drivers/xen/evtchn.c - kernel/msm-5.4 - Gitiles

 /******************************************************************************
  * evtchn.c
  *
  * Driver for receiving and demuxing event-channel signals.
  *
  * Copyright (c) 2004-2005, K A Fraser
  * Multi-process extensions Copyright (c) 2004, Steven Smith
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License version 2
  * as published by the Free Software Foundation; or, when distributed
  * separately from the Linux kernel or incorporated into other
  * software packages, subject to the following license:
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this source file (the "Software"), to deal in the Software without
  * restriction, including without limitation the rights to use, copy, modify,
  * merge, publish, distribute, sublicense, and/or sell copies of the Software,
  * and to permit persons to whom the Software is furnished to do so, subject to
  * the following conditions:
  *
  * The above copyright notice and this permission notice shall be included in
  * all copies or substantial portions of the Software.
  *
  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
  * IN THE SOFTWARE.
  */

 #define pr_fmt(fmt) "xen:" KBUILD_MODNAME ": " fmt

 #include <linux/module.h>
 #include <linux/kernel.h>
 #include <linux/sched.h>
 #include <linux/slab.h>
 #include <linux/string.h>
 #include <linux/errno.h>
 #include <linux/fs.h>
 #include <linux/miscdevice.h>
 #include <linux/major.h>
 #include <linux/proc_fs.h>
 #include <linux/stat.h>
 #include <linux/poll.h>
 #include <linux/irq.h>
 #include <linux/init.h>
 #include <linux/mutex.h>
 #include <linux/cpu.h>
 #include <linux/mm.h>
 #include <linux/vmalloc.h>

 #include <xen/xen.h>
 #include <xen/events.h>
 #include <xen/evtchn.h>
 #include <xen/xen-ops.h>
 #include <asm/xen/hypervisor.h>

 struct per_user_data {
 	struct mutex bind_mutex; /* serialize bind/unbind operations */
 	struct rb_root evtchns;
 	unsigned int nr_evtchns;

 	/* Notification ring, accessed via /dev/xen/evtchn. */
 	unsigned int ring_size;
 	evtchn_port_t *ring;
 	unsigned int ring_cons, ring_prod, ring_overflow;
 	struct mutex ring_cons_mutex; /* protect against concurrent readers */
 	spinlock_t ring_prod_lock; /* product against concurrent interrupts */

 	/* Processes wait on this queue when ring is empty. */
 	wait_queue_head_t evtchn_wait;
 	struct fasync_struct *evtchn_async_queue;
 	const char *name;

 	domid_t restrict_domid;
 };

 #define UNRESTRICTED_DOMID ((domid_t)-1)

 struct user_evtchn {
 	struct rb_node node;
 	struct per_user_data *user;
 	unsigned port;
 	bool enabled;
 };

 static evtchn_port_t *evtchn_alloc_ring(unsigned int size)
 {
 	evtchn_port_t *ring;
 	size_t s = size * sizeof(*ring);

 	ring = kmalloc(s, GFP_KERNEL);
 	if (!ring)
 		ring = vmalloc(s);

 	return ring;
 }

 static void evtchn_free_ring(evtchn_port_t *ring)
 {
 	kvfree(ring);
 }

 static unsigned int evtchn_ring_offset(struct per_user_data *u,
 				       unsigned int idx)
 {
 	return idx & (u->ring_size - 1);
 }

 static evtchn_port_t *evtchn_ring_entry(struct per_user_data *u,
 					unsigned int idx)
 {
 	return u->ring + evtchn_ring_offset(u, idx);
 }

 static int add_evtchn(struct per_user_data *u, struct user_evtchn *evtchn)
 {
 	struct rb_node **new = &(u->evtchns.rb_node), *parent = NULL;

 	u->nr_evtchns++;

 	while (*new) {
 		struct user_evtchn *this;

 		this = rb_entry(*new, struct user_evtchn, node);

 		parent = *new;
 		if (this->port < evtchn->port)
 			new = &((*new)->rb_left);
 		else if (this->port > evtchn->port)
 			new = &((*new)->rb_right);
 		else
 			return -EEXIST;
 	}

 	/* Add new node and rebalance tree. */
 	rb_link_node(&evtchn->node, parent, new);
 	rb_insert_color(&evtchn->node, &u->evtchns);

 	return 0;
 }

 static void del_evtchn(struct per_user_data *u, struct user_evtchn *evtchn)
 {
 	u->nr_evtchns--;
 	rb_erase(&evtchn->node, &u->evtchns);
 	kfree(evtchn);
 }

 static struct user_evtchn *find_evtchn(struct per_user_data *u, unsigned port)
 {
 	struct rb_node *node = u->evtchns.rb_node;

 	while (node) {
 		struct user_evtchn *evtchn;

 		evtchn = rb_entry(node, struct user_evtchn, node);

 		if (evtchn->port < port)
 			node = node->rb_left;
 		else if (evtchn->port > port)
 			node = node->rb_right;
 		else
 			return evtchn;
 	}
 	return NULL;
 }

 static irqreturn_t evtchn_interrupt(int irq, void *data)
 {
 	struct user_evtchn *evtchn = data;
 	struct per_user_data *u = evtchn->user;

 	WARN(!evtchn->enabled,
 	     "Interrupt for port %d, but apparently not enabled; per-user %p\n",
 	     evtchn->port, u);

 	disable_irq_nosync(irq);
 	evtchn->enabled = false;

 	spin_lock(&u->ring_prod_lock);

 	if ((u->ring_prod - u->ring_cons) < u->ring_size) {
 		*evtchn_ring_entry(u, u->ring_prod) = evtchn->port;
 		wmb(); /* Ensure ring contents visible */
 		if (u->ring_cons == u->ring_prod++) {
 			wake_up_interruptible(&u->evtchn_wait);
 			kill_fasync(&u->evtchn_async_queue,
 				    SIGIO, POLL_IN);
 		}
 	} else
 		u->ring_overflow = 1;

 	spin_unlock(&u->ring_prod_lock);

 	return IRQ_HANDLED;
 }

 static ssize_t evtchn_read(struct file *file, char __user *buf,
 			   size_t count, loff_t *ppos)
 {
 	int rc;
 	unsigned int c, p, bytes1 = 0, bytes2 = 0;
 	struct per_user_data *u = file->private_data;

 	/* Whole number of ports. */
 	count &= ~(sizeof(evtchn_port_t)-1);

 	if (count == 0)
 		return 0;

 	if (count > PAGE_SIZE)
 		count = PAGE_SIZE;

 	for (;;) {
 		mutex_lock(&u->ring_cons_mutex);

 		rc = -EFBIG;
 		if (u->ring_overflow)
 			goto unlock_out;

 		c = u->ring_cons;
 		p = u->ring_prod;
 		if (c != p)
 			break;

 		mutex_unlock(&u->ring_cons_mutex);

 		if (file->f_flags & O_NONBLOCK)
 			return -EAGAIN;

 		rc = wait_event_interruptible(u->evtchn_wait,
 					      u->ring_cons != u->ring_prod);
 		if (rc)
 			return rc;
 	}

 	/* Byte lengths of two chunks. Chunk split (if any) is at ring wrap. */
 	if (((c ^ p) & u->ring_size) != 0) {
 		bytes1 = (u->ring_size - evtchn_ring_offset(u, c)) *
 			sizeof(evtchn_port_t);
 		bytes2 = evtchn_ring_offset(u, p) * sizeof(evtchn_port_t);
 	} else {
 		bytes1 = (p - c) * sizeof(evtchn_port_t);
 		bytes2 = 0;
 	}

 	/* Truncate chunks according to caller's maximum byte count. */
 	if (bytes1 > count) {
 		bytes1 = count;
 		bytes2 = 0;
 	} else if ((bytes1 + bytes2) > count) {
 		bytes2 = count - bytes1;
 	}

 	rc = -EFAULT;
 	rmb(); /* Ensure that we see the port before we copy it. */
 	if (copy_to_user(buf, evtchn_ring_entry(u, c), bytes1) ||
 	    ((bytes2 != 0) &&
 	     copy_to_user(&buf[bytes1], &u->ring[0], bytes2)))
 		goto unlock_out;

 	u->ring_cons += (bytes1 + bytes2) / sizeof(evtchn_port_t);
 	rc = bytes1 + bytes2;

  unlock_out:
 	mutex_unlock(&u->ring_cons_mutex);
 	return rc;
 }

 static ssize_t evtchn_write(struct file *file, const char __user *buf,
 			    size_t count, loff_t *ppos)
 {
 	int rc, i;
 	evtchn_port_t *kbuf = (evtchn_port_t *)__get_free_page(GFP_KERNEL);
 	struct per_user_data *u = file->private_data;

 	if (kbuf == NULL)
 		return -ENOMEM;

 	/* Whole number of ports. */
 	count &= ~(sizeof(evtchn_port_t)-1);

 	rc = 0;
 	if (count == 0)
 		goto out;

 	if (count > PAGE_SIZE)
 		count = PAGE_SIZE;

 	rc = -EFAULT;
 	if (copy_from_user(kbuf, buf, count) != 0)
 		goto out;

 	mutex_lock(&u->bind_mutex);

 	for (i = 0; i < (count/sizeof(evtchn_port_t)); i++) {
 		unsigned port = kbuf[i];
 		struct user_evtchn *evtchn;

 		evtchn = find_evtchn(u, port);
 		if (evtchn && !evtchn->enabled) {
 			evtchn->enabled = true;
 			enable_irq(irq_from_evtchn(port));
 		}
 	}

 	mutex_unlock(&u->bind_mutex);

 	rc = count;

  out:
 	free_page((unsigned long)kbuf);
 	return rc;
 }

 static int evtchn_resize_ring(struct per_user_data *u)
 {
 	unsigned int new_size;
 	evtchn_port_t *new_ring, *old_ring;

 	/*
 	 * Ensure the ring is large enough to capture all possible
 	 * events. i.e., one free slot for each bound event.
 	 */
 	if (u->nr_evtchns <= u->ring_size)
 		return 0;

 	if (u->ring_size == 0)
 		new_size = 64;
 	else
 		new_size = 2 * u->ring_size;

 	new_ring = evtchn_alloc_ring(new_size);
 	if (!new_ring)
 		return -ENOMEM;

 	old_ring = u->ring;

 	/*
 	 * Access to the ring contents is serialized by either the
 	 * prod /or/ cons lock so take both when resizing.
 	 */
 	mutex_lock(&u->ring_cons_mutex);
 	spin_lock_irq(&u->ring_prod_lock);

 	/*
 	 * Copy the old ring contents to the new ring.
 	 *
 	 * To take care of wrapping, a full ring, and the new index
 	 * pointing into the second half, simply copy the old contents
 	 * twice.
 	 *
 	 * +---------+    +------------------+
 	 * |34567  12| -> |34567  1234567  12|
 	 * +-----p-c-+    +-------c------p---+
 	 */
 	memcpy(new_ring, old_ring, u->ring_size * sizeof(*u->ring));
 	memcpy(new_ring + u->ring_size, old_ring,
 	       u->ring_size * sizeof(*u->ring));

 	u->ring = new_ring;
 	u->ring_size = new_size;

 	spin_unlock_irq(&u->ring_prod_lock);
 	mutex_unlock(&u->ring_cons_mutex);

 	evtchn_free_ring(old_ring);

 	return 0;
 }

 static int evtchn_bind_to_user(struct per_user_data *u, int port)
 {
 	struct user_evtchn *evtchn;
 	struct evtchn_close close;
 	int rc = 0;

 	/*
 	 * Ports are never reused, so every caller should pass in a
 	 * unique port.
 	 *
 	 * (Locking not necessary because we haven't registered the
 	 * interrupt handler yet, and our caller has already
 	 * serialized bind operations.)
 	 */

 	evtchn = kzalloc(sizeof(*evtchn), GFP_KERNEL);
 	if (!evtchn)
 		return -ENOMEM;

 	evtchn->user = u;
 	evtchn->port = port;
 	evtchn->enabled = true; /* start enabled */

 	rc = add_evtchn(u, evtchn);
 	if (rc < 0)
 		goto err;

 	rc = evtchn_resize_ring(u);
 	if (rc < 0)
 		goto err;

 	rc = bind_evtchn_to_irqhandler(port, evtchn_interrupt, 0,
 				       u->name, evtchn);
 	if (rc < 0)
 		goto err;

 	rc = evtchn_make_refcounted(port);
 	return rc;

 err:
 	/* bind failed, should close the port now */
 	close.port = port;
 	if (HYPERVISOR_event_channel_op(EVTCHNOP_close, &close) != 0)
 		BUG();
 	del_evtchn(u, evtchn);
 	return rc;
 }

 static void evtchn_unbind_from_user(struct per_user_data *u,
 				    struct user_evtchn *evtchn)
 {
 	int irq = irq_from_evtchn(evtchn->port);

 	BUG_ON(irq < 0);

 	unbind_from_irqhandler(irq, evtchn);

 	del_evtchn(u, evtchn);
 }

 static long evtchn_ioctl(struct file *file,
 			 unsigned int cmd, unsigned long arg)
 {
 	int rc;
 	struct per_user_data *u = file->private_data;
 	void __user *uarg = (void __user *) arg;

 	/* Prevent bind from racing with unbind */
 	mutex_lock(&u->bind_mutex);

 	switch (cmd) {
 	case IOCTL_EVTCHN_BIND_VIRQ: {
 		struct ioctl_evtchn_bind_virq bind;
 		struct evtchn_bind_virq bind_virq;

 		rc = -EACCES;
 		if (u->restrict_domid != UNRESTRICTED_DOMID)
 			break;

 		rc = -EFAULT;
 		if (copy_from_user(&bind, uarg, sizeof(bind)))
 			break;

 		bind_virq.virq = bind.virq;
 		bind_virq.vcpu = xen_vcpu_nr(0);
 		rc = HYPERVISOR_event_channel_op(EVTCHNOP_bind_virq,
 						 &bind_virq);
 		if (rc != 0)
 			break;

 		rc = evtchn_bind_to_user(u, bind_virq.port);
 		if (rc == 0)
 			rc = bind_virq.port;
 		break;
 	}

 	case IOCTL_EVTCHN_BIND_INTERDOMAIN: {
 		struct ioctl_evtchn_bind_interdomain bind;
 		struct evtchn_bind_interdomain bind_interdomain;

 		rc = -EFAULT;
 		if (copy_from_user(&bind, uarg, sizeof(bind)))
 			break;

 		rc = -EACCES;
 		if (u->restrict_domid != UNRESTRICTED_DOMID &&
 		    u->restrict_domid != bind.remote_domain)
 			break;

 		bind_interdomain.remote_dom  = bind.remote_domain;
 		bind_interdomain.remote_port = bind.remote_port;
 		rc = HYPERVISOR_event_channel_op(EVTCHNOP_bind_interdomain,
 						 &bind_interdomain);
 		if (rc != 0)
 			break;

 		rc = evtchn_bind_to_user(u, bind_interdomain.local_port);
 		if (rc == 0)
 			rc = bind_interdomain.local_port;
 		break;
 	}

 	case IOCTL_EVTCHN_BIND_UNBOUND_PORT: {
 		struct ioctl_evtchn_bind_unbound_port bind;
 		struct evtchn_alloc_unbound alloc_unbound;

 		rc = -EACCES;
 		if (u->restrict_domid != UNRESTRICTED_DOMID)
 			break;

 		rc = -EFAULT;
 		if (copy_from_user(&bind, uarg, sizeof(bind)))
 			break;

 		alloc_unbound.dom        = DOMID_SELF;
 		alloc_unbound.remote_dom = bind.remote_domain;
 		rc = HYPERVISOR_event_channel_op(EVTCHNOP_alloc_unbound,
 						 &alloc_unbound);
 		if (rc != 0)
 			break;

 		rc = evtchn_bind_to_user(u, alloc_unbound.port);
 		if (rc == 0)
 			rc = alloc_unbound.port;
 		break;
 	}

 	case IOCTL_EVTCHN_UNBIND: {
 		struct ioctl_evtchn_unbind unbind;
 		struct user_evtchn *evtchn;

 		rc = -EFAULT;
 		if (copy_from_user(&unbind, uarg, sizeof(unbind)))
 			break;

 		rc = -EINVAL;
 		if (unbind.port >= xen_evtchn_nr_channels())
 			break;

 		rc = -ENOTCONN;
 		evtchn = find_evtchn(u, unbind.port);
 		if (!evtchn)
 			break;

 		disable_irq(irq_from_evtchn(unbind.port));
 		evtchn_unbind_from_user(u, evtchn);
 		rc = 0;
 		break;
 	}

 	case IOCTL_EVTCHN_NOTIFY: {
 		struct ioctl_evtchn_notify notify;
 		struct user_evtchn *evtchn;

 		rc = -EFAULT;
 		if (copy_from_user(&notify, uarg, sizeof(notify)))
 			break;

 		rc = -ENOTCONN;
 		evtchn = find_evtchn(u, notify.port);
 		if (evtchn) {
 			notify_remote_via_evtchn(notify.port);
 			rc = 0;
 		}
 		break;
 	}

 	case IOCTL_EVTCHN_RESET: {
 		/* Initialise the ring to empty. Clear errors. */
 		mutex_lock(&u->ring_cons_mutex);
 		spin_lock_irq(&u->ring_prod_lock);
 		u->ring_cons = u->ring_prod = u->ring_overflow = 0;
 		spin_unlock_irq(&u->ring_prod_lock);
 		mutex_unlock(&u->ring_cons_mutex);
 		rc = 0;
 		break;
 	}

 	case IOCTL_EVTCHN_RESTRICT_DOMID: {
 		struct ioctl_evtchn_restrict_domid ierd;

 		rc = -EACCES;
 		if (u->restrict_domid != UNRESTRICTED_DOMID)
 			break;

 		rc = -EFAULT;
 		if (copy_from_user(&ierd, uarg, sizeof(ierd)))
 		    break;

 		rc = -EINVAL;
 		if (ierd.domid == 0 || ierd.domid >= DOMID_FIRST_RESERVED)
 			break;

 		u->restrict_domid = ierd.domid;
 		rc = 0;

 		break;
 	}

 	default:
 		rc = -ENOSYS;
 		break;
 	}
 	mutex_unlock(&u->bind_mutex);

 	return rc;
 }

 static unsigned int evtchn_poll(struct file *file, poll_table *wait)
 {
 	unsigned int mask = POLLOUT | POLLWRNORM;
 	struct per_user_data *u = file->private_data;

 	poll_wait(file, &u->evtchn_wait, wait);
 	if (u->ring_cons != u->ring_prod)
 		mask |= POLLIN | POLLRDNORM;
 	if (u->ring_overflow)
 		mask = POLLERR;
 	return mask;
 }

 static int evtchn_fasync(int fd, struct file *filp, int on)
 {
 	struct per_user_data *u = filp->private_data;
 	return fasync_helper(fd, filp, on, &u->evtchn_async_queue);
 }

 static int evtchn_open(struct inode *inode, struct file *filp)
 {
 	struct per_user_data *u;

 	u = kzalloc(sizeof(*u), GFP_KERNEL);
 	if (u == NULL)
 		return -ENOMEM;

 	u->name = kasprintf(GFP_KERNEL, "evtchn:%s", current->comm);
 	if (u->name == NULL) {
 		kfree(u);
 		return -ENOMEM;
 	}

 	init_waitqueue_head(&u->evtchn_wait);

 	mutex_init(&u->bind_mutex);
 	mutex_init(&u->ring_cons_mutex);
 	spin_lock_init(&u->ring_prod_lock);

 	u->restrict_domid = UNRESTRICTED_DOMID;

 	filp->private_data = u;

 	return nonseekable_open(inode, filp);
 }

 static int evtchn_release(struct inode *inode, struct file *filp)
 {
 	struct per_user_data *u = filp->private_data;
 	struct rb_node *node;

 	while ((node = u->evtchns.rb_node)) {
 		struct user_evtchn *evtchn;

 		evtchn = rb_entry(node, struct user_evtchn, node);
 		disable_irq(irq_from_evtchn(evtchn->port));
 		evtchn_unbind_from_user(u, evtchn);
 	}

 	evtchn_free_ring(u->ring);
 	kfree(u->name);
 	kfree(u);

 	return 0;
 }

 static const struct file_operations evtchn_fops = {
 	.owner   = THIS_MODULE,
 	.read    = evtchn_read,
 	.write   = evtchn_write,
 	.unlocked_ioctl = evtchn_ioctl,
 	.poll    = evtchn_poll,
 	.fasync  = evtchn_fasync,
 	.open    = evtchn_open,
 	.release = evtchn_release,
 	.llseek	 = no_llseek,
 };

 static struct miscdevice evtchn_miscdev = {
 	.minor        = MISC_DYNAMIC_MINOR,
 	.name         = "xen/evtchn",
 	.fops         = &evtchn_fops,
 };
 static int __init evtchn_init(void)
 {
 	int err;

 	if (!xen_domain())
 		return -ENODEV;

 	/* Create '/dev/xen/evtchn'. */
 	err = misc_register(&evtchn_miscdev);
 	if (err != 0) {
 		pr_err("Could not register /dev/xen/evtchn\n");
 		return err;
 	}

 	pr_info("Event-channel device installed\n");

 	return 0;
 }

 static void __exit evtchn_cleanup(void)
 {
 	misc_deregister(&evtchn_miscdev);
 }

 module_init(evtchn_init);
 module_exit(evtchn_cleanup);

 MODULE_LICENSE("GPL");
	/******************************************************************************
	* evtchn.c
	*
	* Driver for receiving and demuxing event-channel signals.
	*
	* Copyright (c) 2004-2005, K A Fraser
	* Multi-process extensions Copyright (c) 2004, Steven Smith
	*
	* This program is free software; you can redistribute it and/or
	* modify it under the terms of the GNU General Public License version 2
	* as published by the Free Software Foundation; or, when distributed
	* separately from the Linux kernel or incorporated into other
	* software packages, subject to the following license:
	*
	* Permission is hereby granted, free of charge, to any person obtaining a copy
	* of this source file (the "Software"), to deal in the Software without
	* restriction, including without limitation the rights to use, copy, modify,
	* merge, publish, distribute, sublicense, and/or sell copies of the Software,
	* and to permit persons to whom the Software is furnished to do so, subject to
	* the following conditions:
	*
	* The above copyright notice and this permission notice shall be included in
	* all copies or substantial portions of the Software.
	*
	* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
	* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
	* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
	* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
	* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
	* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
	* IN THE SOFTWARE.
	*/

	#define pr_fmt(fmt) "xen:" KBUILD_MODNAME ": " fmt

	#include <linux/module.h>
	#include <linux/kernel.h>
	#include <linux/sched.h>
	#include <linux/slab.h>
	#include <linux/string.h>
	#include <linux/errno.h>
	#include <linux/fs.h>
	#include <linux/miscdevice.h>
	#include <linux/major.h>
	#include <linux/proc_fs.h>
	#include <linux/stat.h>
	#include <linux/poll.h>
	#include <linux/irq.h>
	#include <linux/init.h>
	#include <linux/mutex.h>
	#include <linux/cpu.h>
	#include <linux/mm.h>
	#include <linux/vmalloc.h>

	#include <xen/xen.h>
	#include <xen/events.h>
	#include <xen/evtchn.h>
	#include <xen/xen-ops.h>
	#include <asm/xen/hypervisor.h>

	struct per_user_data {
	struct mutex bind_mutex; /* serialize bind/unbind operations */
	struct rb_root evtchns;
	unsigned int nr_evtchns;

	/* Notification ring, accessed via /dev/xen/evtchn. */
	unsigned int ring_size;
	evtchn_port_t *ring;
	unsigned int ring_cons, ring_prod, ring_overflow;
	struct mutex ring_cons_mutex; /* protect against concurrent readers */
	spinlock_t ring_prod_lock; /* product against concurrent interrupts */

	/* Processes wait on this queue when ring is empty. */
	wait_queue_head_t evtchn_wait;
	struct fasync_struct *evtchn_async_queue;
	const char *name;

	domid_t restrict_domid;
	};

	#define UNRESTRICTED_DOMID ((domid_t)-1)

	struct user_evtchn {
	struct rb_node node;
	struct per_user_data *user;
	unsigned port;
	bool enabled;
	};

	static evtchn_port_t *evtchn_alloc_ring(unsigned int size)
	{
	evtchn_port_t *ring;
	size_t s = size * sizeof(*ring);

	ring = kmalloc(s, GFP_KERNEL);
	if (!ring)
	ring = vmalloc(s);

	return ring;
	}

	static void evtchn_free_ring(evtchn_port_t *ring)
	{
	kvfree(ring);
	}

	static unsigned int evtchn_ring_offset(struct per_user_data *u,
	unsigned int idx)
	{
	return idx & (u->ring_size - 1);
	}

	static evtchn_port_t evtchn_ring_entry(struct per_user_data u,
	unsigned int idx)
	{
	return u->ring + evtchn_ring_offset(u, idx);
	}

	static int add_evtchn(struct per_user_data u, struct user_evtchn evtchn)
	{
	struct rb_node *new = &(u->evtchns.rb_node), parent = NULL;

	u->nr_evtchns++;

	while (*new) {
	struct user_evtchn *this;

	this = rb_entry(*new, struct user_evtchn, node);

	parent = *new;
	if (this->port < evtchn->port)
	new = &((*new)->rb_left);
	else if (this->port > evtchn->port)
	new = &((*new)->rb_right);
	else
	return -EEXIST;
	}

	/* Add new node and rebalance tree. */
	rb_link_node(&evtchn->node, parent, new);
	rb_insert_color(&evtchn->node, &u->evtchns);

	return 0;
	}

	static void del_evtchn(struct per_user_data u, struct user_evtchn evtchn)
	{
	u->nr_evtchns--;
	rb_erase(&evtchn->node, &u->evtchns);
	kfree(evtchn);
	}

	static struct user_evtchn find_evtchn(struct per_user_data u, unsigned port)
	{
	struct rb_node *node = u->evtchns.rb_node;

	while (node) {
	struct user_evtchn *evtchn;

	evtchn = rb_entry(node, struct user_evtchn, node);

	if (evtchn->port < port)
	node = node->rb_left;
	else if (evtchn->port > port)
	node = node->rb_right;
	else
	return evtchn;
	}
	return NULL;
	}

	static irqreturn_t evtchn_interrupt(int irq, void *data)
	{
	struct user_evtchn *evtchn = data;
	struct per_user_data *u = evtchn->user;

	WARN(!evtchn->enabled,
	"Interrupt for port %d, but apparently not enabled; per-user %p\n",
	evtchn->port, u);

	disable_irq_nosync(irq);
	evtchn->enabled = false;

	spin_lock(&u->ring_prod_lock);

	if ((u->ring_prod - u->ring_cons) < u->ring_size) {
	*evtchn_ring_entry(u, u->ring_prod) = evtchn->port;
	wmb(); /* Ensure ring contents visible */
	if (u->ring_cons == u->ring_prod++) {
	wake_up_interruptible(&u->evtchn_wait);
	kill_fasync(&u->evtchn_async_queue,
	SIGIO, POLL_IN);
	}
	} else
	u->ring_overflow = 1;

	spin_unlock(&u->ring_prod_lock);

	return IRQ_HANDLED;
	}

	static ssize_t evtchn_read(struct file file, char __user buf,
	size_t count, loff_t *ppos)
	{
	int rc;
	unsigned int c, p, bytes1 = 0, bytes2 = 0;
	struct per_user_data *u = file->private_data;

	/* Whole number of ports. */
	count &= ~(sizeof(evtchn_port_t)-1);

	if (count == 0)
	return 0;

	if (count > PAGE_SIZE)
	count = PAGE_SIZE;

	for (;;) {
	mutex_lock(&u->ring_cons_mutex);

	rc = -EFBIG;
	if (u->ring_overflow)
	goto unlock_out;

	c = u->ring_cons;
	p = u->ring_prod;
	if (c != p)
	break;

	mutex_unlock(&u->ring_cons_mutex);

	if (file->f_flags & O_NONBLOCK)
	return -EAGAIN;

	rc = wait_event_interruptible(u->evtchn_wait,
	u->ring_cons != u->ring_prod);
	if (rc)
	return rc;
	}

	/* Byte lengths of two chunks. Chunk split (if any) is at ring wrap. */
	if (((c ^ p) & u->ring_size) != 0) {
	bytes1 = (u->ring_size - evtchn_ring_offset(u, c)) *
	sizeof(evtchn_port_t);
	bytes2 = evtchn_ring_offset(u, p) * sizeof(evtchn_port_t);
	} else {
	bytes1 = (p - c) * sizeof(evtchn_port_t);
	bytes2 = 0;
	}

	/* Truncate chunks according to caller's maximum byte count. */
	if (bytes1 > count) {
	bytes1 = count;
	bytes2 = 0;
	} else if ((bytes1 + bytes2) > count) {
	bytes2 = count - bytes1;
	}

	rc = -EFAULT;
	rmb(); /* Ensure that we see the port before we copy it. */
	if (copy_to_user(buf, evtchn_ring_entry(u, c), bytes1) \|\|
	((bytes2 != 0) &&
	copy_to_user(&buf[bytes1], &u->ring[0], bytes2)))
	goto unlock_out;

	u->ring_cons += (bytes1 + bytes2) / sizeof(evtchn_port_t);
	rc = bytes1 + bytes2;

	unlock_out:
	mutex_unlock(&u->ring_cons_mutex);
	return rc;
	}

	static ssize_t evtchn_write(struct file file, const char __user buf,
	size_t count, loff_t *ppos)
	{
	int rc, i;
	evtchn_port_t kbuf = (evtchn_port_t )__get_free_page(GFP_KERNEL);
	struct per_user_data *u = file->private_data;

	if (kbuf == NULL)
	return -ENOMEM;

	/* Whole number of ports. */
	count &= ~(sizeof(evtchn_port_t)-1);

	rc = 0;
	if (count == 0)
	goto out;

	if (count > PAGE_SIZE)
	count = PAGE_SIZE;

	rc = -EFAULT;
	if (copy_from_user(kbuf, buf, count) != 0)
	goto out;

	mutex_lock(&u->bind_mutex);

	for (i = 0; i < (count/sizeof(evtchn_port_t)); i++) {
	unsigned port = kbuf[i];
	struct user_evtchn *evtchn;

	evtchn = find_evtchn(u, port);
	if (evtchn && !evtchn->enabled) {
	evtchn->enabled = true;
	enable_irq(irq_from_evtchn(port));
	}
	}

	mutex_unlock(&u->bind_mutex);

	rc = count;

	out:
	free_page((unsigned long)kbuf);
	return rc;
	}

	static int evtchn_resize_ring(struct per_user_data *u)
	{
	unsigned int new_size;
	evtchn_port_t new_ring, old_ring;

	/*
	* Ensure the ring is large enough to capture all possible
	* events. i.e., one free slot for each bound event.
	*/
	if (u->nr_evtchns <= u->ring_size)
	return 0;

	if (u->ring_size == 0)
	new_size = 64;
	else
	new_size = 2 * u->ring_size;

	new_ring = evtchn_alloc_ring(new_size);
	if (!new_ring)
	return -ENOMEM;

	old_ring = u->ring;

	/*
	* Access to the ring contents is serialized by either the
	* prod /or/ cons lock so take both when resizing.
	*/
	mutex_lock(&u->ring_cons_mutex);
	spin_lock_irq(&u->ring_prod_lock);

	/*
	* Copy the old ring contents to the new ring.
	*
	* To take care of wrapping, a full ring, and the new index
	* pointing into the second half, simply copy the old contents
	* twice.
	*
	* +---------+ +------------------+
	* \|34567 12\| -> \|34567 1234567 12\|
	* +-----p-c-+ +-------c------p---+
	*/
	memcpy(new_ring, old_ring, u->ring_size * sizeof(*u->ring));
	memcpy(new_ring + u->ring_size, old_ring,
	u->ring_size * sizeof(*u->ring));

	u->ring = new_ring;
	u->ring_size = new_size;

	spin_unlock_irq(&u->ring_prod_lock);
	mutex_unlock(&u->ring_cons_mutex);

	evtchn_free_ring(old_ring);

	return 0;
	}

	static int evtchn_bind_to_user(struct per_user_data *u, int port)
	{
	struct user_evtchn *evtchn;
	struct evtchn_close close;
	int rc = 0;

	/*
	* Ports are never reused, so every caller should pass in a
	* unique port.
	*
	* (Locking not necessary because we haven't registered the
	* interrupt handler yet, and our caller has already
	* serialized bind operations.)
	*/

	evtchn = kzalloc(sizeof(*evtchn), GFP_KERNEL);
	if (!evtchn)
	return -ENOMEM;

	evtchn->user = u;
	evtchn->port = port;
	evtchn->enabled = true; /* start enabled */

	rc = add_evtchn(u, evtchn);
	if (rc < 0)
	goto err;

	rc = evtchn_resize_ring(u);
	if (rc < 0)
	goto err;

	rc = bind_evtchn_to_irqhandler(port, evtchn_interrupt, 0,
	u->name, evtchn);
	if (rc < 0)
	goto err;

	rc = evtchn_make_refcounted(port);
	return rc;

	err:
	/* bind failed, should close the port now */
	close.port = port;
	if (HYPERVISOR_event_channel_op(EVTCHNOP_close, &close) != 0)
	BUG();
	del_evtchn(u, evtchn);
	return rc;
	}

	static void evtchn_unbind_from_user(struct per_user_data *u,
	struct user_evtchn *evtchn)
	{
	int irq = irq_from_evtchn(evtchn->port);

	BUG_ON(irq < 0);

	unbind_from_irqhandler(irq, evtchn);

	del_evtchn(u, evtchn);
	}

	static long evtchn_ioctl(struct file *file,
	unsigned int cmd, unsigned long arg)
	{
	int rc;
	struct per_user_data *u = file->private_data;
	void __user uarg = (void __user ) arg;

	/* Prevent bind from racing with unbind */
	mutex_lock(&u->bind_mutex);

	switch (cmd) {
	case IOCTL_EVTCHN_BIND_VIRQ: {
	struct ioctl_evtchn_bind_virq bind;
	struct evtchn_bind_virq bind_virq;

	rc = -EACCES;
	if (u->restrict_domid != UNRESTRICTED_DOMID)
	break;

	rc = -EFAULT;
	if (copy_from_user(&bind, uarg, sizeof(bind)))
	break;

	bind_virq.virq = bind.virq;
	bind_virq.vcpu = xen_vcpu_nr(0);
	rc = HYPERVISOR_event_channel_op(EVTCHNOP_bind_virq,
	&bind_virq);
	if (rc != 0)
	break;

	rc = evtchn_bind_to_user(u, bind_virq.port);
	if (rc == 0)
	rc = bind_virq.port;
	break;
	}

	case IOCTL_EVTCHN_BIND_INTERDOMAIN: {
	struct ioctl_evtchn_bind_interdomain bind;
	struct evtchn_bind_interdomain bind_interdomain;

	rc = -EFAULT;
	if (copy_from_user(&bind, uarg, sizeof(bind)))
	break;

	rc = -EACCES;
	if (u->restrict_domid != UNRESTRICTED_DOMID &&
	u->restrict_domid != bind.remote_domain)
	break;

	bind_interdomain.remote_dom = bind.remote_domain;
	bind_interdomain.remote_port = bind.remote_port;
	rc = HYPERVISOR_event_channel_op(EVTCHNOP_bind_interdomain,
	&bind_interdomain);
	if (rc != 0)
	break;

	rc = evtchn_bind_to_user(u, bind_interdomain.local_port);
	if (rc == 0)
	rc = bind_interdomain.local_port;
	break;
	}

	case IOCTL_EVTCHN_BIND_UNBOUND_PORT: {
	struct ioctl_evtchn_bind_unbound_port bind;
	struct evtchn_alloc_unbound alloc_unbound;

	rc = -EACCES;
	if (u->restrict_domid != UNRESTRICTED_DOMID)
	break;

	rc = -EFAULT;
	if (copy_from_user(&bind, uarg, sizeof(bind)))
	break;

	alloc_unbound.dom = DOMID_SELF;
	alloc_unbound.remote_dom = bind.remote_domain;
	rc = HYPERVISOR_event_channel_op(EVTCHNOP_alloc_unbound,
	&alloc_unbound);
	if (rc != 0)
	break;

	rc = evtchn_bind_to_user(u, alloc_unbound.port);
	if (rc == 0)
	rc = alloc_unbound.port;
	break;
	}

	case IOCTL_EVTCHN_UNBIND: {
	struct ioctl_evtchn_unbind unbind;
	struct user_evtchn *evtchn;

	rc = -EFAULT;
	if (copy_from_user(&unbind, uarg, sizeof(unbind)))
	break;

	rc = -EINVAL;
	if (unbind.port >= xen_evtchn_nr_channels())
	break;

	rc = -ENOTCONN;
	evtchn = find_evtchn(u, unbind.port);
	if (!evtchn)
	break;

	disable_irq(irq_from_evtchn(unbind.port));
	evtchn_unbind_from_user(u, evtchn);
	rc = 0;
	break;
	}

	case IOCTL_EVTCHN_NOTIFY: {
	struct ioctl_evtchn_notify notify;
	struct user_evtchn *evtchn;

	rc = -EFAULT;
	if (copy_from_user(&notify, uarg, sizeof(notify)))
	break;

	rc = -ENOTCONN;
	evtchn = find_evtchn(u, notify.port);
	if (evtchn) {
	notify_remote_via_evtchn(notify.port);
	rc = 0;
	}
	break;
	}

	case IOCTL_EVTCHN_RESET: {
	/* Initialise the ring to empty. Clear errors. */
	mutex_lock(&u->ring_cons_mutex);
	spin_lock_irq(&u->ring_prod_lock);
	u->ring_cons = u->ring_prod = u->ring_overflow = 0;
	spin_unlock_irq(&u->ring_prod_lock);
	mutex_unlock(&u->ring_cons_mutex);
	rc = 0;
	break;
	}

	case IOCTL_EVTCHN_RESTRICT_DOMID: {
	struct ioctl_evtchn_restrict_domid ierd;

	rc = -EACCES;
	if (u->restrict_domid != UNRESTRICTED_DOMID)
	break;

	rc = -EFAULT;
	if (copy_from_user(&ierd, uarg, sizeof(ierd)))
	break;

	rc = -EINVAL;
	if (ierd.domid == 0 \|\| ierd.domid >= DOMID_FIRST_RESERVED)
	break;

	u->restrict_domid = ierd.domid;
	rc = 0;

	break;
	}

	default:
	rc = -ENOSYS;
	break;
	}
	mutex_unlock(&u->bind_mutex);

	return rc;
	}

	static unsigned int evtchn_poll(struct file file, poll_table wait)
	{
	unsigned int mask = POLLOUT \| POLLWRNORM;
	struct per_user_data *u = file->private_data;

	poll_wait(file, &u->evtchn_wait, wait);
	if (u->ring_cons != u->ring_prod)
	mask \|= POLLIN \| POLLRDNORM;
	if (u->ring_overflow)
	mask = POLLERR;
	return mask;
	}

	static int evtchn_fasync(int fd, struct file *filp, int on)
	{
	struct per_user_data *u = filp->private_data;
	return fasync_helper(fd, filp, on, &u->evtchn_async_queue);
	}

	static int evtchn_open(struct inode inode, struct file filp)
	{
	struct per_user_data *u;

	u = kzalloc(sizeof(*u), GFP_KERNEL);
	if (u == NULL)
	return -ENOMEM;

	u->name = kasprintf(GFP_KERNEL, "evtchn:%s", current->comm);
	if (u->name == NULL) {
	kfree(u);
	return -ENOMEM;
	}

	init_waitqueue_head(&u->evtchn_wait);

	mutex_init(&u->bind_mutex);
	mutex_init(&u->ring_cons_mutex);
	spin_lock_init(&u->ring_prod_lock);

	u->restrict_domid = UNRESTRICTED_DOMID;

	filp->private_data = u;

	return nonseekable_open(inode, filp);
	}

	static int evtchn_release(struct inode inode, struct file filp)
	{
	struct per_user_data *u = filp->private_data;
	struct rb_node *node;

	while ((node = u->evtchns.rb_node)) {
	struct user_evtchn *evtchn;

	evtchn = rb_entry(node, struct user_evtchn, node);
	disable_irq(irq_from_evtchn(evtchn->port));
	evtchn_unbind_from_user(u, evtchn);
	}

	evtchn_free_ring(u->ring);
	kfree(u->name);
	kfree(u);

	return 0;
	}

	static const struct file_operations evtchn_fops = {
	.owner = THIS_MODULE,
	.read = evtchn_read,
	.write = evtchn_write,
	.unlocked_ioctl = evtchn_ioctl,
	.poll = evtchn_poll,
	.fasync = evtchn_fasync,
	.open = evtchn_open,
	.release = evtchn_release,
	.llseek = no_llseek,
	};

	static struct miscdevice evtchn_miscdev = {
	.minor = MISC_DYNAMIC_MINOR,
	.name = "xen/evtchn",
	.fops = &evtchn_fops,
	};
	static int __init evtchn_init(void)
	{
	int err;

	if (!xen_domain())
	return -ENODEV;

	/* Create '/dev/xen/evtchn'. */
	err = misc_register(&evtchn_miscdev);
	if (err != 0) {
	pr_err("Could not register /dev/xen/evtchn\n");
	return err;
	}

	pr_info("Event-channel device installed\n");

	return 0;
	}

	static void __exit evtchn_cleanup(void)
	{
	misc_deregister(&evtchn_miscdev);
	}

	module_init(evtchn_init);
	module_exit(evtchn_cleanup);

	MODULE_LICENSE("GPL");