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