kernel/time/itimer.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * linux/kernel/itimer.c
   4  *
   5  * Copyright (C) 1992 Darren Senn
   6  */
   7
   8 /* These are all the functions necessary to implement itimers */
   9
  10 #include <linux/mm.h>
  11 #include <linux/interrupt.h>
  12 #include <linux/syscalls.h>
  13 #include <linux/time.h>
  14 #include <linux/sched/signal.h>
  15 #include <linux/sched/cputime.h>
  16 #include <linux/posix-timers.h>
  17 #include <linux/hrtimer.h>
  18 #include <trace/events/timer.h>
  19 #include <linux/compat.h>
  20
  21 #include <linux/uaccess.h>
  22
  23 /**
  24  * itimer_get_remtime - get remaining time for the timer
  25  *
  26  * @timer: the timer to read
  27  *
  28  * Returns the delta between the expiry time and now, which can be
  29  * less than zero or 1usec for an pending expired timer
  30  */
  31 static struct timeval itimer_get_remtime(struct hrtimer *timer)
  32 {
  33         ktime_t rem = __hrtimer_get_remaining(timer, true);
  34
  35         /*
  36          * Racy but safe: if the itimer expires after the above
  37          * hrtimer_get_remtime() call but before this condition
  38          * then we return 0 - which is correct.
  39          */
  40         if (hrtimer_active(timer)) {
  41                 if (rem <= 0)
  42                         rem = NSEC_PER_USEC;
  43         } else
  44                 rem = 0;
  45
  46         return ktime_to_timeval(rem);
  47 }
  48
  49 static void get_cpu_itimer(struct task_struct *tsk, unsigned int clock_id,
  50                            struct itimerval *const value)
  51 {
  52         u64 val, interval;
  53         struct cpu_itimer *it = &tsk->signal->it[clock_id];
  54
  55         spin_lock_irq(&tsk->sighand->siglock);
  56
  57         val = it->expires;
  58         interval = it->incr;
  59         if (val) {
  60                 struct task_cputime cputime;
  61                 u64 t;
  62
  63                 thread_group_cputimer(tsk, &cputime);
  64                 if (clock_id == CPUCLOCK_PROF)
  65                         t = cputime.utime + cputime.stime;
  66                 else
  67                         /* CPUCLOCK_VIRT */
  68                         t = cputime.utime;
  69
  70                 if (val < t)
  71                         /* about to fire */
  72                         val = TICK_NSEC;
  73                 else
  74                         val -= t;
  75         }
  76
  77         spin_unlock_irq(&tsk->sighand->siglock);
  78
  79         value->it_value = ns_to_timeval(val);
  80         value->it_interval = ns_to_timeval(interval);
  81 }
  82
  83 int do_getitimer(int which, struct itimerval *value)
  84 {
  85         struct task_struct *tsk = current;
  86
  87         switch (which) {
  88         case ITIMER_REAL:
  89                 spin_lock_irq(&tsk->sighand->siglock);
  90                 value->it_value = itimer_get_remtime(&tsk->signal->real_timer);
  91                 value->it_interval =
  92                         ktime_to_timeval(tsk->signal->it_real_incr);
  93                 spin_unlock_irq(&tsk->sighand->siglock);
  94                 break;
  95         case ITIMER_VIRTUAL:
  96                 get_cpu_itimer(tsk, CPUCLOCK_VIRT, value);
  97                 break;
  98         case ITIMER_PROF:
  99                 get_cpu_itimer(tsk, CPUCLOCK_PROF, value);
 100                 break;
 101         default:
 102                 return(-EINVAL);
 103         }
 104         return 0;
 105 }
 106
 107 SYSCALL_DEFINE2(getitimer, int, which, struct itimerval __user *, value)
 108 {
 109         int error = -EFAULT;
 110         struct itimerval get_buffer;
 111
 112         if (value) {
 113                 error = do_getitimer(which, &get_buffer);
 114                 if (!error &&
 115                     copy_to_user(value, &get_buffer, sizeof(get_buffer)))
 116                         error = -EFAULT;
 117         }
 118         return error;
 119 }
 120
 121 #ifdef CONFIG_COMPAT
 122 COMPAT_SYSCALL_DEFINE2(getitimer, int, which,
 123                        struct compat_itimerval __user *, it)
 124 {
 125         struct itimerval kit;
 126         int error = do_getitimer(which, &kit);
 127
 128         if (!error && put_compat_itimerval(it, &kit))
 129                 error = -EFAULT;
 130         return error;
 131 }
 132 #endif
 133
 134
 135 /*
 136  * The timer is automagically restarted, when interval != 0
 137  */
 138 enum hrtimer_restart it_real_fn(struct hrtimer *timer)
 139 {
 140         struct signal_struct *sig =
 141                 container_of(timer, struct signal_struct, real_timer);
 142
 143         trace_itimer_expire(ITIMER_REAL, sig->leader_pid, 0);
 144         kill_pid_info(SIGALRM, SEND_SIG_PRIV, sig->leader_pid);
 145
 146         return HRTIMER_NORESTART;
 147 }
 148
 149 static void set_cpu_itimer(struct task_struct *tsk, unsigned int clock_id,
 150                            const struct itimerval *const value,
 151                            struct itimerval *const ovalue)
 152 {
 153         u64 oval, nval, ointerval, ninterval;
 154         struct cpu_itimer *it = &tsk->signal->it[clock_id];
 155
 156         /*
 157          * Use the to_ktime conversion because that clamps the maximum
 158          * value to KTIME_MAX and avoid multiplication overflows.
 159          */
 160         nval = ktime_to_ns(timeval_to_ktime(value->it_value));
 161         ninterval = ktime_to_ns(timeval_to_ktime(value->it_interval));
 162
 163         spin_lock_irq(&tsk->sighand->siglock);
 164
 165         oval = it->expires;
 166         ointerval = it->incr;
 167         if (oval || nval) {
 168                 if (nval > 0)
 169                         nval += TICK_NSEC;
 170                 set_process_cpu_timer(tsk, clock_id, &nval, &oval);
 171         }
 172         it->expires = nval;
 173         it->incr = ninterval;
 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                 ovalue->it_value = ns_to_timeval(oval);
 181                 ovalue->it_interval = ns_to_timeval(ointerval);
 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 != 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 = 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 #ifdef __ARCH_WANT_SYS_ALARM
 243
 244 /**
 245  * alarm_setitimer - set alarm in seconds
 246  *
 247  * @seconds:    number of seconds until alarm
 248  *              0 disables the alarm
 249  *
 250  * Returns the remaining time in seconds of a pending timer or 0 when
 251  * the timer is not active.
 252  *
 253  * On 32 bit machines the seconds value is limited to (INT_MAX/2) to avoid
 254  * negative timeval settings which would cause immediate expiry.
 255  */
 256 static unsigned int alarm_setitimer(unsigned int seconds)
 257 {
 258         struct itimerval it_new, it_old;
 259
 260 #if BITS_PER_LONG < 64
 261         if (seconds > INT_MAX)
 262                 seconds = INT_MAX;
 263 #endif
 264         it_new.it_value.tv_sec = seconds;
 265         it_new.it_value.tv_usec = 0;
 266         it_new.it_interval.tv_sec = it_new.it_interval.tv_usec = 0;
 267
 268         do_setitimer(ITIMER_REAL, &it_new, &it_old);
 269
 270         /*
 271          * We can't return 0 if we have an alarm pending ...  And we'd
 272          * better return too much than too little anyway
 273          */
 274         if ((!it_old.it_value.tv_sec && it_old.it_value.tv_usec) ||
 275               it_old.it_value.tv_usec >= 500000)
 276                 it_old.it_value.tv_sec++;
 277
 278         return it_old.it_value.tv_sec;
 279 }
 280
 281 /*
 282  * For backwards compatibility?  This can be done in libc so Alpha
 283  * and all newer ports shouldn't need it.
 284  */
 285 SYSCALL_DEFINE1(alarm, unsigned int, seconds)
 286 {
 287         return alarm_setitimer(seconds);
 288 }
 289
 290 #endif
 291
 292 SYSCALL_DEFINE3(setitimer, int, which, struct itimerval __user *, value,
 293                 struct itimerval __user *, ovalue)
 294 {
 295         struct itimerval set_buffer, get_buffer;
 296         int error;
 297
 298         if (value) {
 299                 if(copy_from_user(&set_buffer, value, sizeof(set_buffer)))
 300                         return -EFAULT;
 301         } else {
 302                 memset(&set_buffer, 0, sizeof(set_buffer));
 303                 printk_once(KERN_WARNING "%s calls setitimer() with new_value NULL pointer."
 304                             " Misfeature support will be removed\n",
 305                             current->comm);
 306         }
 307
 308         error = do_setitimer(which, &set_buffer, ovalue ? &get_buffer : NULL);
 309         if (error || !ovalue)
 310                 return error;
 311
 312         if (copy_to_user(ovalue, &get_buffer, sizeof(get_buffer)))
 313                 return -EFAULT;
 314         return 0;
 315 }
 316
 317 #ifdef CONFIG_COMPAT
 318 COMPAT_SYSCALL_DEFINE3(setitimer, int, which,
 319                        struct compat_itimerval __user *, in,
 320                        struct compat_itimerval __user *, out)
 321 {
 322         struct itimerval kin, kout;
 323         int error;
 324
 325         if (in) {
 326                 if (get_compat_itimerval(&kin, in))
 327                         return -EFAULT;
 328         } else {
 329                 memset(&kin, 0, sizeof(kin));
 330         }
 331
 332         error = do_setitimer(which, &kin, out ? &kout : NULL);
 333         if (error || !out)
 334                 return error;
 335         if (put_compat_itimerval(out, &kout))
 336                 return -EFAULT;
 337         return 0;
 338 }
 339 #endif