kernel/time/itimer.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0
 /*
  * linux/kernel/itimer.c
  *
  * Copyright (C) 1992 Darren Senn
  */

 /* These are all the functions necessary to implement itimers */

 #include <linux/mm.h>
 #include <linux/interrupt.h>
 #include <linux/syscalls.h>
 #include <linux/time.h>
 #include <linux/sched/signal.h>
 #include <linux/sched/cputime.h>
 #include <linux/posix-timers.h>
 #include <linux/hrtimer.h>
 #include <trace/events/timer.h>
 #include <linux/compat.h>

 #include <linux/uaccess.h>

 /**
  * itimer_get_remtime - get remaining time for the timer
  *
  * @timer: the timer to read
  *
  * Returns the delta between the expiry time and now, which can be
  * less than zero or 1usec for an pending expired timer
  */
 static struct timeval itimer_get_remtime(struct hrtimer *timer)
 {
 	ktime_t rem = __hrtimer_get_remaining(timer, true);

 	/*
 	 * Racy but safe: if the itimer expires after the above
 	 * hrtimer_get_remtime() call but before this condition
 	 * then we return 0 - which is correct.
 	 */
 	if (hrtimer_active(timer)) {
 		if (rem <= 0)
 			rem = NSEC_PER_USEC;
 	} else
 		rem = 0;

 	return ktime_to_timeval(rem);
 }

 static void get_cpu_itimer(struct task_struct *tsk, unsigned int clock_id,
 			   struct itimerval *const value)
 {
 	u64 val, interval;
 	struct cpu_itimer *it = &tsk->signal->it[clock_id];

 	spin_lock_irq(&tsk->sighand->siglock);

 	val = it->expires;
 	interval = it->incr;
 	if (val) {
 		struct task_cputime cputime;
 		u64 t;

 		thread_group_cputimer(tsk, &cputime);
 		if (clock_id == CPUCLOCK_PROF)
 			t = cputime.utime + cputime.stime;
 		else
 			/* CPUCLOCK_VIRT */
 			t = cputime.utime;

 		if (val < t)
 			/* about to fire */
 			val = TICK_NSEC;
 		else
 			val -= t;
 	}

 	spin_unlock_irq(&tsk->sighand->siglock);

 	value->it_value = ns_to_timeval(val);
 	value->it_interval = ns_to_timeval(interval);
 }

 int do_getitimer(int which, struct itimerval *value)
 {
 	struct task_struct *tsk = current;

 	switch (which) {
 	case ITIMER_REAL:
 		spin_lock_irq(&tsk->sighand->siglock);
 		value->it_value = itimer_get_remtime(&tsk->signal->real_timer);
 		value->it_interval =
 			ktime_to_timeval(tsk->signal->it_real_incr);
 		spin_unlock_irq(&tsk->sighand->siglock);
 		break;
 	case ITIMER_VIRTUAL:
 		get_cpu_itimer(tsk, CPUCLOCK_VIRT, value);
 		break;
 	case ITIMER_PROF:
 		get_cpu_itimer(tsk, CPUCLOCK_PROF, value);
 		break;
 	default:
 		return(-EINVAL);
 	}
 	return 0;
 }

 SYSCALL_DEFINE2(getitimer, int, which, struct itimerval __user *, value)
 {
 	int error = -EFAULT;
 	struct itimerval get_buffer;

 	if (value) {
 		error = do_getitimer(which, &get_buffer);
 		if (!error &&
 		    copy_to_user(value, &get_buffer, sizeof(get_buffer)))
 			error = -EFAULT;
 	}
 	return error;
 }

 #ifdef CONFIG_COMPAT
 COMPAT_SYSCALL_DEFINE2(getitimer, int, which,
 		       struct compat_itimerval __user *, it)
 {
 	struct itimerval kit;
 	int error = do_getitimer(which, &kit);

 	if (!error && put_compat_itimerval(it, &kit))
 		error = -EFAULT;
 	return error;
 }
 #endif


 /*
  * The timer is automagically restarted, when interval != 0
  */
 enum hrtimer_restart it_real_fn(struct hrtimer *timer)
 {
 	struct signal_struct *sig =
 		container_of(timer, struct signal_struct, real_timer);
 	struct pid *leader_pid = sig->pids[PIDTYPE_TGID];

 	trace_itimer_expire(ITIMER_REAL, leader_pid, 0);
 	kill_pid_info(SIGALRM, SEND_SIG_PRIV, leader_pid);

 	return HRTIMER_NORESTART;
 }

 static void set_cpu_itimer(struct task_struct *tsk, unsigned int clock_id,
 			   const struct itimerval *const value,
 			   struct itimerval *const ovalue)
 {
 	u64 oval, nval, ointerval, ninterval;
 	struct cpu_itimer *it = &tsk->signal->it[clock_id];

 	/*
 	 * Use the to_ktime conversion because that clamps the maximum
 	 * value to KTIME_MAX and avoid multiplication overflows.
 	 */
 	nval = ktime_to_ns(timeval_to_ktime(value->it_value));
 	ninterval = ktime_to_ns(timeval_to_ktime(value->it_interval));

 	spin_lock_irq(&tsk->sighand->siglock);

 	oval = it->expires;
 	ointerval = it->incr;
 	if (oval || nval) {
 		if (nval > 0)
 			nval += TICK_NSEC;
 		set_process_cpu_timer(tsk, clock_id, &nval, &oval);
 	}
 	it->expires = nval;
 	it->incr = ninterval;
 	trace_itimer_state(clock_id == CPUCLOCK_VIRT ?
 			   ITIMER_VIRTUAL : ITIMER_PROF, value, nval);

 	spin_unlock_irq(&tsk->sighand->siglock);

 	if (ovalue) {
 		ovalue->it_value = ns_to_timeval(oval);
 		ovalue->it_interval = ns_to_timeval(ointerval);
 	}
 }

 /*
  * Returns true if the timeval is in canonical form
  */
 #define timeval_valid(t) \
 	(((t)->tv_sec >= 0) && (((unsigned long) (t)->tv_usec) < USEC_PER_SEC))

 int do_setitimer(int which, struct itimerval *value, struct itimerval *ovalue)
 {
 	struct task_struct *tsk = current;
 	struct hrtimer *timer;
 	ktime_t expires;

 	/*
 	 * Validate the timevals in value.
 	 */
 	if (!timeval_valid(&value->it_value) ||
 	    !timeval_valid(&value->it_interval))
 		return -EINVAL;

 	switch (which) {
 	case ITIMER_REAL:
 again:
 		spin_lock_irq(&tsk->sighand->siglock);
 		timer = &tsk->signal->real_timer;
 		if (ovalue) {
 			ovalue->it_value = itimer_get_remtime(timer);
 			ovalue->it_interval
 				= ktime_to_timeval(tsk->signal->it_real_incr);
 		}
 		/* We are sharing ->siglock with it_real_fn() */
 		if (hrtimer_try_to_cancel(timer) < 0) {
 			spin_unlock_irq(&tsk->sighand->siglock);
 			goto again;
 		}
 		expires = timeval_to_ktime(value->it_value);
 		if (expires != 0) {
 			tsk->signal->it_real_incr =
 				timeval_to_ktime(value->it_interval);
 			hrtimer_start(timer, expires, HRTIMER_MODE_REL);
 		} else
 			tsk->signal->it_real_incr = 0;

 		trace_itimer_state(ITIMER_REAL, value, 0);
 		spin_unlock_irq(&tsk->sighand->siglock);
 		break;
 	case ITIMER_VIRTUAL:
 		set_cpu_itimer(tsk, CPUCLOCK_VIRT, value, ovalue);
 		break;
 	case ITIMER_PROF:
 		set_cpu_itimer(tsk, CPUCLOCK_PROF, value, ovalue);
 		break;
 	default:
 		return -EINVAL;
 	}
 	return 0;
 }

 #ifdef __ARCH_WANT_SYS_ALARM

 /**
  * alarm_setitimer - set alarm in seconds
  *
  * @seconds:	number of seconds until alarm
  *		0 disables the alarm
  *
  * Returns the remaining time in seconds of a pending timer or 0 when
  * the timer is not active.
  *
  * On 32 bit machines the seconds value is limited to (INT_MAX/2) to avoid
  * negative timeval settings which would cause immediate expiry.
  */
 static unsigned int alarm_setitimer(unsigned int seconds)
 {
 	struct itimerval it_new, it_old;

 #if BITS_PER_LONG < 64
 	if (seconds > INT_MAX)
 		seconds = INT_MAX;
 #endif
 	it_new.it_value.tv_sec = seconds;
 	it_new.it_value.tv_usec = 0;
 	it_new.it_interval.tv_sec = it_new.it_interval.tv_usec = 0;

 	do_setitimer(ITIMER_REAL, &it_new, &it_old);

 	/*
 	 * We can't return 0 if we have an alarm pending ...  And we'd
 	 * better return too much than too little anyway
 	 */
 	if ((!it_old.it_value.tv_sec && it_old.it_value.tv_usec) ||
 	      it_old.it_value.tv_usec >= 500000)
 		it_old.it_value.tv_sec++;

 	return it_old.it_value.tv_sec;
 }

 /*
  * For backwards compatibility?  This can be done in libc so Alpha
  * and all newer ports shouldn't need it.
  */
 SYSCALL_DEFINE1(alarm, unsigned int, seconds)
 {
 	return alarm_setitimer(seconds);
 }

 #endif

 SYSCALL_DEFINE3(setitimer, int, which, struct itimerval __user *, value,
 		struct itimerval __user *, ovalue)
 {
 	struct itimerval set_buffer, get_buffer;
 	int error;

 	if (value) {
 		if(copy_from_user(&set_buffer, value, sizeof(set_buffer)))
 			return -EFAULT;
 	} else {
 		memset(&set_buffer, 0, sizeof(set_buffer));
 		printk_once(KERN_WARNING "%s calls setitimer() with new_value NULL pointer."
 			    " Misfeature support will be removed\n",
 			    current->comm);
 	}

 	error = do_setitimer(which, &set_buffer, ovalue ? &get_buffer : NULL);
 	if (error || !ovalue)
 		return error;

 	if (copy_to_user(ovalue, &get_buffer, sizeof(get_buffer)))
 		return -EFAULT;
 	return 0;
 }

 #ifdef CONFIG_COMPAT
 COMPAT_SYSCALL_DEFINE3(setitimer, int, which,
 		       struct compat_itimerval __user *, in,
 		       struct compat_itimerval __user *, out)
 {
 	struct itimerval kin, kout;
 	int error;

 	if (in) {
 		if (get_compat_itimerval(&kin, in))
 			return -EFAULT;
 	} else {
 		memset(&kin, 0, sizeof(kin));
 	}

 	error = do_setitimer(which, &kin, out ? &kout : NULL);
 	if (error || !out)
 		return error;
 	if (put_compat_itimerval(out, &kout))
 		return -EFAULT;
 	return 0;
 }
 #endif
	// SPDX-License-Identifier: GPL-2.0
	/*
	* linux/kernel/itimer.c
	*
	* Copyright (C) 1992 Darren Senn
	*/

	/* These are all the functions necessary to implement itimers */

	#include <linux/mm.h>
	#include <linux/interrupt.h>
	#include <linux/syscalls.h>
	#include <linux/time.h>
	#include <linux/sched/signal.h>
	#include <linux/sched/cputime.h>
	#include <linux/posix-timers.h>
	#include <linux/hrtimer.h>
	#include <trace/events/timer.h>
	#include <linux/compat.h>

	#include <linux/uaccess.h>

	/**
	* itimer_get_remtime - get remaining time for the timer
	*
	* @timer: the timer to read
	*
	* Returns the delta between the expiry time and now, which can be
	* less than zero or 1usec for an pending expired timer
	*/
	static struct timeval itimer_get_remtime(struct hrtimer *timer)
	{
	ktime_t rem = __hrtimer_get_remaining(timer, true);

	/*
	* Racy but safe: if the itimer expires after the above
	* hrtimer_get_remtime() call but before this condition
	* then we return 0 - which is correct.
	*/
	if (hrtimer_active(timer)) {
	if (rem <= 0)
	rem = NSEC_PER_USEC;
	} else
	rem = 0;

	return ktime_to_timeval(rem);
	}

	static void get_cpu_itimer(struct task_struct *tsk, unsigned int clock_id,
	struct itimerval *const value)
	{
	u64 val, interval;
	struct cpu_itimer *it = &tsk->signal->it[clock_id];

	spin_lock_irq(&tsk->sighand->siglock);

	val = it->expires;
	interval = it->incr;
	if (val) {
	struct task_cputime cputime;
	u64 t;

	thread_group_cputimer(tsk, &cputime);
	if (clock_id == CPUCLOCK_PROF)
	t = cputime.utime + cputime.stime;
	else
	/* CPUCLOCK_VIRT */
	t = cputime.utime;

	if (val < t)
	/* about to fire */
	val = TICK_NSEC;
	else
	val -= t;
	}

	spin_unlock_irq(&tsk->sighand->siglock);

	value->it_value = ns_to_timeval(val);
	value->it_interval = ns_to_timeval(interval);
	}

	int do_getitimer(int which, struct itimerval *value)
	{
	struct task_struct *tsk = current;

	switch (which) {
	case ITIMER_REAL:
	spin_lock_irq(&tsk->sighand->siglock);
	value->it_value = itimer_get_remtime(&tsk->signal->real_timer);
	value->it_interval =
	ktime_to_timeval(tsk->signal->it_real_incr);
	spin_unlock_irq(&tsk->sighand->siglock);
	break;
	case ITIMER_VIRTUAL:
	get_cpu_itimer(tsk, CPUCLOCK_VIRT, value);
	break;
	case ITIMER_PROF:
	get_cpu_itimer(tsk, CPUCLOCK_PROF, value);
	break;
	default:
	return(-EINVAL);
	}
	return 0;
	}

	SYSCALL_DEFINE2(getitimer, int, which, struct itimerval __user *, value)
	{
	int error = -EFAULT;
	struct itimerval get_buffer;

	if (value) {
	error = do_getitimer(which, &get_buffer);
	if (!error &&
	copy_to_user(value, &get_buffer, sizeof(get_buffer)))
	error = -EFAULT;
	}
	return error;
	}

	#ifdef CONFIG_COMPAT
	COMPAT_SYSCALL_DEFINE2(getitimer, int, which,
	struct compat_itimerval __user *, it)
	{
	struct itimerval kit;
	int error = do_getitimer(which, &kit);

	if (!error && put_compat_itimerval(it, &kit))
	error = -EFAULT;
	return error;
	}
	#endif


	/*
	* The timer is automagically restarted, when interval != 0
	*/
	enum hrtimer_restart it_real_fn(struct hrtimer *timer)
	{
	struct signal_struct *sig =
	container_of(timer, struct signal_struct, real_timer);
	struct pid *leader_pid = sig->pids[PIDTYPE_TGID];

	trace_itimer_expire(ITIMER_REAL, leader_pid, 0);
	kill_pid_info(SIGALRM, SEND_SIG_PRIV, leader_pid);

	return HRTIMER_NORESTART;
	}

	static void set_cpu_itimer(struct task_struct *tsk, unsigned int clock_id,
	const struct itimerval *const value,
	struct itimerval *const ovalue)
	{
	u64 oval, nval, ointerval, ninterval;
	struct cpu_itimer *it = &tsk->signal->it[clock_id];

	/*
	* Use the to_ktime conversion because that clamps the maximum
	* value to KTIME_MAX and avoid multiplication overflows.
	*/
	nval = ktime_to_ns(timeval_to_ktime(value->it_value));
	ninterval = ktime_to_ns(timeval_to_ktime(value->it_interval));

	spin_lock_irq(&tsk->sighand->siglock);

	oval = it->expires;
	ointerval = it->incr;
	if (oval \|\| nval) {
	if (nval > 0)
	nval += TICK_NSEC;
	set_process_cpu_timer(tsk, clock_id, &nval, &oval);
	}
	it->expires = nval;
	it->incr = ninterval;
	trace_itimer_state(clock_id == CPUCLOCK_VIRT ?
	ITIMER_VIRTUAL : ITIMER_PROF, value, nval);

	spin_unlock_irq(&tsk->sighand->siglock);

	if (ovalue) {
	ovalue->it_value = ns_to_timeval(oval);
	ovalue->it_interval = ns_to_timeval(ointerval);
	}
	}

	/*
	* Returns true if the timeval is in canonical form
	*/
	#define timeval_valid(t) \
	(((t)->tv_sec >= 0) && (((unsigned long) (t)->tv_usec) < USEC_PER_SEC))

	int do_setitimer(int which, struct itimerval value, struct itimerval ovalue)
	{
	struct task_struct *tsk = current;
	struct hrtimer *timer;
	ktime_t expires;

	/*
	* Validate the timevals in value.
	*/
	if (!timeval_valid(&value->it_value) \|\|
	!timeval_valid(&value->it_interval))
	return -EINVAL;

	switch (which) {
	case ITIMER_REAL:
	again:
	spin_lock_irq(&tsk->sighand->siglock);
	timer = &tsk->signal->real_timer;
	if (ovalue) {
	ovalue->it_value = itimer_get_remtime(timer);
	ovalue->it_interval
	= ktime_to_timeval(tsk->signal->it_real_incr);
	}
	/* We are sharing ->siglock with it_real_fn() */
	if (hrtimer_try_to_cancel(timer) < 0) {
	spin_unlock_irq(&tsk->sighand->siglock);
	goto again;
	}
	expires = timeval_to_ktime(value->it_value);
	if (expires != 0) {
	tsk->signal->it_real_incr =
	timeval_to_ktime(value->it_interval);
	hrtimer_start(timer, expires, HRTIMER_MODE_REL);
	} else
	tsk->signal->it_real_incr = 0;

	trace_itimer_state(ITIMER_REAL, value, 0);
	spin_unlock_irq(&tsk->sighand->siglock);
	break;
	case ITIMER_VIRTUAL:
	set_cpu_itimer(tsk, CPUCLOCK_VIRT, value, ovalue);
	break;
	case ITIMER_PROF:
	set_cpu_itimer(tsk, CPUCLOCK_PROF, value, ovalue);
	break;
	default:
	return -EINVAL;
	}
	return 0;
	}

	#ifdef __ARCH_WANT_SYS_ALARM

	/**
	* alarm_setitimer - set alarm in seconds
	*
	* @seconds: number of seconds until alarm
	* 0 disables the alarm
	*
	* Returns the remaining time in seconds of a pending timer or 0 when
	* the timer is not active.
	*
	* On 32 bit machines the seconds value is limited to (INT_MAX/2) to avoid
	* negative timeval settings which would cause immediate expiry.
	*/
	static unsigned int alarm_setitimer(unsigned int seconds)
	{
	struct itimerval it_new, it_old;

	#if BITS_PER_LONG < 64
	if (seconds > INT_MAX)
	seconds = INT_MAX;
	#endif
	it_new.it_value.tv_sec = seconds;
	it_new.it_value.tv_usec = 0;
	it_new.it_interval.tv_sec = it_new.it_interval.tv_usec = 0;

	do_setitimer(ITIMER_REAL, &it_new, &it_old);

	/*
	* We can't return 0 if we have an alarm pending ... And we'd
	* better return too much than too little anyway
	*/
	if ((!it_old.it_value.tv_sec && it_old.it_value.tv_usec) \|\|
	it_old.it_value.tv_usec >= 500000)
	it_old.it_value.tv_sec++;

	return it_old.it_value.tv_sec;
	}

	/*
	* For backwards compatibility? This can be done in libc so Alpha
	* and all newer ports shouldn't need it.
	*/
	SYSCALL_DEFINE1(alarm, unsigned int, seconds)
	{
	return alarm_setitimer(seconds);
	}

	#endif

	SYSCALL_DEFINE3(setitimer, int, which, struct itimerval __user *, value,
	struct itimerval __user *, ovalue)
	{
	struct itimerval set_buffer, get_buffer;
	int error;

	if (value) {
	if(copy_from_user(&set_buffer, value, sizeof(set_buffer)))
	return -EFAULT;
	} else {
	memset(&set_buffer, 0, sizeof(set_buffer));
	printk_once(KERN_WARNING "%s calls setitimer() with new_value NULL pointer."
	" Misfeature support will be removed\n",
	current->comm);
	}

	error = do_setitimer(which, &set_buffer, ovalue ? &get_buffer : NULL);
	if (error \|\| !ovalue)
	return error;

	if (copy_to_user(ovalue, &get_buffer, sizeof(get_buffer)))
	return -EFAULT;
	return 0;
	}

	#ifdef CONFIG_COMPAT
	COMPAT_SYSCALL_DEFINE3(setitimer, int, which,
	struct compat_itimerval __user *, in,
	struct compat_itimerval __user *, out)
	{
	struct itimerval kin, kout;
	int error;

	if (in) {
	if (get_compat_itimerval(&kin, in))
	return -EFAULT;
	} else {
	memset(&kin, 0, sizeof(kin));
	}

	error = do_setitimer(which, &kin, out ? &kout : NULL);
	if (error \|\| !out)
	return error;
	if (put_compat_itimerval(out, &kout))
	return -EFAULT;
	return 0;
	}
	#endif