linux/kernel/itimer.c
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   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 (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
  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 (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
 190int 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:
 205again:
 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 */
 253unsigned 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
 278SYSCALL_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
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