// 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 #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #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. */ struct timer_hash_bucket { spinlock_t lock; struct hlist_head head; }; static struct { struct timer_hash_bucket *buckets; unsigned long mask; } __timer_data __ro_after_init __aligned(2*sizeof(long)); #define timer_buckets (__timer_data.buckets) #define timer_hashmask (__timer_data.mask) 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; #define TIMER_ANY_ID INT_MIN /* 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); #define lock_timer(tid) \ ({ struct k_itimer *__timr; \ __cond_lock(&__timr->it_lock, __timr = __lock_timer(tid)); \ __timr; \ }) static inline void unlock_timer(struct k_itimer *timr) { if (likely((timr))) spin_unlock_irq(&timr->it_lock); } #define scoped_timer_get_or_fail(_id) \ scoped_cond_guard(lock_timer, return -EINVAL, _id) #define scoped_timer (scope) DEFINE_CLASS(lock_timer, struct k_itimer *, unlock_timer(_T), __lock_timer(id), timer_t id); DEFINE_CLASS_IS_COND_GUARD(lock_timer); static struct timer_hash_bucket *hash_bucket(struct signal_struct *sig, unsigned int nr) { return &timer_buckets[jhash2((u32 *)&sig, sizeof(sig) / sizeof(u32), nr) & timer_hashmask]; } static struct k_itimer *posix_timer_by_id(timer_t id) { struct signal_struct *sig = current->signal; struct timer_hash_bucket *bucket = hash_bucket(sig, id); struct k_itimer *timer; hlist_for_each_entry_rcu(timer, &bucket->head, t_hash) { /* timer->it_signal can be set concurrently */ if ((READ_ONCE(timer->it_signal) == sig) && (timer->it_id == id)) return timer; } return NULL; } static inline struct signal_struct *posix_sig_owner(const struct k_itimer *timer) { unsigned long val = (unsigned long)timer->it_signal; /* * Mask out bit 0, which acts as invalid marker to prevent * posix_timer_by_id() detecting it as valid. */ return (struct signal_struct *)(val & ~1UL); } static bool posix_timer_hashed(struct timer_hash_bucket *bucket, struct signal_struct *sig, timer_t id) { struct hlist_head *head = &bucket->head; struct k_itimer *timer; hlist_for_each_entry_rcu(timer, head, t_hash, lockdep_is_held(&bucket->lock)) { if ((posix_sig_owner(timer) == sig) && (timer->it_id == id)) return true; } return false; } static bool posix_timer_add_at(struct k_itimer *timer, struct signal_struct *sig, unsigned int id) { struct timer_hash_bucket *bucket = hash_bucket(sig, id); scoped_guard (spinlock, &bucket->lock) { /* * Validate under the lock as this could have raced against * another thread ending up with the same ID, which is * highly unlikely, but possible. */ if (!posix_timer_hashed(bucket, sig, id)) { /* * Set the timer ID and the signal pointer to make * it identifiable in the hash table. The signal * pointer has bit 0 set to indicate that it is not * yet fully initialized. posix_timer_hashed() * masks this bit out, but the syscall lookup fails * to match due to it being set. This guarantees * that there can't be duplicate timer IDs handed * out. */ timer->it_id = (timer_t)id; timer->it_signal = (struct signal_struct *)((unsigned long)sig | 1UL); hlist_add_head_rcu(&timer->t_hash, &bucket->head); return true; } } return false; } static int posix_timer_add(struct k_itimer *timer, int req_id) { struct signal_struct *sig = current->signal; if (unlikely(req_id != TIMER_ANY_ID)) { if (!posix_timer_add_at(timer, sig, req_id)) return -EBUSY; /* * Move the ID counter past the requested ID, so that after * switching back to normal mode the IDs are outside of the * exact allocated region. That avoids ID collisions on the * next regular timer_create() invocations. */ atomic_set(&sig->next_posix_timer_id, req_id + 1); return req_id; } for (unsigned int cnt = 0; cnt <= INT_MAX; cnt++) { /* Get the next timer ID and clamp it to positive space */ unsigned int id = atomic_fetch_inc(&sig->next_posix_timer_id) & INT_MAX; if (posix_timer_add_at(timer, sig, id)) return id; cond_resched(); } /* POSIX return code when no timer ID could be allocated */ return -EAGAIN; } 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), __alignof__(struct k_itimer), 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) { if (timr->it_overrun_last > (s64)INT_MAX) return INT_MAX; return (int)timr->it_overrun_last; } 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); } static bool __posixtimer_deliver_signal(struct kernel_siginfo *info, struct k_itimer *timr) { guard(spinlock)(&timr->it_lock); /* * Check if the timer is still alive or whether it got modified * since the signal was queued. In either case, don't rearm and * drop the signal. */ if (timr->it_signal_seq != timr->it_sigqueue_seq || WARN_ON_ONCE(!posixtimer_valid(timr))) return false; if (!timr->it_interval || WARN_ON_ONCE(timr->it_status != POSIX_TIMER_REQUEUE_PENDING)) return true; timr->kclock->timer_rearm(timr); timr->it_status = POSIX_TIMER_ARMED; timr->it_overrun_last = timr->it_overrun; timr->it_overrun = -1LL; ++timr->it_signal_seq; info->si_overrun = timer_overrun_to_int(timr); return true; } /* * This function is called from the signal delivery code. It decides * whether the signal should be dropped and rearms interval timers. The * timer can be unconditionally accessed as there is a reference held on * it. */ bool posixtimer_deliver_signal(struct kernel_siginfo *info, struct sigqueue *timer_sigq) { struct k_itimer *timr = container_of(timer_sigq, struct k_itimer, sigq); bool ret; /* * Release siglock to ensure proper locking order versus * timr::it_lock. Keep interrupts disabled. */ spin_unlock(¤t->sighand->siglock); ret = __posixtimer_deliver_signal(info, timr); /* Drop the reference which was acquired when the signal was queued */ posixtimer_putref(timr); spin_lock(¤t->sighand->siglock); return ret; } void posix_timer_queue_signal(struct k_itimer *timr) { lockdep_assert_held(&timr->it_lock); if (!posixtimer_valid(timr)) return; timr->it_status = timr->it_interval ? POSIX_TIMER_REQUEUE_PENDING : POSIX_TIMER_DISARMED; posixtimer_send_sigqueue(timr); } /* * 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) { struct k_itimer *timr = container_of(timer, struct k_itimer, it.real.timer); guard(spinlock_irqsave)(&timr->it_lock); posix_timer_queue_signal(timr); return HRTIMER_NORESTART; } long posixtimer_create_prctl(unsigned long ctrl) { switch (ctrl) { case PR_TIMER_CREATE_RESTORE_IDS_OFF: current->signal->timer_create_restore_ids = 0; return 0; case PR_TIMER_CREATE_RESTORE_IDS_ON: current->signal->timer_create_restore_ids = 1; return 0; case PR_TIMER_CREATE_RESTORE_IDS_GET: return current->signal->timer_create_restore_ids; } return -EINVAL; } 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; if (unlikely(!posix_timers_cache)) return NULL; tmr = kmem_cache_zalloc(posix_timers_cache, GFP_KERNEL); if (!tmr) return tmr; if (unlikely(!posixtimer_init_sigqueue(&tmr->sigq))) { kmem_cache_free(posix_timers_cache, tmr); return NULL; } rcuref_init(&tmr->rcuref, 1); return tmr; } void posixtimer_free_timer(struct k_itimer *tmr) { put_pid(tmr->it_pid); if (tmr->sigq.ucounts) dec_rlimit_put_ucounts(tmr->sigq.ucounts, UCOUNT_RLIMIT_SIGPENDING); kfree_rcu(tmr, rcu); } static void posix_timer_unhash_and_free(struct k_itimer *tmr) { struct timer_hash_bucket *bucket = hash_bucket(posix_sig_owner(tmr), tmr->it_id); scoped_guard (spinlock, &bucket->lock) hlist_del_rcu(&tmr->t_hash); posixtimer_putref(tmr); } static int common_timer_create(struct k_itimer *new_timer) { hrtimer_setup(&new_timer->it.real.timer, posix_timer_fn, 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); timer_t req_id = TIMER_ANY_ID; 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); /* Special case for CRIU to restore timers with a given timer ID. */ if (unlikely(current->signal->timer_create_restore_ids)) { if (copy_from_user(&req_id, created_timer_id, sizeof(req_id))) return -EFAULT; /* Valid IDs are 0..INT_MAX */ if ((unsigned int)req_id > INT_MAX) return -EINVAL; } /* * Add the timer to the hash table. The timer is not yet valid * after insertion, but has a unique ID allocated. */ new_timer_id = posix_timer_add(new_timer, req_id); if (new_timer_id < 0) { posixtimer_free_timer(new_timer); return new_timer_id; } new_timer->it_clock = which_clock; new_timer->kclock = kc; new_timer->it_overrun = -1LL; if (event) { scoped_guard (rcu) new_timer->it_pid = get_pid(good_sigevent(event)); 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; new_timer->sigq.info.si_value.sival_int = new_timer->it_id; new_timer->it_pid = get_pid(task_tgid(current)); } if (new_timer->it_sigev_notify & SIGEV_THREAD_ID) new_timer->it_pid_type = PIDTYPE_PID; else new_timer->it_pid_type = PIDTYPE_TGID; 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 low order bit is 1. * * Complete the initialization with the clock specific create * callback. */ error = kc->timer_create(new_timer); if (error) goto out; /* * timer::it_lock ensures that __lock_timer() observes a fully * initialized timer when it observes a valid timer::it_signal. * * sighand::siglock is required to protect signal::posix_timers. */ scoped_guard (spinlock_irq, &new_timer->it_lock) { guard(spinlock)(¤t->sighand->siglock); /* * new_timer::it_signal contains the signal pointer with * bit 0 set, which makes it invalid for syscall operations. * Store the unmodified signal pointer to make it valid. */ WRITE_ONCE(new_timer->it_signal, current->signal); hlist_add_head_rcu(&new_timer->list, ¤t->signal->posix_timers); } /* * After unlocking @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) { 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 is marked invalid. timer::it_signal is only set * after the rest of the initialization succeeded. * * Timer destruction happens in steps: * 1) Set timr::it_signal marked invalid with timr::it_lock held * 2) Release timr::it_lock * 3) Remove from the hash under hash_lock * 4) Put the reference count. * * The reference count might not drop to zero if timr::sigq is * queued. In that case the signal delivery or flush will put the * last reference count. * * When the reference count reaches zero, the timer is scheduled * for RCU removal after the grace period. * * Holding rcu_read_lock() across 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 can become invalid during * destruction, which makes the locked check fail. */ guard(rcu)(); timr = posix_timer_by_id(timer_id); if (timr) { spin_lock_irq(&timr->it_lock); /* * Validate under timr::it_lock that timr::it_signal is * still valid. Pairs with #1 above. */ if (timr->it_signal == current->signal) return timr; spin_unlock_irq(&timr->it_lock); } 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_status == POSIX_TIMER_DISARMED) { /* * SIGEV_NONE oneshot timers are never queued and therefore * timr->it_status is always DISARMED. 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_status != POSIX_TIMER_ARMED) 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) { memset(setting, 0, sizeof(*setting)); scoped_timer_get_or_fail(timer_id) scoped_timer->kclock->timer_get(scoped_timer, setting); return 0; } /* 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) { scoped_timer_get_or_fail(timer_id) return timer_overrun_to_int(scoped_timer); } 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_setup(). 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_setup(&timr->it.real.timer, posix_timer_fn, timr->it_clock, mode); 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 void timer_wait_running(struct k_itimer *timer) { /* * kc->timer_wait_running() might drop RCU lock. So @timer * cannot be touched anymore after the function returns! */ timer->kclock->timer_wait_running(timer); } /* * Set up the new interval and reset the signal delivery data */ void posix_timer_set_common(struct k_itimer *timer, struct itimerspec64 *new_setting) { if (new_setting->it_value.tv_sec || new_setting->it_value.tv_nsec) timer->it_interval = timespec64_to_ktime(new_setting->it_interval); else timer->it_interval = 0; /* Reset overrun accounting */ timer->it_overrun_last = 0; timer->it_overrun = -1LL; } /* 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); /* * 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_status = POSIX_TIMER_DISARMED; posix_timer_set_common(timr, new_setting); /* Keep timer disarmed when it_value is zero */ if (!new_setting->it_value.tv_sec && !new_setting->it_value.tv_nsec) return 0; 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); if (!sigev_none) timr->it_status = POSIX_TIMER_ARMED; return 0; } static int do_timer_settime(timer_t timer_id, int tmr_flags, struct itimerspec64 *new_spec64, struct itimerspec64 *old_spec64) { 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)); for (; ; old_spec64 = NULL) { struct k_itimer *timr; scoped_timer_get_or_fail(timer_id) { timr = scoped_timer; if (old_spec64) old_spec64->it_interval = ktime_to_timespec64(timr->it_interval); /* Prevent signal delivery and rearming. */ timr->it_signal_seq++; int ret = timr->kclock->timer_set(timr, tmr_flags, new_spec64, old_spec64); if (ret != TIMER_RETRY) return ret; /* Protect the timer from being freed when leaving the lock scope */ rcu_read_lock(); } timer_wait_running(timr); rcu_read_unlock(); } } /* 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; if (kc->timer_try_to_cancel(timer) < 0) return TIMER_RETRY; timer->it_status = POSIX_TIMER_DISARMED; return 0; } /* * If the deleted timer is on the ignored list, remove it and * drop the associated reference. */ static inline void posix_timer_cleanup_ignored(struct k_itimer *tmr) { if (!hlist_unhashed(&tmr->ignored_list)) { hlist_del_init(&tmr->ignored_list); posixtimer_putref(tmr); } } static void posix_timer_delete(struct k_itimer *timer) { /* * Invalidate the timer, remove it from the linked list and remove * it from the ignored list if pending. * * The invalidation must be written with siglock held so that the * signal code observes the invalidated timer::it_signal in * do_sigaction(), which prevents it from moving a pending signal * of a deleted timer to the ignore list. * * The invalidation also prevents signal queueing, signal delivery * and therefore rearming from the signal delivery path. * * A concurrent lookup can still find the timer in the hash, but it * will check timer::it_signal with timer::it_lock held and observe * bit 0 set, which invalidates it. That also prevents the timer ID * from being handed out before this timer is completely gone. */ timer->it_signal_seq++; scoped_guard (spinlock, ¤t->sighand->siglock) { unsigned long sig = (unsigned long)timer->it_signal | 1UL; WRITE_ONCE(timer->it_signal, (struct signal_struct *)sig); hlist_del_rcu(&timer->list); posix_timer_cleanup_ignored(timer); } while (timer->kclock->timer_del(timer) == TIMER_RETRY) { guard(rcu)(); spin_unlock_irq(&timer->it_lock); timer_wait_running(timer); spin_lock_irq(&timer->it_lock); } } /* Delete a POSIX.1b interval timer. */ SYSCALL_DEFINE1(timer_delete, timer_t, timer_id) { struct k_itimer *timer; scoped_timer_get_or_fail(timer_id) { timer = scoped_timer; posix_timer_delete(timer); } /* Remove it from the hash, which frees up the timer ID */ posix_timer_unhash_and_free(timer); return 0; } /* * 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 hlist_head timers; struct hlist_node *next; struct k_itimer *timer; /* Clear restore mode for exec() */ tsk->signal->timer_create_restore_ids = 0; if (hlist_empty(&tsk->signal->posix_timers)) return; /* Protect against concurrent read via /proc/$PID/timers */ scoped_guard (spinlock_irq, &tsk->sighand->siglock) hlist_move_list(&tsk->signal->posix_timers, &timers); /* The timers are not longer accessible via tsk::signal */ hlist_for_each_entry_safe(timer, next, &timers, list) { scoped_guard (spinlock_irq, &timer->it_lock) posix_timer_delete(timer); posix_timer_unhash_and_free(timer); cond_resched(); } /* * There should be no timers on the ignored list. itimer_delete() has * mopped them up. */ if (!WARN_ON_ONCE(!hlist_empty(&tsk->signal->ignored_posix_timers))) return; hlist_move_list(&tsk->signal->ignored_posix_timers, &timers); while (!hlist_empty(&timers)) { posix_timer_cleanup_ignored(hlist_entry(timers.first, struct k_itimer, ignored_list)); } } 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))]; } static int __init posixtimer_init(void) { unsigned long i, size; unsigned int shift; if (IS_ENABLED(CONFIG_BASE_SMALL)) size = 512; else size = roundup_pow_of_two(512 * num_possible_cpus()); timer_buckets = alloc_large_system_hash("posixtimers", sizeof(*timer_buckets), size, 0, 0, &shift, NULL, size, size); size = 1UL << shift; timer_hashmask = size - 1; for (i = 0; i < size; i++) { spin_lock_init(&timer_buckets[i].lock); INIT_HLIST_HEAD(&timer_buckets[i].head); } return 0; } core_initcall(posixtimer_init);