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#ifndef xchg
18
19/*
20 * This function doesn't exist, so you'll get a linker error if
21 * something tries to do an invalidly-sized xchg().
22 */
23extern void __xchg_called_with_bad_pointer(void);
24
25static inline
26unsigned long __xchg(unsigned long x, volatile void *ptr, int size)
27{
28	unsigned long ret, flags;
29
30	switch (size) {
31	case 1:
32#ifdef __xchg_u8
33		return __xchg_u8(x, ptr);
34#else
35		local_irq_save(flags);
36		ret = *(volatile u8 *)ptr;
37		*(volatile u8 *)ptr = x;
38		local_irq_restore(flags);
39		return ret;
40#endif /* __xchg_u8 */
41
42	case 2:
43#ifdef __xchg_u16
44		return __xchg_u16(x, ptr);
45#else
46		local_irq_save(flags);
47		ret = *(volatile u16 *)ptr;
48		*(volatile u16 *)ptr = x;
49		local_irq_restore(flags);
50		return ret;
51#endif /* __xchg_u16 */
52
53	case 4:
54#ifdef __xchg_u32
55		return __xchg_u32(x, ptr);
56#else
57		local_irq_save(flags);
58		ret = *(volatile u32 *)ptr;
59		*(volatile u32 *)ptr = x;
60		local_irq_restore(flags);
61		return ret;
62#endif /* __xchg_u32 */
63
64#ifdef CONFIG_64BIT
65	case 8:
66#ifdef __xchg_u64
67		return __xchg_u64(x, ptr);
68#else
69		local_irq_save(flags);
70		ret = *(volatile u64 *)ptr;
71		*(volatile u64 *)ptr = x;
72		local_irq_restore(flags);
73		return ret;
74#endif /* __xchg_u64 */
75#endif /* CONFIG_64BIT */
76
77	default:
78		__xchg_called_with_bad_pointer();
79		return x;
80	}
81}
82
83#define xchg(ptr, x) ({							\
84	((__typeof__(*(ptr)))						\
85		__xchg((unsigned long)(x), (ptr), sizeof(*(ptr))));	\
86})
87
88#endif /* xchg */
89
90/*
91 * Atomic compare and exchange.
92 */
93#include <asm-generic/cmpxchg-local.h>
94
95#ifndef cmpxchg_local
96#define cmpxchg_local(ptr, o, n) ({					       \
97	((__typeof__(*(ptr)))__cmpxchg_local_generic((ptr), (unsigned long)(o),\
98			(unsigned long)(n), sizeof(*(ptr))));		       \
99})
100#endif
101
102#ifndef cmpxchg64_local
103#define cmpxchg64_local(ptr, o, n) __cmpxchg64_local_generic((ptr), (o), (n))
104#endif
105
106#define cmpxchg(ptr, o, n)	cmpxchg_local((ptr), (o), (n))
107#define cmpxchg64(ptr, o, n)	cmpxchg64_local((ptr), (o), (n))
108
109#endif /* __ASM_GENERIC_CMPXCHG_H */
110