GNU Linux-libre 4.19.211-gnu1
[releases.git] / include / asm-generic / futex.h
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  * -EFAULT - User access resulted in a page fault
27  * -EAGAIN - Atomic operation was unable to complete due to contention
28  * -ENOSYS - Operation not supported
29  */
30 static inline int
31 arch_futex_atomic_op_inuser(int op, u32 oparg, int *oval, u32 __user *uaddr)
32 {
33         int oldval, ret;
34         u32 tmp;
35
36         preempt_disable();
37         pagefault_disable();
38
39         ret = -EFAULT;
40         if (unlikely(get_user(oldval, uaddr) != 0))
41                 goto out_pagefault_enable;
42
43         ret = 0;
44         tmp = oldval;
45
46         switch (op) {
47         case FUTEX_OP_SET:
48                 tmp = oparg;
49                 break;
50         case FUTEX_OP_ADD:
51                 tmp += oparg;
52                 break;
53         case FUTEX_OP_OR:
54                 tmp |= oparg;
55                 break;
56         case FUTEX_OP_ANDN:
57                 tmp &= ~oparg;
58                 break;
59         case FUTEX_OP_XOR:
60                 tmp ^= oparg;
61                 break;
62         default:
63                 ret = -ENOSYS;
64         }
65
66         if (ret == 0 && unlikely(put_user(tmp, uaddr) != 0))
67                 ret = -EFAULT;
68
69 out_pagefault_enable:
70         pagefault_enable();
71         preempt_enable();
72
73         if (ret == 0)
74                 *oval = oldval;
75
76         return ret;
77 }
78
79 /**
80  * futex_atomic_cmpxchg_inatomic() - Compare and exchange the content of the
81  *                              uaddr with newval if the current value is
82  *                              oldval.
83  * @uval:       pointer to store content of @uaddr
84  * @uaddr:      pointer to user space address
85  * @oldval:     old value
86  * @newval:     new value to store to @uaddr
87  *
88  * Return:
89  * 0 - On success
90  * -EFAULT - User access resulted in a page fault
91  * -EAGAIN - Atomic operation was unable to complete due to contention
92  * -ENOSYS - Function not implemented (only if !HAVE_FUTEX_CMPXCHG)
93  */
94 static inline int
95 futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,
96                               u32 oldval, u32 newval)
97 {
98         u32 val;
99
100         preempt_disable();
101         if (unlikely(get_user(val, uaddr) != 0)) {
102                 preempt_enable();
103                 return -EFAULT;
104         }
105
106         if (val == oldval && unlikely(put_user(newval, uaddr) != 0)) {
107                 preempt_enable();
108                 return -EFAULT;
109         }
110
111         *uval = val;
112         preempt_enable();
113
114         return 0;
115 }
116
117 #else
118 static inline int
119 arch_futex_atomic_op_inuser(int op, u32 oparg, int *oval, u32 __user *uaddr)
120 {
121         int oldval = 0, ret;
122
123         pagefault_disable();
124
125         switch (op) {
126         case FUTEX_OP_SET:
127         case FUTEX_OP_ADD:
128         case FUTEX_OP_OR:
129         case FUTEX_OP_ANDN:
130         case FUTEX_OP_XOR:
131         default:
132                 ret = -ENOSYS;
133         }
134
135         pagefault_enable();
136
137         if (!ret)
138                 *oval = oldval;
139
140         return ret;
141 }
142
143 static inline int
144 futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,
145                               u32 oldval, u32 newval)
146 {
147         return -ENOSYS;
148 }
149
150 #endif /* CONFIG_SMP */
151 #endif