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1// SPDX-License-Identifier: GPL-2.02/*3 * fs/timerfd.c4 *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 31struct 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 49static LIST_HEAD(cancel_list);50static DEFINE_SPINLOCK(cancel_lock);51 52static inline bool isalarm(struct timerfd_ctx *ctx)53{54 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 */63static HWJS_SUSPENDS void timerfd_triggered(struct timerfd_ctx *ctx)64{65 unsigned long flags;66 67 spin_lock_irqsave(&ctx->wqh.lock, flags);68 ctx->expired = 1;69 ctx->ticks++;70 wake_up_locked_poll(&ctx->wqh, EPOLLIN);71 spin_unlock_irqrestore(&ctx->wqh.lock, flags);72}73 74static HWJS_SUSPENDS enum hrtimer_restart timerfd_tmrproc(struct hrtimer *htmr)75{76 struct timerfd_ctx *ctx = container_of(htmr, struct timerfd_ctx,77 t.tmr);78 timerfd_triggered(ctx);79 return HRTIMER_NORESTART;80}81 82static HWJS_SUSPENDS enum alarmtimer_restart timerfd_alarmproc(struct alarm *alarm,83 ktime_t now)84{85 struct timerfd_ctx *ctx = container_of(alarm, struct timerfd_ctx,86 t.alarm);87 timerfd_triggered(ctx);88 return ALARMTIMER_NORESTART;89}90 91/*92 * Called when the clock was set to cancel the timers in the cancel93 * list. This will wake up processes waiting on these timers. The94 * wake-up requires ctx->ticks to be non zero, therefore we increment95 * it before calling wake_up_locked().96 */97void timerfd_clock_was_set(void)98{99 ktime_t moffs = ktime_mono_to_real(0);100 struct timerfd_ctx *ctx;101 unsigned long flags;102 103 rcu_read_lock();104 list_for_each_entry_rcu(ctx, &cancel_list, clist) {105 if (!ctx->might_cancel)106 continue;107 spin_lock_irqsave(&ctx->wqh.lock, flags);108 if (ctx->moffs != moffs) {109 ctx->moffs = KTIME_MAX;110 ctx->ticks++;111 wake_up_locked_poll(&ctx->wqh, EPOLLIN);112 }113 spin_unlock_irqrestore(&ctx->wqh.lock, flags);114 }115 rcu_read_unlock();116}117 118static HWJS_SUSPENDS void timerfd_resume_work(struct work_struct *work)119{120 timerfd_clock_was_set();121}122 123static DECLARE_WORK(timerfd_work, timerfd_resume_work);124 125/*126 * Invoked from timekeeping_resume(). Defer the actual update to work so127 * timerfd_clock_was_set() runs in task context.128 */129void timerfd_resume(void)130{131 schedule_work(&timerfd_work);132}133 134static void __timerfd_remove_cancel(struct timerfd_ctx *ctx)135{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);141 }142}143 144static void timerfd_remove_cancel(struct timerfd_ctx *ctx)145{146 spin_lock(&ctx->cancel_lock);147 __timerfd_remove_cancel(ctx);148 spin_unlock(&ctx->cancel_lock);149}150 151static bool timerfd_canceled(struct timerfd_ctx *ctx)152{153 if (!ctx->might_cancel || ctx->moffs != KTIME_MAX)154 return false;155 ctx->moffs = ktime_mono_to_real(0);156 return true;157}158 159static void timerfd_setup_cancel(struct timerfd_ctx *ctx, int flags)160{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);170 }171 } else {172 __timerfd_remove_cancel(ctx);173 }174 spin_unlock(&ctx->cancel_lock);175}176 177static ktime_t timerfd_get_remaining(struct timerfd_ctx *ctx)178{179 ktime_t remaining;180 181 if (isalarm(ctx))182 remaining = alarm_expires_remaining(&ctx->t.alarm);183 else184 remaining = hrtimer_expires_remaining_adjusted(&ctx->t.tmr);185 186 return remaining < 0 ? 0: remaining;187}188 189static int timerfd_setup(struct timerfd_ctx *ctx, int flags,190 const struct itimerspec64 *ktmr)191{192 enum hrtimer_mode htmode;193 ktime_t texp;194 int clockid = ctx->clockid;195 196 htmode = (flags & TFD_TIMER_ABSTIME) ?197 HRTIMER_MODE_ABS: HRTIMER_MODE_REL;198 199 texp = timespec64_to_ktime(ktmr->it_value);200 ctx->expired = 0;201 ctx->ticks = 0;202 ctx->tintv = timespec64_to_ktime(ktmr->it_interval);203 204 if (isalarm(ctx)) {205 alarm_init(&ctx->t.alarm,206 ctx->clockid == CLOCK_REALTIME_ALARM ?207 ALARM_REALTIME : ALARM_BOOTTIME,208 timerfd_alarmproc);209 } else {210 hrtimer_init(&ctx->t.tmr, clockid, htmode);211 hrtimer_set_expires(&ctx->t.tmr, texp);212 ctx->t.tmr.function = timerfd_tmrproc;213 }214 215 if (texp != 0) {216 if (flags & TFD_TIMER_ABSTIME)217 texp = timens_ktime_to_host(clockid, texp);218 if (isalarm(ctx)) {219 if (flags & TFD_TIMER_ABSTIME)220 alarm_start(&ctx->t.alarm, texp);221 else222 alarm_start_relative(&ctx->t.alarm, texp);223 } else {224 hrtimer_start(&ctx->t.tmr, texp, htmode);225 }226 227 if (timerfd_canceled(ctx))228 return -ECANCELED;229 }230 231 ctx->settime_flags = flags & TFD_SETTIME_FLAGS;232 return 0;233}234 235static HWJS_SUSPENDS int timerfd_release(struct inode *inode, struct file *file)236{237 struct timerfd_ctx *ctx = file->private_data;238 239 timerfd_remove_cancel(ctx);240 241 if (isalarm(ctx))242 alarm_cancel(&ctx->t.alarm);243 else244 hrtimer_cancel(&ctx->t.tmr);245 kfree_rcu(ctx, rcu);246 return 0;247}248 249static __poll_t timerfd_poll(struct file *file, poll_table *wait)250{251 struct timerfd_ctx *ctx = file->private_data;252 __poll_t events = 0;253 unsigned long flags;254 255 poll_wait(file, &ctx->wqh, wait);256 257 spin_lock_irqsave(&ctx->wqh.lock, flags);258 if (ctx->ticks)259 events |= EPOLLIN;260 spin_unlock_irqrestore(&ctx->wqh.lock, flags);261 262 return events;263}264 265static HWJS_SUSPENDS ssize_t timerfd_read_iter(struct kiocb *iocb, struct iov_iter *to)266{267 struct file *file = iocb->ki_filp;268 struct timerfd_ctx *ctx = file->private_data;269 ssize_t res;270 u64 ticks = 0;271 272 if (iov_iter_count(to) < sizeof(ticks))273 return -EINVAL;274 275 spin_lock_irq(&ctx->wqh.lock);276 if (file->f_flags & O_NONBLOCK || iocb->ki_flags & IOCB_NOWAIT)277 res = -EAGAIN;278 else279 res = wait_event_interruptible_locked_irq(ctx->wqh, ctx->ticks);280 281 /*282 * If clock has changed, we do not care about the283 * ticks and we do not rearm the timer. Userspace must284 * reevaluate anyway.285 */286 if (timerfd_canceled(ctx)) {287 ctx->ticks = 0;288 ctx->expired = 0;289 res = -ECANCELED;290 }291 292 if (ctx->ticks) {293 ticks = ctx->ticks;294 295 if (ctx->expired && ctx->tintv) {296 /*297 * If tintv != 0, this is a periodic timer that298 * needs to be re-armed. We avoid doing it in the timer299 * callback to avoid DoS attacks specifying a very300 * short timer period.301 */302 if (isalarm(ctx)) {303 ticks += alarm_forward_now(304 &ctx->t.alarm, ctx->tintv) - 1;305 alarm_restart(&ctx->t.alarm);306 } else {307 ticks += hrtimer_forward_now(&ctx->t.tmr,308 ctx->tintv) - 1;309 hrtimer_restart(&ctx->t.tmr);310 }311 }312 ctx->expired = 0;313 ctx->ticks = 0;314 }315 spin_unlock_irq(&ctx->wqh.lock);316 if (ticks) {317 res = copy_to_iter(&ticks, sizeof(ticks), to);318 if (!res)319 res = -EFAULT;320 }321 return res;322}323 324#ifdef CONFIG_PROC_FS325static void timerfd_show(struct seq_file *m, struct file *file)326{327 struct timerfd_ctx *ctx = file->private_data;328 struct timespec64 value, interval;329 330 spin_lock_irq(&ctx->wqh.lock);331 value = ktime_to_timespec64(timerfd_get_remaining(ctx));332 interval = ktime_to_timespec64(ctx->tintv);333 spin_unlock_irq(&ctx->wqh.lock);334 335 seq_printf(m,336 "clockid: %d\n"337 "ticks: %llu\n"338 "settime flags: 0%o\n"339 "it_value: (%llu, %llu)\n"340 "it_interval: (%llu, %llu)\n",341 ctx->clockid,342 (unsigned long long)ctx->ticks,343 ctx->settime_flags,344 (unsigned long long)value.tv_sec,345 (unsigned long long)value.tv_nsec,346 (unsigned long long)interval.tv_sec,347 (unsigned long long)interval.tv_nsec);348}349#else350#define timerfd_show NULL351#endif352 353#ifdef CONFIG_CHECKPOINT_RESTORE354static long timerfd_ioctl(struct file *file, unsigned int cmd, unsigned long arg)355{356 struct timerfd_ctx *ctx = file->private_data;357 int ret = 0;358 359 switch (cmd) {360 case TFD_IOC_SET_TICKS: {361 u64 ticks;362 363 if (copy_from_user(&ticks, (u64 __user *)arg, sizeof(ticks)))364 return -EFAULT;365 if (!ticks)366 return -EINVAL;367 368 spin_lock_irq(&ctx->wqh.lock);369 if (!timerfd_canceled(ctx)) {370 ctx->ticks = ticks;371 wake_up_locked_poll(&ctx->wqh, EPOLLIN);372 } else373 ret = -ECANCELED;374 spin_unlock_irq(&ctx->wqh.lock);375 break;376 }377 default:378 ret = -ENOTTY;379 break;380 }381 382 return ret;383}384#else385#define timerfd_ioctl NULL386#endif387 388static const struct file_operations timerfd_fops = {389 .release = timerfd_release,390 .poll = timerfd_poll,391 .read_iter = timerfd_read_iter,392 .llseek = noop_llseek,393 .show_fdinfo = timerfd_show,394 .unlocked_ioctl = timerfd_ioctl,395};396 397static int timerfd_fget(int fd, struct fd *p)398{399 struct fd f = fdget(fd);400 if (!fd_file(f))401 return -EBADF;402 if (fd_file(f)->f_op != &timerfd_fops) {403 fdput(f);404 return -EINVAL;405 }406 *p = f;407 return 0;408}409 410SYSCALL_DEFINE2(timerfd_create, int, clockid, int, flags)411{412 int ufd;413 struct timerfd_ctx *ctx;414 struct file *file;415 416 /* Check the TFD_* constants for consistency. */417 BUILD_BUG_ON(TFD_CLOEXEC != O_CLOEXEC);418 BUILD_BUG_ON(TFD_NONBLOCK != O_NONBLOCK);419 420 if ((flags & ~TFD_CREATE_FLAGS) ||421 (clockid != CLOCK_MONOTONIC &&422 clockid != CLOCK_REALTIME &&423 clockid != CLOCK_REALTIME_ALARM &&424 clockid != CLOCK_BOOTTIME &&425 clockid != CLOCK_BOOTTIME_ALARM))426 return -EINVAL;427 428 if ((clockid == CLOCK_REALTIME_ALARM ||429 clockid == CLOCK_BOOTTIME_ALARM) &&430 !capable(CAP_WAKE_ALARM))431 return -EPERM;432 433 ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);434 if (!ctx)435 return -ENOMEM;436 437 init_waitqueue_head(&ctx->wqh);438 spin_lock_init(&ctx->cancel_lock);439 ctx->clockid = clockid;440 441 if (isalarm(ctx))442 alarm_init(&ctx->t.alarm,443 ctx->clockid == CLOCK_REALTIME_ALARM ?444 ALARM_REALTIME : ALARM_BOOTTIME,445 timerfd_alarmproc);446 else447 hrtimer_init(&ctx->t.tmr, clockid, HRTIMER_MODE_ABS);448 449 ctx->moffs = ktime_mono_to_real(0);450 451 ufd = get_unused_fd_flags(flags & TFD_SHARED_FCNTL_FLAGS);452 if (ufd < 0) {453 kfree(ctx);454 return ufd;455 }456 457 file = anon_inode_getfile("[timerfd]", &timerfd_fops, ctx,458 O_RDWR | (flags & TFD_SHARED_FCNTL_FLAGS));459 if (IS_ERR(file)) {460 put_unused_fd(ufd);461 kfree(ctx);462 return PTR_ERR(file);463 }464 465 file->f_mode |= FMODE_NOWAIT;466 fd_install(ufd, file);467 return ufd;468}469 470static int do_timerfd_settime(int ufd, int flags, 471 const struct itimerspec64 *new,472 struct itimerspec64 *old)473{474 struct fd f;475 struct timerfd_ctx *ctx;476 int ret;477 478 if ((flags & ~TFD_SETTIME_FLAGS) ||479 !itimerspec64_valid(new))480 return -EINVAL;481 482 ret = timerfd_fget(ufd, &f);483 if (ret)484 return ret;485 ctx = fd_file(f)->private_data;486 487 if (isalarm(ctx) && !capable(CAP_WAKE_ALARM)) {488 fdput(f);489 return -EPERM;490 }491 492 timerfd_setup_cancel(ctx, flags);493 494 /*495 * We need to stop the existing timer before reprogramming496 * it to the new values.497 */498 for (;;) {499 spin_lock_irq(&ctx->wqh.lock);500 501 if (isalarm(ctx)) {502 if (alarm_try_to_cancel(&ctx->t.alarm) >= 0)503 break;504 } else {505 if (hrtimer_try_to_cancel(&ctx->t.tmr) >= 0)506 break;507 }508 spin_unlock_irq(&ctx->wqh.lock);509 510 if (isalarm(ctx))511 hrtimer_cancel_wait_running(&ctx->t.alarm.timer);512 else513 hrtimer_cancel_wait_running(&ctx->t.tmr);514 }515 516 /*517 * If the timer is expired and it's periodic, we need to advance it518 * because the caller may want to know the previous expiration time.519 * We do not update "ticks" and "expired" since the timer will be520 * re-programmed again in the following timerfd_setup() call.521 */522 if (ctx->expired && ctx->tintv) {523 if (isalarm(ctx))524 alarm_forward_now(&ctx->t.alarm, ctx->tintv);525 else526 hrtimer_forward_now(&ctx->t.tmr, ctx->tintv);527 }528 529 old->it_value = ktime_to_timespec64(timerfd_get_remaining(ctx));530 old->it_interval = ktime_to_timespec64(ctx->tintv);531 532 /*533 * Re-program the timer to the new value ...534 */535 ret = timerfd_setup(ctx, flags, new);536 537 spin_unlock_irq(&ctx->wqh.lock);538 fdput(f);539 return ret;540}541 542static int do_timerfd_gettime(int ufd, struct itimerspec64 *t)543{544 struct fd f;545 struct timerfd_ctx *ctx;546 int ret = timerfd_fget(ufd, &f);547 if (ret)548 return ret;549 ctx = fd_file(f)->private_data;550 551 spin_lock_irq(&ctx->wqh.lock);552 if (ctx->expired && ctx->tintv) {553 ctx->expired = 0;554 555 if (isalarm(ctx)) {556 ctx->ticks +=557 alarm_forward_now(558 &ctx->t.alarm, ctx->tintv) - 1;559 alarm_restart(&ctx->t.alarm);560 } else {561 ctx->ticks +=562 hrtimer_forward_now(&ctx->t.tmr, ctx->tintv)563 - 1;564 hrtimer_restart(&ctx->t.tmr);565 }566 }567 t->it_value = ktime_to_timespec64(timerfd_get_remaining(ctx));568 t->it_interval = ktime_to_timespec64(ctx->tintv);569 spin_unlock_irq(&ctx->wqh.lock);570 fdput(f);571 return 0;572}573 574SYSCALL_DEFINE4(timerfd_settime, int, ufd, int, flags,575 const struct __kernel_itimerspec __user *, utmr,576 struct __kernel_itimerspec __user *, otmr)577{578 struct itimerspec64 new, old;579 int ret;580 581 if (get_itimerspec64(&new, utmr))582 return -EFAULT;583 ret = do_timerfd_settime(ufd, flags, &new, &old);584 if (ret)585 return ret;586 if (otmr && put_itimerspec64(&old, otmr))587 return -EFAULT;588 589 return ret;590}591 592SYSCALL_DEFINE2(timerfd_gettime, int, ufd, struct __kernel_itimerspec __user *, otmr)593{594 struct itimerspec64 kotmr;595 int ret = do_timerfd_gettime(ufd, &kotmr);596 if (ret)597 return ret;598 return put_itimerspec64(&kotmr, otmr) ? -EFAULT : 0;599}600 601#ifdef CONFIG_COMPAT_32BIT_TIME602SYSCALL_DEFINE4(timerfd_settime32, int, ufd, int, flags,603 const struct old_itimerspec32 __user *, utmr,604 struct old_itimerspec32 __user *, otmr)605{606 struct itimerspec64 new, old;607 int ret;608 609 if (get_old_itimerspec32(&new, utmr))610 return -EFAULT;611 ret = do_timerfd_settime(ufd, flags, &new, &old);612 if (ret)613 return ret;614 if (otmr && put_old_itimerspec32(&old, otmr))615 return -EFAULT;616 return ret;617}618 619SYSCALL_DEFINE2(timerfd_gettime32, int, ufd,620 struct old_itimerspec32 __user *, otmr)621{622 struct itimerspec64 kotmr;623 int ret = do_timerfd_gettime(ufd, &kotmr);624 if (ret)625 return ret;626 return put_old_itimerspec32(&kotmr, otmr) ? -EFAULT : 0;627}628#endif629