tools/arch/x86/include/asm/cmpxchg.h

   1 #ifndef TOOLS_ASM_X86_CMPXCHG_H
   2 #define TOOLS_ASM_X86_CMPXCHG_H
   3
   4 #include <linux/compiler.h>
   5
   6 /*
   7  * Non-existant functions to indicate usage errors at link time
   8  * (or compile-time if the compiler implements __compiletime_error().
   9  */
  10 extern void __cmpxchg_wrong_size(void)
  11         __compiletime_error("Bad argument size for cmpxchg");
  12
  13 /*
  14  * Constants for operation sizes. On 32-bit, the 64-bit size it set to
  15  * -1 because sizeof will never return -1, thereby making those switch
  16  * case statements guaranteeed dead code which the compiler will
  17  * eliminate, and allowing the "missing symbol in the default case" to
  18  * indicate a usage error.
  19  */
  20 #define __X86_CASE_B    1
  21 #define __X86_CASE_W    2
  22 #define __X86_CASE_L    4
  23 #ifdef __x86_64__
  24 #define __X86_CASE_Q    8
  25 #else
  26 #define __X86_CASE_Q    -1              /* sizeof will never return -1 */
  27 #endif
  28
  29 /*
  30  * Atomic compare and exchange.  Compare OLD with MEM, if identical,
  31  * store NEW in MEM.  Return the initial value in MEM.  Success is
  32  * indicated by comparing RETURN with OLD.
  33  */
  34 #define __raw_cmpxchg(ptr, old, new, size, lock)                        \
  35 ({                                                                      \
  36         __typeof__(*(ptr)) __ret;                                       \
  37         __typeof__(*(ptr)) __old = (old);                               \
  38         __typeof__(*(ptr)) __new = (new);                               \
  39         switch (size) {                                                 \
  40         case __X86_CASE_B:                                              \
  41         {                                                               \
  42                 volatile u8 *__ptr = (volatile u8 *)(ptr);              \
  43                 asm volatile(lock "cmpxchgb %2,%1"                      \
  44                              : "=a" (__ret), "+m" (*__ptr)              \
  45                              : "q" (__new), "0" (__old)                 \
  46                              : "memory");                               \
  47                 break;                                                  \
  48         }                                                               \
  49         case __X86_CASE_W:                                              \
  50         {                                                               \
  51                 volatile u16 *__ptr = (volatile u16 *)(ptr);            \
  52                 asm volatile(lock "cmpxchgw %2,%1"                      \
  53                              : "=a" (__ret), "+m" (*__ptr)              \
  54                              : "r" (__new), "0" (__old)                 \
  55                              : "memory");                               \
  56                 break;                                                  \
  57         }                                                               \
  58         case __X86_CASE_L:                                              \
  59         {                                                               \
  60                 volatile u32 *__ptr = (volatile u32 *)(ptr);            \
  61                 asm volatile(lock "cmpxchgl %2,%1"                      \
  62                              : "=a" (__ret), "+m" (*__ptr)              \
  63                              : "r" (__new), "0" (__old)                 \
  64                              : "memory");                               \
  65                 break;                                                  \
  66         }                                                               \
  67         case __X86_CASE_Q:                                              \
  68         {                                                               \
  69                 volatile u64 *__ptr = (volatile u64 *)(ptr);            \
  70                 asm volatile(lock "cmpxchgq %2,%1"                      \
  71                              : "=a" (__ret), "+m" (*__ptr)              \
  72                              : "r" (__new), "0" (__old)                 \
  73                              : "memory");                               \
  74                 break;                                                  \
  75         }                                                               \
  76         default:                                                        \
  77                 __cmpxchg_wrong_size();                                 \
  78         }                                                               \
  79         __ret;                                                          \
  80 })
  81
  82 #define __cmpxchg(ptr, old, new, size)                                  \
  83         __raw_cmpxchg((ptr), (old), (new), (size), LOCK_PREFIX)
  84
  85 #define cmpxchg(ptr, old, new)                                          \
  86         __cmpxchg(ptr, old, new, sizeof(*(ptr)))
  87
  88
  89 #endif  /* TOOLS_ASM_X86_CMPXCHG_H */