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
  13 #include <asm/uaccess.h>
  14
  15 /*
  16  * change timeval to jiffies, trying to avoid the
  17  * most obvious overflows..
  18  *
  19  * The tv_*sec values are signed, but nothing seems to
  20  * indicate whether we really should use them as signed values
  21  * when doing itimers. POSIX doesn't mention this (but if
  22  * alarm() uses itimers without checking, we have to use unsigned
  23  * arithmetic).
  24  */
  25 static unsigned long tvtojiffies(struct timeval *value)
  26 {
  27         unsigned long sec = (unsigned) value->tv_sec;
  28         unsigned long usec = (unsigned) value->tv_usec;
  29
  30         if (sec > (ULONG_MAX / HZ))
  31                 return ULONG_MAX;
  32         usec += 1000000 / HZ - 1;
  33         usec /= 1000000 / HZ;
  34         return HZ*sec+usec;
  35 }
  36
  37 static void jiffiestotv(unsigned long jiffies, struct timeval *value)
  38 {
  39         value->tv_usec = (jiffies % HZ) * (1000000 / HZ);
  40         value->tv_sec = jiffies / HZ;
  41 }
  42
  43 int do_getitimer(int which, struct itimerval *value)
  44 {
  45         register unsigned long val, interval;
  46
  47         switch (which) {
  48         case ITIMER_REAL:
  49                 interval = current->it_real_incr;
  50                 val = 0;
  51                 /*
  52                  * FIXME! This needs to be atomic, in case the kernel timer happens!
  53                  */
  54                 if (timer_pending(&current->real_timer)) {
  55                         val = current->real_timer.expires - jiffies;
  56
  57                         /* look out for negative/zero itimer.. */
  58                         if ((long) val <= 0)
  59                                 val = 1;
  60                 }
  61                 break;
  62         case ITIMER_VIRTUAL:
  63                 val = current->it_virt_value;
  64                 interval = current->it_virt_incr;
  65                 break;
  66         case ITIMER_PROF:
  67                 val = current->it_prof_value;
  68                 interval = current->it_prof_incr;
  69                 break;
  70         default:
  71                 return(-EINVAL);
  72         }
  73         jiffiestotv(val, &value->it_value);
  74         jiffiestotv(interval, &value->it_interval);
  75         return 0;
  76 }
  77
  78 /* SMP: Only we modify our itimer values. */
  79 asmlinkage long sys_getitimer(int which, struct itimerval *value)
  80 {
  81         int error = -EFAULT;
  82         struct itimerval get_buffer;
  83
  84         if (value) {
  85                 error = do_getitimer(which, &get_buffer);
  86                 if (!error &&
  87                     copy_to_user(value, &get_buffer, sizeof(get_buffer)))
  88                         error = -EFAULT;
  89         }
  90         return error;
  91 }
  92
  93 void it_real_fn(unsigned long __data)
  94 {
  95         struct task_struct * p = (struct task_struct *) __data;
  96         unsigned long interval;
  97
  98         send_sig(SIGALRM, p, 1);
  99         interval = p->it_real_incr;
 100         if (interval) {
 101                 if (interval > (unsigned long) LONG_MAX)
 102                         interval = LONG_MAX;
 103                 p->real_timer.expires = jiffies + interval;
 104                 add_timer(&p->real_timer);
 105         }
 106 }
 107
 108 int do_setitimer(int which, struct itimerval *value, struct itimerval *ovalue)
 109 {
 110         register unsigned long i, j;
 111         int k;
 112
 113         i = tvtojiffies(&value->it_interval);
 114         j = tvtojiffies(&value->it_value);
 115         if (ovalue && (k = do_getitimer(which, ovalue)) < 0)
 116                 return k;
 117         switch (which) {
 118                 case ITIMER_REAL:
 119                         del_timer_sync(&current->real_timer);
 120                         current->it_real_value = j;
 121                         current->it_real_incr = i;
 122                         if (!j)
 123                                 break;
 124                         if (j > (unsigned long) LONG_MAX)
 125                                 j = LONG_MAX;
 126                         i = j + jiffies;
 127                         current->real_timer.expires = i;
 128                         add_timer(&current->real_timer);
 129                         break;
 130                 case ITIMER_VIRTUAL:
 131                         if (j)
 132                                 j++;
 133                         current->it_virt_value = j;
 134                         current->it_virt_incr = i;
 135                         break;
 136                 case ITIMER_PROF:
 137                         if (j)
 138                                 j++;
 139                         current->it_prof_value = j;
 140                         current->it_prof_incr = i;
 141                         break;
 142                 default:
 143                         return -EINVAL;
 144         }
 145         return 0;
 146 }
 147
 148 /* SMP: Again, only we play with our itimers, and signals are SMP safe
 149  *      now so that is not an issue at all anymore.
 150  */
 151 asmlinkage long sys_setitimer(int which, struct itimerval *value,
 152                               struct itimerval *ovalue)
 153 {
 154         struct itimerval set_buffer, get_buffer;
 155         int error;
 156
 157         if (value) {
 158                 if(copy_from_user(&set_buffer, value, sizeof(set_buffer)))
 159                         return -EFAULT;
 160         } else
 161                 memset((char *) &set_buffer, 0, sizeof(set_buffer));
 162
 163         error = do_setitimer(which, &set_buffer, ovalue ? &get_buffer : 0);
 164         if (error || !ovalue)
 165                 return error;
 166
 167         if (copy_to_user(ovalue, &get_buffer, sizeof(get_buffer)))
 168                 return -EFAULT;
 169         return 0;
 170 }