1 files changed, 40 insertions, 13 deletions

diff --git a/arch/powerpc/mm/hash_utils_64.c b/arch/powerpc/mm/hash_utils_64.c
index 98f262de5585..09dffe6efa46 100644
--- a/arch/powerpc/mm/hash_utils_64.c
+++ b/arch/powerpc/mm/hash_utils_64.c
@@ -871,6 +871,18 @@ static inline int subpage_protection(struct mm_struct *mm, unsigned long ea)
 }
 #endif
 
+void hash_failure_debug(unsigned long ea, unsigned long access,
+                        unsigned long vsid, unsigned long trap,
+                        int ssize, int psize, unsigned long pte)
+{
+        if (!printk_ratelimit())
+                return;
+        pr_info("mm: Hashing failure ! EA=0x%lx access=0x%lx current=%s\n",
+                ea, access, current->comm);
+        pr_info("    trap=0x%lx vsid=0x%lx ssize=%d psize=%d pte=0x%lx\n",
+                trap, vsid, ssize, psize, pte);
+}
+
 /* Result code is:
  *  0 - handled
  *  1 - normal page fault
@@ -955,6 +967,17 @@ int hash_page(unsigned long ea, unsigned long access, unsigned long trap)
                 return 1;
         }
 
+        /* Add _PAGE_PRESENT to the required access perm */
+        access |= _PAGE_PRESENT;
+
+        /* Pre-check access permissions (will be re-checked atomically
+         * in __hash_page_XX but this pre-check is a fast path
+         */
+        if (access & ~pte_val(*ptep)) {
+                DBG_LOW(" no access !\n");
+                return 1;
+        }
+
 #ifdef CONFIG_HUGETLB_PAGE
         if (hugeshift)
                 return __hash_page_huge(ea, access, vsid, ptep, trap, local,
@@ -967,14 +990,6 @@ int hash_page(unsigned long ea, unsigned long access, unsigned long trap)
         DBG_LOW(" i-pte: %016lx %016lx\n", pte_val(*ptep),
                 pte_val(*(ptep + PTRS_PER_PTE)));
 #endif
-        /* Pre-check access permissions (will be re-checked atomically
-         * in __hash_page_XX but this pre-check is a fast path
-         */
-        if (access & ~pte_val(*ptep)) {
-                DBG_LOW(" no access !\n");
-                return 1;
-        }
-
         /* Do actual hashing */
 #ifdef CONFIG_PPC_64K_PAGES
         /* If _PAGE_4K_PFN is set, make sure this is a 4k segment */
@@ -1033,6 +1048,12 @@ int hash_page(unsigned long ea, unsigned long access, unsigned long trap)
                                             local, ssize, spp);
         }
 
+        /* Dump some info in case of hash insertion failure, they should
+         * never happen so it is really useful to know if/when they do
+         */
+        if (rc == -1)
+                hash_failure_debug(ea, access, vsid, trap, ssize, psize,
+                                   pte_val(*ptep));
 #ifndef CONFIG_PPC_64K_PAGES
         DBG_LOW(" o-pte: %016lx\n", pte_val(*ptep));
 #else
@@ -1051,8 +1072,7 @@ void hash_preload(struct mm_struct *mm, unsigned long ea,
         void *pgdir;
         pte_t *ptep;
         unsigned long flags;
-        int local = 0;
-        int ssize;
+        int rc, ssize, local = 0;
 
         BUG_ON(REGION_ID(ea) != USER_REGION_ID);
 
@@ -1098,11 +1118,18 @@ void hash_preload(struct mm_struct *mm, unsigned long ea,
         /* Hash it in */
 #ifdef CONFIG_PPC_HAS_HASH_64K
         if (mm->context.user_psize == MMU_PAGE_64K)
-                __hash_page_64K(ea, access, vsid, ptep, trap, local, ssize);
+                rc = __hash_page_64K(ea, access, vsid, ptep, trap, local, ssize);
         else
 #endif /* CONFIG_PPC_HAS_HASH_64K */
-                __hash_page_4K(ea, access, vsid, ptep, trap, local, ssize,
-                               subpage_protection(pgdir, ea));
+                rc = __hash_page_4K(ea, access, vsid, ptep, trap, local, ssize,
+                                    subpage_protection(pgdir, ea));
+
+        /* Dump some info in case of hash insertion failure, they should
+         * never happen so it is really useful to know if/when they do
+         */
+        if (rc == -1)
+                hash_failure_debug(ea, access, vsid, trap, ssize,
+                                   mm->context.user_psize, pte_val(*ptep));
 
         local_irq_restore(flags);
 }