From 79b5dc0c64d88cda3da23b2e22a5cec0964372ac Mon Sep 17 00:00:00 2001 From: Eric Paris Date: Fri, 15 Oct 2010 14:34:14 -0700 Subject: 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 Signed-off-by: Eric Paris Cc: Jan Engelhardt Cc: David Miller Cc: Andi Kleen Cc: Arnd Bergmann Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/types.h | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-) (limited to 'include/linux/types.h') diff --git a/include/linux/types.h b/include/linux/types.h index 01a082f..357dbc1 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; -- cgit v1.1