futex.h

  1/* SPDX-License-Identifier: GPL-2.0 */
  2#ifndef _LINUX_FUTEX_H
  3#define _LINUX_FUTEX_H
  4
  5#include <linux/sched.h>
  6#include <linux/ktime.h>
  7#include <linux/mm_types.h>
  8
  9#include <uapi/linux/futex.h>
 10
 11struct inode;
 12struct task_struct;
 13
 14/*
 15 * Futexes are matched on equal values of this key.
 16 * The key type depends on whether it's a shared or private mapping.
 17 * Don't rearrange members without looking at hash_futex().
 18 *
 19 * offset is aligned to a multiple of sizeof(u32) (== 4) by definition.
 20 * We use the two low order bits of offset to tell what is the kind of key :
 21 *  00 : Private process futex (PTHREAD_PROCESS_PRIVATE)
 22 *       (no reference on an inode or mm)
 23 *  01 : Shared futex (PTHREAD_PROCESS_SHARED)
 24 *	mapped on a file (reference on the underlying inode)
 25 *  10 : Shared futex (PTHREAD_PROCESS_SHARED)
 26 *       (but private mapping on an mm, and reference taken on it)
 27*/
 28
 29#define FUT_OFF_INODE    1 /* We set bit 0 if key has a reference on inode */
 30#define FUT_OFF_MMSHARED 2 /* We set bit 1 if key has a reference on mm */
 31
 32union futex_key {
 33	struct {
 34		u64 i_seq;
 35		unsigned long pgoff;
 36		unsigned int offset;
 37		/* unsigned int node; */
 38	} shared;
 39	struct {
 40		union {
 41			struct mm_struct *mm;
 42			u64 __tmp;
 43		};
 44		unsigned long address;
 45		unsigned int offset;
 46		/* unsigned int node; */
 47	} private;
 48	struct {
 49		u64 ptr;
 50		unsigned long word;
 51		unsigned int offset;
 52		unsigned int node;	/* NOT hashed! */
 53	} both;
 54};
 55
 56#define FUTEX_KEY_INIT (union futex_key) { .both = { .ptr = 0ULL } }
 57
 58#ifdef CONFIG_FUTEX
 59enum {
 60	FUTEX_STATE_OK,
 61	FUTEX_STATE_EXITING,
 62	FUTEX_STATE_DEAD,
 63};
 64
 65static inline void futex_init_task(struct task_struct *tsk)
 66{
 67	tsk->robust_list = NULL;
 68#ifdef CONFIG_COMPAT
 69	tsk->compat_robust_list = NULL;
 70#endif
 71	INIT_LIST_HEAD(&tsk->pi_state_list);
 72	tsk->pi_state_cache = NULL;
 73	tsk->futex_state = FUTEX_STATE_OK;
 74	mutex_init(&tsk->futex_exit_mutex);
 75}
 76
 77void futex_exit_recursive(struct task_struct *tsk);
 78void futex_exit_release(struct task_struct *tsk);
 79void futex_exec_release(struct task_struct *tsk);
 80
 81long do_futex(u32 __user *uaddr, int op, u32 val, ktime_t *timeout,
 82	      u32 __user *uaddr2, u32 val2, u32 val3);
 83int futex_hash_prctl(unsigned long arg2, unsigned long arg3, unsigned long arg4);
 84
 85#ifdef CONFIG_FUTEX_PRIVATE_HASH
 86int futex_hash_allocate_default(void);
 87void futex_hash_free(struct mm_struct *mm);
 88int futex_mm_init(struct mm_struct *mm);
 89
 90#else /* !CONFIG_FUTEX_PRIVATE_HASH */
 91static inline int futex_hash_allocate_default(void) { return 0; }
 92static inline int futex_hash_free(struct mm_struct *mm) { return 0; }
 93static inline int futex_mm_init(struct mm_struct *mm) { return 0; }
 94#endif /* CONFIG_FUTEX_PRIVATE_HASH */
 95
 96#else /* !CONFIG_FUTEX */
 97static inline void futex_init_task(struct task_struct *tsk) { }
 98static inline void futex_exit_recursive(struct task_struct *tsk) { }
 99static inline void futex_exit_release(struct task_struct *tsk) { }
100static inline void futex_exec_release(struct task_struct *tsk) { }
101static inline long do_futex(u32 __user *uaddr, int op, u32 val,
102			    ktime_t *timeout, u32 __user *uaddr2,
103			    u32 val2, u32 val3)
104{
105	return -EINVAL;
106}
107static inline int futex_hash_prctl(unsigned long arg2, unsigned long arg3, unsigned long arg4)
108{
109	return -EINVAL;
110}
111static inline int futex_hash_allocate_default(void)
112{
113	return 0;
114}
115static inline int futex_hash_free(struct mm_struct *mm) { return 0; }
116static inline int futex_mm_init(struct mm_struct *mm) { return 0; }
117
118#endif
119
120#endif