1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* 3 * Copyright (c) 2015 Linux Test Project 4 * Copyright (C) 2021 SUSE LLC Andrea Cervesato <[email protected]> 5 */ 6 7 #ifndef LAPI_FUTEX_H__ 8 #define LAPI_FUTEX_H__ 9 10 #include <stdint.h> 11 #include "config.h" 12 13 typedef volatile uint32_t futex_t; 14 15 #if !defined(SYS_futex) && defined(SYS_futex_time64) 16 #define SYS_futex SYS_futex_time64 17 #endif 18 19 #ifdef HAVE_LINUX_FUTEX_H 20 # include <linux/futex.h> 21 #else 22 #include <unistd.h> 23 24 #define FUTEX_WAIT 0 25 #define FUTEX_WAKE 1 26 #define FUTEX_FD 2 27 #define FUTEX_REQUEUE 3 28 #define FUTEX_CMP_REQUEUE 4 29 #define FUTEX_WAKE_OP 5 30 #define FUTEX_LOCK_PI 6 31 #define FUTEX_UNLOCK_PI 7 32 #define FUTEX_TRYLOCK_PI 8 33 #define FUTEX_WAIT_BITSET 9 34 #define FUTEX_WAKE_BITSET 10 35 #define FUTEX_WAIT_REQUEUE_PI 11 36 #define FUTEX_CMP_REQUEUE_PI 12 37 #define FUTEX_LOCK_PI2 13 38 39 #define FUTEX_PRIVATE_FLAG 128 40 #define FUTEX_CLOCK_REALTIME 256 41 #define FUTEX_CMD_MASK ~(FUTEX_PRIVATE_FLAG | FUTEX_CLOCK_REALTIME) 42 43 #define FUTEX_WAIT_PRIVATE (FUTEX_WAIT | FUTEX_PRIVATE_FLAG) 44 #define FUTEX_WAKE_PRIVATE (FUTEX_WAKE | FUTEX_PRIVATE_FLAG) 45 #define FUTEX_REQUEUE_PRIVATE (FUTEX_REQUEUE | FUTEX_PRIVATE_FLAG) 46 #define FUTEX_CMP_REQUEUE_PRIVATE (FUTEX_CMP_REQUEUE | FUTEX_PRIVATE_FLAG) 47 #define FUTEX_WAKE_OP_PRIVATE (FUTEX_WAKE_OP | FUTEX_PRIVATE_FLAG) 48 #define FUTEX_LOCK_PI_PRIVATE (FUTEX_LOCK_PI | FUTEX_PRIVATE_FLAG) 49 #define FUTEX_LOCK_PI2_PRIVATE (FUTEX_LOCK_PI2 | FUTEX_PRIVATE_FLAG) 50 #define FUTEX_UNLOCK_PI_PRIVATE (FUTEX_UNLOCK_PI | FUTEX_PRIVATE_FLAG) 51 #define FUTEX_TRYLOCK_PI_PRIVATE (FUTEX_TRYLOCK_PI | FUTEX_PRIVATE_FLAG) 52 #define FUTEX_WAIT_BITSET_PRIVATE (FUTEX_WAIT_BITSET | FUTEX_PRIVATE_FLAG) 53 #define FUTEX_WAKE_BITSET_PRIVATE (FUTEX_WAKE_BITSET | FUTEX_PRIVATE_FLAG) 54 #define FUTEX_WAIT_REQUEUE_PI_PRIVATE (FUTEX_WAIT_REQUEUE_PI | \ 55 FUTEX_PRIVATE_FLAG) 56 #define FUTEX_CMP_REQUEUE_PI_PRIVATE (FUTEX_CMP_REQUEUE_PI | \ 57 FUTEX_PRIVATE_FLAG) 58 59 /* 60 * Support for robust futexes: the kernel cleans up held futexes at 61 * thread exit time. 62 */ 63 64 /* 65 * Per-lock list entry - embedded in user-space locks, somewhere close 66 * to the futex field. (Note: user-space uses a double-linked list to 67 * achieve O(1) list add and remove, but the kernel only needs to know 68 * about the forward link) 69 * 70 * NOTE: this structure is part of the syscall ABI, and must not be 71 * changed. 72 */ 73 struct robust_list { 74 struct robust_list *next; 75 }; 76 77 /* 78 * Per-thread list head: 79 * 80 * NOTE: this structure is part of the syscall ABI, and must only be 81 * changed if the change is first communicated with the glibc folks. 82 * (When an incompatible change is done, we'll increase the structure 83 * size, which glibc will detect) 84 */ 85 struct robust_list_head { 86 /* 87 * The head of the list. Points back to itself if empty: 88 */ 89 struct robust_list list; 90 91 /* 92 * This relative offset is set by user-space, it gives the kernel 93 * the relative position of the futex field to examine. This way 94 * we keep userspace flexible, to freely shape its data-structure, 95 * without hardcoding any particular offset into the kernel: 96 */ 97 long futex_offset; 98 99 /* 100 * The death of the thread may race with userspace setting 101 * up a lock's links. So to handle this race, userspace first 102 * sets this field to the address of the to-be-taken lock, 103 * then does the lock acquire, and then adds itself to the 104 * list, and then clears this field. Hence the kernel will 105 * always have full knowledge of all locks that the thread 106 * _might_ have taken. We check the owner TID in any case, 107 * so only truly owned locks will be handled. 108 */ 109 struct robust_list *list_op_pending; 110 }; 111 112 /* 113 * Are there any waiters for this robust futex: 114 */ 115 #define FUTEX_WAITERS 0x80000000 116 117 /* 118 * The kernel signals via this bit that a thread holding a futex 119 * has exited without unlocking the futex. The kernel also does 120 * a FUTEX_WAKE on such futexes, after setting the bit, to wake 121 * up any possible waiters: 122 */ 123 #define FUTEX_OWNER_DIED 0x40000000 124 125 /* 126 * The rest of the robust-futex field is for the TID: 127 */ 128 #define FUTEX_TID_MASK 0x3fffffff 129 130 /* 131 * This limit protects against a deliberately circular list. 132 * (Not worth introducing an rlimit for it) 133 */ 134 #define ROBUST_LIST_LIMIT 2048 135 136 /* 137 * bitset with all bits set for the FUTEX_xxx_BITSET OPs to request a 138 * match of any bit. 139 */ 140 #define FUTEX_BITSET_MATCH_ANY 0xffffffff 141 142 143 #define FUTEX_OP_SET 0 /* *(int *)UADDR2 = OPARG; */ 144 #define FUTEX_OP_ADD 1 /* *(int *)UADDR2 += OPARG; */ 145 #define FUTEX_OP_OR 2 /* *(int *)UADDR2 |= OPARG; */ 146 #define FUTEX_OP_ANDN 3 /* *(int *)UADDR2 &= ~OPARG; */ 147 #define FUTEX_OP_XOR 4 /* *(int *)UADDR2 ^= OPARG; */ 148 149 #define FUTEX_OP_OPARG_SHIFT 8 /* Use (1 << OPARG) instead of OPARG. */ 150 151 #define FUTEX_OP_CMP_EQ 0 /* if (oldval == CMPARG) wake */ 152 #define FUTEX_OP_CMP_NE 1 /* if (oldval != CMPARG) wake */ 153 #define FUTEX_OP_CMP_LT 2 /* if (oldval < CMPARG) wake */ 154 #define FUTEX_OP_CMP_LE 3 /* if (oldval <= CMPARG) wake */ 155 #define FUTEX_OP_CMP_GT 4 /* if (oldval > CMPARG) wake */ 156 #define FUTEX_OP_CMP_GE 5 /* if (oldval >= CMPARG) wake */ 157 158 /* FUTEX_WAKE_OP will perform atomically 159 int oldval = *(int *)UADDR2; 160 *(int *)UADDR2 = oldval OP OPARG; 161 if (oldval CMP CMPARG) 162 wake UADDR2; */ 163 164 #define FUTEX_OP(op, oparg, cmp, cmparg) \ 165 (((op & 0xf) << 28) | ((cmp & 0xf) << 24) \ 166 | ((oparg & 0xfff) << 12) | (cmparg & 0xfff)) 167 168 #endif /* HAVE_LINUX_FUTEX_H */ 169 170 #ifndef HAVE_STRUCT_FUTEX_WAITV 171 /* 172 * Flags to specify the bit length of the futex word for futex2 syscalls. 173 * Currently, only 32 is supported. 174 */ 175 #define FUTEX_32 2 176 177 /* 178 * Max numbers of elements in a futex_waitv array 179 */ 180 #define FUTEX_WAITV_MAX 128 181 182 /** 183 * struct futex_waitv - A waiter for vectorized wait 184 * @val: Expected value at uaddr 185 * @uaddr: User address to wait on 186 * @flags: Flags for this waiter 187 * @__reserved: Reserved member to preserve data alignment. Should be 0. 188 */ 189 struct futex_waitv { 190 uint64_t val; 191 uint64_t uaddr; 192 uint32_t flags; 193 uint32_t __reserved; 194 }; 195 #endif /* HAVE_STRUCT_FUTEX_WAITV */ 196 197 #endif /* LAPI_FUTEX_H__ */ 198