From 4e06fd14d5fa78826397c891654a37e5a36ee827 Mon Sep 17 00:00:00 2001 From: Will Newton Date: Tue, 21 Dec 2010 17:24:29 -0800 Subject: include/linux/unaligned: pack the whole struct rather than just the field The current packed struct implementation of unaligned access adds the packed attribute only to the field within the unaligned struct rather than to the struct as a whole. This is not sufficient to enforce proper behaviour on architectures with a default struct alignment of more than one byte. For example, the current implementation of __get_unaligned_cpu16 when compiled for arm with gcc -O1 -mstructure-size-boundary=32 assumes the struct is on a 4 byte boundary so performs the load of the 16bit packed field as if it were on a 4 byte boundary: __get_unaligned_cpu16: ldrh r0, [r0, #0] bx lr Moving the packed attribute to the struct rather than the field causes the proper unaligned access code to be generated: __get_unaligned_cpu16: ldrb r3, [r0, #0] @ zero_extendqisi2 ldrb r0, [r0, #1] @ zero_extendqisi2 orr r0, r3, r0, asl #8 bx lr Signed-off-by: Will Newton Cc: Arnd Bergmann Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/unaligned/packed_struct.h | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) (limited to 'include/linux') diff --git a/include/linux/unaligned/packed_struct.h b/include/linux/unaligned/packed_struct.h index 2498bb9fe002..c9a6abd972a1 100644 --- a/include/linux/unaligned/packed_struct.h +++ b/include/linux/unaligned/packed_struct.h @@ -3,9 +3,9 @@ #include -struct __una_u16 { u16 x __attribute__((packed)); }; -struct __una_u32 { u32 x __attribute__((packed)); }; -struct __una_u64 { u64 x __attribute__((packed)); }; +struct __una_u16 { u16 x; } __attribute__((packed)); +struct __una_u32 { u32 x; } __attribute__((packed)); +struct __una_u64 { u64 x; } __attribute__((packed)); static inline u16 __get_unaligned_cpu16(const void *p) { -- cgit v1.2.3