powerpc: Add "memory" attribute for mfmsr()

commit b416c9a10baae6a177b4f9ee858b8d309542fbef upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.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 c5cae0dd176..764e99c750d 100644
--- a/arch/powerpc/include/asm/reg.h
+++ b/arch/powerpc/include/asm/reg.h
@@ -1000,7 +1000,8 @@
 /* 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")