1// SPDX-License-Identifier: GPL-2.0
  2/*
  3 * linux/kernel/itimer.c
  4 *
  5 * Copyright (C) 1992 Darren Senn
  6 */
  7
  8/* These are all the functions necessary to implement itimers */
  9
 10#include <linux/mm.h>
 11#include <linux/interrupt.h>
 12#include <linux/syscalls.h>
 13#include <linux/time.h>
 14#include <linux/sched/signal.h>
 15#include <linux/sched/cputime.h>
 16#include <linux/posix-timers.h>
 17#include <linux/hrtimer.h>
 18#include <trace/events/timer.h>
 19#include <linux/compat.h>
 20
 21#include <linux/uaccess.h>
 22
 23/**
 24 * itimer_get_remtime - get remaining time for the timer
 25 *
 26 * @timer: the timer to read
 27 *
 28 * Returns the delta between the expiry time and now, which can be
 29 * less than zero or 1usec for an pending expired timer
 30 */
 31static struct timeval itimer_get_remtime(struct hrtimer *timer)
 32{
 33	ktime_t rem = __hrtimer_get_remaining(timer, true);
 34
 35	/*
 36	 * Racy but safe: if the itimer expires after the above
 37	 * hrtimer_get_remtime() call but before this condition
 38	 * then we return 0 - which is correct.
 39	 */
 40	if (hrtimer_active(timer)) {
 41		if (rem <= 0)
 42			rem = NSEC_PER_USEC;
 43	} else
 44		rem = 0;
 45
 46	return ktime_to_timeval(rem);
 47}
 48
 49static void get_cpu_itimer(struct task_struct *tsk, unsigned int clock_id,
 50			   struct itimerval *const value)
 51{
 52	u64 val, interval;
 53	struct cpu_itimer *it = &tsk->signal->it[clock_id];
 54
 55	spin_lock_irq(&tsk->sighand->siglock);
 56
 57	val = it->expires;
 58	interval = it->incr;
 59	if (val) {
 60		struct task_cputime cputime;
 61		u64 t;
 62
 63		thread_group_cputimer(tsk, &cputime);
 64		if (clock_id == CPUCLOCK_PROF)
 65			t = cputime.utime + cputime.stime;
 66		else
 67			/* CPUCLOCK_VIRT */
 68			t = cputime.utime;
 69
 70		if (val < t)
 71			/* about to fire */
 72			val = TICK_NSEC;
 73		else
 74			val -= t;
 75	}
 76
 77	spin_unlock_irq(&tsk->sighand->siglock);
 78
 79	value->it_value = ns_to_timeval(val);
 80	value->it_interval = ns_to_timeval(interval);
 81}
 82
 83int do_getitimer(int which, struct itimerval *value)
 84{
 85	struct task_struct *tsk = current;
 86
 87	switch (which) {
 88	case ITIMER_REAL:
 89		spin_lock_irq(&tsk->sighand->siglock);
 90		value->it_value = itimer_get_remtime(&tsk->signal->real_timer);
 91		value->it_interval =
 92			ktime_to_timeval(tsk->signal->it_real_incr);
 93		spin_unlock_irq(&tsk->sighand->siglock);
 94		break;
 95	case ITIMER_VIRTUAL:
 96		get_cpu_itimer(tsk, CPUCLOCK_VIRT, value);
 97		break;
 98	case ITIMER_PROF:
 99		get_cpu_itimer(tsk, CPUCLOCK_PROF, value);
100		break;
101	default:
102		return(-EINVAL);
103	}
104	return 0;
105}
106
107SYSCALL_DEFINE2(getitimer, int, which, struct itimerval __user *, value)
108{
109	int error = -EFAULT;
110	struct itimerval get_buffer;
111
112	if (value) {
113		error = do_getitimer(which, &get_buffer);
114		if (!error &&
115		    copy_to_user(value, &get_buffer, sizeof(get_buffer)))
116			error = -EFAULT;
117	}
118	return error;
119}
120
121#ifdef CONFIG_COMPAT
122COMPAT_SYSCALL_DEFINE2(getitimer, int, which,
123		       struct compat_itimerval __user *, it)
124{
125	struct itimerval kit;
126	int error = do_getitimer(which, &kit);
127
128	if (!error && put_compat_itimerval(it, &kit))
129		error = -EFAULT;
130	return error;
131}
132#endif
133
134
135/*
136 * The timer is automagically restarted, when interval != 0
137 */
138enum hrtimer_restart it_real_fn(struct hrtimer *timer)
139{
140	struct signal_struct *sig =
141		container_of(timer, struct signal_struct, real_timer);
142
143	trace_itimer_expire(ITIMER_REAL, sig->leader_pid, 0);
144	kill_pid_info(SIGALRM, SEND_SIG_PRIV, sig->leader_pid);
145
146	return HRTIMER_NORESTART;
147}
148
149static void set_cpu_itimer(struct task_struct *tsk, unsigned int clock_id,
150			   const struct itimerval *const value,
151			   struct itimerval *const ovalue)
152{
153	u64 oval, nval, ointerval, ninterval;
154	struct cpu_itimer *it = &tsk->signal->it[clock_id];
155
156	/*
157	 * Use the to_ktime conversion because that clamps the maximum
158	 * value to KTIME_MAX and avoid multiplication overflows.
159	 */
160	nval = ktime_to_ns(timeval_to_ktime(value->it_value));
161	ninterval = ktime_to_ns(timeval_to_ktime(value->it_interval));
162
163	spin_lock_irq(&tsk->sighand->siglock);
164
165	oval = it->expires;
166	ointerval = it->incr;
167	if (oval || nval) {
168		if (nval > 0)
169			nval += TICK_NSEC;
170		set_process_cpu_timer(tsk, clock_id, &nval, &oval);
171	}
172	it->expires = nval;
173	it->incr = ninterval;
174	trace_itimer_state(clock_id == CPUCLOCK_VIRT ?
175			   ITIMER_VIRTUAL : ITIMER_PROF, value, nval);
176
177	spin_unlock_irq(&tsk->sighand->siglock);
178
179	if (ovalue) {
180		ovalue->it_value = ns_to_timeval(oval);
181		ovalue->it_interval = ns_to_timeval(ointerval);
182	}
183}
184
185/*
186 * Returns true if the timeval is in canonical form
187 */
188#define timeval_valid(t) \
189	(((t)->tv_sec >= 0) && (((unsigned long) (t)->tv_usec) < USEC_PER_SEC))
190
191int do_setitimer(int which, struct itimerval *value, struct itimerval *ovalue)
192{
193	struct task_struct *tsk = current;
194	struct hrtimer *timer;
195	ktime_t expires;
196
197	/*
198	 * Validate the timevals in value.
199	 */
200	if (!timeval_valid(&value->it_value) ||
201	    !timeval_valid(&value->it_interval))
202		return -EINVAL;
203
204	switch (which) {
205	case ITIMER_REAL:
206again:
207		spin_lock_irq(&tsk->sighand->siglock);
208		timer = &tsk->signal->real_timer;
209		if (ovalue) {
210			ovalue->it_value = itimer_get_remtime(timer);
211			ovalue->it_interval
212				= ktime_to_timeval(tsk->signal->it_real_incr);
213		}
214		/* We are sharing ->siglock with it_real_fn() */
215		if (hrtimer_try_to_cancel(timer) < 0) {
216			spin_unlock_irq(&tsk->sighand->siglock);
217			goto again;
218		}
219		expires = timeval_to_ktime(value->it_value);
220		if (expires != 0) {
221			tsk->signal->it_real_incr =
222				timeval_to_ktime(value->it_interval);
223			hrtimer_start(timer, expires, HRTIMER_MODE_REL);
224		} else
225			tsk->signal->it_real_incr = 0;
226
227		trace_itimer_state(ITIMER_REAL, value, 0);
228		spin_unlock_irq(&tsk->sighand->siglock);
229		break;
230	case ITIMER_VIRTUAL:
231		set_cpu_itimer(tsk, CPUCLOCK_VIRT, value, ovalue);
232		break;
233	case ITIMER_PROF:
234		set_cpu_itimer(tsk, CPUCLOCK_PROF, value, ovalue);
235		break;
236	default:
237		return -EINVAL;
238	}
239	return 0;
240}
241
242#ifdef __ARCH_WANT_SYS_ALARM
243
244/**
245 * alarm_setitimer - set alarm in seconds
246 *
247 * @seconds:	number of seconds until alarm
248 *		0 disables the alarm
249 *
250 * Returns the remaining time in seconds of a pending timer or 0 when
251 * the timer is not active.
252 *
253 * On 32 bit machines the seconds value is limited to (INT_MAX/2) to avoid
254 * negative timeval settings which would cause immediate expiry.
255 */
256static unsigned int alarm_setitimer(unsigned int seconds)
257{
258	struct itimerval it_new, it_old;
259
260#if BITS_PER_LONG < 64
261	if (seconds > INT_MAX)
262		seconds = INT_MAX;
263#endif
264	it_new.it_value.tv_sec = seconds;
265	it_new.it_value.tv_usec = 0;
266	it_new.it_interval.tv_sec = it_new.it_interval.tv_usec = 0;
267
268	do_setitimer(ITIMER_REAL, &it_new, &it_old);
269
270	/*
271	 * We can't return 0 if we have an alarm pending ...  And we'd
272	 * better return too much than too little anyway
273	 */
274	if ((!it_old.it_value.tv_sec && it_old.it_value.tv_usec) ||
275	      it_old.it_value.tv_usec >= 500000)
276		it_old.it_value.tv_sec++;
277
278	return it_old.it_value.tv_sec;
279}
280
281/*
282 * For backwards compatibility?  This can be done in libc so Alpha
283 * and all newer ports shouldn't need it.
284 */
285SYSCALL_DEFINE1(alarm, unsigned int, seconds)
286{
287	return alarm_setitimer(seconds);
288}
289
290#endif
291
292SYSCALL_DEFINE3(setitimer, int, which, struct itimerval __user *, value,
293		struct itimerval __user *, ovalue)
294{
295	struct itimerval set_buffer, get_buffer;
296	int error;
297
298	if (value) {
299		if(copy_from_user(&set_buffer, value, sizeof(set_buffer)))
300			return -EFAULT;
301	} else {
302		memset(&set_buffer, 0, sizeof(set_buffer));
303		printk_once(KERN_WARNING "%s calls setitimer() with new_value NULL pointer."
304			    " Misfeature support will be removed\n",
305			    current->comm);
306	}
307
308	error = do_setitimer(which, &set_buffer, ovalue ? &get_buffer : NULL);
309	if (error || !ovalue)
310		return error;
311
312	if (copy_to_user(ovalue, &get_buffer, sizeof(get_buffer)))
313		return -EFAULT;
314	return 0;
315}
316
317#ifdef CONFIG_COMPAT
318COMPAT_SYSCALL_DEFINE3(setitimer, int, which,
319		       struct compat_itimerval __user *, in,
320		       struct compat_itimerval __user *, out)
321{
322	struct itimerval kin, kout;
323	int error;
324
325	if (in) {
326		if (get_compat_itimerval(&kin, in))
327			return -EFAULT;
328	} else {
329		memset(&kin, 0, sizeof(kin));
330	}
331
332	error = do_setitimer(which, &kin, out ? &kout : NULL);
333	if (error || !out)
334		return error;
335	if (put_compat_itimerval(out, &kout))
336		return -EFAULT;
337	return 0;
338}
339#endif