futex.h (5689B)
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 */ 64struct 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 */ 85struct 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 */ 97struct 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 */