1 // SPDX-License-Identifier: GPL-2.0
3 * linux/kernel/itimer.c
5 * Copyright (C) 1992 Darren Senn
8 /* These are all the functions necessary to implement itimers */
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>
21 #include <linux/uaccess.h>
24 * itimer_get_remtime - get remaining time for the timer
26 * @timer: the timer to read
28 * Returns the delta between the expiry time and now, which can be
29 * less than zero or 1usec for an pending expired timer
31 static struct timeval itimer_get_remtime(struct hrtimer *timer)
33 ktime_t rem = __hrtimer_get_remaining(timer, true);
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.
40 if (hrtimer_active(timer)) {
46 return ktime_to_timeval(rem);
49 static void get_cpu_itimer(struct task_struct *tsk, unsigned int clock_id,
50 struct itimerval *const value)
53 struct cpu_itimer *it = &tsk->signal->it[clock_id];
55 spin_lock_irq(&tsk->sighand->siglock);
60 struct task_cputime cputime;
63 thread_group_cputimer(tsk, &cputime);
64 if (clock_id == CPUCLOCK_PROF)
65 t = cputime.utime + cputime.stime;
77 spin_unlock_irq(&tsk->sighand->siglock);
79 value->it_value = ns_to_timeval(val);
80 value->it_interval = ns_to_timeval(interval);
83 int do_getitimer(int which, struct itimerval *value)
85 struct task_struct *tsk = current;
89 spin_lock_irq(&tsk->sighand->siglock);
90 value->it_value = itimer_get_remtime(&tsk->signal->real_timer);
92 ktime_to_timeval(tsk->signal->it_real_incr);
93 spin_unlock_irq(&tsk->sighand->siglock);
96 get_cpu_itimer(tsk, CPUCLOCK_VIRT, value);
99 get_cpu_itimer(tsk, CPUCLOCK_PROF, value);
107 SYSCALL_DEFINE2(getitimer, int, which, struct itimerval __user *, value)
110 struct itimerval get_buffer;
113 error = do_getitimer(which, &get_buffer);
115 copy_to_user(value, &get_buffer, sizeof(get_buffer)))
122 COMPAT_SYSCALL_DEFINE2(getitimer, int, which,
123 struct compat_itimerval __user *, it)
125 struct itimerval kit;
126 int error = do_getitimer(which, &kit);
128 if (!error && put_compat_itimerval(it, &kit))
136 * The timer is automagically restarted, when interval != 0
138 enum hrtimer_restart it_real_fn(struct hrtimer *timer)
140 struct signal_struct *sig =
141 container_of(timer, struct signal_struct, real_timer);
143 trace_itimer_expire(ITIMER_REAL, sig->leader_pid, 0);
144 kill_pid_info(SIGALRM, SEND_SIG_PRIV, sig->leader_pid);
146 return HRTIMER_NORESTART;
149 static void set_cpu_itimer(struct task_struct *tsk, unsigned int clock_id,
150 const struct itimerval *const value,
151 struct itimerval *const ovalue)
153 u64 oval, nval, ointerval, ninterval;
154 struct cpu_itimer *it = &tsk->signal->it[clock_id];
157 * Use the to_ktime conversion because that clamps the maximum
158 * value to KTIME_MAX and avoid multiplication overflows.
160 nval = ktime_to_ns(timeval_to_ktime(value->it_value));
161 ninterval = ktime_to_ns(timeval_to_ktime(value->it_interval));
163 spin_lock_irq(&tsk->sighand->siglock);
166 ointerval = it->incr;
170 set_process_cpu_timer(tsk, clock_id, &nval, &oval);
173 it->incr = ninterval;
174 trace_itimer_state(clock_id == CPUCLOCK_VIRT ?
175 ITIMER_VIRTUAL : ITIMER_PROF, value, nval);
177 spin_unlock_irq(&tsk->sighand->siglock);
180 ovalue->it_value = ns_to_timeval(oval);
181 ovalue->it_interval = ns_to_timeval(ointerval);
186 * Returns true if the timeval is in canonical form
188 #define timeval_valid(t) \
189 (((t)->tv_sec >= 0) && (((unsigned long) (t)->tv_usec) < USEC_PER_SEC))
191 int do_setitimer(int which, struct itimerval *value, struct itimerval *ovalue)
193 struct task_struct *tsk = current;
194 struct hrtimer *timer;
198 * Validate the timevals in value.
200 if (!timeval_valid(&value->it_value) ||
201 !timeval_valid(&value->it_interval))
207 spin_lock_irq(&tsk->sighand->siglock);
208 timer = &tsk->signal->real_timer;
210 ovalue->it_value = itimer_get_remtime(timer);
212 = ktime_to_timeval(tsk->signal->it_real_incr);
214 /* We are sharing ->siglock with it_real_fn() */
215 if (hrtimer_try_to_cancel(timer) < 0) {
216 spin_unlock_irq(&tsk->sighand->siglock);
219 expires = timeval_to_ktime(value->it_value);
221 tsk->signal->it_real_incr =
222 timeval_to_ktime(value->it_interval);
223 hrtimer_start(timer, expires, HRTIMER_MODE_REL);
225 tsk->signal->it_real_incr = 0;
227 trace_itimer_state(ITIMER_REAL, value, 0);
228 spin_unlock_irq(&tsk->sighand->siglock);
231 set_cpu_itimer(tsk, CPUCLOCK_VIRT, value, ovalue);
234 set_cpu_itimer(tsk, CPUCLOCK_PROF, value, ovalue);
242 #ifdef __ARCH_WANT_SYS_ALARM
245 * alarm_setitimer - set alarm in seconds
247 * @seconds: number of seconds until alarm
248 * 0 disables the alarm
250 * Returns the remaining time in seconds of a pending timer or 0 when
251 * the timer is not active.
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.
256 static unsigned int alarm_setitimer(unsigned int seconds)
258 struct itimerval it_new, it_old;
260 #if BITS_PER_LONG < 64
261 if (seconds > INT_MAX)
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;
268 do_setitimer(ITIMER_REAL, &it_new, &it_old);
271 * We can't return 0 if we have an alarm pending ... And we'd
272 * better return too much than too little anyway
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++;
278 return it_old.it_value.tv_sec;
282 * For backwards compatibility? This can be done in libc so Alpha
283 * and all newer ports shouldn't need it.
285 SYSCALL_DEFINE1(alarm, unsigned int, seconds)
287 return alarm_setitimer(seconds);
292 SYSCALL_DEFINE3(setitimer, int, which, struct itimerval __user *, value,
293 struct itimerval __user *, ovalue)
295 struct itimerval set_buffer, get_buffer;
299 if(copy_from_user(&set_buffer, value, sizeof(set_buffer)))
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",
308 error = do_setitimer(which, &set_buffer, ovalue ? &get_buffer : NULL);
309 if (error || !ovalue)
312 if (copy_to_user(ovalue, &get_buffer, sizeof(get_buffer)))
318 COMPAT_SYSCALL_DEFINE3(setitimer, int, which,
319 struct compat_itimerval __user *, in,
320 struct compat_itimerval __user *, out)
322 struct itimerval kin, kout;
326 if (get_compat_itimerval(&kin, in))
329 memset(&kin, 0, sizeof(kin));
332 error = do_setitimer(which, &kin, out ? &kout : NULL);
335 if (put_compat_itimerval(out, &kout))