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 (!cputime_eq(cval, cputime_zero)) {
  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_add(cputime.utime, cputime.stime);
  62                 else
  63                         /* CPUCLOCK_VIRT */
  64                         t = cputime.utime;
  65
  66                 if (cputime_le(cval, t))
  67                         /* about to fire */
  68                         cval = cputime_one_jiffy;
  69                 else
  70                         cval = cputime_sub(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 (!cputime_eq(cval, cputime_zero) ||
 165             !cputime_eq(nval, cputime_zero)) {
 166                 if (cputime_gt(nval, cputime_zero))
 167                         nval = cputime_add(nval, cputime_one_jiffy);
 168                 set_process_cpu_timer(tsk, clock_id, &nval, &cval);
 169         }
 170         it->expires = nval;
 171         it->incr = ninterval;
 172         it->error = error;
 173         it->incr_error = incr_error;
 174         trace_itimer_state(clock_id == CPUCLOCK_VIRT ?
 175                            ITIMER_VIRTUAL : ITIMER_PROF, value, nval);
 176
 177         spin_unlock_irq(&tsk->sighand->siglock);
 178
 179         if (ovalue) {
 180                 cputime_to_timeval(cval, &ovalue->it_value);
 181                 cputime_to_timeval(cinterval, &ovalue->it_interval);
 182         }
 183 }
 184
 185 /*
 186  * Returns true if the timeval is in canonical form
 187  */
 188 #define timeval_valid(t) \
 189         (((t)->tv_sec >= 0) && (((unsigned long) (t)->tv_usec) < USEC_PER_SEC))
 190
 191 int do_setitimer(int which, struct itimerval *value, struct itimerval *ovalue)
 192 {
 193         struct task_struct *tsk = current;
 194         struct hrtimer *timer;
 195         ktime_t expires;
 196
 197         /*
 198          * Validate the timevals in value.
 199          */
 200         if (!timeval_valid(&value->it_value) ||
 201             !timeval_valid(&value->it_interval))
 202                 return -EINVAL;
 203
 204         switch (which) {
 205         case ITIMER_REAL:
 206 again:
 207                 spin_lock_irq(&tsk->sighand->siglock);
 208                 timer = &tsk->signal->real_timer;
 209                 if (ovalue) {
 210                         ovalue->it_value = itimer_get_remtime(timer);
 211                         ovalue->it_interval
 212                                 = ktime_to_timeval(tsk->signal->it_real_incr);
 213                 }
 214                 /* We are sharing ->siglock with it_real_fn() */
 215                 if (hrtimer_try_to_cancel(timer) < 0) {
 216                         spin_unlock_irq(&tsk->sighand->siglock);
 217                         goto again;
 218                 }
 219                 expires = timeval_to_ktime(value->it_value);
 220                 if (expires.tv64 != 0) {
 221                         tsk->signal->it_real_incr =
 222                                 timeval_to_ktime(value->it_interval);
 223                         hrtimer_start(timer, expires, HRTIMER_MODE_REL);
 224                 } else
 225                         tsk->signal->it_real_incr.tv64 = 0;
 226
 227                 trace_itimer_state(ITIMER_REAL, value, 0);
 228                 spin_unlock_irq(&tsk->sighand->siglock);
 229                 break;
 230         case ITIMER_VIRTUAL:
 231                 set_cpu_itimer(tsk, CPUCLOCK_VIRT, value, ovalue);
 232                 break;
 233         case ITIMER_PROF:
 234                 set_cpu_itimer(tsk, CPUCLOCK_PROF, value, ovalue);
 235                 break;
 236         default:
 237                 return -EINVAL;
 238         }
 239         return 0;
 240 }
 241
 242 /**
 243  * alarm_setitimer - set alarm in seconds
 244  *
 245  * @seconds:    number of seconds until alarm
 246  *              0 disables the alarm
 247  *
 248  * Returns the remaining time in seconds of a pending timer or 0 when
 249  * the timer is not active.
 250  *
 251  * On 32 bit machines the seconds value is limited to (INT_MAX/2) to avoid
 252  * negative timeval settings which would cause immediate expiry.
 253  */
 254 unsigned int alarm_setitimer(unsigned int seconds)
 255 {
 256         struct itimerval it_new, it_old;
 257
 258 #if BITS_PER_LONG < 64
 259         if (seconds > INT_MAX)
 260                 seconds = INT_MAX;
 261 #endif
 262         it_new.it_value.tv_sec = seconds;
 263         it_new.it_value.tv_usec = 0;
 264         it_new.it_interval.tv_sec = it_new.it_interval.tv_usec = 0;
 265
 266         do_setitimer(ITIMER_REAL, &it_new, &it_old);
 267
 268         /*
 269          * We can't return 0 if we have an alarm pending ...  And we'd
 270          * better return too much than too little anyway
 271          */
 272         if ((!it_old.it_value.tv_sec && it_old.it_value.tv_usec) ||
 273               it_old.it_value.tv_usec >= 500000)
 274                 it_old.it_value.tv_sec++;
 275
 276         return it_old.it_value.tv_sec;
 277 }
 278
 279 SYSCALL_DEFINE3(setitimer, int, which, struct itimerval __user *, value,
 280                 struct itimerval __user *, ovalue)
 281 {
 282         struct itimerval set_buffer, get_buffer;
 283         int error;
 284
 285         if (value) {
 286                 if(copy_from_user(&set_buffer, value, sizeof(set_buffer)))
 287                         return -EFAULT;
 288         } else
 289                 memset((char *) &set_buffer, 0, sizeof(set_buffer));
 290
 291         error = do_setitimer(which, &set_buffer, ovalue ? &get_buffer : NULL);
 292         if (error || !ovalue)
 293                 return error;
 294
 295         if (copy_to_user(ovalue, &get_buffer, sizeof(get_buffer)))
 296                 return -EFAULT;
 297         return 0;
 298 }