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 */
itimer_get_remtime(struct hrtimer * timer)29 static struct timeval itimer_get_remtime(struct hrtimer *timer)
30 {
31 ktime_t rem = __hrtimer_get_remaining(timer, 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_timeval(rem);
45 }
46
get_cpu_itimer(struct task_struct * tsk,unsigned int clock_id,struct itimerval * const value)47 static void get_cpu_itimer(struct task_struct *tsk, unsigned int clock_id,
48 struct itimerval *const value)
49 {
50 u64 val, interval;
51 struct cpu_itimer *it = &tsk->signal->it[clock_id];
52
53 spin_lock_irq(&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(&tsk->sighand->siglock);
71
72 value->it_value = ns_to_timeval(val);
73 value->it_interval = ns_to_timeval(interval);
74 }
75
do_getitimer(int which,struct itimerval * value)76 int do_getitimer(int which, struct itimerval *value)
77 {
78 struct task_struct *tsk = current;
79
80 switch (which) {
81 case ITIMER_REAL:
82 spin_lock_irq(&tsk->sighand->siglock);
83 value->it_value = itimer_get_remtime(&tsk->signal->real_timer);
84 value->it_interval =
85 ktime_to_timeval(tsk->signal->it_real_incr);
86 spin_unlock_irq(&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
SYSCALL_DEFINE2(getitimer,int,which,struct itimerval __user *,value)100 SYSCALL_DEFINE2(getitimer, int, which, struct itimerval __user *, value)
101 {
102 int error = -EFAULT;
103 struct itimerval get_buffer;
104
105 if (value) {
106 error = do_getitimer(which, &get_buffer);
107 if (!error &&
108 copy_to_user(value, &get_buffer, sizeof(get_buffer)))
109 error = -EFAULT;
110 }
111 return error;
112 }
113
114 #ifdef CONFIG_COMPAT
COMPAT_SYSCALL_DEFINE2(getitimer,int,which,struct compat_itimerval __user *,it)115 COMPAT_SYSCALL_DEFINE2(getitimer, int, which,
116 struct compat_itimerval __user *, it)
117 {
118 struct itimerval kit;
119 int error = do_getitimer(which, &kit);
120
121 if (!error && put_compat_itimerval(it, &kit))
122 error = -EFAULT;
123 return error;
124 }
125 #endif
126
127
128 /*
129 * The timer is automagically restarted, when interval != 0
130 */
it_real_fn(struct hrtimer * timer)131 enum hrtimer_restart it_real_fn(struct hrtimer *timer)
132 {
133 struct signal_struct *sig =
134 container_of(timer, struct signal_struct, real_timer);
135 struct pid *leader_pid = sig->pids[PIDTYPE_TGID];
136
137 trace_itimer_expire(ITIMER_REAL, leader_pid, 0);
138 kill_pid_info(SIGALRM, SEND_SIG_PRIV, leader_pid);
139
140 return HRTIMER_NORESTART;
141 }
142
set_cpu_itimer(struct task_struct * tsk,unsigned int clock_id,const struct itimerval * const value,struct itimerval * const ovalue)143 static void set_cpu_itimer(struct task_struct *tsk, unsigned int clock_id,
144 const struct itimerval *const value,
145 struct itimerval *const ovalue)
146 {
147 u64 oval, nval, ointerval, ninterval;
148 struct cpu_itimer *it = &tsk->signal->it[clock_id];
149
150 /*
151 * Use the to_ktime conversion because that clamps the maximum
152 * value to KTIME_MAX and avoid multiplication overflows.
153 */
154 nval = ktime_to_ns(timeval_to_ktime(value->it_value));
155 ninterval = ktime_to_ns(timeval_to_ktime(value->it_interval));
156
157 spin_lock_irq(&tsk->sighand->siglock);
158
159 oval = it->expires;
160 ointerval = it->incr;
161 if (oval || nval) {
162 if (nval > 0)
163 nval += TICK_NSEC;
164 set_process_cpu_timer(tsk, clock_id, &nval, &oval);
165 }
166 it->expires = nval;
167 it->incr = ninterval;
168 trace_itimer_state(clock_id == CPUCLOCK_VIRT ?
169 ITIMER_VIRTUAL : ITIMER_PROF, value, nval);
170
171 spin_unlock_irq(&tsk->sighand->siglock);
172
173 if (ovalue) {
174 ovalue->it_value = ns_to_timeval(oval);
175 ovalue->it_interval = ns_to_timeval(ointerval);
176 }
177 }
178
179 /*
180 * Returns true if the timeval is in canonical form
181 */
182 #define timeval_valid(t) \
183 (((t)->tv_sec >= 0) && (((unsigned long) (t)->tv_usec) < USEC_PER_SEC))
184
do_setitimer(int which,struct itimerval * value,struct itimerval * ovalue)185 int do_setitimer(int which, struct itimerval *value, struct itimerval *ovalue)
186 {
187 struct task_struct *tsk = current;
188 struct hrtimer *timer;
189 ktime_t expires;
190
191 /*
192 * Validate the timevals in value.
193 */
194 if (!timeval_valid(&value->it_value) ||
195 !timeval_valid(&value->it_interval))
196 return -EINVAL;
197
198 switch (which) {
199 case ITIMER_REAL:
200 again:
201 spin_lock_irq(&tsk->sighand->siglock);
202 timer = &tsk->signal->real_timer;
203 if (ovalue) {
204 ovalue->it_value = itimer_get_remtime(timer);
205 ovalue->it_interval
206 = ktime_to_timeval(tsk->signal->it_real_incr);
207 }
208 /* We are sharing ->siglock with it_real_fn() */
209 if (hrtimer_try_to_cancel(timer) < 0) {
210 spin_unlock_irq(&tsk->sighand->siglock);
211 hrtimer_cancel_wait_running(timer);
212 goto again;
213 }
214 expires = timeval_to_ktime(value->it_value);
215 if (expires != 0) {
216 tsk->signal->it_real_incr =
217 timeval_to_ktime(value->it_interval);
218 hrtimer_start(timer, expires, HRTIMER_MODE_REL);
219 } else
220 tsk->signal->it_real_incr = 0;
221
222 trace_itimer_state(ITIMER_REAL, value, 0);
223 spin_unlock_irq(&tsk->sighand->siglock);
224 break;
225 case ITIMER_VIRTUAL:
226 set_cpu_itimer(tsk, CPUCLOCK_VIRT, value, ovalue);
227 break;
228 case ITIMER_PROF:
229 set_cpu_itimer(tsk, CPUCLOCK_PROF, value, ovalue);
230 break;
231 default:
232 return -EINVAL;
233 }
234 return 0;
235 }
236
237 #ifdef __ARCH_WANT_SYS_ALARM
238
239 /**
240 * alarm_setitimer - set alarm in seconds
241 *
242 * @seconds: number of seconds until alarm
243 * 0 disables the alarm
244 *
245 * Returns the remaining time in seconds of a pending timer or 0 when
246 * the timer is not active.
247 *
248 * On 32 bit machines the seconds value is limited to (INT_MAX/2) to avoid
249 * negative timeval settings which would cause immediate expiry.
250 */
alarm_setitimer(unsigned int seconds)251 static unsigned int alarm_setitimer(unsigned int seconds)
252 {
253 struct itimerval it_new, it_old;
254
255 #if BITS_PER_LONG < 64
256 if (seconds > INT_MAX)
257 seconds = INT_MAX;
258 #endif
259 it_new.it_value.tv_sec = seconds;
260 it_new.it_value.tv_usec = 0;
261 it_new.it_interval.tv_sec = it_new.it_interval.tv_usec = 0;
262
263 do_setitimer(ITIMER_REAL, &it_new, &it_old);
264
265 /*
266 * We can't return 0 if we have an alarm pending ... And we'd
267 * better return too much than too little anyway
268 */
269 if ((!it_old.it_value.tv_sec && it_old.it_value.tv_usec) ||
270 it_old.it_value.tv_usec >= 500000)
271 it_old.it_value.tv_sec++;
272
273 return it_old.it_value.tv_sec;
274 }
275
276 /*
277 * For backwards compatibility? This can be done in libc so Alpha
278 * and all newer ports shouldn't need it.
279 */
SYSCALL_DEFINE1(alarm,unsigned int,seconds)280 SYSCALL_DEFINE1(alarm, unsigned int, seconds)
281 {
282 return alarm_setitimer(seconds);
283 }
284
285 #endif
286
SYSCALL_DEFINE3(setitimer,int,which,struct itimerval __user *,value,struct itimerval __user *,ovalue)287 SYSCALL_DEFINE3(setitimer, int, which, struct itimerval __user *, value,
288 struct itimerval __user *, ovalue)
289 {
290 struct itimerval set_buffer, get_buffer;
291 int error;
292
293 if (value) {
294 if(copy_from_user(&set_buffer, value, sizeof(set_buffer)))
295 return -EFAULT;
296 } else {
297 memset(&set_buffer, 0, sizeof(set_buffer));
298 printk_once(KERN_WARNING "%s calls setitimer() with new_value NULL pointer."
299 " Misfeature support will be removed\n",
300 current->comm);
301 }
302
303 error = do_setitimer(which, &set_buffer, ovalue ? &get_buffer : NULL);
304 if (error || !ovalue)
305 return error;
306
307 if (copy_to_user(ovalue, &get_buffer, sizeof(get_buffer)))
308 return -EFAULT;
309 return 0;
310 }
311
312 #ifdef CONFIG_COMPAT
COMPAT_SYSCALL_DEFINE3(setitimer,int,which,struct compat_itimerval __user *,in,struct compat_itimerval __user *,out)313 COMPAT_SYSCALL_DEFINE3(setitimer, int, which,
314 struct compat_itimerval __user *, in,
315 struct compat_itimerval __user *, out)
316 {
317 struct itimerval kin, kout;
318 int error;
319
320 if (in) {
321 if (get_compat_itimerval(&kin, in))
322 return -EFAULT;
323 } else {
324 memset(&kin, 0, sizeof(kin));
325 }
326
327 error = do_setitimer(which, &kin, out ? &kout : NULL);
328 if (error || !out)
329 return error;
330 if (put_compat_itimerval(out, &kout))
331 return -EFAULT;
332 return 0;
333 }
334 #endif
335