projects/linux·blob v4.20 · refs

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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * linux/kernel/itimer.c
4 *
5 * Copyright (C) 1992 Darren Senn
6 */
7
8/* These are all the functions necessary to implement itimers */
9
10#include <linux/mm.h>
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>
20
21#include <linux/uaccess.h>
22
23/**
24 * itimer_get_remtime - get remaining time for the timer
25 *
26 * @timer: the timer to read
27 *
28 * Returns the delta between the expiry time and now, which can be
29 * less than zero or 1usec for an pending expired timer
30 */
31static struct timeval itimer_get_remtime(struct hrtimer *timer)
32{
33 ktime_t rem = __hrtimer_get_remaining(timer, true);
34
35 /*
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.
39 */
40 if (hrtimer_active(timer)) {
41 if (rem <= 0)
42 rem = NSEC_PER_USEC;
43 } else
44 rem = 0;
45
46 return ktime_to_timeval(rem);
47}
48
49static void get_cpu_itimer(struct task_struct *tsk, unsigned int clock_id,
50 struct itimerval *const value)
51{
52 u64 val, interval;
53 struct cpu_itimer *it = &tsk->signal->it[clock_id];
54
55 spin_lock_irq(&tsk->sighand->siglock);
56
57 val = it->expires;
58 interval = it->incr;
59 if (val) {
60 struct task_cputime cputime;
61 u64 t;
62
63 thread_group_cputimer(tsk, &cputime);
64 if (clock_id == CPUCLOCK_PROF)
65 t = cputime.utime + cputime.stime;
66 else
67 /* CPUCLOCK_VIRT */
68 t = cputime.utime;
69
70 if (val < t)
71 /* about to fire */
72 val = TICK_NSEC;
73 else
74 val -= t;
75 }
76
77 spin_unlock_irq(&tsk->sighand->siglock);
78
79 value->it_value = ns_to_timeval(val);
80 value->it_interval = ns_to_timeval(interval);
81}
82
83int do_getitimer(int which, struct itimerval *value)
84{
85 struct task_struct *tsk = current;
86
87 switch (which) {
88 case ITIMER_REAL:
89 spin_lock_irq(&tsk->sighand->siglock);
90 value->it_value = itimer_get_remtime(&tsk->signal->real_timer);
91 value->it_interval =
92 ktime_to_timeval(tsk->signal->it_real_incr);
93 spin_unlock_irq(&tsk->sighand->siglock);
94 break;
95 case ITIMER_VIRTUAL:
96 get_cpu_itimer(tsk, CPUCLOCK_VIRT, value);
97 break;
98 case ITIMER_PROF:
99 get_cpu_itimer(tsk, CPUCLOCK_PROF, value);
100 break;
101 default:
102 return(-EINVAL);
103 }
104 return 0;
105}
106
107SYSCALL_DEFINE2(getitimer, int, which, struct itimerval __user *, value)
108{
109 int error = -EFAULT;
110 struct itimerval get_buffer;
111
112 if (value) {
113 error = do_getitimer(which, &get_buffer);
114 if (!error &&
115 copy_to_user(value, &get_buffer, sizeof(get_buffer)))
116 error = -EFAULT;
117 }
118 return error;
119}
120
121#ifdef CONFIG_COMPAT
122COMPAT_SYSCALL_DEFINE2(getitimer, int, which,
123 struct compat_itimerval __user *, it)
124{
125 struct itimerval kit;
126 int error = do_getitimer(which, &kit);
127
128 if (!error && put_compat_itimerval(it, &kit))
129 error = -EFAULT;
130 return error;
131}
132#endif
133
134
135/*
136 * The timer is automagically restarted, when interval != 0
137 */
138enum hrtimer_restart it_real_fn(struct hrtimer *timer)
139{
140 struct signal_struct *sig =
141 container_of(timer, struct signal_struct, real_timer);
142 struct pid *leader_pid = sig->pids[PIDTYPE_TGID];
143
144 trace_itimer_expire(ITIMER_REAL, leader_pid, 0);
145 kill_pid_info(SIGALRM, SEND_SIG_PRIV, leader_pid);
146
147 return HRTIMER_NORESTART;
148}
149
150static void set_cpu_itimer(struct task_struct *tsk, unsigned int clock_id,
151 const struct itimerval *const value,
152 struct itimerval *const ovalue)
153{
154 u64 oval, nval, ointerval, ninterval;
155 struct cpu_itimer *it = &tsk->signal->it[clock_id];
156
157 /*
158 * Use the to_ktime conversion because that clamps the maximum
159 * value to KTIME_MAX and avoid multiplication overflows.
160 */
161 nval = ktime_to_ns(timeval_to_ktime(value->it_value));
162 ninterval = ktime_to_ns(timeval_to_ktime(value->it_interval));
163
164 spin_lock_irq(&tsk->sighand->siglock);
165
166 oval = it->expires;
167 ointerval = it->incr;
168 if (oval || nval) {
169 if (nval > 0)
170 nval += TICK_NSEC;
171 set_process_cpu_timer(tsk, clock_id, &nval, &oval);
172 }
173 it->expires = nval;
174 it->incr = ninterval;
175 trace_itimer_state(clock_id == CPUCLOCK_VIRT ?
176 ITIMER_VIRTUAL : ITIMER_PROF, value, nval);
177
178 spin_unlock_irq(&tsk->sighand->siglock);
179
180 if (ovalue) {
181 ovalue->it_value = ns_to_timeval(oval);
182 ovalue->it_interval = ns_to_timeval(ointerval);
183 }
184}
185
186/*
187 * Returns true if the timeval is in canonical form
188 */
189#define timeval_valid(t) \
190 (((t)->tv_sec >= 0) && (((unsigned long) (t)->tv_usec) < USEC_PER_SEC))
191
192int do_setitimer(int which, struct itimerval *value, struct itimerval *ovalue)
193{
194 struct task_struct *tsk = current;
195 struct hrtimer *timer;
196 ktime_t expires;
197
198 /*
199 * Validate the timevals in value.
200 */
201 if (!timeval_valid(&value->it_value) ||
202 !timeval_valid(&value->it_interval))
203 return -EINVAL;
204
205 switch (which) {
206 case ITIMER_REAL:
207again:
208 spin_lock_irq(&tsk->sighand->siglock);
209 timer = &tsk->signal->real_timer;
210 if (ovalue) {
211 ovalue->it_value = itimer_get_remtime(timer);
212 ovalue->it_interval
213 = ktime_to_timeval(tsk->signal->it_real_incr);
214 }
215 /* We are sharing ->siglock with it_real_fn() */
216 if (hrtimer_try_to_cancel(timer) < 0) {
217 spin_unlock_irq(&tsk->sighand->siglock);
218 goto again;
219 }
220 expires = timeval_to_ktime(value->it_value);
221 if (expires != 0) {
222 tsk->signal->it_real_incr =
223 timeval_to_ktime(value->it_interval);
224 hrtimer_start(timer, expires, HRTIMER_MODE_REL);
225 } else
226 tsk->signal->it_real_incr = 0;
227
228 trace_itimer_state(ITIMER_REAL, value, 0);
229 spin_unlock_irq(&tsk->sighand->siglock);
230 break;
231 case ITIMER_VIRTUAL:
232 set_cpu_itimer(tsk, CPUCLOCK_VIRT, value, ovalue);
233 break;
234 case ITIMER_PROF:
235 set_cpu_itimer(tsk, CPUCLOCK_PROF, value, ovalue);
236 break;
237 default:
238 return -EINVAL;
239 }
240 return 0;
241}
242
243#ifdef __ARCH_WANT_SYS_ALARM
244
245/**
246 * alarm_setitimer - set alarm in seconds
247 *
248 * @seconds: number of seconds until alarm
249 * 0 disables the alarm
250 *
251 * Returns the remaining time in seconds of a pending timer or 0 when
252 * the timer is not active.
253 *
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.
256 */
257static unsigned int alarm_setitimer(unsigned int seconds)
258{
259 struct itimerval it_new, it_old;
260
261#if BITS_PER_LONG < 64
262 if (seconds > INT_MAX)
263 seconds = INT_MAX;
264#endif
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;
268
269 do_setitimer(ITIMER_REAL, &it_new, &it_old);
270
271 /*
272 * We can't return 0 if we have an alarm pending ... And we'd
273 * better return too much than too little anyway
274 */
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++;
278
279 return it_old.it_value.tv_sec;
280}
281
282/*
283 * For backwards compatibility? This can be done in libc so Alpha
284 * and all newer ports shouldn't need it.
285 */
286SYSCALL_DEFINE1(alarm, unsigned int, seconds)
287{
288 return alarm_setitimer(seconds);
289}
290
291#endif
292
293SYSCALL_DEFINE3(setitimer, int, which, struct itimerval __user *, value,
294 struct itimerval __user *, ovalue)
295{
296 struct itimerval set_buffer, get_buffer;
297 int error;
298
299 if (value) {
300 if(copy_from_user(&set_buffer, value, sizeof(set_buffer)))
301 return -EFAULT;
302 } else {
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",
306 current->comm);
307 }
308
309 error = do_setitimer(which, &set_buffer, ovalue ? &get_buffer : NULL);
310 if (error || !ovalue)
311 return error;
312
313 if (copy_to_user(ovalue, &get_buffer, sizeof(get_buffer)))
314 return -EFAULT;
315 return 0;
316}
317
318#ifdef CONFIG_COMPAT
319COMPAT_SYSCALL_DEFINE3(setitimer, int, which,
320 struct compat_itimerval __user *, in,
321 struct compat_itimerval __user *, out)
322{
323 struct itimerval kin, kout;
324 int error;
325
326 if (in) {
327 if (get_compat_itimerval(&kin, in))
328 return -EFAULT;
329 } else {
330 memset(&kin, 0, sizeof(kin));
331 }
332
333 error = do_setitimer(which, &kin, out ? &kout : NULL);
334 if (error || !out)
335 return error;
336 if (put_compat_itimerval(out, &kout))
337 return -EFAULT;
338 return 0;
339}
340#endif