linux-kernel - Re: [BUGFIX] x86_64: NX bit handling in change_page

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Date:	Tue, 11 Sep 2007 20:23:32 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	"Huang, Ying" <ying.huang@...el.com>
Cc:	Andi Kleen <ak@...e.de>, linux-kernel@...r.kernel.org
Subject: Re: [BUGFIX] x86_64: NX bit handling in change_page_attr

On Fri, 17 Aug 2007 13:28:38 +0800 "Huang, Ying" <ying.huang@...el.com> wrote:

> This patch fixes a bug of change_page_attr/change_page_attr_addr on
> Intel x86_64 CPU. After changing page attribute to be executable with
> these functions, the page remains un-executable on Intel x86_64
> CPU. Because on Intel x86_64 CPU, only if the "NX" bits of all four
> level page tables are cleared, the corresponding page is executable
> (refer to section 4.13.2 of Intel 64 and IA-32 Architectures Software
> Developer's Manual). So, the bug is fixed through clearing the "NX"
> bit of PMD when splitting the huge PMD.
> 
> Signed-off-by: Huang Ying <ying.huang@...el.com>
> 
> ---
> 
> Index: linux-2.6.23-rc2-mm2/arch/x86_64/mm/pageattr.c
> ===================================================================
> --- linux-2.6.23-rc2-mm2.orig/arch/x86_64/mm/pageattr.c	2007-08-17 12:50:25.000000000 +0800
> +++ linux-2.6.23-rc2-mm2/arch/x86_64/mm/pageattr.c	2007-08-17 12:50:48.000000000 +0800
> @@ -147,6 +147,7 @@
>  			split = split_large_page(address, prot, ref_prot2);
>  			if (!split)
>  				return -ENOMEM;
> +			pgprot_val(ref_prot2) &= ~_PAGE_NX;
>  			set_pte(kpte, mk_pte(split, ref_prot2));
>  			kpte_page = split;
>  		}

What happened with this?  Still valid?
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