1 // SPDX-License-Identifier: GPL-2.0
5 * Copyright (C) 2007 Davide Libenzi <davidel@xmailserver.org>
8 * Thanks to Thomas Gleixner for code reviews and useful comments.
12 #include <linux/alarmtimer.h>
13 #include <linux/file.h>
14 #include <linux/poll.h>
15 #include <linux/init.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>
38 wait_queue_head_t wqh;
41 short unsigned expired;
42 short unsigned settime_flags; /* to show in fdinfo */
44 struct list_head clist;
45 spinlock_t cancel_lock;
49 static LIST_HEAD(cancel_list);
50 static DEFINE_SPINLOCK(cancel_lock);
52 static inline bool isalarm(struct timerfd_ctx *ctx)
54 return ctx->clockid == CLOCK_REALTIME_ALARM ||
55 ctx->clockid == CLOCK_BOOTTIME_ALARM;
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.
63 static void timerfd_triggered(struct timerfd_ctx *ctx)
67 spin_lock_irqsave(&ctx->wqh.lock, flags);
70 wake_up_locked_poll(&ctx->wqh, EPOLLIN);
71 spin_unlock_irqrestore(&ctx->wqh.lock, flags);
74 static enum hrtimer_restart timerfd_tmrproc(struct hrtimer *htmr)
76 struct timerfd_ctx *ctx = container_of(htmr, struct timerfd_ctx,
78 timerfd_triggered(ctx);
79 return HRTIMER_NORESTART;
82 static enum alarmtimer_restart timerfd_alarmproc(struct alarm *alarm,
85 struct timerfd_ctx *ctx = container_of(alarm, struct timerfd_ctx,
87 timerfd_triggered(ctx);
88 return ALARMTIMER_NORESTART;
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().
97 void timerfd_clock_was_set(void)
99 ktime_t moffs = ktime_mono_to_real(0);
100 struct timerfd_ctx *ctx;
104 list_for_each_entry_rcu(ctx, &cancel_list, clist) {
105 if (!ctx->might_cancel)
107 spin_lock_irqsave(&ctx->wqh.lock, flags);
108 if (ctx->moffs != moffs) {
109 ctx->moffs = KTIME_MAX;
111 wake_up_locked_poll(&ctx->wqh, EPOLLIN);
113 spin_unlock_irqrestore(&ctx->wqh.lock, flags);
118 static void timerfd_resume_work(struct work_struct *work)
120 timerfd_clock_was_set();
123 static DECLARE_WORK(timerfd_work, timerfd_resume_work);
126 * Invoked from timekeeping_resume(). Defer the actual update to work so
127 * timerfd_clock_was_set() runs in task context.
129 void timerfd_resume(void)
131 schedule_work(&timerfd_work);
134 static void __timerfd_remove_cancel(struct timerfd_ctx *ctx)
136 if (ctx->might_cancel) {
137 ctx->might_cancel = false;
138 spin_lock(&cancel_lock);
139 list_del_rcu(&ctx->clist);
140 spin_unlock(&cancel_lock);
144 static void timerfd_remove_cancel(struct timerfd_ctx *ctx)
146 spin_lock(&ctx->cancel_lock);
147 __timerfd_remove_cancel(ctx);
148 spin_unlock(&ctx->cancel_lock);
151 static bool timerfd_canceled(struct timerfd_ctx *ctx)
153 if (!ctx->might_cancel || ctx->moffs != KTIME_MAX)
155 ctx->moffs = ktime_mono_to_real(0);
159 static void timerfd_setup_cancel(struct timerfd_ctx *ctx, int flags)
161 spin_lock(&ctx->cancel_lock);
162 if ((ctx->clockid == CLOCK_REALTIME ||
163 ctx->clockid == CLOCK_REALTIME_ALARM) &&
164 (flags & TFD_TIMER_ABSTIME) && (flags & TFD_TIMER_CANCEL_ON_SET)) {
165 if (!ctx->might_cancel) {
166 ctx->might_cancel = true;
167 spin_lock(&cancel_lock);
168 list_add_rcu(&ctx->clist, &cancel_list);
169 spin_unlock(&cancel_lock);
172 __timerfd_remove_cancel(ctx);
174 spin_unlock(&ctx->cancel_lock);
177 static ktime_t timerfd_get_remaining(struct timerfd_ctx *ctx)
182 remaining = alarm_expires_remaining(&ctx->t.alarm);
184 remaining = hrtimer_expires_remaining_adjusted(&ctx->t.tmr);
186 return remaining < 0 ? 0: remaining;
189 static int timerfd_setup(struct timerfd_ctx *ctx, int flags,
190 const struct itimerspec64 *ktmr)
192 enum hrtimer_mode htmode;
194 int clockid = ctx->clockid;
196 htmode = (flags & TFD_TIMER_ABSTIME) ?
197 HRTIMER_MODE_ABS: HRTIMER_MODE_REL;
199 texp = timespec64_to_ktime(ktmr->it_value);
202 ctx->tintv = timespec64_to_ktime(ktmr->it_interval);
205 alarm_init(&ctx->t.alarm,
206 ctx->clockid == CLOCK_REALTIME_ALARM ?
207 ALARM_REALTIME : ALARM_BOOTTIME,
210 hrtimer_init(&ctx->t.tmr, clockid, htmode);
211 hrtimer_set_expires(&ctx->t.tmr, texp);
212 ctx->t.tmr.function = timerfd_tmrproc;
216 if (flags & TFD_TIMER_ABSTIME)
217 texp = timens_ktime_to_host(clockid, texp);
219 if (flags & TFD_TIMER_ABSTIME)
220 alarm_start(&ctx->t.alarm, texp);
222 alarm_start_relative(&ctx->t.alarm, texp);
224 hrtimer_start(&ctx->t.tmr, texp, htmode);
227 if (timerfd_canceled(ctx))
231 ctx->settime_flags = flags & TFD_SETTIME_FLAGS;
235 static int timerfd_release(struct inode *inode, struct file *file)
237 struct timerfd_ctx *ctx = file->private_data;
239 timerfd_remove_cancel(ctx);
242 alarm_cancel(&ctx->t.alarm);
244 hrtimer_cancel(&ctx->t.tmr);
249 static __poll_t timerfd_poll(struct file *file, poll_table *wait)
251 struct timerfd_ctx *ctx = file->private_data;
255 poll_wait(file, &ctx->wqh, wait);
257 spin_lock_irqsave(&ctx->wqh.lock, flags);
260 spin_unlock_irqrestore(&ctx->wqh.lock, flags);
265 static ssize_t timerfd_read(struct file *file, char __user *buf, size_t count,
268 struct timerfd_ctx *ctx = file->private_data;
272 if (count < sizeof(ticks))
274 spin_lock_irq(&ctx->wqh.lock);
275 if (file->f_flags & O_NONBLOCK)
278 res = wait_event_interruptible_locked_irq(ctx->wqh, ctx->ticks);
281 * If clock has changed, we do not care about the
282 * ticks and we do not rearm the timer. Userspace must
285 if (timerfd_canceled(ctx)) {
294 if (ctx->expired && ctx->tintv) {
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.
302 ticks += alarm_forward_now(
303 &ctx->t.alarm, ctx->tintv) - 1;
304 alarm_restart(&ctx->t.alarm);
306 ticks += hrtimer_forward_now(&ctx->t.tmr,
308 hrtimer_restart(&ctx->t.tmr);
314 spin_unlock_irq(&ctx->wqh.lock);
316 res = put_user(ticks, (u64 __user *) buf) ? -EFAULT: sizeof(ticks);
320 #ifdef CONFIG_PROC_FS
321 static void timerfd_show(struct seq_file *m, struct file *file)
323 struct timerfd_ctx *ctx = file->private_data;
324 struct timespec64 value, interval;
326 spin_lock_irq(&ctx->wqh.lock);
327 value = ktime_to_timespec64(timerfd_get_remaining(ctx));
328 interval = ktime_to_timespec64(ctx->tintv);
329 spin_unlock_irq(&ctx->wqh.lock);
334 "settime flags: 0%o\n"
335 "it_value: (%llu, %llu)\n"
336 "it_interval: (%llu, %llu)\n",
338 (unsigned long long)ctx->ticks,
340 (unsigned long long)value.tv_sec,
341 (unsigned long long)value.tv_nsec,
342 (unsigned long long)interval.tv_sec,
343 (unsigned long long)interval.tv_nsec);
346 #define timerfd_show NULL
349 #ifdef CONFIG_CHECKPOINT_RESTORE
350 static long timerfd_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
352 struct timerfd_ctx *ctx = file->private_data;
356 case TFD_IOC_SET_TICKS: {
359 if (copy_from_user(&ticks, (u64 __user *)arg, sizeof(ticks)))
364 spin_lock_irq(&ctx->wqh.lock);
365 if (!timerfd_canceled(ctx)) {
367 wake_up_locked_poll(&ctx->wqh, EPOLLIN);
370 spin_unlock_irq(&ctx->wqh.lock);
381 #define timerfd_ioctl NULL
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,
393 static int timerfd_fget(int fd, struct fd *p)
395 struct fd f = fdget(fd);
398 if (f.file->f_op != &timerfd_fops) {
406 SYSCALL_DEFINE2(timerfd_create, int, clockid, int, flags)
409 struct timerfd_ctx *ctx;
411 /* Check the TFD_* constants for consistency. */
412 BUILD_BUG_ON(TFD_CLOEXEC != O_CLOEXEC);
413 BUILD_BUG_ON(TFD_NONBLOCK != O_NONBLOCK);
415 if ((flags & ~TFD_CREATE_FLAGS) ||
416 (clockid != CLOCK_MONOTONIC &&
417 clockid != CLOCK_REALTIME &&
418 clockid != CLOCK_REALTIME_ALARM &&
419 clockid != CLOCK_BOOTTIME &&
420 clockid != CLOCK_BOOTTIME_ALARM))
423 if ((clockid == CLOCK_REALTIME_ALARM ||
424 clockid == CLOCK_BOOTTIME_ALARM) &&
425 !capable(CAP_WAKE_ALARM))
428 ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
432 init_waitqueue_head(&ctx->wqh);
433 spin_lock_init(&ctx->cancel_lock);
434 ctx->clockid = clockid;
437 alarm_init(&ctx->t.alarm,
438 ctx->clockid == CLOCK_REALTIME_ALARM ?
439 ALARM_REALTIME : ALARM_BOOTTIME,
442 hrtimer_init(&ctx->t.tmr, clockid, HRTIMER_MODE_ABS);
444 ctx->moffs = ktime_mono_to_real(0);
446 ufd = anon_inode_getfd("[timerfd]", &timerfd_fops, ctx,
447 O_RDWR | (flags & TFD_SHARED_FCNTL_FLAGS));
454 static int do_timerfd_settime(int ufd, int flags,
455 const struct itimerspec64 *new,
456 struct itimerspec64 *old)
459 struct timerfd_ctx *ctx;
462 if ((flags & ~TFD_SETTIME_FLAGS) ||
463 !itimerspec64_valid(new))
466 ret = timerfd_fget(ufd, &f);
469 ctx = f.file->private_data;
471 if (isalarm(ctx) && !capable(CAP_WAKE_ALARM)) {
476 timerfd_setup_cancel(ctx, flags);
479 * We need to stop the existing timer before reprogramming
480 * it to the new values.
483 spin_lock_irq(&ctx->wqh.lock);
486 if (alarm_try_to_cancel(&ctx->t.alarm) >= 0)
489 if (hrtimer_try_to_cancel(&ctx->t.tmr) >= 0)
492 spin_unlock_irq(&ctx->wqh.lock);
495 hrtimer_cancel_wait_running(&ctx->t.alarm.timer);
497 hrtimer_cancel_wait_running(&ctx->t.tmr);
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.
506 if (ctx->expired && ctx->tintv) {
508 alarm_forward_now(&ctx->t.alarm, ctx->tintv);
510 hrtimer_forward_now(&ctx->t.tmr, ctx->tintv);
513 old->it_value = ktime_to_timespec64(timerfd_get_remaining(ctx));
514 old->it_interval = ktime_to_timespec64(ctx->tintv);
517 * Re-program the timer to the new value ...
519 ret = timerfd_setup(ctx, flags, new);
521 spin_unlock_irq(&ctx->wqh.lock);
526 static int do_timerfd_gettime(int ufd, struct itimerspec64 *t)
529 struct timerfd_ctx *ctx;
530 int ret = timerfd_fget(ufd, &f);
533 ctx = f.file->private_data;
535 spin_lock_irq(&ctx->wqh.lock);
536 if (ctx->expired && ctx->tintv) {
542 &ctx->t.alarm, ctx->tintv) - 1;
543 alarm_restart(&ctx->t.alarm);
546 hrtimer_forward_now(&ctx->t.tmr, ctx->tintv)
548 hrtimer_restart(&ctx->t.tmr);
551 t->it_value = ktime_to_timespec64(timerfd_get_remaining(ctx));
552 t->it_interval = ktime_to_timespec64(ctx->tintv);
553 spin_unlock_irq(&ctx->wqh.lock);
558 SYSCALL_DEFINE4(timerfd_settime, int, ufd, int, flags,
559 const struct __kernel_itimerspec __user *, utmr,
560 struct __kernel_itimerspec __user *, otmr)
562 struct itimerspec64 new, old;
565 if (get_itimerspec64(&new, utmr))
567 ret = do_timerfd_settime(ufd, flags, &new, &old);
570 if (otmr && put_itimerspec64(&old, otmr))
576 SYSCALL_DEFINE2(timerfd_gettime, int, ufd, struct __kernel_itimerspec __user *, otmr)
578 struct itimerspec64 kotmr;
579 int ret = do_timerfd_gettime(ufd, &kotmr);
582 return put_itimerspec64(&kotmr, otmr) ? -EFAULT : 0;
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)
590 struct itimerspec64 new, old;
593 if (get_old_itimerspec32(&new, utmr))
595 ret = do_timerfd_settime(ufd, flags, &new, &old);
598 if (otmr && put_old_itimerspec32(&old, otmr))
603 SYSCALL_DEFINE2(timerfd_gettime32, int, ufd,
604 struct old_itimerspec32 __user *, otmr)
606 struct itimerspec64 kotmr;
607 int ret = do_timerfd_gettime(ufd, &kotmr);
610 return put_old_itimerspec32(&kotmr, otmr) ? -EFAULT : 0;