[PATCH 3.10 034/139] powerpc/asm: Mark cr0 as clobbered in mftb()

[Willy Tarreau]

From: Oliver O'Halloran <oohall@xxxxxxxxx>

commit 2400fd822f467cb4c886c879d8ad99feac9cf319 upstream.

The workaround for the CELL timebase bug does not correctly mark cr0 as
being clobbered. This means GCC doesn't know that the asm block changes cr0 and
might leave the result of an unrelated comparison in cr0 across the block, which
we then trash, leading to basically random behaviour.

Fixes: 859deea949c3 ("[POWERPC] Cell timebase bug workaround")
Cc: stable@xxxxxxxxxxxxxxx 
Signed-off-by: Oliver O'Halloran <oohall@xxxxxxxxx>
[mpe: Tweak change log and flag for stable]
Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Signed-off-by: Willy Tarreau <w@xxxxxx>
---
 arch/powerpc/include/asm/reg.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/powerpc/include/asm/reg.h b/arch/powerpc/include/asm/reg.h
index 469d771..954168b 100644
--- a/arch/powerpc/include/asm/reg.h
+++ b/arch/powerpc/include/asm/reg.h
@@ -1136,7 +1136,7 @@
 				"	.llong 0\n"			\
 				"	.llong 0\n"			\
 				".previous"				\
-			: "=r" (rval) : "i" (CPU_FTR_CELL_TB_BUG)); rval;})
+			: "=r" (rval) : "i" (CPU_FTR_CELL_TB_BUG) : "cr0"); rval;})
 #else
 #define mftb()		({unsigned long rval;	\
 			asm volatile("mftb %0" : "=r" (rval)); rval;})
-- 
2.8.0.rc2.1.gbe9624a