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