kernel/time/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 <linux/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, true);
  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 <= 0)
  38                         rem = NSEC_PER_USEC;
  39         } else
  40                 rem = 0;
  41
  42         return ktime_to_timeval(rem);
  43 }
  44
  45 static void get_cpu_itimer(struct task_struct *tsk, unsigned int clock_id,
  46                            struct itimerval *const value)
  47 {
  48         u64 val, interval;
  49         struct cpu_itimer *it = &tsk->signal->it[clock_id];
  50
  51         spin_lock_irq(&tsk->sighand->siglock);
  52
  53         val = it->expires;
  54         interval = it->incr;
  55         if (val) {
  56                 struct task_cputime cputime;
  57                 u64 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 (val < t)
  67                         /* about to fire */
  68                         val = TICK_NSEC;
  69                 else
  70                         val -= t;
  71         }
  72
  73         spin_unlock_irq(&tsk->sighand->siglock);
  74
  75         value->it_value = ns_to_timeval(val);
  76         value->it_interval = ns_to_timeval(interval);
  77 }
  78
  79 int 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
 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         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
 132 static void set_cpu_itimer(struct task_struct *tsk, unsigned int clock_id,
 133                            const struct itimerval *const value,
 134                            struct itimerval *const ovalue)
 135 {
 136         u64 oval, nval, ointerval, ninterval;
 137         struct cpu_itimer *it = &tsk->signal->it[clock_id];
 138
 139         nval = timeval_to_ns(&value->it_value);
 140         ninterval = timeval_to_ns(&value->it_interval);
 141
 142         spin_lock_irq(&tsk->sighand->siglock);
 143
 144         oval = it->expires;
 145         ointerval = it->incr;
 146         if (oval || nval) {
 147                 if (nval > 0)
 148                         nval += TICK_NSEC;
 149                 set_process_cpu_timer(tsk, clock_id, &nval, &oval);
 150         }
 151         it->expires = nval;
 152         it->incr = ninterval;
 153         trace_itimer_state(clock_id == CPUCLOCK_VIRT ?
 154                            ITIMER_VIRTUAL : ITIMER_PROF, value, nval);
 155
 156         spin_unlock_irq(&tsk->sighand->siglock);
 157
 158         if (ovalue) {
 159                 ovalue->it_value = ns_to_timeval(oval);
 160                 ovalue->it_interval = ns_to_timeval(ointerval);
 161         }
 162 }
 163
 164 /*
 165  * Returns true if the timeval is in canonical form
 166  */
 167 #define timeval_valid(t) \
 168         (((t)->tv_sec >= 0) && (((unsigned long) (t)->tv_usec) < USEC_PER_SEC))
 169
 170 int do_setitimer(int which, struct itimerval *value, struct itimerval *ovalue)
 171 {
 172         struct task_struct *tsk = current;
 173         struct hrtimer *timer;
 174         ktime_t expires;
 175
 176         /*
 177          * Validate the timevals in value.
 178          */
 179         if (!timeval_valid(&value->it_value) ||
 180             !timeval_valid(&value->it_interval))
 181                 return -EINVAL;
 182
 183         switch (which) {
 184         case ITIMER_REAL:
 185 again:
 186                 spin_lock_irq(&tsk->sighand->siglock);
 187                 timer = &tsk->signal->real_timer;
 188                 if (ovalue) {
 189                         ovalue->it_value = itimer_get_remtime(timer);
 190                         ovalue->it_interval
 191                                 = ktime_to_timeval(tsk->signal->it_real_incr);
 192                 }
 193                 /* We are sharing ->siglock with it_real_fn() */
 194                 if (hrtimer_try_to_cancel(timer) < 0) {
 195                         spin_unlock_irq(&tsk->sighand->siglock);
 196                         goto again;
 197                 }
 198                 expires = timeval_to_ktime(value->it_value);
 199                 if (expires != 0) {
 200                         tsk->signal->it_real_incr =
 201                                 timeval_to_ktime(value->it_interval);
 202                         hrtimer_start(timer, expires, HRTIMER_MODE_REL);
 203                 } else
 204                         tsk->signal->it_real_incr = 0;
 205
 206                 trace_itimer_state(ITIMER_REAL, value, 0);
 207                 spin_unlock_irq(&tsk->sighand->siglock);
 208                 break;
 209         case ITIMER_VIRTUAL:
 210                 set_cpu_itimer(tsk, CPUCLOCK_VIRT, value, ovalue);
 211                 break;
 212         case ITIMER_PROF:
 213                 set_cpu_itimer(tsk, CPUCLOCK_PROF, value, ovalue);
 214                 break;
 215         default:
 216                 return -EINVAL;
 217         }
 218         return 0;
 219 }
 220
 221 #ifdef __ARCH_WANT_SYS_ALARM
 222
 223 /**
 224  * alarm_setitimer - set alarm in seconds
 225  *
 226  * @seconds:    number of seconds until alarm
 227  *              0 disables the alarm
 228  *
 229  * Returns the remaining time in seconds of a pending timer or 0 when
 230  * the timer is not active.
 231  *
 232  * On 32 bit machines the seconds value is limited to (INT_MAX/2) to avoid
 233  * negative timeval settings which would cause immediate expiry.
 234  */
 235 static unsigned int alarm_setitimer(unsigned int seconds)
 236 {
 237         struct itimerval it_new, it_old;
 238
 239 #if BITS_PER_LONG < 64
 240         if (seconds > INT_MAX)
 241                 seconds = INT_MAX;
 242 #endif
 243         it_new.it_value.tv_sec = seconds;
 244         it_new.it_value.tv_usec = 0;
 245         it_new.it_interval.tv_sec = it_new.it_interval.tv_usec = 0;
 246
 247         do_setitimer(ITIMER_REAL, &it_new, &it_old);
 248
 249         /*
 250          * We can't return 0 if we have an alarm pending ...  And we'd
 251          * better return too much than too little anyway
 252          */
 253         if ((!it_old.it_value.tv_sec && it_old.it_value.tv_usec) ||
 254               it_old.it_value.tv_usec >= 500000)
 255                 it_old.it_value.tv_sec++;
 256
 257         return it_old.it_value.tv_sec;
 258 }
 259
 260 /*
 261  * For backwards compatibility?  This can be done in libc so Alpha
 262  * and all newer ports shouldn't need it.
 263  */
 264 SYSCALL_DEFINE1(alarm, unsigned int, seconds)
 265 {
 266         return alarm_setitimer(seconds);
 267 }
 268
 269 #endif
 270
 271 SYSCALL_DEFINE3(setitimer, int, which, struct itimerval __user *, value,
 272                 struct itimerval __user *, ovalue)
 273 {
 274         struct itimerval set_buffer, get_buffer;
 275         int error;
 276
 277         if (value) {
 278                 if(copy_from_user(&set_buffer, value, sizeof(set_buffer)))
 279                         return -EFAULT;
 280         } else {
 281                 memset(&set_buffer, 0, sizeof(set_buffer));
 282                 printk_once(KERN_WARNING "%s calls setitimer() with new_value NULL pointer."
 283                             " Misfeature support will be removed\n",
 284                             current->comm);
 285         }
 286
 287         error = do_setitimer(which, &set_buffer, ovalue ? &get_buffer : NULL);
 288         if (error || !ovalue)
 289                 return error;
 290
 291         if (copy_to_user(ovalue, &get_buffer, sizeof(get_buffer)))
 292                 return -EFAULT;
 293         return 0;
 294 }