Linux kernel mirror (for testing)
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linux
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 futex_atomic_cmpxchg_inatomic
10#ifndef CONFIG_SMP
11/*
12 * The following implementation only for uniprocessor machines.
13 * It relies on preempt_disable() ensuring mutual exclusion.
14 *
15 */
16#define futex_atomic_cmpxchg_inatomic(uval, uaddr, oldval, newval) \
17 futex_atomic_cmpxchg_inatomic_local(uval, uaddr, oldval, newval)
18#define arch_futex_atomic_op_inuser(op, oparg, oval, uaddr) \
19 futex_atomic_op_inuser_local(op, oparg, oval, uaddr)
20#endif /* CONFIG_SMP */
21#endif
22
23/**
24 * futex_atomic_op_inuser_local() - Atomic arithmetic operation with constant
25 * argument and comparison of the previous
26 * futex value with another constant.
27 *
28 * @op: operation to execute
29 * @oparg: argument of the operation
30 * @oval: previous value at @uaddr on successful return
31 * @uaddr: pointer to user space address
32 *
33 * Return:
34 * 0 - On success
35 * -EFAULT - User access resulted in a page fault
36 * -EAGAIN - Atomic operation was unable to complete due to contention
37 * -ENOSYS - Operation not supported
38 */
39static inline int
40futex_atomic_op_inuser_local(int op, u32 oparg, int *oval, u32 __user *uaddr)
41{
42 int oldval, ret;
43 u32 tmp;
44
45 preempt_disable();
46
47 ret = -EFAULT;
48 if (unlikely(get_user(oldval, uaddr) != 0))
49 goto out_pagefault_enable;
50
51 ret = 0;
52 tmp = oldval;
53
54 switch (op) {
55 case FUTEX_OP_SET:
56 tmp = oparg;
57 break;
58 case FUTEX_OP_ADD:
59 tmp += oparg;
60 break;
61 case FUTEX_OP_OR:
62 tmp |= oparg;
63 break;
64 case FUTEX_OP_ANDN:
65 tmp &= ~oparg;
66 break;
67 case FUTEX_OP_XOR:
68 tmp ^= oparg;
69 break;
70 default:
71 ret = -ENOSYS;
72 }
73
74 if (ret == 0 && unlikely(put_user(tmp, uaddr) != 0))
75 ret = -EFAULT;
76
77out_pagefault_enable:
78 preempt_enable();
79
80 if (ret == 0)
81 *oval = oldval;
82
83 return ret;
84}
85
86/**
87 * futex_atomic_cmpxchg_inatomic_local() - Compare and exchange the content of the
88 * uaddr with newval if the current value is
89 * oldval.
90 * @uval: pointer to store content of @uaddr
91 * @uaddr: pointer to user space address
92 * @oldval: old value
93 * @newval: new value to store to @uaddr
94 *
95 * Return:
96 * 0 - On success
97 * -EFAULT - User access resulted in a page fault
98 * -EAGAIN - Atomic operation was unable to complete due to contention
99 */
100static inline int
101futex_atomic_cmpxchg_inatomic_local(u32 *uval, u32 __user *uaddr,
102 u32 oldval, u32 newval)
103{
104 u32 val;
105
106 preempt_disable();
107 if (unlikely(get_user(val, uaddr) != 0)) {
108 preempt_enable();
109 return -EFAULT;
110 }
111
112 if (val == oldval && unlikely(put_user(newval, uaddr) != 0)) {
113 preempt_enable();
114 return -EFAULT;
115 }
116
117 *uval = val;
118 preempt_enable();
119
120 return 0;
121}
122
123#endif