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 */
21extern void __generic_xchg_called_with_bad_pointer(void);
22
23static inline
24unsigned 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 & 0xffu);
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 & 0xffffu);
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 & 0xffffffffu);
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