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 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 #ifdef CONFIG_COMPAT
 120 COMPAT_SYSCALL_DEFINE2(getitimer, int, which,
 121                        struct compat_itimerval __user *, it)
 122 {
 123         struct itimerval kit;
 124         int error = do_getitimer(which, &kit);
 125
 126         if (!error && put_compat_itimerval(it, &kit))
 127                 error = -EFAULT;
 128         return error;
 129 }
 130 #endif
 131
 132
 133 /*
 134  * The timer is automagically restarted, when interval != 0
 135  */
 136 enum hrtimer_restart it_real_fn(struct hrtimer *timer)
 137 {
 138         struct signal_struct *sig =
 139                 container_of(timer, struct signal_struct, real_timer);
 140         struct pid *leader_pid = sig->pids[PIDTYPE_TGID];
 141
 142         trace_itimer_expire(ITIMER_REAL, leader_pid, 0);
 143         kill_pid_info(SIGALRM, SEND_SIG_PRIV, leader_pid);
 144
 145         return HRTIMER_NORESTART;
 146 }
 147
 148 static void set_cpu_itimer(struct task_struct *tsk, unsigned int clock_id,
 149                            const struct itimerval *const value,
 150                            struct itimerval *const ovalue)
 151 {
 152         u64 oval, nval, ointerval, ninterval;
 153         struct cpu_itimer *it = &tsk->signal->it[clock_id];
 154
 155         /*
 156          * Use the to_ktime conversion because that clamps the maximum
 157          * value to KTIME_MAX and avoid multiplication overflows.
 158          */
 159         nval = ktime_to_ns(timeval_to_ktime(value->it_value));
 160         ninterval = ktime_to_ns(timeval_to_ktime(value->it_interval));
 161
 162         spin_lock_irq(&tsk->sighand->siglock);
 163
 164         oval = it->expires;
 165         ointerval = it->incr;
 166         if (oval || nval) {
 167                 if (nval > 0)
 168                         nval += TICK_NSEC;
 169                 set_process_cpu_timer(tsk, clock_id, &nval, &oval);
 170         }
 171         it->expires = nval;
 172         it->incr = ninterval;
 173         trace_itimer_state(clock_id == CPUCLOCK_VIRT ?
 174                            ITIMER_VIRTUAL : ITIMER_PROF, value, nval);
 175
 176         spin_unlock_irq(&tsk->sighand->siglock);
 177
 178         if (ovalue) {
 179                 ovalue->it_value = ns_to_timeval(oval);
 180                 ovalue->it_interval = ns_to_timeval(ointerval);
 181         }
 182 }
 183
 184 /*
 185  * Returns true if the timeval is in canonical form
 186  */
 187 #define timeval_valid(t) \
 188         (((t)->tv_sec >= 0) && (((unsigned long) (t)->tv_usec) < USEC_PER_SEC))
 189
 190 int do_setitimer(int which, struct itimerval *value, struct itimerval *ovalue)
 191 {
 192         struct task_struct *tsk = current;
 193         struct hrtimer *timer;
 194         ktime_t expires;
 195
 196         /*
 197          * Validate the timevals in value.
 198          */
 199         if (!timeval_valid(&value->it_value) ||
 200             !timeval_valid(&value->it_interval))
 201                 return -EINVAL;
 202
 203         switch (which) {
 204         case ITIMER_REAL:
 205 again:
 206                 spin_lock_irq(&tsk->sighand->siglock);
 207                 timer = &tsk->signal->real_timer;
 208                 if (ovalue) {
 209                         ovalue->it_value = itimer_get_remtime(timer);
 210                         ovalue->it_interval
 211                                 = ktime_to_timeval(tsk->signal->it_real_incr);
 212                 }
 213                 /* We are sharing ->siglock with it_real_fn() */
 214                 if (hrtimer_try_to_cancel(timer) < 0) {
 215                         spin_unlock_irq(&tsk->sighand->siglock);
 216                         goto again;
 217                 }
 218                 expires = timeval_to_ktime(value->it_value);
 219                 if (expires != 0) {
 220                         tsk->signal->it_real_incr =
 221                                 timeval_to_ktime(value->it_interval);
 222                         hrtimer_start(timer, expires, HRTIMER_MODE_REL);
 223                 } else
 224                         tsk->signal->it_real_incr = 0;
 225
 226                 trace_itimer_state(ITIMER_REAL, value, 0);
 227                 spin_unlock_irq(&tsk->sighand->siglock);
 228                 break;
 229         case ITIMER_VIRTUAL:
 230                 set_cpu_itimer(tsk, CPUCLOCK_VIRT, value, ovalue);
 231                 break;
 232         case ITIMER_PROF:
 233                 set_cpu_itimer(tsk, CPUCLOCK_PROF, value, ovalue);
 234                 break;
 235         default:
 236                 return -EINVAL;
 237         }
 238         return 0;
 239 }
 240
 241 #ifdef __ARCH_WANT_SYS_ALARM
 242
 243 /**
 244  * alarm_setitimer - set alarm in seconds
 245  *
 246  * @seconds:    number of seconds until alarm
 247  *              0 disables the alarm
 248  *
 249  * Returns the remaining time in seconds of a pending timer or 0 when
 250  * the timer is not active.
 251  *
 252  * On 32 bit machines the seconds value is limited to (INT_MAX/2) to avoid
 253  * negative timeval settings which would cause immediate expiry.
 254  */
 255 static unsigned int alarm_setitimer(unsigned int seconds)
 256 {
 257         struct itimerval it_new, it_old;
 258
 259 #if BITS_PER_LONG < 64
 260         if (seconds > INT_MAX)
 261                 seconds = INT_MAX;
 262 #endif
 263         it_new.it_value.tv_sec = seconds;
 264         it_new.it_value.tv_usec = 0;
 265         it_new.it_interval.tv_sec = it_new.it_interval.tv_usec = 0;
 266
 267         do_setitimer(ITIMER_REAL, &it_new, &it_old);
 268
 269         /*
 270          * We can't return 0 if we have an alarm pending ...  And we'd
 271          * better return too much than too little anyway
 272          */
 273         if ((!it_old.it_value.tv_sec && it_old.it_value.tv_usec) ||
 274               it_old.it_value.tv_usec >= 500000)
 275                 it_old.it_value.tv_sec++;
 276
 277         return it_old.it_value.tv_sec;
 278 }
 279
 280 /*
 281  * For backwards compatibility?  This can be done in libc so Alpha
 282  * and all newer ports shouldn't need it.
 283  */
 284 SYSCALL_DEFINE1(alarm, unsigned int, seconds)
 285 {
 286         return alarm_setitimer(seconds);
 287 }
 288
 289 #endif
 290
 291 SYSCALL_DEFINE3(setitimer, int, which, struct itimerval __user *, value,
 292                 struct itimerval __user *, ovalue)
 293 {
 294         struct itimerval set_buffer, get_buffer;
 295         int error;
 296
 297         if (value) {
 298                 if(copy_from_user(&set_buffer, value, sizeof(set_buffer)))
 299                         return -EFAULT;
 300         } else {
 301                 memset(&set_buffer, 0, sizeof(set_buffer));
 302                 printk_once(KERN_WARNING "%s calls setitimer() with new_value NULL pointer."
 303                             " Misfeature support will be removed\n",
 304                             current->comm);
 305         }
 306
 307         error = do_setitimer(which, &set_buffer, ovalue ? &get_buffer : NULL);
 308         if (error || !ovalue)
 309                 return error;
 310
 311         if (copy_to_user(ovalue, &get_buffer, sizeof(get_buffer)))
 312                 return -EFAULT;
 313         return 0;
 314 }
 315
 316 #ifdef CONFIG_COMPAT
 317 COMPAT_SYSCALL_DEFINE3(setitimer, int, which,
 318                        struct compat_itimerval __user *, in,
 319                        struct compat_itimerval __user *, out)
 320 {
 321         struct itimerval kin, kout;
 322         int error;
 323
 324         if (in) {
 325                 if (get_compat_itimerval(&kin, in))
 326                         return -EFAULT;
 327         } else {
 328                 memset(&kin, 0, sizeof(kin));
 329         }
 330
 331         error = do_setitimer(which, &kin, out ? &kout : NULL);
 332         if (error || !out)
 333                 return error;
 334         if (put_compat_itimerval(out, &kout))
 335                 return -EFAULT;
 336         return 0;
 337 }
 338 #endif