diff options
Diffstat (limited to 'kernel/time/posix-timers.c')
| -rw-r--r-- | kernel/time/posix-timers.c | 1541 |
1 files changed, 1541 insertions, 0 deletions
diff --git a/kernel/time/posix-timers.c b/kernel/time/posix-timers.c new file mode 100644 index 0000000000..b924f0f096 --- /dev/null +++ b/kernel/time/posix-timers.c @@ -0,0 +1,1541 @@ +// 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(¤t->sighand->siglock); + /* This makes the timer valid in the hash table */ + WRITE_ONCE(new_timer->it_signal, current->signal); + list_add(&new_timer->list, ¤t->signal->posix_timers); + spin_unlock_irq(¤t->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(¤t->sighand->siglock); + list_del(&timer->list); + spin_unlock(¤t->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))]; +} |