kernel/time/itimer.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Copyright (C) 1992 Darren Senn
   4  */
   5
   6 /* These are all the functions necessary to implement itimers */
   7
   8 #include <linux/mm.h>
   9 #include <linux/interrupt.h>
  10 #include <linux/syscalls.h>
  11 #include <linux/time.h>
  12 #include <linux/sched/signal.h>
  13 #include <linux/sched/cputime.h>
  14 #include <linux/posix-timers.h>
  15 #include <linux/hrtimer.h>
  16 #include <trace/events/timer.h>
  17 #include <linux/compat.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 timespec64 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_timespec64(rem);
  45 }
  46
  47 static void get_cpu_itimer(struct task_struct *tsk, unsigned int clock_id,
  48                            struct itimerspec64 *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                 u64 t, samples[CPUCLOCK_MAX];
  59
  60                 thread_group_sample_cputime(tsk, samples);
  61                 t = samples[clock_id];
  62
  63                 if (val < t)
  64                         /* about to fire */
  65                         val = TICK_NSEC;
  66                 else
  67                         val -= t;
  68         }
  69
  70         spin_unlock_irq(&tsk->sighand->siglock);
  71
  72         value->it_value = ns_to_timespec64(val);
  73         value->it_interval = ns_to_timespec64(interval);
  74 }
  75
  76 static int do_getitimer(int which, struct itimerspec64 *value)
  77 {
  78         struct task_struct *tsk = current;
  79
  80         switch (which) {
  81         case ITIMER_REAL:
  82                 spin_lock_irq(&tsk->sighand->siglock);
  83                 value->it_value = itimer_get_remtime(&tsk->signal->real_timer);
  84                 value->it_interval =
  85                         ktime_to_timespec64(tsk->signal->it_real_incr);
  86                 spin_unlock_irq(&tsk->sighand->siglock);
  87                 break;
  88         case ITIMER_VIRTUAL:
  89                 get_cpu_itimer(tsk, CPUCLOCK_VIRT, value);
  90                 break;
  91         case ITIMER_PROF:
  92                 get_cpu_itimer(tsk, CPUCLOCK_PROF, value);
  93                 break;
  94         default:
  95                 return(-EINVAL);
  96         }
  97         return 0;
  98 }
  99
 100 static int put_itimerval(struct __kernel_old_itimerval __user *o,
 101                          const struct itimerspec64 *i)
 102 {
 103         struct __kernel_old_itimerval v;
 104
 105         v.it_interval.tv_sec = i->it_interval.tv_sec;
 106         v.it_interval.tv_usec = i->it_interval.tv_nsec / NSEC_PER_USEC;
 107         v.it_value.tv_sec = i->it_value.tv_sec;
 108         v.it_value.tv_usec = i->it_value.tv_nsec / NSEC_PER_USEC;
 109         return copy_to_user(o, &v, sizeof(struct __kernel_old_itimerval)) ? -EFAULT : 0;
 110 }
 111
 112
 113 SYSCALL_DEFINE2(getitimer, int, which, struct __kernel_old_itimerval __user *, value)
 114 {
 115         struct itimerspec64 get_buffer;
 116         int error = do_getitimer(which, &get_buffer);
 117
 118         if (!error && put_itimerval(value, &get_buffer))
 119                 error = -EFAULT;
 120         return error;
 121 }
 122
 123 #if defined(CONFIG_COMPAT) || defined(CONFIG_ALPHA)
 124 struct old_itimerval32 {
 125         struct old_timeval32    it_interval;
 126         struct old_timeval32    it_value;
 127 };
 128
 129 static int put_old_itimerval32(struct old_itimerval32 __user *o,
 130                                const struct itimerspec64 *i)
 131 {
 132         struct old_itimerval32 v32;
 133
 134         v32.it_interval.tv_sec = i->it_interval.tv_sec;
 135         v32.it_interval.tv_usec = i->it_interval.tv_nsec / NSEC_PER_USEC;
 136         v32.it_value.tv_sec = i->it_value.tv_sec;
 137         v32.it_value.tv_usec = i->it_value.tv_nsec / NSEC_PER_USEC;
 138         return copy_to_user(o, &v32, sizeof(struct old_itimerval32)) ? -EFAULT : 0;
 139 }
 140
 141 COMPAT_SYSCALL_DEFINE2(getitimer, int, which,
 142                        struct old_itimerval32 __user *, value)
 143 {
 144         struct itimerspec64 get_buffer;
 145         int error = do_getitimer(which, &get_buffer);
 146
 147         if (!error && put_old_itimerval32(value, &get_buffer))
 148                 error = -EFAULT;
 149         return error;
 150 }
 151 #endif
 152
 153 /*
 154  * Invoked from dequeue_signal() when SIG_ALRM is delivered.
 155  *
 156  * Restart the ITIMER_REAL timer if it is armed as periodic timer.  Doing
 157  * this in the signal delivery path instead of self rearming prevents a DoS
 158  * with small increments in the high reolution timer case and reduces timer
 159  * noise in general.
 160  */
 161 void posixtimer_rearm_itimer(struct task_struct *tsk)
 162 {
 163         struct hrtimer *tmr = &tsk->signal->real_timer;
 164
 165         if (!hrtimer_is_queued(tmr) && tsk->signal->it_real_incr != 0) {
 166                 hrtimer_forward(tmr, tmr->base->get_time(),
 167                                 tsk->signal->it_real_incr);
 168                 hrtimer_restart(tmr);
 169         }
 170 }
 171
 172 /*
 173  * Interval timers are restarted in the signal delivery path.  See
 174  * posixtimer_rearm_itimer().
 175  */
 176 enum hrtimer_restart it_real_fn(struct hrtimer *timer)
 177 {
 178         struct signal_struct *sig =
 179                 container_of(timer, struct signal_struct, real_timer);
 180         struct pid *leader_pid = sig->pids[PIDTYPE_TGID];
 181
 182         trace_itimer_expire(ITIMER_REAL, leader_pid, 0);
 183         kill_pid_info(SIGALRM, SEND_SIG_PRIV, leader_pid);
 184
 185         return HRTIMER_NORESTART;
 186 }
 187
 188 static void set_cpu_itimer(struct task_struct *tsk, unsigned int clock_id,
 189                            const struct itimerspec64 *const value,
 190                            struct itimerspec64 *const ovalue)
 191 {
 192         u64 oval, nval, ointerval, ninterval;
 193         struct cpu_itimer *it = &tsk->signal->it[clock_id];
 194
 195         nval = timespec64_to_ns(&value->it_value);
 196         ninterval = timespec64_to_ns(&value->it_interval);
 197
 198         spin_lock_irq(&tsk->sighand->siglock);
 199
 200         oval = it->expires;
 201         ointerval = it->incr;
 202         if (oval || nval) {
 203                 if (nval > 0)
 204                         nval += TICK_NSEC;
 205                 set_process_cpu_timer(tsk, clock_id, &nval, &oval);
 206         }
 207         it->expires = nval;
 208         it->incr = ninterval;
 209         trace_itimer_state(clock_id == CPUCLOCK_VIRT ?
 210                            ITIMER_VIRTUAL : ITIMER_PROF, value, nval);
 211
 212         spin_unlock_irq(&tsk->sighand->siglock);
 213
 214         if (ovalue) {
 215                 ovalue->it_value = ns_to_timespec64(oval);
 216                 ovalue->it_interval = ns_to_timespec64(ointerval);
 217         }
 218 }
 219
 220 /*
 221  * Returns true if the timeval is in canonical form
 222  */
 223 #define timeval_valid(t) \
 224         (((t)->tv_sec >= 0) && (((unsigned long) (t)->tv_usec) < USEC_PER_SEC))
 225
 226 static int do_setitimer(int which, struct itimerspec64 *value,
 227                         struct itimerspec64 *ovalue)
 228 {
 229         struct task_struct *tsk = current;
 230         struct hrtimer *timer;
 231         ktime_t expires;
 232
 233         switch (which) {
 234         case ITIMER_REAL:
 235 again:
 236                 spin_lock_irq(&tsk->sighand->siglock);
 237                 timer = &tsk->signal->real_timer;
 238                 if (ovalue) {
 239                         ovalue->it_value = itimer_get_remtime(timer);
 240                         ovalue->it_interval
 241                                 = ktime_to_timespec64(tsk->signal->it_real_incr);
 242                 }
 243                 /* We are sharing ->siglock with it_real_fn() */
 244                 if (hrtimer_try_to_cancel(timer) < 0) {
 245                         spin_unlock_irq(&tsk->sighand->siglock);
 246                         hrtimer_cancel_wait_running(timer);
 247                         goto again;
 248                 }
 249                 expires = timespec64_to_ktime(value->it_value);
 250                 if (expires != 0) {
 251                         tsk->signal->it_real_incr =
 252                                 timespec64_to_ktime(value->it_interval);
 253                         hrtimer_start(timer, expires, HRTIMER_MODE_REL);
 254                 } else
 255                         tsk->signal->it_real_incr = 0;
 256
 257                 trace_itimer_state(ITIMER_REAL, value, 0);
 258                 spin_unlock_irq(&tsk->sighand->siglock);
 259                 break;
 260         case ITIMER_VIRTUAL:
 261                 set_cpu_itimer(tsk, CPUCLOCK_VIRT, value, ovalue);
 262                 break;
 263         case ITIMER_PROF:
 264                 set_cpu_itimer(tsk, CPUCLOCK_PROF, value, ovalue);
 265                 break;
 266         default:
 267                 return -EINVAL;
 268         }
 269         return 0;
 270 }
 271
 272 #ifdef CONFIG_SECURITY_SELINUX
 273 void clear_itimer(void)
 274 {
 275         struct itimerspec64 v = {};
 276         int i;
 277
 278         for (i = 0; i < 3; i++)
 279                 do_setitimer(i, &v, NULL);
 280 }
 281 #endif
 282
 283 #ifdef __ARCH_WANT_SYS_ALARM
 284
 285 /**
 286  * alarm_setitimer - set alarm in seconds
 287  *
 288  * @seconds:    number of seconds until alarm
 289  *              0 disables the alarm
 290  *
 291  * Returns the remaining time in seconds of a pending timer or 0 when
 292  * the timer is not active.
 293  *
 294  * On 32 bit machines the seconds value is limited to (INT_MAX/2) to avoid
 295  * negative timeval settings which would cause immediate expiry.
 296  */
 297 static unsigned int alarm_setitimer(unsigned int seconds)
 298 {
 299         struct itimerspec64 it_new, it_old;
 300
 301 #if BITS_PER_LONG < 64
 302         if (seconds > INT_MAX)
 303                 seconds = INT_MAX;
 304 #endif
 305         it_new.it_value.tv_sec = seconds;
 306         it_new.it_value.tv_nsec = 0;
 307         it_new.it_interval.tv_sec = it_new.it_interval.tv_nsec = 0;
 308
 309         do_setitimer(ITIMER_REAL, &it_new, &it_old);
 310
 311         /*
 312          * We can't return 0 if we have an alarm pending ...  And we'd
 313          * better return too much than too little anyway
 314          */
 315         if ((!it_old.it_value.tv_sec && it_old.it_value.tv_nsec) ||
 316               it_old.it_value.tv_nsec >= (NSEC_PER_SEC / 2))
 317                 it_old.it_value.tv_sec++;
 318
 319         return it_old.it_value.tv_sec;
 320 }
 321
 322 /*
 323  * For backwards compatibility?  This can be done in libc so Alpha
 324  * and all newer ports shouldn't need it.
 325  */
 326 SYSCALL_DEFINE1(alarm, unsigned int, seconds)
 327 {
 328         return alarm_setitimer(seconds);
 329 }
 330
 331 #endif
 332
 333 static int get_itimerval(struct itimerspec64 *o, const struct __kernel_old_itimerval __user *i)
 334 {
 335         struct __kernel_old_itimerval v;
 336
 337         if (copy_from_user(&v, i, sizeof(struct __kernel_old_itimerval)))
 338                 return -EFAULT;
 339
 340         /* Validate the timevals in value. */
 341         if (!timeval_valid(&v.it_value) ||
 342             !timeval_valid(&v.it_interval))
 343                 return -EINVAL;
 344
 345         o->it_interval.tv_sec = v.it_interval.tv_sec;
 346         o->it_interval.tv_nsec = v.it_interval.tv_usec * NSEC_PER_USEC;
 347         o->it_value.tv_sec = v.it_value.tv_sec;
 348         o->it_value.tv_nsec = v.it_value.tv_usec * NSEC_PER_USEC;
 349         return 0;
 350 }
 351
 352 SYSCALL_DEFINE3(setitimer, int, which, struct __kernel_old_itimerval __user *, value,
 353                 struct __kernel_old_itimerval __user *, ovalue)
 354 {
 355         struct itimerspec64 set_buffer, get_buffer;
 356         int error;
 357
 358         if (value) {
 359                 error = get_itimerval(&set_buffer, value);
 360                 if (error)
 361                         return error;
 362         } else {
 363                 memset(&set_buffer, 0, sizeof(set_buffer));
 364                 printk_once(KERN_WARNING "%s calls setitimer() with new_value NULL pointer."
 365                             " Misfeature support will be removed\n",
 366                             current->comm);
 367         }
 368
 369         error = do_setitimer(which, &set_buffer, ovalue ? &get_buffer : NULL);
 370         if (error || !ovalue)
 371                 return error;
 372
 373         if (put_itimerval(ovalue, &get_buffer))
 374                 return -EFAULT;
 375         return 0;
 376 }
 377
 378 #if defined(CONFIG_COMPAT) || defined(CONFIG_ALPHA)
 379 static int get_old_itimerval32(struct itimerspec64 *o, const struct old_itimerval32 __user *i)
 380 {
 381         struct old_itimerval32 v32;
 382
 383         if (copy_from_user(&v32, i, sizeof(struct old_itimerval32)))
 384                 return -EFAULT;
 385
 386         /* Validate the timevals in value.  */
 387         if (!timeval_valid(&v32.it_value) ||
 388             !timeval_valid(&v32.it_interval))
 389                 return -EINVAL;
 390
 391         o->it_interval.tv_sec = v32.it_interval.tv_sec;
 392         o->it_interval.tv_nsec = v32.it_interval.tv_usec * NSEC_PER_USEC;
 393         o->it_value.tv_sec = v32.it_value.tv_sec;
 394         o->it_value.tv_nsec = v32.it_value.tv_usec * NSEC_PER_USEC;
 395         return 0;
 396 }
 397
 398 COMPAT_SYSCALL_DEFINE3(setitimer, int, which,
 399                        struct old_itimerval32 __user *, value,
 400                        struct old_itimerval32 __user *, ovalue)
 401 {
 402         struct itimerspec64 set_buffer, get_buffer;
 403         int error;
 404
 405         if (value) {
 406                 error = get_old_itimerval32(&set_buffer, value);
 407                 if (error)
 408                         return error;
 409         } else {
 410                 memset(&set_buffer, 0, sizeof(set_buffer));
 411                 printk_once(KERN_WARNING "%s calls setitimer() with new_value NULL pointer."
 412                             " Misfeature support will be removed\n",
 413                             current->comm);
 414         }
 415
 416         error = do_setitimer(which, &set_buffer, ovalue ? &get_buffer : NULL);
 417         if (error || !ovalue)
 418                 return error;
 419         if (put_old_itimerval32(ovalue, &get_buffer))
 420                 return -EFAULT;
 421         return 0;
 422 }
 423 #endif