linux-headers (unknown)
1 /* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
2 #ifndef _LINUX_FUTEX_H
3 #define _LINUX_FUTEX_H
4
5
6 #include <linux/types.h>
7
8 /* Second argument to futex syscall */
9
10
11 #define FUTEX_WAIT 0
12 #define FUTEX_WAKE 1
13 #define FUTEX_FD 2
14 #define FUTEX_REQUEUE 3
15 #define FUTEX_CMP_REQUEUE 4
16 #define FUTEX_WAKE_OP 5
17 #define FUTEX_LOCK_PI 6
18 #define FUTEX_UNLOCK_PI 7
19 #define FUTEX_TRYLOCK_PI 8
20 #define FUTEX_WAIT_BITSET 9
21 #define FUTEX_WAKE_BITSET 10
22 #define FUTEX_WAIT_REQUEUE_PI 11
23 #define FUTEX_CMP_REQUEUE_PI 12
24 #define FUTEX_LOCK_PI2 13
25
26 #define FUTEX_PRIVATE_FLAG 128
27 #define FUTEX_CLOCK_REALTIME 256
28 #define FUTEX_CMD_MASK ~(FUTEX_PRIVATE_FLAG | FUTEX_CLOCK_REALTIME)
29
30 #define FUTEX_WAIT_PRIVATE (FUTEX_WAIT | FUTEX_PRIVATE_FLAG)
31 #define FUTEX_WAKE_PRIVATE (FUTEX_WAKE | FUTEX_PRIVATE_FLAG)
32 #define FUTEX_REQUEUE_PRIVATE (FUTEX_REQUEUE | FUTEX_PRIVATE_FLAG)
33 #define FUTEX_CMP_REQUEUE_PRIVATE (FUTEX_CMP_REQUEUE | FUTEX_PRIVATE_FLAG)
34 #define FUTEX_WAKE_OP_PRIVATE (FUTEX_WAKE_OP | FUTEX_PRIVATE_FLAG)
35 #define FUTEX_LOCK_PI_PRIVATE (FUTEX_LOCK_PI | FUTEX_PRIVATE_FLAG)
36 #define FUTEX_LOCK_PI2_PRIVATE (FUTEX_LOCK_PI2 | FUTEX_PRIVATE_FLAG)
37 #define FUTEX_UNLOCK_PI_PRIVATE (FUTEX_UNLOCK_PI | FUTEX_PRIVATE_FLAG)
38 #define FUTEX_TRYLOCK_PI_PRIVATE (FUTEX_TRYLOCK_PI | FUTEX_PRIVATE_FLAG)
39 #define FUTEX_WAIT_BITSET_PRIVATE (FUTEX_WAIT_BITSET | FUTEX_PRIVATE_FLAG)
40 #define FUTEX_WAKE_BITSET_PRIVATE (FUTEX_WAKE_BITSET | FUTEX_PRIVATE_FLAG)
41 #define FUTEX_WAIT_REQUEUE_PI_PRIVATE (FUTEX_WAIT_REQUEUE_PI | \
42 FUTEX_PRIVATE_FLAG)
43 #define FUTEX_CMP_REQUEUE_PI_PRIVATE (FUTEX_CMP_REQUEUE_PI | \
44 FUTEX_PRIVATE_FLAG)
45
46 /*
47 * Flags to specify the bit length of the futex word for futex2 syscalls.
48 * Currently, only 32 is supported.
49 */
50 #define FUTEX_32 2
51
52 /*
53 * Max numbers of elements in a futex_waitv array
54 */
55 #define FUTEX_WAITV_MAX 128
56
57 /**
58 * struct futex_waitv - A waiter for vectorized wait
59 * @val: Expected value at uaddr
60 * @uaddr: User address to wait on
61 * @flags: Flags for this waiter
62 * @__reserved: Reserved member to preserve data alignment. Should be 0.
63 */
64 struct futex_waitv {
65 __u64 val;
66 __u64 uaddr;
67 __u32 flags;
68 __u32 __reserved;
69 };
70
71 /*
72 * Support for robust futexes: the kernel cleans up held futexes at
73 * thread exit time.
74 */
75
76 /*
77 * Per-lock list entry - embedded in user-space locks, somewhere close
78 * to the futex field. (Note: user-space uses a double-linked list to
79 * achieve O(1) list add and remove, but the kernel only needs to know
80 * about the forward link)
81 *
82 * NOTE: this structure is part of the syscall ABI, and must not be
83 * changed.
84 */
85 struct robust_list {
86 struct robust_list *next;
87 };
88
89 /*
90 * Per-thread list head:
91 *
92 * NOTE: this structure is part of the syscall ABI, and must only be
93 * changed if the change is first communicated with the glibc folks.
94 * (When an incompatible change is done, we'll increase the structure
95 * size, which glibc will detect)
96 */
97 struct robust_list_head {
98 /*
99 * The head of the list. Points back to itself if empty:
100 */
101 struct robust_list list;
102
103 /*
104 * This relative offset is set by user-space, it gives the kernel
105 * the relative position of the futex field to examine. This way
106 * we keep userspace flexible, to freely shape its data-structure,
107 * without hardcoding any particular offset into the kernel:
108 */
109 long futex_offset;
110
111 /*
112 * The death of the thread may race with userspace setting
113 * up a lock's links. So to handle this race, userspace first
114 * sets this field to the address of the to-be-taken lock,
115 * then does the lock acquire, and then adds itself to the
116 * list, and then clears this field. Hence the kernel will
117 * always have full knowledge of all locks that the thread
118 * _might_ have taken. We check the owner TID in any case,
119 * so only truly owned locks will be handled.
120 */
121 struct robust_list *list_op_pending;
122 };
123
124 /*
125 * Are there any waiters for this robust futex:
126 */
127 #define FUTEX_WAITERS 0x80000000
128
129 /*
130 * The kernel signals via this bit that a thread holding a futex
131 * has exited without unlocking the futex. The kernel also does
132 * a FUTEX_WAKE on such futexes, after setting the bit, to wake
133 * up any possible waiters:
134 */
135 #define FUTEX_OWNER_DIED 0x40000000
136
137 /*
138 * The rest of the robust-futex field is for the TID:
139 */
140 #define FUTEX_TID_MASK 0x3fffffff
141
142 /*
143 * This limit protects against a deliberately circular list.
144 * (Not worth introducing an rlimit for it)
145 */
146 #define ROBUST_LIST_LIMIT 2048
147
148 /*
149 * bitset with all bits set for the FUTEX_xxx_BITSET OPs to request a
150 * match of any bit.
151 */
152 #define FUTEX_BITSET_MATCH_ANY 0xffffffff
153
154
155 #define FUTEX_OP_SET 0 /* *(int *)UADDR2 = OPARG; */
156 #define FUTEX_OP_ADD 1 /* *(int *)UADDR2 += OPARG; */
157 #define FUTEX_OP_OR 2 /* *(int *)UADDR2 |= OPARG; */
158 #define FUTEX_OP_ANDN 3 /* *(int *)UADDR2 &= ~OPARG; */
159 #define FUTEX_OP_XOR 4 /* *(int *)UADDR2 ^= OPARG; */
160
161 #define FUTEX_OP_OPARG_SHIFT 8 /* Use (1 << OPARG) instead of OPARG. */
162
163 #define FUTEX_OP_CMP_EQ 0 /* if (oldval == CMPARG) wake */
164 #define FUTEX_OP_CMP_NE 1 /* if (oldval != CMPARG) wake */
165 #define FUTEX_OP_CMP_LT 2 /* if (oldval < CMPARG) wake */
166 #define FUTEX_OP_CMP_LE 3 /* if (oldval <= CMPARG) wake */
167 #define FUTEX_OP_CMP_GT 4 /* if (oldval > CMPARG) wake */
168 #define FUTEX_OP_CMP_GE 5 /* if (oldval >= CMPARG) wake */
169
170 /* FUTEX_WAKE_OP will perform atomically
171 int oldval = *(int *)UADDR2;
172 *(int *)UADDR2 = oldval OP OPARG;
173 if (oldval CMP CMPARG)
174 wake UADDR2; */
175
176 #define FUTEX_OP(op, oparg, cmp, cmparg) \
177 (((op & 0xf) << 28) | ((cmp & 0xf) << 24) \
178 | ((oparg & 0xfff) << 12) | (cmparg & 0xfff))
179
180 #endif /* _LINUX_FUTEX_H */
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