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 #include <trace/events/timer.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 static void get_cpu_itimer(struct task_struct *tsk, unsigned int clock_id,
  46                            struct itimerval *const value)
  47 {
  48         cputime_t cval, cinterval;
  49         struct cpu_itimer *it = &tsk->signal->it[clock_id];
  50
  51         spin_lock_irq(&tsk->sighand->siglock);
  52
  53         cval = it->expires;
  54         cinterval = it->incr;
  55         if (cval) {
  56                 struct task_cputime cputime;
  57                 cputime_t 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 (cval < t)
  67                         /* about to fire */
  68                         cval = cputime_one_jiffy;
  69                 else
  70                         cval = cval - t;
  71         }
  72
  73         spin_unlock_irq(&tsk->sighand->siglock);
  74
  75         cputime_to_timeval(cval, &value->it_value);
  76         cputime_to_timeval(cinterval, &value->it_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 inline u32 cputime_sub_ns(cputime_t ct, s64 real_ns)
 133 {
 134         struct timespec ts;
 135         s64 cpu_ns;
 136
 137         cputime_to_timespec(ct, &ts);
 138         cpu_ns = timespec_to_ns(&ts);
 139
 140         return (cpu_ns <= real_ns) ? 0 : cpu_ns - real_ns;
 141 }
 142
 143 static void set_cpu_itimer(struct task_struct *tsk, unsigned int clock_id,
 144                            const struct itimerval *const value,
 145                            struct itimerval *const ovalue)
 146 {
 147         cputime_t cval, nval, cinterval, ninterval;
 148         s64 ns_ninterval, ns_nval;
 149         u32 error, incr_error;
 150         struct cpu_itimer *it = &tsk->signal->it[clock_id];
 151
 152         nval = timeval_to_cputime(&value->it_value);
 153         ns_nval = timeval_to_ns(&value->it_value);
 154         ninterval = timeval_to_cputime(&value->it_interval);
 155         ns_ninterval = timeval_to_ns(&value->it_interval);
 156
 157         error = cputime_sub_ns(nval, ns_nval);
 158         incr_error = cputime_sub_ns(ninterval, ns_ninterval);
 159
 160         spin_lock_irq(&tsk->sighand->siglock);
 161
 162         cval = it->expires;
 163         cinterval = it->incr;
 164         if (cval || nval) {
 165                 if (nval > 0)
 166                         nval += cputime_one_jiffy;
 167                 set_process_cpu_timer(tsk, clock_id, &nval, &cval);
 168         }
 169         it->expires = nval;
 170         it->incr = ninterval;
 171         it->error = error;
 172         it->incr_error = incr_error;
 173         trace_itimer_state(clock_id == CPUCLOCK_VIRT ?
 174                            ITIMER_VIRTUAL : ITIMER_PROF, value, nval);
 175
 176         spin_unlock_irq(&tsk->sighand->siglock);
 177
 178         if (ovalue) {
 179                 cputime_to_timeval(cval, &ovalue->it_value);
 180                 cputime_to_timeval(cinterval, &ovalue->it_interval);
 181         }
 182 }
 183
 184 /*
 185  * Returns true if the timeval is in canonical form
 186  */
 187 #define timeval_valid(t) \
 188         (((t)->tv_sec >= 0) && (((unsigned long) (t)->tv_usec) < USEC_PER_SEC))
 189
 190 int do_setitimer(int which, struct itimerval *value, struct itimerval *ovalue)
 191 {
 192         struct task_struct *tsk = current;
 193         struct hrtimer *timer;
 194         ktime_t expires;
 195
 196         /*
 197          * Validate the timevals in value.
 198          */
 199         if (!timeval_valid(&value->it_value) ||
 200             !timeval_valid(&value->it_interval))
 201                 return -EINVAL;
 202
 203         switch (which) {
 204         case ITIMER_REAL:
 205 again:
 206                 spin_lock_irq(&tsk->sighand->siglock);
 207                 timer = &tsk->signal->real_timer;
 208                 if (ovalue) {
 209                         ovalue->it_value = itimer_get_remtime(timer);
 210                         ovalue->it_interval
 211                                 = ktime_to_timeval(tsk->signal->it_real_incr);
 212                 }
 213                 /* We are sharing ->siglock with it_real_fn() */
 214                 if (hrtimer_try_to_cancel(timer) < 0) {
 215                         spin_unlock_irq(&tsk->sighand->siglock);
 216                         goto again;
 217                 }
 218                 expires = timeval_to_ktime(value->it_value);
 219                 if (expires.tv64 != 0) {
 220                         tsk->signal->it_real_incr =
 221                                 timeval_to_ktime(value->it_interval);
 222                         hrtimer_start(timer, expires, HRTIMER_MODE_REL);
 223                 } else
 224                         tsk->signal->it_real_incr.tv64 = 0;
 225
 226                 trace_itimer_state(ITIMER_REAL, value, 0);
 227                 spin_unlock_irq(&tsk->sighand->siglock);
 228                 break;
 229         case ITIMER_VIRTUAL:
 230                 set_cpu_itimer(tsk, CPUCLOCK_VIRT, value, ovalue);
 231                 break;
 232         case ITIMER_PROF:
 233                 set_cpu_itimer(tsk, CPUCLOCK_PROF, value, ovalue);
 234                 break;
 235         default:
 236                 return -EINVAL;
 237         }
 238         return 0;
 239 }
 240
 241 /**
 242  * alarm_setitimer - set alarm in seconds
 243  *
 244  * @seconds:    number of seconds until alarm
 245  *              0 disables the alarm
 246  *
 247  * Returns the remaining time in seconds of a pending timer or 0 when
 248  * the timer is not active.
 249  *
 250  * On 32 bit machines the seconds value is limited to (INT_MAX/2) to avoid
 251  * negative timeval settings which would cause immediate expiry.
 252  */
 253 unsigned int alarm_setitimer(unsigned int seconds)
 254 {
 255         struct itimerval it_new, it_old;
 256
 257 #if BITS_PER_LONG < 64
 258         if (seconds > INT_MAX)
 259                 seconds = INT_MAX;
 260 #endif
 261         it_new.it_value.tv_sec = seconds;
 262         it_new.it_value.tv_usec = 0;
 263         it_new.it_interval.tv_sec = it_new.it_interval.tv_usec = 0;
 264
 265         do_setitimer(ITIMER_REAL, &it_new, &it_old);
 266
 267         /*
 268          * We can't return 0 if we have an alarm pending ...  And we'd
 269          * better return too much than too little anyway
 270          */
 271         if ((!it_old.it_value.tv_sec && it_old.it_value.tv_usec) ||
 272               it_old.it_value.tv_usec >= 500000)
 273                 it_old.it_value.tv_sec++;
 274
 275         return it_old.it_value.tv_sec;
 276 }
 277
 278 SYSCALL_DEFINE3(setitimer, int, which, struct itimerval __user *, value,
 279                 struct itimerval __user *, ovalue)
 280 {
 281         struct itimerval set_buffer, get_buffer;
 282         int error;
 283
 284         if (value) {
 285                 if(copy_from_user(&set_buffer, value, sizeof(set_buffer)))
 286                         return -EFAULT;
 287         } else
 288                 memset((char *) &set_buffer, 0, sizeof(set_buffer));
 289
 290         error = do_setitimer(which, &set_buffer, ovalue ? &get_buffer : NULL);
 291         if (error || !ovalue)
 292                 return error;
 293
 294         if (copy_to_user(ovalue, &get_buffer, sizeof(get_buffer)))
 295                 return -EFAULT;
 296         return 0;
 297 }