Root/kernel/itimer.c

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 */
27static struct timeval itimer_get_remtime(struct hrtimer *timer)
28{
29    ktime_t rem = hrtimer_get_remaining(timer);
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
45static 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 (!cputime_eq(cval, cputime_zero)) {
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_add(cputime.utime, cputime.stime);
62        else
63            /* CPUCLOCK_VIRT */
64            t = cputime.utime;
65
66        if (cputime_le(cval, t))
67            /* about to fire */
68            cval = cputime_one_jiffy;
69        else
70            cval = cputime_sub(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
79int 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
103SYSCALL_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 */
121enum 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
132static 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
143static 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 (!cputime_eq(cval, cputime_zero) ||
165        !cputime_eq(nval, cputime_zero)) {
166        if (cputime_gt(nval, cputime_zero))
167            nval = cputime_add(nval, cputime_one_jiffy);
168        set_process_cpu_timer(tsk, clock_id, &nval, &cval);
169    }
170    it->expires = nval;
171    it->incr = ninterval;
172    it->error = error;
173    it->incr_error = incr_error;
174    trace_itimer_state(clock_id == CPUCLOCK_VIRT ?
175               ITIMER_VIRTUAL : ITIMER_PROF, value, nval);
176
177    spin_unlock_irq(&tsk->sighand->siglock);
178
179    if (ovalue) {
180        cputime_to_timeval(cval, &ovalue->it_value);
181        cputime_to_timeval(cinterval, &ovalue->it_interval);
182    }
183}
184
185/*
186 * Returns true if the timeval is in canonical form
187 */
188#define timeval_valid(t) \
189    (((t)->tv_sec >= 0) && (((unsigned long) (t)->tv_usec) < USEC_PER_SEC))
190
191int do_setitimer(int which, struct itimerval *value, struct itimerval *ovalue)
192{
193    struct task_struct *tsk = current;
194    struct hrtimer *timer;
195    ktime_t expires;
196
197    /*
198     * Validate the timevals in value.
199     */
200    if (!timeval_valid(&value->it_value) ||
201        !timeval_valid(&value->it_interval))
202        return -EINVAL;
203
204    switch (which) {
205    case ITIMER_REAL:
206again:
207        spin_lock_irq(&tsk->sighand->siglock);
208        timer = &tsk->signal->real_timer;
209        if (ovalue) {
210            ovalue->it_value = itimer_get_remtime(timer);
211            ovalue->it_interval
212                = ktime_to_timeval(tsk->signal->it_real_incr);
213        }
214        /* We are sharing ->siglock with it_real_fn() */
215        if (hrtimer_try_to_cancel(timer) < 0) {
216            spin_unlock_irq(&tsk->sighand->siglock);
217            goto again;
218        }
219        expires = timeval_to_ktime(value->it_value);
220        if (expires.tv64 != 0) {
221            tsk->signal->it_real_incr =
222                timeval_to_ktime(value->it_interval);
223            hrtimer_start(timer, expires, HRTIMER_MODE_REL);
224        } else
225            tsk->signal->it_real_incr.tv64 = 0;
226
227        trace_itimer_state(ITIMER_REAL, value, 0);
228        spin_unlock_irq(&tsk->sighand->siglock);
229        break;
230    case ITIMER_VIRTUAL:
231        set_cpu_itimer(tsk, CPUCLOCK_VIRT, value, ovalue);
232        break;
233    case ITIMER_PROF:
234        set_cpu_itimer(tsk, CPUCLOCK_PROF, value, ovalue);
235        break;
236    default:
237        return -EINVAL;
238    }
239    return 0;
240}
241
242/**
243 * alarm_setitimer - set alarm in seconds
244 *
245 * @seconds: number of seconds until alarm
246 * 0 disables the alarm
247 *
248 * Returns the remaining time in seconds of a pending timer or 0 when
249 * the timer is not active.
250 *
251 * On 32 bit machines the seconds value is limited to (INT_MAX/2) to avoid
252 * negative timeval settings which would cause immediate expiry.
253 */
254unsigned int alarm_setitimer(unsigned int seconds)
255{
256    struct itimerval it_new, it_old;
257
258#if BITS_PER_LONG < 64
259    if (seconds > INT_MAX)
260        seconds = INT_MAX;
261#endif
262    it_new.it_value.tv_sec = seconds;
263    it_new.it_value.tv_usec = 0;
264    it_new.it_interval.tv_sec = it_new.it_interval.tv_usec = 0;
265
266    do_setitimer(ITIMER_REAL, &it_new, &it_old);
267
268    /*
269     * We can't return 0 if we have an alarm pending ... And we'd
270     * better return too much than too little anyway
271     */
272    if ((!it_old.it_value.tv_sec && it_old.it_value.tv_usec) ||
273          it_old.it_value.tv_usec >= 500000)
274        it_old.it_value.tv_sec++;
275
276    return it_old.it_value.tv_sec;
277}
278
279SYSCALL_DEFINE3(setitimer, int, which, struct itimerval __user *, value,
280        struct itimerval __user *, ovalue)
281{
282    struct itimerval set_buffer, get_buffer;
283    int error;
284
285    if (value) {
286        if(copy_from_user(&set_buffer, value, sizeof(set_buffer)))
287            return -EFAULT;
288    } else
289        memset((char *) &set_buffer, 0, sizeof(set_buffer));
290
291    error = do_setitimer(which, &set_buffer, ovalue ? &get_buffer : NULL);
292    if (error || !ovalue)
293        return error;
294
295    if (copy_to_user(ovalue, &get_buffer, sizeof(get_buffer)))
296        return -EFAULT;
297    return 0;
298}
299

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