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authorSteve Capper <steve.capper@linaro.org>2013-11-19 15:22:39 +0000
committerSteve Capper <steve.capper@linaro.org>2013-12-10 08:22:45 +0000
commit97c7796e80231ae933fa7a2f7de472165c70e989 (patch)
tree3a50bc762806a39a280e4f472a111e710e13f29e
parent5e01dc7b26d9f24f39abace5da98ccbd6a5ceb52 (diff)
downloadlinux-97c7796e80231ae933fa7a2f7de472165c70e989.tar.gz
ARM: mm: Rewire LPAE set_huge_pte_at
For LPAE, set_huge_pte_at calls set_pte_at which then calls set_pte_ext, which in turn is wired up to call cpu_v7_set_pte_ext, which is defined in proc-v7-3level.S. For huge pages, given newprot a pgprot_t value for a shared writable VMA, and ptep a pointer to a pte belonging to this VMA; the following behaviour is assumed by core code: hugetlb_change_protection(vma, address, end, newprot); ... huge_pte_write(huge_ptep_get(ptep)); /* should be true! */ Unfortunately, cpu_v7_set_pte_ext will change the bit layout of the resultant pte, and will set the read only bit if the dirty bit is not also enabled. If one were to allocate a read only shared huge page, then fault it in, and then mprotect it to be writeable. A subsequent write to that huge page will result in a spurious call to hugetlb_cow. This call is optimised away prior to: 37a2140 mm, hugetlb: do not use a page in page cache for cow optimization If one runs the libhugetlbfs test suite on v3.12-rc1 upwards, then the mprotect test will cause the afformentioned corruption and before the set of tests completes, the system will be left in an unresponsive state. (calls to fork fail with -ENOMEM). This patch re-implements set_huge_pte_at to dereference the pte value explicitly. hugetlb_cow is no longer called spuriously, and the unit tests complete succesfully. Signed-off-by: Steve Capper <steve.capper@linaro.org>
-rw-r--r--arch/arm/include/asm/hugetlb-3level.h7
1 files changed, 6 insertions, 1 deletions
diff --git a/arch/arm/include/asm/hugetlb-3level.h b/arch/arm/include/asm/hugetlb-3level.h
index d4014fbe5ea..211e9a89db4 100644
--- a/arch/arm/include/asm/hugetlb-3level.h
+++ b/arch/arm/include/asm/hugetlb-3level.h
@@ -40,7 +40,12 @@ static inline pte_t huge_ptep_get(pte_t *ptep)
static inline void set_huge_pte_at(struct mm_struct *mm, unsigned long addr,
pte_t *ptep, pte_t pte)
{
- set_pte_at(mm, addr, ptep, pte);
+ VM_BUG_ON(addr >= TASK_SIZE);
+
+ if (pte_present_user(pte))
+ __sync_icache_dcache(pte);
+
+ *ptep = pte;
}
static inline void huge_ptep_clear_flush(struct vm_area_struct *vma,