/*
 * Copyright (c) 2015 Julien Grall <julien.grall@citrix.com>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/param.h>
#include <sys/module.h>
#include <sys/systm.h>
#include <sys/eventhandler.h>
#include <sys/consio.h>
#include <sys/priv.h>
#include <sys/proc.h>
#include <sys/uio.h>
#include <sys/tty.h>
#include <sys/systm.h>
#include <sys/taskqueue.h>
#include <sys/conf.h>
#include <sys/kernel.h>
#include <sys/bus.h>
#include <sys/cons.h>
#include <sys/kdb.h>
#include <sys/proc.h>
#include <sys/reboot.h>
#include <sys/stdarg.h>

#include <vm/vm.h>
#include <vm/pmap.h>

#include <xen/xen-os.h>
#include <xen/hypervisor.h>
#include <xen/xen_intr.h>
#include <contrib/xen/io/console.h>

#include "opt_ddb.h"
#include "opt_printf.h"

#ifdef DDB
#include <ddb/ddb.h>
#endif

static char driver_name[] = "xc";

struct xencons_priv;

typedef void xencons_early_init_t(struct xencons_priv *cons);
typedef int xencons_init_t(device_t dev, struct tty *tp,
    driver_intr_t intr_handler);
typedef int xencons_read_t(struct xencons_priv *cons, char *buffer,
    unsigned int size);
typedef int xencons_write_t(struct xencons_priv *cons, const char *buffer,
    unsigned int size);

struct xencons_ops {
        /*
         * Called by the low-level driver during early boot.
         * Only the minimal set up to get a console should be done here.
         */
        xencons_early_init_t    *early_init;
        /* Prepare the console to be fully use */
        xencons_init_t          *init;
        /* Read/write helpers */
        xencons_read_t          *read;
        xencons_write_t         *write;
};

struct xencons_priv {
        /* Mutex to protect the shared ring and the internal buffers */
        struct mtx                      mtx;
        /* Interrupt handler used for notify the backend */
        xen_intr_handle_t               intr_handle;
        /* KDB internal state */
#ifdef KDB
        int                             altbrk;
#endif
        /* Status of the tty */
        bool                            opened;
        /* Callout used when the write buffer is full */
        struct callout                  callout;

        /* Internal buffers must be used with mtx locked */
#define WBUF_SIZE     4096
#define WBUF_MASK(_i) ((_i)&(WBUF_SIZE-1))
        char                            wbuf[WBUF_SIZE];
        unsigned int                    wc, wp; /* Consumer/producer wbuf */

#define RBUF_SIZE     1024
#define RBUF_MASK(_i) ((_i)&(RBUF_SIZE-1))
        char                            rbuf[RBUF_SIZE];
        unsigned int                    rc, rp; /* Consumer/producer rbuf */

        /* Pointer to the console operations */
        const struct xencons_ops        *ops;

        /*
         * Ring specific fields
         * XXX: make an union?
         */
        /* Event channel number for early notification (PV only) */
        uint32_t                        evtchn;
        /* Console shared page */
        struct xencons_interface        *intf;
};

/*
 * Data for the main console
 * Necessary to support low-level console driver
 */
static struct xencons_priv main_cons;

#define XC_POLLTIME     (hz/10)

/*----------------------------- Debug function ------------------------------*/
struct putchar_arg {
        char    *buf;
        size_t  size;
        size_t  n_next;
};

void __weak_symbol
xen_emergency_print(const char *str, size_t size)
{
        KASSERT((xen_domain()), ("call to xc_printf from non Xen guest"));
        HYPERVISOR_console_write(str, size);
}

static void
putchar(int c, void *arg)
{
        struct putchar_arg *pca;

        pca = (struct putchar_arg *)arg;

        if (pca->buf == NULL) {
                /*
                 * We have no buffer, output directly to the
                 * console char by char.
                 */
                xen_emergency_print((char *)&c, 1);
        } else {
                pca->buf[pca->n_next++] = c;
                if ((pca->size == pca->n_next) || (c = '\0')) {
                        /* Flush the buffer */
                        xen_emergency_print(pca->buf, pca->n_next);
                        pca->n_next = 0;
                }
        }
}

void
xc_printf(const char *fmt, ...)
{
        va_list ap;
        struct putchar_arg pca;
#ifdef PRINTF_BUFR_SIZE
        char buf[PRINTF_BUFR_SIZE];

        pca.buf = buf;
        pca.size = sizeof(buf);
        pca.n_next = 0;
#else
        pca.buf = NULL;
        pca.size = 0;
#endif

        va_start(ap, fmt);
        kvprintf(fmt, putchar, &pca, 10, ap);
        va_end(ap);

#ifdef PRINTF_BUFR_SIZE
        if (pca.n_next != 0)
                xen_emergency_print(buf, pca.n_next);
#endif
}

/*---------------------- Helpers for the console lock -----------------------*/
/*
 * The lock is not used when the kernel is panicing as it will never recover
 * and we want to output no matter what it costs.
 */
static inline void xencons_lock(struct xencons_priv *cons)
{

        if (!KERNEL_PANICKED())
                mtx_lock_spin(&cons->mtx);

}

static inline void xencons_unlock(struct xencons_priv *cons)
{

        if (!KERNEL_PANICKED())
                mtx_unlock_spin(&cons->mtx);
}

#define xencons_lock_assert(cons)       mtx_assert(&(cons)->mtx, MA_OWNED)

/*------------------ Helpers for the hypervisor console ---------------------*/
static void
xencons_early_init_hypervisor(struct xencons_priv *cons)
{
        /*
         * Nothing to setup for the low-level console when using
         * the hypervisor console.
         */
}

static int
xencons_init_hypervisor(device_t dev, struct tty *tp,
    driver_intr_t intr_handler)
{
        struct xencons_priv *cons;
        int err;

        cons = tty_softc(tp);

        err = xen_intr_bind_virq(dev, VIRQ_CONSOLE, 0, NULL,
            intr_handler, tp, INTR_TYPE_TTY | INTR_MPSAFE, &cons->intr_handle);
        if (err != 0)
                device_printf(dev, "Can't register console interrupt\n");

        return (err);
}

static int
xencons_write_hypervisor(struct xencons_priv *cons, const char *buffer,
    unsigned int size)
{

        HYPERVISOR_console_io(CONSOLEIO_write, size, buffer);

        return (size);
}

static int
xencons_read_hypervisor(struct xencons_priv *cons, char *buffer,
    unsigned int size)
{

        xencons_lock_assert(cons);

        return (HYPERVISOR_console_io(CONSOLEIO_read, size, buffer));
}

static const struct xencons_ops xencons_hypervisor_ops = {
        .early_init     = xencons_early_init_hypervisor,
        .init           = xencons_init_hypervisor,
        .read           = xencons_read_hypervisor,
        .write          = xencons_write_hypervisor,
};

/*------------------ Helpers for the ring console ---------------------------*/
static void
xencons_early_init_ring(struct xencons_priv *cons)
{
        cons->intf = pmap_mapdev_attr(ptoa(xen_get_console_mfn()), PAGE_SIZE,
            VM_MEMATTR_XEN);
        cons->evtchn = xen_get_console_evtchn();
}

static int
xencons_init_ring(device_t dev, struct tty *tp, driver_intr_t intr_handler)
{
        struct xencons_priv *cons;
        int err;

        cons = tty_softc(tp);

        if (cons->evtchn == 0)
                return (ENODEV);

        err = xen_intr_bind_local_port(dev, cons->evtchn, NULL,
            intr_handler, tp, INTR_TYPE_TTY | INTR_MPSAFE, &cons->intr_handle);
        if (err != 0)
                return (err);

        return (0);
}

static void
xencons_notify_ring(struct xencons_priv *cons)
{
        /*
         * The console may be used before the ring interrupt is properly
         * initialized.
         * If so, fallback to directly use the event channel hypercall.
         */
        if (__predict_true(cons->intr_handle != NULL))
                xen_intr_signal(cons->intr_handle);
        else {
                struct evtchn_send send = {
                        .port = cons->evtchn
                };

                HYPERVISOR_event_channel_op(EVTCHNOP_send, &send);
        }
}

static int
xencons_write_ring(struct xencons_priv *cons, const char *buffer,
    unsigned int size)
{
        struct xencons_interface *intf;
        XENCONS_RING_IDX wcons, wprod;
        int sent;

        intf = cons->intf;

        xencons_lock_assert(cons);

        wcons = intf->out_cons;
        wprod = intf->out_prod;

        mb();
        KASSERT((wprod - wcons) <= sizeof(intf->out),
                ("console send ring inconsistent"));

        for (sent = 0; sent < size; sent++, wprod++) {
                if ((wprod - wcons) >= sizeof(intf->out))
                        break;
                intf->out[MASK_XENCONS_IDX(wprod, intf->out)] = buffer[sent];
        }

        wmb();
        intf->out_prod = wprod;

        xencons_notify_ring(cons);

        return (sent);
}

static int
xencons_read_ring(struct xencons_priv *cons, char *buffer, unsigned int size)
{
        struct xencons_interface *intf;
        XENCONS_RING_IDX rcons, rprod;
        unsigned int rsz;

        intf = cons->intf;

        xencons_lock_assert(cons);

        rcons = intf->in_cons;
        rprod = intf->in_prod;
        rmb();

        for (rsz = 0; rsz < size; rsz++, rcons++) {
                if (rprod == rcons)
                        break;
                buffer[rsz] = intf->in[MASK_XENCONS_IDX(rcons, intf->in)];
        }

        wmb();
        intf->in_cons = rcons;

        /* No need to notify the backend if nothing has been read */
        if (rsz != 0)
                xencons_notify_ring(cons);

        return (rsz);
}

static const struct xencons_ops xencons_ring_ops = {
        .early_init     = xencons_early_init_ring,
        .init           = xencons_init_ring,
        .read           = xencons_read_ring,
        .write          = xencons_write_ring,
};

/*------------------ Common implementation of the console -------------------*/

/*
 * Called by the low-level driver during early boot to initialize the
 * main console driver.
 * Only the minimal set up to get a console should be done here.
 */
static void
xencons_early_init(void)
{

        mtx_init(&main_cons.mtx, "XCONS LOCK", NULL, MTX_SPIN);

        if (xen_get_console_evtchn() == 0)
                main_cons.ops = &xencons_hypervisor_ops;
        else
                main_cons.ops = &xencons_ring_ops;

        main_cons.ops->early_init(&main_cons);
}

/*
 * Receive character from the console and put them in the internal buffer
 * XXX: Handle overflow of the internal buffer
 */
static void
xencons_rx(struct xencons_priv *cons)
{
        char buf[16];
        int sz;

        xencons_lock(cons);
        while ((sz = cons->ops->read(cons, buf, sizeof(buf))) > 0) {
                int i;

                for (i = 0; i < sz; i++)
                        cons->rbuf[RBUF_MASK(cons->rp++)] = buf[i];
        }
        xencons_unlock(cons);
}

/* Return true if the write buffer is full */
static bool
xencons_tx_full(struct xencons_priv *cons)
{
        unsigned int used;

        xencons_lock(cons);
        used = cons->wp - cons->wc;
        xencons_unlock(cons);

        return (used >= WBUF_SIZE);
}

static void
xencons_tx_flush(struct xencons_priv *cons, int force)
{
        int        sz;

        xencons_lock(cons);
        while (cons->wc != cons->wp) {
                int sent;
                sz = cons->wp - cons->wc;
                if (sz > (WBUF_SIZE - WBUF_MASK(cons->wc)))
                        sz = WBUF_SIZE - WBUF_MASK(cons->wc);
                sent = cons->ops->write(cons, &cons->wbuf[WBUF_MASK(cons->wc)],
                    sz);

                /*
                 * The other end may not have been initialized. Ignore
                 * the force.
                 */
                if (__predict_false(sent < 0))
                        break;

                /*
                 * If force is set, spin until the console data is
                 * flushed through the domain controller.
                 */
                if (sent == 0 && __predict_true(!force))
                        break;

                cons->wc += sent;
        }
        xencons_unlock(cons);
}

static bool
xencons_putc(struct xencons_priv *cons, int c, bool force_flush)
{

        xencons_lock(cons);
        if ((cons->wp - cons->wc) < WBUF_SIZE)
                cons->wbuf[WBUF_MASK(cons->wp++)] = c;
        xencons_unlock(cons);

        xencons_tx_flush(cons, force_flush);

        return (xencons_tx_full(cons));
}

static int
xencons_getc(struct xencons_priv *cons)
{
        int ret;

        xencons_lock(cons);
        if (cons->rp != cons->rc) {
                /* We need to return only one char */
                ret = (int)cons->rbuf[RBUF_MASK(cons->rc)];
                cons->rc++;
        } else {
                ret = -1;
        }

        xencons_unlock(cons);

        return (ret);
}

static bool
xencons_tx(struct tty *tp)
{
        bool cons_full;
        char c;
        struct xencons_priv *cons;

        cons = tty_softc(tp);

        tty_assert_locked(tp);

        /*
         * Don't transmit any character if the buffer is full. Otherwise,
         * characters may be lost
         */
        if (xencons_tx_full(cons))
                return (false);

        cons_full = false;
        while (!cons_full && ttydisc_getc(tp, &c, 1) == 1)
                cons_full = xencons_putc(cons, c, false);

        return (!cons_full);
}

static void
xencons_intr(void *arg)
{
        struct tty *tp;
        struct xencons_priv *cons;
        int ret;

        tp = arg;
        cons = tty_softc(tp);

        /*
         * The input will be used by the low-level console when KDB is active
         */
        if (kdb_active)
                return;

        /*
         * It's not necessary to retrieve input when the tty is not opened
         */
        if (!cons->opened)
                return;

        xencons_rx(cons);

        tty_lock(tp);
        while ((ret = xencons_getc(cons)) != -1) {
#ifdef KDB
                kdb_alt_break(ret, &cons->altbrk);
#endif
                ttydisc_rint(tp, ret, 0);
        }
        ttydisc_rint_done(tp);
        tty_unlock(tp);

        /* Try to flush remaining characters if necessary */
        xencons_tx_flush(cons, 0);
}

/*
 * Helpers to call while shutting down:
 *      - Force flush all output
 */
static void
xencons_shutdown(void *arg, int howto)
{
        struct tty *tp;

        tp = arg;

        xencons_tx_flush(tty_softc(tp), 1);
}

/*---------------------- Low-level console driver ---------------------------*/
static void
xencons_cnprobe(struct consdev *cp)
{

        if (!xen_domain())
                return;

        cp->cn_pri = (boothowto & RB_SERIAL) ? CN_REMOTE : CN_NORMAL;
        sprintf(cp->cn_name, "%s0", driver_name);
}

static void
xencons_cninit(struct consdev *cp)
{

        xencons_early_init();
}

static void
xencons_cnterm(struct consdev *cp)
{
}

static void
xencons_cngrab(struct consdev *cp)
{
}

static void
xencons_cnungrab(struct consdev *cp)
{
}

static int
xencons_cngetc(struct consdev *dev)
{

        xencons_rx(&main_cons);

        return (xencons_getc(&main_cons));
}

static void
xencons_cnputc(struct consdev *dev, int c)
{
        /*
         * The low-level console is used by KDB and panic. We have to ensure
         * that any character sent will be seen by the backend.
         */
        xencons_putc(&main_cons, c, true);
}

CONSOLE_DRIVER(xencons);

/*----------------------------- TTY driver ---------------------------------*/

static int
xencons_tty_open(struct tty *tp)
{
        struct xencons_priv *cons;

        cons = tty_softc(tp);

        cons->opened = true;

        return (0);
}

static void
xencons_tty_close(struct tty *tp)
{
        struct xencons_priv *cons;

        cons = tty_softc(tp);

        cons->opened = false;
}

static void
xencons_timeout(void *v)
{
        struct tty *tp;
        struct xencons_priv *cons;

        tp = v;
        cons = tty_softc(tp);

        if (!xencons_tx(tp))
                callout_reset(&cons->callout, XC_POLLTIME,
                    xencons_timeout, tp);
}

static void
xencons_tty_outwakeup(struct tty *tp)
{
        struct xencons_priv *cons;

        cons = tty_softc(tp);

        callout_stop(&cons->callout);

        if (!xencons_tx(tp))
                callout_reset(&cons->callout, XC_POLLTIME,
                    xencons_timeout, tp);
}

static struct ttydevsw xencons_ttydevsw = {
        .tsw_flags      = TF_NOPREFIX,
        .tsw_open       = xencons_tty_open,
        .tsw_close      = xencons_tty_close,
        .tsw_outwakeup  = xencons_tty_outwakeup,
};

/*------------------------ Main console driver ------------------------------*/
static void
xencons_identify(driver_t *driver, device_t parent)
{
        device_t child __unused;

        if (main_cons.ops == NULL)
                return;

        child = BUS_ADD_CHILD(parent, 0, driver_name, 0);
}

static int
xencons_probe(device_t dev)
{

        device_set_desc(dev, "Xen Console");
        return (BUS_PROBE_NOWILDCARD);
}

static int
xencons_attach(device_t dev)
{
        struct tty *tp;
        /*
         * The main console is already allocated statically in order to
         * support low-level console
         */
        struct xencons_priv *cons;
        int err;

        cons = &main_cons;

        tp = tty_alloc(&xencons_ttydevsw, cons);
        tty_makedev(tp, NULL, "%s%r", driver_name, 0);
        device_set_softc(dev, tp);

        callout_init_mtx(&cons->callout, tty_getlock(tp), 0);

        err = cons->ops->init(dev, tp, xencons_intr);
        if (err != 0) {
                device_printf(dev, "Unable to initialize the console (%d)\n",
                    err);
                return (err);
        }

        /* register handler to flush console on shutdown */
        if ((EVENTHANDLER_REGISTER(shutdown_post_sync, xencons_shutdown,
            tp, SHUTDOWN_PRI_DEFAULT)) == NULL)
                device_printf(dev, "shutdown event registration failed!\n");

        return (0);
}

static int
xencons_resume(device_t dev)
{
        struct xencons_priv *cons;
        struct tty *tp;
        int err;

        tp = device_get_softc(dev);
        cons = tty_softc(tp);
        xen_intr_unbind(&cons->intr_handle);

        err = cons->ops->init(dev, tp, xencons_intr);
        if (err != 0) {
                device_printf(dev, "Unable to resume the console (%d)\n", err);
                return (err);
        }

        return (0);
}

static device_method_t xencons_methods[] = {
        DEVMETHOD(device_identify, xencons_identify),
        DEVMETHOD(device_probe, xencons_probe),
        DEVMETHOD(device_attach, xencons_attach),
        DEVMETHOD(device_resume, xencons_resume),

        DEVMETHOD_END
};

static driver_t xencons_driver = {
        driver_name,
        xencons_methods,
        0,
};

DRIVER_MODULE(xc, xenpv, xencons_driver, 0, 0);