1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef _ASM_X86_CMPXCHG_32_H
3 #define _ASM_X86_CMPXCHG_32_H
4
5 /*
6 * Note: if you use set64_bit(), __cmpxchg64(), or their variants, you
7 * you need to test for the feature in boot_cpu_data.
8 */
9
10 /*
11 * CMPXCHG8B only writes to the target if we had the previous
12 * value in registers, otherwise it acts as a read and gives us the
13 * "new previous" value. That is why there is a loop. Preloading
14 * EDX:EAX is a performance optimization: in the common case it means
15 * we need only one locked operation.
16 *
17 * A SIMD/3DNOW!/MMX/FPU 64-bit store here would require at the very
18 * least an FPU save and/or %cr0.ts manipulation.
19 *
20 * cmpxchg8b must be used with the lock prefix here to allow the
21 * instruction to be executed atomically. We need to have the reader
22 * side to see the coherent 64bit value.
23 */
24 static inline void set_64bit(volatile u64 *ptr, u64 value)
25 {
26 u32 low = value;
27 u32 high = value >> 32;
28 u64 prev = *ptr;
29
30 asm volatile("\n1:\t"
31 LOCK_PREFIX "cmpxchg8b %0\n\t"
32 "jnz 1b"
33 : "=m" (*ptr), "+A" (prev)
34 : "b" (low), "c" (high)
35 : "memory");
36 }
37
38 #ifdef CONFIG_X86_CMPXCHG64
39 #define arch_cmpxchg64(ptr, o, n) \
40 ((__typeof__(*(ptr)))__cmpxchg64((ptr), (unsigned long long)(o), \
41 (unsigned long long)(n)))
42 #define arch_cmpxchg64_local(ptr, o, n) \
43 ((__typeof__(*(ptr)))__cmpxchg64_local((ptr), (unsigned long long)(o), \
44 (unsigned long long)(n)))
45 #endif
46
47 static inline u64 __cmpxchg64(volatile u64 *ptr, u64 old, u64 new)
48 {
49 u64 prev;
50 asm volatile(LOCK_PREFIX "cmpxchg8b %1"
51 : "=A" (prev),
52 "+m" (*ptr)
53 : "b" ((u32)new),
54 "c" ((u32)(new >> 32)),
55 "0" (old)
56 : "memory");
57 return prev;
58 }
59
60 static inline u64 __cmpxchg64_local(volatile u64 *ptr, u64 old, u64 new)
61 {
62 u64 prev;
63 asm volatile("cmpxchg8b %1"
64 : "=A" (prev),
65 "+m" (*ptr)
66 : "b" ((u32)new),
67 "c" ((u32)(new >> 32)),
68 "0" (old)
69 : "memory");
70 return prev;
71 }
72
73 #ifndef CONFIG_X86_CMPXCHG64
74 /*
75 * Building a kernel capable running on 80386 and 80486. It may be necessary
76 * to simulate the cmpxchg8b on the 80386 and 80486 CPU.
77 */
78
79 #define arch_cmpxchg64(ptr, o, n) \
80 ({ \
81 __typeof__(*(ptr)) __ret; \
82 __typeof__(*(ptr)) __old = (o); \
83 __typeof__(*(ptr)) __new = (n); \
84 alternative_io(LOCK_PREFIX_HERE \
85 "call cmpxchg8b_emu", \
86 "lock; cmpxchg8b (%%esi)" , \
87 X86_FEATURE_CX8, \
88 "=A" (__ret), \
89 "S" ((ptr)), "0" (__old), \
90 "b" ((unsigned int)__new), \
91 "c" ((unsigned int)(__new>>32)) \
92 : "memory"); \
93 __ret; })
94
95
96 #define arch_cmpxchg64_local(ptr, o, n) \
97 ({ \
98 __typeof__(*(ptr)) __ret; \
99 __typeof__(*(ptr)) __old = (o); \
100 __typeof__(*(ptr)) __new = (n); \
101 alternative_io("call cmpxchg8b_emu", \
102 "cmpxchg8b (%%esi)" , \
103 X86_FEATURE_CX8, \
104 "=A" (__ret), \
105 "S" ((ptr)), "0" (__old), \
106 "b" ((unsigned int)__new), \
107 "c" ((unsigned int)(__new>>32)) \
108 : "memory"); \
109 __ret; })
110
111 #endif
112
113 #define system_has_cmpxchg_double() boot_cpu_has(X86_FEATURE_CX8)
114
115 #endif /* _ASM_X86_CMPXCHG_32_H */