/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _FUTEX_H
#define _FUTEX_H

#include <linux/futex.h>
#include <linux/rtmutex.h>
#include <linux/sched/wake_q.h>
#include <linux/compat.h>
#include <linux/uaccess.h>
#include <linux/cleanup.h>

#ifdef CONFIG_PREEMPT_RT
#include <linux/rcuwait.h>
#endif

#include <asm/futex.h>

/*
 * Futex flags used to encode options to functions and preserve them across
 * restarts.
 */
#define FLAGS_SIZE_8            0x0000
#define FLAGS_SIZE_16           0x0001
#define FLAGS_SIZE_32           0x0002
#define FLAGS_SIZE_64           0x0003

#define FLAGS_SIZE_MASK         0x0003

#ifdef CONFIG_MMU
# define FLAGS_SHARED           0x0010
#else
/*
 * NOMMU does not have per process address space. Let the compiler optimize
 * code away.
 */
# define FLAGS_SHARED           0x0000
#endif
#define FLAGS_CLOCKRT           0x0020
#define FLAGS_HAS_TIMEOUT       0x0040
#define FLAGS_NUMA              0x0080
#define FLAGS_STRICT            0x0100
#define FLAGS_MPOL              0x0200

/* FUTEX_ to FLAGS_ */
static inline unsigned int futex_to_flags(unsigned int op)
{
        unsigned int flags = FLAGS_SIZE_32;

        if (!(op & FUTEX_PRIVATE_FLAG))
                flags |= FLAGS_SHARED;

        if (op & FUTEX_CLOCK_REALTIME)
                flags |= FLAGS_CLOCKRT;

        return flags;
}

#define FUTEX2_VALID_MASK (FUTEX2_SIZE_MASK | FUTEX2_NUMA | FUTEX2_MPOL | FUTEX2_PRIVATE)

/* FUTEX2_ to FLAGS_ */
static inline unsigned int futex2_to_flags(unsigned int flags2)
{
        unsigned int flags = flags2 & FUTEX2_SIZE_MASK;

        if (!(flags2 & FUTEX2_PRIVATE))
                flags |= FLAGS_SHARED;

        if (flags2 & FUTEX2_NUMA)
                flags |= FLAGS_NUMA;

        if (flags2 & FUTEX2_MPOL)
                flags |= FLAGS_MPOL;

        return flags;
}

static inline unsigned int futex_size(unsigned int flags)
{
        return 1 << (flags & FLAGS_SIZE_MASK);
}

static inline bool futex_flags_valid(unsigned int flags)
{
        /* Only 64bit futexes for 64bit code */
        if (!IS_ENABLED(CONFIG_64BIT) || in_compat_syscall()) {
                if ((flags & FLAGS_SIZE_MASK) == FLAGS_SIZE_64)
                        return false;
        }

        /* Only 32bit futexes are implemented -- for now */
        if ((flags & FLAGS_SIZE_MASK) != FLAGS_SIZE_32)
                return false;

        /*
         * Must be able to represent both FUTEX_NO_NODE and every valid nodeid
         * in a futex word.
         */
        if (flags & FLAGS_NUMA) {
                int bits = 8 * futex_size(flags);
                u64 max = ~0ULL;

                max >>= 64 - bits;
                if (nr_node_ids >= max)
                        return false;
        }

        return true;
}

static inline bool futex_validate_input(unsigned int flags, u64 val)
{
        int bits = 8 * futex_size(flags);

        if (bits < 64 && (val >> bits))
                return false;

        return true;
}

#ifdef CONFIG_FAIL_FUTEX
extern bool should_fail_futex(bool fshared);
#else
static inline bool should_fail_futex(bool fshared)
{
        return false;
}
#endif

/*
 * Hash buckets are shared by all the futex_keys that hash to the same
 * location.  Each key may have multiple futex_q structures, one for each task
 * waiting on a futex.
 */
struct futex_hash_bucket {
        atomic_t waiters;
        spinlock_t lock;
        struct plist_head chain;
        struct futex_private_hash *priv;
} ____cacheline_aligned_in_smp;

/*
 * Priority Inheritance state:
 */
struct futex_pi_state {
        /*
         * list of 'owned' pi_state instances - these have to be
         * cleaned up in do_exit() if the task exits prematurely:
         */
        struct list_head list;

        /*
         * The PI object:
         */
        struct rt_mutex_base pi_mutex;

        struct task_struct *owner;
        refcount_t refcount;

        union futex_key key;
} __randomize_layout;

struct futex_q;
typedef void (futex_wake_fn)(struct wake_q_head *wake_q, struct futex_q *q);

/**
 * struct futex_q - The hashed futex queue entry, one per waiting task
 * @list:               priority-sorted list of tasks waiting on this futex
 * @task:               the task waiting on the futex
 * @lock_ptr:           the hash bucket lock
 * @wake:               the wake handler for this queue
 * @wake_data:          data associated with the wake handler
 * @key:                the key the futex is hashed on
 * @pi_state:           optional priority inheritance state
 * @rt_waiter:          rt_waiter storage for use with requeue_pi
 * @requeue_pi_key:     the requeue_pi target futex key
 * @bitset:             bitset for the optional bitmasked wakeup
 * @requeue_state:      State field for futex_requeue_pi()
 * @drop_hb_ref:        Waiter should drop the extra hash bucket reference if true
 * @requeue_wait:       RCU wait for futex_requeue_pi() (RT only)
 *
 * We use this hashed waitqueue, instead of a normal wait_queue_entry_t, so
 * we can wake only the relevant ones (hashed queues may be shared).
 *
 * A futex_q has a woken state, just like tasks have TASK_RUNNING.
 * It is considered woken when plist_node_empty(&q->list) || q->lock_ptr == 0.
 * The order of wakeup is always to make the first condition true, then
 * the second.
 *
 * PI futexes are typically woken before they are removed from the hash list via
 * the rt_mutex code. See futex_unqueue_pi().
 */
struct futex_q {
        struct plist_node list;

        struct task_struct *task;
        spinlock_t *lock_ptr;
        futex_wake_fn *wake;
        void *wake_data;
        union futex_key key;
        struct futex_pi_state *pi_state;
        struct rt_mutex_waiter *rt_waiter;
        union futex_key *requeue_pi_key;
        u32 bitset;
        atomic_t requeue_state;
        bool drop_hb_ref;
#ifdef CONFIG_PREEMPT_RT
        struct rcuwait requeue_wait;
#endif
} __randomize_layout;

extern const struct futex_q futex_q_init;

enum futex_access {
        FUTEX_READ,
        FUTEX_WRITE
};

extern int get_futex_key(u32 __user *uaddr, unsigned int flags, union futex_key *key,
                         enum futex_access rw);
extern void futex_q_lockptr_lock(struct futex_q *q);
extern struct hrtimer_sleeper *
futex_setup_timer(ktime_t *time, struct hrtimer_sleeper *timeout,
                  int flags, u64 range_ns);

extern struct futex_hash_bucket *futex_hash(union futex_key *key);
#ifdef CONFIG_FUTEX_PRIVATE_HASH
extern void futex_hash_get(struct futex_hash_bucket *hb);
extern void futex_hash_put(struct futex_hash_bucket *hb);

extern struct futex_private_hash *futex_private_hash(void);
extern void futex_private_hash_put(struct futex_private_hash *fph);

#else /* !CONFIG_FUTEX_PRIVATE_HASH */
static inline void futex_hash_get(struct futex_hash_bucket *hb) { }
static inline void futex_hash_put(struct futex_hash_bucket *hb) { }
static inline struct futex_private_hash *futex_private_hash(void) { return NULL; }
static inline void futex_private_hash_put(struct futex_private_hash *fph) { }
#endif

DEFINE_CLASS(hb, struct futex_hash_bucket *,
             if (_T) futex_hash_put(_T),
             futex_hash(key), union futex_key *key);

DEFINE_CLASS(private_hash, struct futex_private_hash *,
             if (_T) futex_private_hash_put(_T),
             futex_private_hash(), void);

/**
 * futex_match - Check whether two futex keys are equal
 * @key1:       Pointer to key1
 * @key2:       Pointer to key2
 *
 * Return 1 if two futex_keys are equal, 0 otherwise.
 */
static inline int futex_match(union futex_key *key1, union futex_key *key2)
{
        return (key1 && key2
                && key1->both.word == key2->both.word
                && key1->both.ptr == key2->both.ptr
                && key1->both.offset == key2->both.offset);
}

extern int futex_wait_setup(u32 __user *uaddr, u32 val, unsigned int flags,
                            struct futex_q *q, union futex_key *key2,
                            struct task_struct *task);
extern void futex_do_wait(struct futex_q *q, struct hrtimer_sleeper *timeout);
extern bool __futex_wake_mark(struct futex_q *q);
extern void futex_wake_mark(struct wake_q_head *wake_q, struct futex_q *q);

extern int fault_in_user_writeable(u32 __user *uaddr);
extern struct futex_q *futex_top_waiter(struct futex_hash_bucket *hb, union futex_key *key);

static inline int futex_cmpxchg_value_locked(u32 *curval, u32 __user *uaddr, u32 uval, u32 newval)
{
        int ret;

        pagefault_disable();
        ret = futex_atomic_cmpxchg_inatomic(curval, uaddr, uval, newval);
        pagefault_enable();

        return ret;
}

/* Read from user memory with pagefaults disabled */
static inline int futex_get_value_locked(u32 *dest, u32 __user *from)
{
        guard(pagefault)();
        return get_user_inline(*dest, from);
}

extern void __futex_unqueue(struct futex_q *q);
extern void __futex_queue(struct futex_q *q, struct futex_hash_bucket *hb,
                                struct task_struct *task);
extern int futex_unqueue(struct futex_q *q);

/**
 * futex_queue() - Enqueue the futex_q on the futex_hash_bucket
 * @q:  The futex_q to enqueue
 * @hb: The destination hash bucket
 * @task: Task queueing this futex
 *
 * The hb->lock must be held by the caller, and is released here. A call to
 * futex_queue() is typically paired with exactly one call to futex_unqueue().  The
 * exceptions involve the PI related operations, which may use futex_unqueue_pi()
 * or nothing if the unqueue is done as part of the wake process and the unqueue
 * state is implicit in the state of woken task (see futex_wait_requeue_pi() for
 * an example).
 *
 * Note that @task may be NULL, for async usage of futexes.
 */
static inline void futex_queue(struct futex_q *q, struct futex_hash_bucket *hb,
                               struct task_struct *task)
        __releases(&hb->lock)
{
        __futex_queue(q, hb, task);
        spin_unlock(&hb->lock);
}

extern void futex_unqueue_pi(struct futex_q *q);

extern void wait_for_owner_exiting(int ret, struct task_struct *exiting);

/*
 * Reflects a new waiter being added to the waitqueue.
 */
static inline void futex_hb_waiters_inc(struct futex_hash_bucket *hb)
{
#ifdef CONFIG_SMP
        atomic_inc(&hb->waiters);
        /*
         * Full barrier (A), see the ordering comment above.
         */
        smp_mb__after_atomic();
#endif
}

/*
 * Reflects a waiter being removed from the waitqueue by wakeup
 * paths.
 */
static inline void futex_hb_waiters_dec(struct futex_hash_bucket *hb)
{
#ifdef CONFIG_SMP
        atomic_dec(&hb->waiters);
#endif
}

static inline int futex_hb_waiters_pending(struct futex_hash_bucket *hb)
{
#ifdef CONFIG_SMP
        /*
         * Full barrier (B), see the ordering comment above.
         */
        smp_mb();
        return atomic_read(&hb->waiters);
#else
        return 1;
#endif
}

extern void futex_q_lock(struct futex_q *q, struct futex_hash_bucket *hb);
extern void futex_q_unlock(struct futex_hash_bucket *hb);


extern int futex_lock_pi_atomic(u32 __user *uaddr, struct futex_hash_bucket *hb,
                                union futex_key *key,
                                struct futex_pi_state **ps,
                                struct task_struct *task,
                                struct task_struct **exiting,
                                int set_waiters);

extern int refill_pi_state_cache(void);
extern void get_pi_state(struct futex_pi_state *pi_state);
extern void put_pi_state(struct futex_pi_state *pi_state);
extern int fixup_pi_owner(u32 __user *uaddr, struct futex_q *q, int locked);

/*
 * Express the locking dependencies for lockdep:
 */
static inline void
double_lock_hb(struct futex_hash_bucket *hb1, struct futex_hash_bucket *hb2)
{
        if (hb1 > hb2)
                swap(hb1, hb2);

        spin_lock(&hb1->lock);
        if (hb1 != hb2)
                spin_lock_nested(&hb2->lock, SINGLE_DEPTH_NESTING);
}

static inline void
double_unlock_hb(struct futex_hash_bucket *hb1, struct futex_hash_bucket *hb2)
{
        spin_unlock(&hb1->lock);
        if (hb1 != hb2)
                spin_unlock(&hb2->lock);
}

/* syscalls */

extern int futex_wait_requeue_pi(u32 __user *uaddr, unsigned int flags, u32
                                 val, ktime_t *abs_time, u32 bitset, u32 __user
                                 *uaddr2);

extern int futex_requeue(u32 __user *uaddr1, unsigned int flags1,
                         u32 __user *uaddr2, unsigned int flags2,
                         int nr_wake, int nr_requeue,
                         u32 *cmpval, int requeue_pi);

extern int __futex_wait(u32 __user *uaddr, unsigned int flags, u32 val,
                        struct hrtimer_sleeper *to, u32 bitset);

extern int futex_wait(u32 __user *uaddr, unsigned int flags, u32 val,
                      ktime_t *abs_time, u32 bitset);

/**
 * struct futex_vector - Auxiliary struct for futex_waitv()
 * @w: Userspace provided data
 * @q: Kernel side data
 *
 * Struct used to build an array with all data need for futex_waitv()
 */
struct futex_vector {
        struct futex_waitv w;
        struct futex_q q;
};

extern int futex_parse_waitv(struct futex_vector *futexv,
                             struct futex_waitv __user *uwaitv,
                             unsigned int nr_futexes, futex_wake_fn *wake,
                             void *wake_data);

extern int futex_wait_multiple_setup(struct futex_vector *vs, int count,
                                     int *woken);

extern int futex_unqueue_multiple(struct futex_vector *v, int count);

extern int futex_wait_multiple(struct futex_vector *vs, unsigned int count,
                               struct hrtimer_sleeper *to);

extern int futex_wake(u32 __user *uaddr, unsigned int flags, int nr_wake, u32 bitset);

extern int futex_wake_op(u32 __user *uaddr1, unsigned int flags,
                         u32 __user *uaddr2, int nr_wake, int nr_wake2, int op);

extern int futex_unlock_pi(u32 __user *uaddr, unsigned int flags);

extern int futex_lock_pi(u32 __user *uaddr, unsigned int flags, ktime_t *time, int trylock);

#endif /* _FUTEX_H */