1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Copyright (C) 1992 Darren Senn
4 */
5
6/* These are all the functions necessary to implement itimers */
7
8#include <linux/mm.h>
9#include <linux/interrupt.h>
10#include <linux/syscalls.h>
11#include <linux/time.h>
12#include <linux/sched/signal.h>
13#include <linux/sched/cputime.h>
14#include <linux/posix-timers.h>
15#include <linux/hrtimer.h>
16#include <trace/events/timer.h>
17#include <linux/compat.h>
18
19#include <linux/uaccess.h>
20
21/**
22 * itimer_get_remtime - get remaining time for the timer
23 *
24 * @timer: the timer to read
25 *
26 * Returns the delta between the expiry time and now, which can be
27 * less than zero or 1usec for an pending expired timer
28 */
29static struct timespec64 itimer_get_remtime(struct hrtimer *timer)
30{
31	ktime_t rem = __hrtimer_get_remaining(timer, true);
32
33	/*
34	 * Racy but safe: if the itimer expires after the above
35	 * hrtimer_get_remtime() call but before this condition
36	 * then we return 0 - which is correct.
37	 */
38	if (hrtimer_active(timer)) {
39		if (rem <= 0)
40			rem = NSEC_PER_USEC;
41	} else
42		rem = 0;
43
44	return ktime_to_timespec64(rem);
45}
46
47static void get_cpu_itimer(struct task_struct *tsk, unsigned int clock_id,
48			   struct itimerspec64 *const value)
49{
50	u64 val, interval;
51	struct cpu_itimer *it = &tsk->signal->it[clock_id];
52
53	spin_lock_irq(&tsk->sighand->siglock);
54
55	val = it->expires;
56	interval = it->incr;
57	if (val) {
58		u64 t, samples[CPUCLOCK_MAX];
59
60		thread_group_sample_cputime(tsk, samples);
61		t = samples[clock_id];
62
63		if (val < t)
64			/* about to fire */
65			val = TICK_NSEC;
66		else
67			val -= t;
68	}
69
70	spin_unlock_irq(&tsk->sighand->siglock);
71
72	value->it_value = ns_to_timespec64(val);
73	value->it_interval = ns_to_timespec64(interval);
74}
75
76static int do_getitimer(int which, struct itimerspec64 *value)
77{
78	struct task_struct *tsk = current;
79
80	switch (which) {
81	case ITIMER_REAL:
82		spin_lock_irq(&tsk->sighand->siglock);
83		value->it_value = itimer_get_remtime(&tsk->signal->real_timer);
84		value->it_interval =
85			ktime_to_timespec64(tsk->signal->it_real_incr);
86		spin_unlock_irq(&tsk->sighand->siglock);
87		break;
88	case ITIMER_VIRTUAL:
89		get_cpu_itimer(tsk, CPUCLOCK_VIRT, value);
90		break;
91	case ITIMER_PROF:
92		get_cpu_itimer(tsk, CPUCLOCK_PROF, value);
93		break;
94	default:
95		return(-EINVAL);
96	}
97	return 0;
98}
99
100static int put_itimerval(struct __kernel_old_itimerval __user *o,
101			 const struct itimerspec64 *i)
102{
103	struct __kernel_old_itimerval v;
104
105	v.it_interval.tv_sec = i->it_interval.tv_sec;
106	v.it_interval.tv_usec = i->it_interval.tv_nsec / NSEC_PER_USEC;
107	v.it_value.tv_sec = i->it_value.tv_sec;
108	v.it_value.tv_usec = i->it_value.tv_nsec / NSEC_PER_USEC;
109	return copy_to_user(o, &v, sizeof(struct __kernel_old_itimerval)) ? -EFAULT : 0;
110}
111
112
113SYSCALL_DEFINE2(getitimer, int, which, struct __kernel_old_itimerval __user *, value)
114{
115	struct itimerspec64 get_buffer;
116	int error = do_getitimer(which, &get_buffer);
117
118	if (!error && put_itimerval(value, &get_buffer))
119		error = -EFAULT;
120	return error;
121}
122
123#if defined(CONFIG_COMPAT) || defined(CONFIG_ALPHA)
124struct old_itimerval32 {
125	struct old_timeval32	it_interval;
126	struct old_timeval32	it_value;
127};
128
129static int put_old_itimerval32(struct old_itimerval32 __user *o,
130			       const struct itimerspec64 *i)
131{
132	struct old_itimerval32 v32;
133
134	v32.it_interval.tv_sec = i->it_interval.tv_sec;
135	v32.it_interval.tv_usec = i->it_interval.tv_nsec / NSEC_PER_USEC;
136	v32.it_value.tv_sec = i->it_value.tv_sec;
137	v32.it_value.tv_usec = i->it_value.tv_nsec / NSEC_PER_USEC;
138	return copy_to_user(o, &v32, sizeof(struct old_itimerval32)) ? -EFAULT : 0;
139}
140
141COMPAT_SYSCALL_DEFINE2(getitimer, int, which,
142		       struct old_itimerval32 __user *, value)
143{
144	struct itimerspec64 get_buffer;
145	int error = do_getitimer(which, &get_buffer);
146
147	if (!error && put_old_itimerval32(value, &get_buffer))
148		error = -EFAULT;
149	return error;
150}
151#endif
152
153/*
154 * The timer is automagically restarted, when interval != 0
155 */
156enum hrtimer_restart it_real_fn(struct hrtimer *timer)
157{
158	struct signal_struct *sig =
159		container_of(timer, struct signal_struct, real_timer);
160	struct pid *leader_pid = sig->pids[PIDTYPE_TGID];
161
162	trace_itimer_expire(ITIMER_REAL, leader_pid, 0);
163	kill_pid_info(SIGALRM, SEND_SIG_PRIV, leader_pid);
164
165	return HRTIMER_NORESTART;
166}
167
168static void set_cpu_itimer(struct task_struct *tsk, unsigned int clock_id,
169			   const struct itimerspec64 *const value,
170			   struct itimerspec64 *const ovalue)
171{
172	u64 oval, nval, ointerval, ninterval;
173	struct cpu_itimer *it = &tsk->signal->it[clock_id];
174
175	nval = timespec64_to_ns(&value->it_value);
176	ninterval = timespec64_to_ns(&value->it_interval);
177
178	spin_lock_irq(&tsk->sighand->siglock);
179
180	oval = it->expires;
181	ointerval = it->incr;
182	if (oval || nval) {
183		if (nval > 0)
184			nval += TICK_NSEC;
185		set_process_cpu_timer(tsk, clock_id, &nval, &oval);
186	}
187	it->expires = nval;
188	it->incr = ninterval;
189	trace_itimer_state(clock_id == CPUCLOCK_VIRT ?
190			   ITIMER_VIRTUAL : ITIMER_PROF, value, nval);
191
192	spin_unlock_irq(&tsk->sighand->siglock);
193
194	if (ovalue) {
195		ovalue->it_value = ns_to_timespec64(oval);
196		ovalue->it_interval = ns_to_timespec64(ointerval);
197	}
198}
199
200/*
201 * Returns true if the timeval is in canonical form
202 */
203#define timeval_valid(t) \
204	(((t)->tv_sec >= 0) && (((unsigned long) (t)->tv_usec) < USEC_PER_SEC))
205
206static int do_setitimer(int which, struct itimerspec64 *value,
207			struct itimerspec64 *ovalue)
208{
209	struct task_struct *tsk = current;
210	struct hrtimer *timer;
211	ktime_t expires;
212
213	switch (which) {
214	case ITIMER_REAL:
215again:
216		spin_lock_irq(&tsk->sighand->siglock);
217		timer = &tsk->signal->real_timer;
218		if (ovalue) {
219			ovalue->it_value = itimer_get_remtime(timer);
220			ovalue->it_interval
221				= ktime_to_timespec64(tsk->signal->it_real_incr);
222		}
223		/* We are sharing ->siglock with it_real_fn() */
224		if (hrtimer_try_to_cancel(timer) < 0) {
225			spin_unlock_irq(&tsk->sighand->siglock);
226			hrtimer_cancel_wait_running(timer);
227			goto again;
228		}
229		expires = timespec64_to_ktime(value->it_value);
230		if (expires != 0) {
231			tsk->signal->it_real_incr =
232				timespec64_to_ktime(value->it_interval);
233			hrtimer_start(timer, expires, HRTIMER_MODE_REL);
234		} else
235			tsk->signal->it_real_incr = 0;
236
237		trace_itimer_state(ITIMER_REAL, value, 0);
238		spin_unlock_irq(&tsk->sighand->siglock);
239		break;
240	case ITIMER_VIRTUAL:
241		set_cpu_itimer(tsk, CPUCLOCK_VIRT, value, ovalue);
242		break;
243	case ITIMER_PROF:
244		set_cpu_itimer(tsk, CPUCLOCK_PROF, value, ovalue);
245		break;
246	default:
247		return -EINVAL;
248	}
249	return 0;
250}
251
252#ifdef CONFIG_SECURITY_SELINUX
253void clear_itimer(void)
254{
255	struct itimerspec64 v = {};
256	int i;
257
258	for (i = 0; i < 3; i++)
259		do_setitimer(i, &v, NULL);
260}
261#endif
262
263#ifdef __ARCH_WANT_SYS_ALARM
264
265/**
266 * alarm_setitimer - set alarm in seconds
267 *
268 * @seconds:	number of seconds until alarm
269 *		0 disables the alarm
270 *
271 * Returns the remaining time in seconds of a pending timer or 0 when
272 * the timer is not active.
273 *
274 * On 32 bit machines the seconds value is limited to (INT_MAX/2) to avoid
275 * negative timeval settings which would cause immediate expiry.
276 */
277static unsigned int alarm_setitimer(unsigned int seconds)
278{
279	struct itimerspec64 it_new, it_old;
280
281#if BITS_PER_LONG < 64
282	if (seconds > INT_MAX)
283		seconds = INT_MAX;
284#endif
285	it_new.it_value.tv_sec = seconds;
286	it_new.it_value.tv_nsec = 0;
287	it_new.it_interval.tv_sec = it_new.it_interval.tv_nsec = 0;
288
289	do_setitimer(ITIMER_REAL, &it_new, &it_old);
290
291	/*
292	 * We can't return 0 if we have an alarm pending ...  And we'd
293	 * better return too much than too little anyway
294	 */
295	if ((!it_old.it_value.tv_sec && it_old.it_value.tv_nsec) ||
296	      it_old.it_value.tv_nsec >= (NSEC_PER_SEC / 2))
297		it_old.it_value.tv_sec++;
298
299	return it_old.it_value.tv_sec;
300}
301
302/*
303 * For backwards compatibility?  This can be done in libc so Alpha
304 * and all newer ports shouldn't need it.
305 */
306SYSCALL_DEFINE1(alarm, unsigned int, seconds)
307{
308	return alarm_setitimer(seconds);
309}
310
311#endif
312
313static int get_itimerval(struct itimerspec64 *o, const struct __kernel_old_itimerval __user *i)
314{
315	struct __kernel_old_itimerval v;
316
317	if (copy_from_user(&v, i, sizeof(struct __kernel_old_itimerval)))
318		return -EFAULT;
319
320	/* Validate the timevals in value. */
321	if (!timeval_valid(&v.it_value) ||
322	    !timeval_valid(&v.it_interval))
323		return -EINVAL;
324
325	o->it_interval.tv_sec = v.it_interval.tv_sec;
326	o->it_interval.tv_nsec = v.it_interval.tv_usec * NSEC_PER_USEC;
327	o->it_value.tv_sec = v.it_value.tv_sec;
328	o->it_value.tv_nsec = v.it_value.tv_usec * NSEC_PER_USEC;
329	return 0;
330}
331
332SYSCALL_DEFINE3(setitimer, int, which, struct __kernel_old_itimerval __user *, value,
333		struct __kernel_old_itimerval __user *, ovalue)
334{
335	struct itimerspec64 set_buffer, get_buffer;
336	int error;
337
338	if (value) {
339		error = get_itimerval(&set_buffer, value);
340		if (error)
341			return error;
342	} else {
343		memset(&set_buffer, 0, sizeof(set_buffer));
344		printk_once(KERN_WARNING "%s calls setitimer() with new_value NULL pointer."
345			    " Misfeature support will be removed\n",
346			    current->comm);
347	}
348
349	error = do_setitimer(which, &set_buffer, ovalue ? &get_buffer : NULL);
350	if (error || !ovalue)
351		return error;
352
353	if (put_itimerval(ovalue, &get_buffer))
354		return -EFAULT;
355	return 0;
356}
357
358#if defined(CONFIG_COMPAT) || defined(CONFIG_ALPHA)
359static int get_old_itimerval32(struct itimerspec64 *o, const struct old_itimerval32 __user *i)
360{
361	struct old_itimerval32 v32;
362
363	if (copy_from_user(&v32, i, sizeof(struct old_itimerval32)))
364		return -EFAULT;
365
366	/* Validate the timevals in value.  */
367	if (!timeval_valid(&v32.it_value) ||
368	    !timeval_valid(&v32.it_interval))
369		return -EINVAL;
370
371	o->it_interval.tv_sec = v32.it_interval.tv_sec;
372	o->it_interval.tv_nsec = v32.it_interval.tv_usec * NSEC_PER_USEC;
373	o->it_value.tv_sec = v32.it_value.tv_sec;
374	o->it_value.tv_nsec = v32.it_value.tv_usec * NSEC_PER_USEC;
375	return 0;
376}
377
378COMPAT_SYSCALL_DEFINE3(setitimer, int, which,
379		       struct old_itimerval32 __user *, value,
380		       struct old_itimerval32 __user *, ovalue)
381{
382	struct itimerspec64 set_buffer, get_buffer;
383	int error;
384
385	if (value) {
386		error = get_old_itimerval32(&set_buffer, value);
387		if (error)
388			return error;
389	} else {
390		memset(&set_buffer, 0, sizeof(set_buffer));
391		printk_once(KERN_WARNING "%s calls setitimer() with new_value NULL pointer."
392			    " Misfeature support will be removed\n",
393			    current->comm);
394	}
395
396	error = do_setitimer(which, &set_buffer, ovalue ? &get_buffer : NULL);
397	if (error || !ovalue)
398		return error;
399	if (put_old_itimerval32(ovalue, &get_buffer))
400		return -EFAULT;
401	return 0;
402}
403#endif
404