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 */
37 static inline int
38 futex_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
75 out_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 */
98 static inline int
99 futex_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
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