lkml.org 
[lkml]   [2018]   [Feb]   [7]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 2/6] s390: add optimized array_index_mask_nospec
Date
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 <schwidefsky@de.ibm.com>
---
arch/s390/include/asm/barrier.h | 24 ++++++++++++++++++++++++
1 file changed, 24 insertions(+)

diff --git a/arch/s390/include/asm/barrier.h b/arch/s390/include/asm/barrier.h
index 1043260..f9eddbc 100644
--- a/arch/s390/include/asm/barrier.h
+++ b/arch/s390/include/asm/barrier.h
@@ -49,6 +49,30 @@ 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 */
--
2.7.4
\
 
 \ /
  Last update: 2018-02-07 08:02    [W:0.088 / U:3.260 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site