/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _ASM_X86_CMPXCHG_32_H
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#define _ASM_X86_CMPXCHG_32_H
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/*
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* Note: if you use set64_bit(), __cmpxchg64(), or their variants,
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* you need to test for the feature in boot_cpu_data.
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*/
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/*
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* CMPXCHG8B only writes to the target if we had the previous
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* value in registers, otherwise it acts as a read and gives us the
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* "new previous" value. That is why there is a loop. Preloading
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* EDX:EAX is a performance optimization: in the common case it means
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* we need only one locked operation.
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*
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* A SIMD/3DNOW!/MMX/FPU 64-bit store here would require at the very
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* least an FPU save and/or %cr0.ts manipulation.
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*
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* cmpxchg8b must be used with the lock prefix here to allow the
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* instruction to be executed atomically. We need to have the reader
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* side to see the coherent 64bit value.
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*/
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static inline void set_64bit(volatile u64 *ptr, u64 value)
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{
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u32 low = value;
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u32 high = value >> 32;
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u64 prev = *ptr;
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asm volatile("\n1:\t"
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LOCK_PREFIX "cmpxchg8b %0\n\t"
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"jnz 1b"
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: "=m" (*ptr), "+A" (prev)
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: "b" (low), "c" (high)
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: "memory");
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}
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#ifdef CONFIG_X86_CMPXCHG64
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#define arch_cmpxchg64(ptr, o, n) \
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((__typeof__(*(ptr)))__cmpxchg64((ptr), (unsigned long long)(o), \
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(unsigned long long)(n)))
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#define arch_cmpxchg64_local(ptr, o, n) \
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((__typeof__(*(ptr)))__cmpxchg64_local((ptr), (unsigned long long)(o), \
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(unsigned long long)(n)))
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#endif
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static inline u64 __cmpxchg64(volatile u64 *ptr, u64 old, u64 new)
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{
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u64 prev;
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asm volatile(LOCK_PREFIX "cmpxchg8b %1"
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: "=A" (prev),
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"+m" (*ptr)
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: "b" ((u32)new),
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"c" ((u32)(new >> 32)),
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"0" (old)
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: "memory");
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return prev;
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}
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static inline u64 __cmpxchg64_local(volatile u64 *ptr, u64 old, u64 new)
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{
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u64 prev;
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asm volatile("cmpxchg8b %1"
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: "=A" (prev),
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"+m" (*ptr)
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: "b" ((u32)new),
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"c" ((u32)(new >> 32)),
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"0" (old)
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: "memory");
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return prev;
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}
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#ifndef CONFIG_X86_CMPXCHG64
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/*
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* Building a kernel capable running on 80386 and 80486. It may be necessary
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* to simulate the cmpxchg8b on the 80386 and 80486 CPU.
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*/
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#define arch_cmpxchg64(ptr, o, n) \
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({ \
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__typeof__(*(ptr)) __ret; \
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__typeof__(*(ptr)) __old = (o); \
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__typeof__(*(ptr)) __new = (n); \
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alternative_io(LOCK_PREFIX_HERE \
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"call cmpxchg8b_emu", \
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"lock; cmpxchg8b (%%esi)" , \
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X86_FEATURE_CX8, \
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"=A" (__ret), \
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"S" ((ptr)), "0" (__old), \
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"b" ((unsigned int)__new), \
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"c" ((unsigned int)(__new>>32)) \
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: "memory"); \
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__ret; })
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#define arch_cmpxchg64_local(ptr, o, n) \
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({ \
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__typeof__(*(ptr)) __ret; \
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__typeof__(*(ptr)) __old = (o); \
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__typeof__(*(ptr)) __new = (n); \
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alternative_io("call cmpxchg8b_emu", \
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"cmpxchg8b (%%esi)" , \
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X86_FEATURE_CX8, \
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"=A" (__ret), \
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"S" ((ptr)), "0" (__old), \
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"b" ((unsigned int)__new), \
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"c" ((unsigned int)(__new>>32)) \
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: "memory"); \
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__ret; })
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#endif
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#define system_has_cmpxchg_double() boot_cpu_has(X86_FEATURE_CX8)
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#endif /* _ASM_X86_CMPXCHG_32_H */
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