include/asm-generic/unaligned.h

   1 #ifndef _ASM_GENERIC_UNALIGNED_H_
   2 #define _ASM_GENERIC_UNALIGNED_H_
   3
   4 /*
   5  * For the benefit of those who are trying to port Linux to another
   6  * architecture, here are some C-language equivalents.
   7  *
   8  * This is based almost entirely upon Richard Henderson's
   9  * asm-alpha/unaligned.h implementation.  Some comments were
  10  * taken from David Mosberger's asm-ia64/unaligned.h header.
  11  */
  12
  13 #include <linux/types.h>
  14
  15 /*
  16  * The main single-value unaligned transfer routines.
  17  */
  18 #define get_unaligned(ptr) \
  19         __get_unaligned((ptr), sizeof(*(ptr)))
  20 #define put_unaligned(x,ptr) \
  21         ((void)sizeof(*(ptr)=(x)),\
  22         __put_unaligned((__force __u64)(x), (ptr), sizeof(*(ptr))))
  23
  24 /*
  25  * This function doesn't actually exist.  The idea is that when
  26  * someone uses the macros below with an unsupported size (datatype),
  27  * the linker will alert us to the problem via an unresolved reference
  28  * error.
  29  */
  30 extern void bad_unaligned_access_length(void) __attribute__((noreturn));
  31
  32 struct __una_u64 { __u64 x __attribute__((packed)); };
  33 struct __una_u32 { __u32 x __attribute__((packed)); };
  34 struct __una_u16 { __u16 x __attribute__((packed)); };
  35
  36 /*
  37  * Elemental unaligned loads
  38  */
  39
  40 static inline __u64 __uldq(const __u64 *addr)
  41 {
  42         const struct __una_u64 *ptr = (const struct __una_u64 *) addr;
  43         return ptr->x;
  44 }
  45
  46 static inline __u32 __uldl(const __u32 *addr)
  47 {
  48         const struct __una_u32 *ptr = (const struct __una_u32 *) addr;
  49         return ptr->x;
  50 }
  51
  52 static inline __u16 __uldw(const __u16 *addr)
  53 {
  54         const struct __una_u16 *ptr = (const struct __una_u16 *) addr;
  55         return ptr->x;
  56 }
  57
  58 /*
  59  * Elemental unaligned stores
  60  */
  61
  62 static inline void __ustq(__u64 val, __u64 *addr)
  63 {
  64         struct __una_u64 *ptr = (struct __una_u64 *) addr;
  65         ptr->x = val;
  66 }
  67
  68 static inline void __ustl(__u32 val, __u32 *addr)
  69 {
  70         struct __una_u32 *ptr = (struct __una_u32 *) addr;
  71         ptr->x = val;
  72 }
  73
  74 static inline void __ustw(__u16 val, __u16 *addr)
  75 {
  76         struct __una_u16 *ptr = (struct __una_u16 *) addr;
  77         ptr->x = val;
  78 }
  79
  80 #define __get_unaligned(ptr, size) ({           \
  81         const void *__gu_p = ptr;               \
  82         __u64 __val;                            \
  83         switch (size) {                         \
  84         case 1:                                 \
  85                 __val = *(const __u8 *)__gu_p;  \
  86                 break;                          \
  87         case 2:                                 \
  88                 __val = __uldw(__gu_p);         \
  89                 break;                          \
  90         case 4:                                 \
  91                 __val = __uldl(__gu_p);         \
  92                 break;                          \
  93         case 8:                                 \
  94                 __val = __uldq(__gu_p);         \
  95                 break;                          \
  96         default:                                \
  97                 bad_unaligned_access_length();  \
  98         };                                      \
  99         (__force __typeof__(*(ptr)))__val;      \
 100 })
 101
 102 #define __put_unaligned(val, ptr, size)         \
 103 ({                                              \
 104         void *__gu_p = ptr;                     \
 105         switch (size) {                         \
 106         case 1:                                 \
 107                 *(__u8 *)__gu_p = (__force __u8)val;            \
 108                 break;                          \
 109         case 2:                                 \
 110                 __ustw((__force __u16)val, __gu_p);             \
 111                 break;                          \
 112         case 4:                                 \
 113                 __ustl((__force __u32)val, __gu_p);             \
 114                 break;                          \
 115         case 8:                                 \
 116                 __ustq(val, __gu_p);            \
 117                 break;                          \
 118         default:                                \
 119                 bad_unaligned_access_length();  \
 120         };                                      \
 121         (void)0;                                \
 122 })
 123
 124 #endif /* _ASM_GENERIC_UNALIGNED_H */