include/unaligned.h

   1 #ifndef _UNALIGNED_H_
   2 #define _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 /*
  14  * The main single-value unaligned transfer routines.
  15  */
  16 #define get_unaligned(ptr) \
  17         __get_unaligned((ptr), sizeof(*(ptr)))
  18 #define put_unaligned(x,ptr) \
  19         __put_unaligned((__u64)(x), (ptr), sizeof(*(ptr)))
  20
  21 /*
  22  * This function doesn't actually exist.  The idea is that when
  23  * someone uses the macros below with an unsupported size (datatype),
  24  * the linker will alert us to the problem via an unresolved reference
  25  * error.
  26  */
  27 extern void bad_unaligned_access_length(void) __attribute__((noreturn));
  28
  29 struct __una_u64 { __u64 x __attribute__((packed)); };
  30 struct __una_u32 { __u32 x __attribute__((packed)); };
  31 struct __una_u16 { __u16 x __attribute__((packed)); };
  32
  33 /*
  34  * Elemental unaligned loads
  35  */
  36
  37 static inline __u64 __uldq(const __u64 *addr)
  38 {
  39         const struct __una_u64 *ptr = (const struct __una_u64 *) addr;
  40         return ptr->x;
  41 }
  42
  43 static inline __u32 __uldl(const __u32 *addr)
  44 {
  45         const struct __una_u32 *ptr = (const struct __una_u32 *) addr;
  46         return ptr->x;
  47 }
  48
  49 static inline __u16 __uldw(const __u16 *addr)
  50 {
  51         const struct __una_u16 *ptr = (const struct __una_u16 *) addr;
  52         return ptr->x;
  53 }
  54
  55 /*
  56  * Elemental unaligned stores
  57  */
  58
  59 static inline void __ustq(__u64 val, __u64 *addr)
  60 {
  61         struct __una_u64 *ptr = (struct __una_u64 *) addr;
  62         ptr->x = val;
  63 }
  64
  65 static inline void __ustl(__u32 val, __u32 *addr)
  66 {
  67         struct __una_u32 *ptr = (struct __una_u32 *) addr;
  68         ptr->x = val;
  69 }
  70
  71 static inline void __ustw(__u16 val, __u16 *addr)
  72 {
  73         struct __una_u16 *ptr = (struct __una_u16 *) addr;
  74         ptr->x = val;
  75 }
  76
  77 #define __get_unaligned(ptr, size) ({           \
  78         const void *__gu_p = ptr;               \
  79         __u64 val;                              \
  80         switch (size) {                         \
  81         case 1:                                 \
  82                 val = *(const __u8 *)__gu_p;    \
  83                 break;                          \
  84         case 2:                                 \
  85                 val = __uldw(__gu_p);           \
  86                 break;                          \
  87         case 4:                                 \
  88                 val = __uldl(__gu_p);           \
  89                 break;                          \
  90         case 8:                                 \
  91                 val = __uldq(__gu_p);           \
  92                 break;                          \
  93         default:                                \
  94                 bad_unaligned_access_length();  \
  95         };                                      \
  96         (__typeof__(*(ptr)))val;                \
  97 })
  98
  99 #define __put_unaligned(val, ptr, size)         \
 100 do {                                            \
 101         void *__gu_p = ptr;                     \
 102         switch (size) {                         \
 103         case 1:                                 \
 104                 *(__u8 *)__gu_p = val;          \
 105                 break;                          \
 106         case 2:                                 \
 107                 __ustw(val, __gu_p);            \
 108                 break;                          \
 109         case 4:                                 \
 110                 __ustl(val, __gu_p);            \
 111                 break;                          \
 112         case 8:                                 \
 113                 __ustq(val, __gu_p);            \
 114                 break;                          \
 115         default:                                \
 116                 bad_unaligned_access_length();  \
 117         };                                      \
 118 } while(0)
 119
 120 #endif /* _UNALIGNED_H */