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
futex_atomic_op_inuser_local(int op,u32 oparg,int * oval,u32 __user * uaddr)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
futex_atomic_cmpxchg_inatomic_local(u32 * uval,u32 __user * uaddr,u32 oldval,u32 newval)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