1 /*
2 * linux/kernel/itimer.c
3 *
4 * Copyright (C) 1992 Darren Senn
5 */
6
7 /* These are all the functions necessary to implement itimers */
8
9 #include <linux/mm.h>
10 #include <linux/interrupt.h>
11 #include <linux/syscalls.h>
12 #include <linux/time.h>
13 #include <linux/posix-timers.h>
14 #include <linux/hrtimer.h>
15 #include <trace/events/timer.h>
16
17 #include <asm/uaccess.h>
18
19 /**
20 * itimer_get_remtime - get remaining time for the timer
21 *
22 * @timer: the timer to read
23 *
24 * Returns the delta between the expiry time and now, which can be
25 * less than zero or 1usec for an pending expired timer
26 */
itimer_get_remtime(struct hrtimer * timer)27 static struct timeval itimer_get_remtime(struct hrtimer *timer)
28 {
29 ktime_t rem = __hrtimer_get_remaining(timer, true);
30
31 /*
32 * Racy but safe: if the itimer expires after the above
33 * hrtimer_get_remtime() call but before this condition
34 * then we return 0 - which is correct.
35 */
36 if (hrtimer_active(timer)) {
37 if (rem.tv64 <= 0)
38 rem.tv64 = NSEC_PER_USEC;
39 } else
40 rem.tv64 = 0;
41
42 return ktime_to_timeval(rem);
43 }
44
get_cpu_itimer(struct task_struct * tsk,unsigned int clock_id,struct itimerval * const value)45 static void get_cpu_itimer(struct task_struct *tsk, unsigned int clock_id,
46 struct itimerval *const value)
47 {
48 cputime_t cval, cinterval;
49 struct cpu_itimer *it = &tsk->signal->it[clock_id];
50
51 spin_lock_irq(&tsk->sighand->siglock);
52
53 cval = it->expires;
54 cinterval = it->incr;
55 if (cval) {
56 struct task_cputime cputime;
57 cputime_t t;
58
59 thread_group_cputimer(tsk, &cputime);
60 if (clock_id == CPUCLOCK_PROF)
61 t = cputime.utime + cputime.stime;
62 else
63 /* CPUCLOCK_VIRT */
64 t = cputime.utime;
65
66 if (cval < t)
67 /* about to fire */
68 cval = cputime_one_jiffy;
69 else
70 cval = cval - t;
71 }
72
73 spin_unlock_irq(&tsk->sighand->siglock);
74
75 cputime_to_timeval(cval, &value->it_value);
76 cputime_to_timeval(cinterval, &value->it_interval);
77 }
78
do_getitimer(int which,struct itimerval * value)79 int do_getitimer(int which, struct itimerval *value)
80 {
81 struct task_struct *tsk = current;
82
83 switch (which) {
84 case ITIMER_REAL:
85 spin_lock_irq(&tsk->sighand->siglock);
86 value->it_value = itimer_get_remtime(&tsk->signal->real_timer);
87 value->it_interval =
88 ktime_to_timeval(tsk->signal->it_real_incr);
89 spin_unlock_irq(&tsk->sighand->siglock);
90 break;
91 case ITIMER_VIRTUAL:
92 get_cpu_itimer(tsk, CPUCLOCK_VIRT, value);
93 break;
94 case ITIMER_PROF:
95 get_cpu_itimer(tsk, CPUCLOCK_PROF, value);
96 break;
97 default:
98 return(-EINVAL);
99 }
100 return 0;
101 }
102
SYSCALL_DEFINE2(getitimer,int,which,struct itimerval __user *,value)103 SYSCALL_DEFINE2(getitimer, int, which, struct itimerval __user *, value)
104 {
105 int error = -EFAULT;
106 struct itimerval get_buffer;
107
108 if (value) {
109 error = do_getitimer(which, &get_buffer);
110 if (!error &&
111 copy_to_user(value, &get_buffer, sizeof(get_buffer)))
112 error = -EFAULT;
113 }
114 return error;
115 }
116
117
118 /*
119 * The timer is automagically restarted, when interval != 0
120 */
it_real_fn(struct hrtimer * timer)121 enum hrtimer_restart it_real_fn(struct hrtimer *timer)
122 {
123 struct signal_struct *sig =
124 container_of(timer, struct signal_struct, real_timer);
125
126 trace_itimer_expire(ITIMER_REAL, sig->leader_pid, 0);
127 kill_pid_info(SIGALRM, SEND_SIG_PRIV, sig->leader_pid);
128
129 return HRTIMER_NORESTART;
130 }
131
cputime_sub_ns(cputime_t ct,s64 real_ns)132 static inline u32 cputime_sub_ns(cputime_t ct, s64 real_ns)
133 {
134 struct timespec ts;
135 s64 cpu_ns;
136
137 cputime_to_timespec(ct, &ts);
138 cpu_ns = timespec_to_ns(&ts);
139
140 return (cpu_ns <= real_ns) ? 0 : cpu_ns - real_ns;
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 cputime_t cval, nval, cinterval, ninterval;
148 s64 ns_ninterval, ns_nval;
149 u32 error, incr_error;
150 struct cpu_itimer *it = &tsk->signal->it[clock_id];
151
152 nval = timeval_to_cputime(&value->it_value);
153 ns_nval = timeval_to_ns(&value->it_value);
154 ninterval = timeval_to_cputime(&value->it_interval);
155 ns_ninterval = timeval_to_ns(&value->it_interval);
156
157 error = cputime_sub_ns(nval, ns_nval);
158 incr_error = cputime_sub_ns(ninterval, ns_ninterval);
159
160 spin_lock_irq(&tsk->sighand->siglock);
161
162 cval = it->expires;
163 cinterval = it->incr;
164 if (cval || nval) {
165 if (nval > 0)
166 nval += cputime_one_jiffy;
167 set_process_cpu_timer(tsk, clock_id, &nval, &cval);
168 }
169 it->expires = nval;
170 it->incr = ninterval;
171 it->error = error;
172 it->incr_error = incr_error;
173 trace_itimer_state(clock_id == CPUCLOCK_VIRT ?
174 ITIMER_VIRTUAL : ITIMER_PROF, value, nval);
175
176 spin_unlock_irq(&tsk->sighand->siglock);
177
178 if (ovalue) {
179 cputime_to_timeval(cval, &ovalue->it_value);
180 cputime_to_timeval(cinterval, &ovalue->it_interval);
181 }
182 }
183
184 /*
185 * Returns true if the timeval is in canonical form
186 */
187 #define timeval_valid(t) \
188 (((t)->tv_sec >= 0) && (((unsigned long) (t)->tv_usec) < USEC_PER_SEC))
189
do_setitimer(int which,struct itimerval * value,struct itimerval * ovalue)190 int do_setitimer(int which, struct itimerval *value, struct itimerval *ovalue)
191 {
192 struct task_struct *tsk = current;
193 struct hrtimer *timer;
194 ktime_t expires;
195
196 /*
197 * Validate the timevals in value.
198 */
199 if (!timeval_valid(&value->it_value) ||
200 !timeval_valid(&value->it_interval))
201 return -EINVAL;
202
203 switch (which) {
204 case ITIMER_REAL:
205 again:
206 spin_lock_irq(&tsk->sighand->siglock);
207 timer = &tsk->signal->real_timer;
208 if (ovalue) {
209 ovalue->it_value = itimer_get_remtime(timer);
210 ovalue->it_interval
211 = ktime_to_timeval(tsk->signal->it_real_incr);
212 }
213 /* We are sharing ->siglock with it_real_fn() */
214 if (hrtimer_try_to_cancel(timer) < 0) {
215 spin_unlock_irq(&tsk->sighand->siglock);
216 goto again;
217 }
218 expires = timeval_to_ktime(value->it_value);
219 if (expires.tv64 != 0) {
220 tsk->signal->it_real_incr =
221 timeval_to_ktime(value->it_interval);
222 hrtimer_start(timer, expires, HRTIMER_MODE_REL);
223 } else
224 tsk->signal->it_real_incr.tv64 = 0;
225
226 trace_itimer_state(ITIMER_REAL, value, 0);
227 spin_unlock_irq(&tsk->sighand->siglock);
228 break;
229 case ITIMER_VIRTUAL:
230 set_cpu_itimer(tsk, CPUCLOCK_VIRT, value, ovalue);
231 break;
232 case ITIMER_PROF:
233 set_cpu_itimer(tsk, CPUCLOCK_PROF, value, ovalue);
234 break;
235 default:
236 return -EINVAL;
237 }
238 return 0;
239 }
240
241 /**
242 * alarm_setitimer - set alarm in seconds
243 *
244 * @seconds: number of seconds until alarm
245 * 0 disables the alarm
246 *
247 * Returns the remaining time in seconds of a pending timer or 0 when
248 * the timer is not active.
249 *
250 * On 32 bit machines the seconds value is limited to (INT_MAX/2) to avoid
251 * negative timeval settings which would cause immediate expiry.
252 */
alarm_setitimer(unsigned int seconds)253 unsigned int alarm_setitimer(unsigned int seconds)
254 {
255 struct itimerval it_new, it_old;
256
257 #if BITS_PER_LONG < 64
258 if (seconds > INT_MAX)
259 seconds = INT_MAX;
260 #endif
261 it_new.it_value.tv_sec = seconds;
262 it_new.it_value.tv_usec = 0;
263 it_new.it_interval.tv_sec = it_new.it_interval.tv_usec = 0;
264
265 do_setitimer(ITIMER_REAL, &it_new, &it_old);
266
267 /*
268 * We can't return 0 if we have an alarm pending ... And we'd
269 * better return too much than too little anyway
270 */
271 if ((!it_old.it_value.tv_sec && it_old.it_value.tv_usec) ||
272 it_old.it_value.tv_usec >= 500000)
273 it_old.it_value.tv_sec++;
274
275 return it_old.it_value.tv_sec;
276 }
277
SYSCALL_DEFINE3(setitimer,int,which,struct itimerval __user *,value,struct itimerval __user *,ovalue)278 SYSCALL_DEFINE3(setitimer, int, which, struct itimerval __user *, value,
279 struct itimerval __user *, ovalue)
280 {
281 struct itimerval set_buffer, get_buffer;
282 int error;
283
284 if (value) {
285 if(copy_from_user(&set_buffer, value, sizeof(set_buffer)))
286 return -EFAULT;
287 } else {
288 memset(&set_buffer, 0, sizeof(set_buffer));
289 printk_once(KERN_WARNING "%s calls setitimer() with new_value NULL pointer."
290 " Misfeature support will be removed\n",
291 current->comm);
292 }
293
294 error = do_setitimer(which, &set_buffer, ovalue ? &get_buffer : NULL);
295 if (error || !ovalue)
296 return error;
297
298 if (copy_to_user(ovalue, &get_buffer, sizeof(get_buffer)))
299 return -EFAULT;
300 return 0;
301 }
302