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 for futex2 syscalls.
48 *
49 * NOTE: these are not pure flags, they can also be seen as:
50 *
51 * union {
52 * u32 flags;
53 * struct {
54 * u32 size : 2,
55 * numa : 1,
56 * : 4,
57 * private : 1;
58 * };
59 * };
60 */
61#define FUTEX2_SIZE_U8 0x00
62#define FUTEX2_SIZE_U16 0x01
63#define FUTEX2_SIZE_U32 0x02
64#define FUTEX2_SIZE_U64 0x03
65#define FUTEX2_NUMA 0x04
66 /* 0x08 */
67 /* 0x10 */
68 /* 0x20 */
69 /* 0x40 */
70#define FUTEX2_PRIVATE FUTEX_PRIVATE_FLAG
71
72#define FUTEX2_SIZE_MASK 0x03
73
74/* do not use */
75#define FUTEX_32 FUTEX2_SIZE_U32 /* historical accident :-( */
76
77/*
78 * Max numbers of elements in a futex_waitv array
79 */
80#define FUTEX_WAITV_MAX 128
81
82/**
83 * struct futex_waitv - A waiter for vectorized wait
84 * @val: Expected value at uaddr
85 * @uaddr: User address to wait on
86 * @flags: Flags for this waiter
87 * @__reserved: Reserved member to preserve data alignment. Should be 0.
88 */
89struct futex_waitv {
90 __u64 val;
91 __u64 uaddr;
92 __u32 flags;
93 __u32 __reserved;
94};
95
96/*
97 * Support for robust futexes: the kernel cleans up held futexes at
98 * thread exit time.
99 */
100
101/*
102 * Per-lock list entry - embedded in user-space locks, somewhere close
103 * to the futex field. (Note: user-space uses a double-linked list to
104 * achieve O(1) list add and remove, but the kernel only needs to know
105 * about the forward link)
106 *
107 * NOTE: this structure is part of the syscall ABI, and must not be
108 * changed.
109 */
110struct robust_list {
111 struct robust_list *next;
112};
113
114/*
115 * Per-thread list head:
116 *
117 * NOTE: this structure is part of the syscall ABI, and must only be
118 * changed if the change is first communicated with the glibc folks.
119 * (When an incompatible change is done, we'll increase the structure
120 * size, which glibc will detect)
121 */
122struct robust_list_head {
123 /*
124 * The head of the list. Points back to itself if empty:
125 */
126 struct robust_list list;
127
128 /*
129 * This relative offset is set by user-space, it gives the kernel
130 * the relative position of the futex field to examine. This way
131 * we keep userspace flexible, to freely shape its data-structure,
132 * without hardcoding any particular offset into the kernel:
133 */
134 long futex_offset;
135
136 /*
137 * The death of the thread may race with userspace setting
138 * up a lock's links. So to handle this race, userspace first
139 * sets this field to the address of the to-be-taken lock,
140 * then does the lock acquire, and then adds itself to the
141 * list, and then clears this field. Hence the kernel will
142 * always have full knowledge of all locks that the thread
143 * _might_ have taken. We check the owner TID in any case,
144 * so only truly owned locks will be handled.
145 */
146 struct robust_list *list_op_pending;
147};
148
149/*
150 * Are there any waiters for this robust futex:
151 */
152#define FUTEX_WAITERS 0x80000000
153
154/*
155 * The kernel signals via this bit that a thread holding a futex
156 * has exited without unlocking the futex. The kernel also does
157 * a FUTEX_WAKE on such futexes, after setting the bit, to wake
158 * up any possible waiters:
159 */
160#define FUTEX_OWNER_DIED 0x40000000
161
162/*
163 * The rest of the robust-futex field is for the TID:
164 */
165#define FUTEX_TID_MASK 0x3fffffff
166
167/*
168 * This limit protects against a deliberately circular list.
169 * (Not worth introducing an rlimit for it)
170 */
171#define ROBUST_LIST_LIMIT 2048
172
173/*
174 * bitset with all bits set for the FUTEX_xxx_BITSET OPs to request a
175 * match of any bit.
176 */
177#define FUTEX_BITSET_MATCH_ANY 0xffffffff
178
179
180#define FUTEX_OP_SET 0 /* *(int *)UADDR2 = OPARG; */
181#define FUTEX_OP_ADD 1 /* *(int *)UADDR2 += OPARG; */
182#define FUTEX_OP_OR 2 /* *(int *)UADDR2 |= OPARG; */
183#define FUTEX_OP_ANDN 3 /* *(int *)UADDR2 &= ~OPARG; */
184#define FUTEX_OP_XOR 4 /* *(int *)UADDR2 ^= OPARG; */
185
186#define FUTEX_OP_OPARG_SHIFT 8 /* Use (1 << OPARG) instead of OPARG. */
187
188#define FUTEX_OP_CMP_EQ 0 /* if (oldval == CMPARG) wake */
189#define FUTEX_OP_CMP_NE 1 /* if (oldval != CMPARG) wake */
190#define FUTEX_OP_CMP_LT 2 /* if (oldval < CMPARG) wake */
191#define FUTEX_OP_CMP_LE 3 /* if (oldval <= CMPARG) wake */
192#define FUTEX_OP_CMP_GT 4 /* if (oldval > CMPARG) wake */
193#define FUTEX_OP_CMP_GE 5 /* if (oldval >= CMPARG) wake */
194
195/* FUTEX_WAKE_OP will perform atomically
196 int oldval = *(int *)UADDR2;
197 *(int *)UADDR2 = oldval OP OPARG;
198 if (oldval CMP CMPARG)
199 wake UADDR2; */
200
201#define FUTEX_OP(op, oparg, cmp, cmparg) \
202 (((op & 0xf) << 28) | ((cmp & 0xf) << 24) \
203 | ((oparg & 0xfff) << 12) | (cmparg & 0xfff))
204
205#endif /* _LINUX_FUTEX_H */
206