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, adjust: 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(lock: &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(lock: &tsk->sighand->siglock);
71
72 value->it_value = ns_to_timespec64(nsec: val);
73 value->it_interval = ns_to_timespec64(nsec: 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(lock: &tsk->sighand->siglock);
83 value->it_value = itimer_get_remtime(timer: &tsk->signal->real_timer);
84 value->it_interval =
85 ktime_to_timespec64(tsk->signal->it_real_incr);
86 spin_unlock_irq(lock: &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(to: o, from: &v, n: 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, value: &get_buffer);
117
118 if (!error && put_itimerval(o: value, i: &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(to: o, from: &v32, n: 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, value: &get_buffer);
146
147 if (!error && put_old_itimerval32(o: value, i: &get_buffer))
148 error = -EFAULT;
149 return error;
150}
151#endif
152
153/*
154 * Invoked from dequeue_signal() when SIG_ALRM is delivered.
155 *
156 * Restart the ITIMER_REAL timer if it is armed as periodic timer. Doing
157 * this in the signal delivery path instead of self rearming prevents a DoS
158 * with small increments in the high reolution timer case and reduces timer
159 * noise in general.
160 */
161void posixtimer_rearm_itimer(struct task_struct *tsk)
162{
163 struct hrtimer *tmr = &tsk->signal->real_timer;
164
165 if (!hrtimer_is_queued(timer: tmr) && tsk->signal->it_real_incr != 0) {
166 hrtimer_forward(timer: tmr, now: tmr->base->get_time(),
167 interval: tsk->signal->it_real_incr);
168 hrtimer_restart(timer: tmr);
169 }
170}
171
172/*
173 * Interval timers are restarted in the signal delivery path. See
174 * posixtimer_rearm_itimer().
175 */
176enum hrtimer_restart it_real_fn(struct hrtimer *timer)
177{
178 struct signal_struct *sig =
179 container_of(timer, struct signal_struct, real_timer);
180 struct pid *leader_pid = sig->pids[PIDTYPE_TGID];
181
182 trace_itimer_expire(ITIMER_REAL, pid: leader_pid, now: 0);
183 kill_pid_info(SIGALRM, SEND_SIG_PRIV, pid: leader_pid);
184
185 return HRTIMER_NORESTART;
186}
187
188static void set_cpu_itimer(struct task_struct *tsk, unsigned int clock_id,
189 const struct itimerspec64 *const value,
190 struct itimerspec64 *const ovalue)
191{
192 u64 oval, nval, ointerval, ninterval;
193 struct cpu_itimer *it = &tsk->signal->it[clock_id];
194
195 nval = timespec64_to_ns(ts: &value->it_value);
196 ninterval = timespec64_to_ns(ts: &value->it_interval);
197
198 spin_lock_irq(lock: &tsk->sighand->siglock);
199
200 oval = it->expires;
201 ointerval = it->incr;
202 if (oval || nval) {
203 if (nval > 0)
204 nval += TICK_NSEC;
205 set_process_cpu_timer(task: tsk, clock_idx: clock_id, newval: &nval, oldval: &oval);
206 }
207 it->expires = nval;
208 it->incr = ninterval;
209 trace_itimer_state(which: clock_id == CPUCLOCK_VIRT ?
210 ITIMER_VIRTUAL : ITIMER_PROF, value, expires: nval);
211
212 spin_unlock_irq(lock: &tsk->sighand->siglock);
213
214 if (ovalue) {
215 ovalue->it_value = ns_to_timespec64(nsec: oval);
216 ovalue->it_interval = ns_to_timespec64(nsec: ointerval);
217 }
218}
219
220/*
221 * Returns true if the timeval is in canonical form
222 */
223#define timeval_valid(t) \
224 (((t)->tv_sec >= 0) && (((unsigned long) (t)->tv_usec) < USEC_PER_SEC))
225
226static int do_setitimer(int which, struct itimerspec64 *value,
227 struct itimerspec64 *ovalue)
228{
229 struct task_struct *tsk = current;
230 struct hrtimer *timer;
231 ktime_t expires;
232
233 switch (which) {
234 case ITIMER_REAL:
235again:
236 spin_lock_irq(lock: &tsk->sighand->siglock);
237 timer = &tsk->signal->real_timer;
238 if (ovalue) {
239 ovalue->it_value = itimer_get_remtime(timer);
240 ovalue->it_interval
241 = ktime_to_timespec64(tsk->signal->it_real_incr);
242 }
243 /* We are sharing ->siglock with it_real_fn() */
244 if (hrtimer_try_to_cancel(timer) < 0) {
245 spin_unlock_irq(lock: &tsk->sighand->siglock);
246 hrtimer_cancel_wait_running(timer);
247 goto again;
248 }
249 expires = timespec64_to_ktime(ts: value->it_value);
250 if (expires != 0) {
251 tsk->signal->it_real_incr =
252 timespec64_to_ktime(ts: value->it_interval);
253 hrtimer_start(timer, tim: expires, mode: HRTIMER_MODE_REL);
254 } else
255 tsk->signal->it_real_incr = 0;
256
257 trace_itimer_state(ITIMER_REAL, value, expires: 0);
258 spin_unlock_irq(lock: &tsk->sighand->siglock);
259 break;
260 case ITIMER_VIRTUAL:
261 set_cpu_itimer(tsk, CPUCLOCK_VIRT, value, ovalue);
262 break;
263 case ITIMER_PROF:
264 set_cpu_itimer(tsk, CPUCLOCK_PROF, value, ovalue);
265 break;
266 default:
267 return -EINVAL;
268 }
269 return 0;
270}
271
272#ifdef CONFIG_SECURITY_SELINUX
273void clear_itimer(void)
274{
275 struct itimerspec64 v = {};
276 int i;
277
278 for (i = 0; i < 3; i++)
279 do_setitimer(which: i, value: &v, NULL);
280}
281#endif
282
283#ifdef __ARCH_WANT_SYS_ALARM
284
285/**
286 * alarm_setitimer - set alarm in seconds
287 *
288 * @seconds: number of seconds until alarm
289 * 0 disables the alarm
290 *
291 * Returns the remaining time in seconds of a pending timer or 0 when
292 * the timer is not active.
293 *
294 * On 32 bit machines the seconds value is limited to (INT_MAX/2) to avoid
295 * negative timeval settings which would cause immediate expiry.
296 */
297static unsigned int alarm_setitimer(unsigned int seconds)
298{
299 struct itimerspec64 it_new, it_old;
300
301#if BITS_PER_LONG < 64
302 if (seconds > INT_MAX)
303 seconds = INT_MAX;
304#endif
305 it_new.it_value.tv_sec = seconds;
306 it_new.it_value.tv_nsec = 0;
307 it_new.it_interval.tv_sec = it_new.it_interval.tv_nsec = 0;
308
309 do_setitimer(ITIMER_REAL, value: &it_new, ovalue: &it_old);
310
311 /*
312 * We can't return 0 if we have an alarm pending ... And we'd
313 * better return too much than too little anyway
314 */
315 if ((!it_old.it_value.tv_sec && it_old.it_value.tv_nsec) ||
316 it_old.it_value.tv_nsec >= (NSEC_PER_SEC / 2))
317 it_old.it_value.tv_sec++;
318
319 return it_old.it_value.tv_sec;
320}
321
322/*
323 * For backwards compatibility? This can be done in libc so Alpha
324 * and all newer ports shouldn't need it.
325 */
326SYSCALL_DEFINE1(alarm, unsigned int, seconds)
327{
328 return alarm_setitimer(seconds);
329}
330
331#endif
332
333static int get_itimerval(struct itimerspec64 *o, const struct __kernel_old_itimerval __user *i)
334{
335 struct __kernel_old_itimerval v;
336
337 if (copy_from_user(to: &v, from: i, n: sizeof(struct __kernel_old_itimerval)))
338 return -EFAULT;
339
340 /* Validate the timevals in value. */
341 if (!timeval_valid(&v.it_value) ||
342 !timeval_valid(&v.it_interval))
343 return -EINVAL;
344
345 o->it_interval.tv_sec = v.it_interval.tv_sec;
346 o->it_interval.tv_nsec = v.it_interval.tv_usec * NSEC_PER_USEC;
347 o->it_value.tv_sec = v.it_value.tv_sec;
348 o->it_value.tv_nsec = v.it_value.tv_usec * NSEC_PER_USEC;
349 return 0;
350}
351
352SYSCALL_DEFINE3(setitimer, int, which, struct __kernel_old_itimerval __user *, value,
353 struct __kernel_old_itimerval __user *, ovalue)
354{
355 struct itimerspec64 set_buffer, get_buffer;
356 int error;
357
358 if (value) {
359 error = get_itimerval(o: &set_buffer, i: value);
360 if (error)
361 return error;
362 } else {
363 memset(&set_buffer, 0, sizeof(set_buffer));
364 printk_once(KERN_WARNING "%s calls setitimer() with new_value NULL pointer."
365 " Misfeature support will be removed\n",
366 current->comm);
367 }
368
369 error = do_setitimer(which, value: &set_buffer, ovalue: ovalue ? &get_buffer : NULL);
370 if (error || !ovalue)
371 return error;
372
373 if (put_itimerval(o: ovalue, i: &get_buffer))
374 return -EFAULT;
375 return 0;
376}
377
378#if defined(CONFIG_COMPAT) || defined(CONFIG_ALPHA)
379static int get_old_itimerval32(struct itimerspec64 *o, const struct old_itimerval32 __user *i)
380{
381 struct old_itimerval32 v32;
382
383 if (copy_from_user(to: &v32, from: i, n: sizeof(struct old_itimerval32)))
384 return -EFAULT;
385
386 /* Validate the timevals in value. */
387 if (!timeval_valid(&v32.it_value) ||
388 !timeval_valid(&v32.it_interval))
389 return -EINVAL;
390
391 o->it_interval.tv_sec = v32.it_interval.tv_sec;
392 o->it_interval.tv_nsec = v32.it_interval.tv_usec * NSEC_PER_USEC;
393 o->it_value.tv_sec = v32.it_value.tv_sec;
394 o->it_value.tv_nsec = v32.it_value.tv_usec * NSEC_PER_USEC;
395 return 0;
396}
397
398COMPAT_SYSCALL_DEFINE3(setitimer, int, which,
399 struct old_itimerval32 __user *, value,
400 struct old_itimerval32 __user *, ovalue)
401{
402 struct itimerspec64 set_buffer, get_buffer;
403 int error;
404
405 if (value) {
406 error = get_old_itimerval32(o: &set_buffer, i: value);
407 if (error)
408 return error;
409 } else {
410 memset(&set_buffer, 0, sizeof(set_buffer));
411 printk_once(KERN_WARNING "%s calls setitimer() with new_value NULL pointer."
412 " Misfeature support will be removed\n",
413 current->comm);
414 }
415
416 error = do_setitimer(which, value: &set_buffer, ovalue: ovalue ? &get_buffer : NULL);
417 if (error || !ovalue)
418 return error;
419 if (put_old_itimerval32(o: ovalue, i: &get_buffer))
420 return -EFAULT;
421 return 0;
422}
423#endif
424

source code of linux/kernel/time/itimer.c