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