1 /* SPDX-License-Identifier: GPL-2.0 */
2 /*
3 * Generic UP xchg and cmpxchg using interrupt disablement. Does not
4 * support SMP.
5 */
6
7 #ifndef __ASM_GENERIC_CMPXCHG_H
8 #define __ASM_GENERIC_CMPXCHG_H
9
10 #ifdef CONFIG_SMP
11 #error "Cannot use generic cmpxchg on SMP"
12 #endif
13
14 #include <linux/types.h>
15 #include <linux/irqflags.h>
16
17 /*
18 * This function doesn't exist, so you'll get a linker error if
19 * something tries to do an invalidly-sized xchg().
20 */
21 extern void __generic_xchg_called_with_bad_pointer(void);
22
23 static inline
__generic_xchg(unsigned long x,volatile void * ptr,int size)24 unsigned long __generic_xchg(unsigned long x, volatile void *ptr, int size)
25 {
26 unsigned long ret, flags;
27
28 switch (size) {
29 case 1:
30 #ifdef __xchg_u8
31 return __xchg_u8(x, ptr);
32 #else
33 local_irq_save(flags);
34 ret = *(volatile u8 *)ptr;
35 *(volatile u8 *)ptr = x;
36 local_irq_restore(flags);
37 return ret;
38 #endif /* __xchg_u8 */
39
40 case 2:
41 #ifdef __xchg_u16
42 return __xchg_u16(x, ptr);
43 #else
44 local_irq_save(flags);
45 ret = *(volatile u16 *)ptr;
46 *(volatile u16 *)ptr = x;
47 local_irq_restore(flags);
48 return ret;
49 #endif /* __xchg_u16 */
50
51 case 4:
52 #ifdef __xchg_u32
53 return __xchg_u32(x, ptr);
54 #else
55 local_irq_save(flags);
56 ret = *(volatile u32 *)ptr;
57 *(volatile u32 *)ptr = x;
58 local_irq_restore(flags);
59 return ret;
60 #endif /* __xchg_u32 */
61
62 #ifdef CONFIG_64BIT
63 case 8:
64 #ifdef __xchg_u64
65 return __xchg_u64(x, ptr);
66 #else
67 local_irq_save(flags);
68 ret = *(volatile u64 *)ptr;
69 *(volatile u64 *)ptr = x;
70 local_irq_restore(flags);
71 return ret;
72 #endif /* __xchg_u64 */
73 #endif /* CONFIG_64BIT */
74
75 default:
76 __generic_xchg_called_with_bad_pointer();
77 return x;
78 }
79 }
80
81 #define generic_xchg(ptr, x) ({ \
82 ((__typeof__(*(ptr))) \
83 __generic_xchg((unsigned long)(x), (ptr), sizeof(*(ptr)))); \
84 })
85
86 /*
87 * Atomic compare and exchange.
88 */
89 #include <asm-generic/cmpxchg-local.h>
90
91 #define generic_cmpxchg_local(ptr, o, n) ({ \
92 ((__typeof__(*(ptr)))__generic_cmpxchg_local((ptr), (unsigned long)(o), \
93 (unsigned long)(n), sizeof(*(ptr)))); \
94 })
95
96 #define generic_cmpxchg64_local(ptr, o, n) \
97 __generic_cmpxchg64_local((ptr), (o), (n))
98
99
100 #ifndef arch_xchg
101 #define arch_xchg generic_xchg
102 #endif
103
104 #ifndef arch_cmpxchg_local
105 #define arch_cmpxchg_local generic_cmpxchg_local
106 #endif
107
108 #ifndef arch_cmpxchg64_local
109 #define arch_cmpxchg64_local generic_cmpxchg64_local
110 #endif
111
112 #define arch_cmpxchg arch_cmpxchg_local
113 #define arch_cmpxchg64 arch_cmpxchg64_local
114
115 #endif /* __ASM_GENERIC_CMPXCHG_H */
116