Commit 4c881ca1 authored Jan 30, 2008 by Huang, Ying Committed by Ingo Molnar Jan 30, 2008

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 <ying.huang@intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

parent 8192206d

arch/x86/mm/pageattr.c

+6 −1

Original line number	Diff line number	Diff line
		@@ -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;

Admin message