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
  16 #include <asm/uaccess.h>
  17
  18 /**
  19  * itimer_get_remtime - get remaining time for the timer
  20  *
  21  * @timer: the timer to read
  22  *
  23  * Returns the delta between the expiry time and now, which can be
  24  * less than zero or 1usec for an pending expired timer
  25  */
  26 static struct timeval itimer_get_remtime(struct hrtimer *timer)
  27 {
  28         ktime_t rem = hrtimer_get_remaining(timer);
  29
  30         /*
  31          * Racy but safe: if the itimer expires after the above
  32          * hrtimer_get_remtime() call but before this condition
  33          * then we return 0 - which is correct.
  34          */
  35         if (hrtimer_active(timer)) {
  36                 if (rem.tv64 <= 0)
  37                         rem.tv64 = NSEC_PER_USEC;
  38         } else
  39                 rem.tv64 = 0;
  40
  41         return ktime_to_timeval(rem);
  42 }
  43
  44 int do_getitimer(int which, struct itimerval *value)
  45 {
  46         struct task_struct *tsk = current;
  47         cputime_t cinterval, cval;
  48
  49         switch (which) {
  50         case ITIMER_REAL:
  51                 spin_lock_irq(&tsk->sighand->siglock);
  52                 value->it_value = itimer_get_remtime(&tsk->signal->real_timer);
  53                 value->it_interval =
  54                         ktime_to_timeval(tsk->signal->it_real_incr);
  55                 spin_unlock_irq(&tsk->sighand->siglock);
  56                 break;
  57         case ITIMER_VIRTUAL:
  58                 spin_lock_irq(&tsk->sighand->siglock);
  59                 cval = tsk->signal->it_virt_expires;
  60                 cinterval = tsk->signal->it_virt_incr;
  61                 if (!cputime_eq(cval, cputime_zero)) {
  62                         struct task_cputime cputime;
  63                         cputime_t utime;
  64
  65                         thread_group_cputime(tsk, &cputime);
  66                         utime = cputime.utime;
  67                         if (cputime_le(cval, utime)) { /* about to fire */
  68                                 cval = jiffies_to_cputime(1);
  69                         } else {
  70                                 cval = cputime_sub(cval, utime);
  71                         }
  72                 }
  73                 spin_unlock_irq(&tsk->sighand->siglock);
  74                 cputime_to_timeval(cval, &value->it_value);
  75                 cputime_to_timeval(cinterval, &value->it_interval);
  76                 break;
  77         case ITIMER_PROF:
  78                 spin_lock_irq(&tsk->sighand->siglock);
  79                 cval = tsk->signal->it_prof_expires;
  80                 cinterval = tsk->signal->it_prof_incr;
  81                 if (!cputime_eq(cval, cputime_zero)) {
  82                         struct task_cputime times;
  83                         cputime_t ptime;
  84
  85                         thread_group_cputime(tsk, &times);
  86                         ptime = cputime_add(times.utime, times.stime);
  87                         if (cputime_le(cval, ptime)) { /* about to fire */
  88                                 cval = jiffies_to_cputime(1);
  89                         } else {
  90                                 cval = cputime_sub(cval, ptime);
  91                         }
  92                 }
  93                 spin_unlock_irq(&tsk->sighand->siglock);
  94                 cputime_to_timeval(cval, &value->it_value);
  95                 cputime_to_timeval(cinterval, &value->it_interval);
  96                 break;
  97         default:
  98                 return(-EINVAL);
  99         }
 100         return 0;
 101 }
 102
 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  */
 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         kill_pid_info(SIGALRM, SEND_SIG_PRIV, sig->leader_pid);
 127
 128         return HRTIMER_NORESTART;
 129 }
 130
 131 /*
 132  * Returns true if the timeval is in canonical form
 133  */
 134 #define timeval_valid(t) \
 135         (((t)->tv_sec >= 0) && (((unsigned long) (t)->tv_usec) < USEC_PER_SEC))
 136
 137 int do_setitimer(int which, struct itimerval *value, struct itimerval *ovalue)
 138 {
 139         struct task_struct *tsk = current;
 140         struct hrtimer *timer;
 141         ktime_t expires;
 142         cputime_t cval, cinterval, nval, ninterval;
 143
 144         /*
 145          * Validate the timevals in value.
 146          */
 147         if (!timeval_valid(&value->it_value) ||
 148             !timeval_valid(&value->it_interval))
 149                 return -EINVAL;
 150
 151         switch (which) {
 152         case ITIMER_REAL:
 153 again:
 154                 spin_lock_irq(&tsk->sighand->siglock);
 155                 timer = &tsk->signal->real_timer;
 156                 if (ovalue) {
 157                         ovalue->it_value = itimer_get_remtime(timer);
 158                         ovalue->it_interval
 159                                 = ktime_to_timeval(tsk->signal->it_real_incr);
 160                 }
 161                 /* We are sharing ->siglock with it_real_fn() */
 162                 if (hrtimer_try_to_cancel(timer) < 0) {
 163                         spin_unlock_irq(&tsk->sighand->siglock);
 164                         goto again;
 165                 }
 166                 expires = timeval_to_ktime(value->it_value);
 167                 if (expires.tv64 != 0) {
 168                         tsk->signal->it_real_incr =
 169                                 timeval_to_ktime(value->it_interval);
 170                         hrtimer_start(timer, expires, HRTIMER_MODE_REL);
 171                 } else
 172                         tsk->signal->it_real_incr.tv64 = 0;
 173
 174                 spin_unlock_irq(&tsk->sighand->siglock);
 175                 break;
 176         case ITIMER_VIRTUAL:
 177                 nval = timeval_to_cputime(&value->it_value);
 178                 ninterval = timeval_to_cputime(&value->it_interval);
 179                 spin_lock_irq(&tsk->sighand->siglock);
 180                 cval = tsk->signal->it_virt_expires;
 181                 cinterval = tsk->signal->it_virt_incr;
 182                 if (!cputime_eq(cval, cputime_zero) ||
 183                     !cputime_eq(nval, cputime_zero)) {
 184                         if (cputime_gt(nval, cputime_zero))
 185                                 nval = cputime_add(nval,
 186                                                    jiffies_to_cputime(1));
 187                         set_process_cpu_timer(tsk, CPUCLOCK_VIRT,
 188                                               &nval, &cval);
 189                 }
 190                 tsk->signal->it_virt_expires = nval;
 191                 tsk->signal->it_virt_incr = ninterval;
 192                 spin_unlock_irq(&tsk->sighand->siglock);
 193                 if (ovalue) {
 194                         cputime_to_timeval(cval, &ovalue->it_value);
 195                         cputime_to_timeval(cinterval, &ovalue->it_interval);
 196                 }
 197                 break;
 198         case ITIMER_PROF:
 199                 nval = timeval_to_cputime(&value->it_value);
 200                 ninterval = timeval_to_cputime(&value->it_interval);
 201                 spin_lock_irq(&tsk->sighand->siglock);
 202                 cval = tsk->signal->it_prof_expires;
 203                 cinterval = tsk->signal->it_prof_incr;
 204                 if (!cputime_eq(cval, cputime_zero) ||
 205                     !cputime_eq(nval, cputime_zero)) {
 206                         if (cputime_gt(nval, cputime_zero))
 207                                 nval = cputime_add(nval,
 208                                                    jiffies_to_cputime(1));
 209                         set_process_cpu_timer(tsk, CPUCLOCK_PROF,
 210                                               &nval, &cval);
 211                 }
 212                 tsk->signal->it_prof_expires = nval;
 213                 tsk->signal->it_prof_incr = ninterval;
 214                 spin_unlock_irq(&tsk->sighand->siglock);
 215                 if (ovalue) {
 216                         cputime_to_timeval(cval, &ovalue->it_value);
 217                         cputime_to_timeval(cinterval, &ovalue->it_interval);
 218                 }
 219                 break;
 220         default:
 221                 return -EINVAL;
 222         }
 223         return 0;
 224 }
 225
 226 /**
 227  * alarm_setitimer - set alarm in seconds
 228  *
 229  * @seconds:    number of seconds until alarm
 230  *              0 disables the alarm
 231  *
 232  * Returns the remaining time in seconds of a pending timer or 0 when
 233  * the timer is not active.
 234  *
 235  * On 32 bit machines the seconds value is limited to (INT_MAX/2) to avoid
 236  * negative timeval settings which would cause immediate expiry.
 237  */
 238 unsigned int alarm_setitimer(unsigned int seconds)
 239 {
 240         struct itimerval it_new, it_old;
 241
 242 #if BITS_PER_LONG < 64
 243         if (seconds > INT_MAX)
 244                 seconds = INT_MAX;
 245 #endif
 246         it_new.it_value.tv_sec = seconds;
 247         it_new.it_value.tv_usec = 0;
 248         it_new.it_interval.tv_sec = it_new.it_interval.tv_usec = 0;
 249
 250         do_setitimer(ITIMER_REAL, &it_new, &it_old);
 251
 252         /*
 253          * We can't return 0 if we have an alarm pending ...  And we'd
 254          * better return too much than too little anyway
 255          */
 256         if ((!it_old.it_value.tv_sec && it_old.it_value.tv_usec) ||
 257               it_old.it_value.tv_usec >= 500000)
 258                 it_old.it_value.tv_sec++;
 259
 260         return it_old.it_value.tv_sec;
 261 }
 262
 263 SYSCALL_DEFINE3(setitimer, int, which, struct itimerval __user *, value,
 264                 struct itimerval __user *, ovalue)
 265 {
 266         struct itimerval set_buffer, get_buffer;
 267         int error;
 268
 269         if (value) {
 270                 if(copy_from_user(&set_buffer, value, sizeof(set_buffer)))
 271                         return -EFAULT;
 272         } else
 273                 memset((char *) &set_buffer, 0, sizeof(set_buffer));
 274
 275         error = do_setitimer(which, &set_buffer, ovalue ? &get_buffer : NULL);
 276         if (error || !ovalue)
 277                 return error;
 278
 279         if (copy_to_user(ovalue, &get_buffer, sizeof(get_buffer)))
 280                 return -EFAULT;
 281         return 0;
 282 }