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