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x86: cpa, fix lookup_address

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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 <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Thomas Gleixner 2008-02-04 16:48:07 +01:00 committed by Ingo Molnar
parent 34508f66b6
commit 9a14aefc1d
1 changed files with 9 additions and 1 deletions
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10
arch/x86/mm/pageattr.c
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@ -188,6 +188,14 @@ static inline pgprot_t static_protections(pgprot_t prot, unsigned long address)
return prot; 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) pte_t *lookup_address(unsigned long address, int *level)
{ {
pgd_t *pgd = pgd_offset_k(address); pgd_t *pgd = pgd_offset_k(address);
@ -206,7 +214,7 @@ pte_t *lookup_address(unsigned long address, int *level)
return NULL; return NULL;
*level = PG_LEVEL_2M; *level = PG_LEVEL_2M;
if (pmd_large(*pmd)) if (pmd_large(*pmd) || !pmd_present(*pmd))
return (pte_t *)pmd; return (pte_t *)pmd;
*level = PG_LEVEL_4K; *level = PG_LEVEL_4K;