[PATCH 3.18 22/60] powerpc/asm: Mark cr0 as clobbered in mftb()

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From	Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Subject	[PATCH 3.18 22/60] powerpc/asm: Mark cr0 as clobbered in mftb()
Date	Tue, 25 Jul 2017 23:40:02 +0200
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3.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Oliver O'Halloran <oohall@gmail.com>

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>

---
 arch/powerpc/include/asm/reg.h |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/powerpc/include/asm/reg.h
+++ b/arch/powerpc/include/asm/reg.h
@@ -1231,7 +1231,7 @@ static inline unsigned long mfvtb (void)
 				"	.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;	\

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[PATCH 3.18 22/60] powerpc/asm: Mark cr0 as clobbered in mftb() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-25 23:40 +0200

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