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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#define FUTEX2_MPOL 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 * When FUTEX2_NUMA doubles the futex word, the second word is a node value.
79 * The special value -1 indicates no-node. This is the same value as
80 * NUMA_NO_NODE, except that value is not ABI, this is.
81 */
82#define FUTEX_NO_NODE (-1)
83
84/*
85 * Max numbers of elements in a futex_waitv array
86 */
87#define FUTEX_WAITV_MAX 128
88
89/**
90 * struct futex_waitv - A waiter for vectorized wait
91 * @val: Expected value at uaddr
92 * @uaddr: User address to wait on
93 * @flags: Flags for this waiter
94 * @__reserved: Reserved member to preserve data alignment. Should be 0.
95 */
96struct futex_waitv {
97 __u64 val;
98 __u64 uaddr;
99 __u32 flags;
100 __u32 __reserved;
101};
102
103/*
104 * Support for robust futexes: the kernel cleans up held futexes at
105 * thread exit time.
106 */
107
108/*
109 * Per-lock list entry - embedded in user-space locks, somewhere close
110 * to the futex field. (Note: user-space uses a double-linked list to
111 * achieve O(1) list add and remove, but the kernel only needs to know
112 * about the forward link)
113 *
114 * NOTE: this structure is part of the syscall ABI, and must not be
115 * changed.
116 */
117struct robust_list {
118 struct robust_list *next;
119};
120
121/*
122 * Per-thread list head:
123 *
124 * NOTE: this structure is part of the syscall ABI, and must only be
125 * changed if the change is first communicated with the glibc folks.
126 * (When an incompatible change is done, we'll increase the structure
127 * size, which glibc will detect)
128 */
129struct robust_list_head {
130 /*
131 * The head of the list. Points back to itself if empty:
132 */
133 struct robust_list list;
134
135 /*
136 * This relative offset is set by user-space, it gives the kernel
137 * the relative position of the futex field to examine. This way
138 * we keep userspace flexible, to freely shape its data-structure,
139 * without hardcoding any particular offset into the kernel:
140 */
141 long futex_offset;
142
143 /*
144 * The death of the thread may race with userspace setting
145 * up a lock's links. So to handle this race, userspace first
146 * sets this field to the address of the to-be-taken lock,
147 * then does the lock acquire, and then adds itself to the
148 * list, and then clears this field. Hence the kernel will
149 * always have full knowledge of all locks that the thread
150 * _might_ have taken. We check the owner TID in any case,
151 * so only truly owned locks will be handled.
152 */
153 struct robust_list *list_op_pending;
154};
155
156/*
157 * Are there any waiters for this robust futex:
158 */
159#define FUTEX_WAITERS 0x80000000
160
161/*
162 * The kernel signals via this bit that a thread holding a futex
163 * has exited without unlocking the futex. The kernel also does
164 * a FUTEX_WAKE on such futexes, after setting the bit, to wake
165 * up any possible waiters:
166 */
167#define FUTEX_OWNER_DIED 0x40000000
168
169/*
170 * The rest of the robust-futex field is for the TID:
171 */
172#define FUTEX_TID_MASK 0x3fffffff
173
174/*
175 * This limit protects against a deliberately circular list.
176 * (Not worth introducing an rlimit for it)
177 */
178#define ROBUST_LIST_LIMIT 2048
179
180/*
181 * bitset with all bits set for the FUTEX_xxx_BITSET OPs to request a
182 * match of any bit.
183 */
184#define FUTEX_BITSET_MATCH_ANY 0xffffffff
185
186
187#define FUTEX_OP_SET 0 /* *(int *)UADDR2 = OPARG; */
188#define FUTEX_OP_ADD 1 /* *(int *)UADDR2 += OPARG; */
189#define FUTEX_OP_OR 2 /* *(int *)UADDR2 |= OPARG; */
190#define FUTEX_OP_ANDN 3 /* *(int *)UADDR2 &= ~OPARG; */
191#define FUTEX_OP_XOR 4 /* *(int *)UADDR2 ^= OPARG; */
192
193#define FUTEX_OP_OPARG_SHIFT 8 /* Use (1 << OPARG) instead of OPARG. */
194
195#define FUTEX_OP_CMP_EQ 0 /* if (oldval == CMPARG) wake */
196#define FUTEX_OP_CMP_NE 1 /* if (oldval != CMPARG) wake */
197#define FUTEX_OP_CMP_LT 2 /* if (oldval < CMPARG) wake */
198#define FUTEX_OP_CMP_LE 3 /* if (oldval <= CMPARG) wake */
199#define FUTEX_OP_CMP_GT 4 /* if (oldval > CMPARG) wake */
200#define FUTEX_OP_CMP_GE 5 /* if (oldval >= CMPARG) wake */
201
202/* FUTEX_WAKE_OP will perform atomically
203 int oldval = *(int *)UADDR2;
204 *(int *)UADDR2 = oldval OP OPARG;
205 if (oldval CMP CMPARG)
206 wake UADDR2; */
207
208#define FUTEX_OP(op, oparg, cmp, cmparg) \
209 (((op & 0xf) << 28) | ((cmp & 0xf) << 24) \
210 | ((oparg & 0xfff) << 12) | (cmparg & 0xfff))
211
212#endif /* _LINUX_FUTEX_H */