kees Cook wrote:
>> The second clause can only get executed if CONFIG_X86_PAE is unset,
>> which in turn means _PAGE_NX == 0... so that piece of code is meaningless.
> CONFIG_X86_PAE is unset for x86_64, where _PAGE_NX is valid.  (This was
> the main situation I was trying to address.)  So that chunk runs for
> non-pae 32bit, and all 64bit:

In reality, X86_PAE really should have been defined for 64 bits, since
64 bits really is PAE in most aspects.

Anyway, for the 64-bit case it looks like the proper place for any of
this is in check_efer() just below, not in this null routine.


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

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