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 itimerval __user *o,
 101                          const struct itimerspec64 *i)
 102 {
 103         struct 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 itimerval)) ? -EFAULT : 0;
 110 }
 111
 112
 113 SYSCALL_DEFINE2(getitimer, int, which, struct 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  * The timer is automagically restarted, when interval != 0
 155  */
 156 enum hrtimer_restart it_real_fn(struct hrtimer *timer)
 157 {
 158         struct signal_struct *sig =
 159                 container_of(timer, struct signal_struct, real_timer);
 160         struct pid *leader_pid = sig->pids[PIDTYPE_TGID];
 161
 162         trace_itimer_expire(ITIMER_REAL, leader_pid, 0);
 163         kill_pid_info(SIGALRM, SEND_SIG_PRIV, leader_pid);
 164
 165         return HRTIMER_NORESTART;
 166 }
 167
 168 static void set_cpu_itimer(struct task_struct *tsk, unsigned int clock_id,
 169                            const struct itimerspec64 *const value,
 170                            struct itimerspec64 *const ovalue)
 171 {
 172         u64 oval, nval, ointerval, ninterval;
 173         struct cpu_itimer *it = &tsk->signal->it[clock_id];
 174
 175         /*
 176          * Use the to_ktime conversion because that clamps the maximum
 177          * value to KTIME_MAX and avoid multiplication overflows.
 178          */
 179         nval = timespec64_to_ns(&value->it_value);
 180         ninterval = timespec64_to_ns(&value->it_interval);
 181
 182         spin_lock_irq(&tsk->sighand->siglock);
 183
 184         oval = it->expires;
 185         ointerval = it->incr;
 186         if (oval || nval) {
 187                 if (nval > 0)
 188                         nval += TICK_NSEC;
 189                 set_process_cpu_timer(tsk, clock_id, &nval, &oval);
 190         }
 191         it->expires = nval;
 192         it->incr = ninterval;
 193         trace_itimer_state(clock_id == CPUCLOCK_VIRT ?
 194                            ITIMER_VIRTUAL : ITIMER_PROF, value, nval);
 195
 196         spin_unlock_irq(&tsk->sighand->siglock);
 197
 198         if (ovalue) {
 199                 ovalue->it_value = ns_to_timespec64(oval);
 200                 ovalue->it_interval = ns_to_timespec64(ointerval);
 201         }
 202 }
 203
 204 /*
 205  * Returns true if the timeval is in canonical form
 206  */
 207 #define timeval_valid(t) \
 208         (((t)->tv_sec >= 0) && (((unsigned long) (t)->tv_usec) < USEC_PER_SEC))
 209
 210 static int do_setitimer(int which, struct itimerspec64 *value,
 211                         struct itimerspec64 *ovalue)
 212 {
 213         struct task_struct *tsk = current;
 214         struct hrtimer *timer;
 215         ktime_t expires;
 216
 217         switch (which) {
 218         case ITIMER_REAL:
 219 again:
 220                 spin_lock_irq(&tsk->sighand->siglock);
 221                 timer = &tsk->signal->real_timer;
 222                 if (ovalue) {
 223                         ovalue->it_value = itimer_get_remtime(timer);
 224                         ovalue->it_interval
 225                                 = ktime_to_timespec64(tsk->signal->it_real_incr);
 226                 }
 227                 /* We are sharing ->siglock with it_real_fn() */
 228                 if (hrtimer_try_to_cancel(timer) < 0) {
 229                         spin_unlock_irq(&tsk->sighand->siglock);
 230                         hrtimer_cancel_wait_running(timer);
 231                         goto again;
 232                 }
 233                 expires = timespec64_to_ktime(value->it_value);
 234                 if (expires != 0) {
 235                         tsk->signal->it_real_incr =
 236                                 timespec64_to_ktime(value->it_interval);
 237                         hrtimer_start(timer, expires, HRTIMER_MODE_REL);
 238                 } else
 239                         tsk->signal->it_real_incr = 0;
 240
 241                 trace_itimer_state(ITIMER_REAL, value, 0);
 242                 spin_unlock_irq(&tsk->sighand->siglock);
 243                 break;
 244         case ITIMER_VIRTUAL:
 245                 set_cpu_itimer(tsk, CPUCLOCK_VIRT, value, ovalue);
 246                 break;
 247         case ITIMER_PROF:
 248                 set_cpu_itimer(tsk, CPUCLOCK_PROF, value, ovalue);
 249                 break;
 250         default:
 251                 return -EINVAL;
 252         }
 253         return 0;
 254 }
 255
 256 #ifdef CONFIG_SECURITY_SELINUX
 257 void clear_itimer(void)
 258 {
 259         struct itimerspec64 v = {};
 260         int i;
 261
 262         for (i = 0; i < 3; i++)
 263                 do_setitimer(i, &v, NULL);
 264 }
 265 #endif
 266
 267 #ifdef __ARCH_WANT_SYS_ALARM
 268
 269 /**
 270  * alarm_setitimer - set alarm in seconds
 271  *
 272  * @seconds:    number of seconds until alarm
 273  *              0 disables the alarm
 274  *
 275  * Returns the remaining time in seconds of a pending timer or 0 when
 276  * the timer is not active.
 277  *
 278  * On 32 bit machines the seconds value is limited to (INT_MAX/2) to avoid
 279  * negative timeval settings which would cause immediate expiry.
 280  */
 281 static unsigned int alarm_setitimer(unsigned int seconds)
 282 {
 283         struct itimerspec64 it_new, it_old;
 284
 285 #if BITS_PER_LONG < 64
 286         if (seconds > INT_MAX)
 287                 seconds = INT_MAX;
 288 #endif
 289         it_new.it_value.tv_sec = seconds;
 290         it_new.it_value.tv_nsec = 0;
 291         it_new.it_interval.tv_sec = it_new.it_interval.tv_nsec = 0;
 292
 293         do_setitimer(ITIMER_REAL, &it_new, &it_old);
 294
 295         /*
 296          * We can't return 0 if we have an alarm pending ...  And we'd
 297          * better return too much than too little anyway
 298          */
 299         if ((!it_old.it_value.tv_sec && it_old.it_value.tv_nsec) ||
 300               it_old.it_value.tv_nsec >= (NSEC_PER_SEC / 2))
 301                 it_old.it_value.tv_sec++;
 302
 303         return it_old.it_value.tv_sec;
 304 }
 305
 306 /*
 307  * For backwards compatibility?  This can be done in libc so Alpha
 308  * and all newer ports shouldn't need it.
 309  */
 310 SYSCALL_DEFINE1(alarm, unsigned int, seconds)
 311 {
 312         return alarm_setitimer(seconds);
 313 }
 314
 315 #endif
 316
 317 static int get_itimerval(struct itimerspec64 *o, const struct itimerval __user *i)
 318 {
 319         struct itimerval v;
 320
 321         if (copy_from_user(&v, i, sizeof(struct itimerval)))
 322                 return -EFAULT;
 323
 324         /* Validate the timevals in value. */
 325         if (!timeval_valid(&v.it_value) ||
 326             !timeval_valid(&v.it_interval))
 327                 return -EINVAL;
 328
 329         o->it_interval.tv_sec = v.it_interval.tv_sec;
 330         o->it_interval.tv_nsec = v.it_interval.tv_usec * NSEC_PER_USEC;
 331         o->it_value.tv_sec = v.it_value.tv_sec;
 332         o->it_value.tv_nsec = v.it_value.tv_usec * NSEC_PER_USEC;
 333         return 0;
 334 }
 335
 336 SYSCALL_DEFINE3(setitimer, int, which, struct itimerval __user *, value,
 337                 struct itimerval __user *, ovalue)
 338 {
 339         struct itimerspec64 set_buffer, get_buffer;
 340         int error;
 341
 342         if (value) {
 343                 error = get_itimerval(&set_buffer, value);
 344                 if (error)
 345                         return error;
 346         } else {
 347                 memset(&set_buffer, 0, sizeof(set_buffer));
 348                 printk_once(KERN_WARNING "%s calls setitimer() with new_value NULL pointer."
 349                             " Misfeature support will be removed\n",
 350                             current->comm);
 351         }
 352
 353         error = do_setitimer(which, &set_buffer, ovalue ? &get_buffer : NULL);
 354         if (error || !ovalue)
 355                 return error;
 356
 357         if (put_itimerval(ovalue, &get_buffer))
 358                 return -EFAULT;
 359         return 0;
 360 }
 361
 362 #if defined(CONFIG_COMPAT) || defined(CONFIG_ALPHA)
 363 static int get_old_itimerval32(struct itimerspec64 *o, const struct old_itimerval32 __user *i)
 364 {
 365         struct old_itimerval32 v32;
 366
 367         if (copy_from_user(&v32, i, sizeof(struct old_itimerval32)))
 368                 return -EFAULT;
 369
 370         /* Validate the timevals in value.  */
 371         if (!timeval_valid(&v32.it_value) ||
 372             !timeval_valid(&v32.it_interval))
 373                 return -EINVAL;
 374
 375         o->it_interval.tv_sec = v32.it_interval.tv_sec;
 376         o->it_interval.tv_nsec = v32.it_interval.tv_usec * NSEC_PER_USEC;
 377         o->it_value.tv_sec = v32.it_value.tv_sec;
 378         o->it_value.tv_nsec = v32.it_value.tv_usec * NSEC_PER_USEC;
 379         return 0;
 380 }
 381
 382 COMPAT_SYSCALL_DEFINE3(setitimer, int, which,
 383                        struct old_itimerval32 __user *, value,
 384                        struct old_itimerval32 __user *, ovalue)
 385 {
 386         struct itimerspec64 set_buffer, get_buffer;
 387         int error;
 388
 389         if (value) {
 390                 error = get_old_itimerval32(&set_buffer, value);
 391                 if (error)
 392                         return error;
 393         } else {
 394                 memset(&set_buffer, 0, sizeof(set_buffer));
 395                 printk_once(KERN_WARNING "%s calls setitimer() with new_value NULL pointer."
 396                             " Misfeature support will be removed\n",
 397                             current->comm);
 398         }
 399
 400         error = do_setitimer(which, &set_buffer, ovalue ? &get_buffer : NULL);
 401         if (error || !ovalue)
 402                 return error;
 403         if (put_old_itimerval32(ovalue, &get_buffer))
 404                 return -EFAULT;
 405         return 0;
 406 }
 407 #endif