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 (!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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