Line data Source code
1 : // SPDX-License-Identifier: GPL-2.0
2 : /*
3 : * fs/timerfd.c
4 : *
5 : * Copyright (C) 2007 Davide Libenzi <davidel@xmailserver.org>
6 : *
7 : *
8 : * Thanks to Thomas Gleixner for code reviews and useful comments.
9 : *
10 : */
11 :
12 : #include <linux/alarmtimer.h>
13 : #include <linux/file.h>
14 : #include <linux/poll.h>
15 : #include <linux/init.h>
16 : #include <linux/fs.h>
17 : #include <linux/sched.h>
18 : #include <linux/kernel.h>
19 : #include <linux/slab.h>
20 : #include <linux/list.h>
21 : #include <linux/spinlock.h>
22 : #include <linux/time.h>
23 : #include <linux/hrtimer.h>
24 : #include <linux/anon_inodes.h>
25 : #include <linux/timerfd.h>
26 : #include <linux/syscalls.h>
27 : #include <linux/compat.h>
28 : #include <linux/rcupdate.h>
29 : #include <linux/time_namespace.h>
30 :
31 : struct timerfd_ctx {
32 : union {
33 : struct hrtimer tmr;
34 : struct alarm alarm;
35 : } t;
36 : ktime_t tintv;
37 : ktime_t moffs;
38 : wait_queue_head_t wqh;
39 : u64 ticks;
40 : int clockid;
41 : short unsigned expired;
42 : short unsigned settime_flags; /* to show in fdinfo */
43 : struct rcu_head rcu;
44 : struct list_head clist;
45 : spinlock_t cancel_lock;
46 : bool might_cancel;
47 : };
48 :
49 : static LIST_HEAD(cancel_list);
50 : static DEFINE_SPINLOCK(cancel_lock);
51 :
52 : static inline bool isalarm(struct timerfd_ctx *ctx)
53 : {
54 5278360 : return ctx->clockid == CLOCK_REALTIME_ALARM ||
55 : ctx->clockid == CLOCK_BOOTTIME_ALARM;
56 : }
57 :
58 : /*
59 : * This gets called when the timer event triggers. We set the "expired"
60 : * flag, but we do not re-arm the timer (in case it's necessary,
61 : * tintv != 0) until the timer is accessed.
62 : */
63 205028 : static void timerfd_triggered(struct timerfd_ctx *ctx)
64 : {
65 205028 : unsigned long flags;
66 :
67 205028 : spin_lock_irqsave(&ctx->wqh.lock, flags);
68 204998 : ctx->expired = 1;
69 204998 : ctx->ticks++;
70 204998 : wake_up_locked_poll(&ctx->wqh, EPOLLIN);
71 204993 : spin_unlock_irqrestore(&ctx->wqh.lock, flags);
72 204991 : }
73 :
74 204933 : static enum hrtimer_restart timerfd_tmrproc(struct hrtimer *htmr)
75 : {
76 204933 : struct timerfd_ctx *ctx = container_of(htmr, struct timerfd_ctx,
77 : t.tmr);
78 204933 : timerfd_triggered(ctx);
79 204990 : return HRTIMER_NORESTART;
80 : }
81 :
82 0 : static enum alarmtimer_restart timerfd_alarmproc(struct alarm *alarm,
83 : ktime_t now)
84 : {
85 0 : struct timerfd_ctx *ctx = container_of(alarm, struct timerfd_ctx,
86 : t.alarm);
87 0 : timerfd_triggered(ctx);
88 0 : return ALARMTIMER_NORESTART;
89 : }
90 :
91 : /*
92 : * Called when the clock was set to cancel the timers in the cancel
93 : * list. This will wake up processes waiting on these timers. The
94 : * wake-up requires ctx->ticks to be non zero, therefore we increment
95 : * it before calling wake_up_locked().
96 : */
97 0 : void timerfd_clock_was_set(void)
98 : {
99 0 : ktime_t moffs = ktime_mono_to_real(0);
100 0 : struct timerfd_ctx *ctx;
101 0 : unsigned long flags;
102 :
103 0 : rcu_read_lock();
104 0 : list_for_each_entry_rcu(ctx, &cancel_list, clist) {
105 0 : if (!ctx->might_cancel)
106 0 : continue;
107 0 : spin_lock_irqsave(&ctx->wqh.lock, flags);
108 0 : if (ctx->moffs != moffs) {
109 0 : ctx->moffs = KTIME_MAX;
110 0 : ctx->ticks++;
111 0 : wake_up_locked_poll(&ctx->wqh, EPOLLIN);
112 : }
113 0 : spin_unlock_irqrestore(&ctx->wqh.lock, flags);
114 : }
115 0 : rcu_read_unlock();
116 0 : }
117 :
118 0 : static void timerfd_resume_work(struct work_struct *work)
119 : {
120 0 : timerfd_clock_was_set();
121 0 : }
122 :
123 : static DECLARE_WORK(timerfd_work, timerfd_resume_work);
124 :
125 : /*
126 : * Invoked from timekeeping_resume(). Defer the actual update to work so
127 : * timerfd_clock_was_set() runs in task context.
128 : */
129 0 : void timerfd_resume(void)
130 : {
131 0 : schedule_work(&timerfd_work);
132 0 : }
133 :
134 1166983 : static void __timerfd_remove_cancel(struct timerfd_ctx *ctx)
135 : {
136 1166983 : if (ctx->might_cancel) {
137 779 : ctx->might_cancel = false;
138 779 : spin_lock(&cancel_lock);
139 779 : list_del_rcu(&ctx->clist);
140 779 : spin_unlock(&cancel_lock);
141 : }
142 1166983 : }
143 :
144 81134 : static void timerfd_remove_cancel(struct timerfd_ctx *ctx)
145 : {
146 81134 : spin_lock(&ctx->cancel_lock);
147 81134 : __timerfd_remove_cancel(ctx);
148 81134 : spin_unlock(&ctx->cancel_lock);
149 81134 : }
150 :
151 1043317 : static bool timerfd_canceled(struct timerfd_ctx *ctx)
152 : {
153 1043317 : if (!ctx->might_cancel || ctx->moffs != KTIME_MAX)
154 : return false;
155 0 : ctx->moffs = ktime_mono_to_real(0);
156 0 : return true;
157 : }
158 :
159 1086556 : static void timerfd_setup_cancel(struct timerfd_ctx *ctx, int flags)
160 : {
161 1086556 : spin_lock(&ctx->cancel_lock);
162 1086602 : if ((ctx->clockid == CLOCK_REALTIME ||
163 : ctx->clockid == CLOCK_REALTIME_ALARM) &&
164 1637 : (flags & TFD_TIMER_ABSTIME) && (flags & TFD_TIMER_CANCEL_ON_SET)) {
165 773 : if (!ctx->might_cancel) {
166 773 : ctx->might_cancel = true;
167 773 : spin_lock(&cancel_lock);
168 773 : list_add_rcu(&ctx->clist, &cancel_list);
169 773 : spin_unlock(&cancel_lock);
170 : }
171 : } else {
172 1085829 : __timerfd_remove_cancel(ctx);
173 : }
174 1086787 : spin_unlock(&ctx->cancel_lock);
175 1086710 : }
176 :
177 1086663 : static ktime_t timerfd_get_remaining(struct timerfd_ctx *ctx)
178 : {
179 1086663 : ktime_t remaining;
180 :
181 1086663 : if (isalarm(ctx))
182 0 : remaining = alarm_expires_remaining(&ctx->t.alarm);
183 : else
184 1086663 : remaining = hrtimer_expires_remaining_adjusted(&ctx->t.tmr);
185 :
186 1086679 : return remaining < 0 ? 0: remaining;
187 : }
188 :
189 1086556 : static int timerfd_setup(struct timerfd_ctx *ctx, int flags,
190 : const struct itimerspec64 *ktmr)
191 : {
192 1086556 : enum hrtimer_mode htmode;
193 1086556 : ktime_t texp;
194 1086556 : int clockid = ctx->clockid;
195 :
196 1086556 : htmode = (flags & TFD_TIMER_ABSTIME) ?
197 : HRTIMER_MODE_ABS: HRTIMER_MODE_REL;
198 :
199 1086556 : texp = timespec64_to_ktime(ktmr->it_value);
200 1086556 : ctx->expired = 0;
201 1086556 : ctx->ticks = 0;
202 1086556 : ctx->tintv = timespec64_to_ktime(ktmr->it_interval);
203 :
204 1086556 : if (isalarm(ctx)) {
205 0 : alarm_init(&ctx->t.alarm,
206 : ctx->clockid == CLOCK_REALTIME_ALARM ?
207 : ALARM_REALTIME : ALARM_BOOTTIME,
208 : timerfd_alarmproc);
209 : } else {
210 1086556 : hrtimer_init(&ctx->t.tmr, clockid, htmode);
211 1086555 : hrtimer_set_expires(&ctx->t.tmr, texp);
212 1086555 : ctx->t.tmr.function = timerfd_tmrproc;
213 : }
214 :
215 1086555 : if (texp != 0) {
216 850759 : if (flags & TFD_TIMER_ABSTIME)
217 848572 : texp = timens_ktime_to_host(clockid, texp);
218 850758 : if (isalarm(ctx)) {
219 0 : if (flags & TFD_TIMER_ABSTIME)
220 0 : alarm_start(&ctx->t.alarm, texp);
221 : else
222 0 : alarm_start_relative(&ctx->t.alarm, texp);
223 : } else {
224 850758 : hrtimer_start(&ctx->t.tmr, texp, htmode);
225 : }
226 :
227 850795 : if (timerfd_canceled(ctx))
228 : return -ECANCELED;
229 : }
230 :
231 1086595 : ctx->settime_flags = flags & TFD_SETTIME_FLAGS;
232 1086595 : return 0;
233 : }
234 :
235 81134 : static int timerfd_release(struct inode *inode, struct file *file)
236 : {
237 81134 : struct timerfd_ctx *ctx = file->private_data;
238 :
239 81134 : timerfd_remove_cancel(ctx);
240 :
241 81133 : if (isalarm(ctx))
242 0 : alarm_cancel(&ctx->t.alarm);
243 : else
244 81133 : hrtimer_cancel(&ctx->t.tmr);
245 81132 : kfree_rcu(ctx, rcu);
246 81133 : return 0;
247 : }
248 :
249 453147 : static __poll_t timerfd_poll(struct file *file, poll_table *wait)
250 : {
251 453147 : struct timerfd_ctx *ctx = file->private_data;
252 453147 : __poll_t events = 0;
253 453147 : unsigned long flags;
254 :
255 453147 : poll_wait(file, &ctx->wqh, wait);
256 :
257 453147 : spin_lock_irqsave(&ctx->wqh.lock, flags);
258 453136 : if (ctx->ticks)
259 192525 : events |= EPOLLIN;
260 453136 : spin_unlock_irqrestore(&ctx->wqh.lock, flags);
261 :
262 453082 : return events;
263 : }
264 :
265 192552 : static ssize_t timerfd_read(struct file *file, char __user *buf, size_t count,
266 : loff_t *ppos)
267 : {
268 192552 : struct timerfd_ctx *ctx = file->private_data;
269 192552 : ssize_t res;
270 192552 : u64 ticks = 0;
271 :
272 192552 : if (count < sizeof(ticks))
273 : return -EINVAL;
274 192552 : spin_lock_irq(&ctx->wqh.lock);
275 192320 : if (file->f_flags & O_NONBLOCK)
276 : res = -EAGAIN;
277 : else
278 0 : res = wait_event_interruptible_locked_irq(ctx->wqh, ctx->ticks);
279 :
280 : /*
281 : * If clock has changed, we do not care about the
282 : * ticks and we do not rearm the timer. Userspace must
283 : * reevaluate anyway.
284 : */
285 192320 : if (timerfd_canceled(ctx)) {
286 0 : ctx->ticks = 0;
287 0 : ctx->expired = 0;
288 0 : res = -ECANCELED;
289 : }
290 :
291 192528 : if (ctx->ticks) {
292 192533 : ticks = ctx->ticks;
293 :
294 192533 : if (ctx->expired && ctx->tintv) {
295 : /*
296 : * If tintv != 0, this is a periodic timer that
297 : * needs to be re-armed. We avoid doing it in the timer
298 : * callback to avoid DoS attacks specifying a very
299 : * short timer period.
300 : */
301 0 : if (isalarm(ctx)) {
302 0 : ticks += alarm_forward_now(
303 0 : &ctx->t.alarm, ctx->tintv) - 1;
304 0 : alarm_restart(&ctx->t.alarm);
305 : } else {
306 0 : ticks += hrtimer_forward_now(&ctx->t.tmr,
307 0 : ctx->tintv) - 1;
308 0 : hrtimer_restart(&ctx->t.tmr);
309 : }
310 : }
311 192533 : ctx->expired = 0;
312 192533 : ctx->ticks = 0;
313 : }
314 192528 : spin_unlock_irq(&ctx->wqh.lock);
315 192552 : if (ticks)
316 192552 : res = put_user(ticks, (u64 __user *) buf) ? -EFAULT: sizeof(ticks);
317 : return res;
318 : }
319 :
320 : #ifdef CONFIG_PROC_FS
321 0 : static void timerfd_show(struct seq_file *m, struct file *file)
322 : {
323 0 : struct timerfd_ctx *ctx = file->private_data;
324 0 : struct timespec64 value, interval;
325 :
326 0 : spin_lock_irq(&ctx->wqh.lock);
327 0 : value = ktime_to_timespec64(timerfd_get_remaining(ctx));
328 0 : interval = ktime_to_timespec64(ctx->tintv);
329 0 : spin_unlock_irq(&ctx->wqh.lock);
330 :
331 0 : seq_printf(m,
332 : "clockid: %d\n"
333 : "ticks: %llu\n"
334 : "settime flags: 0%o\n"
335 : "it_value: (%llu, %llu)\n"
336 : "it_interval: (%llu, %llu)\n",
337 : ctx->clockid,
338 0 : (unsigned long long)ctx->ticks,
339 0 : ctx->settime_flags,
340 0 : (unsigned long long)value.tv_sec,
341 0 : (unsigned long long)value.tv_nsec,
342 0 : (unsigned long long)interval.tv_sec,
343 0 : (unsigned long long)interval.tv_nsec);
344 0 : }
345 : #else
346 : #define timerfd_show NULL
347 : #endif
348 :
349 : #ifdef CONFIG_CHECKPOINT_RESTORE
350 : static long timerfd_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
351 : {
352 : struct timerfd_ctx *ctx = file->private_data;
353 : int ret = 0;
354 :
355 : switch (cmd) {
356 : case TFD_IOC_SET_TICKS: {
357 : u64 ticks;
358 :
359 : if (copy_from_user(&ticks, (u64 __user *)arg, sizeof(ticks)))
360 : return -EFAULT;
361 : if (!ticks)
362 : return -EINVAL;
363 :
364 : spin_lock_irq(&ctx->wqh.lock);
365 : if (!timerfd_canceled(ctx)) {
366 : ctx->ticks = ticks;
367 : wake_up_locked_poll(&ctx->wqh, EPOLLIN);
368 : } else
369 : ret = -ECANCELED;
370 : spin_unlock_irq(&ctx->wqh.lock);
371 : break;
372 : }
373 : default:
374 : ret = -ENOTTY;
375 : break;
376 : }
377 :
378 : return ret;
379 : }
380 : #else
381 : #define timerfd_ioctl NULL
382 : #endif
383 :
384 : static const struct file_operations timerfd_fops = {
385 : .release = timerfd_release,
386 : .poll = timerfd_poll,
387 : .read = timerfd_read,
388 : .llseek = noop_llseek,
389 : .show_fdinfo = timerfd_show,
390 : .unlocked_ioctl = timerfd_ioctl,
391 : };
392 :
393 1086774 : static int timerfd_fget(int fd, struct fd *p)
394 : {
395 1086774 : struct fd f = fdget(fd);
396 1086606 : if (!f.file)
397 : return -EBADF;
398 1086606 : if (f.file->f_op != &timerfd_fops) {
399 0 : fdput(f);
400 0 : return -EINVAL;
401 : }
402 1086606 : *p = f;
403 1086606 : return 0;
404 : }
405 :
406 162255 : SYSCALL_DEFINE2(timerfd_create, int, clockid, int, flags)
407 : {
408 81127 : int ufd;
409 81127 : struct timerfd_ctx *ctx;
410 :
411 : /* Check the TFD_* constants for consistency. */
412 81127 : BUILD_BUG_ON(TFD_CLOEXEC != O_CLOEXEC);
413 81127 : BUILD_BUG_ON(TFD_NONBLOCK != O_NONBLOCK);
414 :
415 81127 : if ((flags & ~TFD_CREATE_FLAGS) ||
416 81127 : (clockid != CLOCK_MONOTONIC &&
417 81127 : clockid != CLOCK_REALTIME &&
418 81127 : clockid != CLOCK_REALTIME_ALARM &&
419 13585 : clockid != CLOCK_BOOTTIME &&
420 13585 : clockid != CLOCK_BOOTTIME_ALARM))
421 : return -EINVAL;
422 :
423 81127 : if ((clockid == CLOCK_REALTIME_ALARM ||
424 0 : clockid == CLOCK_BOOTTIME_ALARM) &&
425 0 : !capable(CAP_WAKE_ALARM))
426 : return -EPERM;
427 :
428 81127 : ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
429 81127 : if (!ctx)
430 : return -ENOMEM;
431 :
432 81127 : init_waitqueue_head(&ctx->wqh);
433 81127 : spin_lock_init(&ctx->cancel_lock);
434 81127 : ctx->clockid = clockid;
435 :
436 81127 : if (isalarm(ctx))
437 0 : alarm_init(&ctx->t.alarm,
438 : ctx->clockid == CLOCK_REALTIME_ALARM ?
439 : ALARM_REALTIME : ALARM_BOOTTIME,
440 : timerfd_alarmproc);
441 : else
442 81127 : hrtimer_init(&ctx->t.tmr, clockid, HRTIMER_MODE_ABS);
443 :
444 81128 : ctx->moffs = ktime_mono_to_real(0);
445 :
446 81127 : ufd = anon_inode_getfd("[timerfd]", &timerfd_fops, ctx,
447 81127 : O_RDWR | (flags & TFD_SHARED_FCNTL_FLAGS));
448 81128 : if (ufd < 0)
449 0 : kfree(ctx);
450 :
451 81128 : return ufd;
452 : }
453 :
454 1086608 : static int do_timerfd_settime(int ufd, int flags,
455 : const struct itimerspec64 *new,
456 : struct itimerspec64 *old)
457 : {
458 1086608 : struct fd f;
459 1086608 : struct timerfd_ctx *ctx;
460 1086608 : int ret;
461 :
462 1086608 : if ((flags & ~TFD_SETTIME_FLAGS) ||
463 1086608 : !itimerspec64_valid(new))
464 : return -EINVAL;
465 :
466 1086608 : ret = timerfd_fget(ufd, &f);
467 1086561 : if (ret)
468 : return ret;
469 1086561 : ctx = f.file->private_data;
470 :
471 1086561 : if (isalarm(ctx) && !capable(CAP_WAKE_ALARM)) {
472 0 : fdput(f);
473 0 : return -EPERM;
474 : }
475 :
476 1086561 : timerfd_setup_cancel(ctx, flags);
477 :
478 : /*
479 : * We need to stop the existing timer before reprogramming
480 : * it to the new values.
481 : */
482 1086731 : for (;;) {
483 1086731 : spin_lock_irq(&ctx->wqh.lock);
484 :
485 1086689 : if (isalarm(ctx)) {
486 0 : if (alarm_try_to_cancel(&ctx->t.alarm) >= 0)
487 : break;
488 : } else {
489 1086689 : if (hrtimer_try_to_cancel(&ctx->t.tmr) >= 0)
490 : break;
491 : }
492 0 : spin_unlock_irq(&ctx->wqh.lock);
493 :
494 0 : if (isalarm(ctx))
495 0 : hrtimer_cancel_wait_running(&ctx->t.alarm.timer);
496 : else
497 0 : hrtimer_cancel_wait_running(&ctx->t.tmr);
498 : }
499 :
500 : /*
501 : * If the timer is expired and it's periodic, we need to advance it
502 : * because the caller may want to know the previous expiration time.
503 : * We do not update "ticks" and "expired" since the timer will be
504 : * re-programmed again in the following timerfd_setup() call.
505 : */
506 1086787 : if (ctx->expired && ctx->tintv) {
507 0 : if (isalarm(ctx))
508 0 : alarm_forward_now(&ctx->t.alarm, ctx->tintv);
509 : else
510 0 : hrtimer_forward_now(&ctx->t.tmr, ctx->tintv);
511 : }
512 :
513 1086787 : old->it_value = ktime_to_timespec64(timerfd_get_remaining(ctx));
514 1086739 : old->it_interval = ktime_to_timespec64(ctx->tintv);
515 :
516 : /*
517 : * Re-program the timer to the new value ...
518 : */
519 1086736 : ret = timerfd_setup(ctx, flags, new);
520 :
521 1086760 : spin_unlock_irq(&ctx->wqh.lock);
522 1086731 : fdput(f);
523 1086731 : return ret;
524 : }
525 :
526 0 : static int do_timerfd_gettime(int ufd, struct itimerspec64 *t)
527 : {
528 0 : struct fd f;
529 0 : struct timerfd_ctx *ctx;
530 0 : int ret = timerfd_fget(ufd, &f);
531 0 : if (ret)
532 : return ret;
533 0 : ctx = f.file->private_data;
534 :
535 0 : spin_lock_irq(&ctx->wqh.lock);
536 0 : if (ctx->expired && ctx->tintv) {
537 0 : ctx->expired = 0;
538 :
539 0 : if (isalarm(ctx)) {
540 0 : ctx->ticks +=
541 0 : alarm_forward_now(
542 0 : &ctx->t.alarm, ctx->tintv) - 1;
543 0 : alarm_restart(&ctx->t.alarm);
544 : } else {
545 0 : ctx->ticks +=
546 0 : hrtimer_forward_now(&ctx->t.tmr, ctx->tintv)
547 0 : - 1;
548 0 : hrtimer_restart(&ctx->t.tmr);
549 : }
550 : }
551 0 : t->it_value = ktime_to_timespec64(timerfd_get_remaining(ctx));
552 0 : t->it_interval = ktime_to_timespec64(ctx->tintv);
553 0 : spin_unlock_irq(&ctx->wqh.lock);
554 0 : fdput(f);
555 0 : return 0;
556 : }
557 :
558 2173287 : SYSCALL_DEFINE4(timerfd_settime, int, ufd, int, flags,
559 : const struct __kernel_itimerspec __user *, utmr,
560 : struct __kernel_itimerspec __user *, otmr)
561 : {
562 1086616 : struct itimerspec64 new, old;
563 1086616 : int ret;
564 :
565 1086616 : if (get_itimerspec64(&new, utmr))
566 : return -EFAULT;
567 1086697 : ret = do_timerfd_settime(ufd, flags, &new, &old);
568 1086760 : if (ret)
569 0 : return ret;
570 1086760 : if (otmr && put_itimerspec64(&old, otmr))
571 0 : return -EFAULT;
572 :
573 : return ret;
574 : }
575 :
576 0 : SYSCALL_DEFINE2(timerfd_gettime, int, ufd, struct __kernel_itimerspec __user *, otmr)
577 : {
578 0 : struct itimerspec64 kotmr;
579 0 : int ret = do_timerfd_gettime(ufd, &kotmr);
580 0 : if (ret)
581 0 : return ret;
582 0 : return put_itimerspec64(&kotmr, otmr) ? -EFAULT : 0;
583 : }
584 :
585 : #ifdef CONFIG_COMPAT_32BIT_TIME
586 : SYSCALL_DEFINE4(timerfd_settime32, int, ufd, int, flags,
587 : const struct old_itimerspec32 __user *, utmr,
588 : struct old_itimerspec32 __user *, otmr)
589 : {
590 : struct itimerspec64 new, old;
591 : int ret;
592 :
593 : if (get_old_itimerspec32(&new, utmr))
594 : return -EFAULT;
595 : ret = do_timerfd_settime(ufd, flags, &new, &old);
596 : if (ret)
597 : return ret;
598 : if (otmr && put_old_itimerspec32(&old, otmr))
599 : return -EFAULT;
600 : return ret;
601 : }
602 :
603 : SYSCALL_DEFINE2(timerfd_gettime32, int, ufd,
604 : struct old_itimerspec32 __user *, otmr)
605 : {
606 : struct itimerspec64 kotmr;
607 : int ret = do_timerfd_gettime(ufd, &kotmr);
608 : if (ret)
609 : return ret;
610 : return put_old_itimerspec32(&kotmr, otmr) ? -EFAULT : 0;
611 : }
612 : #endif
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