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
arch_futex_atomic_op_inuser(int op,u32 oparg,int * oval,u32 __user * uaddr)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
futex_atomic_cmpxchg_inatomic(u32 * uval,u32 __user * uaddr,u32 oldval,u32 newval)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
arch_futex_atomic_op_inuser(int op,u32 oparg,int * oval,u32 __user * uaddr)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
futex_atomic_cmpxchg_inatomic(u32 * uval,u32 __user * uaddr,u32 oldval,u32 newval)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
152