1/*
  2 * linux/kernel/itimer.c
  3 *
  4 * Copyright (C) 1992 Darren Senn
  5 */
  6
  7/* These are all the functions necessary to implement itimers */
  8
  9#include <linux/mm.h>
 10#include <linux/interrupt.h>
 11#include <linux/syscalls.h>
 12#include <linux/time.h>
 13#include <linux/posix-timers.h>
 14#include <linux/hrtimer.h>
 15#include <trace/events/timer.h>
 16
 17#include <asm/uaccess.h>
 18
 19/**
 20 * itimer_get_remtime - get remaining time for the timer
 21 *
 22 * @timer: the timer to read
 23 *
 24 * Returns the delta between the expiry time and now, which can be
 25 * less than zero or 1usec for an pending expired timer
 26 */
 27static struct timeval itimer_get_remtime(struct hrtimer *timer)
 28{
 29	ktime_t rem = hrtimer_get_remaining(timer);
 30
 31	/*
 32	 * Racy but safe: if the itimer expires after the above
 33	 * hrtimer_get_remtime() call but before this condition
 34	 * then we return 0 - which is correct.
 35	 */
 36	if (hrtimer_active(timer)) {
 37		if (rem.tv64 <= 0)
 38			rem.tv64 = NSEC_PER_USEC;
 39	} else
 40		rem.tv64 = 0;
 41
 42	return ktime_to_timeval(rem);
 43}
 44
 45static void get_cpu_itimer(struct task_struct *tsk, unsigned int clock_id,
 46			   struct itimerval *const value)
 47{
 48	cputime_t cval, cinterval;
 49	struct cpu_itimer *it = &tsk->signal->it[clock_id];
 50
 51	spin_lock_irq(&tsk->sighand->siglock);
 52
 53	cval = it->expires;
 54	cinterval = it->incr;
 55	if (!cputime_eq(cval, cputime_zero)) {
 56		struct task_cputime cputime;
 57		cputime_t t;
 58
 59		thread_group_cputimer(tsk, &cputime);
 60		if (clock_id == CPUCLOCK_PROF)
 61			t = cputime_add(cputime.utime, cputime.stime);
 62		else
 63			/* CPUCLOCK_VIRT */
 64			t = cputime.utime;
 65
 66		if (cputime_le(cval, t))
 67			/* about to fire */
 68			cval = cputime_one_jiffy;
 69		else
 70			cval = cputime_sub(cval, t);
 71	}
 72
 73	spin_unlock_irq(&tsk->sighand->siglock);
 74
 75	cputime_to_timeval(cval, &value->it_value);
 76	cputime_to_timeval(cinterval, &value->it_interval);
 77}
 78
 79int do_getitimer(int which, struct itimerval *value)
 80{
 81	struct task_struct *tsk = current;
 82
 83	switch (which) {
 84	case ITIMER_REAL:
 85		spin_lock_irq(&tsk->sighand->siglock);
 86		value->it_value = itimer_get_remtime(&tsk->signal->real_timer);
 87		value->it_interval =
 88			ktime_to_timeval(tsk->signal->it_real_incr);
 89		spin_unlock_irq(&tsk->sighand->siglock);
 90		break;
 91	case ITIMER_VIRTUAL:
 92		get_cpu_itimer(tsk, CPUCLOCK_VIRT, value);
 93		break;
 94	case ITIMER_PROF:
 95		get_cpu_itimer(tsk, CPUCLOCK_PROF, value);
 96		break;
 97	default:
 98		return(-EINVAL);
 99	}
100	return 0;
101}
102
103SYSCALL_DEFINE2(getitimer, int, which, struct itimerval __user *, value)
104{
105	int error = -EFAULT;
106	struct itimerval get_buffer;
107
108	if (value) {
109		error = do_getitimer(which, &get_buffer);
110		if (!error &&
111		    copy_to_user(value, &get_buffer, sizeof(get_buffer)))
112			error = -EFAULT;
113	}
114	return error;
115}
116
117
118/*
119 * The timer is automagically restarted, when interval != 0
120 */
121enum hrtimer_restart it_real_fn(struct hrtimer *timer)
122{
123	struct signal_struct *sig =
124		container_of(timer, struct signal_struct, real_timer);
125
126	trace_itimer_expire(ITIMER_REAL, sig->leader_pid, 0);
127	kill_pid_info(SIGALRM, SEND_SIG_PRIV, sig->leader_pid);
128
129	return HRTIMER_NORESTART;
130}
131
132static inline u32 cputime_sub_ns(cputime_t ct, s64 real_ns)
133{
134	struct timespec ts;
135	s64 cpu_ns;
136
137	cputime_to_timespec(ct, &ts);
138	cpu_ns = timespec_to_ns(&ts);
139
140	return (cpu_ns <= real_ns) ? 0 : cpu_ns - real_ns;
141}
142
143static void set_cpu_itimer(struct task_struct *tsk, unsigned int clock_id,
144			   const struct itimerval *const value,
145			   struct itimerval *const ovalue)
146{
147	cputime_t cval, nval, cinterval, ninterval;
148	s64 ns_ninterval, ns_nval;
149	u32 error, incr_error;
150	struct cpu_itimer *it = &tsk->signal->it[clock_id];
151
152	nval = timeval_to_cputime(&value->it_value);
153	ns_nval = timeval_to_ns(&value->it_value);
154	ninterval = timeval_to_cputime(&value->it_interval);
155	ns_ninterval = timeval_to_ns(&value->it_interval);
156
157	error = cputime_sub_ns(nval, ns_nval);
158	incr_error = cputime_sub_ns(ninterval, ns_ninterval);
159
160	spin_lock_irq(&tsk->sighand->siglock);
161
162	cval = it->expires;
163	cinterval = it->incr;
164	if (!cputime_eq(cval, cputime_zero) ||
165	    !cputime_eq(nval, cputime_zero)) {
166		if (cputime_gt(nval, cputime_zero))
167			nval = cputime_add(nval, cputime_one_jiffy);
168		set_process_cpu_timer(tsk, clock_id, &nval, &cval);
169	}
170	it->expires = nval;
171	it->incr = ninterval;
172	it->error = error;
173	it->incr_error = incr_error;
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		cputime_to_timeval(cval, &ovalue->it_value);
181		cputime_to_timeval(cinterval, &ovalue->it_interval);
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.tv64 != 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.tv64 = 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/**
243 * alarm_setitimer - set alarm in seconds
244 *
245 * @seconds:	number of seconds until alarm
246 *		0 disables the alarm
247 *
248 * Returns the remaining time in seconds of a pending timer or 0 when
249 * the timer is not active.
250 *
251 * On 32 bit machines the seconds value is limited to (INT_MAX/2) to avoid
252 * negative timeval settings which would cause immediate expiry.
253 */
254unsigned int alarm_setitimer(unsigned int seconds)
255{
256	struct itimerval it_new, it_old;
257
258#if BITS_PER_LONG < 64
259	if (seconds > INT_MAX)
260		seconds = INT_MAX;
261#endif
262	it_new.it_value.tv_sec = seconds;
263	it_new.it_value.tv_usec = 0;
264	it_new.it_interval.tv_sec = it_new.it_interval.tv_usec = 0;
265
266	do_setitimer(ITIMER_REAL, &it_new, &it_old);
267
268	/*
269	 * We can't return 0 if we have an alarm pending ...  And we'd
270	 * better return too much than too little anyway
271	 */
272	if ((!it_old.it_value.tv_sec && it_old.it_value.tv_usec) ||
273	      it_old.it_value.tv_usec >= 500000)
274		it_old.it_value.tv_sec++;
275
276	return it_old.it_value.tv_sec;
277}
278
279SYSCALL_DEFINE3(setitimer, int, which, struct itimerval __user *, value,
280		struct itimerval __user *, ovalue)
281{
282	struct itimerval set_buffer, get_buffer;
283	int error;
284
285	if (value) {
286		if(copy_from_user(&set_buffer, value, sizeof(set_buffer)))
287			return -EFAULT;
288	} else
289		memset((char *) &set_buffer, 0, sizeof(set_buffer));
290
291	error = do_setitimer(which, &set_buffer, ovalue ? &get_buffer : NULL);
292	if (error || !ovalue)
293		return error;
294
295	if (copy_to_user(ovalue, &get_buffer, sizeof(get_buffer)))
296		return -EFAULT;
297	return 0;
298}