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

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 #ifndef TOOLS_ASM_X86_CMPXCHG_H
   3 #define TOOLS_ASM_X86_CMPXCHG_H
   4
   5 #include <linux/compiler.h>
   6
   7 /*
   8  * Non-existant functions to indicate usage errors at link time
   9  * (or compile-time if the compiler implements __compiletime_error().
  10  */
  11 extern void __cmpxchg_wrong_size(void)
  12         __compiletime_error("Bad argument size for cmpxchg");
  13
  14 /*
  15  * Constants for operation sizes. On 32-bit, the 64-bit size it set to
  16  * -1 because sizeof will never return -1, thereby making those switch
  17  * case statements guaranteeed dead code which the compiler will
  18  * eliminate, and allowing the "missing symbol in the default case" to
  19  * indicate a usage error.
  20  */
  21 #define __X86_CASE_B    1
  22 #define __X86_CASE_W    2
  23 #define __X86_CASE_L    4
  24 #ifdef __x86_64__
  25 #define __X86_CASE_Q    8
  26 #else
  27 #define __X86_CASE_Q    -1              /* sizeof will never return -1 */
  28 #endif
  29
  30 /*
  31  * Atomic compare and exchange.  Compare OLD with MEM, if identical,
  32  * store NEW in MEM.  Return the initial value in MEM.  Success is
  33  * indicated by comparing RETURN with OLD.
  34  */
  35 #define __raw_cmpxchg(ptr, old, new, size, lock)                        \
  36 ({                                                                      \
  37         __typeof__(*(ptr)) __ret;                                       \
  38         __typeof__(*(ptr)) __old = (old);                               \
  39         __typeof__(*(ptr)) __new = (new);                               \
  40         switch (size) {                                                 \
  41         case __X86_CASE_B:                                              \
  42         {                                                               \
  43                 volatile u8 *__ptr = (volatile u8 *)(ptr);              \
  44                 asm volatile(lock "cmpxchgb %2,%1"                      \
  45                              : "=a" (__ret), "+m" (*__ptr)              \
  46                              : "q" (__new), "0" (__old)                 \
  47                              : "memory");                               \
  48                 break;                                                  \
  49         }                                                               \
  50         case __X86_CASE_W:                                              \
  51         {                                                               \
  52                 volatile u16 *__ptr = (volatile u16 *)(ptr);            \
  53                 asm volatile(lock "cmpxchgw %2,%1"                      \
  54                              : "=a" (__ret), "+m" (*__ptr)              \
  55                              : "r" (__new), "0" (__old)                 \
  56                              : "memory");                               \
  57                 break;                                                  \
  58         }                                                               \
  59         case __X86_CASE_L:                                              \
  60         {                                                               \
  61                 volatile u32 *__ptr = (volatile u32 *)(ptr);            \
  62                 asm volatile(lock "cmpxchgl %2,%1"                      \
  63                              : "=a" (__ret), "+m" (*__ptr)              \
  64                              : "r" (__new), "0" (__old)                 \
  65                              : "memory");                               \
  66                 break;                                                  \
  67         }                                                               \
  68         case __X86_CASE_Q:                                              \
  69         {                                                               \
  70                 volatile u64 *__ptr = (volatile u64 *)(ptr);            \
  71                 asm volatile(lock "cmpxchgq %2,%1"                      \
  72                              : "=a" (__ret), "+m" (*__ptr)              \
  73                              : "r" (__new), "0" (__old)                 \
  74                              : "memory");                               \
  75                 break;                                                  \
  76         }                                                               \
  77         default:                                                        \
  78                 __cmpxchg_wrong_size();                                 \
  79         }                                                               \
  80         __ret;                                                          \
  81 })
  82
  83 #define __cmpxchg(ptr, old, new, size)                                  \
  84         __raw_cmpxchg((ptr), (old), (new), (size), LOCK_PREFIX)
  85
  86 #define cmpxchg(ptr, old, new)                                          \
  87         __cmpxchg(ptr, old, new, sizeof(*(ptr)))
  88
  89
  90 #endif  /* TOOLS_ASM_X86_CMPXCHG_H */