kernel/time/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/sched/signal.h>
  14 #include <linux/sched/cputime.h>
  15 #include <linux/posix-timers.h>
  16 #include <linux/hrtimer.h>
  17 #include <trace/events/timer.h>
  18
  19 #include <linux/uaccess.h>
  20
  21 /**
  22  * itimer_get_remtime - get remaining time for the timer
  23  *
  24  * @timer: the timer to read
  25  *
  26  * Returns the delta between the expiry time and now, which can be
  27  * less than zero or 1usec for an pending expired timer
  28  */
  29 static struct timeval itimer_get_remtime(struct hrtimer *timer)
  30 {
  31         ktime_t rem = __hrtimer_get_remaining(timer, true);
  32
  33         /*
  34          * Racy but safe: if the itimer expires after the above
  35          * hrtimer_get_remtime() call but before this condition
  36          * then we return 0 - which is correct.
  37          */
  38         if (hrtimer_active(timer)) {
  39                 if (rem <= 0)
  40                         rem = NSEC_PER_USEC;
  41         } else
  42                 rem = 0;
  43
  44         return ktime_to_timeval(rem);
  45 }
  46
  47 static void get_cpu_itimer(struct task_struct *tsk, unsigned int clock_id,
  48                            struct itimerval *const value)
  49 {
  50         u64 val, interval;
  51         struct cpu_itimer *it = &tsk->signal->it[clock_id];
  52
  53         spin_lock_irq(&tsk->sighand->siglock);
  54
  55         val = it->expires;
  56         interval = it->incr;
  57         if (val) {
  58                 struct task_cputime cputime;
  59                 u64 t;
  60
  61                 thread_group_cputimer(tsk, &cputime);
  62                 if (clock_id == CPUCLOCK_PROF)
  63                         t = cputime.utime + cputime.stime;
  64                 else
  65                         /* CPUCLOCK_VIRT */
  66                         t = cputime.utime;
  67
  68                 if (val < t)
  69                         /* about to fire */
  70                         val = TICK_NSEC;
  71                 else
  72                         val -= t;
  73         }
  74
  75         spin_unlock_irq(&tsk->sighand->siglock);
  76
  77         value->it_value = ns_to_timeval(val);
  78         value->it_interval = ns_to_timeval(interval);
  79 }
  80
  81 int do_getitimer(int which, struct itimerval *value)
  82 {
  83         struct task_struct *tsk = current;
  84
  85         switch (which) {
  86         case ITIMER_REAL:
  87                 spin_lock_irq(&tsk->sighand->siglock);
  88                 value->it_value = itimer_get_remtime(&tsk->signal->real_timer);
  89                 value->it_interval =
  90                         ktime_to_timeval(tsk->signal->it_real_incr);
  91                 spin_unlock_irq(&tsk->sighand->siglock);
  92                 break;
  93         case ITIMER_VIRTUAL:
  94                 get_cpu_itimer(tsk, CPUCLOCK_VIRT, value);
  95                 break;
  96         case ITIMER_PROF:
  97                 get_cpu_itimer(tsk, CPUCLOCK_PROF, value);
  98                 break;
  99         default:
 100                 return(-EINVAL);
 101         }
 102         return 0;
 103 }
 104
 105 SYSCALL_DEFINE2(getitimer, int, which, struct itimerval __user *, value)
 106 {
 107         int error = -EFAULT;
 108         struct itimerval get_buffer;
 109
 110         if (value) {
 111                 error = do_getitimer(which, &get_buffer);
 112                 if (!error &&
 113                     copy_to_user(value, &get_buffer, sizeof(get_buffer)))
 114                         error = -EFAULT;
 115         }
 116         return error;
 117 }
 118
 119
 120 /*
 121  * The timer is automagically restarted, when interval != 0
 122  */
 123 enum hrtimer_restart it_real_fn(struct hrtimer *timer)
 124 {
 125         struct signal_struct *sig =
 126                 container_of(timer, struct signal_struct, real_timer);
 127
 128         trace_itimer_expire(ITIMER_REAL, sig->leader_pid, 0);
 129         kill_pid_info(SIGALRM, SEND_SIG_PRIV, sig->leader_pid);
 130
 131         return HRTIMER_NORESTART;
 132 }
 133
 134 static void set_cpu_itimer(struct task_struct *tsk, unsigned int clock_id,
 135                            const struct itimerval *const value,
 136                            struct itimerval *const ovalue)
 137 {
 138         u64 oval, nval, ointerval, ninterval;
 139         struct cpu_itimer *it = &tsk->signal->it[clock_id];
 140
 141         nval = timeval_to_ns(&value->it_value);
 142         ninterval = timeval_to_ns(&value->it_interval);
 143
 144         spin_lock_irq(&tsk->sighand->siglock);
 145
 146         oval = it->expires;
 147         ointerval = it->incr;
 148         if (oval || nval) {
 149                 if (nval > 0)
 150                         nval += TICK_NSEC;
 151                 set_process_cpu_timer(tsk, clock_id, &nval, &oval);
 152         }
 153         it->expires = nval;
 154         it->incr = ninterval;
 155         trace_itimer_state(clock_id == CPUCLOCK_VIRT ?
 156                            ITIMER_VIRTUAL : ITIMER_PROF, value, nval);
 157
 158         spin_unlock_irq(&tsk->sighand->siglock);
 159
 160         if (ovalue) {
 161                 ovalue->it_value = ns_to_timeval(oval);
 162                 ovalue->it_interval = ns_to_timeval(ointerval);
 163         }
 164 }
 165
 166 /*
 167  * Returns true if the timeval is in canonical form
 168  */
 169 #define timeval_valid(t) \
 170         (((t)->tv_sec >= 0) && (((unsigned long) (t)->tv_usec) < USEC_PER_SEC))
 171
 172 int do_setitimer(int which, struct itimerval *value, struct itimerval *ovalue)
 173 {
 174         struct task_struct *tsk = current;
 175         struct hrtimer *timer;
 176         ktime_t expires;
 177
 178         /*
 179          * Validate the timevals in value.
 180          */
 181         if (!timeval_valid(&value->it_value) ||
 182             !timeval_valid(&value->it_interval))
 183                 return -EINVAL;
 184
 185         switch (which) {
 186         case ITIMER_REAL:
 187 again:
 188                 spin_lock_irq(&tsk->sighand->siglock);
 189                 timer = &tsk->signal->real_timer;
 190                 if (ovalue) {
 191                         ovalue->it_value = itimer_get_remtime(timer);
 192                         ovalue->it_interval
 193                                 = ktime_to_timeval(tsk->signal->it_real_incr);
 194                 }
 195                 /* We are sharing ->siglock with it_real_fn() */
 196                 if (hrtimer_try_to_cancel(timer) < 0) {
 197                         spin_unlock_irq(&tsk->sighand->siglock);
 198                         goto again;
 199                 }
 200                 expires = timeval_to_ktime(value->it_value);
 201                 if (expires != 0) {
 202                         tsk->signal->it_real_incr =
 203                                 timeval_to_ktime(value->it_interval);
 204                         hrtimer_start(timer, expires, HRTIMER_MODE_REL);
 205                 } else
 206                         tsk->signal->it_real_incr = 0;
 207
 208                 trace_itimer_state(ITIMER_REAL, value, 0);
 209                 spin_unlock_irq(&tsk->sighand->siglock);
 210                 break;
 211         case ITIMER_VIRTUAL:
 212                 set_cpu_itimer(tsk, CPUCLOCK_VIRT, value, ovalue);
 213                 break;
 214         case ITIMER_PROF:
 215                 set_cpu_itimer(tsk, CPUCLOCK_PROF, value, ovalue);
 216                 break;
 217         default:
 218                 return -EINVAL;
 219         }
 220         return 0;
 221 }
 222
 223 #ifdef __ARCH_WANT_SYS_ALARM
 224
 225 /**
 226  * alarm_setitimer - set alarm in seconds
 227  *
 228  * @seconds:    number of seconds until alarm
 229  *              0 disables the alarm
 230  *
 231  * Returns the remaining time in seconds of a pending timer or 0 when
 232  * the timer is not active.
 233  *
 234  * On 32 bit machines the seconds value is limited to (INT_MAX/2) to avoid
 235  * negative timeval settings which would cause immediate expiry.
 236  */
 237 static unsigned int alarm_setitimer(unsigned int seconds)
 238 {
 239         struct itimerval it_new, it_old;
 240
 241 #if BITS_PER_LONG < 64
 242         if (seconds > INT_MAX)
 243                 seconds = INT_MAX;
 244 #endif
 245         it_new.it_value.tv_sec = seconds;
 246         it_new.it_value.tv_usec = 0;
 247         it_new.it_interval.tv_sec = it_new.it_interval.tv_usec = 0;
 248
 249         do_setitimer(ITIMER_REAL, &it_new, &it_old);
 250
 251         /*
 252          * We can't return 0 if we have an alarm pending ...  And we'd
 253          * better return too much than too little anyway
 254          */
 255         if ((!it_old.it_value.tv_sec && it_old.it_value.tv_usec) ||
 256               it_old.it_value.tv_usec >= 500000)
 257                 it_old.it_value.tv_sec++;
 258
 259         return it_old.it_value.tv_sec;
 260 }
 261
 262 /*
 263  * For backwards compatibility?  This can be done in libc so Alpha
 264  * and all newer ports shouldn't need it.
 265  */
 266 SYSCALL_DEFINE1(alarm, unsigned int, seconds)
 267 {
 268         return alarm_setitimer(seconds);
 269 }
 270
 271 #endif
 272
 273 SYSCALL_DEFINE3(setitimer, int, which, struct itimerval __user *, value,
 274                 struct itimerval __user *, ovalue)
 275 {
 276         struct itimerval set_buffer, get_buffer;
 277         int error;
 278
 279         if (value) {
 280                 if(copy_from_user(&set_buffer, value, sizeof(set_buffer)))
 281                         return -EFAULT;
 282         } else {
 283                 memset(&set_buffer, 0, sizeof(set_buffer));
 284                 printk_once(KERN_WARNING "%s calls setitimer() with new_value NULL pointer."
 285                             " Misfeature support will be removed\n",
 286                             current->comm);
 287         }
 288
 289         error = do_setitimer(which, &set_buffer, ovalue ? &get_buffer : NULL);
 290         if (error || !ovalue)
 291                 return error;
 292
 293         if (copy_to_user(ovalue, &get_buffer, sizeof(get_buffer)))
 294                 return -EFAULT;
 295         return 0;
 296 }