/******************************************************************************
   * 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 <xen/xen.h>
  #include <xen/events.h>
  #include <xen/evtchn.h>
  #include <asm/xen/hypervisor.h>
  
  struct per_user_data {
  	struct mutex bind_mutex; /* serialize bind/unbind operations */
  	struct rb_root evtchns;
  
  	/* Notification ring, accessed via /dev/xen/evtchn. */
  #define EVTCHN_RING_SIZE     (PAGE_SIZE / sizeof(evtchn_port_t))
  #define EVTCHN_RING_MASK(_i) ((_i)&(EVTCHN_RING_SIZE-1))
  	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;
  };
  
  struct user_evtchn {
  	struct rb_node node;
  	struct per_user_data *user;
  	unsigned port;
  	bool enabled;
  };
  
  static int add_evtchn(struct per_user_data *u, struct user_evtchn *evtchn)
  {
  	struct rb_node **new = &(u->evtchns.rb_node), *parent = NULL;
  
  	while (*new) {
  		struct user_evtchn *this;
  
  		this = container_of(*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)
  {
  	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 = container_of(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
  ",
  	     evtchn->port, u);
  
  	disable_irq_nosync(irq);
  	evtchn->enabled = false;
  
  	spin_lock(&u->ring_prod_lock);
  
  	if ((u->ring_prod - u->ring_cons) < EVTCHN_RING_SIZE) {
  		u->ring[EVTCHN_RING_MASK(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) & EVTCHN_RING_SIZE) != 0) {
  		bytes1 = (EVTCHN_RING_SIZE - EVTCHN_RING_MASK(c)) *
  			sizeof(evtchn_port_t);
  		bytes2 = EVTCHN_RING_MASK(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, &u->ring[EVTCHN_RING_MASK(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_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 = 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 = -EFAULT;
  		if (copy_from_user(&bind, uarg, sizeof(bind)))
  			break;
  
  		bind_virq.virq = bind.virq;
  		bind_virq.vcpu = 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;
  
  		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 = -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;
  	}
  
  	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);
  
  	u->ring = (evtchn_port_t *)__get_free_page(GFP_KERNEL);
  	if (u->ring == NULL) {
  		kfree(u->name);
  		kfree(u);
  		return -ENOMEM;
  	}
  
  	mutex_init(&u->bind_mutex);
  	mutex_init(&u->ring_cons_mutex);
  	spin_lock_init(&u->ring_prod_lock);
  
  	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);
  	}
  
  	free_page((unsigned long)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
  ");
  		return err;
  	}
  
  	pr_info("Event-channel device installed
  ");
  
  	return 0;
  }
  
  static void __exit evtchn_cleanup(void)
  {
  	misc_deregister(&evtchn_miscdev);
  }
  
  module_init(evtchn_init);
  module_exit(evtchn_cleanup);
  
  MODULE_LICENSE("GPL");