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                 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_timeval(val);
  73         value->it_interval = ns_to_timeval(interval);
  74 }
  75
  76 int do_getitimer(int which, struct itimerval *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_timeval(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 SYSCALL_DEFINE2(getitimer, int, which, struct itimerval __user *, value)
 101 {
 102         int error = -EFAULT;
 103         struct itimerval get_buffer;
 104
 105         if (value) {
 106                 error = do_getitimer(which, &get_buffer);
 107                 if (!error &&
 108                     copy_to_user(value, &get_buffer, sizeof(get_buffer)))
 109                         error = -EFAULT;
 110         }
 111         return error;
 112 }
 113
 114 #ifdef CONFIG_COMPAT
 115 COMPAT_SYSCALL_DEFINE2(getitimer, int, which,
 116                        struct compat_itimerval __user *, it)
 117 {
 118         struct itimerval kit;
 119         int error = do_getitimer(which, &kit);
 120
 121         if (!error && put_compat_itimerval(it, &kit))
 122                 error = -EFAULT;
 123         return error;
 124 }
 125 #endif
 126
 127
 128 /*
 129  * The timer is automagically restarted, when interval != 0
 130  */
 131 enum hrtimer_restart it_real_fn(struct hrtimer *timer)
 132 {
 133         struct signal_struct *sig =
 134                 container_of(timer, struct signal_struct, real_timer);
 135         struct pid *leader_pid = sig->pids[PIDTYPE_TGID];
 136
 137         trace_itimer_expire(ITIMER_REAL, leader_pid, 0);
 138         kill_pid_info(SIGALRM, SEND_SIG_PRIV, leader_pid);
 139
 140         return HRTIMER_NORESTART;
 141 }
 142
 143 static void set_cpu_itimer(struct task_struct *tsk, unsigned int clock_id,
 144                            const struct itimerval *const value,
 145                            struct itimerval *const ovalue)
 146 {
 147         u64 oval, nval, ointerval, ninterval;
 148         struct cpu_itimer *it = &tsk->signal->it[clock_id];
 149
 150         nval = ktime_to_ns(timeval_to_ktime(value->it_value));
 151         ninterval = ktime_to_ns(timeval_to_ktime(value->it_interval));
 152
 153         spin_lock_irq(&tsk->sighand->siglock);
 154
 155         oval = it->expires;
 156         ointerval = it->incr;
 157         if (oval || nval) {
 158                 if (nval > 0)
 159                         nval += TICK_NSEC;
 160                 set_process_cpu_timer(tsk, clock_id, &nval, &oval);
 161         }
 162         it->expires = nval;
 163         it->incr = ninterval;
 164         trace_itimer_state(clock_id == CPUCLOCK_VIRT ?
 165                            ITIMER_VIRTUAL : ITIMER_PROF, value, nval);
 166
 167         spin_unlock_irq(&tsk->sighand->siglock);
 168
 169         if (ovalue) {
 170                 ovalue->it_value = ns_to_timeval(oval);
 171                 ovalue->it_interval = ns_to_timeval(ointerval);
 172         }
 173 }
 174
 175 /*
 176  * Returns true if the timeval is in canonical form
 177  */
 178 #define timeval_valid(t) \
 179         (((t)->tv_sec >= 0) && (((unsigned long) (t)->tv_usec) < USEC_PER_SEC))
 180
 181 int do_setitimer(int which, struct itimerval *value, struct itimerval *ovalue)
 182 {
 183         struct task_struct *tsk = current;
 184         struct hrtimer *timer;
 185         ktime_t expires;
 186
 187         /*
 188          * Validate the timevals in value.
 189          */
 190         if (!timeval_valid(&value->it_value) ||
 191             !timeval_valid(&value->it_interval))
 192                 return -EINVAL;
 193
 194         switch (which) {
 195         case ITIMER_REAL:
 196 again:
 197                 spin_lock_irq(&tsk->sighand->siglock);
 198                 timer = &tsk->signal->real_timer;
 199                 if (ovalue) {
 200                         ovalue->it_value = itimer_get_remtime(timer);
 201                         ovalue->it_interval
 202                                 = ktime_to_timeval(tsk->signal->it_real_incr);
 203                 }
 204                 /* We are sharing ->siglock with it_real_fn() */
 205                 if (hrtimer_try_to_cancel(timer) < 0) {
 206                         spin_unlock_irq(&tsk->sighand->siglock);
 207                         hrtimer_cancel_wait_running(timer);
 208                         goto again;
 209                 }
 210                 expires = timeval_to_ktime(value->it_value);
 211                 if (expires != 0) {
 212                         tsk->signal->it_real_incr =
 213                                 timeval_to_ktime(value->it_interval);
 214                         hrtimer_start(timer, expires, HRTIMER_MODE_REL);
 215                 } else
 216                         tsk->signal->it_real_incr = 0;
 217
 218                 trace_itimer_state(ITIMER_REAL, value, 0);
 219                 spin_unlock_irq(&tsk->sighand->siglock);
 220                 break;
 221         case ITIMER_VIRTUAL:
 222                 set_cpu_itimer(tsk, CPUCLOCK_VIRT, value, ovalue);
 223                 break;
 224         case ITIMER_PROF:
 225                 set_cpu_itimer(tsk, CPUCLOCK_PROF, value, ovalue);
 226                 break;
 227         default:
 228                 return -EINVAL;
 229         }
 230         return 0;
 231 }
 232
 233 #ifdef __ARCH_WANT_SYS_ALARM
 234
 235 /**
 236  * alarm_setitimer - set alarm in seconds
 237  *
 238  * @seconds:    number of seconds until alarm
 239  *              0 disables the alarm
 240  *
 241  * Returns the remaining time in seconds of a pending timer or 0 when
 242  * the timer is not active.
 243  *
 244  * On 32 bit machines the seconds value is limited to (INT_MAX/2) to avoid
 245  * negative timeval settings which would cause immediate expiry.
 246  */
 247 static unsigned int alarm_setitimer(unsigned int seconds)
 248 {
 249         struct itimerval it_new, it_old;
 250
 251 #if BITS_PER_LONG < 64
 252         if (seconds > INT_MAX)
 253                 seconds = INT_MAX;
 254 #endif
 255         it_new.it_value.tv_sec = seconds;
 256         it_new.it_value.tv_usec = 0;
 257         it_new.it_interval.tv_sec = it_new.it_interval.tv_usec = 0;
 258
 259         do_setitimer(ITIMER_REAL, &it_new, &it_old);
 260
 261         /*
 262          * We can't return 0 if we have an alarm pending ...  And we'd
 263          * better return too much than too little anyway
 264          */
 265         if ((!it_old.it_value.tv_sec && it_old.it_value.tv_usec) ||
 266               it_old.it_value.tv_usec >= 500000)
 267                 it_old.it_value.tv_sec++;
 268
 269         return it_old.it_value.tv_sec;
 270 }
 271
 272 /*
 273  * For backwards compatibility?  This can be done in libc so Alpha
 274  * and all newer ports shouldn't need it.
 275  */
 276 SYSCALL_DEFINE1(alarm, unsigned int, seconds)
 277 {
 278         return alarm_setitimer(seconds);
 279 }
 280
 281 #endif
 282
 283 SYSCALL_DEFINE3(setitimer, int, which, struct itimerval __user *, value,
 284                 struct itimerval __user *, ovalue)
 285 {
 286         struct itimerval set_buffer, get_buffer;
 287         int error;
 288
 289         if (value) {
 290                 if(copy_from_user(&set_buffer, value, sizeof(set_buffer)))
 291                         return -EFAULT;
 292         } else {
 293                 memset(&set_buffer, 0, sizeof(set_buffer));
 294                 printk_once(KERN_WARNING "%s calls setitimer() with new_value NULL pointer."
 295                             " Misfeature support will be removed\n",
 296                             current->comm);
 297         }
 298
 299         error = do_setitimer(which, &set_buffer, ovalue ? &get_buffer : NULL);
 300         if (error || !ovalue)
 301                 return error;
 302
 303         if (copy_to_user(ovalue, &get_buffer, sizeof(get_buffer)))
 304                 return -EFAULT;
 305         return 0;
 306 }
 307
 308 #ifdef CONFIG_COMPAT
 309 COMPAT_SYSCALL_DEFINE3(setitimer, int, which,
 310                        struct compat_itimerval __user *, in,
 311                        struct compat_itimerval __user *, out)
 312 {
 313         struct itimerval kin, kout;
 314         int error;
 315
 316         if (in) {
 317                 if (get_compat_itimerval(&kin, in))
 318                         return -EFAULT;
 319         } else {
 320                 memset(&kin, 0, sizeof(kin));
 321         }
 322
 323         error = do_setitimer(which, &kin, out ? &kout : NULL);
 324         if (error || !out)
 325                 return error;
 326         if (put_compat_itimerval(out, &kout))
 327                 return -EFAULT;
 328         return 0;
 329 }
 330 #endif