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

1 files changed, 2 insertions, 1 deletions

diff --git a/arch/powerpc/include/asm/reg.h b/arch/powerpc/include/asm/reg.h
index 2baeb7c8764f..638608677e2a 100644
--- 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")