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authorEric Paris <eparis@redhat.com>2010-10-15 14:34:14 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2010-10-15 14:42:24 -0700
commit79b5dc0c64d88cda3da23b2e22a5cec0964372ac (patch)
treedffaf45200c456b87c4939ce422aea8efff1cfc8 /include
parente3c6cf61815b0af0c697aeed4c6f11762f913002 (diff)
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types.h: define __aligned_u64 and expose to userspace
We currently have a kernel internal type called aligned_u64 which aligns __u64's on 8 bytes boundaries even on systems which would normally align them on 4 byte boundaries. This patch creates a new type __aligned_u64 which does the same thing but which is exposed to userspace rather than being kernel internal. [akpm: merge early as both the net and audit trees want this] [akpm@linux-foundation.org: enhance the comment describing the reasons for using aligned_u64. Via Andreas and Andi.] Based-on-patch-by: Andreas Gruenbacher <agruen@suse.de> Signed-off-by: Eric Paris <eparis@redhat.com> Cc: Jan Engelhardt <jengelh@medozas.de> Cc: David Miller <davem@davemloft.net> Cc: Andi Kleen <andi@firstfloor.org> Cc: Arnd Bergmann <arnd@arndb.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include')
-rw-r--r--include/linux/types.h15
1 files changed, 14 insertions, 1 deletions
diff --git a/include/linux/types.h b/include/linux/types.h
index 01a082f56ef..357dbc19606 100644
--- a/include/linux/types.h
+++ b/include/linux/types.h
@@ -121,7 +121,15 @@ typedef __u64 u_int64_t;
typedef __s64 int64_t;
#endif
-/* this is a special 64bit data type that is 8-byte aligned */
+/*
+ * aligned_u64 should be used in defining kernel<->userspace ABIs to avoid
+ * common 32/64-bit compat problems.
+ * 64-bit values align to 4-byte boundaries on x86_32 (and possibly other
+ * architectures) and to 8-byte boundaries on 64-bit architetures. The new
+ * aligned_64 type enforces 8-byte alignment so that structs containing
+ * aligned_64 values have the same alignment on 32-bit and 64-bit architectures.
+ * No conversions are necessary between 32-bit user-space and a 64-bit kernel.
+ */
#define aligned_u64 __u64 __attribute__((aligned(8)))
#define aligned_be64 __be64 __attribute__((aligned(8)))
#define aligned_le64 __le64 __attribute__((aligned(8)))
@@ -178,6 +186,11 @@ typedef __u64 __bitwise __be64;
typedef __u16 __bitwise __sum16;
typedef __u32 __bitwise __wsum;
+/* this is a special 64bit data type that is 8-byte aligned */
+#define __aligned_u64 __u64 __attribute__((aligned(8)))
+#define __aligned_be64 __be64 __attribute__((aligned(8)))
+#define __aligned_le64 __le64 __attribute__((aligned(8)))
+
#ifdef __KERNEL__
typedef unsigned __bitwise__ gfp_t;
typedef unsigned __bitwise__ fmode_t;