[PATCH] bitops.h: correctly handle rol32 with 0 byte shift

From	Sasha Levin <sasha.levin@oracle.com>
Newsgroups	linux.kernel
Subject	[PATCH] bitops.h: correctly handle rol32 with 0 byte shift
Date	2015-12-03 23:10 +0100
Message-ID	<qBKeB-2ve-1@gated-at.bofh.it> (permalink)
Organization	linux.* mail to news gateway

Show all headers | View raw

rol on a 32 bit integer with a shift of 32 or more is undefined and the
result is arch-dependent. Avoid this by handling the trivial case of
roling by 0 correctly.

Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
---
 include/linux/bitops.h |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/bitops.h b/include/linux/bitops.h
index 2b8ed12..7047a06 100644
--- a/include/linux/bitops.h
+++ b/include/linux/bitops.h
@@ -107,7 +107,7 @@ static inline __u64 ror64(__u64 word, unsigned int shift)
  */
 static inline __u32 rol32(__u32 word, unsigned int shift)
 {
-	return (word << shift) | (word >> (32 - shift));
+	return shift ? (word << shift) | (word >> (32 - shift)) : word;
 }
 
 /**
-- 
1.7.10.4

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

Back to linux.kernel | Previous | Next | Find similar | Unroll thread

Thread

[PATCH] bitops.h: correctly handle rol32 with 0 byte shift Sasha Levin <sasha.levin@oracle.com> - 2015-12-03 23:10 +0100

csiph-web