path: root/kernel/time/posix-timers.c

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

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

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

static struct kmem_cache *posix_timers_cache;

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

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

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

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

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

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

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

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

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

	return __posix_timers_find(head, sig, id);
}

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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