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 */
64struct 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 */
85struct 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 */
97struct 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 */
181