From 9a14aefc1d28c6037122965ee8c10d92a970ade0 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Mon, 4 Feb 2008 16:48:07 +0100 Subject: [PATCH] x86: cpa, fix lookup_address lookup_address() returns a wrong level and a wrong pointer to a non existing pte, when pmd or pud entries are marked !present. This happens for example due to boot time mapping of GART into the low memory space. Signed-off-by: Thomas Gleixner Signed-off-by: Ingo Molnar --- arch/x86/mm/pageattr.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c index 3810f7a83b1d..7d21cd658ed3 100644 --- a/arch/x86/mm/pageattr.c +++ b/arch/x86/mm/pageattr.c @@ -188,6 +188,14 @@ static inline pgprot_t static_protections(pgprot_t prot, unsigned long address) return prot; } +/* + * Lookup the page table entry for a virtual address. Return a pointer + * to the entry and the level of the mapping. + * + * Note: We return pud and pmd either when the entry is marked large + * or when the present bit is not set. Otherwise we would return a + * pointer to a nonexisting mapping. + */ pte_t *lookup_address(unsigned long address, int *level) { pgd_t *pgd = pgd_offset_k(address); @@ -206,7 +214,7 @@ pte_t *lookup_address(unsigned long address, int *level) return NULL; *level = PG_LEVEL_2M; - if (pmd_large(*pmd)) + if (pmd_large(*pmd) || !pmd_present(*pmd)) return (pte_t *)pmd; *level = PG_LEVEL_4K; -- 2.20.1