/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */

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#ifndef _LINUX_FUTEX_H

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#define _LINUX_FUTEX_H

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#include <linux/types.h>

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/* Second argument to futex syscall */

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#define FUTEX_WAIT 0

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#define FUTEX_WAKE 1

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#define FUTEX_FD 2

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#define FUTEX_REQUEUE 3

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#define FUTEX_CMP_REQUEUE 4

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#define FUTEX_WAKE_OP 5

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#define FUTEX_LOCK_PI 6

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#define FUTEX_UNLOCK_PI 7

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#define FUTEX_TRYLOCK_PI 8

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#define FUTEX_WAIT_BITSET 9

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#define FUTEX_WAKE_BITSET 10

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#define FUTEX_WAIT_REQUEUE_PI 11

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#define FUTEX_CMP_REQUEUE_PI 12

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#define FUTEX_PRIVATE_FLAG 128

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#define FUTEX_CLOCK_REALTIME 256

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#define FUTEX_CMD_MASK ~(FUTEX_PRIVATE_FLAG | FUTEX_CLOCK_REALTIME)

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#define FUTEX_WAIT_PRIVATE (FUTEX_WAIT | FUTEX_PRIVATE_FLAG)

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#define FUTEX_WAKE_PRIVATE (FUTEX_WAKE | FUTEX_PRIVATE_FLAG)

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#define FUTEX_REQUEUE_PRIVATE (FUTEX_REQUEUE | FUTEX_PRIVATE_FLAG)

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#define FUTEX_CMP_REQUEUE_PRIVATE (FUTEX_CMP_REQUEUE | FUTEX_PRIVATE_FLAG)

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#define FUTEX_WAKE_OP_PRIVATE (FUTEX_WAKE_OP | FUTEX_PRIVATE_FLAG)

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#define FUTEX_LOCK_PI_PRIVATE (FUTEX_LOCK_PI | FUTEX_PRIVATE_FLAG)

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#define FUTEX_UNLOCK_PI_PRIVATE (FUTEX_UNLOCK_PI | FUTEX_PRIVATE_FLAG)

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#define FUTEX_TRYLOCK_PI_PRIVATE (FUTEX_TRYLOCK_PI | FUTEX_PRIVATE_FLAG)

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#define FUTEX_WAIT_BITSET_PRIVATE (FUTEX_WAIT_BITSET | FUTEX_PRIVATE_FLAG)

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#define FUTEX_WAKE_BITSET_PRIVATE (FUTEX_WAKE_BITSET | FUTEX_PRIVATE_FLAG)

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#define FUTEX_WAIT_REQUEUE_PI_PRIVATE (FUTEX_WAIT_REQUEUE_PI | \

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FUTEX_PRIVATE_FLAG)

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#define FUTEX_CMP_REQUEUE_PI_PRIVATE (FUTEX_CMP_REQUEUE_PI | \

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FUTEX_PRIVATE_FLAG)

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/*

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* Support for robust futexes: the kernel cleans up held futexes at

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* thread exit time.

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*/

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/*

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* Per-lock list entry - embedded in user-space locks, somewhere close

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* to the futex field. (Note: user-space uses a double-linked list to

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* achieve O(1) list add and remove, but the kernel only needs to know

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* about the forward link)

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*

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* NOTE: this structure is part of the syscall ABI, and must not be

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* changed.

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*/

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struct robust_list {

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struct robust_list *next;

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};

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/*

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* Per-thread list head:

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*

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* NOTE: this structure is part of the syscall ABI, and must only be

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* changed if the change is first communicated with the glibc folks.

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* (When an incompatible change is done, we'll increase the structure

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* size, which glibc will detect)

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*/

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struct robust_list_head {

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/*

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* The head of the list. Points back to itself if empty:

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*/

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struct robust_list list;

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/*

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* This relative offset is set by user-space, it gives the kernel

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* the relative position of the futex field to examine. This way

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* we keep userspace flexible, to freely shape its data-structure,

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* without hardcoding any particular offset into the kernel:

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*/

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long futex_offset;

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/*

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* The death of the thread may race with userspace setting

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* up a lock's links. So to handle this race, userspace first

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* sets this field to the address of the to-be-taken lock,

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* then does the lock acquire, and then adds itself to the

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* list, and then clears this field. Hence the kernel will

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* always have full knowledge of all locks that the thread

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* _might_ have taken. We check the owner TID in any case,

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* so only truly owned locks will be handled.

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*/

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struct robust_list *list_op_pending;

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};

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/*

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* Are there any waiters for this robust futex:

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*/

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#define FUTEX_WAITERS 0x80000000

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/*

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* The kernel signals via this bit that a thread holding a futex

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* has exited without unlocking the futex. The kernel also does

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* a FUTEX_WAKE on such futexes, after setting the bit, to wake

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* up any possible waiters:

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*/

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#define FUTEX_OWNER_DIED 0x40000000

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/*

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* The rest of the robust-futex field is for the TID:

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*/

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#define FUTEX_TID_MASK 0x3fffffff

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/*

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* This limit protects against a deliberately circular list.

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* (Not worth introducing an rlimit for it)

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*/

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#define ROBUST_LIST_LIMIT 2048

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/*

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* bitset with all bits set for the FUTEX_xxx_BITSET OPs to request a

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* match of any bit.

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*/

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#define FUTEX_BITSET_MATCH_ANY 0xffffffff

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#define FUTEX_OP_SET 0 /* *(int *)UADDR2 = OPARG; */

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#define FUTEX_OP_ADD 1 /* *(int *)UADDR2 += OPARG; */

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#define FUTEX_OP_OR 2 /* *(int *)UADDR2 |= OPARG; */

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#define FUTEX_OP_ANDN 3 /* *(int *)UADDR2 &= ~OPARG; */

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#define FUTEX_OP_XOR 4 /* *(int *)UADDR2 ^= OPARG; */

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#define FUTEX_OP_OPARG_SHIFT 8 /* Use (1 << OPARG) instead of OPARG. */

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#define FUTEX_OP_CMP_EQ 0 /* if (oldval == CMPARG) wake */

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#define FUTEX_OP_CMP_NE 1 /* if (oldval != CMPARG) wake */

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#define FUTEX_OP_CMP_LT 2 /* if (oldval < CMPARG) wake */

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#define FUTEX_OP_CMP_LE 3 /* if (oldval <= CMPARG) wake */

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#define FUTEX_OP_CMP_GT 4 /* if (oldval > CMPARG) wake */

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#define FUTEX_OP_CMP_GE 5 /* if (oldval >= CMPARG) wake */

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/* FUTEX_WAKE_OP will perform atomically

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int oldval = *(int *)UADDR2;

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*(int *)UADDR2 = oldval OP OPARG;

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if (oldval CMP CMPARG)

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wake UADDR2; */

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#define FUTEX_OP(op, oparg, cmp, cmparg) \

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(((op & 0xf) << 28) | ((cmp & 0xf) << 24) \

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| ((oparg & 0xfff) << 12) | (cmparg & 0xfff))

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#endif /* _LINUX_FUTEX_H */

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