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 * @encoded_op:	encoded operation to execute
29 * @uaddr:	pointer to user space address
30 *
31 * Return:
32 * 0 - On success
33 * -EFAULT - User access resulted in a page fault
34 * -EAGAIN - Atomic operation was unable to complete due to contention
35 * -ENOSYS - Operation not supported
36 */
37static inline int
38futex_atomic_op_inuser_local(int op, u32 oparg, int *oval, u32 __user *uaddr)
39{
40	int oldval, ret;
41	u32 tmp;
42
43	preempt_disable();
44
45	ret = -EFAULT;
46	if (unlikely(get_user(oldval, uaddr) != 0))
47		goto out_pagefault_enable;
48
49	ret = 0;
50	tmp = oldval;
51
52	switch (op) {
53	case FUTEX_OP_SET:
54		tmp = oparg;
55		break;
56	case FUTEX_OP_ADD:
57		tmp += oparg;
58		break;
59	case FUTEX_OP_OR:
60		tmp |= oparg;
61		break;
62	case FUTEX_OP_ANDN:
63		tmp &= ~oparg;
64		break;
65	case FUTEX_OP_XOR:
66		tmp ^= oparg;
67		break;
68	default:
69		ret = -ENOSYS;
70	}
71
72	if (ret == 0 && unlikely(put_user(tmp, uaddr) != 0))
73		ret = -EFAULT;
74
75out_pagefault_enable:
76	preempt_enable();
77
78	if (ret == 0)
79		*oval = oldval;
80
81	return ret;
82}
83
84/**
85 * futex_atomic_cmpxchg_inatomic_local() - Compare and exchange the content of the
86 *				uaddr with newval if the current value is
87 *				oldval.
88 * @uval:	pointer to store content of @uaddr
89 * @uaddr:	pointer to user space address
90 * @oldval:	old value
91 * @newval:	new value to store to @uaddr
92 *
93 * Return:
94 * 0 - On success
95 * -EFAULT - User access resulted in a page fault
96 * -EAGAIN - Atomic operation was unable to complete due to contention
97 */
98static inline int
99futex_atomic_cmpxchg_inatomic_local(u32 *uval, u32 __user *uaddr,
100			      u32 oldval, u32 newval)
101{
102	u32 val;
103
104	preempt_disable();
105	if (unlikely(get_user(val, uaddr) != 0)) {
106		preempt_enable();
107		return -EFAULT;
108	}
109
110	if (val == oldval && unlikely(put_user(newval, uaddr) != 0)) {
111		preempt_enable();
112		return -EFAULT;
113	}
114
115	*uval = val;
116	preempt_enable();
117
118	return 0;
119}
120
121#endif
122