/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2011 NetApp, Inc.
 * 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 NETAPP, INC ``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 NETAPP, INC 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.
 */

/*
 * Micro event library for FreeBSD, designed for a single i/o thread
 * using kqueue, and having events be persistent by default.
 */

#include <sys/cdefs.h>
#include <assert.h>
#ifndef WITHOUT_CAPSICUM
#include <capsicum_helpers.h>
#endif
#include <err.h>
#include <errno.h>
#include <stdbool.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <sysexits.h>
#include <unistd.h>

#include <sys/types.h>
#ifndef WITHOUT_CAPSICUM
#include <sys/capsicum.h>
#endif
#include <sys/event.h>
#include <sys/time.h>

#include <pthread.h>
#include <pthread_np.h>

#include "bhyverun.h"
#include "mevent.h"

#define MEVENT_MAX      64

static pthread_t mevent_tid;
static pthread_once_t mevent_once = PTHREAD_ONCE_INIT;
static int mevent_timid = 43;
static int mevent_pipefd[2];
static int mfd;
static pthread_mutex_t mevent_lmutex = PTHREAD_MUTEX_INITIALIZER;

struct mevent {
        void    (*me_func)(int, enum ev_type, void *);
#define me_msecs me_fd
        int     me_fd;
        int     me_timid;
        enum ev_type me_type;
        void    *me_param;
        int     me_cq;
        int     me_state; /* Desired kevent flags. */
        int     me_closefd;
        int     me_fflags;
        LIST_ENTRY(mevent) me_list;
};

enum mevent_update_type {
        UPDATE_ENABLE,
        UPDATE_DISABLE,
        UPDATE_TIMER,
};

static LIST_HEAD(listhead, mevent) global_head, change_head;

static void
mevent_qlock(void)
{
        pthread_mutex_lock(&mevent_lmutex);
}

static void
mevent_qunlock(void)
{
        pthread_mutex_unlock(&mevent_lmutex);
}

static void
mevent_pipe_read(int fd, enum ev_type type __unused, void *param __unused)
{
        char buf[MEVENT_MAX];
        int status;

        /*
         * Drain the pipe read side. The fd is non-blocking so this is
         * safe to do.
         */
        do {
                status = read(fd, buf, sizeof(buf));
        } while (status == MEVENT_MAX);
}

static void
mevent_notify(void)
{
        char c = '\0';

        /*
         * If calling from outside the i/o thread, write a byte on the
         * pipe to force the i/o thread to exit the blocking kevent call.
         */
        if (mevent_pipefd[1] != 0 && pthread_self() != mevent_tid) {
                write(mevent_pipefd[1], &c, 1);
        }
}

static void
mevent_init(void)
{
#ifndef WITHOUT_CAPSICUM
        cap_rights_t rights;
#endif

        mfd = kqueue();
        assert(mfd > 0);

#ifndef WITHOUT_CAPSICUM
        cap_rights_init(&rights, CAP_KQUEUE);
        if (caph_rights_limit(mfd, &rights) == -1)
                errx(EX_OSERR, "Unable to apply rights for sandbox");
#endif

        LIST_INIT(&change_head);
        LIST_INIT(&global_head);
}

static int
mevent_kq_filter(struct mevent *mevp)
{
        int retval;

        retval = 0;

        if (mevp->me_type == EVF_READ)
                retval = EVFILT_READ;

        if (mevp->me_type == EVF_WRITE)
                retval = EVFILT_WRITE;

        if (mevp->me_type == EVF_TIMER)
                retval = EVFILT_TIMER;

        if (mevp->me_type == EVF_SIGNAL)
                retval = EVFILT_SIGNAL;

        if (mevp->me_type == EVF_VNODE)
                retval = EVFILT_VNODE;

        return (retval);
}

static int
mevent_kq_flags(struct mevent *mevp)
{
        int retval;

        retval = mevp->me_state;

        if (mevp->me_type == EVF_VNODE)
                retval |= EV_CLEAR;

        return (retval);
}

static int
mevent_kq_fflags(struct mevent *mevp)
{
        int retval;

        retval = 0;

        switch (mevp->me_type) {
        case EVF_VNODE:
                if ((mevp->me_fflags & EVFF_ATTRIB) != 0)
                        retval |= NOTE_ATTRIB;
                break;
        case EVF_READ:
        case EVF_WRITE:
        case EVF_TIMER:
        case EVF_SIGNAL:
                break;
        }

        return (retval);
}

static void
mevent_populate(struct mevent *mevp, struct kevent *kev)
{
        if (mevp->me_type == EVF_TIMER) {
                kev->ident = mevp->me_timid;
                kev->data = mevp->me_msecs;
        } else {
                kev->ident = mevp->me_fd;
                kev->data = 0;
        }
        kev->filter = mevent_kq_filter(mevp);
        kev->flags = mevent_kq_flags(mevp);
        kev->fflags = mevent_kq_fflags(mevp);
        kev->udata = mevp;
}

static int
mevent_build(struct kevent *kev)
{
        struct mevent *mevp, *tmpp;
        int i;

        i = 0;

        mevent_qlock();

        LIST_FOREACH_SAFE(mevp, &change_head, me_list, tmpp) {
                if (mevp->me_closefd) {
                        /*
                         * A close of the file descriptor will remove the
                         * event
                         */
                        close(mevp->me_fd);
                } else {
                        mevent_populate(mevp, &kev[i]);
                        i++;
                }

                mevp->me_cq = 0;
                LIST_REMOVE(mevp, me_list);

                if (mevp->me_state & EV_DELETE) {
                        free(mevp);
                } else {
                        LIST_INSERT_HEAD(&global_head, mevp, me_list);
                }

                assert(i < MEVENT_MAX);
        }

        mevent_qunlock();

        return (i);
}

static void
mevent_handle(struct kevent *kev, int numev)
{
        struct mevent *mevp;
        int i;

        for (i = 0; i < numev; i++) {
                mevp = kev[i].udata;

                /* XXX check for EV_ERROR ? */

                (*mevp->me_func)(mevp->me_fd, mevp->me_type, mevp->me_param);
        }
}

static struct mevent *
mevent_add_state(int tfd, enum ev_type type,
           void (*func)(int, enum ev_type, void *), void *param,
           int state, int fflags)
{
        struct kevent kev;
        struct mevent *lp, *mevp;
        int ret;

        if (tfd < 0 || func == NULL) {
                return (NULL);
        }

        mevp = NULL;

        pthread_once(&mevent_once, mevent_init);

        mevent_qlock();

        /*
         * Verify that the fd/type tuple is not present in any list
         */
        LIST_FOREACH(lp, &global_head, me_list) {
                if (type != EVF_TIMER && lp->me_fd == tfd &&
                    lp->me_type == type) {
                        goto exit;
                }
        }

        LIST_FOREACH(lp, &change_head, me_list) {
                if (type != EVF_TIMER && lp->me_fd == tfd &&
                    lp->me_type == type) {
                        goto exit;
                }
        }

        /*
         * Allocate an entry and populate it.
         */
        mevp = calloc(1, sizeof(struct mevent));
        if (mevp == NULL) {
                goto exit;
        }

        if (type == EVF_TIMER) {
                mevp->me_msecs = tfd;
                mevp->me_timid = mevent_timid++;
        } else
                mevp->me_fd = tfd;
        mevp->me_type = type;
        mevp->me_func = func;
        mevp->me_param = param;
        mevp->me_state = state;
        mevp->me_fflags = fflags;

        /*
         * Try to add the event.  If this fails, report the failure to
         * the caller.
         */
        mevent_populate(mevp, &kev);
        ret = kevent(mfd, &kev, 1, NULL, 0, NULL);
        if (ret == -1) {
                free(mevp);
                mevp = NULL;
                goto exit;
        }

        mevp->me_state &= ~EV_ADD;
        LIST_INSERT_HEAD(&global_head, mevp, me_list);

exit:
        mevent_qunlock();

        return (mevp);
}

struct mevent *
mevent_add(int tfd, enum ev_type type,
           void (*func)(int, enum ev_type, void *), void *param)
{

        return (mevent_add_state(tfd, type, func, param, EV_ADD, 0));
}

struct mevent *
mevent_add_flags(int tfd, enum ev_type type, int fflags,
                 void (*func)(int, enum ev_type, void *), void *param)
{

        return (mevent_add_state(tfd, type, func, param, EV_ADD, fflags));
}

struct mevent *
mevent_add_disabled(int tfd, enum ev_type type,
                    void (*func)(int, enum ev_type, void *), void *param)
{

        return (mevent_add_state(tfd, type, func, param, EV_ADD | EV_DISABLE, 0));
}

static int
mevent_update(struct mevent *evp, enum mevent_update_type type, int msecs)
{
        int newstate;

        mevent_qlock();

        /*
         * It's not possible to update a deleted event
         */
        assert((evp->me_state & EV_DELETE) == 0);

        newstate = evp->me_state;
        if (type == UPDATE_ENABLE) {
                newstate |= EV_ENABLE;
                newstate &= ~EV_DISABLE;
        } else if (type == UPDATE_DISABLE) {
                newstate |= EV_DISABLE;
                newstate &= ~EV_ENABLE;
        } else {
                assert(type == UPDATE_TIMER);
                assert(evp->me_type == EVF_TIMER);
                newstate |= EV_ADD;
                evp->me_msecs = msecs;
        }

        /*
         * No update needed if enable/disable had no effect
         */
        if (evp->me_state != newstate || type == UPDATE_TIMER) {
                evp->me_state = newstate;

                /*
                 * Place the entry onto the changed list if not
                 * already there.
                 */
                if (evp->me_cq == 0) {
                        evp->me_cq = 1;
                        LIST_REMOVE(evp, me_list);
                        LIST_INSERT_HEAD(&change_head, evp, me_list);
                        mevent_notify();
                }
        }

        mevent_qunlock();

        return (0);
}

int
mevent_enable(struct mevent *evp)
{
        return (mevent_update(evp, UPDATE_ENABLE, -1));
}

int
mevent_disable(struct mevent *evp)
{
        return (mevent_update(evp, UPDATE_DISABLE, -1));
}

int
mevent_timer_update(struct mevent *evp, int msecs)
{
        return (mevent_update(evp, UPDATE_TIMER, msecs));
}

static int
mevent_delete_event(struct mevent *evp, int closefd)
{
        mevent_qlock();

        /*
         * Place the entry onto the changed list if not already there, and
         * mark as to be deleted.
         */
        if (evp->me_cq == 0) {
                evp->me_cq = 1;
                LIST_REMOVE(evp, me_list);
                LIST_INSERT_HEAD(&change_head, evp, me_list);
                mevent_notify();
        }
        evp->me_state = EV_DELETE;

        if (closefd)
                evp->me_closefd = 1;

        mevent_qunlock();

        return (0);
}

int
mevent_delete(struct mevent *evp)
{

        return (mevent_delete_event(evp, 0));
}

int
mevent_delete_close(struct mevent *evp)
{

        return (mevent_delete_event(evp, 1));
}

static void
mevent_set_name(void)
{

        pthread_set_name_np(mevent_tid, "mevent");
}

void
mevent_dispatch(void)
{
        struct kevent changelist[MEVENT_MAX];
        struct kevent eventlist[MEVENT_MAX];
        struct mevent *pipev;
        int numev;
        int ret;
#ifndef WITHOUT_CAPSICUM
        cap_rights_t rights;
#endif

        mevent_tid = pthread_self();
        mevent_set_name();

        pthread_once(&mevent_once, mevent_init);

        /*
         * Open the pipe that will be used for other threads to force
         * the blocking kqueue call to exit by writing to it. Set the
         * descriptor to non-blocking.
         */
        ret = pipe(mevent_pipefd);
        if (ret < 0) {
                perror("pipe");
                exit(BHYVE_EXIT_ERROR);
        }

#ifndef WITHOUT_CAPSICUM
        cap_rights_init(&rights, CAP_EVENT, CAP_READ, CAP_WRITE);
        if (caph_rights_limit(mevent_pipefd[0], &rights) == -1)
                errx(EX_OSERR, "Unable to apply rights for sandbox");
        if (caph_rights_limit(mevent_pipefd[1], &rights) == -1)
                errx(EX_OSERR, "Unable to apply rights for sandbox");
#endif

        /*
         * Add internal event handler for the pipe write fd
         */
        pipev = mevent_add(mevent_pipefd[0], EVF_READ, mevent_pipe_read, NULL);
        assert(pipev != NULL);

        for (;;) {
                /*
                 * Build changelist if required.
                 * XXX the changelist can be put into the blocking call
                 * to eliminate the extra syscall. Currently better for
                 * debug.
                 */
                numev = mevent_build(changelist);
                if (numev) {
                        ret = kevent(mfd, changelist, numev, NULL, 0, NULL);
                        if (ret == -1) {
                                perror("Error return from kevent change");
                        }
                }

                /*
                 * Block awaiting events
                 */
                ret = kevent(mfd, NULL, 0, eventlist, MEVENT_MAX, NULL);
                if (ret == -1 && errno != EINTR) {
                        perror("Error return from kevent monitor");
                }

                /*
                 * Handle reported events
                 */
                mevent_handle(eventlist, ret);
        }
}