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);
142 struct pid *leader_pid = sig->pids[PIDTYPE_TGID];
144 trace_itimer_expire(ITIMER_REAL, leader_pid, 0);
145 kill_pid_info(SIGALRM, SEND_SIG_PRIV, leader_pid);
147 return HRTIMER_NORESTART;
150 static void set_cpu_itimer(struct task_struct *tsk, unsigned int clock_id,
151 const struct itimerval *const value,
152 struct itimerval *const ovalue)
154 u64 oval, nval, ointerval, ninterval;
155 struct cpu_itimer *it = &tsk->signal->it[clock_id];
158 * Use the to_ktime conversion because that clamps the maximum
159 * value to KTIME_MAX and avoid multiplication overflows.
161 nval = ktime_to_ns(timeval_to_ktime(value->it_value));
162 ninterval = ktime_to_ns(timeval_to_ktime(value->it_interval));
164 spin_lock_irq(&tsk->sighand->siglock);
167 ointerval = it->incr;
171 set_process_cpu_timer(tsk, clock_id, &nval, &oval);
174 it->incr = ninterval;
175 trace_itimer_state(clock_id == CPUCLOCK_VIRT ?
176 ITIMER_VIRTUAL : ITIMER_PROF, value, nval);
178 spin_unlock_irq(&tsk->sighand->siglock);
181 ovalue->it_value = ns_to_timeval(oval);
182 ovalue->it_interval = ns_to_timeval(ointerval);
187 * Returns true if the timeval is in canonical form
189 #define timeval_valid(t) \
190 (((t)->tv_sec >= 0) && (((unsigned long) (t)->tv_usec) < USEC_PER_SEC))
192 int do_setitimer(int which, struct itimerval *value, struct itimerval *ovalue)
194 struct task_struct *tsk = current;
195 struct hrtimer *timer;
199 * Validate the timevals in value.
201 if (!timeval_valid(&value->it_value) ||
202 !timeval_valid(&value->it_interval))
208 spin_lock_irq(&tsk->sighand->siglock);
209 timer = &tsk->signal->real_timer;
211 ovalue->it_value = itimer_get_remtime(timer);
213 = ktime_to_timeval(tsk->signal->it_real_incr);
215 /* We are sharing ->siglock with it_real_fn() */
216 if (hrtimer_try_to_cancel(timer) < 0) {
217 spin_unlock_irq(&tsk->sighand->siglock);
220 expires = timeval_to_ktime(value->it_value);
222 tsk->signal->it_real_incr =
223 timeval_to_ktime(value->it_interval);
224 hrtimer_start(timer, expires, HRTIMER_MODE_REL);
226 tsk->signal->it_real_incr = 0;
228 trace_itimer_state(ITIMER_REAL, value, 0);
229 spin_unlock_irq(&tsk->sighand->siglock);
232 set_cpu_itimer(tsk, CPUCLOCK_VIRT, value, ovalue);
235 set_cpu_itimer(tsk, CPUCLOCK_PROF, value, ovalue);
243 #ifdef __ARCH_WANT_SYS_ALARM
246 * alarm_setitimer - set alarm in seconds
248 * @seconds: number of seconds until alarm
249 * 0 disables the alarm
251 * Returns the remaining time in seconds of a pending timer or 0 when
252 * the timer is not active.
254 * On 32 bit machines the seconds value is limited to (INT_MAX/2) to avoid
255 * negative timeval settings which would cause immediate expiry.
257 static unsigned int alarm_setitimer(unsigned int seconds)
259 struct itimerval it_new, it_old;
261 #if BITS_PER_LONG < 64
262 if (seconds > INT_MAX)
265 it_new.it_value.tv_sec = seconds;
266 it_new.it_value.tv_usec = 0;
267 it_new.it_interval.tv_sec = it_new.it_interval.tv_usec = 0;
269 do_setitimer(ITIMER_REAL, &it_new, &it_old);
272 * We can't return 0 if we have an alarm pending ... And we'd
273 * better return too much than too little anyway
275 if ((!it_old.it_value.tv_sec && it_old.it_value.tv_usec) ||
276 it_old.it_value.tv_usec >= 500000)
277 it_old.it_value.tv_sec++;
279 return it_old.it_value.tv_sec;
283 * For backwards compatibility? This can be done in libc so Alpha
284 * and all newer ports shouldn't need it.
286 SYSCALL_DEFINE1(alarm, unsigned int, seconds)
288 return alarm_setitimer(seconds);
293 SYSCALL_DEFINE3(setitimer, int, which, struct itimerval __user *, value,
294 struct itimerval __user *, ovalue)
296 struct itimerval set_buffer, get_buffer;
300 if(copy_from_user(&set_buffer, value, sizeof(set_buffer)))
303 memset(&set_buffer, 0, sizeof(set_buffer));
304 printk_once(KERN_WARNING "%s calls setitimer() with new_value NULL pointer."
305 " Misfeature support will be removed\n",
309 error = do_setitimer(which, &set_buffer, ovalue ? &get_buffer : NULL);
310 if (error || !ovalue)
313 if (copy_to_user(ovalue, &get_buffer, sizeof(get_buffer)))
319 COMPAT_SYSCALL_DEFINE3(setitimer, int, which,
320 struct compat_itimerval __user *, in,
321 struct compat_itimerval __user *, out)
323 struct itimerval kin, kout;
327 if (get_compat_itimerval(&kin, in))
330 memset(&kin, 0, sizeof(kin));
333 error = do_setitimer(which, &kin, out ? &kout : NULL);
336 if (put_compat_itimerval(out, &kout))