projects/linux·blob v4.13-rc4 · refs

588 lines · 13.3 KiB

1/*
2 * fs/timerfd.c
3 *
4 * Copyright (C) 2007 Davide Libenzi <[email protected]>
5 *
6 *
7 * Thanks to Thomas Gleixner for code reviews and useful comments.
8 *
9 */
10
11#include <linux/alarmtimer.h>
12#include <linux/file.h>
13#include <linux/poll.h>
14#include <linux/init.h>
15#include <linux/fs.h>
16#include <linux/sched.h>
17#include <linux/kernel.h>
18#include <linux/slab.h>
19#include <linux/list.h>
20#include <linux/spinlock.h>
21#include <linux/time.h>
22#include <linux/hrtimer.h>
23#include <linux/anon_inodes.h>
24#include <linux/timerfd.h>
25#include <linux/syscalls.h>
26#include <linux/compat.h>
27#include <linux/rcupdate.h>
28
29struct timerfd_ctx {
30 union {
31 struct hrtimer tmr;
32 struct alarm alarm;
33 } t;
34 ktime_t tintv;
35 ktime_t moffs;
36 wait_queue_head_t wqh;
37 u64 ticks;
38 int clockid;
39 short unsigned expired;
40 short unsigned settime_flags; /* to show in fdinfo */
41 struct rcu_head rcu;
42 struct list_head clist;
43 spinlock_t cancel_lock;
44 bool might_cancel;
45};
46
47static LIST_HEAD(cancel_list);
48static DEFINE_SPINLOCK(cancel_lock);
49
50static inline bool isalarm(struct timerfd_ctx *ctx)
51{
52 return ctx->clockid == CLOCK_REALTIME_ALARM ||
53 ctx->clockid == CLOCK_BOOTTIME_ALARM;
54}
55
56/*
57 * This gets called when the timer event triggers. We set the "expired"
58 * flag, but we do not re-arm the timer (in case it's necessary,
59 * tintv != 0) until the timer is accessed.
60 */
61static void timerfd_triggered(struct timerfd_ctx *ctx)
62{
63 unsigned long flags;
64
65 spin_lock_irqsave(&ctx->wqh.lock, flags);
66 ctx->expired = 1;
67 ctx->ticks++;
68 wake_up_locked(&ctx->wqh);
69 spin_unlock_irqrestore(&ctx->wqh.lock, flags);
70}
71
72static enum hrtimer_restart timerfd_tmrproc(struct hrtimer *htmr)
73{
74 struct timerfd_ctx *ctx = container_of(htmr, struct timerfd_ctx,
75 t.tmr);
76 timerfd_triggered(ctx);
77 return HRTIMER_NORESTART;
78}
79
80static enum alarmtimer_restart timerfd_alarmproc(struct alarm *alarm,
81 ktime_t now)
82{
83 struct timerfd_ctx *ctx = container_of(alarm, struct timerfd_ctx,
84 t.alarm);
85 timerfd_triggered(ctx);
86 return ALARMTIMER_NORESTART;
87}
88
89/*
90 * Called when the clock was set to cancel the timers in the cancel
91 * list. This will wake up processes waiting on these timers. The
92 * wake-up requires ctx->ticks to be non zero, therefore we increment
93 * it before calling wake_up_locked().
94 */
95void timerfd_clock_was_set(void)
96{
97 ktime_t moffs = ktime_mono_to_real(0);
98 struct timerfd_ctx *ctx;
99 unsigned long flags;
100
101 rcu_read_lock();
102 list_for_each_entry_rcu(ctx, &cancel_list, clist) {
103 if (!ctx->might_cancel)
104 continue;
105 spin_lock_irqsave(&ctx->wqh.lock, flags);
106 if (ctx->moffs != moffs) {
107 ctx->moffs = KTIME_MAX;
108 ctx->ticks++;
109 wake_up_locked(&ctx->wqh);
110 }
111 spin_unlock_irqrestore(&ctx->wqh.lock, flags);
112 }
113 rcu_read_unlock();
114}
115
116static void __timerfd_remove_cancel(struct timerfd_ctx *ctx)
117{
118 if (ctx->might_cancel) {
119 ctx->might_cancel = false;
120 spin_lock(&cancel_lock);
121 list_del_rcu(&ctx->clist);
122 spin_unlock(&cancel_lock);
123 }
124}
125
126static void timerfd_remove_cancel(struct timerfd_ctx *ctx)
127{
128 spin_lock(&ctx->cancel_lock);
129 __timerfd_remove_cancel(ctx);
130 spin_unlock(&ctx->cancel_lock);
131}
132
133static bool timerfd_canceled(struct timerfd_ctx *ctx)
134{
135 if (!ctx->might_cancel || ctx->moffs != KTIME_MAX)
136 return false;
137 ctx->moffs = ktime_mono_to_real(0);
138 return true;
139}
140
141static void timerfd_setup_cancel(struct timerfd_ctx *ctx, int flags)
142{
143 spin_lock(&ctx->cancel_lock);
144 if ((ctx->clockid == CLOCK_REALTIME ||
145 ctx->clockid == CLOCK_REALTIME_ALARM) &&
146 (flags & TFD_TIMER_ABSTIME) && (flags & TFD_TIMER_CANCEL_ON_SET)) {
147 if (!ctx->might_cancel) {
148 ctx->might_cancel = true;
149 spin_lock(&cancel_lock);
150 list_add_rcu(&ctx->clist, &cancel_list);
151 spin_unlock(&cancel_lock);
152 }
153 } else {
154 __timerfd_remove_cancel(ctx);
155 }
156 spin_unlock(&ctx->cancel_lock);
157}
158
159static ktime_t timerfd_get_remaining(struct timerfd_ctx *ctx)
160{
161 ktime_t remaining;
162
163 if (isalarm(ctx))
164 remaining = alarm_expires_remaining(&ctx->t.alarm);
165 else
166 remaining = hrtimer_expires_remaining_adjusted(&ctx->t.tmr);
167
168 return remaining < 0 ? 0: remaining;
169}
170
171static int timerfd_setup(struct timerfd_ctx *ctx, int flags,
172 const struct itimerspec64 *ktmr)
173{
174 enum hrtimer_mode htmode;
175 ktime_t texp;
176 int clockid = ctx->clockid;
177
178 htmode = (flags & TFD_TIMER_ABSTIME) ?
179 HRTIMER_MODE_ABS: HRTIMER_MODE_REL;
180
181 texp = timespec64_to_ktime(ktmr->it_value);
182 ctx->expired = 0;
183 ctx->ticks = 0;
184 ctx->tintv = timespec64_to_ktime(ktmr->it_interval);
185
186 if (isalarm(ctx)) {
187 alarm_init(&ctx->t.alarm,
188 ctx->clockid == CLOCK_REALTIME_ALARM ?
189 ALARM_REALTIME : ALARM_BOOTTIME,
190 timerfd_alarmproc);
191 } else {
192 hrtimer_init(&ctx->t.tmr, clockid, htmode);
193 hrtimer_set_expires(&ctx->t.tmr, texp);
194 ctx->t.tmr.function = timerfd_tmrproc;
195 }
196
197 if (texp != 0) {
198 if (isalarm(ctx)) {
199 if (flags & TFD_TIMER_ABSTIME)
200 alarm_start(&ctx->t.alarm, texp);
201 else
202 alarm_start_relative(&ctx->t.alarm, texp);
203 } else {
204 hrtimer_start(&ctx->t.tmr, texp, htmode);
205 }
206
207 if (timerfd_canceled(ctx))
208 return -ECANCELED;
209 }
210
211 ctx->settime_flags = flags & TFD_SETTIME_FLAGS;
212 return 0;
213}
214
215static int timerfd_release(struct inode *inode, struct file *file)
216{
217 struct timerfd_ctx *ctx = file->private_data;
218
219 timerfd_remove_cancel(ctx);
220
221 if (isalarm(ctx))
222 alarm_cancel(&ctx->t.alarm);
223 else
224 hrtimer_cancel(&ctx->t.tmr);
225 kfree_rcu(ctx, rcu);
226 return 0;
227}
228
229static unsigned int timerfd_poll(struct file *file, poll_table *wait)
230{
231 struct timerfd_ctx *ctx = file->private_data;
232 unsigned int events = 0;
233 unsigned long flags;
234
235 poll_wait(file, &ctx->wqh, wait);
236
237 spin_lock_irqsave(&ctx->wqh.lock, flags);
238 if (ctx->ticks)
239 events |= POLLIN;
240 spin_unlock_irqrestore(&ctx->wqh.lock, flags);
241
242 return events;
243}
244
245static ssize_t timerfd_read(struct file *file, char __user *buf, size_t count,
246 loff_t *ppos)
247{
248 struct timerfd_ctx *ctx = file->private_data;
249 ssize_t res;
250 u64 ticks = 0;
251
252 if (count < sizeof(ticks))
253 return -EINVAL;
254 spin_lock_irq(&ctx->wqh.lock);
255 if (file->f_flags & O_NONBLOCK)
256 res = -EAGAIN;
257 else
258 res = wait_event_interruptible_locked_irq(ctx->wqh, ctx->ticks);
259
260 /*
261 * If clock has changed, we do not care about the
262 * ticks and we do not rearm the timer. Userspace must
263 * reevaluate anyway.
264 */
265 if (timerfd_canceled(ctx)) {
266 ctx->ticks = 0;
267 ctx->expired = 0;
268 res = -ECANCELED;
269 }
270
271 if (ctx->ticks) {
272 ticks = ctx->ticks;
273
274 if (ctx->expired && ctx->tintv) {
275 /*
276 * If tintv != 0, this is a periodic timer that
277 * needs to be re-armed. We avoid doing it in the timer
278 * callback to avoid DoS attacks specifying a very
279 * short timer period.
280 */
281 if (isalarm(ctx)) {
282 ticks += alarm_forward_now(
283 &ctx->t.alarm, ctx->tintv) - 1;
284 alarm_restart(&ctx->t.alarm);
285 } else {
286 ticks += hrtimer_forward_now(&ctx->t.tmr,
287 ctx->tintv) - 1;
288 hrtimer_restart(&ctx->t.tmr);
289 }
290 }
291 ctx->expired = 0;
292 ctx->ticks = 0;
293 }
294 spin_unlock_irq(&ctx->wqh.lock);
295 if (ticks)
296 res = put_user(ticks, (u64 __user *) buf) ? -EFAULT: sizeof(ticks);
297 return res;
298}
299
300#ifdef CONFIG_PROC_FS
301static void timerfd_show(struct seq_file *m, struct file *file)
302{
303 struct timerfd_ctx *ctx = file->private_data;
304 struct itimerspec t;
305
306 spin_lock_irq(&ctx->wqh.lock);
307 t.it_value = ktime_to_timespec(timerfd_get_remaining(ctx));
308 t.it_interval = ktime_to_timespec(ctx->tintv);
309 spin_unlock_irq(&ctx->wqh.lock);
310
311 seq_printf(m,
312 "clockid: %d\n"
313 "ticks: %llu\n"
314 "settime flags: 0%o\n"
315 "it_value: (%llu, %llu)\n"
316 "it_interval: (%llu, %llu)\n",
317 ctx->clockid,
318 (unsigned long long)ctx->ticks,
319 ctx->settime_flags,
320 (unsigned long long)t.it_value.tv_sec,
321 (unsigned long long)t.it_value.tv_nsec,
322 (unsigned long long)t.it_interval.tv_sec,
323 (unsigned long long)t.it_interval.tv_nsec);
324}
325#else
326#define timerfd_show NULL
327#endif
328
329#ifdef CONFIG_CHECKPOINT_RESTORE
330static long timerfd_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
331{
332 struct timerfd_ctx *ctx = file->private_data;
333 int ret = 0;
334
335 switch (cmd) {
336 case TFD_IOC_SET_TICKS: {
337 u64 ticks;
338
339 if (copy_from_user(&ticks, (u64 __user *)arg, sizeof(ticks)))
340 return -EFAULT;
341 if (!ticks)
342 return -EINVAL;
343
344 spin_lock_irq(&ctx->wqh.lock);
345 if (!timerfd_canceled(ctx)) {
346 ctx->ticks = ticks;
347 wake_up_locked(&ctx->wqh);
348 } else
349 ret = -ECANCELED;
350 spin_unlock_irq(&ctx->wqh.lock);
351 break;
352 }
353 default:
354 ret = -ENOTTY;
355 break;
356 }
357
358 return ret;
359}
360#else
361#define timerfd_ioctl NULL
362#endif
363
364static const struct file_operations timerfd_fops = {
365 .release = timerfd_release,
366 .poll = timerfd_poll,
367 .read = timerfd_read,
368 .llseek = noop_llseek,
369 .show_fdinfo = timerfd_show,
370 .unlocked_ioctl = timerfd_ioctl,
371};
372
373static int timerfd_fget(int fd, struct fd *p)
374{
375 struct fd f = fdget(fd);
376 if (!f.file)
377 return -EBADF;
378 if (f.file->f_op != &timerfd_fops) {
379 fdput(f);
380 return -EINVAL;
381 }
382 *p = f;
383 return 0;
384}
385
386SYSCALL_DEFINE2(timerfd_create, int, clockid, int, flags)
387{
388 int ufd;
389 struct timerfd_ctx *ctx;
390
391 /* Check the TFD_* constants for consistency. */
392 BUILD_BUG_ON(TFD_CLOEXEC != O_CLOEXEC);
393 BUILD_BUG_ON(TFD_NONBLOCK != O_NONBLOCK);
394
395 if ((flags & ~TFD_CREATE_FLAGS) ||
396 (clockid != CLOCK_MONOTONIC &&
397 clockid != CLOCK_REALTIME &&
398 clockid != CLOCK_REALTIME_ALARM &&
399 clockid != CLOCK_BOOTTIME &&
400 clockid != CLOCK_BOOTTIME_ALARM))
401 return -EINVAL;
402
403 if ((clockid == CLOCK_REALTIME_ALARM ||
404 clockid == CLOCK_BOOTTIME_ALARM) &&
405 !capable(CAP_WAKE_ALARM))
406 return -EPERM;
407
408 ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
409 if (!ctx)
410 return -ENOMEM;
411
412 init_waitqueue_head(&ctx->wqh);
413 spin_lock_init(&ctx->cancel_lock);
414 ctx->clockid = clockid;
415
416 if (isalarm(ctx))
417 alarm_init(&ctx->t.alarm,
418 ctx->clockid == CLOCK_REALTIME_ALARM ?
419 ALARM_REALTIME : ALARM_BOOTTIME,
420 timerfd_alarmproc);
421 else
422 hrtimer_init(&ctx->t.tmr, clockid, HRTIMER_MODE_ABS);
423
424 ctx->moffs = ktime_mono_to_real(0);
425
426 ufd = anon_inode_getfd("[timerfd]", &timerfd_fops, ctx,
427 O_RDWR | (flags & TFD_SHARED_FCNTL_FLAGS));
428 if (ufd < 0)
429 kfree(ctx);
430
431 return ufd;
432}
433
434static int do_timerfd_settime(int ufd, int flags,
435 const struct itimerspec64 *new,
436 struct itimerspec64 *old)
437{
438 struct fd f;
439 struct timerfd_ctx *ctx;
440 int ret;
441
442 if ((flags & ~TFD_SETTIME_FLAGS) ||
443 !itimerspec64_valid(new))
444 return -EINVAL;
445
446 ret = timerfd_fget(ufd, &f);
447 if (ret)
448 return ret;
449 ctx = f.file->private_data;
450
451 if (isalarm(ctx) && !capable(CAP_WAKE_ALARM)) {
452 fdput(f);
453 return -EPERM;
454 }
455
456 timerfd_setup_cancel(ctx, flags);
457
458 /*
459 * We need to stop the existing timer before reprogramming
460 * it to the new values.
461 */
462 for (;;) {
463 spin_lock_irq(&ctx->wqh.lock);
464
465 if (isalarm(ctx)) {
466 if (alarm_try_to_cancel(&ctx->t.alarm) >= 0)
467 break;
468 } else {
469 if (hrtimer_try_to_cancel(&ctx->t.tmr) >= 0)
470 break;
471 }
472 spin_unlock_irq(&ctx->wqh.lock);
473 cpu_relax();
474 }
475
476 /*
477 * If the timer is expired and it's periodic, we need to advance it
478 * because the caller may want to know the previous expiration time.
479 * We do not update "ticks" and "expired" since the timer will be
480 * re-programmed again in the following timerfd_setup() call.
481 */
482 if (ctx->expired && ctx->tintv) {
483 if (isalarm(ctx))
484 alarm_forward_now(&ctx->t.alarm, ctx->tintv);
485 else
486 hrtimer_forward_now(&ctx->t.tmr, ctx->tintv);
487 }
488
489 old->it_value = ktime_to_timespec64(timerfd_get_remaining(ctx));
490 old->it_interval = ktime_to_timespec64(ctx->tintv);
491
492 /*
493 * Re-program the timer to the new value ...
494 */
495 ret = timerfd_setup(ctx, flags, new);
496
497 spin_unlock_irq(&ctx->wqh.lock);
498 fdput(f);
499 return ret;
500}
501
502static int do_timerfd_gettime(int ufd, struct itimerspec64 *t)
503{
504 struct fd f;
505 struct timerfd_ctx *ctx;
506 int ret = timerfd_fget(ufd, &f);
507 if (ret)
508 return ret;
509 ctx = f.file->private_data;
510
511 spin_lock_irq(&ctx->wqh.lock);
512 if (ctx->expired && ctx->tintv) {
513 ctx->expired = 0;
514
515 if (isalarm(ctx)) {
516 ctx->ticks +=
517 alarm_forward_now(
518 &ctx->t.alarm, ctx->tintv) - 1;
519 alarm_restart(&ctx->t.alarm);
520 } else {
521 ctx->ticks +=
522 hrtimer_forward_now(&ctx->t.tmr, ctx->tintv)
523 - 1;
524 hrtimer_restart(&ctx->t.tmr);
525 }
526 }
527 t->it_value = ktime_to_timespec64(timerfd_get_remaining(ctx));
528 t->it_interval = ktime_to_timespec64(ctx->tintv);
529 spin_unlock_irq(&ctx->wqh.lock);
530 fdput(f);
531 return 0;
532}
533
534SYSCALL_DEFINE4(timerfd_settime, int, ufd, int, flags,
535 const struct itimerspec __user *, utmr,
536 struct itimerspec __user *, otmr)
537{
538 struct itimerspec64 new, old;
539 int ret;
540
541 if (get_itimerspec64(&new, utmr))
542 return -EFAULT;
543 ret = do_timerfd_settime(ufd, flags, &new, &old);
544 if (ret)
545 return ret;
546 if (otmr && put_itimerspec64(&old, otmr))
547 return -EFAULT;
548
549 return ret;
550}
551
552SYSCALL_DEFINE2(timerfd_gettime, int, ufd, struct itimerspec __user *, otmr)
553{
554 struct itimerspec64 kotmr;
555 int ret = do_timerfd_gettime(ufd, &kotmr);
556 if (ret)
557 return ret;
558 return put_itimerspec64(&kotmr, otmr) ? -EFAULT : 0;
559}
560
561#ifdef CONFIG_COMPAT
562COMPAT_SYSCALL_DEFINE4(timerfd_settime, int, ufd, int, flags,
563 const struct compat_itimerspec __user *, utmr,
564 struct compat_itimerspec __user *, otmr)
565{
566 struct itimerspec64 new, old;
567 int ret;
568
569 if (get_compat_itimerspec64(&new, utmr))
570 return -EFAULT;
571 ret = do_timerfd_settime(ufd, flags, &new, &old);
572 if (ret)
573 return ret;
574 if (otmr && put_compat_itimerspec64(&old, otmr))
575 return -EFAULT;
576 return ret;
577}
578
579COMPAT_SYSCALL_DEFINE2(timerfd_gettime, int, ufd,
580 struct compat_itimerspec __user *, otmr)
581{
582 struct itimerspec64 kotmr;
583 int ret = do_timerfd_gettime(ufd, &kotmr);
584 if (ret)
585 return ret;
586 return put_compat_itimerspec64(&kotmr, otmr) ? -EFAULT : 0;
587}
588#endif