// SPDX-License-Identifier: GPL-2.0+
/*
* 2002-10-15 Posix Clocks & timers
* by George Anzinger [email protected]
* 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_queue_signal(struct k_itimer *timr)
{
int ret, si_private = 0;
enum pid_type type;
lockdep_assert_held(&timr->it_lock);
timr->it_active = 0;
if (timr->it_interval)
si_private = ++timr->it_requeue_pending;
/*
* 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)
{
struct k_itimer *timr = container_of(timer, struct k_itimer, it.real.timer);
enum hrtimer_restart ret = HRTIMER_NORESTART;
unsigned long flags;
spin_lock_irqsave(&timr->it_lock, flags);
if (posix_timer_queue_signal(timr)) {
/*
* 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
* jiffy expire every jiffy 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 jiffy 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);
hlist_add_head(&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 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;
/* Prevent reloading in case there is a signal pending */
timer->it_requeue_pending = (timer->it_requeue_pending + 2) & ~REQUEUE_PENDING;
/* 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);
/* 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;
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);
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;
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;
if (old_spec64)
old_spec64->it_interval = ktime_to_timespec64(timr->it_interval);
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);
hlist_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;
}
hlist_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 hlist_head timers;
if (hlist_empty(&tsk->signal->posix_timers))
return;
/* Protect against concurrent read via /proc/$PID/timers */
spin_lock_irq(&tsk->sighand->siglock);
hlist_move_list(&tsk->signal->posix_timers, &timers);
spin_unlock_irq(&tsk->sighand->siglock);
/* The timers are not longer accessible via tsk::signal */
while (!hlist_empty(&timers))
itimer_delete(hlist_entry(timers.first, struct k_itimer, 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))];
}
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