/******************************************************************************
 * 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.
 */

#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/gfp.h>
#include <linux/mutex.h>
#include <linux/cpu.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 */

        /* 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 */

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

/* Who's bound to each port? */
static struct per_user_data *port_user[NR_EVENT_CHANNELS];
static DEFINE_SPINLOCK(port_user_lock); /* protects port_user[] and ring_prod */

irqreturn_t evtchn_interrupt(int irq, void *data)
{
        unsigned int port = (unsigned long)data;
        struct per_user_data *u;

        spin_lock(&port_user_lock);

        u = port_user[port];

        disable_irq_nosync(irq);

        if ((u->ring_prod - u->ring_cons) < EVTCHN_RING_SIZE) {
                u->ring[EVTCHN_RING_MASK(u->ring_prod)] = 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(&port_user_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;

        spin_lock_irq(&port_user_lock);
        for (i = 0; i < (count/sizeof(evtchn_port_t)); i++)
                if ((kbuf[i] < NR_EVENT_CHANNELS) && (port_user[kbuf[i]] == u))
                        enable_irq(irq_from_evtchn(kbuf[i]));
        spin_unlock_irq(&port_user_lock);

        rc = count;

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

static int evtchn_bind_to_user(struct per_user_data *u, int port)
{
        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.)
         */
        BUG_ON(port_user[port] != NULL);
        port_user[port] = u;

        rc = bind_evtchn_to_irqhandler(port, evtchn_interrupt, IRQF_DISABLED,
                                       u->name, (void *)(unsigned long)port);
        if (rc >= 0)
                rc = 0;

        return rc;
}

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

        unbind_from_irqhandler(irq, (void *)(unsigned long)port);

        /* make sure we unbind the irq handler before clearing the port */
        barrier();

        port_user[port] = NULL;
}

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;

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

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

                spin_lock_irq(&port_user_lock);

                rc = -ENOTCONN;
                if (port_user[unbind.port] != u) {
                        spin_unlock_irq(&port_user_lock);
                        break;
                }

                evtchn_unbind_from_user(u, unbind.port);

                spin_unlock_irq(&port_user_lock);

                rc = 0;
                break;
        }

        case IOCTL_EVTCHN_NOTIFY: {
                struct ioctl_evtchn_notify notify;

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

                if (notify.port >= NR_EVENT_CHANNELS) {
                        rc = -EINVAL;
                } else if (port_user[notify.port] != u) {
                        rc = -ENOTCONN;
                } else {
                        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(&port_user_lock);
                u->ring_cons = u->ring_prod = u->ring_overflow = 0;
                spin_unlock_irq(&port_user_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);

        filp->private_data = u;

        return 0;
}

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

        spin_lock_irq(&port_user_lock);

        free_page((unsigned long)u->ring);

        for (i = 0; i < NR_EVENT_CHANNELS; i++) {
                if (port_user[i] != u)
                        continue;

                evtchn_unbind_from_user(port_user[i], i);
        }

        spin_unlock_irq(&port_user_lock);

        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,
};

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

        if (!xen_domain())
                return -ENODEV;

        spin_lock_init(&port_user_lock);
        memset(port_user, 0, sizeof(port_user));

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

        printk(KERN_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");