From: Oliver O'Halloran <oohall@gmail.com>
Date: Thu, 6 Jul 2017 18:46:43 +1000
Subject: [PATCH] powerpc/asm: Mark cr0 as clobbered in mftb()
References: bnc#1060662
Patch-mainline: v4.12.4
Git-commit: 2400fd822f467cb4c886c879d8ad99feac9cf319

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")
Signed-off-by: Oliver O'Halloran <oohall@gmail.com>
[mpe: Tweak change log and flag for stable]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
 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 7e50e47375d6..a3b6575c7842 100644
--- a/arch/powerpc/include/asm/reg.h
+++ b/arch/powerpc/include/asm/reg.h
@@ -1303,7 +1303,7 @@ static inline void msr_check_and_clear(unsigned long bits)
 				"	.llong 0\n"			\
 				".previous"				\
 			: "=r" (rval) \
-			: "i" (CPU_FTR_CELL_TB_BUG), "i" (SPRN_TBRL)); \
+			: "i" (CPU_FTR_CELL_TB_BUG), "i" (SPRN_TBRL) : "cr0"); \
 			rval;})
 #else
 #define mftb()		({unsigned long rval;	\
-- 
2.14.2