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         ((__typeof__(*(ptr)))__get_unaligned((ptr), sizeof(*(ptr))))
  20 #define put_unaligned(x,ptr) \
  21         __put_unaligned((unsigned long)(x), (ptr), sizeof(*(ptr)))
  22
  23 /*
  24  * This function doesn't actually exist.  The idea is that when
  25  * someone uses the macros below with an unsupported size (datatype),
  26  * the linker will alert us to the problem via an unresolved reference
  27  * error.
  28  */
  29 extern void bad_unaligned_access_length(void) __attribute__((noreturn));
  30
  31 struct __una_u64 { __u64 x __attribute__((packed)); };
  32 struct __una_u32 { __u32 x __attribute__((packed)); };
  33 struct __una_u16 { __u16 x __attribute__((packed)); };
  34
  35 /*
  36  * Elemental unaligned loads
  37  */
  38
  39 static inline unsigned long __uldq(const __u64 *addr)
  40 {
  41         const struct __una_u64 *ptr = (const struct __una_u64 *) addr;
  42         return ptr->x;
  43 }
  44
  45 static inline unsigned long __uldl(const __u32 *addr)
  46 {
  47         const struct __una_u32 *ptr = (const struct __una_u32 *) addr;
  48         return ptr->x;
  49 }
  50
  51 static inline unsigned long __uldw(const __u16 *addr)
  52 {
  53         const struct __una_u16 *ptr = (const struct __una_u16 *) addr;
  54         return ptr->x;
  55 }
  56
  57 /*
  58  * Elemental unaligned stores
  59  */
  60
  61 static inline void __ustq(__u64 val, __u64 *addr)
  62 {
  63         struct __una_u64 *ptr = (struct __una_u64 *) addr;
  64         ptr->x = val;
  65 }
  66
  67 static inline void __ustl(__u32 val, __u32 *addr)
  68 {
  69         struct __una_u32 *ptr = (struct __una_u32 *) addr;
  70         ptr->x = val;
  71 }
  72
  73 static inline void __ustw(__u16 val, __u16 *addr)
  74 {
  75         struct __una_u16 *ptr = (struct __una_u16 *) addr;
  76         ptr->x = val;
  77 }
  78
  79 #define __get_unaligned(ptr, size) ({           \
  80         const void *__gu_p = ptr;               \
  81         unsigned long val;                      \
  82         switch (size) {                         \
  83         case 1:                                 \
  84                 val = *(const __u8 *)__gu_p;    \
  85                 break;                          \
  86         case 2:                                 \
  87                 val = __uldw(__gu_p);           \
  88                 break;                          \
  89         case 4:                                 \
  90                 val = __uldl(__gu_p);           \
  91                 break;                          \
  92         case 8:                                 \
  93                 val = __uldq(__gu_p);           \
  94                 break;                          \
  95         default:                                \
  96                 bad_unaligned_access_length();  \
  97         };                                      \
  98         val;                                    \
  99 })
 100
 101 #define __put_unaligned(val, ptr, size)         \
 102 do {                                            \
 103         void *__gu_p = ptr;                     \
 104         switch (size) {                         \
 105         case 1:                                 \
 106                 *(__u8 *)__gu_p = val;          \
 107                 break;                          \
 108         case 2:                                 \
 109                 __ustw(val, __gu_p);            \
 110                 break;                          \
 111         case 4:                                 \
 112                 __ustl(val, __gu_p);            \
 113                 break;                          \
 114         case 8:                                 \
 115                 __ustq(val, __gu_p);            \
 116                 break;                          \
 117         default:                                \
 118                 bad_unaligned_access_length();  \
 119         };                                      \
 120 } while(0)
 121
 122 #endif /* _ASM_GENERIC_UNALIGNED_H */