From: Huang, Ying Date: Wed, 30 Jan 2008 12:34:04 +0000 (+0100) Subject: x86: fix NX bit handling in change_page_attr() X-Git-Tag: v2.6.25-rc1~1143^2~74 X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=4c881ca1819da180b047f87eedeb9a5957918705;p=linux-2.6 x86: fix NX bit handling in change_page_attr() This patch fixes a bug of change_page_attr/change_page_attr_addr on Intel i386/x86_64 CPUs. After changing page attribute to be executable with these functions, the page remains un-executable on Intel i386/x86_64 CPU. Because on Intel i386/x86_64 CPU, only if the "NX" bits of all three level page tables are cleared (PAE is enabled), 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 Signed-off-by: Ingo Molnar Signed-off-by: Thomas Gleixner --- diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c index d18c41d752..cbe8e9223b 100644 --- a/arch/x86/mm/pageattr.c +++ b/arch/x86/mm/pageattr.c @@ -130,8 +130,13 @@ static int split_large_page(pte_t *kpte, unsigned long address) set_pte(&pbase[i], pfn_pte(addr >> PAGE_SHIFT, ref_prot)); /* - * Install the new, split up pagetable: + * Install the new, split up pagetable. Important detail here: + * + * On Intel the NX bit of all levels must be cleared to make a + * page executable. See section 4.13.2 of Intel 64 and IA-32 + * Architectures Software Developer's Manual). */ + ref_prot = pte_pgprot(pte_mkexec(pte_clrhuge(*kpte))); __set_pmd_pte(kpte, address, mk_pte(base, ref_prot)); base = NULL;