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 #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  */
64 struct 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  */
85 struct robust_list {
86 	struct robust_list __user *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  */
97 struct 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 __user *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 /* _UAPI_LINUX_FUTEX_H */
181