LXR linux/include/uapi/linux/futex.h

   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 */
  58struct 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 */
  70struct 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