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authorDavid Daney <david.daney@cavium.com>2012-12-04 00:44:26 +0400
committerRalf Baechle <ralf@linux-mips.org>2012-12-04 19:57:54 +0400
commitac53c4fca42c394d8a06c7a470ae2d1d50503717 (patch)
tree4f40ff8ce55356ec23f0bf0c1306d3d2f58d0f59 /arch/mips/include/asm/hugetlb.h
parent9489e9dcae718d5fde988e4a684a0f55b5f94d17 (diff)
downloadlinux-ac53c4fca42c394d8a06c7a470ae2d1d50503717.tar.xz
MIPS: Avoid mcheck by flushing page range in huge_ptep_set_access_flags()
Problem: 1) Huge page mapping of anonymous memory is initially invalid. Will be faulted in by copy-on-write mechanism. 2) Userspace attempts store at the end of the huge mapping. 3) TLB Refill exception handler fill TLB with a normal (4K sized) invalid page at the end of the huge mapping virtual address range. 4) Userspace restarted, and re-attempts the store at the end of the huge mapping. 5) Page from #3 is invalid, we get a fault and go to the hugepage fault handler. This tries to map a huge page and calls huge_ptep_set_access_flags() to install the mapping. 6) We just call the generic ptep_set_access_flags() to set up the page tables, but the flush there assumes a normal (4K sized) page and only tries to flush the first part of the huge page virtual address out of the TLB, since the existing entry from step #3 doesn't conflict, nothing is flushed. 7) We attempt to load the mapping into the TLB, but because it conflicts with the entry from step #3, we get a Machine Check exception. The fix: Flush the entire rage covered by the huge page in huge_ptep_set_access_flags(), and remove the optimization in local_flush_tlb_range() so that the flush actually does the correct thing. Signed-off-by: David Daney <david.daney@cavium.com> Cc: linux-mips@linux-mips.org Cc: linux-kernel@vger.kernel.org Cc: Hillf Danton <dhillf@gmail.com> Patchwork: https://patchwork.linux-mips.org/patch/4661/ Signed-off-by: Ralf Baechle <ralf@linux-mips.org> (cherry picked from commit dd617f258cc39d36be26afee9912624a2d23112c)
Diffstat (limited to 'arch/mips/include/asm/hugetlb.h')
-rw-r--r--arch/mips/include/asm/hugetlb.h12
1 files changed, 11 insertions, 1 deletions
diff --git a/arch/mips/include/asm/hugetlb.h b/arch/mips/include/asm/hugetlb.h
index bd94946a18f3..ef99db994c2f 100644
--- a/arch/mips/include/asm/hugetlb.h
+++ b/arch/mips/include/asm/hugetlb.h
@@ -95,7 +95,17 @@ static inline int huge_ptep_set_access_flags(struct vm_area_struct *vma,
pte_t *ptep, pte_t pte,
int dirty)
{
- return ptep_set_access_flags(vma, addr, ptep, pte, dirty);
+ int changed = !pte_same(*ptep, pte);
+
+ if (changed) {
+ set_pte_at(vma->vm_mm, addr, ptep, pte);
+ /*
+ * There could be some standard sized pages in there,
+ * get them all.
+ */
+ flush_tlb_range(vma, addr, addr + HPAGE_SIZE);
+ }
+ return changed;
}
static inline pte_t huge_ptep_get(pte_t *ptep)