Spotted by Hugh:

Stop mprotect's pte_modify from wiping out the powerpc pte_special bit, which
caused oops thereafter when vm_normal_page thought X's abnormal was normal.

Signed-off-by: Nick Piggin <npiggin@suse.de>
---
Index: linux-2.6/include/asm-powerpc/pgtable-4k.h
===================================================================
--- linux-2.6.orig/include/asm-powerpc/pgtable-4k.h
+++ linux-2.6/include/asm-powerpc/pgtable-4k.h
@@ -60,7 +60,7 @@
 /* It should be preserving the high 48 bits and then specifically */
 /* preserving _PAGE_SECONDARY | _PAGE_GROUP_IX */
 #define _PAGE_CHG_MASK	(PAGE_MASK | _PAGE_ACCESSED | _PAGE_DIRTY | \
-                         _PAGE_HPTEFLAGS)
+                         _PAGE_SPECIAL | _PAGE_HPTEFLAGS)
 
 /* Bits to mask out from a PMD to get to the PTE page */
 #define PMD_MASKED_BITS		0