[PATCH 2/3] s390/xor: Improve inline assembly constraints

[Heiko Carstens]

The inline assembly constraint for the "bytes" operand is "d" for all xor()
inline assemblies. "d" means that any register from 0 to 15 can be used. If
the compiler would use register 0 then the exrl instruction would not or
the value of "bytes" into the executed instruction - resulting in an
incorrect result.

However all the xor() inline assemblies make hard-coded use of register 0,
and it is correctly listed in the clobber list, so that this cannot happen.

Given that this is quite subtle use the better "a" constraint, which
excludes register 0 from register allocation in any case.

Signed-off-by: Heiko Carstens <hca@xxxxxxxxxxxxx>
---
 arch/s390/lib/xor.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/s390/lib/xor.c b/arch/s390/lib/xor.c
index d703c44d5fd6..da134c7d89a6 100644
--- a/arch/s390/lib/xor.c
+++ b/arch/s390/lib/xor.c
@@ -28,7 +28,7 @@ static void xor_xc_2(unsigned long bytes, unsigned long * __restrict p1,
 		"	j	3f\n"
 		"2:	xc	0(1,%1),0(%2)\n"
 		"3:"
-		: "+d" (bytes), "+a" (p1), "+a" (p2)
+		: "+a" (bytes), "+a" (p1), "+a" (p2)
 		: : "0", "cc", "memory");
 }
 
@@ -54,7 +54,7 @@ static void xor_xc_3(unsigned long bytes, unsigned long * __restrict p1,
 		"2:	xc	0(1,%1),0(%2)\n"
 		"3:	xc	0(1,%1),0(%3)\n"
 		"4:"
-		: "+d" (bytes), "+a" (p1), "+a" (p2), "+a" (p3)
+		: "+a" (bytes), "+a" (p1), "+a" (p2), "+a" (p3)
 		: : "0", "cc", "memory");
 }
 
@@ -85,7 +85,7 @@ static void xor_xc_4(unsigned long bytes, unsigned long * __restrict p1,
 		"3:	xc	0(1,%1),0(%3)\n"
 		"4:	xc	0(1,%1),0(%4)\n"
 		"5:"
-		: "+d" (bytes), "+a" (p1), "+a" (p2), "+a" (p3), "+a" (p4)
+		: "+a" (bytes), "+a" (p1), "+a" (p2), "+a" (p3), "+a" (p4)
 		: : "0", "cc", "memory");
 }
 
@@ -122,7 +122,7 @@ static void xor_xc_5(unsigned long bytes, unsigned long * __restrict p1,
 		"4:	xc	0(1,%1),0(%4)\n"
 		"5:	xc	0(1,%1),0(%5)\n"
 		"6:"
-		: "+d" (bytes), "+a" (p1), "+a" (p2), "+a" (p3), "+a" (p4),
+		: "+a" (bytes), "+a" (p1), "+a" (p2), "+a" (p3), "+a" (p4),
 		  "+a" (p5)
 		: : "0", "cc", "memory");
 }
-- 
2.51.0