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kernel: add common infrastructure for unaligned access

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Create a linux/unaligned directory similar in spirit to the linux/byteorder
folder to hold generic implementations collected from various arches.

Currently there are five implementations:
1) packed_struct.h: C-struct based, from asm-generic/unaligned.h
2) le_byteshift.h: Open coded byte-swapping, heavily based on asm-arm
3) be_byteshift.h: Open coded byte-swapping, heavily based on asm-arm
4) memmove.h: taken from multiple implementations in tree
5) access_ok.h: taken from x86 and others, unaligned access is ok.

All of the new implementations checks for sizes not equal to 1,2,4,8
and will fail to link.

API additions:

get_unaligned_{le16|le32|le64|be16|be32|be64}(p) which is meant to replace
code of the form:
le16_to_cpu(get_unaligned((__le16 *)p));

put_unaligned_{le16|le32|le64|be16|be32|be64}(val, pointer) which is meant to
replace code of the form:
put_unaligned(cpu_to_le16(val), (__le16 *)p);

The headers that arches should include from their asm/unaligned.h:

access_ok.h : Wrappers of the byteswapping functions in asm/byteorder

Choose a particular implementation for little-endian access:
le_byteshift.h
le_memmove.h (arch must be LE)
le_struct.h (arch must be LE)

Choose a particular implementation for big-endian access:
be_byteshift.h
be_memmove.h (arch must be BE)
be_struct.h (arch must be BE)

After including as needed from the above, include unaligned/generic.h and
define your arch's get/put_unaligned as (for LE):

Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com>
Cc: <linux-arch@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Harvey Harrison 2008-04-29 01:03:27 -07:00 • committed by Linus Torvalds
commit 064106a91b
10 changed files with 510 additions and 0 deletions
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46
include/linux/unaligned/packed_struct.h Normal file
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#ifndef _LINUX_UNALIGNED_PACKED_STRUCT_H
#define _LINUX_UNALIGNED_PACKED_STRUCT_H
#include <linux/kernel.h>
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)
{
const struct __una_u16 *ptr = (const struct __una_u16 *)p;
return ptr->x;
}
static inline u32 __get_unaligned_cpu32(const void *p)
{
const struct __una_u32 *ptr = (const struct __una_u32 *)p;
return ptr->x;
}
static inline u64 __get_unaligned_cpu64(const void *p)
{
const struct __una_u64 *ptr = (const struct __una_u64 *)p;
return ptr->x;
}
static inline void __put_unaligned_cpu16(u16 val, void *p)
{
struct __una_u16 *ptr = (struct __una_u16 *)p;
ptr->x = val;
}
static inline void __put_unaligned_cpu32(u32 val, void *p)
{
struct __una_u32 *ptr = (struct __una_u32 *)p;
ptr->x = val;
}
static inline void __put_unaligned_cpu64(u64 val, void *p)
{
struct __una_u64 *ptr = (struct __una_u64 *)p;
ptr->x = val;
}
#endif /* _LINUX_UNALIGNED_PACKED_STRUCT_H */