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1/* SPDX-License-Identifier: GPL-2.0 */
2#ifndef _ASM_GENERIC_FUTEX_H
3#define _ASM_GENERIC_FUTEX_H
4
5#include <linux/futex.h>
6#include <linux/uaccess.h>
7#include <asm/errno.h>
8
9#ifndef CONFIG_SMP
10/*
11 * The following implementation only for uniprocessor machines.
12 * It relies on preempt_disable() ensuring mutual exclusion.
13 *
14 */
15
16/**
17 * arch_futex_atomic_op_inuser() - Atomic arithmetic operation with constant
18 * argument and comparison of the previous
19 * futex value with another constant.
20 *
21 * @encoded_op: encoded operation to execute
22 * @uaddr: pointer to user space address
23 *
24 * Return:
25 * 0 - On success
26 * <0 - On error
27 */
28static inline int
29arch_futex_atomic_op_inuser(int op, u32 oparg, int *oval, u32 __user *uaddr)
30{
31 int oldval, ret;
32 u32 tmp;
33
34 preempt_disable();
35 pagefault_disable();
36
37 ret = -EFAULT;
38 if (unlikely(get_user(oldval, uaddr) != 0))
39 goto out_pagefault_enable;
40
41 ret = 0;
42 tmp = oldval;
43
44 switch (op) {
45 case FUTEX_OP_SET:
46 tmp = oparg;
47 break;
48 case FUTEX_OP_ADD:
49 tmp += oparg;
50 break;
51 case FUTEX_OP_OR:
52 tmp |= oparg;
53 break;
54 case FUTEX_OP_ANDN:
55 tmp &= ~oparg;
56 break;
57 case FUTEX_OP_XOR:
58 tmp ^= oparg;
59 break;
60 default:
61 ret = -ENOSYS;
62 }
63
64 if (ret == 0 && unlikely(put_user(tmp, uaddr) != 0))
65 ret = -EFAULT;
66
67out_pagefault_enable:
68 pagefault_enable();
69 preempt_enable();
70
71 if (ret == 0)
72 *oval = oldval;
73
74 return ret;
75}
76
77/**
78 * futex_atomic_cmpxchg_inatomic() - Compare and exchange the content of the
79 * uaddr with newval if the current value is
80 * oldval.
81 * @uval: pointer to store content of @uaddr
82 * @uaddr: pointer to user space address
83 * @oldval: old value
84 * @newval: new value to store to @uaddr
85 *
86 * Return:
87 * 0 - On success
88 * <0 - On error
89 */
90static inline int
91futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,
92 u32 oldval, u32 newval)
93{
94 u32 val;
95
96 preempt_disable();
97 if (unlikely(get_user(val, uaddr) != 0)) {
98 preempt_enable();
99 return -EFAULT;
100 }
101
102 if (val == oldval && unlikely(put_user(newval, uaddr) != 0)) {
103 preempt_enable();
104 return -EFAULT;
105 }
106
107 *uval = val;
108 preempt_enable();
109
110 return 0;
111}
112
113#else
114static inline int
115arch_futex_atomic_op_inuser(int op, u32 oparg, int *oval, u32 __user *uaddr)
116{
117 int oldval = 0, ret;
118
119 pagefault_disable();
120
121 switch (op) {
122 case FUTEX_OP_SET:
123 case FUTEX_OP_ADD:
124 case FUTEX_OP_OR:
125 case FUTEX_OP_ANDN:
126 case FUTEX_OP_XOR:
127 default:
128 ret = -ENOSYS;
129 }
130
131 pagefault_enable();
132
133 if (!ret)
134 *oval = oldval;
135
136 return ret;
137}
138
139static inline int
140futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,
141 u32 oldval, u32 newval)
142{
143 return -ENOSYS;
144}
145
146#endif /* CONFIG_SMP */
147#endif