[PATCH 1/4] bitops: Fix shift overflow in GENMASK macros

[Sascha Hauer]

From: Steffen Trumtrar <s.trumtrar at pengutronix.de>

Based on the original patch for linux:

	commit 00b4d9a14125f1e51874def2b9de6092e007412d
	Author: Maxime COQUELIN <maxime.coquelin at st.com>
	Date:   Thu Nov 6 10:54:19 2014

	On some 32 bits architectures, including x86, GENMASK(31, 0) returns 0
	instead of the expected ~0UL.

	This is the same on some 64 bits architectures with GENMASK_ULL(63, 0).

	This is due to an overflow in the shift operand, 1 << 32 for GENMASK,
	1 << 64 for GENMASK_ULL.

Signed-off-by: Steffen Trumtrar <s.trumtrar at pengutronix.de>
---
 include/linux/bitops.h | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/include/linux/bitops.h b/include/linux/bitops.h
index f3a740c..31345c2 100644
--- a/include/linux/bitops.h
+++ b/include/linux/bitops.h
@@ -18,8 +18,11 @@
  * position @h. For example
  * GENMASK_ULL(39, 21) gives us the 64bit vector 0x000000ffffe00000.
  */
-#define GENMASK(h, l)		(((U32_C(1) << ((h) - (l) + 1)) - 1) << (l))
-#define GENMASK_ULL(h, l)	(((U64_C(1) << ((h) - (l) + 1)) - 1) << (l))
+#define GENMASK(h, l) \
+	(((~0UL) << (l)) & (~0UL >> (BITS_PER_LONG - 1 - (h))))
+
+#define GENMASK_ULL(h, l) \
+	(((~0ULL) << (l)) & (~0ULL >> (BITS_PER_LONG_LONG - 1 - (h))))
 
 extern unsigned int __sw_hweight8(unsigned int w);
 extern unsigned int __sw_hweight16(unsigned int w);
-- 
2.7.0.rc3