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 static void get_cpu_itimer(struct task_struct *tsk, unsigned int clock_id,
  45                            struct itimerval *const value)
  46 {
  47         cputime_t cval, cinterval;
  48         struct cpu_itimer *it = &tsk->signal->it[clock_id];
  49
  50         spin_lock_irq(&tsk->sighand->siglock);
  51
  52         cval = it->expires;
  53         cinterval = it->incr;
  54         if (!cputime_eq(cval, cputime_zero)) {
  55                 struct task_cputime cputime;
  56                 cputime_t t;
  57
  58                 thread_group_cputimer(tsk, &cputime);
  59                 if (clock_id == CPUCLOCK_PROF)
  60                         t = cputime_add(cputime.utime, cputime.stime);
  61                 else
  62                         /* CPUCLOCK_VIRT */
  63                         t = cputime.utime;
  64
  65                 if (cputime_le(cval, t))
  66                         /* about to fire */
  67                         cval = cputime_one_jiffy;
  68                 else
  69                         cval = cputime_sub(cval, t);
  70         }
  71
  72         spin_unlock_irq(&tsk->sighand->siglock);
  73
  74         cputime_to_timeval(cval, &value->it_value);
  75         cputime_to_timeval(cinterval, &value->it_interval);
  76 }
  77
  78 int do_getitimer(int which, struct itimerval *value)
  79 {
  80         struct task_struct *tsk = current;
  81
  82         switch (which) {
  83         case ITIMER_REAL:
  84                 spin_lock_irq(&tsk->sighand->siglock);
  85                 value->it_value = itimer_get_remtime(&tsk->signal->real_timer);
  86                 value->it_interval =
  87                         ktime_to_timeval(tsk->signal->it_real_incr);
  88                 spin_unlock_irq(&tsk->sighand->siglock);
  89                 break;
  90         case ITIMER_VIRTUAL:
  91                 get_cpu_itimer(tsk, CPUCLOCK_VIRT, value);
  92                 break;
  93         case ITIMER_PROF:
  94                 get_cpu_itimer(tsk, CPUCLOCK_PROF, value);
  95                 break;
  96         default:
  97                 return(-EINVAL);
  98         }
  99         return 0;
 100 }
 101
 102 SYSCALL_DEFINE2(getitimer, int, which, struct itimerval __user *, value)
 103 {
 104         int error = -EFAULT;
 105         struct itimerval get_buffer;
 106
 107         if (value) {
 108                 error = do_getitimer(which, &get_buffer);
 109                 if (!error &&
 110                     copy_to_user(value, &get_buffer, sizeof(get_buffer)))
 111                         error = -EFAULT;
 112         }
 113         return error;
 114 }
 115
 116
 117 /*
 118  * The timer is automagically restarted, when interval != 0
 119  */
 120 enum hrtimer_restart it_real_fn(struct hrtimer *timer)
 121 {
 122         struct signal_struct *sig =
 123                 container_of(timer, struct signal_struct, real_timer);
 124
 125         kill_pid_info(SIGALRM, SEND_SIG_PRIV, sig->leader_pid);
 126
 127         return HRTIMER_NORESTART;
 128 }
 129
 130 static inline u32 cputime_sub_ns(cputime_t ct, s64 real_ns)
 131 {
 132         struct timespec ts;
 133         s64 cpu_ns;
 134
 135         cputime_to_timespec(ct, &ts);
 136         cpu_ns = timespec_to_ns(&ts);
 137
 138         return (cpu_ns <= real_ns) ? 0 : cpu_ns - real_ns;
 139 }
 140
 141 static void set_cpu_itimer(struct task_struct *tsk, unsigned int clock_id,
 142                            const struct itimerval *const value,
 143                            struct itimerval *const ovalue)
 144 {
 145         cputime_t cval, nval, cinterval, ninterval;
 146         s64 ns_ninterval, ns_nval;
 147         struct cpu_itimer *it = &tsk->signal->it[clock_id];
 148
 149         nval = timeval_to_cputime(&value->it_value);
 150         ns_nval = timeval_to_ns(&value->it_value);
 151         ninterval = timeval_to_cputime(&value->it_interval);
 152         ns_ninterval = timeval_to_ns(&value->it_interval);
 153
 154         it->incr_error = cputime_sub_ns(ninterval, ns_ninterval);
 155         it->error = cputime_sub_ns(nval, ns_nval);
 156
 157         spin_lock_irq(&tsk->sighand->siglock);
 158
 159         cval = it->expires;
 160         cinterval = it->incr;
 161         if (!cputime_eq(cval, cputime_zero) ||
 162             !cputime_eq(nval, cputime_zero)) {
 163                 if (cputime_gt(nval, cputime_zero))
 164                         nval = cputime_add(nval, cputime_one_jiffy);
 165                 set_process_cpu_timer(tsk, clock_id, &nval, &cval);
 166         }
 167         it->expires = nval;
 168         it->incr = ninterval;
 169
 170         spin_unlock_irq(&tsk->sighand->siglock);
 171
 172         if (ovalue) {
 173                 cputime_to_timeval(cval, &ovalue->it_value);
 174                 cputime_to_timeval(cinterval, &ovalue->it_interval);
 175         }
 176 }
 177
 178 /*
 179  * Returns true if the timeval is in canonical form
 180  */
 181 #define timeval_valid(t) \
 182         (((t)->tv_sec >= 0) && (((unsigned long) (t)->tv_usec) < USEC_PER_SEC))
 183
 184 int do_setitimer(int which, struct itimerval *value, struct itimerval *ovalue)
 185 {
 186         struct task_struct *tsk = current;
 187         struct hrtimer *timer;
 188         ktime_t expires;
 189
 190         /*
 191          * Validate the timevals in value.
 192          */
 193         if (!timeval_valid(&value->it_value) ||
 194             !timeval_valid(&value->it_interval))
 195                 return -EINVAL;
 196
 197         switch (which) {
 198         case ITIMER_REAL:
 199 again:
 200                 spin_lock_irq(&tsk->sighand->siglock);
 201                 timer = &tsk->signal->real_timer;
 202                 if (ovalue) {
 203                         ovalue->it_value = itimer_get_remtime(timer);
 204                         ovalue->it_interval
 205                                 = ktime_to_timeval(tsk->signal->it_real_incr);
 206                 }
 207                 /* We are sharing ->siglock with it_real_fn() */
 208                 if (hrtimer_try_to_cancel(timer) < 0) {
 209                         spin_unlock_irq(&tsk->sighand->siglock);
 210                         goto again;
 211                 }
 212                 expires = timeval_to_ktime(value->it_value);
 213                 if (expires.tv64 != 0) {
 214                         tsk->signal->it_real_incr =
 215                                 timeval_to_ktime(value->it_interval);
 216                         hrtimer_start(timer, expires, HRTIMER_MODE_REL);
 217                 } else
 218                         tsk->signal->it_real_incr.tv64 = 0;
 219
 220                 spin_unlock_irq(&tsk->sighand->siglock);
 221                 break;
 222         case ITIMER_VIRTUAL:
 223                 set_cpu_itimer(tsk, CPUCLOCK_VIRT, value, ovalue);
 224                 break;
 225         case ITIMER_PROF:
 226                 set_cpu_itimer(tsk, CPUCLOCK_PROF, value, ovalue);
 227                 break;
 228         default:
 229                 return -EINVAL;
 230         }
 231         return 0;
 232 }
 233
 234 /**
 235  * alarm_setitimer - set alarm in seconds
 236  *
 237  * @seconds:    number of seconds until alarm
 238  *              0 disables the alarm
 239  *
 240  * Returns the remaining time in seconds of a pending timer or 0 when
 241  * the timer is not active.
 242  *
 243  * On 32 bit machines the seconds value is limited to (INT_MAX/2) to avoid
 244  * negative timeval settings which would cause immediate expiry.
 245  */
 246 unsigned int alarm_setitimer(unsigned int seconds)
 247 {
 248         struct itimerval it_new, it_old;
 249
 250 #if BITS_PER_LONG < 64
 251         if (seconds > INT_MAX)
 252                 seconds = INT_MAX;
 253 #endif
 254         it_new.it_value.tv_sec = seconds;
 255         it_new.it_value.tv_usec = 0;
 256         it_new.it_interval.tv_sec = it_new.it_interval.tv_usec = 0;
 257
 258         do_setitimer(ITIMER_REAL, &it_new, &it_old);
 259
 260         /*
 261          * We can't return 0 if we have an alarm pending ...  And we'd
 262          * better return too much than too little anyway
 263          */
 264         if ((!it_old.it_value.tv_sec && it_old.it_value.tv_usec) ||
 265               it_old.it_value.tv_usec >= 500000)
 266                 it_old.it_value.tv_sec++;
 267
 268         return it_old.it_value.tv_sec;
 269 }
 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((char *) &set_buffer, 0, sizeof(set_buffer));
 282
 283         error = do_setitimer(which, &set_buffer, ovalue ? &get_buffer : NULL);
 284         if (error || !ovalue)
 285                 return error;
 286
 287         if (copy_to_user(ovalue, &get_buffer, sizeof(get_buffer)))
 288                 return -EFAULT;
 289         return 0;
 290 }