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