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Commit dde1b651 authored by Steve Capper's avatar Steve Capper
Browse files

ARM: mm: correct pte_same behaviour for LPAE. 



For 3 levels of paging the PTE_EXT_NG bit will be set for user
address ptes that are written to a page table but not for ptes
created with mk_pte.

This can cause some comparison tests made by pte_same to fail
spuriously and lead to other problems.

To correct this behaviour, we mask off PTE_EXT_NG for any pte that
is present before running the comparison.

Signed-off-by: default avatarSteve Capper <steve.capper@linaro.org>
Reviewed-by: default avatarWill Deacon <will.deacon@arm.com>
parent e4aa937e

arch/arm/include/asm/pgtable-3level.h

+17 −0
Original line number Diff line number Diff line
@@ -166,6 +166,23 @@ static inline pmd_t *pmd_offset(pud_t *pud, unsigned long addr) 
		clean_pmd_entry(pmdp);	\

	} while (0)



/*

 * For 3 levels of paging the PTE_EXT_NG bit will be set for user address ptes

 * that are written to a page table but not for ptes created with mk_pte.

 *

 * In hugetlb_no_page, a new huge pte (new_pte) is generated and passed to

 * hugetlb_cow, where it is compared with an entry in a page table.

 * This comparison test fails erroneously leading ultimately to a memory leak.

 *

 * To correct this behaviour, we mask off PTE_EXT_NG for any pte that is

 * present before running the comparison.

 */

#define __HAVE_ARCH_PTE_SAME

#define pte_same(pte_a,pte_b)	((pte_present(pte_a) ? pte_val(pte_a) & ~PTE_EXT_NG	\

					: pte_val(pte_a))				\

				== (pte_present(pte_b) ? pte_val(pte_b) & ~PTE_EXT_NG	\

					: pte_val(pte_b)))



#define set_pte_ext(ptep,pte,ext) cpu_set_pte_ext(ptep,__pte(pte_val(pte)|(ext)))



#endif /* __ASSEMBLY__ */