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authorDavid Daney <david.daney@cavium.com>2012-12-03 12:44:26 -0800
committerRalf Baechle <ralf@linux-mips.org>2012-12-04 16:57:54 +0100
commitac53c4fca42c394d8a06c7a470ae2d1d50503717 (patch)
tree4f40ff8ce55356ec23f0bf0c1306d3d2f58d0f59 /arch/mips/mm
parent9489e9dcae718d5fde988e4a684a0f55b5f94d17 (diff)
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/mm')
-rw-r--r--arch/mips/mm/tlb-r4k.c18
1 files changed, 4 insertions, 14 deletions
diff --git a/arch/mips/mm/tlb-r4k.c b/arch/mips/mm/tlb-r4k.c
index 4b9b935a070..88e79ad6f81 100644
--- a/arch/mips/mm/tlb-r4k.c
+++ b/arch/mips/mm/tlb-r4k.c
@@ -120,18 +120,11 @@ void local_flush_tlb_range(struct vm_area_struct *vma, unsigned long start,
if (cpu_context(cpu, mm) != 0) {
unsigned long size, flags;
- int huge = is_vm_hugetlb_page(vma);
ENTER_CRITICAL(flags);
- if (huge) {
- start = round_down(start, HPAGE_SIZE);
- end = round_up(end, HPAGE_SIZE);
- size = (end - start) >> HPAGE_SHIFT;
- } else {
- start = round_down(start, PAGE_SIZE << 1);
- end = round_up(end, PAGE_SIZE << 1);
- size = (end - start) >> (PAGE_SHIFT + 1);
- }
+ start = round_down(start, PAGE_SIZE << 1);
+ end = round_up(end, PAGE_SIZE << 1);
+ size = (end - start) >> (PAGE_SHIFT + 1);
if (size <= current_cpu_data.tlbsize/2) {
int oldpid = read_c0_entryhi();
int newpid = cpu_asid(cpu, mm);
@@ -140,10 +133,7 @@ void local_flush_tlb_range(struct vm_area_struct *vma, unsigned long start,
int idx;
write_c0_entryhi(start | newpid);
- if (huge)
- start += HPAGE_SIZE;
- else
- start += (PAGE_SIZE << 1);
+ start += (PAGE_SIZE << 1);
mtc0_tlbw_hazard();
tlb_probe();
tlb_probe_hazard();