ppc64: add paranoid warnings for unexpected DSISR_PROTFAULT

ppc64 should not be depending on DSISR_PROTFAULT and it's unexpected if
they are triggered.  This patch adds warnings just in case they are being
accidentally depended upon.

Signed-off-by: Mel Gorman <mgorman@suse.de>
Acked-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Tested-by: Sasha Levin <sasha.levin@oracle.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Dave Jones <davej@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Kirill Shutemov <kirill.shutemov@linux.intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 15 insertions, 13 deletions

diff --git a/arch/powerpc/mm/copro_fault.c b/arch/powerpc/mm/copro_fault.c
index 1b5305d4bdab..f031a47d7701 100644
--- a/arch/powerpc/mm/copro_fault.c
+++ b/arch/powerpc/mm/copro_fault.c
@@ -64,10 +64,14 @@ int copro_handle_mm_fault(struct mm_struct *mm, unsigned long ea,
                 if (!(vma->vm_flags & VM_WRITE))
                         goto out_unlock;
         } else {
-                if (dsisr & DSISR_PROTFAULT)
-                        goto out_unlock;
                 if (!(vma->vm_flags & (VM_READ | VM_EXEC)))
                         goto out_unlock;
+                /*
+                 * protfault should only happen due to us
+                 * mapping a region readonly temporarily. PROT_NONE
+                 * is also covered by the VMA check above.
+                 */
+                WARN_ON_ONCE(dsisr & DSISR_PROTFAULT);
         }
 
         ret = 0;
diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c
index f38327b95f76..b396868d2aa7 100644
--- a/arch/powerpc/mm/fault.c
+++ b/arch/powerpc/mm/fault.c
@@ -389,17 +389,6 @@ good_area:
 #endif /* CONFIG_8xx */
 
         if (is_exec) {
-#ifdef CONFIG_PPC_STD_MMU
-                /* Protection fault on exec go straight to failure on
-                 * Hash based MMUs as they either don't support per-page
-                 * execute permission, or if they do, it's handled already
-                 * at the hash level. This test would probably have to
-                 * be removed if we change the way this works to make hash
-                 * processors use the same I/D cache coherency mechanism
-                 * as embedded.
-                 */
-#endif /* CONFIG_PPC_STD_MMU */
-
                 /*
                  * Allow execution from readable areas if the MMU does not
                  * provide separate controls over reading and executing.
@@ -414,6 +403,14 @@ good_area:
                     (cpu_has_feature(CPU_FTR_NOEXECUTE) ||
                      !(vma->vm_flags & (VM_READ | VM_WRITE))))
                         goto bad_area;
+#ifdef CONFIG_PPC_STD_MMU
+                /*
+                 * protfault should only happen due to us
+                 * mapping a region readonly temporarily. PROT_NONE
+                 * is also covered by the VMA check above.
+                 */
+                WARN_ON_ONCE(error_code & DSISR_PROTFAULT);
+#endif /* CONFIG_PPC_STD_MMU */
         /* a write */
         } else if (is_write) {
                 if (!(vma->vm_flags & VM_WRITE))
@@ -423,6 +420,7 @@ good_area:
         } else {
                 if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))
                         goto bad_area;
+                WARN_ON_ONCE(error_code & DSISR_PROTFAULT);
         }
 
         /*