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/* SPDX-License-Identifier: GPL-2.0 */
#ifndef TOOLS_ASM_X86_CMPXCHG_H
#define TOOLS_ASM_X86_CMPXCHG_H
#include <linux/compiler.h>
/*
* Non-existant functions to indicate usage errors at link time
* (or compile-time if the compiler implements __compiletime_error().
*/
extern void __cmpxchg_wrong_size(void)
__compiletime_error("Bad argument size for cmpxchg");
/*
* Constants for operation sizes. On 32-bit, the 64-bit size it set to
* -1 because sizeof will never return -1, thereby making those switch
* case statements guaranteeed dead code which the compiler will
* eliminate, and allowing the "missing symbol in the default case" to
* indicate a usage error.
*/
#define __X86_CASE_B 1
#define __X86_CASE_W 2
#define __X86_CASE_L 4
#ifdef __x86_64__
#define __X86_CASE_Q 8
#else
#define __X86_CASE_Q -1 /* sizeof will never return -1 */
#endif
/*
* Atomic compare and exchange. Compare OLD with MEM, if identical,
* store NEW in MEM. Return the initial value in MEM. Success is
* indicated by comparing RETURN with OLD.
*/
#define __raw_cmpxchg(ptr, old, new, size, lock) \
({ \
__typeof__(*(ptr)) __ret; \
__typeof__(*(ptr)) __old = (old); \
__typeof__(*(ptr)) __new = (new); \
switch (size) { \
case __X86_CASE_B: \
{ \
volatile u8 *__ptr = (volatile u8 *)(ptr); \
asm volatile(lock "cmpxchgb %2,%1" \
: "=a" (__ret), "+m" (*__ptr) \
: "q" (__new), "0" (__old) \
: "memory"); \
break; \
} \
case __X86_CASE_W: \
{ \
volatile u16 *__ptr = (volatile u16 *)(ptr); \
asm volatile(lock "cmpxchgw %2,%1" \
: "=a" (__ret), "+m" (*__ptr) \
: "r" (__new), "0" (__old) \
: "memory"); \
break; \
} \
case __X86_CASE_L: \
{ \
volatile u32 *__ptr = (volatile u32 *)(ptr); \
asm volatile(lock "cmpxchgl %2,%1" \
: "=a" (__ret), "+m" (*__ptr) \
: "r" (__new), "0" (__old) \
: "memory"); \
break; \
} \
case __X86_CASE_Q: \
{ \
volatile u64 *__ptr = (volatile u64 *)(ptr); \
asm volatile(lock "cmpxchgq %2,%1" \
: "=a" (__ret), "+m" (*__ptr) \
: "r" (__new), "0" (__old) \
: "memory"); \
break; \
} \
default: \
__cmpxchg_wrong_size(); \
} \
__ret; \
})
#define __cmpxchg(ptr, old, new, size) \
__raw_cmpxchg((ptr), (old), (new), (size), LOCK_PREFIX)
#define cmpxchg(ptr, old, new) \
__cmpxchg(ptr, old, new, sizeof(*(ptr)))
#endif /* TOOLS_ASM_X86_CMPXCHG_H */
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