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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 |