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/smp_lock.h>
  11 #include <linux/interrupt.h>
  12 #include <linux/syscalls.h>
  13 #include <linux/time.h>
  14 #include <linux/posix-timers.h>
  15 #include <linux/hrtimer.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  */
  27 static 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
  45 int do_getitimer(int which, struct itimerval *value)
  46 {
  47         struct task_struct *tsk = current;
  48         cputime_t cinterval, cval;
  49
  50         switch (which) {
  51         case ITIMER_REAL:
  52                 spin_lock_irq(&tsk->sighand->siglock);
  53                 value->it_value = itimer_get_remtime(&tsk->signal->real_timer);
  54                 value->it_interval =
  55                         ktime_to_timeval(tsk->signal->it_real_incr);
  56                 spin_unlock_irq(&tsk->sighand->siglock);
  57                 break;
  58         case ITIMER_VIRTUAL:
  59                 read_lock(&tasklist_lock);
  60                 spin_lock_irq(&tsk->sighand->siglock);
  61                 cval = tsk->signal->it_virt_expires;
  62                 cinterval = tsk->signal->it_virt_incr;
  63                 if (!cputime_eq(cval, cputime_zero)) {
  64                         struct task_struct *t = tsk;
  65                         cputime_t utime = tsk->signal->utime;
  66                         do {
  67                                 utime = cputime_add(utime, t->utime);
  68                                 t = next_thread(t);
  69                         } while (t != tsk);
  70                         if (cputime_le(cval, utime)) { /* about to fire */
  71                                 cval = jiffies_to_cputime(1);
  72                         } else {
  73                                 cval = cputime_sub(cval, utime);
  74                         }
  75                 }
  76                 spin_unlock_irq(&tsk->sighand->siglock);
  77                 read_unlock(&tasklist_lock);
  78                 cputime_to_timeval(cval, &value->it_value);
  79                 cputime_to_timeval(cinterval, &value->it_interval);
  80                 break;
  81         case ITIMER_PROF:
  82                 read_lock(&tasklist_lock);
  83                 spin_lock_irq(&tsk->sighand->siglock);
  84                 cval = tsk->signal->it_prof_expires;
  85                 cinterval = tsk->signal->it_prof_incr;
  86                 if (!cputime_eq(cval, cputime_zero)) {
  87                         struct task_struct *t = tsk;
  88                         cputime_t ptime = cputime_add(tsk->signal->utime,
  89                                                       tsk->signal->stime);
  90                         do {
  91                                 ptime = cputime_add(ptime,
  92                                                     cputime_add(t->utime,
  93                                                                 t->stime));
  94                                 t = next_thread(t);
  95                         } while (t != tsk);
  96                         if (cputime_le(cval, ptime)) { /* about to fire */
  97                                 cval = jiffies_to_cputime(1);
  98                         } else {
  99                                 cval = cputime_sub(cval, ptime);
 100                         }
 101                 }
 102                 spin_unlock_irq(&tsk->sighand->siglock);
 103                 read_unlock(&tasklist_lock);
 104                 cputime_to_timeval(cval, &value->it_value);
 105                 cputime_to_timeval(cinterval, &value->it_interval);
 106                 break;
 107         default:
 108                 return(-EINVAL);
 109         }
 110         return 0;
 111 }
 112
 113 asmlinkage long sys_getitimer(int which, struct itimerval __user *value)
 114 {
 115         int error = -EFAULT;
 116         struct itimerval get_buffer;
 117
 118         if (value) {
 119                 error = do_getitimer(which, &get_buffer);
 120                 if (!error &&
 121                     copy_to_user(value, &get_buffer, sizeof(get_buffer)))
 122                         error = -EFAULT;
 123         }
 124         return error;
 125 }
 126
 127
 128 /*
 129  * The timer is automagically restarted, when interval != 0
 130  */
 131 int it_real_fn(struct hrtimer *timer)
 132 {
 133         struct signal_struct *sig =
 134             container_of(timer, struct signal_struct, real_timer);
 135
 136         send_group_sig_info(SIGALRM, SEND_SIG_PRIV, sig->tsk);
 137
 138         if (sig->it_real_incr.tv64 != 0) {
 139                 hrtimer_forward(timer, timer->base->softirq_time,
 140                                 sig->it_real_incr);
 141                 return HRTIMER_RESTART;
 142         }
 143         return HRTIMER_NORESTART;
 144 }
 145
 146 /*
 147  * We do not care about correctness. We just sanitize the values so
 148  * the ktime_t operations which expect normalized values do not
 149  * break. This converts negative values to long timeouts similar to
 150  * the code in kernel versions < 2.6.16
 151  *
 152  * Print a limited number of warning messages when an invalid timeval
 153  * is detected.
 154  */
 155 static void fixup_timeval(struct timeval *tv, int interval)
 156 {
 157         static int warnlimit = 10;
 158         unsigned long tmp;
 159
 160         if (warnlimit > 0) {
 161                 warnlimit--;
 162                 printk(KERN_WARNING
 163                        "setitimer: %s (pid = %d) provided "
 164                        "invalid timeval %s: tv_sec = %ld tv_usec = %ld\n",
 165                        current->comm, current->pid,
 166                        interval ? "it_interval" : "it_value",
 167                        tv->tv_sec, (long) tv->tv_usec);
 168         }
 169
 170         tmp = tv->tv_usec;
 171         if (tmp >= USEC_PER_SEC) {
 172                 tv->tv_usec = tmp % USEC_PER_SEC;
 173                 tv->tv_sec += tmp / USEC_PER_SEC;
 174         }
 175
 176         tmp = tv->tv_sec;
 177         if (tmp > LONG_MAX)
 178                 tv->tv_sec = LONG_MAX;
 179 }
 180
 181 /*
 182  * Returns true if the timeval is in canonical form
 183  */
 184 #define timeval_valid(t) \
 185         (((t)->tv_sec >= 0) && (((unsigned long) (t)->tv_usec) < USEC_PER_SEC))
 186
 187 /*
 188  * Check for invalid timevals, sanitize them and print a limited
 189  * number of warnings.
 190  */
 191 static void check_itimerval(struct itimerval *value) {
 192
 193         if (unlikely(!timeval_valid(&value->it_value)))
 194                 fixup_timeval(&value->it_value, 0);
 195
 196         if (unlikely(!timeval_valid(&value->it_interval)))
 197                 fixup_timeval(&value->it_interval, 1);
 198 }
 199
 200 int do_setitimer(int which, struct itimerval *value, struct itimerval *ovalue)
 201 {
 202         struct task_struct *tsk = current;
 203         struct hrtimer *timer;
 204         ktime_t expires;
 205         cputime_t cval, cinterval, nval, ninterval;
 206
 207         /*
 208          * Validate the timevals in value.
 209          *
 210          * Note: Although the spec requires that invalid values shall
 211          * return -EINVAL, we just fixup the value and print a limited
 212          * number of warnings in order not to break users of this
 213          * historical misfeature.
 214          *
 215          * Scheduled for replacement in March 2007
 216          */
 217         check_itimerval(value);
 218
 219         switch (which) {
 220         case ITIMER_REAL:
 221 again:
 222                 spin_lock_irq(&tsk->sighand->siglock);
 223                 timer = &tsk->signal->real_timer;
 224                 if (ovalue) {
 225                         ovalue->it_value = itimer_get_remtime(timer);
 226                         ovalue->it_interval
 227                                 = ktime_to_timeval(tsk->signal->it_real_incr);
 228                 }
 229                 /* We are sharing ->siglock with it_real_fn() */
 230                 if (hrtimer_try_to_cancel(timer) < 0) {
 231                         spin_unlock_irq(&tsk->sighand->siglock);
 232                         goto again;
 233                 }
 234                 tsk->signal->it_real_incr =
 235                         timeval_to_ktime(value->it_interval);
 236                 expires = timeval_to_ktime(value->it_value);
 237                 if (expires.tv64 != 0)
 238                         hrtimer_start(timer, expires, HRTIMER_REL);
 239                 spin_unlock_irq(&tsk->sighand->siglock);
 240                 break;
 241         case ITIMER_VIRTUAL:
 242                 nval = timeval_to_cputime(&value->it_value);
 243                 ninterval = timeval_to_cputime(&value->it_interval);
 244                 read_lock(&tasklist_lock);
 245                 spin_lock_irq(&tsk->sighand->siglock);
 246                 cval = tsk->signal->it_virt_expires;
 247                 cinterval = tsk->signal->it_virt_incr;
 248                 if (!cputime_eq(cval, cputime_zero) ||
 249                     !cputime_eq(nval, cputime_zero)) {
 250                         if (cputime_gt(nval, cputime_zero))
 251                                 nval = cputime_add(nval,
 252                                                    jiffies_to_cputime(1));
 253                         set_process_cpu_timer(tsk, CPUCLOCK_VIRT,
 254                                               &nval, &cval);
 255                 }
 256                 tsk->signal->it_virt_expires = nval;
 257                 tsk->signal->it_virt_incr = ninterval;
 258                 spin_unlock_irq(&tsk->sighand->siglock);
 259                 read_unlock(&tasklist_lock);
 260                 if (ovalue) {
 261                         cputime_to_timeval(cval, &ovalue->it_value);
 262                         cputime_to_timeval(cinterval, &ovalue->it_interval);
 263                 }
 264                 break;
 265         case ITIMER_PROF:
 266                 nval = timeval_to_cputime(&value->it_value);
 267                 ninterval = timeval_to_cputime(&value->it_interval);
 268                 read_lock(&tasklist_lock);
 269                 spin_lock_irq(&tsk->sighand->siglock);
 270                 cval = tsk->signal->it_prof_expires;
 271                 cinterval = tsk->signal->it_prof_incr;
 272                 if (!cputime_eq(cval, cputime_zero) ||
 273                     !cputime_eq(nval, cputime_zero)) {
 274                         if (cputime_gt(nval, cputime_zero))
 275                                 nval = cputime_add(nval,
 276                                                    jiffies_to_cputime(1));
 277                         set_process_cpu_timer(tsk, CPUCLOCK_PROF,
 278                                               &nval, &cval);
 279                 }
 280                 tsk->signal->it_prof_expires = nval;
 281                 tsk->signal->it_prof_incr = ninterval;
 282                 spin_unlock_irq(&tsk->sighand->siglock);
 283                 read_unlock(&tasklist_lock);
 284                 if (ovalue) {
 285                         cputime_to_timeval(cval, &ovalue->it_value);
 286                         cputime_to_timeval(cinterval, &ovalue->it_interval);
 287                 }
 288                 break;
 289         default:
 290                 return -EINVAL;
 291         }
 292         return 0;
 293 }
 294
 295 /**
 296  * alarm_setitimer - set alarm in seconds
 297  *
 298  * @seconds:    number of seconds until alarm
 299  *              0 disables the alarm
 300  *
 301  * Returns the remaining time in seconds of a pending timer or 0 when
 302  * the timer is not active.
 303  *
 304  * On 32 bit machines the seconds value is limited to (INT_MAX/2) to avoid
 305  * negative timeval settings which would cause immediate expiry.
 306  */
 307 unsigned int alarm_setitimer(unsigned int seconds)
 308 {
 309         struct itimerval it_new, it_old;
 310
 311 #if BITS_PER_LONG < 64
 312         if (seconds > INT_MAX)
 313                 seconds = INT_MAX;
 314 #endif
 315         it_new.it_value.tv_sec = seconds;
 316         it_new.it_value.tv_usec = 0;
 317         it_new.it_interval.tv_sec = it_new.it_interval.tv_usec = 0;
 318
 319         do_setitimer(ITIMER_REAL, &it_new, &it_old);
 320
 321         /*
 322          * We can't return 0 if we have an alarm pending ...  And we'd
 323          * better return too much than too little anyway
 324          */
 325         if ((!it_old.it_value.tv_sec && it_old.it_value.tv_usec) ||
 326               it_old.it_value.tv_usec >= 500000)
 327                 it_old.it_value.tv_sec++;
 328
 329         return it_old.it_value.tv_sec;
 330 }
 331
 332 asmlinkage long sys_setitimer(int which,
 333                               struct itimerval __user *value,
 334                               struct itimerval __user *ovalue)
 335 {
 336         struct itimerval set_buffer, get_buffer;
 337         int error;
 338
 339         if (value) {
 340                 if(copy_from_user(&set_buffer, value, sizeof(set_buffer)))
 341                         return -EFAULT;
 342         } else
 343                 memset((char *) &set_buffer, 0, sizeof(set_buffer));
 344
 345         error = do_setitimer(which, &set_buffer, ovalue ? &get_buffer : NULL);
 346         if (error || !ovalue)
 347                 return error;
 348
 349         if (copy_to_user(ovalue, &get_buffer, sizeof(get_buffer)))
 350                 return -EFAULT;
 351         return 0;
 352 }