/******************************************************************************
 * 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
 * FreeBSD port Copyright (c) 2014, Roger Pau Monné
 * Fetched from git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
 * File: drivers/xen/evtchn.c
 * Git commit: 0dc0064add422bc0ef5165ebe9ece3052bbd457d
 *
 * 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 <sys/param.h>
#include <sys/systm.h>
#include <sys/uio.h>
#include <sys/bus.h>
#include <sys/malloc.h>
#include <sys/kernel.h>
#include <sys/lock.h>
#include <sys/mutex.h>
#include <sys/sx.h>
#include <sys/selinfo.h>
#include <sys/poll.h>
#include <sys/conf.h>
#include <sys/fcntl.h>
#include <sys/ioccom.h>
#include <sys/rman.h>
#include <sys/tree.h>
#include <sys/module.h>
#include <sys/filio.h>
#include <sys/vnode.h>

#include <xen/xen-os.h>
#include <xen/evtchn.h>
#include <xen/xen_intr.h>

#include <xen/evtchn/evtchnvar.h>

MALLOC_DEFINE(M_EVTCHN, "evtchn_dev", "Xen event channel user-space device");

struct user_evtchn;

static int evtchn_cmp(struct user_evtchn *u1, struct user_evtchn *u2);

RB_HEAD(evtchn_tree, user_evtchn);

struct per_user_data {
        struct mtx bind_mutex; /* serialize bind/unbind operations */
        struct evtchn_tree 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 sx ring_cons_mutex; /* protect against concurrent readers */
        struct mtx ring_prod_mutex; /* product against concurrent interrupts */
        struct selinfo ev_rsel;
};

struct user_evtchn {
        RB_ENTRY(user_evtchn) node;
        struct per_user_data *user;
        evtchn_port_t port;
        xen_intr_handle_t handle;
        bool enabled;
};

RB_GENERATE_STATIC(evtchn_tree, user_evtchn, node, evtchn_cmp);

static device_t evtchn_dev;

static d_read_t      evtchn_read;
static d_write_t     evtchn_write;
static d_ioctl_t     evtchn_ioctl;
static d_poll_t      evtchn_poll;
static d_open_t      evtchn_open;

static void evtchn_release(void *arg);

static struct cdevsw evtchn_devsw = {
        .d_version = D_VERSION,
        .d_open = evtchn_open,
        .d_read = evtchn_read,
        .d_write = evtchn_write,
        .d_ioctl = evtchn_ioctl,
        .d_poll = evtchn_poll,
        .d_name = "evtchn",
};

/*------------------------- Red-black tree helpers ---------------------------*/
static int
evtchn_cmp(struct user_evtchn *u1, struct user_evtchn *u2)
{

        return (u1->port - u2->port);
}

static struct user_evtchn *
find_evtchn(struct per_user_data *u, evtchn_port_t port)
{
        struct user_evtchn tmp = {
                .port = port,
        };

        return (RB_FIND(evtchn_tree, &u->evtchns, &tmp));
}

/*--------------------------- Interrupt handlers -----------------------------*/
static int
evtchn_filter(void *arg)
{
        struct user_evtchn *evtchn;

        evtchn = arg;

        if (!evtchn->enabled && bootverbose) {
                device_printf(evtchn_dev,
                    "Received upcall for disabled event channel %d\n",
                    evtchn->port);
        }

        evtchn_mask_port(evtchn->port);
        evtchn->enabled = false;

        return (FILTER_SCHEDULE_THREAD);
}

static void
evtchn_interrupt(void *arg)
{
        struct user_evtchn *evtchn;
        struct per_user_data *u;

        evtchn = arg;
        u = evtchn->user;

        /*
         * Protect against concurrent events using this handler
         * on different CPUs.
         */
        mtx_lock(&u->ring_prod_mutex);
        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++) {
                        wakeup(u);
                        selwakeup(&u->ev_rsel);
                }
        } else
                u->ring_overflow = 1;
        mtx_unlock(&u->ring_prod_mutex);
}

/*------------------------- Character device methods -------------------------*/
static int
evtchn_open(struct cdev *dev, int flag, int otyp, struct thread *td)
{
        struct per_user_data *u;
        int error;

        u = malloc(sizeof(*u), M_EVTCHN, M_WAITOK | M_ZERO);
        u->ring = malloc(PAGE_SIZE, M_EVTCHN, M_WAITOK | M_ZERO);

        /* Initialize locks */
        mtx_init(&u->bind_mutex, "evtchn_bind_mutex", NULL, MTX_DEF);
        sx_init(&u->ring_cons_mutex, "evtchn_ringc_sx");
        mtx_init(&u->ring_prod_mutex, "evtchn_ringp_mutex", NULL, MTX_DEF);

        /* Initialize red-black tree. */
        RB_INIT(&u->evtchns);

        /* Assign the allocated per_user_data to this open instance. */
        error = devfs_set_cdevpriv(u, evtchn_release);
        if (error != 0) {
                mtx_destroy(&u->bind_mutex);
                mtx_destroy(&u->ring_prod_mutex);
                sx_destroy(&u->ring_cons_mutex);
                free(u->ring, M_EVTCHN);
                free(u, M_EVTCHN);
        }

        return (error);
}

static void
evtchn_release(void *arg)
{
        struct per_user_data *u;
        struct user_evtchn *evtchn, *tmp;

        u = arg;

        seldrain(&u->ev_rsel);

        RB_FOREACH_SAFE(evtchn, evtchn_tree, &u->evtchns, tmp) {
                xen_intr_unbind(&evtchn->handle);

                RB_REMOVE(evtchn_tree, &u->evtchns, evtchn);
                free(evtchn, M_EVTCHN);
        }

        mtx_destroy(&u->bind_mutex);
        mtx_destroy(&u->ring_prod_mutex);
        sx_destroy(&u->ring_cons_mutex);
        free(u->ring, M_EVTCHN);
        free(u, M_EVTCHN);
}

static int
evtchn_read(struct cdev *dev, struct uio *uio, int ioflag)
{
        int error, count;
        unsigned int c, p, bytes1 = 0, bytes2 = 0;
        struct per_user_data *u;

        error = devfs_get_cdevpriv((void **)&u);
        if (error != 0)
                return (EINVAL);

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

        if (count == 0)
                return (0);

        if (count > PAGE_SIZE)
                count = PAGE_SIZE;

        sx_xlock(&u->ring_cons_mutex);
        for (;;) {
                if (u->ring_overflow) {
                        error = EFBIG;
                        goto unlock_out;
                }

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

                if (ioflag & IO_NDELAY) {
                        error = EWOULDBLOCK;
                        goto unlock_out;
                }

                error = sx_sleep(u, &u->ring_cons_mutex, PCATCH, "evtchw", 0);
                if ((error != 0) && (error != EWOULDBLOCK))
                        goto unlock_out;
        }

        /* 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;
        }

        error = EFAULT;
        rmb(); /* Ensure that we see the port before we copy it. */

        if (uiomove(&u->ring[EVTCHN_RING_MASK(c)], bytes1, uio) ||
            ((bytes2 != 0) && uiomove(&u->ring[0], bytes2, uio)))
                goto unlock_out;

        u->ring_cons += (bytes1 + bytes2) / sizeof(evtchn_port_t);
        error = 0;

unlock_out:
        sx_xunlock(&u->ring_cons_mutex);
        return (error);
}

static int
evtchn_write(struct cdev *dev, struct uio *uio, int ioflag)
{
        int error, i, count;
        evtchn_port_t *kbuf;
        struct per_user_data *u;

        error = devfs_get_cdevpriv((void **)&u);
        if (error != 0)
                return (EINVAL);

        kbuf = malloc(PAGE_SIZE, M_EVTCHN, M_WAITOK);

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

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

        if (count > PAGE_SIZE)
                count = PAGE_SIZE;

        error = uiomove(kbuf, count, uio);
        if (error != 0)
                goto out;

        mtx_lock(&u->bind_mutex);

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

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

        mtx_unlock(&u->bind_mutex);
        error = 0;

out:
        free(kbuf, M_EVTCHN);
        return (error);
}

static inline int
evtchn_bind_user_port(struct per_user_data *u, struct user_evtchn *evtchn)
{
        int error;

        evtchn->port = xen_intr_port(evtchn->handle);
        evtchn->user = u;
        evtchn->enabled = true;
        mtx_lock(&u->bind_mutex);
        RB_INSERT(evtchn_tree, &u->evtchns, evtchn);
        mtx_unlock(&u->bind_mutex);
        error = xen_intr_add_handler(device_get_nameunit(evtchn_dev),
            evtchn_filter, evtchn_interrupt, evtchn,
            INTR_TYPE_MISC | INTR_MPSAFE, evtchn->handle);
        if (error != 0) {
                xen_intr_unbind(&evtchn->handle);
                mtx_lock(&u->bind_mutex);
                RB_REMOVE(evtchn_tree, &u->evtchns, evtchn);
                mtx_unlock(&u->bind_mutex);
                free(evtchn, M_EVTCHN);
        }
        return (error);
}

static int
evtchn_ioctl(struct cdev *dev, unsigned long cmd, caddr_t arg,
    int mode, struct thread *td __unused)
{
        struct per_user_data *u;
        int error;

        error = devfs_get_cdevpriv((void **)&u);
        if (error != 0)
                return (EINVAL);

        switch (cmd) {
        case IOCTL_EVTCHN_BIND_VIRQ: {
                struct ioctl_evtchn_bind_virq *bind;
                struct user_evtchn *evtchn;

                evtchn = malloc(sizeof(*evtchn), M_EVTCHN, M_WAITOK | M_ZERO);

                bind = (struct ioctl_evtchn_bind_virq *)arg;

                error = xen_intr_bind_virq(evtchn_dev, bind->virq, 0,
                    NULL, NULL, NULL, 0, &evtchn->handle);
                if (error != 0) {
                        free(evtchn, M_EVTCHN);
                        break;
                }
                error = evtchn_bind_user_port(u, evtchn);
                if (error != 0)
                        break;
                bind->port = evtchn->port;
                break;
        }

        case IOCTL_EVTCHN_BIND_INTERDOMAIN: {
                struct ioctl_evtchn_bind_interdomain *bind;
                struct user_evtchn *evtchn;

                evtchn = malloc(sizeof(*evtchn), M_EVTCHN, M_WAITOK | M_ZERO);

                bind = (struct ioctl_evtchn_bind_interdomain *)arg;

                error = xen_intr_bind_remote_port(evtchn_dev,
                    bind->remote_domain, bind->remote_port, NULL,
                    NULL, NULL, 0, &evtchn->handle);
                if (error != 0) {
                        free(evtchn, M_EVTCHN);
                        break;
                }
                error = evtchn_bind_user_port(u, evtchn);
                if (error != 0)
                        break;
                bind->port = evtchn->port;
                break;
        }

        case IOCTL_EVTCHN_BIND_UNBOUND_PORT: {
                struct ioctl_evtchn_bind_unbound_port *bind;
                struct user_evtchn *evtchn;

                evtchn = malloc(sizeof(*evtchn), M_EVTCHN, M_WAITOK | M_ZERO);

                bind = (struct ioctl_evtchn_bind_unbound_port *)arg;

                error = xen_intr_alloc_and_bind_local_port(evtchn_dev,
                    bind->remote_domain, NULL, NULL, NULL, 0, &evtchn->handle);
                if (error != 0) {
                        free(evtchn, M_EVTCHN);
                        break;
                }
                error = evtchn_bind_user_port(u, evtchn);
                if (error != 0)
                        break;
                bind->port = evtchn->port;
                break;
        }

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

                unbind = (struct ioctl_evtchn_unbind *)arg;

                mtx_lock(&u->bind_mutex);
                evtchn = find_evtchn(u, unbind->port);
                if (evtchn == NULL) {
                        error = ENOTCONN;
                        break;
                }
                RB_REMOVE(evtchn_tree, &u->evtchns, evtchn);
                mtx_unlock(&u->bind_mutex);

                xen_intr_unbind(&evtchn->handle);
                free(evtchn, M_EVTCHN);
                error = 0;
                break;
        }

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

                notify = (struct ioctl_evtchn_notify *)arg;

                mtx_lock(&u->bind_mutex);
                evtchn = find_evtchn(u, notify->port);
                if (evtchn == NULL) {
                        error = ENOTCONN;
                        break;
                }

                xen_intr_signal(evtchn->handle);
                mtx_unlock(&u->bind_mutex);
                error = 0;
                break;
        }

        case IOCTL_EVTCHN_RESET: {
                /* Initialise the ring to empty. Clear errors. */
                sx_xlock(&u->ring_cons_mutex);
                mtx_lock(&u->ring_prod_mutex);
                u->ring_cons = u->ring_prod = u->ring_overflow = 0;
                mtx_unlock(&u->ring_prod_mutex);
                sx_xunlock(&u->ring_cons_mutex);
                error = 0;
                break;
        }

        case FIONBIO:
        case FIOASYNC:
                /* Handled in an upper layer */
                error = 0;
                break;

        default:
                error = ENOTTY;
                break;
        }

        return (error);
}

static int
evtchn_poll(struct cdev *dev, int events, struct thread *td)
{
        struct per_user_data *u;
        int error, mask;

        error = devfs_get_cdevpriv((void **)&u);
        if (error != 0)
                return (POLLERR);

        /* we can always write */
        mask = events & (POLLOUT | POLLWRNORM);

        mtx_lock(&u->ring_prod_mutex);
        if (events & (POLLIN | POLLRDNORM)) {
                if (u->ring_cons != u->ring_prod) {
                        mask |= events & (POLLIN | POLLRDNORM);
                } else {
                        /* Record that someone is waiting */
                        selrecord(td, &u->ev_rsel);
                }
        }
        mtx_unlock(&u->ring_prod_mutex);

        return (mask);
}

/*------------------ Private Device Attachment Functions  --------------------*/
static void
evtchn_identify(driver_t *driver, device_t parent)
{

        KASSERT((xen_domain()),
            ("Trying to attach evtchn device on non Xen domain"));

        evtchn_dev = BUS_ADD_CHILD(parent, 0, "evtchn", 0);
        if (evtchn_dev == NULL)
                panic("unable to attach evtchn user-space device");
}

static int
evtchn_probe(device_t dev)
{

        device_set_desc(dev, "Xen event channel user-space device");
        return (BUS_PROBE_NOWILDCARD);
}

static int
evtchn_attach(device_t dev)
{

        make_dev_credf(MAKEDEV_ETERNAL, &evtchn_devsw, 0, NULL, UID_ROOT,
            GID_WHEEL, 0600, "xen/evtchn");
        return (0);
}

/*-------------------- Private Device Attachment Data  -----------------------*/
static device_method_t evtchn_methods[] = {
        DEVMETHOD(device_identify, evtchn_identify),
        DEVMETHOD(device_probe, evtchn_probe),
        DEVMETHOD(device_attach, evtchn_attach),

        DEVMETHOD_END
};

static driver_t evtchn_driver = {
        "evtchn",
        evtchn_methods,
        0,
};

DRIVER_MODULE(evtchn, xenpv, evtchn_driver, 0, 0);
MODULE_DEPEND(evtchn, xenpv, 1, 1, 1);