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#include <linux/alarmtimer.h>#include <linux/file.h>#include <linux/poll.h>#include <linux/init.h>#include <linux/fs.h>#include <linux/sched.h>#include <linux/kernel.h>#include <linux/slab.h>#include <linux/list.h>#include <linux/spinlock.h>#include <linux/time.h>#include <linux/hrtimer.h>#include <linux/anon_inodes.h>#include <linux/timerfd.h>#include <linux/syscalls.h>#include <linux/compat.h>#include <linux/rcupdate.h>#include <linux/time_namespace.h>
struct timerfd_ctx { union { struct hrtimer tmr; struct alarm alarm; } t; ktime_t tintv; ktime_t moffs; wait_queue_head_t wqh; u64 ticks; int clockid; short unsigned expired; short unsigned settime_flags; /* to show in fdinfo */ struct rcu_head rcu; struct list_head clist; spinlock_t cancel_lock; bool might_cancel;};
static LIST_HEAD(cancel_list);static DEFINE_SPINLOCK(cancel_lock);
static inline bool isalarm(struct timerfd_ctx *ctx){ return ctx->clockid == CLOCK_REALTIME_ALARM || ctx->clockid == CLOCK_BOOTTIME_ALARM;}
static void __timerfd_triggered(struct timerfd_ctx *ctx){ lockdep_assert_held(&ctx->wqh.lock);
ctx->expired = 1; ctx->ticks++; wake_up_locked_poll(&ctx->wqh, EPOLLIN);}
/* * This gets called when the timer event triggers. We set the "expired" * flag, but we do not re-arm the timer (in case it's necessary, * tintv != 0) until the timer is accessed. */static void timerfd_triggered(struct timerfd_ctx *ctx){ guard(spinlock_irqsave)(&ctx->wqh.lock); __timerfd_triggered(ctx);}
static enum hrtimer_restart timerfd_tmrproc(struct hrtimer *htmr){ struct timerfd_ctx *ctx = container_of(htmr, struct timerfd_ctx, t.tmr); timerfd_triggered(ctx); return HRTIMER_NORESTART;}
static void timerfd_alarmproc(struct alarm *alarm, ktime_t now){ struct timerfd_ctx *ctx = container_of(alarm, struct timerfd_ctx, t.alarm); timerfd_triggered(ctx);}
/* * Called when the clock was set to cancel the timers in the cancel * list. This will wake up processes waiting on these timers. The * wake-up requires ctx->ticks to be non zero, therefore we increment * it before calling wake_up_locked(). */void timerfd_clock_was_set(void){ ktime_t moffs = ktime_mono_to_real(0); struct timerfd_ctx *ctx; unsigned long flags;
rcu_read_lock(); list_for_each_entry_rcu(ctx, &cancel_list, clist) { if (!ctx->might_cancel) continue; spin_lock_irqsave(&ctx->wqh.lock, flags); if (ctx->moffs != moffs) { ctx->moffs = KTIME_MAX; ctx->ticks++; wake_up_locked_poll(&ctx->wqh, EPOLLIN); } spin_unlock_irqrestore(&ctx->wqh.lock, flags); } rcu_read_unlock();}
static void timerfd_resume_work(struct work_struct *work){ timerfd_clock_was_set();}
static DECLARE_WORK(timerfd_work, timerfd_resume_work);
/* * Invoked from timekeeping_resume(). Defer the actual update to work so * timerfd_clock_was_set() runs in task context. */void timerfd_resume(void){ schedule_work(&timerfd_work);}
static void __timerfd_remove_cancel(struct timerfd_ctx *ctx){ if (ctx->might_cancel) { ctx->might_cancel = false; spin_lock(&cancel_lock); list_del_rcu(&ctx->clist); spin_unlock(&cancel_lock); }}
static void timerfd_remove_cancel(struct timerfd_ctx *ctx){ spin_lock(&ctx->cancel_lock); __timerfd_remove_cancel(ctx); spin_unlock(&ctx->cancel_lock);}
static bool timerfd_canceled(struct timerfd_ctx *ctx){ if (!ctx->might_cancel || ctx->moffs != KTIME_MAX) return false; ctx->moffs = ktime_mono_to_real(0); return true;}
static void timerfd_setup_cancel(struct timerfd_ctx *ctx, int flags){ spin_lock(&ctx->cancel_lock); if ((ctx->clockid == CLOCK_REALTIME || ctx->clockid == CLOCK_REALTIME_ALARM) && (flags & TFD_TIMER_ABSTIME) && (flags & TFD_TIMER_CANCEL_ON_SET)) { if (!ctx->might_cancel) { ctx->might_cancel = true; spin_lock(&cancel_lock); list_add_rcu(&ctx->clist, &cancel_list); spin_unlock(&cancel_lock); } } else { __timerfd_remove_cancel(ctx); } spin_unlock(&ctx->cancel_lock);}
static ktime_t timerfd_get_remaining(struct timerfd_ctx *ctx){ ktime_t remaining;
if (isalarm(ctx)) remaining = alarm_expires_remaining(&ctx->t.alarm); else remaining = hrtimer_expires_remaining_adjusted(&ctx->t.tmr);
return remaining < 0 ? 0: remaining;}
static void timerfd_alarm_start(struct timerfd_ctx *ctx, ktime_t exp, bool relative){ /* Start the timer. If it's expired already, handle the callback. */ if (!alarm_start_timer(&ctx->t.alarm, exp, relative)) __timerfd_triggered(ctx);}
static u64 timerfd_alarm_restart(struct timerfd_ctx *ctx){ /* -1 to account for ctx->ticks++ in __timerfd_triggered() */ u64 ticks = alarm_forward_now(&ctx->t.alarm, ctx->tintv) - 1;
timerfd_alarm_start(ctx, alarm_get_expires(&ctx->t.alarm), false); return ticks;}
static void timerfd_hrtimer_start(struct timerfd_ctx *ctx, ktime_t exp, const enum hrtimer_mode mode){ /* Start the timer. If it's expired already, handle the callback. */ if (!hrtimer_start_range_ns_user(&ctx->t.tmr, exp, 0, mode)) __timerfd_triggered(ctx);}
static u64 timerfd_hrtimer_restart(struct timerfd_ctx *ctx){ /* -1 to account for ctx->ticks++ in __timerfd_triggered() */ u64 ticks = hrtimer_forward_now(&ctx->t.tmr, ctx->tintv) - 1;
timerfd_hrtimer_start(ctx, hrtimer_get_expires(&ctx->t.tmr), HRTIMER_MODE_ABS); return ticks;}
static u64 timerfd_restart(struct timerfd_ctx *ctx){ if (isalarm(ctx)) return timerfd_alarm_restart(ctx); return timerfd_hrtimer_restart(ctx);}
static int timerfd_setup(struct timerfd_ctx *ctx, int flags, const struct itimerspec64 *ktmr){ int clockid = ctx->clockid; enum hrtimer_mode htmode; ktime_t texp;
htmode = (flags & TFD_TIMER_ABSTIME) ? HRTIMER_MODE_ABS: HRTIMER_MODE_REL;
texp = timespec64_to_ktime(ktmr->it_value); ctx->expired = 0; ctx->ticks = 0; ctx->tintv = timespec64_to_ktime(ktmr->it_interval);
if (isalarm(ctx)) { alarm_init(&ctx->t.alarm, ctx->clockid == CLOCK_REALTIME_ALARM ? ALARM_REALTIME : ALARM_BOOTTIME, timerfd_alarmproc); } else { hrtimer_setup(&ctx->t.tmr, timerfd_tmrproc, clockid, htmode); }
if (texp != 0) { if (flags & TFD_TIMER_ABSTIME) texp = timens_ktime_to_host(clockid, texp); if (isalarm(ctx)) timerfd_alarm_start(ctx, texp, !(flags & TFD_TIMER_ABSTIME)); else timerfd_hrtimer_start(ctx, texp, htmode);
if (timerfd_canceled(ctx)) return -ECANCELED; }
ctx->settime_flags = flags & TFD_SETTIME_FLAGS; return 0;}
static int timerfd_release(struct inode *inode, struct file *file){ struct timerfd_ctx *ctx = file->private_data;
timerfd_remove_cancel(ctx);
if (isalarm(ctx)) alarm_cancel(&ctx->t.alarm); else hrtimer_cancel(&ctx->t.tmr); kfree_rcu(ctx, rcu); return 0;}
static __poll_t timerfd_poll(struct file *file, poll_table *wait){ struct timerfd_ctx *ctx = file->private_data; __poll_t events = 0; unsigned long flags;
poll_wait(file, &ctx->wqh, wait);
spin_lock_irqsave(&ctx->wqh.lock, flags); if (ctx->ticks) events |= EPOLLIN; spin_unlock_irqrestore(&ctx->wqh.lock, flags);
return events;}
static ssize_t timerfd_read_iter(struct kiocb *iocb, struct iov_iter *to){ struct file *file = iocb->ki_filp; struct timerfd_ctx *ctx = file->private_data; ssize_t res; u64 ticks = 0;
if (iov_iter_count(to) < sizeof(ticks)) return -EINVAL;
spin_lock_irq(&ctx->wqh.lock); if (file->f_flags & O_NONBLOCK || iocb->ki_flags & IOCB_NOWAIT) res = -EAGAIN; else res = wait_event_interruptible_locked_irq(ctx->wqh, ctx->ticks);
/* * If clock has changed, we do not care about the * ticks and we do not rearm the timer. Userspace must * reevaluate anyway. */ if (timerfd_canceled(ctx)) { ctx->ticks = 0; ctx->expired = 0; res = -ECANCELED; }
if (ctx->ticks) { unsigned int expired = ctx->expired;
ticks = ctx->ticks; ctx->expired = 0; ctx->ticks = 0;
/* * If tintv != 0, this is a periodic timer that needs to be * re-armed. We avoid doing it in the timer callback to avoid * DoS attacks specifying a very short timer period. */ if (expired && ctx->tintv) ticks += timerfd_restart(ctx); } spin_unlock_irq(&ctx->wqh.lock); if (ticks) { res = copy_to_iter(&ticks, sizeof(ticks), to); if (!res) res = -EFAULT; } return res;}
#ifdef CONFIG_PROC_FSstatic void timerfd_show(struct seq_file *m, struct file *file){ struct timerfd_ctx *ctx = file->private_data; struct timespec64 value, interval;
spin_lock_irq(&ctx->wqh.lock); value = ktime_to_timespec64(timerfd_get_remaining(ctx)); interval = ktime_to_timespec64(ctx->tintv); spin_unlock_irq(&ctx->wqh.lock);
seq_printf(m, "clockid: %d\n" "ticks: %llu\n" "settime flags: 0%o\n" "it_value: (%llu, %llu)\n" "it_interval: (%llu, %llu)\n", ctx->clockid, (unsigned long long)ctx->ticks, ctx->settime_flags, (unsigned long long)value.tv_sec, (unsigned long long)value.tv_nsec, (unsigned long long)interval.tv_sec, (unsigned long long)interval.tv_nsec);}#else#define timerfd_show NULL#endif
#ifdef CONFIG_CHECKPOINT_RESTOREstatic long timerfd_ioctl(struct file *file, unsigned int cmd, unsigned long arg){ struct timerfd_ctx *ctx = file->private_data; int ret = 0;
switch (cmd) { case TFD_IOC_SET_TICKS: { u64 ticks;
if (copy_from_user(&ticks, (u64 __user *)arg, sizeof(ticks))) return -EFAULT; if (!ticks) return -EINVAL;
spin_lock_irq(&ctx->wqh.lock); if (!timerfd_canceled(ctx)) { ctx->ticks = ticks; wake_up_locked_poll(&ctx->wqh, EPOLLIN); } else ret = -ECANCELED; spin_unlock_irq(&ctx->wqh.lock); break; } default: ret = -ENOTTY; break; }
return ret;}#else#define timerfd_ioctl NULL#endif
static const struct file_operations timerfd_fops = { .release = timerfd_release, .poll = timerfd_poll, .read_iter = timerfd_read_iter, .llseek = noop_llseek, .show_fdinfo = timerfd_show, .unlocked_ioctl = timerfd_ioctl,};
SYSCALL_DEFINE2(timerfd_create, int, clockid, int, flags){ struct timerfd_ctx *ctx __free(kfree) = NULL; int ret;
/* Check the TFD_* constants for consistency. */ BUILD_BUG_ON(TFD_CLOEXEC != O_CLOEXEC); BUILD_BUG_ON(TFD_NONBLOCK != O_NONBLOCK);
if ((flags & ~TFD_CREATE_FLAGS) || (clockid != CLOCK_MONOTONIC && clockid != CLOCK_REALTIME && clockid != CLOCK_REALTIME_ALARM && clockid != CLOCK_BOOTTIME && clockid != CLOCK_BOOTTIME_ALARM)) return -EINVAL;
if ((clockid == CLOCK_REALTIME_ALARM || clockid == CLOCK_BOOTTIME_ALARM) && !capable(CAP_WAKE_ALARM)) return -EPERM;
ctx = kzalloc_obj(*ctx); if (!ctx) return -ENOMEM;
init_waitqueue_head(&ctx->wqh); spin_lock_init(&ctx->cancel_lock); ctx->clockid = clockid;
if (isalarm(ctx)) alarm_init(&ctx->t.alarm, ctx->clockid == CLOCK_REALTIME_ALARM ? ALARM_REALTIME : ALARM_BOOTTIME, timerfd_alarmproc); else hrtimer_setup(&ctx->t.tmr, timerfd_tmrproc, clockid, HRTIMER_MODE_ABS);
ctx->moffs = ktime_mono_to_real(0);
ret = FD_ADD(flags & TFD_SHARED_FCNTL_FLAGS, anon_inode_getfile_fmode("[timerfd]", &timerfd_fops, ctx, O_RDWR | (flags & TFD_SHARED_FCNTL_FLAGS), FMODE_NOWAIT)); if (ret >= 0) retain_and_null_ptr(ctx); return ret;}
static int do_timerfd_settime(int ufd, int flags, const struct itimerspec64 *new, struct itimerspec64 *old){ struct timerfd_ctx *ctx; int ret;
if ((flags & ~TFD_SETTIME_FLAGS) || !itimerspec64_valid(new)) return -EINVAL;
CLASS(fd, f)(ufd); if (fd_empty(f)) return -EBADF;
if (fd_file(f)->f_op != &timerfd_fops) return -EINVAL;
ctx = fd_file(f)->private_data;
if (isalarm(ctx) && !capable(CAP_WAKE_ALARM)) return -EPERM;
timerfd_setup_cancel(ctx, flags);
/* * We need to stop the existing timer before reprogramming * it to the new values. */ for (;;) { spin_lock_irq(&ctx->wqh.lock);
if (isalarm(ctx)) { if (alarm_try_to_cancel(&ctx->t.alarm) >= 0) break; } else { if (hrtimer_try_to_cancel(&ctx->t.tmr) >= 0) break; } spin_unlock_irq(&ctx->wqh.lock);
if (isalarm(ctx)) hrtimer_cancel_wait_running(&ctx->t.alarm.timer); else hrtimer_cancel_wait_running(&ctx->t.tmr); }
/* * If the timer is expired and it's periodic, we need to advance it * because the caller may want to know the previous expiration time. * We do not update "ticks" and "expired" since the timer will be * re-programmed again in the following timerfd_setup() call. */ if (ctx->expired && ctx->tintv) { if (isalarm(ctx)) alarm_forward_now(&ctx->t.alarm, ctx->tintv); else hrtimer_forward_now(&ctx->t.tmr, ctx->tintv); }
old->it_value = ktime_to_timespec64(timerfd_get_remaining(ctx)); old->it_interval = ktime_to_timespec64(ctx->tintv);
/* * Re-program the timer to the new value ... */ ret = timerfd_setup(ctx, flags, new);
spin_unlock_irq(&ctx->wqh.lock); return ret;}
static int do_timerfd_gettime(int ufd, struct itimerspec64 *t){ struct timerfd_ctx *ctx; CLASS(fd, f)(ufd);
if (fd_empty(f)) return -EBADF; if (fd_file(f)->f_op != &timerfd_fops) return -EINVAL; ctx = fd_file(f)->private_data;
spin_lock_irq(&ctx->wqh.lock); if (ctx->expired && ctx->tintv) { ctx->expired = 0; ctx->ticks += timerfd_restart(ctx); } t->it_value = ktime_to_timespec64(timerfd_get_remaining(ctx)); t->it_interval = ktime_to_timespec64(ctx->tintv); spin_unlock_irq(&ctx->wqh.lock); return 0;}
SYSCALL_DEFINE4(timerfd_settime, int, ufd, int, flags, const struct __kernel_itimerspec __user *, utmr, struct __kernel_itimerspec __user *, otmr){ struct itimerspec64 new, old; int ret;
if (get_itimerspec64(&new, utmr)) return -EFAULT; ret = do_timerfd_settime(ufd, flags, &new, &old); if (ret) return ret; if (otmr && put_itimerspec64(&old, otmr)) return -EFAULT;
return ret;}
SYSCALL_DEFINE2(timerfd_gettime, int, ufd, struct __kernel_itimerspec __user *, otmr){ struct itimerspec64 kotmr; int ret = do_timerfd_gettime(ufd, &kotmr); if (ret) return ret; return put_itimerspec64(&kotmr, otmr) ? -EFAULT : 0;}
#ifdef CONFIG_COMPAT_32BIT_TIMESYSCALL_DEFINE4(timerfd_settime32, int, ufd, int, flags, const struct old_itimerspec32 __user *, utmr, struct old_itimerspec32 __user *, otmr){ struct itimerspec64 new, old; int ret;
if (get_old_itimerspec32(&new, utmr)) return -EFAULT; ret = do_timerfd_settime(ufd, flags, &new, &old); if (ret) return ret; if (otmr && put_old_itimerspec32(&old, otmr)) return -EFAULT; return ret;}
SYSCALL_DEFINE2(timerfd_gettime32, int, ufd, struct old_itimerspec32 __user *, otmr){ struct itimerspec64 kotmr; int ret = do_timerfd_gettime(ufd, &kotmr); if (ret) return ret; return put_old_itimerspec32(&kotmr, otmr) ? -EFAULT : 0;}#endif