4.9-stable review patch. If anyone has any objections, please let me know.
------------------
From: Martin Schwidefsky <schwidef...@de.ibm.com>
[ Upstream commit e2dd833389cc4069a96b57bdd24227b5f52288f5 ]
Add an optimized version of the array_index_mask_nospec function for
s390 based on a compare and a subtract with borrow.
Signed-off-by: Martin Schwidefsky <schwidef...@de.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
arch/s390/include/asm/barrier.h | 24 ++++++++++++++++++++++++
1 file changed, 24 insertions(+)
--- a/arch/s390/include/asm/barrier.h
+++ b/arch/s390/include/asm/barrier.h
@@ -48,6 +48,30 @@ do {
\
#define __smp_mb__before_atomic() barrier()
#define __smp_mb__after_atomic() barrier()
+/**
+ * array_index_mask_nospec - generate a mask for array_idx() that is
+ * ~0UL when the bounds check succeeds and 0 otherwise
+ * @index: array element index
+ * @size: number of elements in array
+ */
+#define array_index_mask_nospec array_index_mask_nospec
+static inline unsigned long array_index_mask_nospec(unsigned long index,
+ unsigned long size)
+{
+ unsigned long mask;
+
+ if (__builtin_constant_p(size) && size > 0) {
+ asm(" clgr %2,%1\n"
+ " slbgr %0,%0\n"
+ :"=d" (mask) : "d" (size-1), "d" (index) :"cc");
+ return mask;
+ }
+ asm(" clgr %1,%2\n"
+ " slbgr %0,%0\n"
+ :"=d" (mask) : "d" (size), "d" (index) :"cc");
+ return ~mask;
+}
+
#include <asm-generic/barrier.h>
#endif /* __ASM_BARRIER_H */
