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