arm64: dts: qcom: sm8550: add TRNG node

[linux-modified.git] / kernel / time / posix-timers.c

// SPDX-License-Identifier: GPL-2.0+
/*
 * 2002-10-15  Posix Clocks & timers
 *                           by George Anzinger george@mvista.com
 *                           Copyright (C) 2002 2003 by MontaVista Software.
 *
 * 2004-06-01  Fix CLOCK_REALTIME clock/timer TIMER_ABSTIME bug.
 *                           Copyright (C) 2004 Boris Hu
 *
 * These are all the functions necessary to implement POSIX clocks & timers
 */
#include <linux/mm.h>
#include <linux/interrupt.h>
#include <linux/slab.h>
#include <linux/time.h>
#include <linux/mutex.h>
#include <linux/sched/task.h>

#include <linux/uaccess.h>
#include <linux/list.h>
#include <linux/init.h>
#include <linux/compiler.h>
#include <linux/hash.h>
#include <linux/posix-clock.h>
#include <linux/posix-timers.h>
#include <linux/syscalls.h>
#include <linux/wait.h>
#include <linux/workqueue.h>
#include <linux/export.h>
#include <linux/hashtable.h>
#include <linux/compat.h>
#include <linux/nospec.h>
#include <linux/time_namespace.h>

#include "timekeeping.h"
#include "posix-timers.h"

static struct kmem_cache *posix_timers_cache;

/*
 * Timers are managed in a hash table for lockless lookup. The hash key is
 * constructed from current::signal and the timer ID and the timer is
 * matched against current::signal and the timer ID when walking the hash
 * bucket list.
 *
 * This allows checkpoint/restore to reconstruct the exact timer IDs for
 * a process.
 */
static DEFINE_HASHTABLE(posix_timers_hashtable, 9);
static DEFINE_SPINLOCK(hash_lock);

static const struct k_clock * const posix_clocks[];
static const struct k_clock *clockid_to_kclock(const clockid_t id);
static const struct k_clock clock_realtime, clock_monotonic;

/* SIGEV_THREAD_ID cannot share a bit with the other SIGEV values. */
#if SIGEV_THREAD_ID != (SIGEV_THREAD_ID & \
                        ~(SIGEV_SIGNAL | SIGEV_NONE | SIGEV_THREAD))
#error "SIGEV_THREAD_ID must not share bit with other SIGEV values!"
#endif

static struct k_itimer *__lock_timer(timer_t timer_id, unsigned long *flags);

#define lock_timer(tid, flags)                                             \
({      struct k_itimer *__timr;                                           \
        __cond_lock(&__timr->it_lock, __timr = __lock_timer(tid, flags));  \
        __timr;                                                            \
})

static int hash(struct signal_struct *sig, unsigned int nr)
{
        return hash_32(hash32_ptr(sig) ^ nr, HASH_BITS(posix_timers_hashtable));
}

static struct k_itimer *__posix_timers_find(struct hlist_head *head,
                                            struct signal_struct *sig,
                                            timer_t id)
{
        struct k_itimer *timer;

        hlist_for_each_entry_rcu(timer, head, t_hash, lockdep_is_held(&hash_lock)) {
                /* timer->it_signal can be set concurrently */
                if ((READ_ONCE(timer->it_signal) == sig) && (timer->it_id == id))
                        return timer;
        }
        return NULL;
}

static struct k_itimer *posix_timer_by_id(timer_t id)
{
        struct signal_struct *sig = current->signal;
        struct hlist_head *head = &posix_timers_hashtable[hash(sig, id)];

        return __posix_timers_find(head, sig, id);
}

static int posix_timer_add(struct k_itimer *timer)
{
        struct signal_struct *sig = current->signal;
        struct hlist_head *head;
        unsigned int cnt, id;

        /*
         * FIXME: Replace this by a per signal struct xarray once there is
         * a plan to handle the resulting CRIU regression gracefully.
         */
        for (cnt = 0; cnt <= INT_MAX; cnt++) {
                spin_lock(&hash_lock);
                id = sig->next_posix_timer_id;

                /* Write the next ID back. Clamp it to the positive space */
                sig->next_posix_timer_id = (id + 1) & INT_MAX;

                head = &posix_timers_hashtable[hash(sig, id)];
                if (!__posix_timers_find(head, sig, id)) {
                        hlist_add_head_rcu(&timer->t_hash, head);
                        spin_unlock(&hash_lock);
                        return id;
                }
                spin_unlock(&hash_lock);
        }
        /* POSIX return code when no timer ID could be allocated */
        return -EAGAIN;
}

static inline void unlock_timer(struct k_itimer *timr, unsigned long flags)
{
        spin_unlock_irqrestore(&timr->it_lock, flags);
}

static int posix_get_realtime_timespec(clockid_t which_clock, struct timespec64 *tp)
{
        ktime_get_real_ts64(tp);
        return 0;
}

static ktime_t posix_get_realtime_ktime(clockid_t which_clock)
{
        return ktime_get_real();
}

static int posix_clock_realtime_set(const clockid_t which_clock,
                                    const struct timespec64 *tp)
{
        return do_sys_settimeofday64(tp, NULL);
}

static int posix_clock_realtime_adj(const clockid_t which_clock,
                                    struct __kernel_timex *t)
{
        return do_adjtimex(t);
}

static int posix_get_monotonic_timespec(clockid_t which_clock, struct timespec64 *tp)
{
        ktime_get_ts64(tp);
        timens_add_monotonic(tp);
        return 0;
}

static ktime_t posix_get_monotonic_ktime(clockid_t which_clock)
{
        return ktime_get();
}

static int posix_get_monotonic_raw(clockid_t which_clock, struct timespec64 *tp)
{
        ktime_get_raw_ts64(tp);
        timens_add_monotonic(tp);
        return 0;
}

static int posix_get_realtime_coarse(clockid_t which_clock, struct timespec64 *tp)
{
        ktime_get_coarse_real_ts64(tp);
        return 0;
}

static int posix_get_monotonic_coarse(clockid_t which_clock,
                                                struct timespec64 *tp)
{
        ktime_get_coarse_ts64(tp);
        timens_add_monotonic(tp);
        return 0;
}

static int posix_get_coarse_res(const clockid_t which_clock, struct timespec64 *tp)
{
        *tp = ktime_to_timespec64(KTIME_LOW_RES);
        return 0;
}

static int posix_get_boottime_timespec(const clockid_t which_clock, struct timespec64 *tp)
{
        ktime_get_boottime_ts64(tp);
        timens_add_boottime(tp);
        return 0;
}

static ktime_t posix_get_boottime_ktime(const clockid_t which_clock)
{
        return ktime_get_boottime();
}

static int posix_get_tai_timespec(clockid_t which_clock, struct timespec64 *tp)
{
        ktime_get_clocktai_ts64(tp);
        return 0;
}

static ktime_t posix_get_tai_ktime(clockid_t which_clock)
{
        return ktime_get_clocktai();
}

static int posix_get_hrtimer_res(clockid_t which_clock, struct timespec64 *tp)
{
        tp->tv_sec = 0;
        tp->tv_nsec = hrtimer_resolution;
        return 0;
}

static __init int init_posix_timers(void)
{
        posix_timers_cache = kmem_cache_create("posix_timers_cache",
                                        sizeof(struct k_itimer), 0,
                                        SLAB_PANIC | SLAB_ACCOUNT, NULL);
        return 0;
}
__initcall(init_posix_timers);

/*
 * The siginfo si_overrun field and the return value of timer_getoverrun(2)
 * are of type int. Clamp the overrun value to INT_MAX
 */
static inline int timer_overrun_to_int(struct k_itimer *timr, int baseval)
{
        s64 sum = timr->it_overrun_last + (s64)baseval;

        return sum > (s64)INT_MAX ? INT_MAX : (int)sum;
}

static void common_hrtimer_rearm(struct k_itimer *timr)
{
        struct hrtimer *timer = &timr->it.real.timer;

        timr->it_overrun += hrtimer_forward(timer, timer->base->get_time(),
                                            timr->it_interval);
        hrtimer_restart(timer);
}

/*
 * This function is called from the signal delivery code if
 * info->si_sys_private is not zero, which indicates that the timer has to
 * be rearmed. Restart the timer and update info::si_overrun.
 */
void posixtimer_rearm(struct kernel_siginfo *info)
{
        struct k_itimer *timr;
        unsigned long flags;

        timr = lock_timer(info->si_tid, &flags);
        if (!timr)
                return;

        if (timr->it_interval && timr->it_requeue_pending == info->si_sys_private) {
                timr->kclock->timer_rearm(timr);

                timr->it_active = 1;
                timr->it_overrun_last = timr->it_overrun;
                timr->it_overrun = -1LL;
                ++timr->it_requeue_pending;

                info->si_overrun = timer_overrun_to_int(timr, info->si_overrun);
        }

        unlock_timer(timr, flags);
}

int posix_timer_event(struct k_itimer *timr, int si_private)
{
        enum pid_type type;
        int ret;
        /*
         * FIXME: if ->sigq is queued we can race with
         * dequeue_signal()->posixtimer_rearm().
         *
         * If dequeue_signal() sees the "right" value of
         * si_sys_private it calls posixtimer_rearm().
         * We re-queue ->sigq and drop ->it_lock().
         * posixtimer_rearm() locks the timer
         * and re-schedules it while ->sigq is pending.
         * Not really bad, but not that we want.
         */
        timr->sigq->info.si_sys_private = si_private;

        type = !(timr->it_sigev_notify & SIGEV_THREAD_ID) ? PIDTYPE_TGID : PIDTYPE_PID;
        ret = send_sigqueue(timr->sigq, timr->it_pid, type);
        /* If we failed to send the signal the timer stops. */
        return ret > 0;
}

/*
 * This function gets called when a POSIX.1b interval timer expires from
 * the HRTIMER interrupt (soft interrupt on RT kernels).
 *
 * Handles CLOCK_REALTIME, CLOCK_MONOTONIC, CLOCK_BOOTTIME and CLOCK_TAI
 * based timers.
 */
static enum hrtimer_restart posix_timer_fn(struct hrtimer *timer)
{
        enum hrtimer_restart ret = HRTIMER_NORESTART;
        struct k_itimer *timr;
        unsigned long flags;
        int si_private = 0;

        timr = container_of(timer, struct k_itimer, it.real.timer);
        spin_lock_irqsave(&timr->it_lock, flags);

        timr->it_active = 0;
        if (timr->it_interval != 0)
                si_private = ++timr->it_requeue_pending;

        if (posix_timer_event(timr, si_private)) {
                /*
                 * The signal was not queued due to SIG_IGN. As a
                 * consequence the timer is not going to be rearmed from
                 * the signal delivery path. But as a real signal handler
                 * can be installed later the timer must be rearmed here.
                 */
                if (timr->it_interval != 0) {
                        ktime_t now = hrtimer_cb_get_time(timer);

                        /*
                         * FIXME: What we really want, is to stop this
                         * timer completely and restart it in case the
                         * SIG_IGN is removed. This is a non trivial
                         * change to the signal handling code.
                         *
                         * For now let timers with an interval less than a
                         * jiffie expire every jiffie and recheck for a
                         * valid signal handler.
                         *
                         * This avoids interrupt starvation in case of a
                         * very small interval, which would expire the
                         * timer immediately again.
                         *
                         * Moving now ahead of time by one jiffie tricks
                         * hrtimer_forward() to expire the timer later,
                         * while it still maintains the overrun accuracy
                         * for the price of a slight inconsistency in the
                         * timer_gettime() case. This is at least better
                         * than a timer storm.
                         *
                         * Only required when high resolution timers are
                         * enabled as the periodic tick based timers are
                         * automatically aligned to the next tick.
                         */
                        if (IS_ENABLED(CONFIG_HIGH_RES_TIMERS)) {
                                ktime_t kj = TICK_NSEC;

                                if (timr->it_interval < kj)
                                        now = ktime_add(now, kj);
                        }

                        timr->it_overrun += hrtimer_forward(timer, now, timr->it_interval);
                        ret = HRTIMER_RESTART;
                        ++timr->it_requeue_pending;
                        timr->it_active = 1;
                }
        }

        unlock_timer(timr, flags);
        return ret;
}

static struct pid *good_sigevent(sigevent_t * event)
{
        struct pid *pid = task_tgid(current);
        struct task_struct *rtn;

        switch (event->sigev_notify) {
        case SIGEV_SIGNAL | SIGEV_THREAD_ID:
                pid = find_vpid(event->sigev_notify_thread_id);
                rtn = pid_task(pid, PIDTYPE_PID);
                if (!rtn || !same_thread_group(rtn, current))
                        return NULL;
                fallthrough;
        case SIGEV_SIGNAL:
        case SIGEV_THREAD:
                if (event->sigev_signo <= 0 || event->sigev_signo > SIGRTMAX)
                        return NULL;
                fallthrough;
        case SIGEV_NONE:
                return pid;
        default:
                return NULL;
        }
}

static struct k_itimer * alloc_posix_timer(void)
{
        struct k_itimer *tmr = kmem_cache_zalloc(posix_timers_cache, GFP_KERNEL);

        if (!tmr)
                return tmr;
        if (unlikely(!(tmr->sigq = sigqueue_alloc()))) {
                kmem_cache_free(posix_timers_cache, tmr);
                return NULL;
        }
        clear_siginfo(&tmr->sigq->info);
        return tmr;
}

static void k_itimer_rcu_free(struct rcu_head *head)
{
        struct k_itimer *tmr = container_of(head, struct k_itimer, rcu);

        kmem_cache_free(posix_timers_cache, tmr);
}

static void posix_timer_free(struct k_itimer *tmr)
{
        put_pid(tmr->it_pid);
        sigqueue_free(tmr->sigq);
        call_rcu(&tmr->rcu, k_itimer_rcu_free);
}

static void posix_timer_unhash_and_free(struct k_itimer *tmr)
{
        spin_lock(&hash_lock);
        hlist_del_rcu(&tmr->t_hash);
        spin_unlock(&hash_lock);
        posix_timer_free(tmr);
}

static int common_timer_create(struct k_itimer *new_timer)
{
        hrtimer_init(&new_timer->it.real.timer, new_timer->it_clock, 0);
        return 0;
}

/* Create a POSIX.1b interval timer. */
static int do_timer_create(clockid_t which_clock, struct sigevent *event,
                           timer_t __user *created_timer_id)
{
        const struct k_clock *kc = clockid_to_kclock(which_clock);
        struct k_itimer *new_timer;
        int error, new_timer_id;

        if (!kc)
                return -EINVAL;
        if (!kc->timer_create)
                return -EOPNOTSUPP;

        new_timer = alloc_posix_timer();
        if (unlikely(!new_timer))
                return -EAGAIN;

        spin_lock_init(&new_timer->it_lock);

        /*
         * Add the timer to the hash table. The timer is not yet valid
         * because new_timer::it_signal is still NULL. The timer id is also
         * not yet visible to user space.
         */
        new_timer_id = posix_timer_add(new_timer);
        if (new_timer_id < 0) {
                posix_timer_free(new_timer);
                return new_timer_id;
        }

        new_timer->it_id = (timer_t) new_timer_id;
        new_timer->it_clock = which_clock;
        new_timer->kclock = kc;
        new_timer->it_overrun = -1LL;

        if (event) {
                rcu_read_lock();
                new_timer->it_pid = get_pid(good_sigevent(event));
                rcu_read_unlock();
                if (!new_timer->it_pid) {
                        error = -EINVAL;
                        goto out;
                }
                new_timer->it_sigev_notify     = event->sigev_notify;
                new_timer->sigq->info.si_signo = event->sigev_signo;
                new_timer->sigq->info.si_value = event->sigev_value;
        } else {
                new_timer->it_sigev_notify     = SIGEV_SIGNAL;
                new_timer->sigq->info.si_signo = SIGALRM;
                memset(&new_timer->sigq->info.si_value, 0, sizeof(sigval_t));
                new_timer->sigq->info.si_value.sival_int = new_timer->it_id;
                new_timer->it_pid = get_pid(task_tgid(current));
        }

        new_timer->sigq->info.si_tid   = new_timer->it_id;
        new_timer->sigq->info.si_code  = SI_TIMER;

        if (copy_to_user(created_timer_id, &new_timer_id, sizeof (new_timer_id))) {
                error = -EFAULT;
                goto out;
        }
        /*
         * After succesful copy out, the timer ID is visible to user space
         * now but not yet valid because new_timer::signal is still NULL.
         *
         * Complete the initialization with the clock specific create
         * callback.
         */
        error = kc->timer_create(new_timer);
        if (error)
                goto out;

        spin_lock_irq(&current->sighand->siglock);
        /* This makes the timer valid in the hash table */
        WRITE_ONCE(new_timer->it_signal, current->signal);
        list_add(&new_timer->list, &current->signal->posix_timers);
        spin_unlock_irq(&current->sighand->siglock);
        /*
         * After unlocking sighand::siglock @new_timer is subject to
         * concurrent removal and cannot be touched anymore
         */
        return 0;
out:
        posix_timer_unhash_and_free(new_timer);
        return error;
}

SYSCALL_DEFINE3(timer_create, const clockid_t, which_clock,
                struct sigevent __user *, timer_event_spec,
                timer_t __user *, created_timer_id)
{
        if (timer_event_spec) {
                sigevent_t event;

                if (copy_from_user(&event, timer_event_spec, sizeof (event)))
                        return -EFAULT;
                return do_timer_create(which_clock, &event, created_timer_id);
        }
        return do_timer_create(which_clock, NULL, created_timer_id);
}

#ifdef CONFIG_COMPAT
COMPAT_SYSCALL_DEFINE3(timer_create, clockid_t, which_clock,
                       struct compat_sigevent __user *, timer_event_spec,
                       timer_t __user *, created_timer_id)
{
        if (timer_event_spec) {
                sigevent_t event;

                if (get_compat_sigevent(&event, timer_event_spec))
                        return -EFAULT;
                return do_timer_create(which_clock, &event, created_timer_id);
        }
        return do_timer_create(which_clock, NULL, created_timer_id);
}
#endif

static struct k_itimer *__lock_timer(timer_t timer_id, unsigned long *flags)
{
        struct k_itimer *timr;

        /*
         * timer_t could be any type >= int and we want to make sure any
         * @timer_id outside positive int range fails lookup.
         */
        if ((unsigned long long)timer_id > INT_MAX)
                return NULL;

        /*
         * The hash lookup and the timers are RCU protected.
         *
         * Timers are added to the hash in invalid state where
         * timr::it_signal == NULL. timer::it_signal is only set after the
         * rest of the initialization succeeded.
         *
         * Timer destruction happens in steps:
         *  1) Set timr::it_signal to NULL with timr::it_lock held
         *  2) Release timr::it_lock
         *  3) Remove from the hash under hash_lock
         *  4) Call RCU for removal after the grace period
         *
         * Holding rcu_read_lock() accross the lookup ensures that
         * the timer cannot be freed.
         *
         * The lookup validates locklessly that timr::it_signal ==
         * current::it_signal and timr::it_id == @timer_id. timr::it_id
         * can't change, but timr::it_signal becomes NULL during
         * destruction.
         */
        rcu_read_lock();
        timr = posix_timer_by_id(timer_id);
        if (timr) {
                spin_lock_irqsave(&timr->it_lock, *flags);
                /*
                 * Validate under timr::it_lock that timr::it_signal is
                 * still valid. Pairs with #1 above.
                 */
                if (timr->it_signal == current->signal) {
                        rcu_read_unlock();
                        return timr;
                }
                spin_unlock_irqrestore(&timr->it_lock, *flags);
        }
        rcu_read_unlock();

        return NULL;
}

static ktime_t common_hrtimer_remaining(struct k_itimer *timr, ktime_t now)
{
        struct hrtimer *timer = &timr->it.real.timer;

        return __hrtimer_expires_remaining_adjusted(timer, now);
}

static s64 common_hrtimer_forward(struct k_itimer *timr, ktime_t now)
{
        struct hrtimer *timer = &timr->it.real.timer;

        return hrtimer_forward(timer, now, timr->it_interval);
}

/*
 * Get the time remaining on a POSIX.1b interval timer.
 *
 * Two issues to handle here:
 *
 *  1) The timer has a requeue pending. The return value must appear as
 *     if the timer has been requeued right now.
 *
 *  2) The timer is a SIGEV_NONE timer. These timers are never enqueued
 *     into the hrtimer queue and therefore never expired. Emulate expiry
 *     here taking #1 into account.
 */
void common_timer_get(struct k_itimer *timr, struct itimerspec64 *cur_setting)
{
        const struct k_clock *kc = timr->kclock;
        ktime_t now, remaining, iv;
        bool sig_none;

        sig_none = timr->it_sigev_notify == SIGEV_NONE;
        iv = timr->it_interval;

        /* interval timer ? */
        if (iv) {
                cur_setting->it_interval = ktime_to_timespec64(iv);
        } else if (!timr->it_active) {
                /*
                 * SIGEV_NONE oneshot timers are never queued and therefore
                 * timr->it_active is always false. The check below
                 * vs. remaining time will handle this case.
                 *
                 * For all other timers there is nothing to update here, so
                 * return.
                 */
                if (!sig_none)
                        return;
        }

        now = kc->clock_get_ktime(timr->it_clock);

        /*
         * If this is an interval timer and either has requeue pending or
         * is a SIGEV_NONE timer move the expiry time forward by intervals,
         * so expiry is > now.
         */
        if (iv && (timr->it_requeue_pending & REQUEUE_PENDING || sig_none))
                timr->it_overrun += kc->timer_forward(timr, now);

        remaining = kc->timer_remaining(timr, now);
        /*
         * As @now is retrieved before a possible timer_forward() and
         * cannot be reevaluated by the compiler @remaining is based on the
         * same @now value. Therefore @remaining is consistent vs. @now.
         *
         * Consequently all interval timers, i.e. @iv > 0, cannot have a
         * remaining time <= 0 because timer_forward() guarantees to move
         * them forward so that the next timer expiry is > @now.
         */
        if (remaining <= 0) {
                /*
                 * A single shot SIGEV_NONE timer must return 0, when it is
                 * expired! Timers which have a real signal delivery mode
                 * must return a remaining time greater than 0 because the
                 * signal has not yet been delivered.
                 */
                if (!sig_none)
                        cur_setting->it_value.tv_nsec = 1;
        } else {
                cur_setting->it_value = ktime_to_timespec64(remaining);
        }
}

static int do_timer_gettime(timer_t timer_id,  struct itimerspec64 *setting)
{
        const struct k_clock *kc;
        struct k_itimer *timr;
        unsigned long flags;
        int ret = 0;

        timr = lock_timer(timer_id, &flags);
        if (!timr)
                return -EINVAL;

        memset(setting, 0, sizeof(*setting));
        kc = timr->kclock;
        if (WARN_ON_ONCE(!kc || !kc->timer_get))
                ret = -EINVAL;
        else
                kc->timer_get(timr, setting);

        unlock_timer(timr, flags);
        return ret;
}

/* Get the time remaining on a POSIX.1b interval timer. */
SYSCALL_DEFINE2(timer_gettime, timer_t, timer_id,
                struct __kernel_itimerspec __user *, setting)
{
        struct itimerspec64 cur_setting;

        int ret = do_timer_gettime(timer_id, &cur_setting);
        if (!ret) {
                if (put_itimerspec64(&cur_setting, setting))
                        ret = -EFAULT;
        }
        return ret;
}

#ifdef CONFIG_COMPAT_32BIT_TIME

SYSCALL_DEFINE2(timer_gettime32, timer_t, timer_id,
                struct old_itimerspec32 __user *, setting)
{
        struct itimerspec64 cur_setting;

        int ret = do_timer_gettime(timer_id, &cur_setting);
        if (!ret) {
                if (put_old_itimerspec32(&cur_setting, setting))
                        ret = -EFAULT;
        }
        return ret;
}

#endif

/**
 * sys_timer_getoverrun - Get the number of overruns of a POSIX.1b interval timer
 * @timer_id:   The timer ID which identifies the timer
 *
 * The "overrun count" of a timer is one plus the number of expiration
 * intervals which have elapsed between the first expiry, which queues the
 * signal and the actual signal delivery. On signal delivery the "overrun
 * count" is calculated and cached, so it can be returned directly here.
 *
 * As this is relative to the last queued signal the returned overrun count
 * is meaningless outside of the signal delivery path and even there it
 * does not accurately reflect the current state when user space evaluates
 * it.
 *
 * Returns:
 *      -EINVAL         @timer_id is invalid
 *      1..INT_MAX      The number of overruns related to the last delivered signal
 */
SYSCALL_DEFINE1(timer_getoverrun, timer_t, timer_id)
{
        struct k_itimer *timr;
        unsigned long flags;
        int overrun;

        timr = lock_timer(timer_id, &flags);
        if (!timr)
                return -EINVAL;

        overrun = timer_overrun_to_int(timr, 0);
        unlock_timer(timr, flags);

        return overrun;
}

static void common_hrtimer_arm(struct k_itimer *timr, ktime_t expires,
                               bool absolute, bool sigev_none)
{
        struct hrtimer *timer = &timr->it.real.timer;
        enum hrtimer_mode mode;

        mode = absolute ? HRTIMER_MODE_ABS : HRTIMER_MODE_REL;
        /*
         * Posix magic: Relative CLOCK_REALTIME timers are not affected by
         * clock modifications, so they become CLOCK_MONOTONIC based under the
         * hood. See hrtimer_init(). Update timr->kclock, so the generic
         * functions which use timr->kclock->clock_get_*() work.
         *
         * Note: it_clock stays unmodified, because the next timer_set() might
         * use ABSTIME, so it needs to switch back.
         */
        if (timr->it_clock == CLOCK_REALTIME)
                timr->kclock = absolute ? &clock_realtime : &clock_monotonic;

        hrtimer_init(&timr->it.real.timer, timr->it_clock, mode);
        timr->it.real.timer.function = posix_timer_fn;

        if (!absolute)
                expires = ktime_add_safe(expires, timer->base->get_time());
        hrtimer_set_expires(timer, expires);

        if (!sigev_none)
                hrtimer_start_expires(timer, HRTIMER_MODE_ABS);
}

static int common_hrtimer_try_to_cancel(struct k_itimer *timr)
{
        return hrtimer_try_to_cancel(&timr->it.real.timer);
}

static void common_timer_wait_running(struct k_itimer *timer)
{
        hrtimer_cancel_wait_running(&timer->it.real.timer);
}

/*
 * On PREEMPT_RT this prevents priority inversion and a potential livelock
 * against the ksoftirqd thread in case that ksoftirqd gets preempted while
 * executing a hrtimer callback.
 *
 * See the comments in hrtimer_cancel_wait_running(). For PREEMPT_RT=n this
 * just results in a cpu_relax().
 *
 * For POSIX CPU timers with CONFIG_POSIX_CPU_TIMERS_TASK_WORK=n this is
 * just a cpu_relax(). With CONFIG_POSIX_CPU_TIMERS_TASK_WORK=y this
 * prevents spinning on an eventually scheduled out task and a livelock
 * when the task which tries to delete or disarm the timer has preempted
 * the task which runs the expiry in task work context.
 */
static struct k_itimer *timer_wait_running(struct k_itimer *timer,
                                           unsigned long *flags)
{
        const struct k_clock *kc = READ_ONCE(timer->kclock);
        timer_t timer_id = READ_ONCE(timer->it_id);

        /* Prevent kfree(timer) after dropping the lock */
        rcu_read_lock();
        unlock_timer(timer, *flags);

        /*
         * kc->timer_wait_running() might drop RCU lock. So @timer
         * cannot be touched anymore after the function returns!
         */
        if (!WARN_ON_ONCE(!kc->timer_wait_running))
                kc->timer_wait_running(timer);

        rcu_read_unlock();
        /* Relock the timer. It might be not longer hashed. */
        return lock_timer(timer_id, flags);
}

/* Set a POSIX.1b interval timer. */
int common_timer_set(struct k_itimer *timr, int flags,
                     struct itimerspec64 *new_setting,
                     struct itimerspec64 *old_setting)
{
        const struct k_clock *kc = timr->kclock;
        bool sigev_none;
        ktime_t expires;

        if (old_setting)
                common_timer_get(timr, old_setting);

        /* Prevent rearming by clearing the interval */
        timr->it_interval = 0;
        /*
         * Careful here. On SMP systems the timer expiry function could be
         * active and spinning on timr->it_lock.
         */
        if (kc->timer_try_to_cancel(timr) < 0)
                return TIMER_RETRY;

        timr->it_active = 0;
        timr->it_requeue_pending = (timr->it_requeue_pending + 2) &
                ~REQUEUE_PENDING;
        timr->it_overrun_last = 0;

        /* Switch off the timer when it_value is zero */
        if (!new_setting->it_value.tv_sec && !new_setting->it_value.tv_nsec)
                return 0;

        timr->it_interval = timespec64_to_ktime(new_setting->it_interval);
        expires = timespec64_to_ktime(new_setting->it_value);
        if (flags & TIMER_ABSTIME)
                expires = timens_ktime_to_host(timr->it_clock, expires);
        sigev_none = timr->it_sigev_notify == SIGEV_NONE;

        kc->timer_arm(timr, expires, flags & TIMER_ABSTIME, sigev_none);
        timr->it_active = !sigev_none;
        return 0;
}

static int do_timer_settime(timer_t timer_id, int tmr_flags,
                            struct itimerspec64 *new_spec64,
                            struct itimerspec64 *old_spec64)
{
        const struct k_clock *kc;
        struct k_itimer *timr;
        unsigned long flags;
        int error = 0;

        if (!timespec64_valid(&new_spec64->it_interval) ||
            !timespec64_valid(&new_spec64->it_value))
                return -EINVAL;

        if (old_spec64)
                memset(old_spec64, 0, sizeof(*old_spec64));

        timr = lock_timer(timer_id, &flags);
retry:
        if (!timr)
                return -EINVAL;

        kc = timr->kclock;
        if (WARN_ON_ONCE(!kc || !kc->timer_set))
                error = -EINVAL;
        else
                error = kc->timer_set(timr, tmr_flags, new_spec64, old_spec64);

        if (error == TIMER_RETRY) {
                // We already got the old time...
                old_spec64 = NULL;
                /* Unlocks and relocks the timer if it still exists */
                timr = timer_wait_running(timr, &flags);
                goto retry;
        }
        unlock_timer(timr, flags);

        return error;
}

/* Set a POSIX.1b interval timer */
SYSCALL_DEFINE4(timer_settime, timer_t, timer_id, int, flags,
                const struct __kernel_itimerspec __user *, new_setting,
                struct __kernel_itimerspec __user *, old_setting)
{
        struct itimerspec64 new_spec, old_spec, *rtn;
        int error = 0;

        if (!new_setting)
                return -EINVAL;

        if (get_itimerspec64(&new_spec, new_setting))
                return -EFAULT;

        rtn = old_setting ? &old_spec : NULL;
        error = do_timer_settime(timer_id, flags, &new_spec, rtn);
        if (!error && old_setting) {
                if (put_itimerspec64(&old_spec, old_setting))
                        error = -EFAULT;
        }
        return error;
}

#ifdef CONFIG_COMPAT_32BIT_TIME
SYSCALL_DEFINE4(timer_settime32, timer_t, timer_id, int, flags,
                struct old_itimerspec32 __user *, new,
                struct old_itimerspec32 __user *, old)
{
        struct itimerspec64 new_spec, old_spec;
        struct itimerspec64 *rtn = old ? &old_spec : NULL;
        int error = 0;

        if (!new)
                return -EINVAL;
        if (get_old_itimerspec32(&new_spec, new))
                return -EFAULT;

        error = do_timer_settime(timer_id, flags, &new_spec, rtn);
        if (!error && old) {
                if (put_old_itimerspec32(&old_spec, old))
                        error = -EFAULT;
        }
        return error;
}
#endif

int common_timer_del(struct k_itimer *timer)
{
        const struct k_clock *kc = timer->kclock;

        timer->it_interval = 0;
        if (kc->timer_try_to_cancel(timer) < 0)
                return TIMER_RETRY;
        timer->it_active = 0;
        return 0;
}

static inline int timer_delete_hook(struct k_itimer *timer)
{
        const struct k_clock *kc = timer->kclock;

        if (WARN_ON_ONCE(!kc || !kc->timer_del))
                return -EINVAL;
        return kc->timer_del(timer);
}

/* Delete a POSIX.1b interval timer. */
SYSCALL_DEFINE1(timer_delete, timer_t, timer_id)
{
        struct k_itimer *timer;
        unsigned long flags;

        timer = lock_timer(timer_id, &flags);

retry_delete:
        if (!timer)
                return -EINVAL;

        if (unlikely(timer_delete_hook(timer) == TIMER_RETRY)) {
                /* Unlocks and relocks the timer if it still exists */
                timer = timer_wait_running(timer, &flags);
                goto retry_delete;
        }

        spin_lock(&current->sighand->siglock);
        list_del(&timer->list);
        spin_unlock(&current->sighand->siglock);
        /*
         * A concurrent lookup could check timer::it_signal lockless. It
         * will reevaluate with timer::it_lock held and observe the NULL.
         */
        WRITE_ONCE(timer->it_signal, NULL);

        unlock_timer(timer, flags);
        posix_timer_unhash_and_free(timer);
        return 0;
}

/*
 * Delete a timer if it is armed, remove it from the hash and schedule it
 * for RCU freeing.
 */
static void itimer_delete(struct k_itimer *timer)
{
        unsigned long flags;

        /*
         * irqsave is required to make timer_wait_running() work.
         */
        spin_lock_irqsave(&timer->it_lock, flags);

retry_delete:
        /*
         * Even if the timer is not longer accessible from other tasks
         * it still might be armed and queued in the underlying timer
         * mechanism. Worse, that timer mechanism might run the expiry
         * function concurrently.
         */
        if (timer_delete_hook(timer) == TIMER_RETRY) {
                /*
                 * Timer is expired concurrently, prevent livelocks
                 * and pointless spinning on RT.
                 *
                 * timer_wait_running() drops timer::it_lock, which opens
                 * the possibility for another task to delete the timer.
                 *
                 * That's not possible here because this is invoked from
                 * do_exit() only for the last thread of the thread group.
                 * So no other task can access and delete that timer.
                 */
                if (WARN_ON_ONCE(timer_wait_running(timer, &flags) != timer))
                        return;

                goto retry_delete;
        }
        list_del(&timer->list);

        /*
         * Setting timer::it_signal to NULL is technically not required
         * here as nothing can access the timer anymore legitimately via
         * the hash table. Set it to NULL nevertheless so that all deletion
         * paths are consistent.
         */
        WRITE_ONCE(timer->it_signal, NULL);

        spin_unlock_irqrestore(&timer->it_lock, flags);
        posix_timer_unhash_and_free(timer);
}

/*
 * Invoked from do_exit() when the last thread of a thread group exits.
 * At that point no other task can access the timers of the dying
 * task anymore.
 */
void exit_itimers(struct task_struct *tsk)
{
        struct list_head timers;
        struct k_itimer *tmr;

        if (list_empty(&tsk->signal->posix_timers))
                return;

        /* Protect against concurrent read via /proc/$PID/timers */
        spin_lock_irq(&tsk->sighand->siglock);
        list_replace_init(&tsk->signal->posix_timers, &timers);
        spin_unlock_irq(&tsk->sighand->siglock);

        /* The timers are not longer accessible via tsk::signal */
        while (!list_empty(&timers)) {
                tmr = list_first_entry(&timers, struct k_itimer, list);
                itimer_delete(tmr);
        }
}

SYSCALL_DEFINE2(clock_settime, const clockid_t, which_clock,
                const struct __kernel_timespec __user *, tp)
{
        const struct k_clock *kc = clockid_to_kclock(which_clock);
        struct timespec64 new_tp;

        if (!kc || !kc->clock_set)
                return -EINVAL;

        if (get_timespec64(&new_tp, tp))
                return -EFAULT;

        /*
         * Permission checks have to be done inside the clock specific
         * setter callback.
         */
        return kc->clock_set(which_clock, &new_tp);
}

SYSCALL_DEFINE2(clock_gettime, const clockid_t, which_clock,
                struct __kernel_timespec __user *, tp)
{
        const struct k_clock *kc = clockid_to_kclock(which_clock);
        struct timespec64 kernel_tp;
        int error;

        if (!kc)
                return -EINVAL;

        error = kc->clock_get_timespec(which_clock, &kernel_tp);

        if (!error && put_timespec64(&kernel_tp, tp))
                error = -EFAULT;

        return error;
}

int do_clock_adjtime(const clockid_t which_clock, struct __kernel_timex * ktx)
{
        const struct k_clock *kc = clockid_to_kclock(which_clock);

        if (!kc)
                return -EINVAL;
        if (!kc->clock_adj)
                return -EOPNOTSUPP;

        return kc->clock_adj(which_clock, ktx);
}

SYSCALL_DEFINE2(clock_adjtime, const clockid_t, which_clock,
                struct __kernel_timex __user *, utx)
{
        struct __kernel_timex ktx;
        int err;

        if (copy_from_user(&ktx, utx, sizeof(ktx)))
                return -EFAULT;

        err = do_clock_adjtime(which_clock, &ktx);

        if (err >= 0 && copy_to_user(utx, &ktx, sizeof(ktx)))
                return -EFAULT;

        return err;
}

/**
 * sys_clock_getres - Get the resolution of a clock
 * @which_clock:        The clock to get the resolution for
 * @tp:                 Pointer to a a user space timespec64 for storage
 *
 * POSIX defines:
 *
 * "The clock_getres() function shall return the resolution of any
 * clock. Clock resolutions are implementation-defined and cannot be set by
 * a process. If the argument res is not NULL, the resolution of the
 * specified clock shall be stored in the location pointed to by res. If
 * res is NULL, the clock resolution is not returned. If the time argument
 * of clock_settime() is not a multiple of res, then the value is truncated
 * to a multiple of res."
 *
 * Due to the various hardware constraints the real resolution can vary
 * wildly and even change during runtime when the underlying devices are
 * replaced. The kernel also can use hardware devices with different
 * resolutions for reading the time and for arming timers.
 *
 * The kernel therefore deviates from the POSIX spec in various aspects:
 *
 * 1) The resolution returned to user space
 *
 *    For CLOCK_REALTIME, CLOCK_MONOTONIC, CLOCK_BOOTTIME, CLOCK_TAI,
 *    CLOCK_REALTIME_ALARM, CLOCK_BOOTTIME_ALAREM and CLOCK_MONOTONIC_RAW
 *    the kernel differentiates only two cases:
 *
 *    I)  Low resolution mode:
 *
 *        When high resolution timers are disabled at compile or runtime
 *        the resolution returned is nanoseconds per tick, which represents
 *        the precision at which timers expire.
 *
 *    II) High resolution mode:
 *
 *        When high resolution timers are enabled the resolution returned
 *        is always one nanosecond independent of the actual resolution of
 *        the underlying hardware devices.
 *
 *        For CLOCK_*_ALARM the actual resolution depends on system
 *        state. When system is running the resolution is the same as the
 *        resolution of the other clocks. During suspend the actual
 *        resolution is the resolution of the underlying RTC device which
 *        might be way less precise than the clockevent device used during
 *        running state.
 *
 *   For CLOCK_REALTIME_COARSE and CLOCK_MONOTONIC_COARSE the resolution
 *   returned is always nanoseconds per tick.
 *
 *   For CLOCK_PROCESS_CPUTIME and CLOCK_THREAD_CPUTIME the resolution
 *   returned is always one nanosecond under the assumption that the
 *   underlying scheduler clock has a better resolution than nanoseconds
 *   per tick.
 *
 *   For dynamic POSIX clocks (PTP devices) the resolution returned is
 *   always one nanosecond.
 *
 * 2) Affect on sys_clock_settime()
 *
 *    The kernel does not truncate the time which is handed in to
 *    sys_clock_settime(). The kernel internal timekeeping is always using
 *    nanoseconds precision independent of the clocksource device which is
 *    used to read the time from. The resolution of that device only
 *    affects the presicion of the time returned by sys_clock_gettime().
 *
 * Returns:
 *      0               Success. @tp contains the resolution
 *      -EINVAL         @which_clock is not a valid clock ID
 *      -EFAULT         Copying the resolution to @tp faulted
 *      -ENODEV         Dynamic POSIX clock is not backed by a device
 *      -EOPNOTSUPP     Dynamic POSIX clock does not support getres()
 */
SYSCALL_DEFINE2(clock_getres, const clockid_t, which_clock,
                struct __kernel_timespec __user *, tp)
{
        const struct k_clock *kc = clockid_to_kclock(which_clock);
        struct timespec64 rtn_tp;
        int error;

        if (!kc)
                return -EINVAL;

        error = kc->clock_getres(which_clock, &rtn_tp);

        if (!error && tp && put_timespec64(&rtn_tp, tp))
                error = -EFAULT;

        return error;
}

#ifdef CONFIG_COMPAT_32BIT_TIME

SYSCALL_DEFINE2(clock_settime32, clockid_t, which_clock,
                struct old_timespec32 __user *, tp)
{
        const struct k_clock *kc = clockid_to_kclock(which_clock);
        struct timespec64 ts;

        if (!kc || !kc->clock_set)
                return -EINVAL;

        if (get_old_timespec32(&ts, tp))
                return -EFAULT;

        return kc->clock_set(which_clock, &ts);
}

SYSCALL_DEFINE2(clock_gettime32, clockid_t, which_clock,
                struct old_timespec32 __user *, tp)
{
        const struct k_clock *kc = clockid_to_kclock(which_clock);
        struct timespec64 ts;
        int err;

        if (!kc)
                return -EINVAL;

        err = kc->clock_get_timespec(which_clock, &ts);

        if (!err && put_old_timespec32(&ts, tp))
                err = -EFAULT;

        return err;
}

SYSCALL_DEFINE2(clock_adjtime32, clockid_t, which_clock,
                struct old_timex32 __user *, utp)
{
        struct __kernel_timex ktx;
        int err;

        err = get_old_timex32(&ktx, utp);
        if (err)
                return err;

        err = do_clock_adjtime(which_clock, &ktx);

        if (err >= 0 && put_old_timex32(utp, &ktx))
                return -EFAULT;

        return err;
}

SYSCALL_DEFINE2(clock_getres_time32, clockid_t, which_clock,
                struct old_timespec32 __user *, tp)
{
        const struct k_clock *kc = clockid_to_kclock(which_clock);
        struct timespec64 ts;
        int err;

        if (!kc)
                return -EINVAL;

        err = kc->clock_getres(which_clock, &ts);
        if (!err && tp && put_old_timespec32(&ts, tp))
                return -EFAULT;

        return err;
}

#endif

/*
 * sys_clock_nanosleep() for CLOCK_REALTIME and CLOCK_TAI
 */
static int common_nsleep(const clockid_t which_clock, int flags,
                         const struct timespec64 *rqtp)
{
        ktime_t texp = timespec64_to_ktime(*rqtp);

        return hrtimer_nanosleep(texp, flags & TIMER_ABSTIME ?
                                 HRTIMER_MODE_ABS : HRTIMER_MODE_REL,
                                 which_clock);
}

/*
 * sys_clock_nanosleep() for CLOCK_MONOTONIC and CLOCK_BOOTTIME
 *
 * Absolute nanosleeps for these clocks are time-namespace adjusted.
 */
static int common_nsleep_timens(const clockid_t which_clock, int flags,
                                const struct timespec64 *rqtp)
{
        ktime_t texp = timespec64_to_ktime(*rqtp);

        if (flags & TIMER_ABSTIME)
                texp = timens_ktime_to_host(which_clock, texp);

        return hrtimer_nanosleep(texp, flags & TIMER_ABSTIME ?
                                 HRTIMER_MODE_ABS : HRTIMER_MODE_REL,
                                 which_clock);
}

SYSCALL_DEFINE4(clock_nanosleep, const clockid_t, which_clock, int, flags,
                const struct __kernel_timespec __user *, rqtp,
                struct __kernel_timespec __user *, rmtp)
{
        const struct k_clock *kc = clockid_to_kclock(which_clock);
        struct timespec64 t;

        if (!kc)
                return -EINVAL;
        if (!kc->nsleep)
                return -EOPNOTSUPP;

        if (get_timespec64(&t, rqtp))
                return -EFAULT;

        if (!timespec64_valid(&t))
                return -EINVAL;
        if (flags & TIMER_ABSTIME)
                rmtp = NULL;
        current->restart_block.fn = do_no_restart_syscall;
        current->restart_block.nanosleep.type = rmtp ? TT_NATIVE : TT_NONE;
        current->restart_block.nanosleep.rmtp = rmtp;

        return kc->nsleep(which_clock, flags, &t);
}

#ifdef CONFIG_COMPAT_32BIT_TIME

SYSCALL_DEFINE4(clock_nanosleep_time32, clockid_t, which_clock, int, flags,
                struct old_timespec32 __user *, rqtp,
                struct old_timespec32 __user *, rmtp)
{
        const struct k_clock *kc = clockid_to_kclock(which_clock);
        struct timespec64 t;

        if (!kc)
                return -EINVAL;
        if (!kc->nsleep)
                return -EOPNOTSUPP;

        if (get_old_timespec32(&t, rqtp))
                return -EFAULT;

        if (!timespec64_valid(&t))
                return -EINVAL;
        if (flags & TIMER_ABSTIME)
                rmtp = NULL;
        current->restart_block.fn = do_no_restart_syscall;
        current->restart_block.nanosleep.type = rmtp ? TT_COMPAT : TT_NONE;
        current->restart_block.nanosleep.compat_rmtp = rmtp;

        return kc->nsleep(which_clock, flags, &t);
}

#endif

static const struct k_clock clock_realtime = {
        .clock_getres           = posix_get_hrtimer_res,
        .clock_get_timespec     = posix_get_realtime_timespec,
        .clock_get_ktime        = posix_get_realtime_ktime,
        .clock_set              = posix_clock_realtime_set,
        .clock_adj              = posix_clock_realtime_adj,
        .nsleep                 = common_nsleep,
        .timer_create           = common_timer_create,
        .timer_set              = common_timer_set,
        .timer_get              = common_timer_get,
        .timer_del              = common_timer_del,
        .timer_rearm            = common_hrtimer_rearm,
        .timer_forward          = common_hrtimer_forward,
        .timer_remaining        = common_hrtimer_remaining,
        .timer_try_to_cancel    = common_hrtimer_try_to_cancel,
        .timer_wait_running     = common_timer_wait_running,
        .timer_arm              = common_hrtimer_arm,
};

static const struct k_clock clock_monotonic = {
        .clock_getres           = posix_get_hrtimer_res,
        .clock_get_timespec     = posix_get_monotonic_timespec,
        .clock_get_ktime        = posix_get_monotonic_ktime,
        .nsleep                 = common_nsleep_timens,
        .timer_create           = common_timer_create,
        .timer_set              = common_timer_set,
        .timer_get              = common_timer_get,
        .timer_del              = common_timer_del,
        .timer_rearm            = common_hrtimer_rearm,
        .timer_forward          = common_hrtimer_forward,
        .timer_remaining        = common_hrtimer_remaining,
        .timer_try_to_cancel    = common_hrtimer_try_to_cancel,
        .timer_wait_running     = common_timer_wait_running,
        .timer_arm              = common_hrtimer_arm,
};

static const struct k_clock clock_monotonic_raw = {
        .clock_getres           = posix_get_hrtimer_res,
        .clock_get_timespec     = posix_get_monotonic_raw,
};

static const struct k_clock clock_realtime_coarse = {
        .clock_getres           = posix_get_coarse_res,
        .clock_get_timespec     = posix_get_realtime_coarse,
};

static const struct k_clock clock_monotonic_coarse = {
        .clock_getres           = posix_get_coarse_res,
        .clock_get_timespec     = posix_get_monotonic_coarse,
};

static const struct k_clock clock_tai = {
        .clock_getres           = posix_get_hrtimer_res,
        .clock_get_ktime        = posix_get_tai_ktime,
        .clock_get_timespec     = posix_get_tai_timespec,
        .nsleep                 = common_nsleep,
        .timer_create           = common_timer_create,
        .timer_set              = common_timer_set,
        .timer_get              = common_timer_get,
        .timer_del              = common_timer_del,
        .timer_rearm            = common_hrtimer_rearm,
        .timer_forward          = common_hrtimer_forward,
        .timer_remaining        = common_hrtimer_remaining,
        .timer_try_to_cancel    = common_hrtimer_try_to_cancel,
        .timer_wait_running     = common_timer_wait_running,
        .timer_arm              = common_hrtimer_arm,
};

static const struct k_clock clock_boottime = {
        .clock_getres           = posix_get_hrtimer_res,
        .clock_get_ktime        = posix_get_boottime_ktime,
        .clock_get_timespec     = posix_get_boottime_timespec,
        .nsleep                 = common_nsleep_timens,
        .timer_create           = common_timer_create,
        .timer_set              = common_timer_set,
        .timer_get              = common_timer_get,
        .timer_del              = common_timer_del,
        .timer_rearm            = common_hrtimer_rearm,
        .timer_forward          = common_hrtimer_forward,
        .timer_remaining        = common_hrtimer_remaining,
        .timer_try_to_cancel    = common_hrtimer_try_to_cancel,
        .timer_wait_running     = common_timer_wait_running,
        .timer_arm              = common_hrtimer_arm,
};

static const struct k_clock * const posix_clocks[] = {
        [CLOCK_REALTIME]                = &clock_realtime,
        [CLOCK_MONOTONIC]               = &clock_monotonic,
        [CLOCK_PROCESS_CPUTIME_ID]      = &clock_process,
        [CLOCK_THREAD_CPUTIME_ID]       = &clock_thread,
        [CLOCK_MONOTONIC_RAW]           = &clock_monotonic_raw,
        [CLOCK_REALTIME_COARSE]         = &clock_realtime_coarse,
        [CLOCK_MONOTONIC_COARSE]        = &clock_monotonic_coarse,
        [CLOCK_BOOTTIME]                = &clock_boottime,
        [CLOCK_REALTIME_ALARM]          = &alarm_clock,
        [CLOCK_BOOTTIME_ALARM]          = &alarm_clock,
        [CLOCK_TAI]                     = &clock_tai,
};

static const struct k_clock *clockid_to_kclock(const clockid_t id)
{
        clockid_t idx = id;

        if (id < 0) {
                return (id & CLOCKFD_MASK) == CLOCKFD ?
                        &clock_posix_dynamic : &clock_posix_cpu;
        }

        if (id >= ARRAY_SIZE(posix_clocks))
                return NULL;

        return posix_clocks[array_index_nospec(idx, ARRAY_SIZE(posix_clocks))];
}