[PARISC] Purge existing TLB entries in set_pte_at and ptep_set_wrprotect

This patch goes a long way toward fixing the minifail bug, and
it  significantly improves the stability of SMP machines such as
the rp3440.  When write  protecting a page for COW, we need to
purge the existing translation.  Otherwise, the COW break
doesn't occur as expected because the TLB may still have a stale entry
which allows writes.

[jejb: fix up checkpatch errors]
Signed-off-by: John David Anglin <dave.anglin@bell.net>
Cc: stable@vger.kernel.org
Signed-off-by: James Bottomley <JBottomley@Parallels.com>

2 files changed, 28 insertions, 3 deletions

diff --git a/arch/parisc/include/asm/pgtable.h b/arch/parisc/include/asm/pgtable.h
index ee99f2339356..7df49fad29f9 100644
--- a/arch/parisc/include/asm/pgtable.h
+++ b/arch/parisc/include/asm/pgtable.h
@@ -12,11 +12,10 @@
 
 #include <linux/bitops.h>
 #include <linux/spinlock.h>
+#include <linux/mm_types.h>
 #include <asm/processor.h>
 #include <asm/cache.h>
 
-struct vm_area_struct;
-
 /*
  * kern_addr_valid(ADDR) tests if ADDR is pointing to valid kernel
  * memory.  For the return value to be meaningful, ADDR must be >=
@@ -40,7 +39,14 @@ struct vm_area_struct;
         do{                                                     \
                 *(pteptr) = (pteval);                           \
         } while(0)
-#define set_pte_at(mm,addr,ptep,pteval) set_pte(ptep,pteval)
+
+extern void purge_tlb_entries(struct mm_struct *, unsigned long);
+
+#define set_pte_at(mm, addr, ptep, pteval)                      \
+        do {                                                    \
+                set_pte(ptep, pteval);                          \
+                purge_tlb_entries(mm, addr);                    \
+        } while (0)
 
 #endif /* !__ASSEMBLY__ */
 
@@ -466,6 +472,7 @@ static inline void ptep_set_wrprotect(struct mm_struct *mm, unsigned long addr,
                 old = pte_val(*ptep);
                 new = pte_val(pte_wrprotect(__pte (old)));
         } while (cmpxchg((unsigned long *) ptep, old, new) != old);
+        purge_tlb_entries(mm, addr);
 #else
         pte_t old_pte = *ptep;
         set_pte_at(mm, addr, ptep, pte_wrprotect(old_pte));
diff --git a/arch/parisc/kernel/cache.c b/arch/parisc/kernel/cache.c
index 48e16dc20102..b89a85ab945e 100644
--- a/arch/parisc/kernel/cache.c
+++ b/arch/parisc/kernel/cache.c
@@ -419,6 +419,24 @@ void kunmap_parisc(void *addr)
 EXPORT_SYMBOL(kunmap_parisc);
 #endif
 
+void purge_tlb_entries(struct mm_struct *mm, unsigned long addr)
+{
+        unsigned long flags;
+
+        /* Note: purge_tlb_entries can be called at startup with
+           no context.  */
+
+        /* Disable preemption while we play with %sr1.  */
+        preempt_disable();
+        mtsp(mm->context, 1);
+        purge_tlb_start(flags);
+        pdtlb(addr);
+        pitlb(addr);
+        purge_tlb_end(flags);
+        preempt_enable();
+}
+EXPORT_SYMBOL(purge_tlb_entries);
+
 void __flush_tlb_range(unsigned long sid, unsigned long start,
                        unsigned long end)
 {