/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 1999,2000,2001 Jonathan Lemon <jlemon@FreeBSD.org>
 * Copyright 2004 John-Mark Gurney <jmg@FreeBSD.org>
 * Copyright (c) 2009 Apple, 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 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 "opt_ktrace.h"
#include "opt_kqueue.h"

#ifdef COMPAT_FREEBSD11
#define _WANT_FREEBSD11_KEVENT
#endif

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/capsicum.h>
#include <sys/kernel.h>
#include <sys/limits.h>
#include <sys/lock.h>
#include <sys/mutex.h>
#include <sys/proc.h>
#include <sys/malloc.h>
#include <sys/unistd.h>
#include <sys/file.h>
#include <sys/filedesc.h>
#include <sys/filio.h>
#include <sys/fcntl.h>
#include <sys/jail.h>
#include <sys/jaildesc.h>
#include <sys/kthread.h>
#include <sys/selinfo.h>
#include <sys/queue.h>
#include <sys/event.h>
#include <sys/eventvar.h>
#include <sys/poll.h>
#include <sys/protosw.h>
#include <sys/resourcevar.h>
#include <sys/sbuf.h>
#include <sys/sigio.h>
#include <sys/signalvar.h>
#include <sys/socket.h>
#include <sys/socketvar.h>
#include <sys/stat.h>
#include <sys/sysctl.h>
#include <sys/sysent.h>
#include <sys/sysproto.h>
#include <sys/syscallsubr.h>
#include <sys/taskqueue.h>
#include <sys/uio.h>
#include <sys/user.h>
#ifdef KTRACE
#include <sys/ktrace.h>
#endif
#include <machine/atomic.h>
#ifdef COMPAT_FREEBSD32
#include <compat/freebsd32/freebsd32.h>
#include <compat/freebsd32/freebsd32_util.h>
#endif

#include <vm/uma.h>

static MALLOC_DEFINE(M_KQUEUE, "kqueue", "memory for kqueue system");

/*
 * This lock is used if multiple kq locks are required.  This possibly
 * should be made into a per proc lock.
 */
static struct mtx       kq_global;
MTX_SYSINIT(kq_global, &kq_global, "kqueue order", MTX_DEF);
#define KQ_GLOBAL_LOCK(lck, haslck)     do {    \
        if (!haslck)                            \
                mtx_lock(lck);                  \
        haslck = 1;                             \
} while (0)
#define KQ_GLOBAL_UNLOCK(lck, haslck)   do {    \
        if (haslck)                             \
                mtx_unlock(lck);                        \
        haslck = 0;                             \
} while (0)

TASKQUEUE_DEFINE_THREAD(kqueue_ctx);

static int      kevent_copyout(void *arg, struct kevent *kevp, int count);
static int      kevent_copyin(void *arg, struct kevent *kevp, int count);
static int      kqueue_register(struct kqueue *kq, struct kevent *kev,
                    struct thread *td, int mflag);
static int      kqueue_acquire(struct file *fp, struct kqueue **kqp);
static void     kqueue_release(struct kqueue *kq, int locked);
static void     kqueue_destroy(struct kqueue *kq);
static void     kqueue_drain(struct kqueue *kq, struct thread *td);
static int      kqueue_expand(struct kqueue *kq, const struct filterops *fops,
                    uintptr_t ident, int mflag);
static void     kqueue_task(void *arg, int pending);
static int      kqueue_scan(struct kqueue *kq, int maxevents,
                    struct kevent_copyops *k_ops,
                    const struct timespec *timeout,
                    struct kevent *keva, struct thread *td);
static void     kqueue_wakeup(struct kqueue *kq);
static const struct filterops *kqueue_fo_find(int filt);
static void     kqueue_fo_release(int filt);
struct g_kevent_args;
static int      kern_kevent_generic(struct thread *td,
                    struct g_kevent_args *uap,
                    struct kevent_copyops *k_ops, const char *struct_name);

static fo_ioctl_t       kqueue_ioctl;
static fo_poll_t        kqueue_poll;
static fo_kqfilter_t    kqueue_kqfilter;
static fo_stat_t        kqueue_stat;
static fo_close_t       kqueue_close;
static fo_fill_kinfo_t  kqueue_fill_kinfo;
static fo_fork_t        kqueue_fork;

static const struct fileops kqueueops = {
        .fo_read = invfo_rdwr,
        .fo_write = invfo_rdwr,
        .fo_truncate = invfo_truncate,
        .fo_ioctl = kqueue_ioctl,
        .fo_poll = kqueue_poll,
        .fo_kqfilter = kqueue_kqfilter,
        .fo_stat = kqueue_stat,
        .fo_close = kqueue_close,
        .fo_chmod = invfo_chmod,
        .fo_chown = invfo_chown,
        .fo_sendfile = invfo_sendfile,
        .fo_cmp = file_kcmp_generic,
        .fo_fork = kqueue_fork,
        .fo_fill_kinfo = kqueue_fill_kinfo,
        .fo_flags = DFLAG_FORK,
};

static int      knote_attach(struct knote *kn, struct kqueue *kq);
static void     knote_drop(struct knote *kn, struct thread *td);
static void     knote_drop_detached(struct knote *kn, struct thread *td);
static void     knote_enqueue(struct knote *kn);
static void     knote_dequeue(struct knote *kn);
static void     knote_init(void *);
static struct   knote *knote_alloc(int mflag);
static void     knote_free(struct knote *kn);

static void     filt_kqdetach(struct knote *kn);
static int      filt_kqueue(struct knote *kn, long hint);
static int      filt_procattach(struct knote *kn);
static void     filt_procdetach(struct knote *kn);
static int      filt_proc(struct knote *kn, long hint);
static int      filt_jailattach(struct knote *kn);
static void     filt_jaildetach(struct knote *kn);
static int      filt_jail(struct knote *kn, long hint);
static int      filt_fileattach(struct knote *kn);
static void     filt_timerexpire(void *knx);
static void     filt_timerexpire_l(struct knote *kn, bool proc_locked);
static int      filt_timerattach(struct knote *kn);
static void     filt_timerdetach(struct knote *kn);
static void     filt_timerstart(struct knote *kn, sbintime_t to);
static void     filt_timertouch(struct knote *kn, struct kevent *kev,
                    u_long type);
static int      filt_timercopy(struct knote *kn, struct proc *p1);
static int      filt_timervalidate(struct knote *kn, sbintime_t *to);
static int      filt_timer(struct knote *kn, long hint);
static int      filt_userattach(struct knote *kn);
static void     filt_userdetach(struct knote *kn);
static int      filt_user(struct knote *kn, long hint);
static void     filt_usertouch(struct knote *kn, struct kevent *kev,
                    u_long type);

static const struct filterops file_filtops = {
        .f_isfd = 1,
        .f_attach = filt_fileattach,
        .f_copy = knote_triv_copy,
};
static const struct filterops kqread_filtops = {
        .f_isfd = 1,
        .f_detach = filt_kqdetach,
        .f_event = filt_kqueue,
        .f_copy = knote_triv_copy,
};
/* XXX - move to kern_proc.c?  */
static const struct filterops proc_filtops = {
        .f_isfd = 0,
        .f_attach = filt_procattach,
        .f_detach = filt_procdetach,
        .f_event = filt_proc,
        .f_copy = knote_triv_copy,
};
static const struct filterops jail_filtops = {
        .f_isfd = 0,
        .f_attach = filt_jailattach,
        .f_detach = filt_jaildetach,
        .f_event = filt_jail,
        .f_copy = knote_triv_copy,
};
static const struct filterops timer_filtops = {
        .f_isfd = 0,
        .f_attach = filt_timerattach,
        .f_detach = filt_timerdetach,
        .f_event = filt_timer,
        .f_touch = filt_timertouch,
        .f_copy =  filt_timercopy,
};
static const struct filterops user_filtops = {
        .f_attach = filt_userattach,
        .f_detach = filt_userdetach,
        .f_event = filt_user,
        .f_touch = filt_usertouch,
        .f_copy = knote_triv_copy,
};

static uma_zone_t       knote_zone;
static unsigned int __exclusive_cache_line      kq_ncallouts;
static unsigned int     kq_calloutmax = 4 * 1024;
SYSCTL_UINT(_kern, OID_AUTO, kq_calloutmax, CTLFLAG_RW,
    &kq_calloutmax, 0, "Maximum number of callouts allocated for kqueue");

/* XXX - ensure not influx ? */
#define KNOTE_ACTIVATE(kn, islock) do {                                 \
        if ((islock))                                                   \
                mtx_assert(&(kn)->kn_kq->kq_lock, MA_OWNED);            \
        else                                                            \
                KQ_LOCK((kn)->kn_kq);                                   \
        (kn)->kn_status |= KN_ACTIVE;                                   \
        if (((kn)->kn_status & (KN_QUEUED | KN_DISABLED)) == 0)         \
                knote_enqueue((kn));                                    \
        if (!(islock))                                                  \
                KQ_UNLOCK((kn)->kn_kq);                                 \
} while (0)
#define KQ_LOCK(kq) do {                                                \
        mtx_lock(&(kq)->kq_lock);                                       \
} while (0)
#define KQ_FLUX_WAKEUP(kq) do {                                         \
        if (((kq)->kq_state & KQ_FLUXWAIT) == KQ_FLUXWAIT) {            \
                (kq)->kq_state &= ~KQ_FLUXWAIT;                         \
                wakeup((kq));                                           \
        }                                                               \
} while (0)
#define KQ_UNLOCK_FLUX(kq) do {                                         \
        KQ_FLUX_WAKEUP(kq);                                             \
        mtx_unlock(&(kq)->kq_lock);                                     \
} while (0)
#define KQ_UNLOCK(kq) do {                                              \
        mtx_unlock(&(kq)->kq_lock);                                     \
} while (0)
#define KQ_OWNED(kq) do {                                               \
        mtx_assert(&(kq)->kq_lock, MA_OWNED);                           \
} while (0)
#define KQ_NOTOWNED(kq) do {                                            \
        mtx_assert(&(kq)->kq_lock, MA_NOTOWNED);                        \
} while (0)

static struct knlist *
kn_list_lock(struct knote *kn)
{
        struct knlist *knl;

        knl = kn->kn_knlist;
        if (knl != NULL)
                knl->kl_lock(knl->kl_lockarg);
        return (knl);
}

static void
kn_list_unlock(struct knlist *knl)
{
        bool do_free;

        if (knl == NULL)
                return;
        do_free = knl->kl_autodestroy && knlist_empty(knl);
        knl->kl_unlock(knl->kl_lockarg);
        if (do_free) {
                knlist_destroy(knl);
                free(knl, M_KQUEUE);
        }
}

static bool
kn_in_flux(struct knote *kn)
{

        return (kn->kn_influx > 0);
}

static void
kn_enter_flux(struct knote *kn)
{

        KQ_OWNED(kn->kn_kq);
        MPASS(kn->kn_influx < INT_MAX);
        kn->kn_influx++;
}

static bool
kn_leave_flux(struct knote *kn)
{

        KQ_OWNED(kn->kn_kq);
        MPASS(kn->kn_influx > 0);
        kn->kn_influx--;
        return (kn->kn_influx == 0);
}

#define KNL_ASSERT_LOCK(knl, islocked) do {                             \
        if (islocked)                                                   \
                KNL_ASSERT_LOCKED(knl);                         \
        else                                                            \
                KNL_ASSERT_UNLOCKED(knl);                               \
} while (0)
#ifdef INVARIANTS
#define KNL_ASSERT_LOCKED(knl) do {                                     \
        knl->kl_assert_lock((knl)->kl_lockarg, LA_LOCKED);              \
} while (0)
#define KNL_ASSERT_UNLOCKED(knl) do {                                   \
        knl->kl_assert_lock((knl)->kl_lockarg, LA_UNLOCKED);            \
} while (0)
#else /* !INVARIANTS */
#define KNL_ASSERT_LOCKED(knl) do {} while (0)
#define KNL_ASSERT_UNLOCKED(knl) do {} while (0)
#endif /* INVARIANTS */

#ifndef KN_HASHSIZE
#define KN_HASHSIZE             64              /* XXX should be tunable */
#endif

#define KN_HASH(val, mask)      (((val) ^ (val >> 8)) & (mask))

static int
filt_nullattach(struct knote *kn)
{

        return (ENXIO);
};

static const struct filterops null_filtops = {
        .f_isfd = 0,
        .f_attach = filt_nullattach,
        .f_copy = knote_triv_copy,
};

/* XXX - make SYSINIT to add these, and move into respective modules. */
extern const struct filterops sig_filtops;
extern const struct filterops fs_filtops;

/*
 * Table for all system-defined filters.
 */
static struct mtx       filterops_lock;
MTX_SYSINIT(kqueue_filterops, &filterops_lock, "protect sysfilt_ops", MTX_DEF);
static struct {
        const struct filterops *for_fop;
        int for_nolock;
        int for_refcnt;
} sysfilt_ops[EVFILT_SYSCOUNT] = {
        [~EVFILT_READ] = { &file_filtops, 1 },
        [~EVFILT_WRITE] = { &file_filtops, 1 },
        [~EVFILT_AIO] = { &null_filtops },
        [~EVFILT_VNODE] = { &file_filtops, 1 },
        [~EVFILT_PROC] = { &proc_filtops, 1 },
        [~EVFILT_SIGNAL] = { &sig_filtops, 1 },
        [~EVFILT_TIMER] = { &timer_filtops, 1 },
        [~EVFILT_PROCDESC] = { &file_filtops, 1 },
        [~EVFILT_FS] = { &fs_filtops, 1 },
        [~EVFILT_LIO] = { &null_filtops },
        [~EVFILT_USER] = { &user_filtops, 1 },
        [~EVFILT_SENDFILE] = { &null_filtops },
        [~EVFILT_EMPTY] = { &file_filtops, 1 },
        [~EVFILT_JAIL] = { &jail_filtops, 1 },
        [~EVFILT_JAILDESC] = { &file_filtops, 1 },
};

/*
 * Simple redirection for all cdevsw style objects to call their fo_kqfilter
 * method.
 */
static int
filt_fileattach(struct knote *kn)
{

        return (fo_kqfilter(kn->kn_fp, kn));
}

/*ARGSUSED*/
static int
kqueue_kqfilter(struct file *fp, struct knote *kn)
{
        struct kqueue *kq = kn->kn_fp->f_data;

        if (kn->kn_filter != EVFILT_READ)
                return (EINVAL);

        kn->kn_status |= KN_KQUEUE;
        kn->kn_fop = &kqread_filtops;
        knlist_add(&kq->kq_sel.si_note, kn, 0);

        return (0);
}

static void
filt_kqdetach(struct knote *kn)
{
        struct kqueue *kq = kn->kn_fp->f_data;

        knlist_remove(&kq->kq_sel.si_note, kn, 0);
}

/*ARGSUSED*/
static int
filt_kqueue(struct knote *kn, long hint)
{
        struct kqueue *kq = kn->kn_fp->f_data;

        kn->kn_data = kq->kq_count;
        return (kn->kn_data > 0);
}

/* XXX - move to kern_proc.c?  */
static int
filt_procattach(struct knote *kn)
{
        struct proc *p;
        int error;
        bool exiting, immediate;

        exiting = immediate = false;
        if (kn->kn_sfflags & NOTE_EXIT)
                p = pfind_any(kn->kn_id);
        else
                p = pfind(kn->kn_id);
        if (p == NULL)
                return (ESRCH);
        if (p->p_flag & P_WEXIT)
                exiting = true;

        if ((error = p_cansee(curthread, p))) {
                PROC_UNLOCK(p);
                return (error);
        }

        kn->kn_ptr.p_proc = p;
        kn->kn_flags |= EV_CLEAR;               /* automatically set */

        /*
         * Internal flag indicating registration done by kernel for the
         * purposes of getting a NOTE_CHILD notification.
         */
        if (kn->kn_flags & EV_FLAG2) {
                kn->kn_flags &= ~EV_FLAG2;
                kn->kn_data = kn->kn_sdata;             /* ppid */
                kn->kn_fflags = NOTE_CHILD;
                kn->kn_sfflags &= ~(NOTE_EXIT | NOTE_EXEC | NOTE_FORK);
                immediate = true; /* Force immediate activation of child note. */
        }
        /*
         * Internal flag indicating registration done by kernel (for other than
         * NOTE_CHILD).
         */
        if (kn->kn_flags & EV_FLAG1) {
                kn->kn_flags &= ~EV_FLAG1;
        }

        knlist_add(p->p_klist, kn, 1);

        /*
         * Immediately activate any child notes or, in the case of a zombie
         * target process, exit notes.  The latter is necessary to handle the
         * case where the target process, e.g. a child, dies before the kevent
         * is registered.
         */
        if (immediate || (exiting && filt_proc(kn, NOTE_EXIT)))
                KNOTE_ACTIVATE(kn, 0);

        PROC_UNLOCK(p);

        return (0);
}

/*
 * The knote may be attached to a different process, which may exit,
 * leaving nothing for the knote to be attached to.  So when the process
 * exits, the knote is marked as DETACHED and also flagged as ONESHOT so
 * it will be deleted when read out.  However, as part of the knote deletion,
 * this routine is called, so a check is needed to avoid actually performing
 * a detach, because the original process does not exist any more.
 */
/* XXX - move to kern_proc.c?  */
static void
filt_procdetach(struct knote *kn)
{

        knlist_remove(kn->kn_knlist, kn, 0);
        kn->kn_ptr.p_proc = NULL;
}

/* XXX - move to kern_proc.c?  */
static int
filt_proc(struct knote *kn, long hint)
{
        struct proc *p;
        u_int event;

        p = kn->kn_ptr.p_proc;
        if (p == NULL) /* already activated, from attach filter */
                return (0);

        /* Mask off extra data. */
        event = (u_int)hint & NOTE_PCTRLMASK;

        /* If the user is interested in this event, record it. */
        if (kn->kn_sfflags & event)
                kn->kn_fflags |= event;

        /* Process is gone, so flag the event as finished. */
        if (event == NOTE_EXIT) {
                kn->kn_flags |= EV_EOF | EV_ONESHOT;
                kn->kn_ptr.p_proc = NULL;
                if (kn->kn_fflags & NOTE_EXIT)
                        kn->kn_data = KW_EXITCODE(p->p_xexit, p->p_xsig);
                if (kn->kn_fflags == 0)
                        kn->kn_flags |= EV_DROP;
                return (1);
        }

        return (kn->kn_fflags != 0);
}

/*
 * Called when the process forked. It mostly does the same as the
 * knote(), activating all knotes registered to be activated when the
 * process forked. Additionally, for each knote attached to the
 * parent, check whether user wants to track the new process. If so
 * attach a new knote to it, and immediately report an event with the
 * child's pid.
 */
void
knote_fork(struct knlist *list, int pid)
{
        struct kqueue *kq;
        struct knote *kn;
        struct kevent kev;
        int error;

        MPASS(list != NULL);
        KNL_ASSERT_LOCKED(list);
        if (SLIST_EMPTY(&list->kl_list))
                return;

        memset(&kev, 0, sizeof(kev));
        SLIST_FOREACH(kn, &list->kl_list, kn_selnext) {
                kq = kn->kn_kq;
                KQ_LOCK(kq);
                if (kn_in_flux(kn) && (kn->kn_status & KN_SCAN) == 0) {
                        KQ_UNLOCK(kq);
                        continue;
                }

                /*
                 * The same as knote(), activate the event.
                 */
                if ((kn->kn_sfflags & NOTE_TRACK) == 0) {
                        if (kn->kn_fop->f_event(kn, NOTE_FORK))
                                KNOTE_ACTIVATE(kn, 1);
                        KQ_UNLOCK(kq);
                        continue;
                }

                /*
                 * The NOTE_TRACK case. In addition to the activation
                 * of the event, we need to register new events to
                 * track the child. Drop the locks in preparation for
                 * the call to kqueue_register().
                 */
                kn_enter_flux(kn);
                KQ_UNLOCK(kq);
                list->kl_unlock(list->kl_lockarg);

                /*
                 * Activate existing knote and register tracking knotes with
                 * new process.
                 *
                 * First register a knote to get just the child notice. This
                 * must be a separate note from a potential NOTE_EXIT
                 * notification since both NOTE_CHILD and NOTE_EXIT are defined
                 * to use the data field (in conflicting ways).
                 */
                kev.ident = pid;
                kev.filter = kn->kn_filter;
                kev.flags = kn->kn_flags | EV_ADD | EV_ENABLE | EV_ONESHOT |
                    EV_FLAG2;
                kev.fflags = kn->kn_sfflags;
                kev.data = kn->kn_id;           /* parent */
                kev.udata = kn->kn_kevent.udata;/* preserve udata */
                error = kqueue_register(kq, &kev, NULL, M_NOWAIT);
                if (error)
                        kn->kn_fflags |= NOTE_TRACKERR;

                /*
                 * Then register another knote to track other potential events
                 * from the new process.
                 */
                kev.ident = pid;
                kev.filter = kn->kn_filter;
                kev.flags = kn->kn_flags | EV_ADD | EV_ENABLE | EV_FLAG1;
                kev.fflags = kn->kn_sfflags;
                kev.data = kn->kn_id;           /* parent */
                kev.udata = kn->kn_kevent.udata;/* preserve udata */
                error = kqueue_register(kq, &kev, NULL, M_NOWAIT);

                /*
                 * Serialize updates to the kn_kevent fields with threads
                 * scanning the queue.
                 */
                list->kl_lock(list->kl_lockarg);
                if (error)
                        kn->kn_fflags |= NOTE_TRACKERR;
                if (kn->kn_fop->f_event(kn, NOTE_FORK)) {
                        KQ_LOCK(kq);
                        KNOTE_ACTIVATE(kn, 1);
                } else {
                        KQ_LOCK(kq);
                }
                kn_leave_flux(kn);
                KQ_UNLOCK_FLUX(kq);
        }
}

int
filt_jailattach(struct knote *kn)
{
        struct prison *pr;

        if (kn->kn_id == 0) {
                /* Let jid=0 watch the current prison (including prison0). */
                pr = curthread->td_ucred->cr_prison;
                mtx_lock(&pr->pr_mtx);
        } else {
                sx_slock(&allprison_lock);
                pr = prison_find_child(curthread->td_ucred->cr_prison,
                    kn->kn_id);
                sx_sunlock(&allprison_lock);
                if (pr == NULL)
                        return (ENOENT);
                if (!prison_isalive(pr)) {
                        mtx_unlock(&pr->pr_mtx);
                        return (ENOENT);
                }
        }
        kn->kn_ptr.p_prison = pr;
        kn->kn_flags |= EV_CLEAR;
        knlist_add(pr->pr_klist, kn, 1);
        mtx_unlock(&pr->pr_mtx);
        return (0);
}

void
filt_jaildetach(struct knote *kn)
{
        if (kn->kn_ptr.p_prison != NULL) {
                knlist_remove(kn->kn_knlist, kn, 0);
                kn->kn_ptr.p_prison = NULL;
        } else
                kn->kn_status |= KN_DETACHED;
}

int
filt_jail(struct knote *kn, long hint)
{
        struct prison *pr;
        u_int event;

        pr = kn->kn_ptr.p_prison;
        if (pr == NULL) /* already activated, from attach filter */
                return (0);

        /*
         * Mask off extra data.  In the NOTE_JAIL_CHILD case, that's
         * everything except the NOTE_JAIL_CHILD bit itself, since a
         * JID is any positive integer.
         */
        event = ((u_int)hint & NOTE_JAIL_CHILD) ? NOTE_JAIL_CHILD :
            (u_int)hint & NOTE_JAIL_CTRLMASK;

        /* If the user is interested in this event, record it. */
        if (kn->kn_sfflags & event) {
                kn->kn_fflags |= event;
                /* Report the created jail id or attached process id. */
                if (event == NOTE_JAIL_CHILD || event == NOTE_JAIL_ATTACH) {
                        if (kn->kn_data != 0)
                                kn->kn_fflags |= NOTE_JAIL_MULTI;
                        kn->kn_data = (kn->kn_fflags & NOTE_JAIL_MULTI) ? 0U :
                            (u_int)hint & ~event;
                }
        }

        /* Prison is gone, so flag the event as finished. */
        if (event == NOTE_JAIL_REMOVE) {
                kn->kn_flags |= EV_EOF | EV_ONESHOT;
                kn->kn_ptr.p_prison = NULL;
                if (kn->kn_fflags == 0)
                        kn->kn_flags |= EV_DROP;
                return (1);
        }

        return (kn->kn_fflags != 0);
}

/*
 * XXX: EVFILT_TIMER should perhaps live in kern_time.c beside the
 * interval timer support code.
 */

#define NOTE_TIMER_PRECMASK                                             \
    (NOTE_SECONDS | NOTE_MSECONDS | NOTE_USECONDS | NOTE_NSECONDS)

static sbintime_t
timer2sbintime(int64_t data, unsigned int flags)
{
        int64_t secs;

        /*
         * Macros for converting to the fractional second portion of an
         * sbintime_t using 64bit multiplication to improve precision.
         */
#define NS_TO_SBT(ns) (((ns) * (((uint64_t)1 << 63) / 500000000)) >> 32)
#define US_TO_SBT(us) (((us) * (((uint64_t)1 << 63) / 500000)) >> 32)
#define MS_TO_SBT(ms) (((ms) * (((uint64_t)1 << 63) / 500)) >> 32)
        switch (flags & NOTE_TIMER_PRECMASK) {
        case NOTE_SECONDS:
#ifdef __LP64__
                if (data > (SBT_MAX / SBT_1S))
                        return (SBT_MAX);
#endif
                return ((sbintime_t)data << 32);
        case NOTE_MSECONDS: /* FALLTHROUGH */
        case 0:
                if (data >= 1000) {
                        secs = data / 1000;
#ifdef __LP64__
                        if (secs > (SBT_MAX / SBT_1S))
                                return (SBT_MAX);
#endif
                        return (secs << 32 | MS_TO_SBT(data % 1000));
                }
                return (MS_TO_SBT(data));
        case NOTE_USECONDS:
                if (data >= 1000000) {
                        secs = data / 1000000;
#ifdef __LP64__
                        if (secs > (SBT_MAX / SBT_1S))
                                return (SBT_MAX);
#endif
                        return (secs << 32 | US_TO_SBT(data % 1000000));
                }
                return (US_TO_SBT(data));
        case NOTE_NSECONDS:
                if (data >= 1000000000) {
                        secs = data / 1000000000;
#ifdef __LP64__
                        if (secs > (SBT_MAX / SBT_1S))
                                return (SBT_MAX);
#endif
                        return (secs << 32 | NS_TO_SBT(data % 1000000000));
                }
                return (NS_TO_SBT(data));
        default:
                break;
        }
        return (-1);
}

struct kq_timer_cb_data {
        struct callout c;
        struct proc *p;
        struct knote *kn;
        int cpuid;
        int flags;
        TAILQ_ENTRY(kq_timer_cb_data) link;
        sbintime_t next;        /* next timer event fires at */
        sbintime_t to;          /* precalculated timer period, 0 for abs */
};

#define KQ_TIMER_CB_ENQUEUED    0x01

static void
kqtimer_sched_callout(struct kq_timer_cb_data *kc)
{
        callout_reset_sbt_on(&kc->c, kc->next, 0, filt_timerexpire, kc->kn,
            kc->cpuid, C_ABSOLUTE);
}

void
kqtimer_proc_continue(struct proc *p)
{
        struct kq_timer_cb_data *kc, *kc1;
        sbintime_t now;

        PROC_LOCK_ASSERT(p, MA_OWNED);

        now = sbinuptime();
        TAILQ_FOREACH_SAFE(kc, &p->p_kqtim_stop, link, kc1) {
                TAILQ_REMOVE(&p->p_kqtim_stop, kc, link);
                kc->flags &= ~KQ_TIMER_CB_ENQUEUED;
                if (kc->next <= now)
                        filt_timerexpire_l(kc->kn, true);
                else
                        kqtimer_sched_callout(kc);
        }
}

static void
filt_timerexpire_l(struct knote *kn, bool proc_locked)
{
        struct kq_timer_cb_data *kc;
        struct proc *p;
        uint64_t delta;
        sbintime_t now;

        kc = kn->kn_ptr.p_v;

        if ((kn->kn_flags & EV_ONESHOT) != 0 || kc->to == 0) {
                kn->kn_data++;
                KNOTE_ACTIVATE(kn, 0);
                return;
        }

        now = sbinuptime();
        if (now >= kc->next) {
                delta = (now - kc->next) / kc->to;
                if (delta == 0)
                        delta = 1;
                kn->kn_data += delta;
                kc->next += delta * kc->to;
                if (now >= kc->next)    /* overflow */
                        kc->next = now + kc->to;
                KNOTE_ACTIVATE(kn, 0);  /* XXX - handle locking */
        }

        /*
         * Initial check for stopped kc->p is racy.  It is fine to
         * miss the set of the stop flags, at worst we would schedule
         * one more callout.  On the other hand, it is not fine to not
         * schedule when we we missed clearing of the flags, we
         * recheck them under the lock and observe consistent state.
         */
        p = kc->p;
        if (P_SHOULDSTOP(p) || P_KILLED(p)) {
                if (!proc_locked)
                        PROC_LOCK(p);
                if (P_SHOULDSTOP(p) || P_KILLED(p)) {
                        if ((kc->flags & KQ_TIMER_CB_ENQUEUED) == 0) {
                                /*
                                 * Insert into head so that
                                 * kqtimer_proc_continue() does not
                                 * iterate into us again.
                                 */
                                kc->flags |= KQ_TIMER_CB_ENQUEUED;
                                TAILQ_INSERT_HEAD(&p->p_kqtim_stop, kc, link);
                        }
                        if (!proc_locked)
                                PROC_UNLOCK(p);
                        return;
                }
                if (!proc_locked)
                        PROC_UNLOCK(p);
        }
        kqtimer_sched_callout(kc);
}

static void
filt_timerexpire(void *knx)
{
        filt_timerexpire_l(knx, false);
}

/*
 * data contains amount of time to sleep
 */
static int
filt_timervalidate(struct knote *kn, sbintime_t *to)
{
        struct bintime bt;
        sbintime_t sbt;

        if (kn->kn_sdata < 0)
                return (EINVAL);
        if (kn->kn_sdata == 0 && (kn->kn_flags & EV_ONESHOT) == 0)
                kn->kn_sdata = 1;
        /*
         * The only fflags values supported are the timer unit
         * (precision) and the absolute time indicator.
         */
        if ((kn->kn_sfflags & ~(NOTE_TIMER_PRECMASK | NOTE_ABSTIME)) != 0)
                return (EINVAL);

        *to = timer2sbintime(kn->kn_sdata, kn->kn_sfflags);
        if (*to < 0)
                return (EINVAL);
        if ((kn->kn_sfflags & NOTE_ABSTIME) != 0) {
                getboottimebin(&bt);
                sbt = bttosbt(bt);
                *to = MAX(0, *to - sbt);
        }
        return (0);
}

static int
filt_timerattach(struct knote *kn)
{
        struct kq_timer_cb_data *kc;
        sbintime_t to;
        int error;

        to = -1;
        error = filt_timervalidate(kn, &to);
        if (error != 0)
                return (error);
        KASSERT(to > 0 || (kn->kn_flags & EV_ONESHOT) != 0 ||
            (kn->kn_sfflags & NOTE_ABSTIME) != 0,
            ("%s: periodic timer has a calculated zero timeout", __func__));
        KASSERT(to >= 0,
            ("%s: timer has a calculated negative timeout", __func__));

        if (atomic_fetchadd_int(&kq_ncallouts, 1) + 1 > kq_calloutmax) {
                atomic_subtract_int(&kq_ncallouts, 1);
                return (ENOMEM);
        }

        if ((kn->kn_sfflags & NOTE_ABSTIME) == 0)
                kn->kn_flags |= EV_CLEAR;       /* automatically set */
        kn->kn_status &= ~KN_DETACHED;          /* knlist_add clears it */
        kn->kn_ptr.p_v = kc = malloc(sizeof(*kc), M_KQUEUE, M_WAITOK);
        kc->kn = kn;
        kc->p = curproc;
        kc->cpuid = PCPU_GET(cpuid);
        kc->flags = 0;
        callout_init(&kc->c, 1);
        filt_timerstart(kn, to);

        return (0);
}

static int
filt_timercopy(struct knote *kn, struct proc *p)
{
        struct kq_timer_cb_data *kc_src, *kc;

        if (atomic_fetchadd_int(&kq_ncallouts, 1) + 1 > kq_calloutmax) {
                atomic_subtract_int(&kq_ncallouts, 1);
                return (ENOMEM);
        }

        kn->kn_status &= ~KN_DETACHED;
        kc_src = kn->kn_ptr.p_v;
        kn->kn_ptr.p_v = kc = malloc(sizeof(*kc), M_KQUEUE, M_WAITOK);
        kc->kn = kn;
        kc->p = p;
        kc->flags = kc_src->flags & ~KQ_TIMER_CB_ENQUEUED;
        kc->next = kc_src->next;
        kc->to = kc_src->to;
        kc->cpuid = PCPU_GET(cpuid);
        callout_init(&kc->c, 1);
        kqtimer_sched_callout(kc);
        return (0);
}

static void
filt_timerstart(struct knote *kn, sbintime_t to)
{
        struct kq_timer_cb_data *kc;

        kc = kn->kn_ptr.p_v;
        if ((kn->kn_sfflags & NOTE_ABSTIME) != 0) {
                kc->next = to;
                kc->to = 0;
        } else {
                kc->next = to + sbinuptime();
                kc->to = to;
        }
        kqtimer_sched_callout(kc);
}

static void
filt_timerdetach(struct knote *kn)
{
        struct kq_timer_cb_data *kc;
        unsigned int old __unused;
        bool pending;

        kc = kn->kn_ptr.p_v;
        do {
                callout_drain(&kc->c);

                /*
                 * kqtimer_proc_continue() might have rescheduled this callout.
                 * Double-check, using the process mutex as an interlock.
                 */
                PROC_LOCK(kc->p);
                if ((kc->flags & KQ_TIMER_CB_ENQUEUED) != 0) {
                        kc->flags &= ~KQ_TIMER_CB_ENQUEUED;
                        TAILQ_REMOVE(&kc->p->p_kqtim_stop, kc, link);
                }
                pending = callout_pending(&kc->c);
                PROC_UNLOCK(kc->p);
        } while (pending);
        free(kc, M_KQUEUE);
        old = atomic_fetchadd_int(&kq_ncallouts, -1);
        KASSERT(old > 0, ("Number of callouts cannot become negative"));
        kn->kn_status |= KN_DETACHED;   /* knlist_remove sets it */
}

static void
filt_timertouch(struct knote *kn, struct kevent *kev, u_long type)
{
        struct kq_timer_cb_data *kc;
        struct kqueue *kq;
        sbintime_t to;
        int error;

        switch (type) {
        case EVENT_REGISTER:
                /* Handle re-added timers that update data/fflags */
                if (kev->flags & EV_ADD) {
                        kc = kn->kn_ptr.p_v;

                        /* Drain any existing callout. */
                        callout_drain(&kc->c);

                        /* Throw away any existing undelivered record
                         * of the timer expiration. This is done under
                         * the presumption that if a process is
                         * re-adding this timer with new parameters,
                         * it is no longer interested in what may have
                         * happened under the old parameters. If it is
                         * interested, it can wait for the expiration,
                         * delete the old timer definition, and then
                         * add the new one.
                         *
                         * This has to be done while the kq is locked:
                         *   - if enqueued, dequeue
                         *   - make it no longer active
                         *   - clear the count of expiration events
                         */
                        kq = kn->kn_kq;
                        KQ_LOCK(kq);
                        if (kn->kn_status & KN_QUEUED)
                                knote_dequeue(kn);

                        kn->kn_status &= ~KN_ACTIVE;
                        kn->kn_data = 0;
                        KQ_UNLOCK(kq);

                        /* Reschedule timer based on new data/fflags */
                        kn->kn_sfflags = kev->fflags;
                        kn->kn_sdata = kev->data;
                        error = filt_timervalidate(kn, &to);
                        if (error != 0) {
                                kn->kn_flags |= EV_ERROR;
                                kn->kn_data = error;
                        } else
                                filt_timerstart(kn, to);
                }
                break;

        case EVENT_PROCESS:
                *kev = kn->kn_kevent;
                if (kn->kn_flags & EV_CLEAR) {
                        kn->kn_data = 0;
                        kn->kn_fflags = 0;
                }
                break;

        default:
                panic("filt_timertouch() - invalid type (%ld)", type);
                break;
        }
}

static int
filt_timer(struct knote *kn, long hint)
{

        return (kn->kn_data != 0);
}

static int
filt_userattach(struct knote *kn)
{

        /*
         * EVFILT_USER knotes are not attached to anything in the kernel.
         */
        kn->kn_hook = NULL;
        if (kn->kn_fflags & NOTE_TRIGGER)
                kn->kn_hookid = 1;
        else
                kn->kn_hookid = 0;
        return (0);
}

static void
filt_userdetach(__unused struct knote *kn)
{

        /*
         * EVFILT_USER knotes are not attached to anything in the kernel.
         */
}

static int
filt_user(struct knote *kn, __unused long hint)
{

        return (kn->kn_hookid);
}

static void
filt_usertouch(struct knote *kn, struct kevent *kev, u_long type)
{
        u_int ffctrl;

        switch (type) {
        case EVENT_REGISTER:
                if (kev->fflags & NOTE_TRIGGER)
                        kn->kn_hookid = 1;

                ffctrl = kev->fflags & NOTE_FFCTRLMASK;
                kev->fflags &= NOTE_FFLAGSMASK;
                switch (ffctrl) {
                case NOTE_FFNOP:
                        break;

                case NOTE_FFAND:
                        kn->kn_sfflags &= kev->fflags;
                        break;

                case NOTE_FFOR:
                        kn->kn_sfflags |= kev->fflags;
                        break;

                case NOTE_FFCOPY:
                        kn->kn_sfflags = kev->fflags;
                        break;

                default:
                        /* XXX Return error? */
                        break;
                }
                kn->kn_sdata = kev->data;
                if (kev->flags & EV_CLEAR) {
                        kn->kn_hookid = 0;
                        kn->kn_data = 0;
                        kn->kn_fflags = 0;
                }
                break;

        case EVENT_PROCESS:
                *kev = kn->kn_kevent;
                kev->fflags = kn->kn_sfflags;
                kev->data = kn->kn_sdata;
                if (kn->kn_flags & EV_CLEAR) {
                        kn->kn_hookid = 0;
                        kn->kn_data = 0;
                        kn->kn_fflags = 0;
                }
                break;

        default:
                panic("filt_usertouch() - invalid type (%ld)", type);
                break;
        }
}

int
sys_kqueue(struct thread *td, struct kqueue_args *uap)
{

        return (kern_kqueue(td, 0, false, NULL));
}

int
sys_kqueuex(struct thread *td, struct kqueuex_args *uap)
{
        int flags;

        if ((uap->flags & ~(KQUEUE_CLOEXEC | KQUEUE_CPONFORK)) != 0)
                return (EINVAL);
        flags = 0;
        if ((uap->flags & KQUEUE_CLOEXEC) != 0)
                flags |= O_CLOEXEC;
        return (kern_kqueue(td, flags, (uap->flags & KQUEUE_CPONFORK) != 0,
            NULL));
}

static void
kqueue_init(struct kqueue *kq, bool cponfork)
{

        mtx_init(&kq->kq_lock, "kqueue", NULL, MTX_DEF | MTX_DUPOK);
        TAILQ_INIT(&kq->kq_head);
        knlist_init_mtx(&kq->kq_sel.si_note, &kq->kq_lock);
        TASK_INIT(&kq->kq_task, 0, kqueue_task, kq);
        if (cponfork)
                kq->kq_state |= KQ_CPONFORK;
}

static int
kern_kqueue_alloc(struct thread *td, struct filedesc *fdp, int *fdip,
    struct file **fpp, int flags, struct filecaps *fcaps, bool cponfork,
    struct kqueue **kqp)
{
        struct ucred *cred;
        struct kqueue *kq;
        int error;

        cred = td->td_ucred;
        if (!chgkqcnt(cred->cr_ruidinfo, 1, lim_cur(td, RLIMIT_KQUEUES)))
                return (ENOMEM);

        error = fdip != NULL ? falloc_caps(td, fpp, fdip, flags, fcaps) :
            _falloc_noinstall(td, fpp, 1);
        if (error != 0) {
                chgkqcnt(cred->cr_ruidinfo, -1, 0);
                return (error);
        }

        /* An extra reference on `fp' has been held for us by falloc(). */
        kq = malloc(sizeof(*kq), M_KQUEUE, M_WAITOK | M_ZERO);
        kqueue_init(kq, cponfork);
        kq->kq_fdp = fdp;
        kq->kq_cred = crhold(cred);

        if (fdip != NULL)
                FILEDESC_XLOCK(fdp);
        TAILQ_INSERT_HEAD(&fdp->fd_kqlist, kq, kq_list);
        if (fdip != NULL)
                FILEDESC_XUNLOCK(fdp);

        finit(*fpp, FREAD | FWRITE, DTYPE_KQUEUE, kq, &kqueueops);
        *kqp = kq;
        return (0);
}

int
kern_kqueue(struct thread *td, int flags, bool cponfork, struct filecaps *fcaps)
{
        struct kqueue *kq;
        struct file *fp;
        int fd, error;

        error = kern_kqueue_alloc(td, td->td_proc->p_fd, &fd, &fp, flags,
            fcaps, cponfork, &kq);
        if (error != 0)
                return (error);

        fdrop(fp, td);

        td->td_retval[0] = fd;
        return (0);
}

struct g_kevent_args {
        int     fd;
        const void *changelist;
        int     nchanges;
        void    *eventlist;
        int     nevents;
        const struct timespec *timeout;
};

int
sys_kevent(struct thread *td, struct kevent_args *uap)
{
        struct kevent_copyops k_ops = {
                .arg = uap,
                .k_copyout = kevent_copyout,
                .k_copyin = kevent_copyin,
                .kevent_size = sizeof(struct kevent),
        };
        struct g_kevent_args gk_args = {
                .fd = uap->fd,
                .changelist = uap->changelist,
                .nchanges = uap->nchanges,
                .eventlist = uap->eventlist,
                .nevents = uap->nevents,
                .timeout = uap->timeout,
        };

        return (kern_kevent_generic(td, &gk_args, &k_ops, "kevent"));
}

static int
kern_kevent_generic(struct thread *td, struct g_kevent_args *uap,
    struct kevent_copyops *k_ops, const char *struct_name)
{
        struct timespec ts, *tsp;
#ifdef KTRACE
        struct kevent *eventlist = uap->eventlist;
#endif
        int error;

        if (uap->timeout != NULL) {
                error = copyin(uap->timeout, &ts, sizeof(ts));
                if (error)
                        return (error);
                tsp = &ts;
        } else
                tsp = NULL;

#ifdef KTRACE
        if (KTRPOINT(td, KTR_STRUCT_ARRAY))
                ktrstructarray(struct_name, UIO_USERSPACE, uap->changelist,
                    uap->nchanges, k_ops->kevent_size);
#endif

        error = kern_kevent(td, uap->fd, uap->nchanges, uap->nevents,
            k_ops, tsp);

#ifdef KTRACE
        if (error == 0 && KTRPOINT(td, KTR_STRUCT_ARRAY))
                ktrstructarray(struct_name, UIO_USERSPACE, eventlist,
                    td->td_retval[0], k_ops->kevent_size);
#endif

        return (error);
}

/*
 * Copy 'count' items into the destination list pointed to by uap->eventlist.
 */
static int
kevent_copyout(void *arg, struct kevent *kevp, int count)
{
        struct kevent_args *uap;
        int error;

        KASSERT(count <= KQ_NEVENTS, ("count (%d) > KQ_NEVENTS", count));
        uap = (struct kevent_args *)arg;

        error = copyout(kevp, uap->eventlist, count * sizeof *kevp);
        if (error == 0)
                uap->eventlist += count;
        return (error);
}

/*
 * Copy 'count' items from the list pointed to by uap->changelist.
 */
static int
kevent_copyin(void *arg, struct kevent *kevp, int count)
{
        struct kevent_args *uap;
        int error;

        KASSERT(count <= KQ_NEVENTS, ("count (%d) > KQ_NEVENTS", count));
        uap = (struct kevent_args *)arg;

        error = copyin(uap->changelist, kevp, count * sizeof *kevp);
        if (error == 0)
                uap->changelist += count;
        return (error);
}

#ifdef COMPAT_FREEBSD11
static int
kevent11_copyout(void *arg, struct kevent *kevp, int count)
{
        struct freebsd11_kevent_args *uap;
        struct freebsd11_kevent kev11;
        int error, i;

        KASSERT(count <= KQ_NEVENTS, ("count (%d) > KQ_NEVENTS", count));
        uap = (struct freebsd11_kevent_args *)arg;

        for (i = 0; i < count; i++) {
                kev11.ident = kevp->ident;
                kev11.filter = kevp->filter;
                kev11.flags = kevp->flags;
                kev11.fflags = kevp->fflags;
                kev11.data = kevp->data;
                kev11.udata = kevp->udata;
                error = copyout(&kev11, uap->eventlist, sizeof(kev11));
                if (error != 0)
                        break;
                uap->eventlist++;
                kevp++;
        }
        return (error);
}

/*
 * Copy 'count' items from the list pointed to by uap->changelist.
 */
static int
kevent11_copyin(void *arg, struct kevent *kevp, int count)
{
        struct freebsd11_kevent_args *uap;
        struct freebsd11_kevent kev11;
        int error, i;

        KASSERT(count <= KQ_NEVENTS, ("count (%d) > KQ_NEVENTS", count));
        uap = (struct freebsd11_kevent_args *)arg;

        for (i = 0; i < count; i++) {
                error = copyin(uap->changelist, &kev11, sizeof(kev11));
                if (error != 0)
                        break;
                kevp->ident = kev11.ident;
                kevp->filter = kev11.filter;
                kevp->flags = kev11.flags;
                kevp->fflags = kev11.fflags;
                kevp->data = (uintptr_t)kev11.data;
                kevp->udata = kev11.udata;
                bzero(&kevp->ext, sizeof(kevp->ext));
                uap->changelist++;
                kevp++;
        }
        return (error);
}

int
freebsd11_kevent(struct thread *td, struct freebsd11_kevent_args *uap)
{
        struct kevent_copyops k_ops = {
                .arg = uap,
                .k_copyout = kevent11_copyout,
                .k_copyin = kevent11_copyin,
                .kevent_size = sizeof(struct freebsd11_kevent),
        };
        struct g_kevent_args gk_args = {
                .fd = uap->fd,
                .changelist = uap->changelist,
                .nchanges = uap->nchanges,
                .eventlist = uap->eventlist,
                .nevents = uap->nevents,
                .timeout = uap->timeout,
        };

        return (kern_kevent_generic(td, &gk_args, &k_ops, "freebsd11_kevent"));
}
#endif

int
kern_kevent(struct thread *td, int fd, int nchanges, int nevents,
    struct kevent_copyops *k_ops, const struct timespec *timeout)
{
        cap_rights_t rights;
        struct file *fp;
        int error;

        cap_rights_init_zero(&rights);
        if (nchanges > 0)
                cap_rights_set_one(&rights, CAP_KQUEUE_CHANGE);
        if (nevents > 0)
                cap_rights_set_one(&rights, CAP_KQUEUE_EVENT);
        error = fget(td, fd, &rights, &fp);
        if (error != 0)
                return (error);

        error = kern_kevent_fp(td, fp, nchanges, nevents, k_ops, timeout);
        fdrop(fp, td);

        return (error);
}

static int
kqueue_kevent(struct kqueue *kq, struct thread *td, int nchanges, int nevents,
    struct kevent_copyops *k_ops, const struct timespec *timeout)
{
        struct kevent keva[KQ_NEVENTS];
        struct kevent *kevp, *changes;
        int i, n, nerrors, error;

        if (nchanges < 0)
                return (EINVAL);

        nerrors = 0;
        while (nchanges > 0) {
                n = nchanges > KQ_NEVENTS ? KQ_NEVENTS : nchanges;
                error = k_ops->k_copyin(k_ops->arg, keva, n);
                if (error)
                        return (error);
                changes = keva;
                for (i = 0; i < n; i++) {
                        kevp = &changes[i];
                        if (!kevp->filter)
                                continue;
                        kevp->flags &= ~EV_SYSFLAGS;
                        error = kqueue_register(kq, kevp, td, M_WAITOK);
                        if (error || (kevp->flags & EV_RECEIPT)) {
                                if (nevents == 0)
                                        return (error);
                                kevp->flags = EV_ERROR;
                                kevp->data = error;
                                (void)k_ops->k_copyout(k_ops->arg, kevp, 1);
                                nevents--;
                                nerrors++;
                        }
                }
                nchanges -= n;
        }
        if (nerrors) {
                td->td_retval[0] = nerrors;
                return (0);
        }

        return (kqueue_scan(kq, nevents, k_ops, timeout, keva, td));
}

int
kern_kevent_fp(struct thread *td, struct file *fp, int nchanges, int nevents,
    struct kevent_copyops *k_ops, const struct timespec *timeout)
{
        struct kqueue *kq;
        int error;

        error = kqueue_acquire(fp, &kq);
        if (error != 0)
                return (error);
        error = kqueue_kevent(kq, td, nchanges, nevents, k_ops, timeout);
        kqueue_release(kq, 0);
        return (error);
}

/*
 * Performs a kevent() call on a temporarily created kqueue. This can be
 * used to perform one-shot polling, similar to poll() and select().
 */
int
kern_kevent_anonymous(struct thread *td, int nevents,
    struct kevent_copyops *k_ops)
{
        struct kqueue kq = {};
        int error;

        kqueue_init(&kq, false);
        kq.kq_refcnt = 1;
        error = kqueue_kevent(&kq, td, nevents, nevents, k_ops, NULL);
        kqueue_drain(&kq, td);
        kqueue_destroy(&kq);
        return (error);
}

int
kqueue_add_filteropts(int filt, const struct filterops *filtops)
{
        int error;

        error = 0;
        if (filt > 0 || filt + EVFILT_SYSCOUNT < 0) {
                printf(
"trying to add a filterop that is out of range: %d is beyond %d\n",
                    ~filt, EVFILT_SYSCOUNT);
                return EINVAL;
        }
        mtx_lock(&filterops_lock);
        if (sysfilt_ops[~filt].for_fop != &null_filtops &&
            sysfilt_ops[~filt].for_fop != NULL)
                error = EEXIST;
        else {
                sysfilt_ops[~filt].for_fop = filtops;
                sysfilt_ops[~filt].for_refcnt = 0;
        }
        mtx_unlock(&filterops_lock);

        return (error);
}

int
kqueue_del_filteropts(int filt)
{
        int error;

        error = 0;
        if (filt > 0 || filt + EVFILT_SYSCOUNT < 0)
                return EINVAL;

        mtx_lock(&filterops_lock);
        if (sysfilt_ops[~filt].for_fop == &null_filtops ||
            sysfilt_ops[~filt].for_fop == NULL)
                error = EINVAL;
        else if (sysfilt_ops[~filt].for_refcnt != 0)
                error = EBUSY;
        else {
                sysfilt_ops[~filt].for_fop = &null_filtops;
                sysfilt_ops[~filt].for_refcnt = 0;
        }
        mtx_unlock(&filterops_lock);

        return error;
}

static const struct filterops *
kqueue_fo_find(int filt)
{

        if (filt > 0 || filt + EVFILT_SYSCOUNT < 0)
                return NULL;

        if (sysfilt_ops[~filt].for_nolock)
                return sysfilt_ops[~filt].for_fop;

        mtx_lock(&filterops_lock);
        sysfilt_ops[~filt].for_refcnt++;
        if (sysfilt_ops[~filt].for_fop == NULL)
                sysfilt_ops[~filt].for_fop = &null_filtops;
        mtx_unlock(&filterops_lock);

        return sysfilt_ops[~filt].for_fop;
}

static void
kqueue_fo_release(int filt)
{

        if (filt > 0 || filt + EVFILT_SYSCOUNT < 0)
                return;

        if (sysfilt_ops[~filt].for_nolock)
                return;

        mtx_lock(&filterops_lock);
        KASSERT(sysfilt_ops[~filt].for_refcnt > 0,
            ("filter object %d refcount not valid on release", filt));
        sysfilt_ops[~filt].for_refcnt--;
        mtx_unlock(&filterops_lock);
}

/*
 * A ref to kq (obtained via kqueue_acquire) must be held.
 */
static int
kqueue_register(struct kqueue *kq, struct kevent *kev, struct thread *td,
    int mflag)
{
        const struct filterops *fops;
        struct file *fp;
        struct knote *kn, *tkn;
        struct knlist *knl;
        int error, filt, event;
        int haskqglobal, filedesc_unlock;

        if ((kev->flags & (EV_ENABLE | EV_DISABLE)) == (EV_ENABLE | EV_DISABLE))
                return (EINVAL);

        fp = NULL;
        kn = NULL;
        knl = NULL;
        error = 0;
        haskqglobal = 0;
        filedesc_unlock = 0;

        filt = kev->filter;
        fops = kqueue_fo_find(filt);
        if (fops == NULL)
                return EINVAL;

        if (kev->flags & EV_ADD) {
                /* Reject an invalid flag pair early */
                if (kev->flags & EV_KEEPUDATA) {
                        tkn = NULL;
                        error = EINVAL;
                        goto done;
                }

                /*
                 * Prevent waiting with locks.  Non-sleepable
                 * allocation failures are handled in the loop, only
                 * if the spare knote appears to be actually required.
                 */
                tkn = knote_alloc(mflag);
        } else {
                tkn = NULL;
        }

findkn:
        if (fops->f_isfd) {
                KASSERT(td != NULL, ("td is NULL"));
                if (kev->ident > INT_MAX)
                        error = EBADF;
                else
                        error = fget(td, kev->ident, &cap_event_rights, &fp);
                if (error)
                        goto done;

                if ((kev->flags & EV_ADD) == EV_ADD && kqueue_expand(kq, fops,
                    kev->ident, M_NOWAIT) != 0) {
                        /* try again */
                        fdrop(fp, td);
                        fp = NULL;
                        error = kqueue_expand(kq, fops, kev->ident, mflag);
                        if (error)
                                goto done;
                        goto findkn;
                }

                if (fp->f_type == DTYPE_KQUEUE) {
                        /*
                         * If we add some intelligence about what we are doing,
                         * we should be able to support events on ourselves.
                         * We need to know when we are doing this to prevent
                         * getting both the knlist lock and the kq lock since
                         * they are the same thing.
                         */
                        if (fp->f_data == kq) {
                                error = EINVAL;
                                goto done;
                        }

                        /*
                         * Pre-lock the filedesc before the global
                         * lock mutex, see the comment in
                         * kqueue_close().
                         */
                        FILEDESC_XLOCK(td->td_proc->p_fd);
                        filedesc_unlock = 1;
                        KQ_GLOBAL_LOCK(&kq_global, haskqglobal);
                }

                KQ_LOCK(kq);
                if (kev->ident < kq->kq_knlistsize) {
                        SLIST_FOREACH(kn, &kq->kq_knlist[kev->ident], kn_link) {
                                MPASS(kn->kn_kq == kq);
                                if (kev->filter == kn->kn_filter)
                                        break;
                        }
                }
        } else {
                if ((kev->flags & EV_ADD) == EV_ADD) {
                        error = kqueue_expand(kq, fops, kev->ident, mflag);
                        if (error != 0)
                                goto done;
                }

                KQ_LOCK(kq);

                /*
                 * If possible, find an existing knote to use for this kevent.
                 */
                if (kev->filter == EVFILT_PROC &&
                    (kev->flags & (EV_FLAG1 | EV_FLAG2)) != 0) {
                        /* This is an internal creation of a process tracking
                         * note. Don't attempt to coalesce this with an
                         * existing note.
                         */
                        ;
                } else if (kq->kq_knhashmask != 0) {
                        struct klist *list;

                        list = &kq->kq_knhash[
                            KN_HASH((u_long)kev->ident, kq->kq_knhashmask)];
                        SLIST_FOREACH(kn, list, kn_link) {
                                MPASS(kn->kn_kq == kq);
                                if (kev->ident == kn->kn_id &&
                                    kev->filter == kn->kn_filter)
                                        break;
                        }
                }
        }

        /* knote is in the process of changing, wait for it to stabilize. */
        if (kn != NULL && kn_in_flux(kn)) {
                KQ_GLOBAL_UNLOCK(&kq_global, haskqglobal);
                if (filedesc_unlock) {
                        FILEDESC_XUNLOCK(td->td_proc->p_fd);
                        filedesc_unlock = 0;
                }
                kq->kq_state |= KQ_FLUXWAIT;
                msleep(kq, &kq->kq_lock, PSOCK | PDROP, "kqflxwt", 0);
                if (fp != NULL) {
                        fdrop(fp, td);
                        fp = NULL;
                }
                goto findkn;
        }

        /*
         * kn now contains the matching knote, or NULL if no match
         */
        if (kn == NULL) {
                if (kev->flags & EV_ADD) {
                        kn = tkn;
                        tkn = NULL;
                        if (kn == NULL) {
                                KQ_UNLOCK(kq);
                                error = ENOMEM;
                                goto done;
                        }

                        /*
                         * Now that the kqueue is locked, make sure the fd
                         * didn't change out from under us.
                         */
                        if (fops->f_isfd &&
                            fget_noref_unlocked(td->td_proc->p_fd,
                            kev->ident) != fp) {
                                KQ_UNLOCK(kq);
                                tkn = kn;
                                error = EBADF;
                                goto done;
                        }
                        kn->kn_fp = fp;
                        kn->kn_kq = kq;
                        kn->kn_fop = fops;

                        kn->kn_sfflags = kev->fflags;
                        kn->kn_sdata = kev->data;
                        kev->fflags = 0;
                        kev->data = 0;
                        kn->kn_kevent = *kev;
                        kn->kn_kevent.flags &= ~(EV_ADD | EV_DELETE |
                            EV_ENABLE | EV_DISABLE | EV_FORCEONESHOT);
                        kn->kn_status = KN_DETACHED;
                        if ((kev->flags & EV_DISABLE) != 0)
                                kn->kn_status |= KN_DISABLED;
                        kn_enter_flux(kn);

                        error = knote_attach(kn, kq);
                        KQ_UNLOCK(kq);
                        if (error != 0) {
                                tkn = kn;
                                goto done;
                        }

                        /*
                         * We transfer ownership of fops/fp to the knote
                         * structure and avoid releasing them at the end of
                         * this routine, now that all of the remaining exit
                         * paths will knote_drop() to release the reference
                         * counts we held on them above.
                         */
                        fops = NULL;
                        fp = NULL;

                        if ((error = kn->kn_fop->f_attach(kn)) != 0) {
                                knote_drop_detached(kn, td);
                                goto done;
                        }
                        knl = kn_list_lock(kn);
                        goto done_ev_add;
                } else {
                        /* No matching knote and the EV_ADD flag is not set. */
                        KQ_UNLOCK(kq);
                        error = ENOENT;
                        goto done;
                }
        }

        if (kev->flags & EV_DELETE) {
                kn_enter_flux(kn);
                KQ_UNLOCK(kq);
                knote_drop(kn, td);
                goto done;
        }

        if (kev->flags & EV_FORCEONESHOT) {
                kn->kn_flags |= EV_ONESHOT;
                KNOTE_ACTIVATE(kn, 1);
        }

        if ((kev->flags & EV_ENABLE) != 0)
                kn->kn_status &= ~KN_DISABLED;
        else if ((kev->flags & EV_DISABLE) != 0)
                kn->kn_status |= KN_DISABLED;

        /*
         * The user may change some filter values after the initial EV_ADD,
         * but doing so will not reset any filter which has already been
         * triggered.
         */
        kn->kn_status |= KN_SCAN;
        kn_enter_flux(kn);
        KQ_UNLOCK(kq);
        knl = kn_list_lock(kn);
        if ((kev->flags & EV_KEEPUDATA) == 0)
                kn->kn_kevent.udata = kev->udata;
        if (!fops->f_isfd && fops->f_touch != NULL) {
                fops->f_touch(kn, kev, EVENT_REGISTER);
        } else {
                kn->kn_sfflags = kev->fflags;
                kn->kn_sdata = kev->data;
        }

done_ev_add:
        /*
         * We can get here with kn->kn_knlist == NULL.  This can happen when
         * the initial attach event decides that the event is "completed"
         * already, e.g., filt_procattach() is called on a zombie process.  It
         * will call filt_proc() which will remove it from the list, and NULL
         * kn_knlist.
         *
         * KN_DISABLED will be stable while the knote is in flux, so the
         * unlocked read will not race with an update.
         */
        if ((kn->kn_status & KN_DISABLED) == 0)
                event = kn->kn_fop->f_event(kn, 0);
        else
                event = 0;

        KQ_LOCK(kq);
        if (event)
                kn->kn_status |= KN_ACTIVE;
        if ((kn->kn_status & (KN_ACTIVE | KN_DISABLED | KN_QUEUED)) ==
            KN_ACTIVE)
                knote_enqueue(kn);
        kn->kn_status &= ~KN_SCAN;
        kn_leave_flux(kn);
        kn_list_unlock(knl);
        KQ_UNLOCK_FLUX(kq);

done:
        KQ_GLOBAL_UNLOCK(&kq_global, haskqglobal);
        if (filedesc_unlock)
                FILEDESC_XUNLOCK(td->td_proc->p_fd);
        if (fp != NULL)
                fdrop(fp, td);
        knote_free(tkn);
        if (fops != NULL)
                kqueue_fo_release(filt);
        return (error);
}

static int
kqueue_acquire_ref(struct kqueue *kq)
{
        KQ_LOCK(kq);
        if ((kq->kq_state & KQ_CLOSING) == KQ_CLOSING) {
                KQ_UNLOCK(kq);
                return (EBADF);
        }
        kq->kq_refcnt++;
        KQ_UNLOCK(kq);
        return (0);
}

static int
kqueue_acquire(struct file *fp, struct kqueue **kqp)
{
        struct kqueue *kq;
        int error;

        kq = fp->f_data;
        if (fp->f_type != DTYPE_KQUEUE || kq == NULL)
                return (EINVAL);
        error = kqueue_acquire_ref(kq);
        if (error == 0)
                *kqp = kq;
        return (error);
}

static void
kqueue_release(struct kqueue *kq, int locked)
{
        if (locked)
                KQ_OWNED(kq);
        else
                KQ_LOCK(kq);
        kq->kq_refcnt--;
        if (kq->kq_refcnt == 1)
                wakeup(&kq->kq_refcnt);
        if (!locked)
                KQ_UNLOCK(kq);
}

static void
ast_kqueue(struct thread *td, int tda __unused)
{
        taskqueue_quiesce(taskqueue_kqueue_ctx);
}

static void
kqueue_schedtask(struct kqueue *kq)
{
        KQ_OWNED(kq);
        KASSERT(((kq->kq_state & KQ_TASKDRAIN) != KQ_TASKDRAIN),
            ("scheduling kqueue task while draining"));

        if ((kq->kq_state & KQ_TASKSCHED) != KQ_TASKSCHED) {
                taskqueue_enqueue(taskqueue_kqueue_ctx, &kq->kq_task);
                kq->kq_state |= KQ_TASKSCHED;
                ast_sched(curthread, TDA_KQUEUE);
        }
}

/*
 * Expand the kq to make sure we have storage for fops/ident pair.
 *
 * Return 0 on success (or no work necessary), return errno on failure.
 */
static int
kqueue_expand(struct kqueue *kq, const struct filterops *fops, uintptr_t ident,
    int mflag)
{
        struct klist *list, *tmp_knhash, *to_free;
        u_long tmp_knhashmask;
        int error, fd, size;

        KQ_NOTOWNED(kq);

        error = 0;
        to_free = NULL;
        if (fops->f_isfd) {
                fd = ident;
                size = atomic_load_int(&kq->kq_knlistsize);
                if (size <= fd) {
                        do {
                                size += KQEXTENT;
                        } while (size <= fd);
                        list = malloc(size * sizeof(*list), M_KQUEUE, mflag);
                        if (list == NULL)
                                return ENOMEM;
                        KQ_LOCK(kq);
                        if ((kq->kq_state & KQ_CLOSING) != 0) {
                                to_free = list;
                                error = EBADF;
                        } else if (kq->kq_knlistsize >= size) {
                                to_free = list;
                        } else {
                                if (kq->kq_knlist != NULL) {
                                        bcopy(kq->kq_knlist, list,
                                            kq->kq_knlistsize * sizeof(*list));
                                        to_free = kq->kq_knlist;
                                        kq->kq_knlist = NULL;
                                }
                                bzero((caddr_t)list +
                                    kq->kq_knlistsize * sizeof(*list),
                                    (size - kq->kq_knlistsize) * sizeof(*list));
                                kq->kq_knlistsize = size;
                                kq->kq_knlist = list;
                        }
                        MPASS(error != 0 || kq->kq_knlistsize > fd);
                        KQ_UNLOCK(kq);
                }
        } else {
                if (kq->kq_knhashmask == 0) {
                        tmp_knhash = hashinit_flags(KN_HASHSIZE, M_KQUEUE,
                            &tmp_knhashmask, (mflag & M_WAITOK) != 0 ?
                            HASH_WAITOK : HASH_NOWAIT);
                        if (tmp_knhash == NULL)
                                return (ENOMEM);
                        KQ_LOCK(kq);
                        if ((kq->kq_state & KQ_CLOSING) != 0) {
                                to_free = tmp_knhash;
                                error = EBADF;
                        } else if (kq->kq_knhashmask == 0) {
                                kq->kq_knhash = tmp_knhash;
                                kq->kq_knhashmask = tmp_knhashmask;
                        } else {
                                to_free = tmp_knhash;
                        }
                        KQ_UNLOCK(kq);
                }
        }
        free(to_free, M_KQUEUE);

        KQ_NOTOWNED(kq);
        return (error);
}

static void
kqueue_task(void *arg, int pending)
{
        struct kqueue *kq;
        int haskqglobal;

        haskqglobal = 0;
        kq = arg;

        KQ_GLOBAL_LOCK(&kq_global, haskqglobal);
        KQ_LOCK(kq);

        KNOTE_LOCKED(&kq->kq_sel.si_note, 0);

        kq->kq_state &= ~KQ_TASKSCHED;
        if ((kq->kq_state & KQ_TASKDRAIN) == KQ_TASKDRAIN) {
                wakeup(&kq->kq_state);
        }
        KQ_UNLOCK(kq);
        KQ_GLOBAL_UNLOCK(&kq_global, haskqglobal);
}

/*
 * Scan, update kn_data (if not ONESHOT), and copyout triggered events.
 * We treat KN_MARKER knotes as if they are in flux.
 */
static int
kqueue_scan(struct kqueue *kq, int maxevents, struct kevent_copyops *k_ops,
    const struct timespec *tsp, struct kevent *keva, struct thread *td)
{
        struct kevent *kevp;
        struct knote *kn, *marker;
        struct knlist *knl;
        sbintime_t asbt, rsbt;
        int count, error, haskqglobal, influx, nkev, touch;

        count = maxevents;
        nkev = 0;
        error = 0;
        haskqglobal = 0;

        if (maxevents == 0)
                goto done_nl;
        if (maxevents < 0) {
                error = EINVAL;
                goto done_nl;
        }

        rsbt = 0;
        if (tsp != NULL) {
                if (!timespecvalid_interval(tsp)) {
                        error = EINVAL;
                        goto done_nl;
                }
                if (timespecisset(tsp)) {
                        if (tsp->tv_sec <= INT32_MAX) {
                                rsbt = tstosbt(*tsp);
                                if (TIMESEL(&asbt, rsbt))
                                        asbt += tc_tick_sbt;
                                if (asbt <= SBT_MAX - rsbt)
                                        asbt += rsbt;
                                else
                                        asbt = 0;
                                rsbt >>= tc_precexp;
                        } else
                                asbt = 0;
                } else
                        asbt = -1;
        } else
                asbt = 0;
        marker = knote_alloc(M_WAITOK);
        marker->kn_status = KN_MARKER;
        KQ_LOCK(kq);

retry:
        kevp = keva;
        if (kq->kq_count == 0) {
                if (asbt == -1) {
                        error = EWOULDBLOCK;
                } else {
                        kq->kq_state |= KQ_SLEEP;
                        error = msleep_sbt(kq, &kq->kq_lock, PSOCK | PCATCH,
                            "kqread", asbt, rsbt, C_ABSOLUTE);
                }
                if (error == 0)
                        goto retry;
                /* don't restart after signals... */
                if (error == ERESTART)
                        error = EINTR;
                else if (error == EWOULDBLOCK)
                        error = 0;
                goto done;
        }

        TAILQ_INSERT_TAIL(&kq->kq_head, marker, kn_tqe);
        influx = 0;
        while (count) {
                KQ_OWNED(kq);
                kn = TAILQ_FIRST(&kq->kq_head);

                if ((kn->kn_status == KN_MARKER && kn != marker) ||
                    kn_in_flux(kn)) {
                        if (influx) {
                                influx = 0;
                                KQ_FLUX_WAKEUP(kq);
                        }
                        kq->kq_state |= KQ_FLUXWAIT;
                        error = msleep(kq, &kq->kq_lock, PSOCK,
                            "kqflxwt", 0);
                        continue;
                }

                TAILQ_REMOVE(&kq->kq_head, kn, kn_tqe);
                if ((kn->kn_status & KN_DISABLED) == KN_DISABLED) {
                        kn->kn_status &= ~KN_QUEUED;
                        kq->kq_count--;
                        continue;
                }
                if (kn == marker) {
                        KQ_FLUX_WAKEUP(kq);
                        if (count == maxevents)
                                goto retry;
                        goto done;
                }
                KASSERT(!kn_in_flux(kn),
                    ("knote %p is unexpectedly in flux", kn));

                if ((kn->kn_flags & EV_DROP) == EV_DROP) {
                        kn->kn_status &= ~KN_QUEUED;
                        kn_enter_flux(kn);
                        kq->kq_count--;
                        KQ_UNLOCK(kq);
                        /*
                         * We don't need to lock the list since we've
                         * marked it as in flux.
                         */
                        knote_drop(kn, td);
                        KQ_LOCK(kq);
                        continue;
                } else if ((kn->kn_flags & EV_ONESHOT) == EV_ONESHOT) {
                        kn->kn_status &= ~KN_QUEUED;
                        kn_enter_flux(kn);
                        kq->kq_count--;
                        KQ_UNLOCK(kq);
                        /*
                         * We don't need to lock the list since we've
                         * marked the knote as being in flux.
                         */
                        *kevp = kn->kn_kevent;
                        knote_drop(kn, td);
                        KQ_LOCK(kq);
                        kn = NULL;
                } else {
                        kn->kn_status |= KN_SCAN;
                        kn_enter_flux(kn);
                        KQ_UNLOCK(kq);
                        if ((kn->kn_status & KN_KQUEUE) == KN_KQUEUE)
                                KQ_GLOBAL_LOCK(&kq_global, haskqglobal);
                        knl = kn_list_lock(kn);
                        if (kn->kn_fop->f_event(kn, 0) == 0) {
                                KQ_LOCK(kq);
                                KQ_GLOBAL_UNLOCK(&kq_global, haskqglobal);
                                kn->kn_status &= ~(KN_QUEUED | KN_ACTIVE |
                                    KN_SCAN);
                                kn_leave_flux(kn);
                                kq->kq_count--;
                                kn_list_unlock(knl);
                                influx = 1;
                                continue;
                        }
                        touch = (!kn->kn_fop->f_isfd &&
                            kn->kn_fop->f_touch != NULL);
                        if (touch)
                                kn->kn_fop->f_touch(kn, kevp, EVENT_PROCESS);
                        else
                                *kevp = kn->kn_kevent;
                        KQ_LOCK(kq);
                        KQ_GLOBAL_UNLOCK(&kq_global, haskqglobal);
                        if (kn->kn_flags & (EV_CLEAR | EV_DISPATCH)) {
                                /*
                                 * Manually clear knotes who weren't
                                 * 'touch'ed.
                                 */
                                if (touch == 0 && kn->kn_flags & EV_CLEAR) {
                                        kn->kn_data = 0;
                                        kn->kn_fflags = 0;
                                }
                                if (kn->kn_flags & EV_DISPATCH)
                                        kn->kn_status |= KN_DISABLED;
                                kn->kn_status &= ~(KN_QUEUED | KN_ACTIVE);
                                kq->kq_count--;
                        } else
                                TAILQ_INSERT_TAIL(&kq->kq_head, kn, kn_tqe);

                        kn->kn_status &= ~KN_SCAN;
                        kn_leave_flux(kn);
                        kn_list_unlock(knl);
                        influx = 1;
                }

                /* we are returning a copy to the user */
                kevp++;
                nkev++;
                count--;

                if (nkev == KQ_NEVENTS) {
                        influx = 0;
                        KQ_UNLOCK_FLUX(kq);
                        error = k_ops->k_copyout(k_ops->arg, keva, nkev);
                        nkev = 0;
                        kevp = keva;
                        KQ_LOCK(kq);
                        if (error)
                                break;
                }
        }
        TAILQ_REMOVE(&kq->kq_head, marker, kn_tqe);
done:
        KQ_OWNED(kq);
        KQ_UNLOCK_FLUX(kq);
        knote_free(marker);
done_nl:
        KQ_NOTOWNED(kq);
        if (nkev != 0)
                error = k_ops->k_copyout(k_ops->arg, keva, nkev);
        td->td_retval[0] = maxevents - count;
        return (error);
}

/*ARGSUSED*/
static int
kqueue_ioctl(struct file *fp, u_long cmd, void *data,
        struct ucred *active_cred, struct thread *td)
{
        /*
         * Enabling sigio causes two major problems:
         * 1) infinite recursion:
         * Synopsys: kevent is being used to track signals and have FIOASYNC
         * set.  On receipt of a signal this will cause a kqueue to recurse
         * into itself over and over.  Sending the sigio causes the kqueue
         * to become ready, which in turn posts sigio again, forever.
         * Solution: this can be solved by setting a flag in the kqueue that
         * we have a SIGIO in progress.
         * 2) locking problems:
         * Synopsys: Kqueue is a leaf subsystem, but adding signalling puts
         * us above the proc and pgrp locks.
         * Solution: Post a signal using an async mechanism, being sure to
         * record a generation count in the delivery so that we do not deliver
         * a signal to the wrong process.
         *
         * Note, these two mechanisms are somewhat mutually exclusive!
         */
#if 0
        struct kqueue *kq;

        kq = fp->f_data;
        switch (cmd) {
        case FIOASYNC:
                if (*(int *)data) {
                        kq->kq_state |= KQ_ASYNC;
                } else {
                        kq->kq_state &= ~KQ_ASYNC;
                }
                return (0);

        case FIOSETOWN:
                return (fsetown(*(int *)data, &kq->kq_sigio));

        case FIOGETOWN:
                *(int *)data = fgetown(&kq->kq_sigio);
                return (0);
        }
#endif

        return (ENOTTY);
}

/*ARGSUSED*/
static int
kqueue_poll(struct file *fp, int events, struct ucred *active_cred,
        struct thread *td)
{
        struct kqueue *kq;
        int revents = 0;
        int error;

        if ((error = kqueue_acquire(fp, &kq)))
                return POLLERR;

        KQ_LOCK(kq);
        if (events & (POLLIN | POLLRDNORM)) {
                if (kq->kq_count) {
                        revents |= events & (POLLIN | POLLRDNORM);
                } else {
                        selrecord(td, &kq->kq_sel);
                        if (SEL_WAITING(&kq->kq_sel))
                                kq->kq_state |= KQ_SEL;
                }
        }
        kqueue_release(kq, 1);
        KQ_UNLOCK(kq);
        return (revents);
}

/*ARGSUSED*/
static int
kqueue_stat(struct file *fp, struct stat *st, struct ucred *active_cred)
{

        bzero((void *)st, sizeof *st);
        /*
         * We no longer return kq_count because the unlocked value is useless.
         * If you spent all this time getting the count, why not spend your
         * syscall better by calling kevent?
         *
         * XXX - This is needed for libc_r.
         */
        st->st_mode = S_IFIFO;
        return (0);
}

static void
kqueue_drain(struct kqueue *kq, struct thread *td)
{
        struct knote *kn;
        int i;

        KQ_LOCK(kq);

        KASSERT((kq->kq_state & KQ_CLOSING) != KQ_CLOSING,
            ("kqueue already closing"));
        kq->kq_state |= KQ_CLOSING;
        if (kq->kq_refcnt > 1)
                msleep(&kq->kq_refcnt, &kq->kq_lock, PSOCK, "kqclose", 0);

        KASSERT(kq->kq_refcnt == 1, ("other refs are out there!"));

        KASSERT(knlist_empty(&kq->kq_sel.si_note),
            ("kqueue's knlist not empty"));

        for (i = 0; i < kq->kq_knlistsize; i++) {
                while ((kn = SLIST_FIRST(&kq->kq_knlist[i])) != NULL) {
                        if (kn_in_flux(kn)) {
                                kq->kq_state |= KQ_FLUXWAIT;
                                msleep(kq, &kq->kq_lock, PSOCK, "kqclo1", 0);
                                continue;
                        }
                        kn_enter_flux(kn);
                        KQ_UNLOCK(kq);
                        knote_drop(kn, td);
                        KQ_LOCK(kq);
                }
        }
        if (kq->kq_knhashmask != 0) {
                for (i = 0; i <= kq->kq_knhashmask; i++) {
                        while ((kn = SLIST_FIRST(&kq->kq_knhash[i])) != NULL) {
                                if (kn_in_flux(kn)) {
                                        kq->kq_state |= KQ_FLUXWAIT;
                                        msleep(kq, &kq->kq_lock, PSOCK,
                                               "kqclo2", 0);
                                        continue;
                                }
                                kn_enter_flux(kn);
                                KQ_UNLOCK(kq);
                                knote_drop(kn, td);
                                KQ_LOCK(kq);
                        }
                }
        }

        if ((kq->kq_state & KQ_TASKSCHED) == KQ_TASKSCHED) {
                kq->kq_state |= KQ_TASKDRAIN;
                msleep(&kq->kq_state, &kq->kq_lock, PSOCK, "kqtqdr", 0);
        }

        if ((kq->kq_state & KQ_SEL) == KQ_SEL) {
                selwakeuppri(&kq->kq_sel, PSOCK);
                if (!SEL_WAITING(&kq->kq_sel))
                        kq->kq_state &= ~KQ_SEL;
        }

        KQ_UNLOCK(kq);
}

static void
kqueue_destroy(struct kqueue *kq)
{

        KASSERT(kq->kq_fdp == NULL,
            ("kqueue still attached to a file descriptor"));
        seldrain(&kq->kq_sel);
        knlist_destroy(&kq->kq_sel.si_note);
        mtx_destroy(&kq->kq_lock);

        if (kq->kq_knhash != NULL)
                free(kq->kq_knhash, M_KQUEUE);
        if (kq->kq_knlist != NULL)
                free(kq->kq_knlist, M_KQUEUE);

        funsetown(&kq->kq_sigio);
}

/*ARGSUSED*/
static int
kqueue_close(struct file *fp, struct thread *td)
{
        struct kqueue *kq = fp->f_data;
        struct filedesc *fdp;
        int error;
        int filedesc_unlock;

        if ((error = kqueue_acquire(fp, &kq)))
                return error;
        kqueue_drain(kq, td);

        /*
         * We could be called due to the knote_drop() doing fdrop(),
         * called from kqueue_register().  In this case the global
         * lock is owned, and filedesc sx is locked before, to not
         * take the sleepable lock after non-sleepable.
         */
        fdp = kq->kq_fdp;
        kq->kq_fdp = NULL;
        if (!sx_xlocked(FILEDESC_LOCK(fdp))) {
                FILEDESC_XLOCK(fdp);
                filedesc_unlock = 1;
        } else
                filedesc_unlock = 0;
        TAILQ_REMOVE(&fdp->fd_kqlist, kq, kq_list);
        if (filedesc_unlock)
                FILEDESC_XUNLOCK(fdp);

        kqueue_destroy(kq);
        chgkqcnt(kq->kq_cred->cr_ruidinfo, -1, 0);
        crfree(kq->kq_cred);
        free(kq, M_KQUEUE);
        fp->f_data = NULL;

        return (0);
}

static int
kqueue_fill_kinfo(struct file *fp, struct kinfo_file *kif, struct filedesc *fdp)
{
        struct kqueue *kq = fp->f_data;

        kif->kf_type = KF_TYPE_KQUEUE;
        kif->kf_un.kf_kqueue.kf_kqueue_addr = (uintptr_t)kq;
        kif->kf_un.kf_kqueue.kf_kqueue_count = kq->kq_count;
        kif->kf_un.kf_kqueue.kf_kqueue_state = kq->kq_state;
        return (0);
}

static void
kqueue_wakeup(struct kqueue *kq)
{
        KQ_OWNED(kq);

        if ((kq->kq_state & KQ_SLEEP) == KQ_SLEEP) {
                kq->kq_state &= ~KQ_SLEEP;
                wakeup(kq);
        }
        if ((kq->kq_state & KQ_SEL) == KQ_SEL) {
                selwakeuppri(&kq->kq_sel, PSOCK);
                if (!SEL_WAITING(&kq->kq_sel))
                        kq->kq_state &= ~KQ_SEL;
        }
        if (!knlist_empty(&kq->kq_sel.si_note))
                kqueue_schedtask(kq);
        if ((kq->kq_state & KQ_ASYNC) == KQ_ASYNC) {
                pgsigio(&kq->kq_sigio, SIGIO, 0);
        }
}

/*
 * Walk down a list of knotes, activating them if their event has triggered.
 *
 * There is a possibility to optimize in the case of one kq watching another.
 * Instead of scheduling a task to wake it up, you could pass enough state
 * down the chain to make up the parent kqueue.  Make this code functional
 * first.
 */
void
knote(struct knlist *list, long hint, int lockflags)
{
        struct kqueue *kq;
        struct knote *kn, *tkn;
        int error;

        if (list == NULL)
                return;

        KNL_ASSERT_LOCK(list, lockflags & KNF_LISTLOCKED);

        if ((lockflags & KNF_LISTLOCKED) == 0)
                list->kl_lock(list->kl_lockarg); 

        /*
         * If we unlock the list lock (and enter influx), we can
         * eliminate the kqueue scheduling, but this will introduce
         * four lock/unlock's for each knote to test.  Also, marker
         * would be needed to keep iteration position, since filters
         * or other threads could remove events.
         */
        SLIST_FOREACH_SAFE(kn, &list->kl_list, kn_selnext, tkn) {
                kq = kn->kn_kq;
                KQ_LOCK(kq);
                if (kn_in_flux(kn) && (kn->kn_status & KN_SCAN) == 0) {
                        /*
                         * Do not process the influx notes, except for
                         * the influx coming from the kq unlock in the
                         * kqueue_scan().  In the later case, we do
                         * not interfere with the scan, since the code
                         * fragment in kqueue_scan() locks the knlist,
                         * and cannot proceed until we finished.
                         */
                        KQ_UNLOCK(kq);
                } else if ((lockflags & KNF_NOKQLOCK) != 0) {
                        kn_enter_flux(kn);
                        KQ_UNLOCK(kq);
                        error = kn->kn_fop->f_event(kn, hint);
                        KQ_LOCK(kq);
                        kn_leave_flux(kn);
                        if (error)
                                KNOTE_ACTIVATE(kn, 1);
                        KQ_UNLOCK_FLUX(kq);
                } else {
                        if (kn->kn_fop->f_event(kn, hint))
                                KNOTE_ACTIVATE(kn, 1);
                        KQ_UNLOCK(kq);
                }
        }
        if ((lockflags & KNF_LISTLOCKED) == 0)
                list->kl_unlock(list->kl_lockarg); 
}

/*
 * add a knote to a knlist
 */
void
knlist_add(struct knlist *knl, struct knote *kn, int islocked)
{

        KNL_ASSERT_LOCK(knl, islocked);
        KQ_NOTOWNED(kn->kn_kq);
        KASSERT(kn_in_flux(kn), ("knote %p not in flux", kn));
        KASSERT((kn->kn_status & KN_DETACHED) != 0,
            ("knote %p was not detached", kn));
        KASSERT(kn->kn_knlist == NULL,
            ("knote %p was already on knlist %p", kn, kn->kn_knlist));
        if (!islocked)
                knl->kl_lock(knl->kl_lockarg);
        SLIST_INSERT_HEAD(&knl->kl_list, kn, kn_selnext);
        if (!islocked)
                knl->kl_unlock(knl->kl_lockarg);
        KQ_LOCK(kn->kn_kq);
        kn->kn_knlist = knl;
        kn->kn_status &= ~KN_DETACHED;
        KQ_UNLOCK(kn->kn_kq);
}

static void
knlist_remove_kq(struct knlist *knl, struct knote *kn, int knlislocked,
    int kqislocked)
{

        KASSERT(!kqislocked || knlislocked, ("kq locked w/o knl locked"));
        KNL_ASSERT_LOCK(knl, knlislocked);
        mtx_assert(&kn->kn_kq->kq_lock, kqislocked ? MA_OWNED : MA_NOTOWNED);
        KASSERT(kqislocked || kn_in_flux(kn), ("knote %p not in flux", kn));
        KASSERT((kn->kn_status & KN_DETACHED) == 0,
            ("knote %p was already detached", kn));
        KASSERT(kn->kn_knlist == knl,
            ("knote %p was not on knlist %p", kn, knl));
        if (!knlislocked)
                knl->kl_lock(knl->kl_lockarg);
        SLIST_REMOVE(&knl->kl_list, kn, knote, kn_selnext);
        kn->kn_knlist = NULL;
        if (!knlislocked)
                kn_list_unlock(knl);
        if (!kqislocked)
                KQ_LOCK(kn->kn_kq);
        kn->kn_status |= KN_DETACHED;
        if (!kqislocked)
                KQ_UNLOCK(kn->kn_kq);
}

/*
 * remove knote from the specified knlist
 */
void
knlist_remove(struct knlist *knl, struct knote *kn, int islocked)
{

        knlist_remove_kq(knl, kn, islocked, 0);
}

int
knlist_empty(struct knlist *knl)
{

        KNL_ASSERT_LOCKED(knl);
        return (SLIST_EMPTY(&knl->kl_list));
}

static struct mtx knlist_lock;
MTX_SYSINIT(knlist_lock, &knlist_lock, "knlist lock for lockless objects",
    MTX_DEF);
static void knlist_mtx_lock(void *arg);
static void knlist_mtx_unlock(void *arg);

static void
knlist_mtx_lock(void *arg)
{

        mtx_lock((struct mtx *)arg);
}

static void
knlist_mtx_unlock(void *arg)
{

        mtx_unlock((struct mtx *)arg);
}

static void
knlist_mtx_assert_lock(void *arg, int what)
{

        if (what == LA_LOCKED)
                mtx_assert((struct mtx *)arg, MA_OWNED);
        else
                mtx_assert((struct mtx *)arg, MA_NOTOWNED);
}

void
knlist_init(struct knlist *knl, void *lock, void (*kl_lock)(void *),
    void (*kl_unlock)(void *),
    void (*kl_assert_lock)(void *, int))
{

        if (lock == NULL)
                knl->kl_lockarg = &knlist_lock;
        else
                knl->kl_lockarg = lock;

        if (kl_lock == NULL)
                knl->kl_lock = knlist_mtx_lock;
        else
                knl->kl_lock = kl_lock;
        if (kl_unlock == NULL)
                knl->kl_unlock = knlist_mtx_unlock;
        else
                knl->kl_unlock = kl_unlock;
        if (kl_assert_lock == NULL)
                knl->kl_assert_lock = knlist_mtx_assert_lock;
        else
                knl->kl_assert_lock = kl_assert_lock;

        knl->kl_autodestroy = 0;
        SLIST_INIT(&knl->kl_list);
}

void
knlist_init_mtx(struct knlist *knl, struct mtx *lock)
{

        knlist_init(knl, lock, NULL, NULL, NULL);
}

struct knlist *
knlist_alloc(struct mtx *lock)
{
        struct knlist *knl;

        knl = malloc(sizeof(struct knlist), M_KQUEUE, M_WAITOK);
        knlist_init_mtx(knl, lock);
        return (knl);
}

void
knlist_destroy(struct knlist *knl)
{

        KASSERT(KNLIST_EMPTY(knl),
            ("destroying knlist %p with knotes on it", knl));
}

void
knlist_detach(struct knlist *knl)
{

        KNL_ASSERT_LOCKED(knl);
        knl->kl_autodestroy = 1;
        if (knlist_empty(knl)) {
                knlist_destroy(knl);
                free(knl, M_KQUEUE);
        }
}

/*
 * Even if we are locked, we may need to drop the lock to allow any influx
 * knotes time to "settle".
 */
void
knlist_cleardel(struct knlist *knl, struct thread *td, int islocked, int killkn)
{
        struct knote *kn, *kn2;
        struct kqueue *kq;

        KASSERT(!knl->kl_autodestroy, ("cleardel for autodestroy %p", knl));
        if (islocked)
                KNL_ASSERT_LOCKED(knl);
        else {
                KNL_ASSERT_UNLOCKED(knl);
                knl->kl_lock(knl->kl_lockarg);
        }

        for (;;) {
                /*
                 * Each pass removes as many knotes as we can before dropping
                 * into FLUXWAIT.  Active knotes are simply detached and either
                 * freed or converted to one-shot, as the attached subject is
                 * essentially disappearing.
                 */
                SLIST_FOREACH_SAFE(kn, &knl->kl_list, kn_selnext, kn2) {
                        kq = kn->kn_kq;
                        KQ_LOCK(kq);
                        if (kn_in_flux(kn)) {
                                KQ_UNLOCK(kq);
                                continue;
                        }
                        knlist_remove_kq(knl, kn, 1, 1);
                        if (killkn) {
                                kn_enter_flux(kn);
                                KQ_UNLOCK(kq);
                                knote_drop_detached(kn, td);
                        } else {
                                /* Make sure cleared knotes disappear soon */
                                kn->kn_flags |= EV_EOF | EV_ONESHOT;
                                KQ_UNLOCK(kq);
                        }
                        kq = NULL;
                }

                if (SLIST_EMPTY(&knl->kl_list))
                        break;

                /* there are still in flux knotes remaining */
                kn = SLIST_FIRST(&knl->kl_list);
                kq = kn->kn_kq;
                KQ_LOCK(kq);
                KASSERT(kn_in_flux(kn), ("knote removed w/o list lock"));
                knl->kl_unlock(knl->kl_lockarg);
                kq->kq_state |= KQ_FLUXWAIT;
                msleep(kq, &kq->kq_lock, PSOCK | PDROP, "kqkclr", 0);
                kq = NULL;
                knl->kl_lock(knl->kl_lockarg);
        }

        if (islocked)
                KNL_ASSERT_LOCKED(knl);
        else {
                knl->kl_unlock(knl->kl_lockarg);
                KNL_ASSERT_UNLOCKED(knl);
        }
}

/*
 * Remove all knotes referencing a specified fd must be called with FILEDESC
 * lock.  This prevents a race where a new fd comes along and occupies the
 * entry and we attach a knote to the fd.
 */
void
knote_fdclose(struct thread *td, int fd)
{
        struct filedesc *fdp = td->td_proc->p_fd;
        struct kqueue *kq;
        struct knote *kn;

        FILEDESC_XLOCK_ASSERT(fdp);

        /*
         * We shouldn't have to worry about new kevents appearing on fd
         * since filedesc is locked.
         */
        TAILQ_FOREACH(kq, &fdp->fd_kqlist, kq_list) {
                KQ_LOCK(kq);
                if (kq->kq_knlistsize <= fd ||
                    SLIST_EMPTY(&kq->kq_knlist[fd])) {
                        KQ_UNLOCK(kq);
                        continue;
                }

                while ((kn = SLIST_FIRST(&kq->kq_knlist[fd])) != NULL) {
                        if (kn_in_flux(kn)) {
                                /*
                                 * Wait for this knote to stabilize, it could be
                                 * the case that it's in the process of being
                                 * dropped anyways.
                                 */
                                kq->kq_state |= KQ_FLUXWAIT;
                                msleep(kq, &kq->kq_lock, PSOCK, "kqflxwt", 0);
                                continue;
                        }
                        kn_enter_flux(kn);
                        KQ_UNLOCK(kq);
                        knote_drop(kn, td);
                        KQ_LOCK(kq);
                }
                KQ_UNLOCK_FLUX(kq);
        }
}

static int
knote_attach(struct knote *kn, struct kqueue *kq)
{
        struct klist *list;

        KASSERT(kn_in_flux(kn), ("knote %p not marked influx", kn));
        KQ_OWNED(kq);
        MPASS(kn->kn_kq == kq);

        if ((kq->kq_state & KQ_CLOSING) != 0)
                return (EBADF);
        if (kn->kn_fop->f_isfd) {
                if (kn->kn_id >= kq->kq_knlistsize)
                        return (ENOMEM);
                list = &kq->kq_knlist[kn->kn_id];
        } else {
                if (kq->kq_knhash == NULL)
                        return (ENOMEM);
                list = &kq->kq_knhash[KN_HASH(kn->kn_id, kq->kq_knhashmask)];
        }
        SLIST_INSERT_HEAD(list, kn, kn_link);
        return (0);
}

static void
knote_drop(struct knote *kn, struct thread *td)
{

        if ((kn->kn_status & KN_DETACHED) == 0)
                kn->kn_fop->f_detach(kn);
        knote_drop_detached(kn, td);
}

static void
knote_drop_detached(struct knote *kn, struct thread *td)
{
        struct kqueue *kq;
        struct klist *list;

        kq = kn->kn_kq;

        KASSERT((kn->kn_status & KN_DETACHED) != 0,
            ("knote %p still attached", kn));
        KQ_NOTOWNED(kq);

        KQ_LOCK(kq);
        for (;;) {
                KASSERT(kn->kn_influx >= 1,
                    ("knote_drop called on %p with influx %d",
                    kn, kn->kn_influx));
                if (kn->kn_influx == 1)
                        break;
                kq->kq_state |= KQ_FLUXWAIT;
                msleep(kq, &kq->kq_lock, PSOCK, "kqflxwt", 0);
        }

        MPASS(kn->kn_kq == kq);
        if (kn->kn_fop->f_isfd)
                list = &kq->kq_knlist[kn->kn_id];
        else
                list = &kq->kq_knhash[KN_HASH(kn->kn_id, kq->kq_knhashmask)];

        SLIST_REMOVE(list, kn, knote, kn_link);
        if (kn->kn_status & KN_QUEUED)
                knote_dequeue(kn);
        KQ_UNLOCK_FLUX(kq);

        if (kn->kn_fop->f_isfd) {
                fdrop(kn->kn_fp, td);
                kn->kn_fp = NULL;
        }
        kqueue_fo_release(kn->kn_kevent.filter);
        kn->kn_fop = NULL;
        knote_free(kn);
}

static void
knote_enqueue(struct knote *kn)
{
        struct kqueue *kq = kn->kn_kq;

        KQ_OWNED(kn->kn_kq);
        KASSERT((kn->kn_status & KN_QUEUED) == 0, ("knote already queued"));

        TAILQ_INSERT_TAIL(&kq->kq_head, kn, kn_tqe);
        kn->kn_status |= KN_QUEUED;
        kq->kq_count++;
        kqueue_wakeup(kq);
}

static void
knote_dequeue(struct knote *kn)
{
        struct kqueue *kq = kn->kn_kq;

        KQ_OWNED(kn->kn_kq);
        KASSERT(kn->kn_status & KN_QUEUED, ("knote not queued"));

        TAILQ_REMOVE(&kq->kq_head, kn, kn_tqe);
        kn->kn_status &= ~KN_QUEUED;
        kq->kq_count--;
}

static void
knote_init(void *dummy __unused)
{

        knote_zone = uma_zcreate("KNOTE", sizeof(struct knote), NULL, NULL,
            NULL, NULL, UMA_ALIGN_PTR, 0);
        ast_register(TDA_KQUEUE, ASTR_ASTF_REQUIRED, 0, ast_kqueue);
        prison0.pr_klist = knlist_alloc(&prison0.pr_mtx);
}
SYSINIT(knote, SI_SUB_PSEUDO, SI_ORDER_ANY, knote_init, NULL);

static struct knote *
knote_alloc(int mflag)
{

        return (uma_zalloc(knote_zone, mflag | M_ZERO));
}

static void
knote_free(struct knote *kn)
{

        uma_zfree(knote_zone, kn);
}

/*
 * Register the kev w/ the kq specified by fd.
 */
int
kqfd_register(int fd, struct kevent *kev, struct thread *td, int mflag)
{
        struct kqueue *kq;
        struct file *fp;
        cap_rights_t rights;
        int error;

        error = fget(td, fd, cap_rights_init_one(&rights, CAP_KQUEUE_CHANGE),
            &fp);
        if (error != 0)
                return (error);
        if ((error = kqueue_acquire(fp, &kq)) != 0)
                goto noacquire;

        error = kqueue_register(kq, kev, td, mflag);
        kqueue_release(kq, 0);

noacquire:
        fdrop(fp, td);
        return (error);
}

static int
kqueue_fork_alloc(struct filedesc *fdp, struct file *fp, struct file **fp1,
    struct thread *td)
{
        struct kqueue *kq, *kq1;
        int error;

        MPASS(fp->f_type == DTYPE_KQUEUE);
        kq = fp->f_data;
        if ((kq->kq_state & KQ_CPONFORK) == 0)
                return (EOPNOTSUPP);
        error = kqueue_acquire_ref(kq);
        if (error != 0)
                return (error);
        error = kern_kqueue_alloc(td, fdp, NULL, fp1, 0, NULL, true, &kq1);
        if (error == 0) {
                kq1->kq_forksrc = kq;
                (*fp1)->f_flag = fp->f_flag & (FREAD | FWRITE | FEXEC |
                    O_CLOEXEC | O_CLOFORK);
        } else {
                kqueue_release(kq, 0);
        }
        return (error);
}

static void
kqueue_fork_copy_knote(struct kqueue *kq1, struct knote *kn, struct proc *p1,
    struct filedesc *fdp)
{
        struct knote *kn1;
        const struct filterops *fop;
        int error;

        fop = kn->kn_fop;
        if (fop->f_copy == NULL || (fop->f_isfd &&
            fdp->fd_files->fdt_ofiles[kn->kn_kevent.ident].fde_file == NULL))
                return;
        error = kqueue_expand(kq1, fop, kn->kn_kevent.ident, M_WAITOK);
        if (error != 0)
                return;

        kn1 = knote_alloc(M_WAITOK);
        *kn1 = *kn;
        kn1->kn_status |= KN_DETACHED;
        kn1->kn_status &= ~KN_QUEUED;
        kn1->kn_kq = kq1;
        kn1->kn_knlist = NULL;
        error = fop->f_copy(kn1, p1);
        if (error != 0) {
                knote_free(kn1);
                return;
        }
        (void)kqueue_fo_find(kn->kn_kevent.filter);
        if (fop->f_isfd && !fhold(kn1->kn_fp)) {
                fop->f_detach(kn1);
                kqueue_fo_release(kn->kn_kevent.filter);
                knote_free(kn1);
                return;
        }
        if (kn->kn_knlist != NULL)
                knlist_add(kn->kn_knlist, kn1, 0);
        KQ_LOCK(kq1);
        knote_attach(kn1, kq1);
        kn1->kn_influx = 0;
        if ((kn->kn_status & KN_QUEUED) != 0)
                knote_enqueue(kn1);
        KQ_UNLOCK(kq1);
}

static void
kqueue_fork_copy_list(struct klist *knlist, struct knote *marker,
    struct kqueue *kq, struct kqueue *kq1, struct proc *p1,
    struct filedesc *fdp)
{
        struct knote *kn;

        KQ_OWNED(kq);
        kn = SLIST_FIRST(knlist);
        while (kn != NULL) {
                MPASS(kn->kn_kq == kq);
                if ((kn->kn_status & KN_DETACHED) != 0 ||
                    (kn_in_flux(kn) && (kn->kn_status & KN_SCAN) == 0)) {
                        kn = SLIST_NEXT(kn, kn_link);
                        continue;
                }
                kn_enter_flux(kn);
                SLIST_INSERT_AFTER(kn, marker, kn_link);
                KQ_UNLOCK(kq);
                kqueue_fork_copy_knote(kq1, kn, p1, fdp);
                KQ_LOCK(kq);
                kn_leave_flux(kn);
                kn = SLIST_NEXT(marker, kn_link);
                /* XXXKIB switch kn_link to LIST? */
                SLIST_REMOVE(knlist, marker, knote, kn_link);
        }
}

static int
kqueue_fork_copy(struct filedesc *fdp, struct file *fp, struct file *fp1,
    struct proc *p1, struct thread *td)
{
        struct kqueue *kq, *kq1;
        struct knote *marker;
        int error, i;

        error = 0;
        MPASS(fp == NULL);
        MPASS(fp1->f_type == DTYPE_KQUEUE);

        kq1 = fp1->f_data;
        kq = kq1->kq_forksrc;
        marker = knote_alloc(M_WAITOK);
        marker->kn_status = KN_MARKER;
        marker->kn_kq = kq;

        KQ_LOCK(kq);
        for (i = 0; i < kq->kq_knlistsize; i++) {
                kqueue_fork_copy_list(&kq->kq_knlist[i], marker, kq, kq1,
                    p1, fdp);
        }
        if (kq->kq_knhashmask != 0) {
                for (i = 0; i <= kq->kq_knhashmask; i++) {
                        kqueue_fork_copy_list(&kq->kq_knhash[i], marker, kq,
                            kq1, p1, fdp);
                }
        }
        kqueue_release(kq, 1);
        kq1->kq_forksrc = NULL;
        KQ_UNLOCK_FLUX(kq);

        knote_free(marker);
        return (error);
}

static int
kqueue_fork(struct filedesc *fdp, struct file *fp, struct file **fp1,
    struct proc *p1, struct thread *td)
{
        if (*fp1 == NULL)
                return (kqueue_fork_alloc(fdp, fp, fp1, td));
        return (kqueue_fork_copy(fdp, fp, *fp1, p1, td));
}

int
knote_triv_copy(struct knote *kn __unused, struct proc *p1 __unused)
{
        return (0);
}

struct knote_status_export_bit {
        int kn_status_bit;
        int knt_status_bit;
};

#define ST(name) \
    { .kn_status_bit = KN_##name, .knt_status_bit = KNOTE_STATUS_##name }
static const struct knote_status_export_bit knote_status_export_bits[] = {
        ST(ACTIVE),
        ST(QUEUED),
        ST(DISABLED),
        ST(DETACHED),
        ST(KQUEUE),
};
#undef ST

static int
knote_status_export(int kn_status)
{
        const struct knote_status_export_bit *b;
        unsigned i;
        int res;

        res = 0;
        for (i = 0; i < nitems(knote_status_export_bits); i++) {
                b = &knote_status_export_bits[i];
                if ((kn_status & b->kn_status_bit) != 0)
                        res |= b->knt_status_bit;
        }
        return (res);
}

static int
kern_proc_kqueue_report_one(struct sbuf *s, struct proc *p,
    int kq_fd, struct kqueue *kq, struct knote *kn, bool compat32 __unused)
{
        struct kinfo_knote kin;
#ifdef COMPAT_FREEBSD32
        struct kinfo_knote32 kin32;
#endif
        int error;

        if (kn->kn_status == KN_MARKER)
                return (0);

        memset(&kin, 0, sizeof(kin));
        kin.knt_kq_fd = kq_fd;
        memcpy(&kin.knt_event, &kn->kn_kevent, sizeof(struct kevent));
        kin.knt_status = knote_status_export(kn->kn_status);
        kn_enter_flux(kn);
        KQ_UNLOCK_FLUX(kq);
        if (kn->kn_fop->f_userdump != NULL)
                (void)kn->kn_fop->f_userdump(p, kn, &kin);
#ifdef COMPAT_FREEBSD32
        if (compat32) {
                freebsd32_kinfo_knote_to_32(&kin, &kin32);
                error = sbuf_bcat(s, &kin32, sizeof(kin32));
        } else
#endif
                error = sbuf_bcat(s, &kin, sizeof(kin));
        KQ_LOCK(kq);
        kn_leave_flux(kn);
        return (error);
}

static int
kern_proc_kqueue_report(struct sbuf *s, struct proc *p, int kq_fd,
    struct kqueue *kq, bool compat32)
{
        struct knote *kn;
        int error, i;

        error = 0;
        KQ_LOCK(kq);
        for (i = 0; i < kq->kq_knlistsize; i++) {
                SLIST_FOREACH(kn, &kq->kq_knlist[i], kn_link) {
                        MPASS(kn->kn_kq == kq);
                        error = kern_proc_kqueue_report_one(s, p, kq_fd,
                            kq, kn, compat32);
                        if (error != 0)
                                goto out;
                }
        }
        if (kq->kq_knhashmask == 0)
                goto out;
        for (i = 0; i <= kq->kq_knhashmask; i++) {
                SLIST_FOREACH(kn, &kq->kq_knhash[i], kn_link) {
                        MPASS(kn->kn_kq == kq);
                        error = kern_proc_kqueue_report_one(s, p, kq_fd,
                            kq, kn, compat32);
                        if (error != 0)
                                goto out;
                }
        }
out:
        KQ_UNLOCK_FLUX(kq);
        return (error);
}

struct kern_proc_kqueues_out1_cb_args {
        struct sbuf *s;
        bool compat32;
};

static int
kern_proc_kqueues_out1_cb(struct proc *p, int fd, struct file *fp, void *arg)
{
        struct kqueue *kq;
        struct kern_proc_kqueues_out1_cb_args *a;

        if (fp->f_type != DTYPE_KQUEUE)
                return (0);
        a = arg;
        kq = fp->f_data;
        return (kern_proc_kqueue_report(a->s, p, fd, kq, a->compat32));
}

static int
kern_proc_kqueues_out1(struct thread *td, struct proc *p, struct sbuf *s,
    bool compat32)
{
        struct kern_proc_kqueues_out1_cb_args a;

        a.s = s;
        a.compat32 = compat32;
        return (fget_remote_foreach(td, p, kern_proc_kqueues_out1_cb, &a));
}

int
kern_proc_kqueues_out(struct proc *p, struct sbuf *sb, size_t maxlen,
    bool compat32)
{
        struct sbuf *s, sm;
        size_t sb_len;
        int error;

        if (maxlen == -1 || maxlen == 0)
                sb_len = 128;
        else
                sb_len = maxlen;
        s = sbuf_new(&sm, NULL, sb_len, maxlen == -1 ? SBUF_AUTOEXTEND :
            SBUF_FIXEDLEN);
        error = kern_proc_kqueues_out1(curthread, p, s, compat32);
        sbuf_finish(s);
        if (error == 0) {
                sbuf_bcat(sb, sbuf_data(s), MIN(sbuf_len(s), maxlen == -1 ?
                    SIZE_T_MAX : maxlen));
        }
        sbuf_delete(s);
        return (error);
}

static int
sysctl_kern_proc_kqueue_one(struct thread *td, struct sbuf *s, struct proc *p,
    int kq_fd, bool compat32)
{
        struct file *fp;
        struct kqueue *kq;
        int error;

        error = fget_remote(td, p, kq_fd, &fp);
        if (error == 0) {
                if (fp->f_type != DTYPE_KQUEUE) {
                        error = EINVAL;
                } else {
                        kq = fp->f_data;
                        error = kern_proc_kqueue_report(s, p, kq_fd, kq,
                            compat32);
                }
                fdrop(fp, td);
        }
        return (error);
}

static int
sysctl_kern_proc_kqueue(SYSCTL_HANDLER_ARGS)
{
        struct thread *td;
        struct proc *p;
        struct sbuf *s, sm;
        int error, error1, *name;
        bool compat32;

        name = (int *)arg1;
        if ((u_int)arg2 > 2 || (u_int)arg2 == 0)
                return (EINVAL);

        error = pget((pid_t)name[0], PGET_HOLD | PGET_CANDEBUG, &p);
        if (error != 0)
                return (error);

        td = curthread;
#ifdef COMPAT_FREEBSD32
        compat32 = SV_CURPROC_FLAG(SV_ILP32);
#else
        compat32 = false;
#endif

        s = sbuf_new_for_sysctl(&sm, NULL, 0, req);
        if (s == NULL) {
                error = ENOMEM;
                goto out;
        }
        sbuf_clear_flags(s, SBUF_INCLUDENUL);

        if ((u_int)arg2 == 1) {
                error = kern_proc_kqueues_out1(td, p, s, compat32);
        } else {
                error = sysctl_kern_proc_kqueue_one(td, s, p,
                    name[1] /* kq_fd */, compat32);
        }

        error1 = sbuf_finish(s);
        if (error == 0)
                error = error1;
        sbuf_delete(s);

out:
        PRELE(p);
        return (error);
}

static SYSCTL_NODE(_kern_proc, KERN_PROC_KQUEUE, kq,
    CTLFLAG_RD | CTLFLAG_MPSAFE,
    sysctl_kern_proc_kqueue, "KQueue events");