xref: /linux/include/uapi/linux/futex.h (revision 0ea5c948cb64bab5bc7a5516774eb8536f05aa0d)
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 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  */
89 struct 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  */
110 struct robust_list {
111 	struct robust_list __user *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  */
122 struct 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 __user *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 /* _UAPI_LINUX_FUTEX_H */
206