linux/include/asm-generic/unaligned.h
Alexander Lobakin b97687527b asm-generic: fix __get_unaligned_be48() on 32 bit platforms
While testing the new macros for working with 48 bit containers,
I faced a weird problem:

32 + 16: 0x2ef6e8da 0x79e60000
48: 0xffffe8da + 0x79e60000

All the bits starting from the 32nd were getting 1d in 9/10 cases.
The debug showed:

p[0]: 0x00002e0000000000
p[1]: 0x00002ef600000000
p[2]: 0xffffffffe8000000
p[3]: 0xffffffffe8da0000
p[4]: 0xffffffffe8da7900
p[5]: 0xffffffffe8da79e6

that the value becomes a garbage after the third OR, i.e. on
`p[2] << 24`.
When the 31st bit is 1 and there's no explicit cast to an unsigned,
it's being considered as a signed int and getting sign-extended on
OR, so `e8000000` becomes `ffffffffe8000000` and messes up the
result.
Cast the @p[2] to u64 as well to avoid this. Now:

32 + 16: 0x7ef6a490 0xddc10000
48: 0x7ef6a490 + 0xddc10000

p[0]: 0x00007e0000000000
p[1]: 0x00007ef600000000
p[2]: 0x00007ef6a4000000
p[3]: 0x00007ef6a4900000
p[4]: 0x00007ef6a490dd00
p[5]: 0x00007ef6a490ddc1

Fixes: c2ea5fcf53 ("asm-generic: introduce be48 unaligned accessors")
Signed-off-by: Alexander Lobakin <alobakin@pm.me>
Link: https://lore.kernel.org/r/20220412215220.75677-1-alobakin@pm.me
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2022-04-12 16:31:38 -06:00

156 lines
3.3 KiB
C

/* SPDX-License-Identifier: GPL-2.0 */
#ifndef __ASM_GENERIC_UNALIGNED_H
#define __ASM_GENERIC_UNALIGNED_H
/*
* This is the most generic implementation of unaligned accesses
* and should work almost anywhere.
*/
#include <linux/unaligned/packed_struct.h>
#include <asm/byteorder.h>
#define __get_unaligned_t(type, ptr) ({ \
const struct { type x; } __packed *__pptr = (typeof(__pptr))(ptr); \
__pptr->x; \
})
#define __put_unaligned_t(type, val, ptr) do { \
struct { type x; } __packed *__pptr = (typeof(__pptr))(ptr); \
__pptr->x = (val); \
} while (0)
#define get_unaligned(ptr) __get_unaligned_t(typeof(*(ptr)), (ptr))
#define put_unaligned(val, ptr) __put_unaligned_t(typeof(*(ptr)), (val), (ptr))
static inline u16 get_unaligned_le16(const void *p)
{
return le16_to_cpu(__get_unaligned_t(__le16, p));
}
static inline u32 get_unaligned_le32(const void *p)
{
return le32_to_cpu(__get_unaligned_t(__le32, p));
}
static inline u64 get_unaligned_le64(const void *p)
{
return le64_to_cpu(__get_unaligned_t(__le64, p));
}
static inline void put_unaligned_le16(u16 val, void *p)
{
__put_unaligned_t(__le16, cpu_to_le16(val), p);
}
static inline void put_unaligned_le32(u32 val, void *p)
{
__put_unaligned_t(__le32, cpu_to_le32(val), p);
}
static inline void put_unaligned_le64(u64 val, void *p)
{
__put_unaligned_t(__le64, cpu_to_le64(val), p);
}
static inline u16 get_unaligned_be16(const void *p)
{
return be16_to_cpu(__get_unaligned_t(__be16, p));
}
static inline u32 get_unaligned_be32(const void *p)
{
return be32_to_cpu(__get_unaligned_t(__be32, p));
}
static inline u64 get_unaligned_be64(const void *p)
{
return be64_to_cpu(__get_unaligned_t(__be64, p));
}
static inline void put_unaligned_be16(u16 val, void *p)
{
__put_unaligned_t(__be16, cpu_to_be16(val), p);
}
static inline void put_unaligned_be32(u32 val, void *p)
{
__put_unaligned_t(__be32, cpu_to_be32(val), p);
}
static inline void put_unaligned_be64(u64 val, void *p)
{
__put_unaligned_t(__be64, cpu_to_be64(val), p);
}
static inline u32 __get_unaligned_be24(const u8 *p)
{
return p[0] << 16 | p[1] << 8 | p[2];
}
static inline u32 get_unaligned_be24(const void *p)
{
return __get_unaligned_be24(p);
}
static inline u32 __get_unaligned_le24(const u8 *p)
{
return p[0] | p[1] << 8 | p[2] << 16;
}
static inline u32 get_unaligned_le24(const void *p)
{
return __get_unaligned_le24(p);
}
static inline void __put_unaligned_be24(const u32 val, u8 *p)
{
*p++ = val >> 16;
*p++ = val >> 8;
*p++ = val;
}
static inline void put_unaligned_be24(const u32 val, void *p)
{
__put_unaligned_be24(val, p);
}
static inline void __put_unaligned_le24(const u32 val, u8 *p)
{
*p++ = val;
*p++ = val >> 8;
*p++ = val >> 16;
}
static inline void put_unaligned_le24(const u32 val, void *p)
{
__put_unaligned_le24(val, p);
}
static inline void __put_unaligned_be48(const u64 val, __u8 *p)
{
*p++ = val >> 40;
*p++ = val >> 32;
*p++ = val >> 24;
*p++ = val >> 16;
*p++ = val >> 8;
*p++ = val;
}
static inline void put_unaligned_be48(const u64 val, void *p)
{
__put_unaligned_be48(val, p);
}
static inline u64 __get_unaligned_be48(const u8 *p)
{
return (u64)p[0] << 40 | (u64)p[1] << 32 | (u64)p[2] << 24 |
p[3] << 16 | p[4] << 8 | p[5];
}
static inline u64 get_unaligned_be48(const void *p)
{
return __get_unaligned_be48(p);
}
#endif /* __ASM_GENERIC_UNALIGNED_H */