powerpc: Add "memory" attribute for mfmsr()

Add "memory" attribute in inline assembly language as a compiler
barrier to make sure 4.6.x GCC don't reorder mfmsr().

Signed-off-by: Tiejun Chen <tiejun.chen@windriver.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
CC: stable@vger.kernel.org

diff --git a/arch/powerpc/include/asm/reg.h b/arch/powerpc/include/asm/reg.h
index 2baeb7c..6386086 100644 (file)
--- a/arch/powerpc/include/asm/reg.h
+++ b/arch/powerpc/include/asm/reg.h
@@ -1025,7 +1025,8 @@
 /* Macros for setting and retrieving special purpose registers */
 #ifndef __ASSEMBLY__
 #define mfmsr()                ({unsigned long rval; \
-                       asm volatile("mfmsr %0" : "=r" (rval)); rval;})
+                       asm volatile("mfmsr %0" : "=r" (rval) : \
+                                               : "memory"); rval;})
 #ifdef CONFIG_PPC_BOOK3S_64
 #define __mtmsrd(v, l) asm volatile("mtmsrd %0," __stringify(l) \
                                     : : "r" (v) : "memory")