From mboxrd@z Thu Jan 1 00:00:00 1970 From: steve.capper@arm.com (Steve Capper) Date: Fri, 8 Feb 2013 15:01:18 +0000 Subject: [PATCH 1/6] ARM: mm: correct pte_same behaviour for LPAE. In-Reply-To: <1360335683-7755-1-git-send-email-steve.capper@arm.com> References: <1360335683-7755-1-git-send-email-steve.capper@arm.com> Message-ID: <1360335683-7755-2-git-send-email-steve.capper@arm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org 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: Will Deacon Signed-off-by: Steve Capper --- arch/arm/include/asm/pgtable-3level.h | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) diff --git a/arch/arm/include/asm/pgtable-3level.h b/arch/arm/include/asm/pgtable-3level.h index a3f3792..2b73b0f 100644 --- a/arch/arm/include/asm/pgtable-3level.h +++ b/arch/arm/include/asm/pgtable-3level.h @@ -148,6 +148,23 @@ 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__ */ -- 1.7.9.5