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SubjectRe: [BUGFIX] x86_64: NX bit handling in change_page_attr
On Fri, 17 Aug 2007 13:28:38 +0800 "Huang, Ying" <ying.huang@intel.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@intel.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;
> }

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