[Xen-devel] [for-4.7 1/2] xen/bitops: Introduce macros to generate mask

[Julien Grall <julien.grall@xxxxxxx>]

The code has been imported from the header include/linux/bitops.h in
Linux v4.6-rc3.

Signed-off-by: Julien Grall <julien.grall@xxxxxxx>

---
Cc: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
Cc: Jan Beulich <jbeulich@xxxxxxxx>
Cc: Keir Fraser <keir@xxxxxxx>
Cc: Tim Deegan <tim@xxxxxxx>
---
 xen/include/xen/bitops.h | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/xen/include/xen/bitops.h b/xen/include/xen/bitops.h
index cb56f24..e1a4d93 100644
--- a/xen/include/xen/bitops.h
+++ b/xen/include/xen/bitops.h
@@ -3,6 +3,17 @@
 #include <asm/types.h>
 
 /*
+ * Create a contiguous bitmask starting at bit position @l and ending at
+ * position @h. For example
+ * GENMASK_ULL(39, 21) gives us the 64bit vector 0x000000ffffe00000.
+ */
+#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))))
+
+/*
  * ffs: find first bit set. This is defined the same way as
  * the libc and compiler builtin ffs routines, therefore
  * differs in spirit from the above ffz (man ffs).
-- 
1.9.1


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