/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2000-2004
 *      Poul-Henning Kamp.  All rights reserved.
 * Copyright (c) 1989, 1992-1993, 1995
 *      The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software donated to Berkeley by
 * Jan-Simon Pendry.
 *
 * 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. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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.
 * From: FreeBSD: src/sys/miscfs/kernfs/kernfs_vnops.c 1.43
 */

/*
 * TODO:
 *      mkdir: want it ?
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/conf.h>
#include <sys/dirent.h>
#include <sys/eventhandler.h>
#include <sys/fcntl.h>
#include <sys/file.h>
#include <sys/filedesc.h>
#include <sys/filio.h>
#include <sys/jail.h>
#include <sys/kernel.h>
#include <sys/limits.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/mman.h>
#include <sys/mount.h>
#include <sys/namei.h>
#include <sys/priv.h>
#include <sys/proc.h>
#include <sys/stat.h>
#include <sys/sx.h>
#include <sys/sysctl.h>
#include <sys/time.h>
#include <sys/ttycom.h>
#include <sys/unistd.h>
#include <sys/vnode.h>

static struct vop_vector devfs_vnodeops;
static struct vop_vector devfs_specops;
static const struct fileops devfs_ops_f;

#include <fs/devfs/devfs.h>
#include <fs/devfs/devfs_int.h>

#include <security/mac/mac_framework.h>

#include <vm/vm.h>
#include <vm/vm_extern.h>
#include <vm/vm_object.h>

static MALLOC_DEFINE(M_CDEVPDATA, "DEVFSP", "Metainfo for cdev-fp data");

struct mtx      devfs_de_interlock;
MTX_SYSINIT(devfs_de_interlock, &devfs_de_interlock, "devfs interlock", MTX_DEF);
struct mtx      cdevpriv_mtx;
MTX_SYSINIT(cdevpriv_mtx, &cdevpriv_mtx, "cdevpriv lock", MTX_DEF);

SYSCTL_DECL(_vfs_devfs);

static int devfs_dotimes;
SYSCTL_INT(_vfs_devfs, OID_AUTO, dotimes, CTLFLAG_RW,
    &devfs_dotimes, 0, "Update timestamps on DEVFS with default precision");

/*
 * Update devfs node timestamp.  Note that updates are unlocked and
 * stat(2) could see partially updated times.
 */
static void
devfs_timestamp(struct timespec *tsp)
{
        time_t ts;

        if (devfs_dotimes) {
                vfs_timestamp(tsp);
        } else {
                ts = time_second;
                if (tsp->tv_sec != ts) {
                        tsp->tv_sec = ts;
                        tsp->tv_nsec = 0;
                }
        }
}

static int
devfs_fp_check(struct file *fp, struct cdev **devp, struct cdevsw **dswp,
    int *ref)
{
        *dswp = devvn_refthread(fp->f_vnode, devp, ref);
        if (*dswp == NULL || *devp != fp->f_data) {
                if (*dswp != NULL)
                        dev_relthread(*devp, *ref);
                return (ENXIO);
        }
        KASSERT((*devp)->si_refcount > 0,
            ("devfs: un-referenced struct cdev *(%s)", devtoname(*devp)));
        if (*dswp == NULL)
                return (ENXIO);
        curthread->td_fpop = fp;
        return (0);
}

int
devfs_get_cdevpriv(void **datap)
{
        struct file *fp;
        struct cdev_privdata *p;
        int error;

        fp = curthread->td_fpop;
        if (fp == NULL)
                return (EBADF);
        p = fp->f_cdevpriv;
        if (p != NULL) {
                error = 0;
                *datap = p->cdpd_data;
        } else
                error = ENOENT;
        return (error);
}

int
devfs_set_cdevpriv(void *priv, d_priv_dtor_t *priv_dtr)
{
        struct file *fp;
        struct cdev_priv *cdp;
        struct cdev_privdata *p;
        int error;

        fp = curthread->td_fpop;
        if (fp == NULL)
                return (ENOENT);
        cdp = cdev2priv((struct cdev *)fp->f_data);
        p = malloc(sizeof(struct cdev_privdata), M_CDEVPDATA, M_WAITOK);
        p->cdpd_data = priv;
        p->cdpd_dtr = priv_dtr;
        p->cdpd_fp = fp;
        mtx_lock(&cdevpriv_mtx);
        if (fp->f_cdevpriv == NULL) {
                LIST_INSERT_HEAD(&cdp->cdp_fdpriv, p, cdpd_list);
                fp->f_cdevpriv = p;
                mtx_unlock(&cdevpriv_mtx);
                error = 0;
        } else {
                mtx_unlock(&cdevpriv_mtx);
                free(p, M_CDEVPDATA);
                error = EBUSY;
        }
        return (error);
}

int
devfs_foreach_cdevpriv(struct cdev *dev, int (*cb)(void *data, void *arg),
    void *arg)
{
        struct cdev_priv *cdp;
        struct cdev_privdata *p;
        int error;

        cdp = cdev2priv(dev);
        error = 0;
        mtx_lock(&cdevpriv_mtx);
        LIST_FOREACH(p, &cdp->cdp_fdpriv, cdpd_list) {
                error = cb(p->cdpd_data, arg);
                if (error != 0)
                        break;
        }
        mtx_unlock(&cdevpriv_mtx);
        return (error);
}

void
devfs_destroy_cdevpriv(struct cdev_privdata *p)
{
        struct file *fp;
        struct cdev_priv *cdp;

        mtx_assert(&cdevpriv_mtx, MA_OWNED);
        fp = p->cdpd_fp;
        KASSERT(fp->f_cdevpriv == p,
            ("devfs_destoy_cdevpriv %p != %p", fp->f_cdevpriv, p));
        cdp = cdev2priv((struct cdev *)fp->f_data);
        cdp->cdp_fdpriv_dtrc++;
        fp->f_cdevpriv = NULL;
        LIST_REMOVE(p, cdpd_list);
        mtx_unlock(&cdevpriv_mtx);
        (p->cdpd_dtr)(p->cdpd_data);
        mtx_lock(&cdevpriv_mtx);
        MPASS(cdp->cdp_fdpriv_dtrc >= 1);
        cdp->cdp_fdpriv_dtrc--;
        if (cdp->cdp_fdpriv_dtrc == 0)
                wakeup(&cdp->cdp_fdpriv_dtrc);
        mtx_unlock(&cdevpriv_mtx);
        free(p, M_CDEVPDATA);
}

static void
devfs_fpdrop(struct file *fp)
{
        struct cdev_privdata *p;

        mtx_lock(&cdevpriv_mtx);
        if ((p = fp->f_cdevpriv) == NULL) {
                mtx_unlock(&cdevpriv_mtx);
                return;
        }
        devfs_destroy_cdevpriv(p);
}

void
devfs_clear_cdevpriv(void)
{
        struct file *fp;

        fp = curthread->td_fpop;
        if (fp == NULL)
                return;
        devfs_fpdrop(fp);
}

static void
devfs_usecount_add(struct vnode *vp)
{
        struct devfs_dirent *de;
        struct cdev *dev;

        mtx_lock(&devfs_de_interlock);
        VI_LOCK(vp);
        VNPASS(vp->v_type == VCHR || vp->v_type == VBAD, vp);
        if (VN_IS_DOOMED(vp)) {
                goto out_unlock;
        }

        de = vp->v_data;
        dev = vp->v_rdev;
        MPASS(de != NULL);
        MPASS(dev != NULL);
        dev->si_usecount++;
        de->de_usecount++;
out_unlock:
        VI_UNLOCK(vp);
        mtx_unlock(&devfs_de_interlock);
}

static void
devfs_usecount_subl(struct vnode *vp)
{
        struct devfs_dirent *de;
        struct cdev *dev;

        mtx_assert(&devfs_de_interlock, MA_OWNED);
        ASSERT_VI_LOCKED(vp, __func__);
        VNPASS(vp->v_type == VCHR || vp->v_type == VBAD, vp);

        de = vp->v_data;
        dev = vp->v_rdev;
        if (de == NULL)
                return;
        if (dev == NULL) {
                MPASS(de->de_usecount == 0);
                return;
        }
        if (dev->si_usecount < de->de_usecount)
                panic("%s: si_usecount underflow for dev %p "
                    "(has %ld, dirent has %d)\n",
                    __func__, dev, dev->si_usecount, de->de_usecount);
        if (VN_IS_DOOMED(vp)) {
                dev->si_usecount -= de->de_usecount;
                de->de_usecount = 0;
        } else {
                if (de->de_usecount == 0)
                        panic("%s: de_usecount underflow for dev %p\n",
                            __func__, dev);
                dev->si_usecount--;
                de->de_usecount--;
        }
}

static void
devfs_usecount_sub(struct vnode *vp)
{

        mtx_lock(&devfs_de_interlock);
        VI_LOCK(vp);
        devfs_usecount_subl(vp);
        VI_UNLOCK(vp);
        mtx_unlock(&devfs_de_interlock);
}

static int
devfs_usecountl(struct vnode *vp)
{

        VNPASS(vp->v_type == VCHR, vp);
        mtx_assert(&devfs_de_interlock, MA_OWNED);
        ASSERT_VI_LOCKED(vp, __func__);
        return (vp->v_rdev->si_usecount);
}

int
devfs_usecount(struct vnode *vp)
{
        int count;

        VNPASS(vp->v_type == VCHR, vp);
        mtx_lock(&devfs_de_interlock);
        VI_LOCK(vp);
        count = devfs_usecountl(vp);
        VI_UNLOCK(vp);
        mtx_unlock(&devfs_de_interlock);
        return (count);
}

void
devfs_ctty_ref(struct vnode *vp)
{

        vrefact(vp);
        devfs_usecount_add(vp);
}

void
devfs_ctty_unref(struct vnode *vp)
{

        devfs_usecount_sub(vp);
        vrele(vp);
}

/*
 * On success devfs_populate_vp() returns with dmp->dm_lock held.
 */
static int
devfs_populate_vp(struct vnode *vp)
{
        struct devfs_dirent *de;
        struct devfs_mount *dmp;
        int locked;

        ASSERT_VOP_LOCKED(vp, "devfs_populate_vp");

        if (VN_IS_DOOMED(vp))
                return (ENOENT);

        dmp = VFSTODEVFS(vp->v_mount);
        if (!devfs_populate_needed(dmp)) {
                sx_xlock(&dmp->dm_lock);
                goto out_nopopulate;
        }

        locked = VOP_ISLOCKED(vp);

        sx_xlock(&dmp->dm_lock);
        DEVFS_DMP_HOLD(dmp);

        /* Can't call devfs_populate() with the vnode lock held. */
        VOP_UNLOCK(vp);
        devfs_populate(dmp);

        sx_xunlock(&dmp->dm_lock);
        vn_lock(vp, locked | LK_RETRY);
        sx_xlock(&dmp->dm_lock);
        if (DEVFS_DMP_DROP(dmp)) {
                sx_xunlock(&dmp->dm_lock);
                devfs_unmount_final(dmp);
                return (ERESTART);
        }
out_nopopulate:
        if (VN_IS_DOOMED(vp)) {
                sx_xunlock(&dmp->dm_lock);
                return (ERESTART);
        }
        de = vp->v_data;
        KASSERT(de != NULL,
            ("devfs_populate_vp: vp->v_data == NULL but vnode not doomed"));
        if ((de->de_flags & DE_DOOMED) != 0) {
                sx_xunlock(&dmp->dm_lock);
                return (ERESTART);
        }

        return (0);
}

static int
devfs_vptocnp(struct vop_vptocnp_args *ap)
{
        struct vnode *vp = ap->a_vp;
        struct vnode **dvp = ap->a_vpp;
        struct devfs_mount *dmp;
        char *buf = ap->a_buf;
        size_t *buflen = ap->a_buflen;
        struct devfs_dirent *dd, *de;
        int i, error;

        dmp = VFSTODEVFS(vp->v_mount);

        error = devfs_populate_vp(vp);
        if (error != 0)
                return (error);

        if (vp->v_type != VCHR && vp->v_type != VDIR) {
                error = ENOENT;
                goto finished;
        }

        dd = vp->v_data;
        if (vp->v_type == VDIR && dd == dmp->dm_rootdir) {
                *dvp = vp;
                vref(*dvp);
                goto finished;
        }

        i = *buflen;
        i -= dd->de_dirent->d_namlen;
        if (i < 0) {
                error = ENOMEM;
                goto finished;
        }
        bcopy(dd->de_dirent->d_name, buf + i, dd->de_dirent->d_namlen);
        *buflen = i;
        de = devfs_parent_dirent(dd);
        if (de == NULL) {
                error = ENOENT;
                goto finished;
        }
        mtx_lock(&devfs_de_interlock);
        *dvp = de->de_vnode;
        if (*dvp != NULL) {
                VI_LOCK(*dvp);
                mtx_unlock(&devfs_de_interlock);
                vholdl(*dvp);
                VI_UNLOCK(*dvp);
                vref(*dvp);
                vdrop(*dvp);
        } else {
                mtx_unlock(&devfs_de_interlock);
                error = ENOENT;
        }
finished:
        sx_xunlock(&dmp->dm_lock);
        return (error);
}

/*
 * Construct the fully qualified path name relative to the mountpoint.
 * If a NULL cnp is provided, no '/' is appended to the resulting path.
 */
char *
devfs_fqpn(char *buf, struct devfs_mount *dmp, struct devfs_dirent *dd,
    struct componentname *cnp)
{
        int i;
        struct devfs_dirent *de;

        sx_assert(&dmp->dm_lock, SA_LOCKED);

        i = SPECNAMELEN;
        buf[i] = '\0';
        if (cnp != NULL)
                i -= cnp->cn_namelen;
        if (i < 0)
                 return (NULL);
        if (cnp != NULL)
                bcopy(cnp->cn_nameptr, buf + i, cnp->cn_namelen);
        de = dd;
        while (de != dmp->dm_rootdir) {
                if (cnp != NULL || i < SPECNAMELEN) {
                        i--;
                        if (i < 0)
                                 return (NULL);
                        buf[i] = '/';
                }
                i -= de->de_dirent->d_namlen;
                if (i < 0)
                         return (NULL);
                bcopy(de->de_dirent->d_name, buf + i,
                    de->de_dirent->d_namlen);
                de = devfs_parent_dirent(de);
                if (de == NULL)
                        return (NULL);
        }
        return (buf + i);
}

static int
devfs_allocv_drop_refs(int drop_dm_lock, struct devfs_mount *dmp,
        struct devfs_dirent *de)
{
        int not_found;

        not_found = 0;
        if (de->de_flags & DE_DOOMED)
                not_found = 1;
        if (DEVFS_DE_DROP(de)) {
                KASSERT(not_found == 1, ("DEVFS de dropped but not doomed"));
                devfs_dirent_free(de);
        }
        if (DEVFS_DMP_DROP(dmp)) {
                KASSERT(not_found == 1,
                        ("DEVFS mount struct freed before dirent"));
                not_found = 2;
                sx_xunlock(&dmp->dm_lock);
                devfs_unmount_final(dmp);
        }
        if (not_found == 1 || (drop_dm_lock && not_found != 2))
                sx_unlock(&dmp->dm_lock);
        return (not_found);
}

/*
 * devfs_allocv shall be entered with dmp->dm_lock held, and it drops
 * it on return.
 */
int
devfs_allocv(struct devfs_dirent *de, struct mount *mp, int lockmode,
    struct vnode **vpp)
{
        int error;
        struct vnode *vp;
        struct cdev *dev;
        struct devfs_mount *dmp;
        struct cdevsw *dsw;
        enum vgetstate vs;

        dmp = VFSTODEVFS(mp);
        if (de->de_flags & DE_DOOMED) {
                sx_xunlock(&dmp->dm_lock);
                return (ENOENT);
        }
loop:
        DEVFS_DE_HOLD(de);
        DEVFS_DMP_HOLD(dmp);
        mtx_lock(&devfs_de_interlock);
        vp = de->de_vnode;
        if (vp != NULL) {
                vs = vget_prep(vp);
                mtx_unlock(&devfs_de_interlock);
                sx_xunlock(&dmp->dm_lock);
                vget_finish(vp, lockmode | LK_RETRY, vs);
                sx_xlock(&dmp->dm_lock);
                if (devfs_allocv_drop_refs(0, dmp, de)) {
                        vput(vp);
                        return (ENOENT);
                } else if (VN_IS_DOOMED(vp)) {
                        mtx_lock(&devfs_de_interlock);
                        if (de->de_vnode == vp) {
                                de->de_vnode = NULL;
                                vp->v_data = NULL;
                        }
                        mtx_unlock(&devfs_de_interlock);
                        vput(vp);
                        goto loop;
                }
                sx_xunlock(&dmp->dm_lock);
                *vpp = vp;
                return (0);
        }
        mtx_unlock(&devfs_de_interlock);
        if (de->de_dirent->d_type == DT_CHR) {
                if (!(de->de_cdp->cdp_flags & CDP_ACTIVE)) {
                        devfs_allocv_drop_refs(1, dmp, de);
                        return (ENOENT);
                }
                dev = &de->de_cdp->cdp_c;
        } else {
                dev = NULL;
        }
        error = getnewvnode("devfs", mp, &devfs_vnodeops, &vp);
        if (error != 0) {
                devfs_allocv_drop_refs(1, dmp, de);
                printf("devfs_allocv: failed to allocate new vnode\n");
                return (error);
        }

        if (de->de_dirent->d_type == DT_CHR) {
                vp->v_type = VCHR;
                VI_LOCK(vp);
                dev_lock();
                dev_refl(dev);
                /* XXX: v_rdev should be protect by vnode lock */
                vp->v_rdev = dev;
                VNPASS(vp->v_usecount == 1, vp);
                /* Special casing of ttys for deadfs.  Probably redundant. */
                dsw = dev->si_devsw;
                if (dsw != NULL && (dsw->d_flags & D_TTY) != 0)
                        vp->v_vflag |= VV_ISTTY;
                dev_unlock();
                VI_UNLOCK(vp);
                if ((dev->si_flags & SI_ETERNAL) != 0)
                        vp->v_vflag |= VV_ETERNALDEV;
                vp->v_op = &devfs_specops;
        } else if (de->de_dirent->d_type == DT_DIR) {
                vp->v_type = VDIR;
        } else if (de->de_dirent->d_type == DT_LNK) {
                vp->v_type = VLNK;
        } else {
                vp->v_type = VBAD;
        }
        vn_lock(vp, LK_EXCLUSIVE | LK_RETRY | LK_NOWITNESS);
        VN_LOCK_ASHARE(vp);
        mtx_lock(&devfs_de_interlock);
        vp->v_data = de;
        de->de_vnode = vp;
        mtx_unlock(&devfs_de_interlock);
        error = insmntque1(vp, mp);
        if (error != 0) {
                mtx_lock(&devfs_de_interlock);
                vp->v_data = NULL;
                de->de_vnode = NULL;
                mtx_unlock(&devfs_de_interlock);
                vgone(vp);
                vput(vp);
                (void) devfs_allocv_drop_refs(1, dmp, de);
                return (error);
        }
        if (devfs_allocv_drop_refs(0, dmp, de)) {
                vgone(vp);
                vput(vp);
                return (ENOENT);
        }
#ifdef MAC
        mac_devfs_vnode_associate(mp, de, vp);
#endif
        sx_xunlock(&dmp->dm_lock);
        vn_set_state(vp, VSTATE_CONSTRUCTED);
        *vpp = vp;
        return (0);
}

static int
devfs_access(struct vop_access_args *ap)
{
        struct vnode *vp = ap->a_vp;
        struct devfs_dirent *de;
        struct proc *p;
        int error;

        de = vp->v_data;
        if (vp->v_type == VDIR)
                de = de->de_dir;

        error = vaccess(vp->v_type, de->de_mode, de->de_uid, de->de_gid,
            ap->a_accmode, ap->a_cred);
        if (error == 0)
                return (0);
        if (error != EACCES)
                return (error);
        p = ap->a_td->td_proc;
        /* We do, however, allow access to the controlling terminal */
        PROC_LOCK(p);
        if (!(p->p_flag & P_CONTROLT)) {
                PROC_UNLOCK(p);
                return (error);
        }
        if (p->p_session->s_ttydp == de->de_cdp)
                error = 0;
        PROC_UNLOCK(p);
        return (error);
}

_Static_assert(((FMASK | FCNTLFLAGS) & (FLASTCLOSE | FREVOKE)) == 0,
    "devfs-only flag reuse failed");

static int
devfs_close(struct vop_close_args *ap)
{
        struct vnode *vp = ap->a_vp, *oldvp;
        struct thread *td = ap->a_td;
        struct proc *p;
        struct cdev *dev = vp->v_rdev;
        struct cdevsw *dsw;
        struct devfs_dirent *de = vp->v_data;
        int dflags, error, ref, vp_locked;

        /*
         * XXX: Don't call d_close() if we were called because of
         * XXX: insmntque() failure.
         */
        if (vp->v_data == NULL)
                return (0);

        /*
         * Hack: a tty device that is a controlling terminal
         * has a reference from the session structure.
         * We cannot easily tell that a character device is
         * a controlling terminal, unless it is the closing
         * process' controlling terminal.  In that case,
         * if the reference count is 2 (this last descriptor
         * plus the session), release the reference from the session.
         */
        if (de->de_usecount == 2 && td != NULL) {
                p = td->td_proc;
                PROC_LOCK(p);
                if (vp == p->p_session->s_ttyvp) {
                        PROC_UNLOCK(p);
                        oldvp = NULL;
                        sx_xlock(&proctree_lock);
                        if (vp == p->p_session->s_ttyvp) {
                                SESS_LOCK(p->p_session);
                                mtx_lock(&devfs_de_interlock);
                                VI_LOCK(vp);
                                if (devfs_usecountl(vp) == 2 && !VN_IS_DOOMED(vp)) {
                                        p->p_session->s_ttyvp = NULL;
                                        p->p_session->s_ttydp = NULL;
                                        oldvp = vp;
                                }
                                VI_UNLOCK(vp);
                                mtx_unlock(&devfs_de_interlock);
                                SESS_UNLOCK(p->p_session);
                        }
                        sx_xunlock(&proctree_lock);
                        if (oldvp != NULL)
                                devfs_ctty_unref(oldvp);
                } else
                        PROC_UNLOCK(p);
        }
        /*
         * We do not want to really close the device if it
         * is still in use unless we are trying to close it
         * forcibly. Since every use (buffer, vnode, swap, cmap)
         * holds a reference to the vnode, and because we mark
         * any other vnodes that alias this device, when the
         * sum of the reference counts on all the aliased
         * vnodes descends to one, we are on last close.
         */
        dsw = dev_refthread(dev, &ref);
        if (dsw == NULL)
                return (ENXIO);
        dflags = 0;
        mtx_lock(&devfs_de_interlock);
        VI_LOCK(vp);
        if (devfs_usecountl(vp) == 1)
                dflags |= FLASTCLOSE;
        devfs_usecount_subl(vp);
        mtx_unlock(&devfs_de_interlock);
        if (VN_IS_DOOMED(vp)) {
                /* Forced close. */
                dflags |= FREVOKE | FNONBLOCK;
        } else if (dsw->d_flags & D_TRACKCLOSE) {
                /* Keep device updated on status. */
        } else if ((dflags & FLASTCLOSE) == 0) {
                VI_UNLOCK(vp);
                dev_relthread(dev, ref);
                return (0);
        }
        vholdnz(vp);
        VI_UNLOCK(vp);
        vp_locked = VOP_ISLOCKED(vp);
        VOP_UNLOCK(vp);
        KASSERT(dev->si_refcount > 0,
            ("devfs_close() on un-referenced struct cdev *(%s)", devtoname(dev)));
        error = dsw->d_close(dev, ap->a_fflag | dflags, S_IFCHR, td);
        dev_relthread(dev, ref);
        vn_lock(vp, vp_locked | LK_RETRY);
        vdrop(vp);
        return (error);
}

static int
devfs_close_f(struct file *fp, struct thread *td)
{
        int error;
        struct file *fpop;

        /*
         * NB: td may be NULL if this descriptor is closed due to
         * garbage collection from a closed UNIX domain socket.
         */
        fpop = curthread->td_fpop;
        curthread->td_fpop = fp;
        error = vnops.fo_close(fp, td);
        curthread->td_fpop = fpop;

        /*
         * The f_cdevpriv cannot be assigned non-NULL value while we
         * are destroying the file.
         */
        if (fp->f_cdevpriv != NULL)
                devfs_fpdrop(fp);
        return (error);
}

static int
devfs_getattr(struct vop_getattr_args *ap)
{
        struct vnode *vp = ap->a_vp;
        struct vattr *vap = ap->a_vap;
        struct devfs_dirent *de;
        struct devfs_mount *dmp;
        struct cdev *dev;
        struct timeval boottime;
        int error;

        error = devfs_populate_vp(vp);
        if (error != 0)
                return (error);

        dmp = VFSTODEVFS(vp->v_mount);
        sx_xunlock(&dmp->dm_lock);

        de = vp->v_data;
        KASSERT(de != NULL, ("Null dirent in devfs_getattr vp=%p", vp));
        if (vp->v_type == VDIR) {
                de = de->de_dir;
                KASSERT(de != NULL,
                    ("Null dir dirent in devfs_getattr vp=%p", vp));
        }
        vap->va_uid = de->de_uid;
        vap->va_gid = de->de_gid;
        vap->va_mode = de->de_mode;
        if (vp->v_type == VLNK)
                vap->va_size = strlen(de->de_symlink);
        else if (vp->v_type == VDIR)
                vap->va_size = vap->va_bytes = DEV_BSIZE;
        else
                vap->va_size = 0;
        if (vp->v_type != VDIR)
                vap->va_bytes = 0;
        vap->va_blocksize = DEV_BSIZE;
        vap->va_type = vp->v_type;

        getboottime(&boottime);
#define fix(aa)                                                 \
        do {                                                    \
                if ((aa).tv_sec <= 3600) {                      \
                        (aa).tv_sec = boottime.tv_sec;          \
                        (aa).tv_nsec = boottime.tv_usec * 1000; \
                }                                               \
        } while (0)

        if (vp->v_type != VCHR)  {
                fix(de->de_atime);
                vap->va_atime = de->de_atime;
                fix(de->de_mtime);
                vap->va_mtime = de->de_mtime;
                fix(de->de_ctime);
                vap->va_ctime = de->de_ctime;
        } else {
                dev = vp->v_rdev;
                fix(dev->si_atime);
                vap->va_atime = dev->si_atime;
                fix(dev->si_mtime);
                vap->va_mtime = dev->si_mtime;
                fix(dev->si_ctime);
                vap->va_ctime = dev->si_ctime;

                vap->va_rdev = cdev2priv(dev)->cdp_inode;
        }
        vap->va_gen = 0;
        vap->va_flags = 0;
        vap->va_filerev = 0;
        vap->va_nlink = de->de_links;
        vap->va_fileid = de->de_inode;

        return (error);
}

/* ARGSUSED */
static int
devfs_ioctl_f(struct file *fp, u_long com, void *data, struct ucred *cred, struct thread *td)
{
        struct file *fpop;
        int error;

        fpop = td->td_fpop;
        td->td_fpop = fp;
        error = vnops.fo_ioctl(fp, com, data, cred, td);
        td->td_fpop = fpop;
        return (error);
}

void *
fiodgname_buf_get_ptr(void *fgnp, u_long com)
{
        union {
                struct fiodgname_arg    fgn;
#ifdef COMPAT_FREEBSD32
                struct fiodgname_arg32  fgn32;
#endif
        } *fgnup;

        fgnup = fgnp;
        switch (com) {
        case FIODGNAME:
                return (fgnup->fgn.buf);
#ifdef COMPAT_FREEBSD32
        case FIODGNAME_32:
                return ((void *)(uintptr_t)fgnup->fgn32.buf);
#endif
        default:
                panic("Unhandled ioctl command %ld", com);
        }
}

static int
devfs_ioctl(struct vop_ioctl_args *ap)
{
        struct fiodgname_arg *fgn;
        struct vnode *vpold, *vp;
        struct cdevsw *dsw;
        struct thread *td;
        struct session *sess;
        struct cdev *dev;
        int error, ref, i;
        const char *p;
        u_long com;

        vp = ap->a_vp;
        com = ap->a_command;
        td = ap->a_td;

        dsw = devvn_refthread(vp, &dev, &ref);
        if (dsw == NULL)
                return (ENXIO);
        KASSERT(dev->si_refcount > 0,
            ("devfs: un-referenced struct cdev *(%s)", devtoname(dev)));

        switch (com) {
        case FIODTYPE:
                *(int *)ap->a_data = dsw->d_flags & D_TYPEMASK;
                error = 0;
                break;
        case FIODGNAME:
#ifdef  COMPAT_FREEBSD32
        case FIODGNAME_32:
#endif
                fgn = ap->a_data;
                p = devtoname(dev);
                i = strlen(p) + 1;
                if (i > fgn->len)
                        error = EINVAL;
                else
                        error = copyout(p, fiodgname_buf_get_ptr(fgn, com), i);
                break;
        default:
                error = dsw->d_ioctl(dev, com, ap->a_data, ap->a_fflag, td);
        }

        dev_relthread(dev, ref);
        if (error == ENOIOCTL)
                error = ENOTTY;

        if (error == 0 && com == TIOCSCTTY) {
                /*
                 * Do nothing if reassigning same control tty, or if the
                 * control tty has already disappeared.  If it disappeared,
                 * it's because we were racing with TIOCNOTTY.  TIOCNOTTY
                 * already took care of releasing the old vnode and we have
                 * nothing left to do.
                 */
                sx_slock(&proctree_lock);
                sess = td->td_proc->p_session;
                if (sess->s_ttyvp == vp || sess->s_ttyp == NULL) {
                        sx_sunlock(&proctree_lock);
                        return (0);
                }

                devfs_ctty_ref(vp);
                SESS_LOCK(sess);
                vpold = sess->s_ttyvp;
                sess->s_ttyvp = vp;
                sess->s_ttydp = cdev2priv(dev);
                SESS_UNLOCK(sess);

                sx_sunlock(&proctree_lock);

                /* Get rid of reference to old control tty */
                if (vpold)
                        devfs_ctty_unref(vpold);
        }
        return (error);
}

/* ARGSUSED */
static int
devfs_kqfilter_f(struct file *fp, struct knote *kn)
{
        struct cdev *dev;
        struct cdevsw *dsw;
        int error, ref;
        struct file *fpop;
        struct thread *td;

        td = curthread;
        fpop = td->td_fpop;
        error = devfs_fp_check(fp, &dev, &dsw, &ref);
        if (error)
                return (error);
        error = dsw->d_kqfilter(dev, kn);
        td->td_fpop = fpop;
        dev_relthread(dev, ref);
        return (error);
}

static inline int
devfs_prison_check(struct devfs_dirent *de, struct thread *td)
{
        struct cdev_priv *cdp;
        struct ucred *dcr;
        struct proc *p;
        int error;

        cdp = de->de_cdp;
        if (cdp == NULL)
                return (0);
        dcr = cdp->cdp_c.si_cred;
        if (dcr == NULL)
                return (0);

        error = prison_check(td->td_ucred, dcr);
        if (error == 0)
                return (0);
        /* We do, however, allow access to the controlling terminal */
        p = td->td_proc;
        PROC_LOCK(p);
        if (!(p->p_flag & P_CONTROLT)) {
                PROC_UNLOCK(p);
                return (error);
        }
        if (p->p_session->s_ttydp == cdp)
                error = 0;
        PROC_UNLOCK(p);
        return (error);
}

static int
devfs_lookupx(struct vop_lookup_args *ap, int *dm_unlock)
{
        struct componentname *cnp;
        struct vnode *dvp, **vpp;
        struct thread *td;
        struct devfs_dirent *de, *dd;
        struct devfs_dirent **dde;
        struct devfs_mount *dmp;
        struct mount *mp;
        struct cdev *cdev;
        int error, flags, nameiop, dvplocked;
        char specname[SPECNAMELEN + 1], *pname;

        td = curthread;
        cnp = ap->a_cnp;
        vpp = ap->a_vpp;
        dvp = ap->a_dvp;
        pname = cnp->cn_nameptr;
        flags = cnp->cn_flags;
        nameiop = cnp->cn_nameiop;
        mp = dvp->v_mount;
        dmp = VFSTODEVFS(mp);
        dd = dvp->v_data;
        *vpp = NULL;

        if ((flags & ISLASTCN) && nameiop == RENAME)
                return (EOPNOTSUPP);

        if (dvp->v_type != VDIR)
                return (ENOTDIR);

        if ((flags & ISDOTDOT) && (dvp->v_vflag & VV_ROOT))
                return (EIO);

        error = vn_dir_check_exec(dvp, cnp);
        if (error != 0)
                return (error);

        if (cnp->cn_namelen == 1 && *pname == '.') {
                if ((flags & ISLASTCN) && nameiop != LOOKUP)
                        return (EINVAL);
                *vpp = dvp;
                vref(dvp);
                return (0);
        }

        if (flags & ISDOTDOT) {
                if ((flags & ISLASTCN) && nameiop != LOOKUP)
                        return (EINVAL);
                de = devfs_parent_dirent(dd);
                if (de == NULL)
                        return (ENOENT);
                dvplocked = VOP_ISLOCKED(dvp);
                VOP_UNLOCK(dvp);
                error = devfs_allocv(de, mp, cnp->cn_lkflags & LK_TYPE_MASK,
                    vpp);
                *dm_unlock = 0;
                vn_lock(dvp, dvplocked | LK_RETRY);
                return (error);
        }

        dd = dvp->v_data;
        de = devfs_find(dd, cnp->cn_nameptr, cnp->cn_namelen, 0);
        while (de == NULL) {    /* While(...) so we can use break */

                if (nameiop == DELETE)
                        return (ENOENT);

                /*
                 * OK, we didn't have an entry for the name we were asked for
                 * so we try to see if anybody can create it on demand.
                 */
                pname = devfs_fqpn(specname, dmp, dd, cnp);
                if (pname == NULL)
                        break;

                cdev = NULL;
                DEVFS_DMP_HOLD(dmp);
                sx_xunlock(&dmp->dm_lock);
                dvplocked = VOP_ISLOCKED(dvp);

                /*
                 * Invoke the dev_clone handler.  Unlock dvp around it
                 * to simplify the cloner operations.
                 *
                 * If dvp is reclaimed while we unlocked it, we return
                 * with ENOENT by some of the paths below.  If cloner
                 * returned cdev, then devfs_populate_vp() notes the
                 * reclamation.  Otherwise, note that either our devfs
                 * mount is being unmounted, then DEVFS_DMP_DROP()
                 * returns true, and we return ENOENT this way.  Or,
                 * because de == NULL, the check for it after the loop
                 * returns ENOENT.
                 */
                VOP_UNLOCK(dvp);
                EVENTHANDLER_INVOKE(dev_clone,
                    td->td_ucred, pname, strlen(pname), &cdev);
                vn_lock(dvp, dvplocked | LK_RETRY);

                if (cdev == NULL)
                        sx_xlock(&dmp->dm_lock);
                else if (devfs_populate_vp(dvp) != 0) {
                        *dm_unlock = 0;
                        sx_xlock(&dmp->dm_lock);
                        if (DEVFS_DMP_DROP(dmp)) {
                                sx_xunlock(&dmp->dm_lock);
                                devfs_unmount_final(dmp);
                        } else
                                sx_xunlock(&dmp->dm_lock);
                        dev_rel(cdev);
                        return (ENOENT);
                }
                if (DEVFS_DMP_DROP(dmp)) {
                        *dm_unlock = 0;
                        sx_xunlock(&dmp->dm_lock);
                        devfs_unmount_final(dmp);
                        if (cdev != NULL)
                                dev_rel(cdev);
                        return (ENOENT);
                }

                if (cdev == NULL)
                        break;

                dev_lock();
                dde = &cdev2priv(cdev)->cdp_dirents[dmp->dm_idx];
                if (dde != NULL && *dde != NULL)
                        de = *dde;
                dev_unlock();
                dev_rel(cdev);
                break;
        }

        if (de == NULL || de->de_flags & DE_WHITEOUT) {
                if ((nameiop == CREATE || nameiop == RENAME) &&
                    (flags & (LOCKPARENT | WANTPARENT)) && (flags & ISLASTCN)) {
                        return (EJUSTRETURN);
                }
                return (ENOENT);
        }

        if (devfs_prison_check(de, td))
                return (ENOENT);

        if ((cnp->cn_nameiop == DELETE) && (flags & ISLASTCN)) {
                error = VOP_ACCESS(dvp, VWRITE, cnp->cn_cred, td);
                if (error)
                        return (error);
                if (*vpp == dvp) {
                        vref(dvp);
                        *vpp = dvp;
                        return (0);
                }
        }
        error = devfs_allocv(de, mp, cnp->cn_lkflags & LK_TYPE_MASK, vpp);
        *dm_unlock = 0;
        return (error);
}

static int
devfs_lookup(struct vop_lookup_args *ap)
{
        int j;
        struct devfs_mount *dmp;
        int dm_unlock;

        if (devfs_populate_vp(ap->a_dvp) != 0)
                return (ENOTDIR);

        dmp = VFSTODEVFS(ap->a_dvp->v_mount);
        dm_unlock = 1;
        j = devfs_lookupx(ap, &dm_unlock);
        if (dm_unlock == 1)
                sx_xunlock(&dmp->dm_lock);
        return (j);
}

static int
devfs_mknod(struct vop_mknod_args *ap)
{
        struct componentname *cnp;
        struct vnode *dvp, **vpp;
        struct devfs_dirent *dd, *de;
        struct devfs_mount *dmp;
        int error;

        /*
         * The only type of node we should be creating here is a
         * character device, for anything else return EOPNOTSUPP.
         */
        if (ap->a_vap->va_type != VCHR)
                return (EOPNOTSUPP);
        dvp = ap->a_dvp;
        dmp = VFSTODEVFS(dvp->v_mount);

        cnp = ap->a_cnp;
        vpp = ap->a_vpp;
        dd = dvp->v_data;

        error = ENOENT;
        sx_xlock(&dmp->dm_lock);
        TAILQ_FOREACH(de, &dd->de_dlist, de_list) {
                if (cnp->cn_namelen != de->de_dirent->d_namlen)
                        continue;
                if (de->de_dirent->d_type == DT_CHR &&
                    (de->de_cdp->cdp_flags & CDP_ACTIVE) == 0)
                        continue;
                if (bcmp(cnp->cn_nameptr, de->de_dirent->d_name,
                    de->de_dirent->d_namlen) != 0)
                        continue;
                if (de->de_flags & DE_WHITEOUT)
                        break;
                goto notfound;
        }
        if (de == NULL)
                goto notfound;
        de->de_flags &= ~DE_WHITEOUT;
        error = devfs_allocv(de, dvp->v_mount, LK_EXCLUSIVE, vpp);
        return (error);
notfound:
        sx_xunlock(&dmp->dm_lock);
        return (error);
}

/* ARGSUSED */
static int
devfs_open(struct vop_open_args *ap)
{
        struct thread *td = ap->a_td;
        struct vnode *vp = ap->a_vp;
        struct cdev *dev = vp->v_rdev;
        struct file *fp = ap->a_fp;
        int error, ref, vlocked;
        struct cdevsw *dsw;
        struct file *fpop;

        if (vp->v_type == VBLK)
                return (ENXIO);

        if (dev == NULL)
                return (ENXIO);

        /* Make this field valid before any I/O in d_open. */
        if (dev->si_iosize_max == 0)
                dev->si_iosize_max = DFLTPHYS;

        dsw = dev_refthread(dev, &ref);
        if (dsw == NULL)
                return (ENXIO);
        if (fp == NULL && dsw->d_fdopen != NULL) {
                dev_relthread(dev, ref);
                return (ENXIO);
        }

        if (vp->v_type == VCHR)
                devfs_usecount_add(vp);

        vlocked = VOP_ISLOCKED(vp);
        VOP_UNLOCK(vp);

        fpop = td->td_fpop;
        td->td_fpop = fp;
        if (fp != NULL) {
                fp->f_data = dev;
                fp->f_vnode = vp;
        }
        if (dsw->d_fdopen != NULL)
                error = dsw->d_fdopen(dev, ap->a_mode, td, fp);
        else
                error = dsw->d_open(dev, ap->a_mode, S_IFCHR, td);
        /* Clean up any cdevpriv upon error. */
        if (error != 0)
                devfs_clear_cdevpriv();
        td->td_fpop = fpop;

        vn_lock(vp, vlocked | LK_RETRY);
        if (error != 0 && vp->v_type == VCHR)
                devfs_usecount_sub(vp);

        dev_relthread(dev, ref);
        if (error != 0) {
                if (error == ERESTART)
                        error = EINTR;
                return (error);
        }

#if 0   /* /dev/console */
        KASSERT(fp != NULL, ("Could not vnode bypass device on NULL fp"));
#else
        if (fp == NULL)
                return (error);
#endif
        if (fp->f_ops == &badfileops)
                finit(fp, fp->f_flag, DTYPE_VNODE, dev, &devfs_ops_f);
        return (error);
}

static int
devfs_pathconf(struct vop_pathconf_args *ap)
{

        switch (ap->a_name) {
        case _PC_FILESIZEBITS:
                *ap->a_retval = 64;
                return (0);
        case _PC_NAME_MAX:
                *ap->a_retval = NAME_MAX;
                return (0);
        case _PC_LINK_MAX:
                *ap->a_retval = INT_MAX;
                return (0);
        case _PC_SYMLINK_MAX:
                *ap->a_retval = MAXPATHLEN;
                return (0);
        case _PC_MAX_CANON:
                if (ap->a_vp->v_vflag & VV_ISTTY) {
                        *ap->a_retval = MAX_CANON;
                        return (0);
                }
                return (EINVAL);
        case _PC_MAX_INPUT:
                if (ap->a_vp->v_vflag & VV_ISTTY) {
                        *ap->a_retval = MAX_INPUT;
                        return (0);
                }
                return (EINVAL);
        case _PC_VDISABLE:
                if (ap->a_vp->v_vflag & VV_ISTTY) {
                        *ap->a_retval = _POSIX_VDISABLE;
                        return (0);
                }
                return (EINVAL);
        case _PC_MAC_PRESENT:
#ifdef MAC
                /*
                 * If MAC is enabled, devfs automatically supports
                 * trivial non-persistent label storage.
                 */
                *ap->a_retval = 1;
#else
                *ap->a_retval = 0;
#endif
                return (0);
        case _PC_CHOWN_RESTRICTED:
                *ap->a_retval = 1;
                return (0);
        default:
                return (vop_stdpathconf(ap));
        }
        /* NOTREACHED */
}

/* ARGSUSED */
static int
devfs_poll_f(struct file *fp, int events, struct ucred *cred, struct thread *td)
{
        struct cdev *dev;
        struct cdevsw *dsw;
        int error, ref;
        struct file *fpop;

        fpop = td->td_fpop;
        error = devfs_fp_check(fp, &dev, &dsw, &ref);
        if (error != 0) {
                error = vnops.fo_poll(fp, events, cred, td);
                return (error);
        }
        error = dsw->d_poll(dev, events, td);
        td->td_fpop = fpop;
        dev_relthread(dev, ref);
        return(error);
}

/*
 * Print out the contents of a special device vnode.
 */
static int
devfs_print(struct vop_print_args *ap)
{

        printf("\tdev %s\n", devtoname(ap->a_vp->v_rdev));
        return (0);
}

static int
devfs_read_f(struct file *fp, struct uio *uio, struct ucred *cred,
    int flags, struct thread *td)
{
        struct cdev *dev;
        int ioflag, error, ref;
        ssize_t resid;
        struct cdevsw *dsw;
        struct file *fpop;

        if (uio->uio_resid > DEVFS_IOSIZE_MAX)
                return (EINVAL);
        fpop = td->td_fpop;
        error = devfs_fp_check(fp, &dev, &dsw, &ref);
        if (error != 0) {
                error = vnops.fo_read(fp, uio, cred, flags, td);
                return (error);
        }
        resid = uio->uio_resid;
        ioflag = fp->f_flag & (O_NONBLOCK | O_DIRECT);
        if (ioflag & O_DIRECT)
                ioflag |= IO_DIRECT;

        foffset_lock_uio(fp, uio, flags | FOF_NOLOCK);
        error = dsw->d_read(dev, uio, ioflag);
        if (uio->uio_resid != resid || (error == 0 && resid != 0))
                devfs_timestamp(&dev->si_atime);
        td->td_fpop = fpop;
        dev_relthread(dev, ref);

        foffset_unlock_uio(fp, uio, flags | FOF_NOLOCK | FOF_NEXTOFF_R);
        return (error);
}

static int
devfs_readdir(struct vop_readdir_args *ap)
{
        int error;
        struct uio *uio;
        struct dirent *dp;
        struct devfs_dirent *dd;
        struct devfs_dirent *de;
        struct devfs_mount *dmp;
        off_t off;
        int *tmp_ncookies = NULL;
        ssize_t startresid;

        if (ap->a_vp->v_type != VDIR)
                return (ENOTDIR);

        uio = ap->a_uio;
        if (uio->uio_offset < 0)
                return (EINVAL);

        /*
         * XXX: This is a temporary hack to get around this filesystem not
         * supporting cookies. We store the location of the ncookies pointer
         * in a temporary variable before calling vfs_subr.c:vfs_read_dirent()
         * and set the number of cookies to 0. We then set the pointer to
         * NULL so that vfs_read_dirent doesn't try to call realloc() on 
         * ap->a_cookies. Later in this function, we restore the ap->a_ncookies
         * pointer to its original location before returning to the caller.
         */
        if (ap->a_ncookies != NULL) {
                tmp_ncookies = ap->a_ncookies;
                *ap->a_ncookies = 0;
                ap->a_ncookies = NULL;
        }

        dmp = VFSTODEVFS(ap->a_vp->v_mount);
        if (devfs_populate_vp(ap->a_vp) != 0) {
                if (tmp_ncookies != NULL)
                        ap->a_ncookies = tmp_ncookies;
                return (EIO);
        }
        error = 0;
        de = ap->a_vp->v_data;
        off = 0;
        startresid = uio->uio_resid;
        TAILQ_FOREACH(dd, &de->de_dlist, de_list) {
                KASSERT(dd->de_cdp != (void *)0xdeadc0de, ("%s %d\n", __func__, __LINE__));
                if (dd->de_flags & (DE_COVERED | DE_WHITEOUT))
                        continue;
                if (devfs_prison_check(dd, uio->uio_td))
                        continue;
                if (dd->de_dirent->d_type == DT_DIR)
                        de = dd->de_dir;
                else
                        de = dd;
                dp = dd->de_dirent;
                MPASS(dp->d_reclen == GENERIC_DIRSIZ(dp));
                if (dp->d_reclen > uio->uio_resid) {
                        /* Nothing was copied out, return EINVAL. */
                        if (uio->uio_resid == startresid)
                                error = EINVAL;
                        /* Otherwise stop. */
                        break;
                }
                dp->d_fileno = de->de_inode;
                /* NOTE: d_off is the offset for the *next* entry. */
                dp->d_off = off + dp->d_reclen;
                if (off >= uio->uio_offset) {
                        error = vfs_read_dirent(ap, dp, off);
                        if (error)
                                break;
                }
                off += dp->d_reclen;
        }
        sx_xunlock(&dmp->dm_lock);
        uio->uio_offset = off;

        /*
         * Restore ap->a_ncookies if it wasn't originally NULL in the first
         * place.
         */
        if (tmp_ncookies != NULL)
                ap->a_ncookies = tmp_ncookies;
        if (dd == NULL && error == 0 && ap->a_eofflag != NULL)
                *ap->a_eofflag = 1;

        return (error);
}

static int
devfs_readlink(struct vop_readlink_args *ap)
{
        struct devfs_dirent *de;

        de = ap->a_vp->v_data;
        return (uiomove(de->de_symlink, strlen(de->de_symlink), ap->a_uio));
}

static void
devfs_reclaiml(struct vnode *vp)
{
        struct devfs_dirent *de;

        mtx_assert(&devfs_de_interlock, MA_OWNED);
        de = vp->v_data;
        if (de != NULL) {
                MPASS(de->de_usecount == 0);
                de->de_vnode = NULL;
                vp->v_data = NULL;
        }
}

static int
devfs_reclaim(struct vop_reclaim_args *ap)
{
        struct vnode *vp;

        vp = ap->a_vp;
        mtx_lock(&devfs_de_interlock);
        devfs_reclaiml(vp);
        mtx_unlock(&devfs_de_interlock);
        return (0);
}

static int
devfs_reclaim_vchr(struct vop_reclaim_args *ap)
{
        struct vnode *vp;
        struct cdev *dev;

        vp = ap->a_vp;
        MPASS(vp->v_type == VCHR);

        mtx_lock(&devfs_de_interlock);
        VI_LOCK(vp);
        devfs_usecount_subl(vp);
        devfs_reclaiml(vp);
        mtx_unlock(&devfs_de_interlock);
        dev_lock();
        dev = vp->v_rdev;
        vp->v_rdev = NULL;
        dev_unlock();
        VI_UNLOCK(vp);
        if (dev != NULL)
                dev_rel(dev);
        return (0);
}

static int
devfs_remove(struct vop_remove_args *ap)
{
        struct vnode *dvp = ap->a_dvp;
        struct vnode *vp = ap->a_vp;
        struct devfs_dirent *dd;
        struct devfs_dirent *de, *de_covered;
        struct devfs_mount *dmp = VFSTODEVFS(vp->v_mount);

        ASSERT_VOP_ELOCKED(dvp, "devfs_remove");
        ASSERT_VOP_ELOCKED(vp, "devfs_remove");

        sx_xlock(&dmp->dm_lock);
        dd = ap->a_dvp->v_data;
        de = vp->v_data;
        if (de->de_cdp == NULL) {
                TAILQ_REMOVE(&dd->de_dlist, de, de_list);
                if (de->de_dirent->d_type == DT_LNK) {
                        de_covered = devfs_find(dd, de->de_dirent->d_name,
                            de->de_dirent->d_namlen, 0);
                        if (de_covered != NULL)
                                de_covered->de_flags &= ~DE_COVERED;
                }
                /* We need to unlock dvp because devfs_delete() may lock it. */
                VOP_UNLOCK(vp);
                if (dvp != vp)
                        VOP_UNLOCK(dvp);
                devfs_delete(dmp, de, 0);
                sx_xunlock(&dmp->dm_lock);
                if (dvp != vp)
                        vn_lock(dvp, LK_EXCLUSIVE | LK_RETRY);
                vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
        } else {
                de->de_flags |= DE_WHITEOUT;
                sx_xunlock(&dmp->dm_lock);
        }
        return (0);
}

/*
 * Revoke is called on a tty when a terminal session ends.  The vnode
 * is orphaned by setting v_op to deadfs so we need to let go of it
 * as well so that we create a new one next time around.
 *
 */
static int
devfs_revoke(struct vop_revoke_args *ap)
{
        struct vnode *vp = ap->a_vp, *vp2;
        struct cdev *dev;
        struct cdev_priv *cdp;
        struct devfs_dirent *de;
        enum vgetstate vs;
        u_int i;

        KASSERT((ap->a_flags & REVOKEALL) != 0, ("devfs_revoke !REVOKEALL"));

        dev = vp->v_rdev;
        cdp = cdev2priv(dev);

        dev_lock();
        cdp->cdp_inuse++;
        dev_unlock();

        vhold(vp);
        vgone(vp);
        vdrop(vp);

        VOP_UNLOCK(vp);
 loop:
        for (;;) {
                mtx_lock(&devfs_de_interlock);
                dev_lock();
                vp2 = NULL;
                for (i = 0; i <= cdp->cdp_maxdirent; i++) {
                        de = cdp->cdp_dirents[i];
                        if (de == NULL)
                                continue;

                        vp2 = de->de_vnode;
                        if (vp2 != NULL) {
                                dev_unlock();
                                vs = vget_prep(vp2);
                                mtx_unlock(&devfs_de_interlock);
                                if (vget_finish(vp2, LK_EXCLUSIVE, vs) != 0)
                                        goto loop;
                                vhold(vp2);
                                vgone(vp2);
                                vdrop(vp2);
                                vput(vp2);
                                break;
                        }
                }
                if (vp2 != NULL) {
                        continue;
                }
                dev_unlock();
                mtx_unlock(&devfs_de_interlock);
                break;
        }
        dev_lock();
        cdp->cdp_inuse--;
        if (!(cdp->cdp_flags & CDP_ACTIVE) && cdp->cdp_inuse == 0) {
                KASSERT((cdp->cdp_flags & CDP_ON_ACTIVE_LIST) != 0,
                    ("%s: cdp %p (%s) not on active list",
                    __func__, cdp, dev->si_name));
                cdp->cdp_flags &= ~CDP_ON_ACTIVE_LIST;
                TAILQ_REMOVE(&cdevp_list, cdp, cdp_list);
                dev_unlock();
                dev_rel(&cdp->cdp_c);
        } else
                dev_unlock();

        vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
        return (0);
}

static int
devfs_rioctl(struct vop_ioctl_args *ap)
{
        struct vnode *vp;
        struct devfs_mount *dmp;
        int error;

        vp = ap->a_vp;
        vn_lock(vp, LK_SHARED | LK_RETRY);
        if (VN_IS_DOOMED(vp)) {
                VOP_UNLOCK(vp);
                return (EBADF);
        }
        dmp = VFSTODEVFS(vp->v_mount);
        sx_xlock(&dmp->dm_lock);
        VOP_UNLOCK(vp);
        DEVFS_DMP_HOLD(dmp);
        devfs_populate(dmp);
        if (DEVFS_DMP_DROP(dmp)) {
                sx_xunlock(&dmp->dm_lock);
                devfs_unmount_final(dmp);
                return (ENOENT);
        }
        error = devfs_rules_ioctl(dmp, ap->a_command, ap->a_data, ap->a_td);
        sx_xunlock(&dmp->dm_lock);
        return (error);
}

static int
devfs_rread(struct vop_read_args *ap)
{

        if (ap->a_vp->v_type != VDIR)
                return (EINVAL);
        return (VOP_READDIR(ap->a_vp, ap->a_uio, ap->a_cred, NULL, NULL, NULL));
}

static int
devfs_setattr(struct vop_setattr_args *ap)
{
        struct devfs_dirent *de;
        struct vattr *vap;
        struct vnode *vp;
        struct thread *td;
        int c, error;
        uid_t uid;
        gid_t gid;

        vap = ap->a_vap;
        vp = ap->a_vp;
        td = curthread;
        if ((vap->va_type != VNON) ||
            (vap->va_nlink != VNOVAL) ||
            (vap->va_fsid != VNOVAL) ||
            (vap->va_fileid != VNOVAL) ||
            (vap->va_blocksize != VNOVAL) ||
            (vap->va_flags != VNOVAL && vap->va_flags != 0) ||
            (vap->va_rdev != VNOVAL) ||
            ((int)vap->va_bytes != VNOVAL) ||
            (vap->va_gen != VNOVAL)) {
                return (EINVAL);
        }

        error = devfs_populate_vp(vp);
        if (error != 0)
                return (error);

        de = vp->v_data;
        if (vp->v_type == VDIR)
                de = de->de_dir;

        c = 0;
        if (vap->va_uid == (uid_t)VNOVAL)
                uid = de->de_uid;
        else
                uid = vap->va_uid;
        if (vap->va_gid == (gid_t)VNOVAL)
                gid = de->de_gid;
        else
                gid = vap->va_gid;
        if (uid != de->de_uid || gid != de->de_gid) {
                if ((ap->a_cred->cr_uid != de->de_uid) || uid != de->de_uid ||
                    (gid != de->de_gid && !groupmember(gid, ap->a_cred))) {
                        error = priv_check(td, PRIV_VFS_CHOWN);
                        if (error != 0)
                                goto ret;
                }
                de->de_uid = uid;
                de->de_gid = gid;
                c = 1;
        }

        if (vap->va_mode != (mode_t)VNOVAL) {
                if (ap->a_cred->cr_uid != de->de_uid) {
                        error = priv_check(td, PRIV_VFS_ADMIN);
                        if (error != 0)
                                goto ret;
                }
                de->de_mode = vap->va_mode;
                c = 1;
        }

        if (vap->va_atime.tv_sec != VNOVAL || vap->va_mtime.tv_sec != VNOVAL) {
                error = vn_utimes_perm(vp, vap, ap->a_cred, td);
                if (error != 0)
                        goto ret;
                if (vap->va_atime.tv_sec != VNOVAL) {
                        if (vp->v_type == VCHR)
                                vp->v_rdev->si_atime = vap->va_atime;
                        else
                                de->de_atime = vap->va_atime;
                }
                if (vap->va_mtime.tv_sec != VNOVAL) {
                        if (vp->v_type == VCHR)
                                vp->v_rdev->si_mtime = vap->va_mtime;
                        else
                                de->de_mtime = vap->va_mtime;
                }
                c = 1;
        }

        if (c) {
                if (vp->v_type == VCHR)
                        vfs_timestamp(&vp->v_rdev->si_ctime);
                else
                        vfs_timestamp(&de->de_mtime);
        }

ret:
        sx_xunlock(&VFSTODEVFS(vp->v_mount)->dm_lock);
        return (error);
}

#ifdef MAC
static int
devfs_setlabel(struct vop_setlabel_args *ap)
{
        struct vnode *vp;
        struct devfs_dirent *de;

        vp = ap->a_vp;
        de = vp->v_data;

        mac_vnode_relabel(ap->a_cred, vp, ap->a_label);
        mac_devfs_update(vp->v_mount, de, vp);

        return (0);
}
#endif

static int
devfs_stat_f(struct file *fp, struct stat *sb, struct ucred *cred)
{

        return (vnops.fo_stat(fp, sb, cred));
}

static int
devfs_symlink(struct vop_symlink_args *ap)
{
        int i, error;
        struct devfs_dirent *dd;
        struct devfs_dirent *de, *de_covered, *de_dotdot;
        struct devfs_mount *dmp;

        error = priv_check(curthread, PRIV_DEVFS_SYMLINK);
        if (error)
                return(error);
        dmp = VFSTODEVFS(ap->a_dvp->v_mount);
        if (devfs_populate_vp(ap->a_dvp) != 0)
                return (ENOENT);

        dd = ap->a_dvp->v_data;
        de = devfs_newdirent(ap->a_cnp->cn_nameptr, ap->a_cnp->cn_namelen);
        de->de_flags = DE_USER;
        de->de_uid = 0;
        de->de_gid = 0;
        de->de_mode = 0755;
        de->de_inode = alloc_unr(devfs_inos);
        de->de_dir = dd;
        de->de_dirent->d_type = DT_LNK;
        i = strlen(ap->a_target) + 1;
        de->de_symlink = malloc(i, M_DEVFS, M_WAITOK);
        bcopy(ap->a_target, de->de_symlink, i);
#ifdef MAC
        mac_devfs_create_symlink(ap->a_cnp->cn_cred, dmp->dm_mount, dd, de);
#endif
        de_covered = devfs_find(dd, de->de_dirent->d_name,
            de->de_dirent->d_namlen, 0);
        if (de_covered != NULL) {
                if ((de_covered->de_flags & DE_USER) != 0) {
                        devfs_delete(dmp, de, DEVFS_DEL_NORECURSE);
                        sx_xunlock(&dmp->dm_lock);
                        return (EEXIST);
                }
                KASSERT((de_covered->de_flags & DE_COVERED) == 0,
                    ("devfs_symlink: entry %p already covered", de_covered));
                de_covered->de_flags |= DE_COVERED;
        }

        de_dotdot = TAILQ_FIRST(&dd->de_dlist);         /* "." */
        de_dotdot = TAILQ_NEXT(de_dotdot, de_list);     /* ".." */
        TAILQ_INSERT_AFTER(&dd->de_dlist, de_dotdot, de, de_list);
        devfs_dir_ref_de(dmp, dd);
        devfs_rules_apply(dmp, de);

        return (devfs_allocv(de, ap->a_dvp->v_mount, LK_EXCLUSIVE, ap->a_vpp));
}

static int
devfs_truncate_f(struct file *fp, off_t length, struct ucred *cred, struct thread *td)
{

        return (vnops.fo_truncate(fp, length, cred, td));
}

static int
devfs_write_f(struct file *fp, struct uio *uio, struct ucred *cred,
    int flags, struct thread *td)
{
        struct cdev *dev;
        int error, ioflag, ref;
        ssize_t resid;
        struct cdevsw *dsw;
        struct file *fpop;

        if (uio->uio_resid > DEVFS_IOSIZE_MAX)
                return (EINVAL);
        fpop = td->td_fpop;
        error = devfs_fp_check(fp, &dev, &dsw, &ref);
        if (error != 0) {
                error = vnops.fo_write(fp, uio, cred, flags, td);
                return (error);
        }
        KASSERT(uio->uio_td == td, ("uio_td %p is not td %p", uio->uio_td, td));
        ioflag = fp->f_flag & (O_NONBLOCK | O_DIRECT | O_FSYNC);
        if (ioflag & O_DIRECT)
                ioflag |= IO_DIRECT;
        foffset_lock_uio(fp, uio, flags | FOF_NOLOCK);

        resid = uio->uio_resid;

        error = dsw->d_write(dev, uio, ioflag);
        if (uio->uio_resid != resid || (error == 0 && resid != 0)) {
                devfs_timestamp(&dev->si_ctime);
                dev->si_mtime = dev->si_ctime;
        }
        td->td_fpop = fpop;
        dev_relthread(dev, ref);

        foffset_unlock_uio(fp, uio, flags | FOF_NOLOCK | FOF_NEXTOFF_W);
        return (error);
}

static int
devfs_mmap_f(struct file *fp, vm_map_t map, vm_offset_t *addr, vm_size_t size,
    vm_prot_t prot, vm_prot_t cap_maxprot, int flags, vm_ooffset_t foff,
    struct thread *td)
{
        struct cdev *dev;
        struct cdevsw *dsw;
        struct mount *mp;
        struct vnode *vp;
        struct file *fpop;
        vm_object_t object;
        vm_prot_t maxprot;
        int error, ref;

        vp = fp->f_vnode;

        /*
         * Ensure that file and memory protections are
         * compatible.
         */
        mp = vp->v_mount;
        if (mp != NULL && (mp->mnt_flag & MNT_NOEXEC) != 0) {
                maxprot = VM_PROT_NONE;
                if ((prot & VM_PROT_EXECUTE) != 0)
                        return (EACCES);
        } else
                maxprot = VM_PROT_EXECUTE;
        if ((fp->f_flag & FREAD) != 0)
                maxprot |= VM_PROT_READ;
        else if ((prot & VM_PROT_READ) != 0)
                return (EACCES);

        /*
         * If we are sharing potential changes via MAP_SHARED and we
         * are trying to get write permission although we opened it
         * without asking for it, bail out.
         *
         * Note that most character devices always share mappings.
         * The one exception is that D_MMAP_ANON devices
         * (i.e. /dev/zero) permit private writable mappings.
         *
         * Rely on vm_mmap_cdev() to fail invalid MAP_PRIVATE requests
         * as well as updating maxprot to permit writing for
         * D_MMAP_ANON devices rather than doing that here.
         */
        if ((flags & MAP_SHARED) != 0) {
                if ((fp->f_flag & FWRITE) != 0)
                        maxprot |= VM_PROT_WRITE;
                else if ((prot & VM_PROT_WRITE) != 0)
                        return (EACCES);
        }
        maxprot &= cap_maxprot;

        fpop = td->td_fpop;
        error = devfs_fp_check(fp, &dev, &dsw, &ref);
        if (error != 0)
                return (error);

        error = vm_mmap_cdev(td, size, prot, &maxprot, &flags, dev, dsw, &foff,
            &object);
        td->td_fpop = fpop;
        dev_relthread(dev, ref);
        if (error != 0)
                return (error);

        error = vm_mmap_object(map, addr, size, prot, maxprot, flags, object,
            foff, FALSE, td);
        if (error != 0)
                vm_object_deallocate(object);
        return (error);
}

dev_t
dev2udev(struct cdev *x)
{
        if (x == NULL)
                return (NODEV);
        return (cdev2priv(x)->cdp_inode);
}

static int
devfs_cmp_f(struct file *fp1, struct file *fp2, struct thread *td)
{
        if (fp2->f_type != DTYPE_VNODE || fp2->f_ops != &devfs_ops_f)
                return (3);
        return (kcmp_cmp((uintptr_t)fp1->f_data, (uintptr_t)fp2->f_data));
}

static const struct fileops devfs_ops_f = {
        .fo_read =      devfs_read_f,
        .fo_write =     devfs_write_f,
        .fo_truncate =  devfs_truncate_f,
        .fo_ioctl =     devfs_ioctl_f,
        .fo_poll =      devfs_poll_f,
        .fo_kqfilter =  devfs_kqfilter_f,
        .fo_stat =      devfs_stat_f,
        .fo_close =     devfs_close_f,
        .fo_chmod =     vn_chmod,
        .fo_chown =     vn_chown,
        .fo_sendfile =  vn_sendfile,
        .fo_seek =      vn_seek,
        .fo_fill_kinfo = vn_fill_kinfo,
        .fo_mmap =      devfs_mmap_f,
        .fo_cmp =       devfs_cmp_f,
        .fo_flags =     DFLAG_PASSABLE | DFLAG_SEEKABLE
};

/* Vops for non-CHR vnodes in /dev. */
static struct vop_vector devfs_vnodeops = {
        .vop_default =          &default_vnodeops,

        .vop_access =           devfs_access,
        .vop_getattr =          devfs_getattr,
        .vop_ioctl =            devfs_rioctl,
        .vop_lookup =           devfs_lookup,
        .vop_mknod =            devfs_mknod,
        .vop_pathconf =         devfs_pathconf,
        .vop_read =             devfs_rread,
        .vop_readdir =          devfs_readdir,
        .vop_readlink =         devfs_readlink,
        .vop_reclaim =          devfs_reclaim,
        .vop_remove =           devfs_remove,
        .vop_revoke =           devfs_revoke,
        .vop_setattr =          devfs_setattr,
#ifdef MAC
        .vop_setlabel =         devfs_setlabel,
#endif
        .vop_symlink =          devfs_symlink,
        .vop_vptocnp =          devfs_vptocnp,
        .vop_lock1 =            vop_lock,
        .vop_unlock =           vop_unlock,
        .vop_islocked =         vop_islocked,
        .vop_add_writecount =   vop_stdadd_writecount_nomsync,
};
VFS_VOP_VECTOR_REGISTER(devfs_vnodeops);

/* Vops for VCHR vnodes in /dev. */
static struct vop_vector devfs_specops = {
        .vop_default =          &default_vnodeops,

        .vop_access =           devfs_access,
        .vop_bmap =             VOP_PANIC,
        .vop_close =            devfs_close,
        .vop_create =           VOP_PANIC,
        .vop_fsync =            vop_stdfsync,
        .vop_getattr =          devfs_getattr,
        .vop_ioctl =            devfs_ioctl,
        .vop_link =             VOP_PANIC,
        .vop_mkdir =            VOP_PANIC,
        .vop_mknod =            VOP_PANIC,
        .vop_open =             devfs_open,
        .vop_pathconf =         devfs_pathconf,
        .vop_poll =             dead_poll,
        .vop_print =            devfs_print,
        .vop_read =             dead_read,
        .vop_readdir =          VOP_PANIC,
        .vop_readlink =         VOP_PANIC,
        .vop_reallocblks =      VOP_PANIC,
        .vop_reclaim =          devfs_reclaim_vchr,
        .vop_remove =           devfs_remove,
        .vop_rename =           VOP_PANIC,
        .vop_revoke =           devfs_revoke,
        .vop_rmdir =            VOP_PANIC,
        .vop_setattr =          devfs_setattr,
#ifdef MAC
        .vop_setlabel =         devfs_setlabel,
#endif
        .vop_strategy =         VOP_PANIC,
        .vop_symlink =          VOP_PANIC,
        .vop_vptocnp =          devfs_vptocnp,
        .vop_write =            dead_write,
        .vop_lock1 =            vop_lock,
        .vop_unlock =           vop_unlock,
        .vop_islocked =         vop_islocked,
        .vop_add_writecount =   vop_stdadd_writecount_nomsync,
};
VFS_VOP_VECTOR_REGISTER(devfs_specops);

/*
 * Our calling convention to the device drivers used to be that we passed
 * vnode.h IO_* flags to read()/write(), but we're moving to fcntl.h O_ 
 * flags instead since that's what open(), close() and ioctl() takes and
 * we don't really want vnode.h in device drivers.
 * We solved the source compatibility by redefining some vnode flags to
 * be the same as the fcntl ones and by sending down the bitwise OR of
 * the respective fcntl/vnode flags.  These CTASSERTS make sure nobody
 * pulls the rug out under this.
 */
CTASSERT(O_NONBLOCK == IO_NDELAY);
CTASSERT(O_FSYNC == IO_SYNC);