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  */
58 struct 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  */
70 struct 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