1 files changed, 568 insertions, 0 deletions

diff --git a/fs/timerfd.c b/fs/timerfd.c
new file mode 100644
index 000000000..b94fa6c3c
--- /dev/null
+++ b/fs/timerfd.c
@@ -0,0 +1,568 @@
+/*
+ *  fs/timerfd.c
+ *
+ *  Copyright (C) 2007  Davide Libenzi <davidel@xmailserver.org>
+ *
+ *
+ *  Thanks to Thomas Gleixner for code reviews and useful comments.
+ *
+ */
+
+#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>
+
+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;
+	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;
+}
+
+/*
+ * 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.tv64 != 0) until the timer is accessed.
+ */
+static void timerfd_triggered(struct timerfd_ctx *ctx)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&ctx->wqh.lock, flags);
+	ctx->expired = 1;
+	ctx->ticks++;
+	wake_up_locked(&ctx->wqh);
+	spin_unlock_irqrestore(&ctx->wqh.lock, flags);
+}
+
+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 enum alarmtimer_restart timerfd_alarmproc(struct alarm *alarm,
+	ktime_t now)
+{
+	struct timerfd_ctx *ctx = container_of(alarm, struct timerfd_ctx,
+					       t.alarm);
+	timerfd_triggered(ctx);
+	return ALARMTIMER_NORESTART;
+}
+
+/*
+ * 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((ktime_t){ .tv64 = 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.tv64 != moffs.tv64) {
+			ctx->moffs.tv64 = KTIME_MAX;
+			ctx->ticks++;
+			wake_up_locked(&ctx->wqh);
+		}
+		spin_unlock_irqrestore(&ctx->wqh.lock, flags);
+	}
+	rcu_read_unlock();
+}
+
+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 bool timerfd_canceled(struct timerfd_ctx *ctx)
+{
+	if (!ctx->might_cancel || ctx->moffs.tv64 != KTIME_MAX)
+		return false;
+	ctx->moffs = ktime_mono_to_real((ktime_t){ .tv64 = 0 });
+	return true;
+}
+
+static void timerfd_setup_cancel(struct timerfd_ctx *ctx, int flags)
+{
+	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 if (ctx->might_cancel) {
+		timerfd_remove_cancel(ctx);
+	}
+}
+
+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(&ctx->t.tmr);
+
+	return remaining.tv64 < 0 ? ktime_set(0, 0): remaining;
+}
+
+static int timerfd_setup(struct timerfd_ctx *ctx, int flags,
+			 const struct itimerspec *ktmr)
+{
+	enum hrtimer_mode htmode;
+	ktime_t texp;
+	int clockid = ctx->clockid;
+
+	htmode = (flags & TFD_TIMER_ABSTIME) ?
+		HRTIMER_MODE_ABS: HRTIMER_MODE_REL;
+
+	texp = timespec_to_ktime(ktmr->it_value);
+	ctx->expired = 0;
+	ctx->ticks = 0;
+	ctx->tintv = timespec_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_init(&ctx->t.tmr, clockid, htmode);
+		hrtimer_set_expires(&ctx->t.tmr, texp);
+		ctx->t.tmr.function = timerfd_tmrproc;
+	}
+
+	if (texp.tv64 != 0) {
+		if (isalarm(ctx)) {
+			if (flags & TFD_TIMER_ABSTIME)
+				alarm_start(&ctx->t.alarm, texp);
+			else
+				alarm_start_relative(&ctx->t.alarm, texp);
+		} else {
+			hrtimer_start(&ctx->t.tmr, 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 unsigned int timerfd_poll(struct file *file, poll_table *wait)
+{
+	struct timerfd_ctx *ctx = file->private_data;
+	unsigned int events = 0;
+	unsigned long flags;
+
+	poll_wait(file, &ctx->wqh, wait);
+
+	spin_lock_irqsave(&ctx->wqh.lock, flags);
+	if (ctx->ticks)
+		events |= POLLIN;
+	spin_unlock_irqrestore(&ctx->wqh.lock, flags);
+
+	return events;
+}
+
+static ssize_t timerfd_read(struct file *file, char __user *buf, size_t count,
+			    loff_t *ppos)
+{
+	struct timerfd_ctx *ctx = file->private_data;
+	ssize_t res;
+	u64 ticks = 0;
+
+	if (count < sizeof(ticks))
+		return -EINVAL;
+	spin_lock_irq(&ctx->wqh.lock);
+	if (file->f_flags & O_NONBLOCK)
+		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) {
+		ticks = ctx->ticks;
+
+		if (ctx->expired && ctx->tintv.tv64) {
+			/*
+			 * If tintv.tv64 != 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 (isalarm(ctx)) {
+				ticks += alarm_forward_now(
+					&ctx->t.alarm, ctx->tintv) - 1;
+				alarm_restart(&ctx->t.alarm);
+			} else {
+				ticks += hrtimer_forward_now(&ctx->t.tmr,
+							     ctx->tintv) - 1;
+				hrtimer_restart(&ctx->t.tmr);
+			}
+		}
+		ctx->expired = 0;
+		ctx->ticks = 0;
+	}
+	spin_unlock_irq(&ctx->wqh.lock);
+	if (ticks)
+		res = put_user(ticks, (u64 __user *) buf) ? -EFAULT: sizeof(ticks);
+	return res;
+}
+
+#ifdef CONFIG_PROC_FS
+static void timerfd_show(struct seq_file *m, struct file *file)
+{
+	struct timerfd_ctx *ctx = file->private_data;
+	struct itimerspec t;
+
+	spin_lock_irq(&ctx->wqh.lock);
+	t.it_value = ktime_to_timespec(timerfd_get_remaining(ctx));
+	t.it_interval = ktime_to_timespec(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)t.it_value.tv_sec,
+		   (unsigned long long)t.it_value.tv_nsec,
+		   (unsigned long long)t.it_interval.tv_sec,
+		   (unsigned long long)t.it_interval.tv_nsec);
+}
+#else
+#define timerfd_show NULL
+#endif
+
+#ifdef CONFIG_CHECKPOINT_RESTORE
+static 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(&ctx->wqh);
+		} 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		= timerfd_read,
+	.llseek		= noop_llseek,
+	.show_fdinfo	= timerfd_show,
+	.unlocked_ioctl	= timerfd_ioctl,
+};
+
+static int timerfd_fget(int fd, struct fd *p)
+{
+	struct fd f = fdget(fd);
+	if (!f.file)
+		return -EBADF;
+	if (f.file->f_op != &timerfd_fops) {
+		fdput(f);
+		return -EINVAL;
+	}
+	*p = f;
+	return 0;
+}
+
+SYSCALL_DEFINE2(timerfd_create, int, clockid, int, flags)
+{
+	int ufd;
+	struct timerfd_ctx *ctx;
+
+	/* 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;
+
+	ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
+	if (!ctx)
+		return -ENOMEM;
+
+	init_waitqueue_head(&ctx->wqh);
+	ctx->clockid = clockid;
+
+	if (isalarm(ctx))
+		alarm_init(&ctx->t.alarm,
+			   ctx->clockid == CLOCK_REALTIME_ALARM ?
+			   ALARM_REALTIME : ALARM_BOOTTIME,
+			   timerfd_alarmproc);
+	else
+		hrtimer_init(&ctx->t.tmr, clockid, HRTIMER_MODE_ABS);
+
+	ctx->moffs = ktime_mono_to_real((ktime_t){ .tv64 = 0 });
+
+	ufd = anon_inode_getfd("[timerfd]", &timerfd_fops, ctx,
+			       O_RDWR | (flags & TFD_SHARED_FCNTL_FLAGS));
+	if (ufd < 0)
+		kfree(ctx);
+
+	return ufd;
+}
+
+static int do_timerfd_settime(int ufd, int flags, 
+		const struct itimerspec *new,
+		struct itimerspec *old)
+{
+	struct fd f;
+	struct timerfd_ctx *ctx;
+	int ret;
+
+	if ((flags & ~TFD_SETTIME_FLAGS) ||
+	    !timespec_valid(&new->it_value) ||
+	    !timespec_valid(&new->it_interval))
+		return -EINVAL;
+
+	ret = timerfd_fget(ufd, &f);
+	if (ret)
+		return ret;
+	ctx = f.file->private_data;
+
+	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);
+		cpu_relax();
+	}
+
+	/*
+	 * 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.tv64) {
+		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_timespec(timerfd_get_remaining(ctx));
+	old->it_interval = ktime_to_timespec(ctx->tintv);
+
+	/*
+	 * Re-program the timer to the new value ...
+	 */
+	ret = timerfd_setup(ctx, flags, new);
+
+	spin_unlock_irq(&ctx->wqh.lock);
+	fdput(f);
+	return ret;
+}
+
+static int do_timerfd_gettime(int ufd, struct itimerspec *t)
+{
+	struct fd f;
+	struct timerfd_ctx *ctx;
+	int ret = timerfd_fget(ufd, &f);
+	if (ret)
+		return ret;
+	ctx = f.file->private_data;
+
+	spin_lock_irq(&ctx->wqh.lock);
+	if (ctx->expired && ctx->tintv.tv64) {
+		ctx->expired = 0;
+
+		if (isalarm(ctx)) {
+			ctx->ticks +=
+				alarm_forward_now(
+					&ctx->t.alarm, ctx->tintv) - 1;
+			alarm_restart(&ctx->t.alarm);
+		} else {
+			ctx->ticks +=
+				hrtimer_forward_now(&ctx->t.tmr, ctx->tintv)
+				- 1;
+			hrtimer_restart(&ctx->t.tmr);
+		}
+	}
+	t->it_value = ktime_to_timespec(timerfd_get_remaining(ctx));
+	t->it_interval = ktime_to_timespec(ctx->tintv);
+	spin_unlock_irq(&ctx->wqh.lock);
+	fdput(f);
+	return 0;
+}
+
+SYSCALL_DEFINE4(timerfd_settime, int, ufd, int, flags,
+		const struct itimerspec __user *, utmr,
+		struct itimerspec __user *, otmr)
+{
+	struct itimerspec new, old;
+	int ret;
+
+	if (copy_from_user(&new, utmr, sizeof(new)))
+		return -EFAULT;
+	ret = do_timerfd_settime(ufd, flags, &new, &old);
+	if (ret)
+		return ret;
+	if (otmr && copy_to_user(otmr, &old, sizeof(old)))
+		return -EFAULT;
+
+	return ret;
+}
+
+SYSCALL_DEFINE2(timerfd_gettime, int, ufd, struct itimerspec __user *, otmr)
+{
+	struct itimerspec kotmr;
+	int ret = do_timerfd_gettime(ufd, &kotmr);
+	if (ret)
+		return ret;
+	return copy_to_user(otmr, &kotmr, sizeof(kotmr)) ? -EFAULT: 0;
+}
+
+#ifdef CONFIG_COMPAT
+COMPAT_SYSCALL_DEFINE4(timerfd_settime, int, ufd, int, flags,
+		const struct compat_itimerspec __user *, utmr,
+		struct compat_itimerspec __user *, otmr)
+{
+	struct itimerspec new, old;
+	int ret;
+
+	if (get_compat_itimerspec(&new, utmr))
+		return -EFAULT;
+	ret = do_timerfd_settime(ufd, flags, &new, &old);
+	if (ret)
+		return ret;
+	if (otmr && put_compat_itimerspec(otmr, &old))
+		return -EFAULT;
+	return ret;
+}
+
+COMPAT_SYSCALL_DEFINE2(timerfd_gettime, int, ufd,
+		struct compat_itimerspec __user *, otmr)
+{
+	struct itimerspec kotmr;
+	int ret = do_timerfd_gettime(ufd, &kotmr);
+	if (ret)
+		return ret;
+	return put_compat_itimerspec(otmr, &kotmr) ? -EFAULT: 0;
+}
+#endif