linux-kernel - Re: 4.4-rc5: ugly warn on: 5 W+X pages found

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Date:	Tue, 15 Dec 2015 05:26:00 -0800
From:	Arjan van de Ven <arjan@...ux.intel.com>
To:	Pavel Machek <pavel@....cz>
Cc:	Andy Lutomirski <luto@...capital.net>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Borislav Petkov <bp@...en8.de>,
	kernel list <linux-kernel@...r.kernel.org>,
	Stephen Smalley <sds@...ho.nsa.gov>,
	Brian Gerst <brgerst@...il.com>,
	Denys Vlasenko <dvlasenk@...hat.com>,
	Peter Anvin <hpa@...or.com>, Mike Galbraith <efault@....de>,
	Peter Zijlstra <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: 4.4-rc5: ugly warn on: 5 W+X pages found

On 12/14/2015 11:56 PM, Pavel Machek wrote:
> On Mon 2015-12-14 13:24:08, Arjan van de Ven wrote:
>>
>>> That's weird.  The only API to do that seems to be manually setting
>>> kmap_prot to _PAGE_KERNEL_EXEC, and nothing does that.  (Why is
>>> kmap_prot a variable on x86 at all?  It has exactly one writer, and
>>> that's the code that initializes it in the first place.  Shouldn't we
>>> #define kmap_prot _PAGE_KERNEL?
>>
>> iirc it changes based on runtime detection of NX capability
>
> Huh. Is it possible that core duo is so old that it has no NX?

really stupid question I guess, but is PAE on ?
(64 bit pagetables are required for NX)


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