1 /* 2 * fs/timerfd.c 3 * 4 * Copyright (C) 2007 Davide Libenzi <davidel@xmailserver.org> 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 29 struct 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 47 static LIST_HEAD(cancel_list); 48 static DEFINE_SPINLOCK(cancel_lock); 49 50 static 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 */ 61 static 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 72 static 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 80 static 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 */ 95 void 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 } 115 116 static 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 } 125 126 static 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 } 132 133 static 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 } 140 141 static 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 } 158 159 static 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 } 170 171 static 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 } 214 215 static 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 } 228 229 static 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 } 244 245 static 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 301 static 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 330 static 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 363 364 static 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 }; 372 373 static 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 } 385 386 SYSCALL_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 } 433 434 static 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 } 501 502 static 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 } 533 534 SYSCALL_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 } 551 552 SYSCALL_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 562 COMPAT_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 } 578 579 COMPAT_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 589