We have to use pmap_extract() here. If we lose a race against page

[dragonfly.git] / sys / kern / vfs_syscalls.c

/*
 * Copyright (c) 1989, 1993
 *      The Regents of the University of California.  All rights reserved.
 * (c) UNIX System Laboratories, Inc.
 * All or some portions of this file are derived from material licensed
 * to the University of California by American Telephone and Telegraph
 * Co. or Unix System Laboratories, Inc. and are reproduced herein with
 * the permission of UNIX System Laboratories, Inc.
 *
 * 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.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by the University of
 *      California, Berkeley and its contributors.
 * 4. 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.
 *
 *      @(#)vfs_syscalls.c      8.13 (Berkeley) 4/15/94
 * $FreeBSD: src/sys/kern/vfs_syscalls.c,v 1.151.2.18 2003/04/04 20:35:58 tegge Exp $
 * $DragonFly: src/sys/kern/vfs_syscalls.c,v 1.88 2006/05/06 18:48:52 dillon Exp $
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/buf.h>
#include <sys/conf.h>
#include <sys/sysent.h>
#include <sys/malloc.h>
#include <sys/mount.h>
#include <sys/mountctl.h>
#include <sys/sysproto.h>
#include <sys/filedesc.h>
#include <sys/kernel.h>
#include <sys/fcntl.h>
#include <sys/file.h>
#include <sys/linker.h>
#include <sys/stat.h>
#include <sys/unistd.h>
#include <sys/vnode.h>
#include <sys/proc.h>
#include <sys/namei.h>
#include <sys/nlookup.h>
#include <sys/dirent.h>
#include <sys/extattr.h>
#include <sys/kern_syscall.h>

#include <machine/limits.h>
#include <vfs/union/union.h>
#include <sys/sysctl.h>
#include <vm/vm.h>
#include <vm/vm_object.h>
#include <vm/vm_zone.h>
#include <vm/vm_page.h>

#include <sys/file2.h>

static int checkvp_chdir (struct vnode *vn, struct thread *td);
static void checkdirs (struct vnode *olddp, struct namecache *ncp);
static int chroot_refuse_vdir_fds (struct filedesc *fdp);
static int chroot_visible_mnt(struct mount *mp, struct proc *p);
static int getutimes (const struct timeval *, struct timespec *);
static int setfown (struct vnode *, uid_t, gid_t);
static int setfmode (struct vnode *, int);
static int setfflags (struct vnode *, int);
static int setutimes (struct vnode *, const struct timespec *, int);
static int      usermount = 0;  /* if 1, non-root can mount fs. */

int (*union_dircheckp) (struct thread *, struct vnode **, struct file *);

SYSCTL_INT(_vfs, OID_AUTO, usermount, CTLFLAG_RW, &usermount, 0, "");

/*
 * Virtual File System System Calls
 */

/*
 * Mount a file system.
 */
/*
 * mount_args(char *type, char *path, int flags, caddr_t data)
 */
/* ARGSUSED */
int
mount(struct mount_args *uap)
{
        struct thread *td = curthread;
        struct proc *p = td->td_proc;
        struct vnode *vp;
        struct namecache *ncp;
        struct mount *mp;
        struct vfsconf *vfsp;
        int error, flag = 0, flag2 = 0;
        struct vattr va;
        struct nlookupdata nd;
        char fstypename[MFSNAMELEN];
        struct nlcomponent nlc;
        struct ucred *cred = p->p_ucred;

        KKASSERT(p);
        if (cred->cr_prison != NULL)
                return (EPERM);
        if (usermount == 0 && (error = suser(td)))
                return (error);
        /*
         * Do not allow NFS export by non-root users.
         */
        if (uap->flags & MNT_EXPORTED) {
                error = suser(td);
                if (error)
                        return (error);
        }
        /*
         * Silently enforce MNT_NOSUID and MNT_NODEV for non-root users
         */
        if (suser(td)) 
                uap->flags |= MNT_NOSUID | MNT_NODEV;

        /*
         * Lookup the requested path and extract the ncp and vnode.
         */
        error = nlookup_init(&nd, uap->path, UIO_USERSPACE, NLC_FOLLOW);
        if (error == 0) {
                if ((error = nlookup(&nd)) == 0) {
                        if (nd.nl_ncp->nc_vp == NULL)
                                error = ENOENT;
                }
        }
        if (error) {
                nlookup_done(&nd);
                return (error);
        }

        /*
         * Extract the locked+refd ncp and cleanup the nd structure
         */
        ncp = nd.nl_ncp;
        nd.nl_ncp = NULL;
        nlookup_done(&nd);

        /*
         * now we have the locked ref'd ncp and unreferenced vnode.
         */
        vp = ncp->nc_vp;
        if ((error = vget(vp, LK_EXCLUSIVE)) != 0) {
                cache_put(ncp);
                return (error);
        }
        cache_unlock(ncp);

        /*
         * Now we have an unlocked ref'd ncp and a locked ref'd vp
         */
        if (uap->flags & MNT_UPDATE) {
                if ((vp->v_flag & VROOT) == 0) {
                        cache_drop(ncp);
                        vput(vp);
                        return (EINVAL);
                }
                mp = vp->v_mount;
                flag = mp->mnt_flag;
                flag2 = mp->mnt_kern_flag;
                /*
                 * We only allow the filesystem to be reloaded if it
                 * is currently mounted read-only.
                 */
                if ((uap->flags & MNT_RELOAD) &&
                    ((mp->mnt_flag & MNT_RDONLY) == 0)) {
                        cache_drop(ncp);
                        vput(vp);
                        return (EOPNOTSUPP);    /* Needs translation */
                }
                /*
                 * Only root, or the user that did the original mount is
                 * permitted to update it.
                 */
                if (mp->mnt_stat.f_owner != cred->cr_uid &&
                    (error = suser(td))) {
                        cache_drop(ncp);
                        vput(vp);
                        return (error);
                }
                if (vfs_busy(mp, LK_NOWAIT)) {
                        cache_drop(ncp);
                        vput(vp);
                        return (EBUSY);
                }
                if ((vp->v_flag & VMOUNT) != 0 ||
                    vp->v_mountedhere != NULL) {
                        cache_drop(ncp);
                        vfs_unbusy(mp);
                        vput(vp);
                        return (EBUSY);
                }
                vp->v_flag |= VMOUNT;
                mp->mnt_flag |=
                    uap->flags & (MNT_RELOAD | MNT_FORCE | MNT_UPDATE);
                VOP_UNLOCK(vp, 0);
                goto update;
        }
        /*
         * If the user is not root, ensure that they own the directory
         * onto which we are attempting to mount.
         */
        if ((error = VOP_GETATTR(vp, &va)) ||
            (va.va_uid != cred->cr_uid && (error = suser(td)))) {
                cache_drop(ncp);
                vput(vp);
                return (error);
        }
        if ((error = vinvalbuf(vp, V_SAVE, 0, 0)) != 0) {
                cache_drop(ncp);
                vput(vp);
                return (error);
        }
        if (vp->v_type != VDIR) {
                cache_drop(ncp);
                vput(vp);
                return (ENOTDIR);
        }
        if ((error = copyinstr(uap->type, fstypename, MFSNAMELEN, NULL)) != 0) {
                cache_drop(ncp);
                vput(vp);
                return (error);
        }
        for (vfsp = vfsconf; vfsp; vfsp = vfsp->vfc_next) {
                if (!strcmp(vfsp->vfc_name, fstypename))
                        break;
        }
        if (vfsp == NULL) {
                linker_file_t lf;

                /* Only load modules for root (very important!) */
                if ((error = suser(td)) != 0) {
                        cache_drop(ncp);
                        vput(vp);
                        return error;
                }
                error = linker_load_file(fstypename, &lf);
                if (error || lf == NULL) {
                        cache_drop(ncp);
                        vput(vp);
                        if (lf == NULL)
                                error = ENODEV;
                        return error;
                }
                lf->userrefs++;
                /* lookup again, see if the VFS was loaded */
                for (vfsp = vfsconf; vfsp; vfsp = vfsp->vfc_next) {
                        if (!strcmp(vfsp->vfc_name, fstypename))
                                break;
                }
                if (vfsp == NULL) {
                        lf->userrefs--;
                        linker_file_unload(lf);
                        cache_drop(ncp);
                        vput(vp);
                        return (ENODEV);
                }
        }
        if ((vp->v_flag & VMOUNT) != 0 ||
            vp->v_mountedhere != NULL) {
                cache_drop(ncp);
                vput(vp);
                return (EBUSY);
        }
        vp->v_flag |= VMOUNT;

        /*
         * Allocate and initialize the filesystem.
         */
        mp = malloc(sizeof(struct mount), M_MOUNT, M_ZERO|M_WAITOK);
        TAILQ_INIT(&mp->mnt_nvnodelist);
        TAILQ_INIT(&mp->mnt_reservedvnlist);
        TAILQ_INIT(&mp->mnt_jlist);
        mp->mnt_nvnodelistsize = 0;
        lockinit(&mp->mnt_lock, "vfslock", 0, LK_NOPAUSE);
        vfs_busy(mp, LK_NOWAIT);
        mp->mnt_op = vfsp->vfc_vfsops;
        mp->mnt_vfc = vfsp;
        vfsp->vfc_refcount++;
        mp->mnt_stat.f_type = vfsp->vfc_typenum;
        mp->mnt_flag |= vfsp->vfc_flags & MNT_VISFLAGMASK;
        strncpy(mp->mnt_stat.f_fstypename, vfsp->vfc_name, MFSNAMELEN);
        mp->mnt_vnodecovered = vp;
        mp->mnt_stat.f_owner = cred->cr_uid;
        mp->mnt_iosize_max = DFLTPHYS;
        VOP_UNLOCK(vp, 0);
update:
        /*
         * Set the mount level flags.
         */
        if (uap->flags & MNT_RDONLY)
                mp->mnt_flag |= MNT_RDONLY;
        else if (mp->mnt_flag & MNT_RDONLY)
                mp->mnt_kern_flag |= MNTK_WANTRDWR;
        mp->mnt_flag &=~ (MNT_NOSUID | MNT_NOEXEC | MNT_NODEV |
            MNT_SYNCHRONOUS | MNT_UNION | MNT_ASYNC | MNT_NOATIME |
            MNT_NOSYMFOLLOW | MNT_IGNORE |
            MNT_NOCLUSTERR | MNT_NOCLUSTERW | MNT_SUIDDIR);
        mp->mnt_flag |= uap->flags & (MNT_NOSUID | MNT_NOEXEC |
            MNT_NODEV | MNT_SYNCHRONOUS | MNT_UNION | MNT_ASYNC | MNT_FORCE |
            MNT_NOSYMFOLLOW | MNT_IGNORE |
            MNT_NOATIME | MNT_NOCLUSTERR | MNT_NOCLUSTERW | MNT_SUIDDIR);
        /*
         * Mount the filesystem.
         * XXX The final recipients of VFS_MOUNT just overwrite the ndp they
         * get. 
         */
        error = VFS_MOUNT(mp, uap->path, uap->data, cred);
        if (mp->mnt_flag & MNT_UPDATE) {
                if (mp->mnt_kern_flag & MNTK_WANTRDWR)
                        mp->mnt_flag &= ~MNT_RDONLY;
                mp->mnt_flag &=~ (MNT_UPDATE | MNT_RELOAD | MNT_FORCE);
                mp->mnt_kern_flag &=~ MNTK_WANTRDWR;
                if (error) {
                        mp->mnt_flag = flag;
                        mp->mnt_kern_flag = flag2;
                }
                vfs_unbusy(mp);
                vp->v_flag &= ~VMOUNT;
                vrele(vp);
                cache_drop(ncp);
                return (error);
        }
        vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
        /*
         * Put the new filesystem on the mount list after root.  The mount
         * point gets its own mnt_ncp which is a special ncp linking the
         * vnode-under to the root of the new mount.  The lookup code
         * detects the mount point going forward and detects the special
         * mnt_ncp via NCP_MOUNTPT going backwards.
         *
         * It is not necessary to invalidate or purge the vnode underneath
         * because elements under the mount will be given their own glue
         * namecache record.
         */
        if (!error) {
                nlc.nlc_nameptr = "";
                nlc.nlc_namelen = 0;
                mp->mnt_ncp = cache_nlookup(ncp, &nlc);
                cache_setunresolved(mp->mnt_ncp);
                mp->mnt_ncp->nc_flag |= NCF_MOUNTPT;
                mp->mnt_ncp->nc_mount = mp;
                cache_drop(ncp);
                /* XXX get the root of the fs and cache_setvp(mnt_ncp...) */
                vp->v_flag &= ~VMOUNT;
                vp->v_mountedhere = mp;
                mountlist_insert(mp, MNTINS_LAST);
                checkdirs(vp, mp->mnt_ncp);
                cache_unlock(mp->mnt_ncp);      /* leave ref intact */
                VOP_UNLOCK(vp, 0);
                error = vfs_allocate_syncvnode(mp);
                vfs_unbusy(mp);
                if ((error = VFS_START(mp, 0)) != 0)
                        vrele(vp);
        } else {
                vfs_rm_vnodeops(&mp->mnt_vn_coherency_ops);
                vfs_rm_vnodeops(&mp->mnt_vn_journal_ops);
                vfs_rm_vnodeops(&mp->mnt_vn_norm_ops);
                vfs_rm_vnodeops(&mp->mnt_vn_spec_ops);
                vfs_rm_vnodeops(&mp->mnt_vn_fifo_ops);
                vp->v_flag &= ~VMOUNT;
                mp->mnt_vfc->vfc_refcount--;
                vfs_unbusy(mp);
                free(mp, M_MOUNT);
                cache_drop(ncp);
                vput(vp);
        }
        return (error);
}

/*
 * Scan all active processes to see if any of them have a current
 * or root directory onto which the new filesystem has just been
 * mounted. If so, replace them with the new mount point.
 *
 * The passed ncp is ref'd and locked (from the mount code) and
 * must be associated with the vnode representing the root of the
 * mount point.
 */
static void
checkdirs(struct vnode *olddp, struct namecache *ncp)
{
        struct filedesc *fdp;
        struct vnode *newdp;
        struct mount *mp;
        struct proc *p;

        if (olddp->v_usecount == 1)
                return;
        mp = olddp->v_mountedhere;
        if (VFS_ROOT(mp, &newdp))
                panic("mount: lost mount");
        cache_setvp(ncp, newdp);

        if (rootvnode == olddp) {
                vref(newdp);
                vfs_cache_setroot(newdp, cache_hold(ncp));
        }

        FOREACH_PROC_IN_SYSTEM(p) {
                fdp = p->p_fd;
                if (fdp->fd_cdir == olddp) {
                        vrele(fdp->fd_cdir);
                        vref(newdp);
                        fdp->fd_cdir = newdp;
                        cache_drop(fdp->fd_ncdir);
                        fdp->fd_ncdir = cache_hold(ncp);
                }
                if (fdp->fd_rdir == olddp) {
                        vrele(fdp->fd_rdir);
                        vref(newdp);
                        fdp->fd_rdir = newdp;
                        cache_drop(fdp->fd_nrdir);
                        fdp->fd_nrdir = cache_hold(ncp);
                }
        }
        vput(newdp);
}

/*
 * Unmount a file system.
 *
 * Note: unmount takes a path to the vnode mounted on as argument,
 * not special file (as before).
 */
/*
 * umount_args(char *path, int flags)
 */
/* ARGSUSED */
int
unmount(struct unmount_args *uap)
{
        struct thread *td = curthread;
        struct proc *p = td->td_proc;
        struct mount *mp = NULL;
        int error;
        struct nlookupdata nd;

        KKASSERT(p);
        if (p->p_ucred->cr_prison != NULL)
                return (EPERM);
        if (usermount == 0 && (error = suser(td)))
                return (error);

        error = nlookup_init(&nd, uap->path, UIO_USERSPACE, NLC_FOLLOW);
        if (error == 0)
                error = nlookup(&nd);
        if (error)
                goto out;

        mp = nd.nl_ncp->nc_mount;

        /*
         * Only root, or the user that did the original mount is
         * permitted to unmount this filesystem.
         */
        if ((mp->mnt_stat.f_owner != p->p_ucred->cr_uid) &&
            (error = suser(td)))
                goto out;

        /*
         * Don't allow unmounting the root file system.
         */
        if (mp->mnt_flag & MNT_ROOTFS) {
                error = EINVAL;
                goto out;
        }

        /*
         * Must be the root of the filesystem
         */
        if (! (nd.nl_ncp->nc_flag & NCF_MOUNTPT)) {
                error = EINVAL;
                goto out;
        }

out:
        nlookup_done(&nd);
        if (error)
                return (error);
        return (dounmount(mp, uap->flags));
}

/*
 * Do the actual file system unmount.
 */
static int
dounmount_interlock(struct mount *mp)
{
        if (mp->mnt_kern_flag & MNTK_UNMOUNT)
                return (EBUSY);
        mp->mnt_kern_flag |= MNTK_UNMOUNT;
        return(0);
}

int
dounmount(struct mount *mp, int flags)
{
        struct vnode *coveredvp;
        int error;
        int async_flag;
        int lflags;

        /*
         * Exclusive access for unmounting purposes
         */
        if ((error = mountlist_interlock(dounmount_interlock, mp)) != 0)
                return (error);

        /*
         * Allow filesystems to detect that a forced unmount is in progress.
         */
        if (flags & MNT_FORCE)
                mp->mnt_kern_flag |= MNTK_UNMOUNTF;
        lflags = LK_EXCLUSIVE | ((flags & MNT_FORCE) ? 0 : LK_NOWAIT);
        error = lockmgr(&mp->mnt_lock, lflags);
        if (error) {
                mp->mnt_kern_flag &= ~(MNTK_UNMOUNT | MNTK_UNMOUNTF);
                if (mp->mnt_kern_flag & MNTK_MWAIT)
                        wakeup(mp);
                return (error);
        }

        if (mp->mnt_flag & MNT_EXPUBLIC)
                vfs_setpublicfs(NULL, NULL, NULL);

        vfs_msync(mp, MNT_WAIT);
        async_flag = mp->mnt_flag & MNT_ASYNC;
        mp->mnt_flag &=~ MNT_ASYNC;
        cache_purgevfs(mp);     /* remove cache entries for this file sys */
        if (mp->mnt_syncer != NULL)
                vrele(mp->mnt_syncer);
        if (((mp->mnt_flag & MNT_RDONLY) ||
             (error = VFS_SYNC(mp, MNT_WAIT)) == 0) ||
            (flags & MNT_FORCE))
                error = VFS_UNMOUNT(mp, flags);
        if (error) {
                if (mp->mnt_syncer == NULL)
                        vfs_allocate_syncvnode(mp);
                mp->mnt_kern_flag &= ~(MNTK_UNMOUNT | MNTK_UNMOUNTF);
                mp->mnt_flag |= async_flag;
                lockmgr(&mp->mnt_lock, LK_RELEASE);
                if (mp->mnt_kern_flag & MNTK_MWAIT)
                        wakeup(mp);
                return (error);
        }
        /*
         * Clean up any journals still associated with the mount after
         * filesystem activity has ceased.
         */
        journal_remove_all_journals(mp, 
            ((flags & MNT_FORCE) ? MC_JOURNAL_STOP_IMM : 0));

        mountlist_remove(mp);

        /*
         * Remove any installed vnode ops here so the individual VFSs don't
         * have to.
         */
        vfs_rm_vnodeops(&mp->mnt_vn_coherency_ops);
        vfs_rm_vnodeops(&mp->mnt_vn_journal_ops);
        vfs_rm_vnodeops(&mp->mnt_vn_norm_ops);
        vfs_rm_vnodeops(&mp->mnt_vn_spec_ops);
        vfs_rm_vnodeops(&mp->mnt_vn_fifo_ops);

        if ((coveredvp = mp->mnt_vnodecovered) != NULLVP) {
                coveredvp->v_mountedhere = NULL;
                vrele(coveredvp);
                cache_drop(mp->mnt_ncp);
                mp->mnt_ncp = NULL;
        }
        mp->mnt_vfc->vfc_refcount--;
        if (!TAILQ_EMPTY(&mp->mnt_nvnodelist))
                panic("unmount: dangling vnode");
        lockmgr(&mp->mnt_lock, LK_RELEASE);
        if (mp->mnt_kern_flag & MNTK_MWAIT)
                wakeup(mp);
        free(mp, M_MOUNT);
        return (0);
}

/*
 * Sync each mounted filesystem.
 */

#ifdef DEBUG
static int syncprt = 0;
SYSCTL_INT(_debug, OID_AUTO, syncprt, CTLFLAG_RW, &syncprt, 0, "");
#endif /* DEBUG */

static int sync_callback(struct mount *mp, void *data);

/* ARGSUSED */
int
sync(struct sync_args *uap)
{
        mountlist_scan(sync_callback, NULL, MNTSCAN_FORWARD);
#ifdef DEBUG
        /*
         * print out buffer pool stat information on each sync() call.
         */
        if (syncprt)
                vfs_bufstats();
#endif /* DEBUG */
        return (0);
}

static
int
sync_callback(struct mount *mp, void *data __unused)
{
        int asyncflag;

        if ((mp->mnt_flag & MNT_RDONLY) == 0) {
                asyncflag = mp->mnt_flag & MNT_ASYNC;
                mp->mnt_flag &= ~MNT_ASYNC;
                vfs_msync(mp, MNT_NOWAIT);
                VFS_SYNC(mp, MNT_NOWAIT);
                mp->mnt_flag |= asyncflag;
        }
        return(0);
}

/* XXX PRISON: could be per prison flag */
static int prison_quotas;
#if 0
SYSCTL_INT(_kern_prison, OID_AUTO, quotas, CTLFLAG_RW, &prison_quotas, 0, "");
#endif

/*
 *  quotactl_args(char *path, int fcmd, int uid, caddr_t arg)
 *
 * Change filesystem quotas.
 */
/* ARGSUSED */
int
quotactl(struct quotactl_args *uap)
{
        struct nlookupdata nd;
        struct thread *td;
        struct proc *p;
        struct mount *mp;
        int error;

        td = curthread;
        p = td->td_proc;
        if (p->p_ucred->cr_prison && !prison_quotas)
                return (EPERM);

        error = nlookup_init(&nd, uap->path, UIO_USERSPACE, NLC_FOLLOW);
        if (error == 0)
                error = nlookup(&nd);
        if (error == 0) {
                mp = nd.nl_ncp->nc_mount;
                error = VFS_QUOTACTL(mp, uap->cmd, uap->uid,
                                    uap->arg, nd.nl_cred);
        }
        nlookup_done(&nd);
        return (error);
}

/*
 * mountctl(char *path, int op, int fd, const void *ctl, int ctllen,
 *              void *buf, int buflen)
 *
 * This function operates on a mount point and executes the specified
 * operation using the specified control data, and possibly returns data.
 *
 * The actual number of bytes stored in the result buffer is returned, 0
 * if none, otherwise an error is returned.
 */
/* ARGSUSED */
int
mountctl(struct mountctl_args *uap)
{
        struct thread *td = curthread;
        struct proc *p = td->td_proc;
        struct filedesc *fdp = p->p_fd;
        struct file *fp;
        void *ctl = NULL;
        void *buf = NULL;
        char *path = NULL;
        int error;

        /*
         * Sanity and permissions checks.  We must be root.
         */
        KKASSERT(p);
        if (p->p_ucred->cr_prison != NULL)
                return (EPERM);
        if ((error = suser(td)) != 0)
                return (error);

        /*
         * Argument length checks
         */
        if (uap->ctllen < 0 || uap->ctllen > 1024)
                return (EINVAL);
        if (uap->buflen < 0 || uap->buflen > 16 * 1024)
                return (EINVAL);
        if (uap->path == NULL)
                return (EINVAL);

        /*
         * Allocate the necessary buffers and copyin data
         */
        path = zalloc(namei_zone);
        error = copyinstr(uap->path, path, MAXPATHLEN, NULL);
        if (error)
                goto done;

        if (uap->ctllen) {
                ctl = malloc(uap->ctllen + 1, M_TEMP, M_WAITOK|M_ZERO);
                error = copyin(uap->ctl, ctl, uap->ctllen);
                if (error)
                        goto done;
        }
        if (uap->buflen)
                buf = malloc(uap->buflen + 1, M_TEMP, M_WAITOK|M_ZERO);

        /*
         * Validate the descriptor
         */
        if (uap->fd == -1) {
                fp = NULL;
        } else if ((u_int)uap->fd >= fdp->fd_nfiles ||
            (fp = fdp->fd_files[uap->fd].fp) == NULL) {
                error = EBADF;
                goto done;
        }
        if (fp)
                fhold(fp);

        /*
         * Execute the internal kernel function and clean up.
         */
        error = kern_mountctl(path, uap->op, fp, ctl, uap->ctllen, buf, uap->buflen, &uap->sysmsg_result);
        if (fp)
                fdrop(fp);
        if (error == 0 && uap->sysmsg_result > 0)
                error = copyout(buf, uap->buf, uap->sysmsg_result);
done:
        if (path)
                zfree(namei_zone, path);
        if (ctl)
                free(ctl, M_TEMP);
        if (buf)
                free(buf, M_TEMP);
        return (error);
}

/*
 * Execute a mount control operation by resolving the path to a mount point
 * and calling vop_mountctl().  
 */
int
kern_mountctl(const char *path, int op, struct file *fp, 
                const void *ctl, int ctllen, 
                void *buf, int buflen, int *res)
{
        struct vnode *vp;
        struct mount *mp;
        struct nlookupdata nd;
        int error;

        *res = 0;
        vp = NULL;
        error = nlookup_init(&nd, path, UIO_SYSSPACE, NLC_FOLLOW);
        if (error == 0)
                error = nlookup(&nd);
        if (error == 0)
                error = cache_vget(nd.nl_ncp, nd.nl_cred, LK_EXCLUSIVE, &vp);
        nlookup_done(&nd);
        if (error)
                return (error);

        mp = vp->v_mount;

        /*
         * Must be the root of the filesystem
         */
        if ((vp->v_flag & VROOT) == 0) {
                vput(vp);
                return (EINVAL);
        }
        error = vop_mountctl(mp->mnt_vn_use_ops, op, fp, ctl, ctllen, 
                                buf, buflen, res);
        vput(vp);
        return (error);
}

int
kern_statfs(struct nlookupdata *nd, struct statfs *buf)
{
        struct thread *td = curthread;
        struct proc *p = td->td_proc;
        struct mount *mp;
        struct statfs *sp;
        char *fullpath, *freepath;
        int error;

        if ((error = nlookup(nd)) != 0)
                return (error);
        mp = nd->nl_ncp->nc_mount;
        sp = &mp->mnt_stat;
        if ((error = VFS_STATFS(mp, sp, nd->nl_cred)) != 0)
                return (error);

        error = cache_fullpath(p, mp->mnt_ncp, &fullpath, &freepath);
        if (error)
                return(error);
        bzero(sp->f_mntonname, sizeof(sp->f_mntonname));
        strlcpy(sp->f_mntonname, fullpath, sizeof(sp->f_mntonname));
        free(freepath, M_TEMP);

        sp->f_flags = mp->mnt_flag & MNT_VISFLAGMASK;
        bcopy(sp, buf, sizeof(*buf));
        /* Only root should have access to the fsid's. */
        if (suser(td))
                buf->f_fsid.val[0] = buf->f_fsid.val[1] = 0;
        return (0);
}

/*
 * statfs_args(char *path, struct statfs *buf)
 *
 * Get filesystem statistics.
 */
int
statfs(struct statfs_args *uap)
{
        struct nlookupdata nd;
        struct statfs buf;
        int error;

        error = nlookup_init(&nd, uap->path, UIO_USERSPACE, NLC_FOLLOW);
        if (error == 0)
                error = kern_statfs(&nd, &buf);
        nlookup_done(&nd);
        if (error == 0)
                error = copyout(&buf, uap->buf, sizeof(*uap->buf));
        return (error);
}

int
kern_fstatfs(int fd, struct statfs *buf)
{
        struct thread *td = curthread;
        struct proc *p = td->td_proc;
        struct file *fp;
        struct mount *mp;
        struct statfs *sp;
        char *fullpath, *freepath;
        int error;

        KKASSERT(p);
        error = getvnode(p->p_fd, fd, &fp);
        if (error)
                return (error);
        mp = ((struct vnode *)fp->f_data)->v_mount;
        if (mp == NULL)
                return (EBADF);
        if (fp->f_cred == NULL)
                return (EINVAL);
        sp = &mp->mnt_stat;
        error = VFS_STATFS(mp, sp, fp->f_cred);
        if (error)
                return (error);

        error = cache_fullpath(p, mp->mnt_ncp, &fullpath, &freepath);
        if (error)
                return(error);
        bzero(sp->f_mntonname, sizeof(sp->f_mntonname));
        strlcpy(sp->f_mntonname, fullpath, sizeof(sp->f_mntonname));
        free(freepath, M_TEMP);

        sp->f_flags = mp->mnt_flag & MNT_VISFLAGMASK;
        bcopy(sp, buf, sizeof(*buf));

        /* Only root should have access to the fsid's. */
        if (suser(td))
                buf->f_fsid.val[0] = buf->f_fsid.val[1] = 0;
        return (0);
}

/*
 * fstatfs_args(int fd, struct statfs *buf)
 *
 * Get filesystem statistics.
 */
int
fstatfs(struct fstatfs_args *uap)
{
        struct statfs buf;
        int error;

        error = kern_fstatfs(uap->fd, &buf);

        if (error == 0)
                error = copyout(&buf, uap->buf, sizeof(*uap->buf));
        return (error);
}

/*
 * getfsstat_args(struct statfs *buf, long bufsize, int flags)
 *
 * Get statistics on all filesystems.
 */

struct getfsstat_info {
        struct statfs *sfsp;
        long count;
        long maxcount;
        int error;
        int flags;
        int is_chrooted;
        struct proc *p;
};

static int getfsstat_callback(struct mount *, void *);

/* ARGSUSED */
int
getfsstat(struct getfsstat_args *uap)
{
        struct thread *td = curthread;
        struct proc *p = td->td_proc;
        struct getfsstat_info info;

        bzero(&info, sizeof(info));
        if (p != NULL && (p->p_fd->fd_nrdir->nc_flag & NCF_ROOT) == 0)
                info.is_chrooted = 1;
        else
                info.is_chrooted = 0;

        info.maxcount = uap->bufsize / sizeof(struct statfs);
        info.sfsp = uap->buf;
        info.count = 0;
        info.flags = uap->flags;
        info.p = p;

        mountlist_scan(getfsstat_callback, &info, MNTSCAN_FORWARD);
        if (info.sfsp && info.count > info.maxcount)
                uap->sysmsg_result = info.maxcount;
        else
                uap->sysmsg_result = info.count;
        return (info.error);
}

static int
getfsstat_callback(struct mount *mp, void *data)
{
        struct getfsstat_info *info = data;
        struct statfs *sp;
        char *freepath;
        char *fullpath;
        int error;

        if (info->sfsp && info->count < info->maxcount) {
                if (info->is_chrooted && !chroot_visible_mnt(mp, info->p))
                        return(0);
                sp = &mp->mnt_stat;

                /*
                 * If MNT_NOWAIT or MNT_LAZY is specified, do not
                 * refresh the fsstat cache. MNT_NOWAIT or MNT_LAZY
                 * overrides MNT_WAIT.
                 */
                if (((info->flags & (MNT_LAZY|MNT_NOWAIT)) == 0 ||
                    (info->flags & MNT_WAIT)) &&
                    (error = VFS_STATFS(mp, sp, info->p->p_ucred))) {
                        return(0);
                }
                sp->f_flags = mp->mnt_flag & MNT_VISFLAGMASK;

                error = cache_fullpath(info->p, mp->mnt_ncp,
                                        &fullpath, &freepath);
                if (error) {
                        info->error = error;
                        return(-1);
                }
                bzero(sp->f_mntonname, sizeof(sp->f_mntonname));
                strlcpy(sp->f_mntonname, fullpath, sizeof(sp->f_mntonname));
                free(freepath, M_TEMP);

                error = copyout(sp, info->sfsp, sizeof(*sp));
                if (error) {
                        info->error = error;
                        return (-1);
                }
                ++info->sfsp;
        }
        info->count++;
        return(0);
}

/*
 * fchdir_args(int fd)
 *
 * Change current working directory to a given file descriptor.
 */
/* ARGSUSED */
int
fchdir(struct fchdir_args *uap)
{
        struct thread *td = curthread;
        struct proc *p = td->td_proc;
        struct filedesc *fdp = p->p_fd;
        struct vnode *vp, *ovp;
        struct mount *mp;
        struct file *fp;
        struct namecache *ncp, *oncp;
        struct namecache *nct;
        int error;

        if ((error = getvnode(fdp, uap->fd, &fp)) != 0)
                return (error);
        vp = (struct vnode *)fp->f_data;
        vref(vp);
        vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
        if (vp->v_type != VDIR || fp->f_ncp == NULL)
                error = ENOTDIR;
        else
                error = VOP_ACCESS(vp, VEXEC, p->p_ucred);
        if (error) {
                vput(vp);
                return (error);
        }
        ncp = cache_hold(fp->f_ncp);
        while (!error && (mp = vp->v_mountedhere) != NULL) {
                error = nlookup_mp(mp, &nct);
                if (error == 0) {
                        cache_unlock(nct);      /* leave ref intact */
                        vput(vp);
                        vp = nct->nc_vp;
                        error = vget(vp, LK_SHARED);
                        KKASSERT(error == 0);
                        cache_drop(ncp);
                        ncp = nct;
                }
        }
        if (error == 0) {
                ovp = fdp->fd_cdir;
                oncp = fdp->fd_ncdir;
                VOP_UNLOCK(vp, 0);      /* leave ref intact */
                fdp->fd_cdir = vp;
                fdp->fd_ncdir = ncp;
                cache_drop(oncp);
                vrele(ovp);
        } else {
                cache_drop(ncp);
                vput(vp);
        }
        return (error);
}

int
kern_chdir(struct nlookupdata *nd)
{
        struct thread *td = curthread;
        struct proc *p = td->td_proc;
        struct filedesc *fdp = p->p_fd;
        struct vnode *vp, *ovp;
        struct namecache *oncp;
        int error;

        if ((error = nlookup(nd)) != 0)
                return (error);
        if ((vp = nd->nl_ncp->nc_vp) == NULL)
                return (ENOENT);
        if ((error = vget(vp, LK_SHARED)) != 0)
                return (error);

        error = checkvp_chdir(vp, td);
        VOP_UNLOCK(vp, 0);
        if (error == 0) {
                ovp = fdp->fd_cdir;
                oncp = fdp->fd_ncdir;
                cache_unlock(nd->nl_ncp);       /* leave reference intact */
                fdp->fd_ncdir = nd->nl_ncp;
                fdp->fd_cdir = vp;
                cache_drop(oncp);
                vrele(ovp);
                nd->nl_ncp = NULL;
        } else {
                vrele(vp);
        }
        return (error);
}

/*
 * chdir_args(char *path)
 *
 * Change current working directory (``.'').
 */
int
chdir(struct chdir_args *uap)
{
        struct nlookupdata nd;
        int error;

        error = nlookup_init(&nd, uap->path, UIO_USERSPACE, NLC_FOLLOW);
        if (error == 0)
                error = kern_chdir(&nd);
        nlookup_done(&nd);
        return (error);
}

/*
 * Helper function for raised chroot(2) security function:  Refuse if
 * any filedescriptors are open directories.
 */
static int
chroot_refuse_vdir_fds(fdp)
        struct filedesc *fdp;
{
        struct vnode *vp;
        struct file *fp;
        int error;
        int fd;

        for (fd = 0; fd < fdp->fd_nfiles ; fd++) {
                error = getvnode(fdp, fd, &fp);
                if (error)
                        continue;
                vp = (struct vnode *)fp->f_data;
                if (vp->v_type != VDIR)
                        continue;
                return(EPERM);
        }
        return (0);
}

/*
 * This sysctl determines if we will allow a process to chroot(2) if it
 * has a directory open:
 *      0: disallowed for all processes.
 *      1: allowed for processes that were not already chroot(2)'ed.
 *      2: allowed for all processes.
 */

static int chroot_allow_open_directories = 1;

SYSCTL_INT(_kern, OID_AUTO, chroot_allow_open_directories, CTLFLAG_RW,
     &chroot_allow_open_directories, 0, "");

/*
 * chroot to the specified namecache entry.  We obtain the vp from the
 * namecache data.  The passed ncp must be locked and referenced and will
 * remain locked and referenced on return.
 */
int
kern_chroot(struct namecache *ncp)
{
        struct thread *td = curthread;
        struct proc *p = td->td_proc;
        struct filedesc *fdp = p->p_fd;
        struct vnode *vp;
        int error;

        /*
         * Only root can chroot
         */
        if ((error = suser_cred(p->p_ucred, PRISON_ROOT)) != 0)
                return (error);

        /*
         * Disallow open directory descriptors (fchdir() breakouts).
         */
        if (chroot_allow_open_directories == 0 ||
           (chroot_allow_open_directories == 1 && fdp->fd_rdir != rootvnode)) {
                if ((error = chroot_refuse_vdir_fds(fdp)) != 0)
                        return (error);
        }
        if ((vp = ncp->nc_vp) == NULL)
                return (ENOENT);

        if ((error = vget(vp, LK_SHARED)) != 0)
                return (error);

        /*
         * Check the validity of vp as a directory to change to and 
         * associate it with rdir/jdir.
         */
        error = checkvp_chdir(vp, td);
        VOP_UNLOCK(vp, 0);      /* leave reference intact */
        if (error == 0) {
                vrele(fdp->fd_rdir);
                fdp->fd_rdir = vp;      /* reference inherited by fd_rdir */
                cache_drop(fdp->fd_nrdir);
                fdp->fd_nrdir = cache_hold(ncp);
                if (fdp->fd_jdir == NULL) {
                        fdp->fd_jdir = vp;
                        vref(fdp->fd_jdir);
                        fdp->fd_njdir = cache_hold(ncp);
                }
        } else {
                vrele(vp);
        }
        return (error);
}

/*
 * chroot_args(char *path)
 *
 * Change notion of root (``/'') directory.
 */
/* ARGSUSED */
int
chroot(struct chroot_args *uap)
{
        struct thread *td = curthread;
        struct nlookupdata nd;
        int error;

        KKASSERT(td->td_proc);
        error = nlookup_init(&nd, uap->path, UIO_USERSPACE, NLC_FOLLOW);
        if (error) {
                nlookup_done(&nd);
                return(error);
        }
        error = nlookup(&nd);
        if (error == 0)
                error = kern_chroot(nd.nl_ncp);
        nlookup_done(&nd);
        return(error);
}

/*
 * Common routine for chroot and chdir.  Given a locked, referenced vnode,
 * determine whether it is legal to chdir to the vnode.  The vnode's state
 * is not changed by this call.
 */
int
checkvp_chdir(struct vnode *vp, struct thread *td)
{
        int error;

        if (vp->v_type != VDIR)
                error = ENOTDIR;
        else
                error = VOP_ACCESS(vp, VEXEC, td->td_proc->p_ucred);
        return (error);
}

int
kern_open(struct nlookupdata *nd, int oflags, int mode, int *res)
{
        struct thread *td = curthread;
        struct proc *p = td->td_proc;
        struct lwp *lp = td->td_lwp;
        struct filedesc *fdp = p->p_fd;
        int cmode, flags;
        struct file *nfp;
        struct file *fp;
        struct vnode *vp;
        int type, indx, error;
        struct flock lf;

        if ((oflags & O_ACCMODE) == O_ACCMODE)
                return (EINVAL);
        flags = FFLAGS(oflags);
        error = falloc(p, &nfp, NULL);
        if (error)
                return (error);
        fp = nfp;
        cmode = ((mode &~ fdp->fd_cmask) & ALLPERMS) &~ S_ISTXT;

        /*
         * XXX p_dupfd is a real mess.  It allows a device to return a
         * file descriptor to be duplicated rather then doing the open
         * itself.
         */
        lp->lwp_dupfd = -1;

        /*
         * Call vn_open() to do the lookup and assign the vnode to the 
         * file pointer.  vn_open() does not change the ref count on fp
         * and the vnode, on success, will be inherited by the file pointer
         * and unlocked.
         */
        nd->nl_flags |= NLC_LOCKVP;
        error = vn_open(nd, fp, flags, cmode);
        nlookup_done(nd);
        if (error) {
                /*
                 * handle special fdopen() case.  bleh.  dupfdopen() is
                 * responsible for dropping the old contents of ofiles[indx]
                 * if it succeeds.
                 *
                 * Note that if fsetfd() succeeds it will add a ref to fp
                 * which represents the fd_files[] assignment.  We must still
                 * drop our reference.
                 */
                if ((error == ENODEV || error == ENXIO) && lp->lwp_dupfd >= 0) {
                        if (fsetfd(p, fp, &indx) == 0) {
                                error = dupfdopen(fdp, indx, lp->lwp_dupfd, flags, error);
                                if (error == 0) {
                                        *res = indx;
                                        fdrop(fp);      /* our ref */
                                        return (0);
                                }
                                if (fdp->fd_files[indx].fp == fp) {
                                        funsetfd(fdp, indx);
                                        fdrop(fp);      /* fd_files[] ref */
                                }
                        }
                }
                fdrop(fp);      /* our ref */
                if (error == ERESTART)
                        error = EINTR;
                return (error);
        }

        /*
         * ref the vnode for ourselves so it can't be ripped out from under
         * is.  XXX need an ND flag to request that the vnode be returned
         * anyway.
         */
        vp = (struct vnode *)fp->f_data;
        vref(vp);
        if ((error = fsetfd(p, fp, &indx)) != 0) {
                fdrop(fp);
                vrele(vp);
                return (error);
        }

        /*
         * If no error occurs the vp will have been assigned to the file
         * pointer.
         */
        lp->lwp_dupfd = 0;

        /*
         * There should be 2 references on the file, one from the descriptor
         * table, and one for us.
         *
         * Handle the case where someone closed the file (via its file
         * descriptor) while we were blocked.  The end result should look
         * like opening the file succeeded but it was immediately closed.
         */
        if (fp->f_count == 1) {
                KASSERT(fdp->fd_files[indx].fp != fp,
                    ("Open file descriptor lost all refs"));
                vrele(vp);
                fo_close(fp);
                fdrop(fp);
                *res = indx;
                return 0;
        }

        if (flags & (O_EXLOCK | O_SHLOCK)) {
                lf.l_whence = SEEK_SET;
                lf.l_start = 0;
                lf.l_len = 0;
                if (flags & O_EXLOCK)
                        lf.l_type = F_WRLCK;
                else
                        lf.l_type = F_RDLCK;
                type = F_FLOCK;
                if ((flags & FNONBLOCK) == 0)
                        type |= F_WAIT;

                if ((error = VOP_ADVLOCK(vp, (caddr_t)fp, F_SETLK, &lf, type)) != 0) {
                        /*
                         * lock request failed.  Normally close the descriptor
                         * but handle the case where someone might have dup()d
                         * it when we weren't looking.  One reference is
                         * owned by the descriptor array, the other by us.
                         */
                        vrele(vp);
                        if (fdp->fd_files[indx].fp == fp) {
                                funsetfd(fdp, indx);
                                fdrop(fp);
                        }
                        fdrop(fp);
                        return (error);
                }
                fp->f_flag |= FHASLOCK;
        }

#if 0
        /*
         * Assert that all regular file vnodes were created with a object.
         */
        KASSERT(vp->v_type != VREG || vp->v_object != NULL,
                ("open: regular file has no backing object after vn_open"));
#endif

        vrele(vp);

        /*
         * release our private reference, leaving the one associated with the
         * descriptor table intact.
         */
        fdrop(fp);
        *res = indx;
        return (0);
}

/*
 * open_args(char *path, int flags, int mode)
 *
 * Check permissions, allocate an open file structure,
 * and call the device open routine if any.
 */
int
open(struct open_args *uap)
{
        struct nlookupdata nd;
        int error;

        error = nlookup_init(&nd, uap->path, UIO_USERSPACE, NLC_FOLLOW);
        if (error == 0) {
                error = kern_open(&nd, uap->flags,
                                    uap->mode, &uap->sysmsg_result);
        }
        nlookup_done(&nd);
        return (error);
}

int
kern_mknod(struct nlookupdata *nd, int mode, int dev)
{
        struct namecache *ncp;
        struct thread *td = curthread;
        struct proc *p = td->td_proc;
        struct vnode *vp;
        struct vattr vattr;
        int error;
        int whiteout = 0;

        KKASSERT(p);

        switch (mode & S_IFMT) {
        case S_IFCHR:
        case S_IFBLK:
                error = suser(td);
                break;
        default:
                error = suser_cred(p->p_ucred, PRISON_ROOT);
                break;
        }
        if (error)
                return (error);

        bwillwrite();
        nd->nl_flags |= NLC_CREATE;
        if ((error = nlookup(nd)) != 0)
                return (error);
        ncp = nd->nl_ncp;
        if (ncp->nc_vp)
                return (EEXIST);

        VATTR_NULL(&vattr);
        vattr.va_mode = (mode & ALLPERMS) &~ p->p_fd->fd_cmask;
        vattr.va_rdev = dev;
        whiteout = 0;

        switch (mode & S_IFMT) {
        case S_IFMT:    /* used by badsect to flag bad sectors */
                vattr.va_type = VBAD;
                break;
        case S_IFCHR:
                vattr.va_type = VCHR;
                break;
        case S_IFBLK:
                vattr.va_type = VBLK;
                break;
        case S_IFWHT:
                whiteout = 1;
                break;
        default:
                error = EINVAL;
                break;
        }
        if (error == 0) {
                if (whiteout) {
                        error = VOP_NWHITEOUT(ncp, nd->nl_cred, NAMEI_CREATE);
                } else {
                        vp = NULL;
                        error = VOP_NMKNOD(ncp, &vp, nd->nl_cred, &vattr);
                        if (error == 0)
                                vput(vp);
                }
        }
        return (error);
}

/*
 * mknod_args(char *path, int mode, int dev)
 *
 * Create a special file.
 */
int
mknod(struct mknod_args *uap)
{
        struct nlookupdata nd;
        int error;

        error = nlookup_init(&nd, uap->path, UIO_USERSPACE, 0);
        if (error == 0)
                error = kern_mknod(&nd, uap->mode, uap->dev);
        nlookup_done(&nd);
        return (error);
}

int
kern_mkfifo(struct nlookupdata *nd, int mode)
{
        struct namecache *ncp;
        struct thread *td = curthread;
        struct proc *p = td->td_proc;
        struct vattr vattr;
        struct vnode *vp;
        int error;

        bwillwrite();

        nd->nl_flags |= NLC_CREATE;
        if ((error = nlookup(nd)) != 0)
                return (error);
        ncp = nd->nl_ncp;
        if (ncp->nc_vp)
                return (EEXIST);

        VATTR_NULL(&vattr);
        vattr.va_type = VFIFO;
        vattr.va_mode = (mode & ALLPERMS) &~ p->p_fd->fd_cmask;
        vp = NULL;
        error = VOP_NMKNOD(ncp, &vp, nd->nl_cred, &vattr);
        if (error == 0)
                vput(vp);
        return (error);
}

/*
 * mkfifo_args(char *path, int mode)
 *
 * Create a named pipe.
 */
int
mkfifo(struct mkfifo_args *uap)
{
        struct nlookupdata nd;
        int error;

        error = nlookup_init(&nd, uap->path, UIO_USERSPACE, 0);
        if (error == 0)
                error = kern_mkfifo(&nd, uap->mode);
        nlookup_done(&nd);
        return (error);
}

static int hardlink_check_uid = 0;
SYSCTL_INT(_kern, OID_AUTO, hardlink_check_uid, CTLFLAG_RW,
    &hardlink_check_uid, 0, 
    "Unprivileged processes cannot create hard links to files owned by other "
    "users");
static int hardlink_check_gid = 0;
SYSCTL_INT(_kern, OID_AUTO, hardlink_check_gid, CTLFLAG_RW,
    &hardlink_check_gid, 0,
    "Unprivileged processes cannot create hard links to files owned by other "
    "groups");

static int
can_hardlink(struct vnode *vp, struct thread *td, struct ucred *cred)
{
        struct vattr va;
        int error;

        /*
         * Shortcut if disabled
         */
        if (hardlink_check_uid == 0 && hardlink_check_gid == 0)
                return (0);

        /*
         * root cred can always hardlink
         */
        if (suser_cred(cred, PRISON_ROOT) == 0)
                return (0);

        /*
         * Otherwise only if the originating file is owned by the
         * same user or group.  Note that any group is allowed if
         * the file is owned by the caller.
         */
        error = VOP_GETATTR(vp, &va);
        if (error != 0)
                return (error);
        
        if (hardlink_check_uid) {
                if (cred->cr_uid != va.va_uid)
                        return (EPERM);
        }
        
        if (hardlink_check_gid) {
                if (cred->cr_uid != va.va_uid && !groupmember(va.va_gid, cred))
                        return (EPERM);
        }

        return (0);
}

int
kern_link(struct nlookupdata *nd, struct nlookupdata *linknd)
{
        struct thread *td = curthread;
        struct vnode *vp;
        int error;

        /*
         * Lookup the source and obtained a locked vnode.
         *
         * XXX relookup on vget failure / race ?
         */
        bwillwrite();
        if ((error = nlookup(nd)) != 0)
                return (error);
        vp = nd->nl_ncp->nc_vp;
        KKASSERT(vp != NULL);
        if (vp->v_type == VDIR)
                return (EPERM);         /* POSIX */
        if ((error = vget(vp, LK_EXCLUSIVE)) != 0)
                return (error);

        /*
         * Unlock the source so we can lookup the target without deadlocking
         * (XXX vp is locked already, possible other deadlock?).  The target
         * must not exist.
         */
        KKASSERT(nd->nl_flags & NLC_NCPISLOCKED);
        nd->nl_flags &= ~NLC_NCPISLOCKED;
        cache_unlock(nd->nl_ncp);

        linknd->nl_flags |= NLC_CREATE;
        if ((error = nlookup(linknd)) != 0) {
                vput(vp);
                return (error);
        }
        if (linknd->nl_ncp->nc_vp) {
                vput(vp);
                return (EEXIST);
        }

        /*
         * Finally run the new API VOP.
         */
        error = can_hardlink(vp, td, td->td_proc->p_ucred);
        if (error == 0)
                error = VOP_NLINK(linknd->nl_ncp, vp, linknd->nl_cred);
        vput(vp);
        return (error);
}

/*
 * link_args(char *path, char *link)
 *
 * Make a hard file link.
 */
int
link(struct link_args *uap)
{
        struct nlookupdata nd, linknd;
        int error;

        error = nlookup_init(&nd, uap->path, UIO_USERSPACE, NLC_FOLLOW);
        if (error == 0) {
                error = nlookup_init(&linknd, uap->link, UIO_USERSPACE, 0);
                if (error == 0)
                        error = kern_link(&nd, &linknd);
                nlookup_done(&linknd);
        }
        nlookup_done(&nd);
        return (error);
}

int
kern_symlink(struct nlookupdata *nd, char *path, int mode)
{
        struct namecache *ncp;
        struct vattr vattr;
        struct vnode *vp;
        int error;

        bwillwrite();
        nd->nl_flags |= NLC_CREATE;
        if ((error = nlookup(nd)) != 0)
                return (error);
        ncp = nd->nl_ncp;
        if (ncp->nc_vp)
                return (EEXIST);

        VATTR_NULL(&vattr);
        vattr.va_mode = mode;
        error = VOP_NSYMLINK(ncp, &vp, nd->nl_cred, &vattr, path);
        if (error == 0)
                vput(vp);
        return (error);
}

/*
 * symlink(char *path, char *link)
 *
 * Make a symbolic link.
 */
int
symlink(struct symlink_args *uap)
{
        struct thread *td = curthread;
        struct nlookupdata nd;
        char *path;
        int error;
        int mode;

        path = zalloc(namei_zone);
        error = copyinstr(uap->path, path, MAXPATHLEN, NULL);
        if (error == 0) {
                error = nlookup_init(&nd, uap->link, UIO_USERSPACE, 0);
                if (error == 0) {
                        mode = ACCESSPERMS & ~td->td_proc->p_fd->fd_cmask;
                        error = kern_symlink(&nd, path, mode);
                }
                nlookup_done(&nd);
        }
        zfree(namei_zone, path);
        return (error);
}

/*
 * undelete_args(char *path)
 *
 * Delete a whiteout from the filesystem.
 */
/* ARGSUSED */
int
undelete(struct undelete_args *uap)
{
        struct nlookupdata nd;
        int error;

        error = nlookup_init(&nd, uap->path, UIO_USERSPACE, 0);
        bwillwrite();
        nd.nl_flags |= NLC_DELETE;
        if (error == 0)
                error = nlookup(&nd);
        if (error == 0)
                error = VOP_NWHITEOUT(nd.nl_ncp, nd.nl_cred, NAMEI_DELETE);
        nlookup_done(&nd);
        return (error);
}

int
kern_unlink(struct nlookupdata *nd)
{
        struct namecache *ncp;
        int error;

        bwillwrite();
        nd->nl_flags |= NLC_DELETE;
        if ((error = nlookup(nd)) != 0)
                return (error);
        ncp = nd->nl_ncp;
        error = VOP_NREMOVE(ncp, nd->nl_cred);
        return (error);
}

/*
 * unlink_args(char *path)
 *
 * Delete a name from the filesystem.
 */
int
unlink(struct unlink_args *uap)
{
        struct nlookupdata nd;
        int error;

        error = nlookup_init(&nd, uap->path, UIO_USERSPACE, 0);
        if (error == 0)
                error = kern_unlink(&nd);
        nlookup_done(&nd);
        return (error);
}

int
kern_lseek(int fd, off_t offset, int whence, off_t *res)
{
        struct thread *td = curthread;
        struct proc *p = td->td_proc;
        struct filedesc *fdp = p->p_fd;
        struct file *fp;
        struct vattr vattr;
        int error;

        if ((u_int)fd >= fdp->fd_nfiles ||
            (fp = fdp->fd_files[fd].fp) == NULL)
                return (EBADF);
        if (fp->f_type != DTYPE_VNODE)
                return (ESPIPE);
        switch (whence) {
        case L_INCR:
                fp->f_offset += offset;
                break;
        case L_XTND:
                error=VOP_GETATTR((struct vnode *)fp->f_data, &vattr);
                if (error)
                        return (error);
                fp->f_offset = offset + vattr.va_size;
                break;
        case L_SET:
                fp->f_offset = offset;
                break;
        default:
                return (EINVAL);
        }
        *res = fp->f_offset;
        return (0);
}

/*
 * lseek_args(int fd, int pad, off_t offset, int whence)
 *
 * Reposition read/write file offset.
 */
int
lseek(struct lseek_args *uap)
{
        int error;

        error = kern_lseek(uap->fd, uap->offset, uap->whence,
            &uap->sysmsg_offset);

        return (error);
}

int
kern_access(struct nlookupdata *nd, int aflags)
{
        struct vnode *vp;
        int error, flags;

        if ((error = nlookup(nd)) != 0)
                return (error);
retry:
        error = cache_vget(nd->nl_ncp, nd->nl_cred, LK_EXCLUSIVE, &vp);
        if (error)
                return (error);

        /* Flags == 0 means only check for existence. */
        if (aflags) {
                flags = 0;
                if (aflags & R_OK)
                        flags |= VREAD;
                if (aflags & W_OK)
                        flags |= VWRITE;
                if (aflags & X_OK)
                        flags |= VEXEC;
                if ((flags & VWRITE) == 0 || (error = vn_writechk(vp)) == 0)
                        error = VOP_ACCESS(vp, flags, nd->nl_cred);

                /*
                 * If the file handle is stale we have to re-resolve the
                 * entry.  This is a hack at the moment.
                 */
                if (error == ESTALE) {
                        cache_setunresolved(nd->nl_ncp);
                        error = cache_resolve(nd->nl_ncp, nd->nl_cred);
                        if (error == 0) {
                                vput(vp);
                                vp = NULL;
                                goto retry;
                        }
                }
        }
        vput(vp);
        return (error);
}

/*
 * access_args(char *path, int flags)
 *
 * Check access permissions.
 */
int
access(struct access_args *uap)
{
        struct nlookupdata nd;
        int error;

        error = nlookup_init(&nd, uap->path, UIO_USERSPACE, NLC_FOLLOW);
        if (error == 0)
                error = kern_access(&nd, uap->flags);
        nlookup_done(&nd);
        return (error);
}

int
kern_stat(struct nlookupdata *nd, struct stat *st)
{
        int error;
        struct vnode *vp;
        thread_t td;

        if ((error = nlookup(nd)) != 0)
                return (error);
again:
        if ((vp = nd->nl_ncp->nc_vp) == NULL)
                return (ENOENT);

        td = curthread;
        if ((error = vget(vp, LK_SHARED)) != 0)
                return (error);
        error = vn_stat(vp, st, nd->nl_cred);

        /*
         * If the file handle is stale we have to re-resolve the entry.  This
         * is a hack at the moment.
         */
        if (error == ESTALE) {
                cache_setunresolved(nd->nl_ncp);
                error = cache_resolve(nd->nl_ncp, nd->nl_cred);
                if (error == 0) {
                        vput(vp);
                        goto again;
                }
        }
        vput(vp);
        return (error);
}

/*
 * stat_args(char *path, struct stat *ub)
 *
 * Get file status; this version follows links.
 */
int
stat(struct stat_args *uap)
{
        struct nlookupdata nd;
        struct stat st;
        int error;

        error = nlookup_init(&nd, uap->path, UIO_USERSPACE, NLC_FOLLOW);
        if (error == 0) {
                error = kern_stat(&nd, &st);
                if (error == 0)
                        error = copyout(&st, uap->ub, sizeof(*uap->ub));
        }
        nlookup_done(&nd);
        return (error);
}

/*
 * lstat_args(char *path, struct stat *ub)
 *
 * Get file status; this version does not follow links.
 */
int
lstat(struct lstat_args *uap)
{
        struct nlookupdata nd;
        struct stat st;
        int error;

        error = nlookup_init(&nd, uap->path, UIO_USERSPACE, 0);
        if (error == 0) {
                error = kern_stat(&nd, &st);
                if (error == 0)
                        error = copyout(&st, uap->ub, sizeof(*uap->ub));
        }
        nlookup_done(&nd);
        return (error);
}

/*
 * pathconf_Args(char *path, int name)
 *
 * Get configurable pathname variables.
 */
/* ARGSUSED */
int
pathconf(struct pathconf_args *uap)
{
        struct nlookupdata nd;
        struct vnode *vp;
        int error;

        vp = NULL;
        error = nlookup_init(&nd, uap->path, UIO_USERSPACE, NLC_FOLLOW);
        if (error == 0)
                error = nlookup(&nd);
        if (error == 0)
                error = cache_vget(nd.nl_ncp, nd.nl_cred, LK_EXCLUSIVE, &vp);
        nlookup_done(&nd);
        if (error == 0) {
                error = VOP_PATHCONF(vp, uap->name, uap->sysmsg_fds);
                vput(vp);
        }
        return (error);
}

/*
 * XXX: daver
 * kern_readlink isn't properly split yet.  There is a copyin burried
 * in VOP_READLINK().
 */
int
kern_readlink(struct nlookupdata *nd, char *buf, int count, int *res)
{
        struct thread *td = curthread;
        struct proc *p = td->td_proc;
        struct vnode *vp;
        struct iovec aiov;
        struct uio auio;
        int error;

        if ((error = nlookup(nd)) != 0)
                return (error);
        error = cache_vget(nd->nl_ncp, nd->nl_cred, LK_EXCLUSIVE, &vp);
        if (error)
                return (error);
        if (vp->v_type != VLNK) {
                error = EINVAL;
        } else {
                aiov.iov_base = buf;
                aiov.iov_len = count;
                auio.uio_iov = &aiov;
                auio.uio_iovcnt = 1;
                auio.uio_offset = 0;
                auio.uio_rw = UIO_READ;
                auio.uio_segflg = UIO_USERSPACE;
                auio.uio_td = td;
                auio.uio_resid = count;
                error = VOP_READLINK(vp, &auio, p->p_ucred);
        }
        vput(vp);
        *res = count - auio.uio_resid;
        return (error);
}

/*
 * readlink_args(char *path, char *buf, int count)
 *
 * Return target name of a symbolic link.
 */
int
readlink(struct readlink_args *uap)
{
        struct nlookupdata nd;
        int error;

        error = nlookup_init(&nd, uap->path, UIO_USERSPACE, 0);
        if (error == 0) {
                error = kern_readlink(&nd, uap->buf, uap->count,
                                        &uap->sysmsg_result);
        }
        nlookup_done(&nd);
        return (error);
}

static int
setfflags(struct vnode *vp, int flags)
{
        struct thread *td = curthread;
        struct proc *p = td->td_proc;
        int error;
        struct vattr vattr;

        /*
         * Prevent non-root users from setting flags on devices.  When
         * a device is reused, users can retain ownership of the device
         * if they are allowed to set flags and programs assume that
         * chown can't fail when done as root.
         */
        if ((vp->v_type == VCHR || vp->v_type == VBLK) && 
            ((error = suser_cred(p->p_ucred, PRISON_ROOT)) != 0))
                return (error);

        /*
         * note: vget is required for any operation that might mod the vnode
         * so VINACTIVE is properly cleared.
         */
        if ((error = vget(vp, LK_EXCLUSIVE)) == 0) {
                VATTR_NULL(&vattr);
                vattr.va_flags = flags;
                error = VOP_SETATTR(vp, &vattr, p->p_ucred);
                vput(vp);
        }
        return (error);
}

/*
 * chflags(char *path, int flags)
 *
 * Change flags of a file given a path name.
 */
/* ARGSUSED */
int
chflags(struct chflags_args *uap)
{
        struct nlookupdata nd;
        struct vnode *vp;
        int error;

        vp = NULL;
        error = nlookup_init(&nd, uap->path, UIO_USERSPACE, NLC_FOLLOW);
        /* XXX Add NLC flag indicating modifying operation? */
        if (error == 0)
                error = nlookup(&nd);
        if (error == 0)
                error = cache_vref(nd.nl_ncp, nd.nl_cred, &vp);
        nlookup_done(&nd);
        if (error == 0) {
                error = setfflags(vp, uap->flags);
                vrele(vp);
        }
        return (error);
}

/*
 * fchflags_args(int fd, int flags)
 *
 * Change flags of a file given a file descriptor.
 */
/* ARGSUSED */
int
fchflags(struct fchflags_args *uap)
{
        struct thread *td = curthread;
        struct proc *p = td->td_proc;
        struct file *fp;
        int error;

        if ((error = getvnode(p->p_fd, uap->fd, &fp)) != 0)
                return (error);
        return setfflags((struct vnode *) fp->f_data, uap->flags);
}

static int
setfmode(struct vnode *vp, int mode)
{
        struct thread *td = curthread;
        struct proc *p = td->td_proc;
        int error;
        struct vattr vattr;

        /*
         * note: vget is required for any operation that might mod the vnode
         * so VINACTIVE is properly cleared.
         */
        if ((error = vget(vp, LK_EXCLUSIVE)) == 0) {
                VATTR_NULL(&vattr);
                vattr.va_mode = mode & ALLPERMS;
                error = VOP_SETATTR(vp, &vattr, p->p_ucred);
                vput(vp);
        }
        return error;
}

int
kern_chmod(struct nlookupdata *nd, int mode)
{
        struct vnode *vp;
        int error;

        /* XXX Add NLC flag indicating modifying operation? */
        if ((error = nlookup(nd)) != 0)
                return (error);
        if ((error = cache_vref(nd->nl_ncp, nd->nl_cred, &vp)) != 0)
                return (error);
        error = setfmode(vp, mode);
        vrele(vp);
        return (error);
}

/*
 * chmod_args(char *path, int mode)
 *
 * Change mode of a file given path name.
 */
/* ARGSUSED */
int
chmod(struct chmod_args *uap)
{
        struct nlookupdata nd;
        int error;

        error = nlookup_init(&nd, uap->path, UIO_USERSPACE, NLC_FOLLOW);
        if (error == 0)
                error = kern_chmod(&nd, uap->mode);
        nlookup_done(&nd);
        return (error);
}

/*
 * lchmod_args(char *path, int mode)
 *
 * Change mode of a file given path name (don't follow links.)
 */
/* ARGSUSED */
int
lchmod(struct lchmod_args *uap)
{
        struct nlookupdata nd;
        int error;

        error = nlookup_init(&nd, uap->path, UIO_USERSPACE, 0);
        if (error == 0)
                error = kern_chmod(&nd, uap->mode);
        nlookup_done(&nd);
        return (error);
}

/*
 * fchmod_args(int fd, int mode)
 *
 * Change mode of a file given a file descriptor.
 */
/* ARGSUSED */
int
fchmod(struct fchmod_args *uap)
{
        struct thread *td = curthread;
        struct proc *p = td->td_proc;
        struct file *fp;
        int error;

        if ((error = getvnode(p->p_fd, uap->fd, &fp)) != 0)
                return (error);
        return setfmode((struct vnode *)fp->f_data, uap->mode);
}

static int
setfown(struct vnode *vp, uid_t uid, gid_t gid)
{
        struct thread *td = curthread;
        struct proc *p = td->td_proc;
        int error;
        struct vattr vattr;

        /*
         * note: vget is required for any operation that might mod the vnode
         * so VINACTIVE is properly cleared.
         */
        if ((error = vget(vp, LK_EXCLUSIVE)) == 0) {
                VATTR_NULL(&vattr);
                vattr.va_uid = uid;
                vattr.va_gid = gid;
                error = VOP_SETATTR(vp, &vattr, p->p_ucred);
                vput(vp);
        }
        return error;
}

int
kern_chown(struct nlookupdata *nd, int uid, int gid)
{
        struct vnode *vp;
        int error;

        /* XXX Add NLC flag indicating modifying operation? */
        if ((error = nlookup(nd)) != 0)
                return (error);
        if ((error = cache_vref(nd->nl_ncp, nd->nl_cred, &vp)) != 0)
                return (error);
        error = setfown(vp, uid, gid);
        vrele(vp);
        return (error);
}

/*
 * chown(char *path, int uid, int gid)
 *
 * Set ownership given a path name.
 */
int
chown(struct chown_args *uap)
{
        struct nlookupdata nd;
        int error;

        error = nlookup_init(&nd, uap->path, UIO_USERSPACE, NLC_FOLLOW);
        if (error == 0)
                error = kern_chown(&nd, uap->uid, uap->gid);
        nlookup_done(&nd);
        return (error);
}

/*
 * lchown_args(char *path, int uid, int gid)
 *
 * Set ownership given a path name, do not cross symlinks.
 */
int
lchown(struct lchown_args *uap)
{
        struct nlookupdata nd;
        int error;

        error = nlookup_init(&nd, uap->path, UIO_USERSPACE, 0);
        if (error == 0)
                error = kern_chown(&nd, uap->uid, uap->gid);
        nlookup_done(&nd);
        return (error);
}

/*
 * fchown_args(int fd, int uid, int gid)
 *
 * Set ownership given a file descriptor.
 */
/* ARGSUSED */
int
fchown(struct fchown_args *uap)
{
        struct thread *td = curthread;
        struct proc *p = td->td_proc;
        struct file *fp;
        int error;

        if ((error = getvnode(p->p_fd, uap->fd, &fp)) != 0)
                return (error);
        return setfown((struct vnode *)fp->f_data,
                uap->uid, uap->gid);
}

static int
getutimes(const struct timeval *tvp, struct timespec *tsp)
{
        struct timeval tv[2];

        if (tvp == NULL) {
                microtime(&tv[0]);
                TIMEVAL_TO_TIMESPEC(&tv[0], &tsp[0]);
                tsp[1] = tsp[0];
        } else {
                TIMEVAL_TO_TIMESPEC(&tvp[0], &tsp[0]);
                TIMEVAL_TO_TIMESPEC(&tvp[1], &tsp[1]);
        }
        return 0;
}

static int
setutimes(struct vnode *vp, const struct timespec *ts, int nullflag)
{
        struct thread *td = curthread;
        struct proc *p = td->td_proc;
        int error;
        struct vattr vattr;

        /*
         * note: vget is required for any operation that might mod the vnode
         * so VINACTIVE is properly cleared.
         */
        if ((error = vget(vp, LK_EXCLUSIVE)) == 0) {
                VATTR_NULL(&vattr);
                vattr.va_atime = ts[0];
                vattr.va_mtime = ts[1];
                if (nullflag)
                        vattr.va_vaflags |= VA_UTIMES_NULL;
                error = VOP_SETATTR(vp, &vattr, p->p_ucred);
                vput(vp);
        }
        return error;
}

int
kern_utimes(struct nlookupdata *nd, struct timeval *tptr)
{
        struct timespec ts[2];
        struct vnode *vp;
        int error;

        if ((error = getutimes(tptr, ts)) != 0)
                return (error);
        /* XXX Add NLC flag indicating modifying operation? */
        if ((error = nlookup(nd)) != 0)
                return (error);
        if ((error = cache_vref(nd->nl_ncp, nd->nl_cred, &vp)) != 0)
                return (error);
        error = setutimes(vp, ts, tptr == NULL);
        vrele(vp);
        return (error);
}

/*
 * utimes_args(char *path, struct timeval *tptr)
 *
 * Set the access and modification times of a file.
 */
int
utimes(struct utimes_args *uap)
{
        struct timeval tv[2];
        struct nlookupdata nd;
        int error;

        if (uap->tptr) {
                error = copyin(uap->tptr, tv, sizeof(tv));
                if (error)
                        return (error);
        }
        error = nlookup_init(&nd, uap->path, UIO_USERSPACE, NLC_FOLLOW);
        if (error == 0)
                error = kern_utimes(&nd, uap->tptr ? tv : NULL);
        nlookup_done(&nd);
        return (error);
}

/*
 * lutimes_args(char *path, struct timeval *tptr)
 *
 * Set the access and modification times of a file.
 */
int
lutimes(struct lutimes_args *uap)
{
        struct timeval tv[2];
        struct nlookupdata nd;
        int error;

        if (uap->tptr) {
                error = copyin(uap->tptr, tv, sizeof(tv));
                if (error)
                        return (error);
        }
        error = nlookup_init(&nd, uap->path, UIO_USERSPACE, 0);
        if (error == 0)
                error = kern_utimes(&nd, uap->tptr ? tv : NULL);
        nlookup_done(&nd);
        return (error);
}

int
kern_futimes(int fd, struct timeval *tptr)
{
        struct thread *td = curthread;
        struct proc *p = td->td_proc;
        struct timespec ts[2];
        struct file *fp;
        int error;

        error = getutimes(tptr, ts);
        if (error)
                return (error);
        error = getvnode(p->p_fd, fd, &fp);
        if (error)
                return (error);
        error =  setutimes((struct vnode *)fp->f_data, ts, tptr == NULL);
        return (error);
}

/*
 * futimes_args(int fd, struct timeval *tptr)
 *
 * Set the access and modification times of a file.
 */
int
futimes(struct futimes_args *uap)
{
        struct timeval tv[2];
        int error;

        if (uap->tptr) {
                error = copyin(uap->tptr, tv, sizeof(tv));
                if (error)
                        return (error);
        }

        error = kern_futimes(uap->fd, uap->tptr ? tv : NULL);

        return (error);
}

int
kern_truncate(struct nlookupdata *nd, off_t length)
{
        struct vnode *vp;
        struct vattr vattr;
        int error;

        if (length < 0)
                return(EINVAL);
        /* XXX Add NLC flag indicating modifying operation? */
        if ((error = nlookup(nd)) != 0)
                return (error);
        if ((error = cache_vref(nd->nl_ncp, nd->nl_cred, &vp)) != 0)
                return (error);
        if ((error = vn_lock(vp, LK_EXCLUSIVE | LK_RETRY)) != 0) {
                vrele(vp);
                return (error);
        }
        if (vp->v_type == VDIR) {
                error = EISDIR;
        } else if ((error = vn_writechk(vp)) == 0 &&
            (error = VOP_ACCESS(vp, VWRITE, nd->nl_cred)) == 0) {
                VATTR_NULL(&vattr);
                vattr.va_size = length;
                error = VOP_SETATTR(vp, &vattr, nd->nl_cred);
        }
        vput(vp);
        return (error);
}

/*
 * truncate(char *path, int pad, off_t length)
 *
 * Truncate a file given its path name.
 */
int
truncate(struct truncate_args *uap)
{
        struct nlookupdata nd;
        int error;

        error = nlookup_init(&nd, uap->path, UIO_USERSPACE, NLC_FOLLOW);
        if (error == 0)
                error = kern_truncate(&nd, uap->length);
        nlookup_done(&nd);
        return error;
}

int
kern_ftruncate(int fd, off_t length)
{
        struct thread *td = curthread;
        struct proc *p = td->td_proc;
        struct vattr vattr;
        struct vnode *vp;
        struct file *fp;
        int error;

        if (length < 0)
                return(EINVAL);
        if ((error = getvnode(p->p_fd, fd, &fp)) != 0)
                return (error);
        if ((fp->f_flag & FWRITE) == 0)
                return (EINVAL);
        vp = (struct vnode *)fp->f_data;
        vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
        if (vp->v_type == VDIR)
                error = EISDIR;
        else if ((error = vn_writechk(vp)) == 0) {
                VATTR_NULL(&vattr);
                vattr.va_size = length;
                error = VOP_SETATTR(vp, &vattr, fp->f_cred);
        }
        VOP_UNLOCK(vp, 0);
        return (error);
}

/*
 * ftruncate_args(int fd, int pad, off_t length)
 *
 * Truncate a file given a file descriptor.
 */
int
ftruncate(struct ftruncate_args *uap)
{
        int error;

        error = kern_ftruncate(uap->fd, uap->length);

        return (error);
}

/*
 * fsync(int fd)
 *
 * Sync an open file.
 */
/* ARGSUSED */
int
fsync(struct fsync_args *uap)
{
        struct thread *td = curthread;
        struct proc *p = td->td_proc;
        struct vnode *vp;
        struct file *fp;
        vm_object_t obj;
        int error;

        if ((error = getvnode(p->p_fd, uap->fd, &fp)) != 0)
                return (error);
        vp = (struct vnode *)fp->f_data;
        vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
        if ((obj = vp->v_object) != NULL)
                vm_object_page_clean(obj, 0, 0, 0);
        if ((error = VOP_FSYNC(vp, MNT_WAIT)) == 0 &&
            vp->v_mount && (vp->v_mount->mnt_flag & MNT_SOFTDEP) &&
            bioops.io_fsync)
                error = (*bioops.io_fsync)(vp);
        VOP_UNLOCK(vp, 0);
        return (error);
}

int
kern_rename(struct nlookupdata *fromnd, struct nlookupdata *tond)
{
        struct namecache *fncpd;
        struct namecache *tncpd;
        struct namecache *ncp;
        struct mount *mp;
        int error;

        bwillwrite();
        if ((error = nlookup(fromnd)) != 0)
                return (error);
        if ((fncpd = fromnd->nl_ncp->nc_parent) == NULL)
                return (ENOENT);
        cache_hold(fncpd);

        /*
         * unlock the source ncp so we can lookup the target ncp without
         * deadlocking.  The target may or may not exist so we do not check
         * for a target vp like kern_mkdir() and other creation functions do.
         *
         * The source and target directories are ref'd and rechecked after
         * everything is relocked to determine if the source or target file
         * has been renamed.
         */
        KKASSERT(fromnd->nl_flags & NLC_NCPISLOCKED);
        fromnd->nl_flags &= ~NLC_NCPISLOCKED;
        cache_unlock(fromnd->nl_ncp);

        tond->nl_flags |= NLC_CREATE;
        if ((error = nlookup(tond)) != 0) {
                cache_drop(fncpd);
                return (error);
        }
        if ((tncpd = tond->nl_ncp->nc_parent) == NULL) {
                cache_drop(fncpd);
                return (ENOENT);
        }
        cache_hold(tncpd);

        /*
         * If the source and target are the same there is nothing to do
         */
        if (fromnd->nl_ncp == tond->nl_ncp) {
                cache_drop(fncpd);
                cache_drop(tncpd);
                return (0);
        }

        /*
         * relock the source ncp.  NOTE AFTER RELOCKING: the source ncp
         * may have become invalid while it was unlocked, nc_vp and nc_mount
         * could be NULL.
         */
        if (cache_lock_nonblock(fromnd->nl_ncp) == 0) {
                cache_resolve(fromnd->nl_ncp, fromnd->nl_cred);
        } else if (fromnd->nl_ncp > tond->nl_ncp) {
                cache_lock(fromnd->nl_ncp);
                cache_resolve(fromnd->nl_ncp, fromnd->nl_cred);
        } else {
                cache_unlock(tond->nl_ncp);
                cache_lock(fromnd->nl_ncp);
                cache_resolve(fromnd->nl_ncp, fromnd->nl_cred);
                cache_lock(tond->nl_ncp);
                cache_resolve(tond->nl_ncp, tond->nl_cred);
        }
        fromnd->nl_flags |= NLC_NCPISLOCKED;

        /*
         * make sure the parent directories linkages are the same
         */
        if (fncpd != fromnd->nl_ncp->nc_parent ||
            tncpd != tond->nl_ncp->nc_parent) {
                cache_drop(fncpd);
                cache_drop(tncpd);
                return (ENOENT);
        }

        /*
         * Both the source and target must be within the same filesystem and
         * in the same filesystem as their parent directories within the
         * namecache topology.
         *
         * NOTE: fromnd's nc_mount or nc_vp could be NULL.
         */
        mp = fncpd->nc_mount;
        if (mp != tncpd->nc_mount || mp != fromnd->nl_ncp->nc_mount ||
            mp != tond->nl_ncp->nc_mount) {
                cache_drop(fncpd);
                cache_drop(tncpd);
                return (EXDEV);
        }

        /*
         * If the target exists and either the source or target is a directory,
         * then both must be directories.
         *
         * Due to relocking of the source, fromnd->nl_ncp->nc_vp might have
         * become NULL.
         */
        if (tond->nl_ncp->nc_vp) {
                if (fromnd->nl_ncp->nc_vp == NULL) {
                        error = ENOENT;
                } else if (fromnd->nl_ncp->nc_vp->v_type == VDIR) {
                        if (tond->nl_ncp->nc_vp->v_type != VDIR)
                                error = ENOTDIR;
                } else if (tond->nl_ncp->nc_vp->v_type == VDIR) {
                        error = EISDIR;
                }
        }

        /*
         * You cannot rename a source into itself or a subdirectory of itself.
         * We check this by travsersing the target directory upwards looking
         * for a match against the source.
         */
        if (error == 0) {
                for (ncp = tncpd; ncp; ncp = ncp->nc_parent) {
                        if (fromnd->nl_ncp == ncp) {
                                error = EINVAL;
                                break;
                        }
                }
        }

        cache_drop(fncpd);
        cache_drop(tncpd);

        /*
         * Even though the namespaces are different, they may still represent
         * hardlinks to the same file.  The filesystem might have a hard time
         * with this so we issue a NREMOVE of the source instead of a NRENAME
         * when we detect the situation.
         */
        if (error == 0) {
                if (fromnd->nl_ncp->nc_vp == tond->nl_ncp->nc_vp) {
                        error = VOP_NREMOVE(fromnd->nl_ncp, fromnd->nl_cred);
                } else {
                        error = VOP_NRENAME(fromnd->nl_ncp, tond->nl_ncp, 
                                            tond->nl_cred);
                }
        }
        return (error);
}

/*
 * rename_args(char *from, char *to)
 *
 * Rename files.  Source and destination must either both be directories,
 * or both not be directories.  If target is a directory, it must be empty.
 */
int
rename(struct rename_args *uap)
{
        struct nlookupdata fromnd, tond;
        int error;

        error = nlookup_init(&fromnd, uap->from, UIO_USERSPACE, 0);
        if (error == 0) {
                error = nlookup_init(&tond, uap->to, UIO_USERSPACE, 0);
                if (error == 0)
                        error = kern_rename(&fromnd, &tond);
                nlookup_done(&tond);
        }
        nlookup_done(&fromnd);
        return (error);
}

int
kern_mkdir(struct nlookupdata *nd, int mode)
{
        struct thread *td = curthread;
        struct proc *p = td->td_proc;
        struct namecache *ncp;
        struct vnode *vp;
        struct vattr vattr;
        int error;

        bwillwrite();
        nd->nl_flags |= NLC_WILLBEDIR | NLC_CREATE;
        if ((error = nlookup(nd)) != 0)
                return (error);

        ncp = nd->nl_ncp;
        if (ncp->nc_vp)
                return (EEXIST);

        VATTR_NULL(&vattr);
        vattr.va_type = VDIR;
        vattr.va_mode = (mode & ACCESSPERMS) &~ p->p_fd->fd_cmask;

        vp = NULL;
        error = VOP_NMKDIR(ncp, &vp, p->p_ucred, &vattr);
        if (error == 0)
                vput(vp);
        return (error);
}

/*
 * mkdir_args(char *path, int mode)
 *
 * Make a directory file.
 */
/* ARGSUSED */
int
mkdir(struct mkdir_args *uap)
{
        struct nlookupdata nd;
        int error;

        error = nlookup_init(&nd, uap->path, UIO_USERSPACE, 0);
        if (error == 0)
                error = kern_mkdir(&nd, uap->mode);
        nlookup_done(&nd);
        return (error);
}

int
kern_rmdir(struct nlookupdata *nd)
{
        struct namecache *ncp;
        int error;

        bwillwrite();
        nd->nl_flags |= NLC_DELETE;
        if ((error = nlookup(nd)) != 0)
                return (error);

        ncp = nd->nl_ncp;
        error = VOP_NRMDIR(ncp, nd->nl_cred);
        return (error);
}

/*
 * rmdir_args(char *path)
 *
 * Remove a directory file.
 */
/* ARGSUSED */
int
rmdir(struct rmdir_args *uap)
{
        struct nlookupdata nd;
        int error;

        error = nlookup_init(&nd, uap->path, UIO_USERSPACE, 0);
        if (error == 0)
                error = kern_rmdir(&nd);
        nlookup_done(&nd);
        return (error);
}

int
kern_getdirentries(int fd, char *buf, u_int count, long *basep, int *res,
    enum uio_seg direction)
{
        struct thread *td = curthread;
        struct proc *p = td->td_proc;
        struct vnode *vp;
        struct file *fp;
        struct uio auio;
        struct iovec aiov;
        long loff;
        int error, eofflag;

        if ((error = getvnode(p->p_fd, fd, &fp)) != 0)
                return (error);
        if ((fp->f_flag & FREAD) == 0)
                return (EBADF);
        vp = (struct vnode *)fp->f_data;
unionread:
        if (vp->v_type != VDIR)
                return (EINVAL);
        aiov.iov_base = buf;
        aiov.iov_len = count;
        auio.uio_iov = &aiov;
        auio.uio_iovcnt = 1;
        auio.uio_rw = UIO_READ;
        auio.uio_segflg = direction;
        auio.uio_td = td;
        auio.uio_resid = count;
        /* vn_lock(vp, LK_SHARED | LK_RETRY); */
        vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
        loff = auio.uio_offset = fp->f_offset;
        error = VOP_READDIR(vp, &auio, fp->f_cred, &eofflag, NULL, NULL);
        fp->f_offset = auio.uio_offset;
        VOP_UNLOCK(vp, 0);
        if (error)
                return (error);
        if (count == auio.uio_resid) {
                if (union_dircheckp) {
                        error = union_dircheckp(td, &vp, fp);
                        if (error == -1)
                                goto unionread;
                        if (error)
                                return (error);
                }
                if ((vp->v_flag & VROOT) &&
                    (vp->v_mount->mnt_flag & MNT_UNION)) {
                        struct vnode *tvp = vp;
                        vp = vp->v_mount->mnt_vnodecovered;
                        vref(vp);
                        fp->f_data = vp;
                        fp->f_offset = 0;
                        vrele(tvp);
                        goto unionread;
                }
        }
        if (basep) {
                *basep = loff;
        }
        *res = count - auio.uio_resid;
        return (error);
}

/*
 * getdirentries_args(int fd, char *buf, u_int conut, long *basep)
 *
 * Read a block of directory entries in a file system independent format.
 */
int
getdirentries(struct getdirentries_args *uap)
{
        long base;
        int error;

        error = kern_getdirentries(uap->fd, uap->buf, uap->count, &base,
            &uap->sysmsg_result, UIO_USERSPACE);

        if (error == 0)
                error = copyout(&base, uap->basep, sizeof(*uap->basep));
        return (error);
}

/*
 * getdents_args(int fd, char *buf, size_t count)
 */
int
getdents(struct getdents_args *uap)
{
        int error;

        error = kern_getdirentries(uap->fd, uap->buf, uap->count, NULL,
            &uap->sysmsg_result, UIO_USERSPACE);

        return (error);
}

/*
 * umask(int newmask)
 *
 * Set the mode mask for creation of filesystem nodes.
 *
 * MP SAFE
 */
int
umask(struct umask_args *uap)
{
        struct thread *td = curthread;
        struct proc *p = td->td_proc;
        struct filedesc *fdp;

        fdp = p->p_fd;
        uap->sysmsg_result = fdp->fd_cmask;
        fdp->fd_cmask = uap->newmask & ALLPERMS;
        return (0);
}

/*
 * revoke(char *path)
 *
 * Void all references to file by ripping underlying filesystem
 * away from vnode.
 */
/* ARGSUSED */
int
revoke(struct revoke_args *uap)
{
        struct nlookupdata nd;
        struct vattr vattr;
        struct vnode *vp;
        struct ucred *cred;
        int error;

        vp = NULL;
        error = nlookup_init(&nd, uap->path, UIO_USERSPACE, NLC_FOLLOW);
        if (error == 0)
                error = nlookup(&nd);
        if (error == 0)
                error = cache_vref(nd.nl_ncp, nd.nl_cred, &vp);
        cred = crhold(nd.nl_cred);
        nlookup_done(&nd);
        if (error == 0) {
                if (vp->v_type != VCHR && vp->v_type != VBLK)
                        error = EINVAL;
                if (error == 0)
                        error = VOP_GETATTR(vp, &vattr);
                if (error == 0 && cred->cr_uid != vattr.va_uid)
                        error = suser_cred(cred, PRISON_ROOT);
                if (error == 0 && count_udev(vp->v_udev) > 0) {
                        if ((error = vx_lock(vp)) == 0) {
                                VOP_REVOKE(vp, REVOKEALL);
                                vx_unlock(vp);
                        }
                }
                vrele(vp);
        }
        if (cred)
                crfree(cred);
        return (error);
}

/*
 * Convert a user file descriptor to a kernel file entry.
 */
int
getvnode(struct filedesc *fdp, int fd, struct file **fpp)
{
        struct file *fp;

        if ((u_int)fd >= fdp->fd_nfiles ||
            (fp = fdp->fd_files[fd].fp) == NULL)
                return (EBADF);
        if (fp->f_type != DTYPE_VNODE && fp->f_type != DTYPE_FIFO)
                return (EINVAL);
        *fpp = fp;
        return (0);
}
/*
 * getfh_args(char *fname, fhandle_t *fhp)
 *
 * Get (NFS) file handle
 */
int
getfh(struct getfh_args *uap)
{
        struct thread *td = curthread;
        struct nlookupdata nd;
        fhandle_t fh;
        struct vnode *vp;
        int error;

        /*
         * Must be super user
         */
        if ((error = suser(td)) != 0)
                return (error);

        vp = NULL;
        error = nlookup_init(&nd, uap->fname, UIO_USERSPACE, NLC_FOLLOW);
        if (error == 0)
                error = nlookup(&nd);
        if (error == 0)
                error = cache_vget(nd.nl_ncp, nd.nl_cred, LK_EXCLUSIVE, &vp);
        nlookup_done(&nd);
        if (error == 0) {
                bzero(&fh, sizeof(fh));
                fh.fh_fsid = vp->v_mount->mnt_stat.f_fsid;
                error = VFS_VPTOFH(vp, &fh.fh_fid);
                vput(vp);
                if (error == 0)
                        error = copyout(&fh, uap->fhp, sizeof(fh));
        }
        return (error);
}

/*
 * fhopen_args(const struct fhandle *u_fhp, int flags)
 *
 * syscall for the rpc.lockd to use to translate a NFS file handle into
 * an open descriptor.
 *
 * warning: do not remove the suser() call or this becomes one giant
 * security hole.
 */
int
fhopen(struct fhopen_args *uap)
{
        struct thread *td = curthread;
        struct proc *p = td->td_proc;
        struct mount *mp;
        struct vnode *vp;
        struct fhandle fhp;
        struct vattr vat;
        struct vattr *vap = &vat;
        struct flock lf;
        struct filedesc *fdp = p->p_fd;
        int fmode, mode, error, type;
        struct file *nfp; 
        struct file *fp;
        int indx;

        /*
         * Must be super user
         */
        error = suser(td);
        if (error)
                return (error);

        fmode = FFLAGS(uap->flags);
        /* why not allow a non-read/write open for our lockd? */
        if (((fmode & (FREAD | FWRITE)) == 0) || (fmode & O_CREAT))
                return (EINVAL);
        error = copyin(uap->u_fhp, &fhp, sizeof(fhp));
        if (error)
                return(error);
        /* find the mount point */
        mp = vfs_getvfs(&fhp.fh_fsid);
        if (mp == NULL)
                return (ESTALE);
        /* now give me my vnode, it gets returned to me locked */
        error = VFS_FHTOVP(mp, &fhp.fh_fid, &vp);
        if (error)
                return (error);
        /*
         * from now on we have to make sure not
         * to forget about the vnode
         * any error that causes an abort must vput(vp) 
         * just set error = err and 'goto bad;'.
         */

        /* 
         * from vn_open 
         */
        if (vp->v_type == VLNK) {
                error = EMLINK;
                goto bad;
        }
        if (vp->v_type == VSOCK) {
                error = EOPNOTSUPP;
                goto bad;
        }
        mode = 0;
        if (fmode & (FWRITE | O_TRUNC)) {
                if (vp->v_type == VDIR) {
                        error = EISDIR;
                        goto bad;
                }
                error = vn_writechk(vp);
                if (error)
                        goto bad;
                mode |= VWRITE;
        }
        if (fmode & FREAD)
                mode |= VREAD;
        if (mode) {
                error = VOP_ACCESS(vp, mode, p->p_ucred);
                if (error)
                        goto bad;
        }
        if (fmode & O_TRUNC) {
                VOP_UNLOCK(vp, 0);                      /* XXX */
                vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);   /* XXX */
                VATTR_NULL(vap);
                vap->va_size = 0;
                error = VOP_SETATTR(vp, vap, p->p_ucred);
                if (error)
                        goto bad;
        }

        /*
         * VOP_OPEN needs the file pointer so it can potentially override
         * it.
         *
         * WARNING! no f_ncp will be associated when fhopen()ing a directory.
         * XXX
         */
        if ((error = falloc(p, &nfp, NULL)) != 0)
                goto bad;
        fp = nfp;

        error = VOP_OPEN(vp, fmode, p->p_ucred, fp);
        if (error) {
                /*
                 * setting f_ops this way prevents VOP_CLOSE from being
                 * called or fdrop() releasing the vp from v_data.   Since
                 * the VOP_OPEN failed we don't want to VOP_CLOSE.
                 */
                fp->f_ops = &badfileops;
                fp->f_data = NULL;
                fdrop(fp);
                goto bad;
        }

        /*
         * The fp is given its own reference, we still have our ref and lock.
         *
         * Assert that all regular files must be created with a VM object.
         */
        if (vp->v_type == VREG && vp->v_object == NULL) {
                printf("fhopen: regular file did not have VM object: %p\n", vp);
                fdrop(fp);
                goto bad;
        }

        /*
         * The open was successful, associate it with a file descriptor.
         */
        if ((error = fsetfd(p, fp, &indx)) != 0) {
                fdrop(fp);
                goto bad;
        }

        if (fmode & (O_EXLOCK | O_SHLOCK)) {
                lf.l_whence = SEEK_SET;
                lf.l_start = 0;
                lf.l_len = 0;
                if (fmode & O_EXLOCK)
                        lf.l_type = F_WRLCK;
                else
                        lf.l_type = F_RDLCK;
                type = F_FLOCK;
                if ((fmode & FNONBLOCK) == 0)
                        type |= F_WAIT;
                VOP_UNLOCK(vp, 0);
                if ((error = VOP_ADVLOCK(vp, (caddr_t)fp, F_SETLK, &lf, type)) != 0) {
                        /*
                         * lock request failed.  Normally close the descriptor
                         * but handle the case where someone might have dup()d
                         * or close()d it when we weren't looking.
                         */
                        if (fdp->fd_files[indx].fp == fp) {
                                funsetfd(fdp, indx);
                                fdrop(fp);
                        }

                        /*
                         * release our private reference.
                         */
                        fdrop(fp);
                        vrele(vp);
                        return (error);
                }
                vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
                fp->f_flag |= FHASLOCK;
        }

        vput(vp);
        fdrop(fp);
        uap->sysmsg_result = indx;
        return (0);

bad:
        vput(vp);
        return (error);
}

/*
 * fhstat_args(struct fhandle *u_fhp, struct stat *sb)
 */
int
fhstat(struct fhstat_args *uap)
{
        struct thread *td = curthread;
        struct stat sb;
        fhandle_t fh;
        struct mount *mp;
        struct vnode *vp;
        int error;

        /*
         * Must be super user
         */
        error = suser(td);
        if (error)
                return (error);
        
        error = copyin(uap->u_fhp, &fh, sizeof(fhandle_t));
        if (error)
                return (error);

        if ((mp = vfs_getvfs(&fh.fh_fsid)) == NULL)
                return (ESTALE);
        if ((error = VFS_FHTOVP(mp, &fh.fh_fid, &vp)))
                return (error);
        error = vn_stat(vp, &sb, td->td_proc->p_ucred);
        vput(vp);
        if (error)
                return (error);
        error = copyout(&sb, uap->sb, sizeof(sb));
        return (error);
}

/*
 * fhstatfs_args(struct fhandle *u_fhp, struct statfs *buf)
 */
int
fhstatfs(struct fhstatfs_args *uap)
{
        struct thread *td = curthread;
        struct proc *p = td->td_proc;
        struct statfs *sp;
        struct mount *mp;
        struct vnode *vp;
        struct statfs sb;
        char *fullpath, *freepath;
        fhandle_t fh;
        int error;

        /*
         * Must be super user
         */
        if ((error = suser(td)))
                return (error);

        if ((error = copyin(uap->u_fhp, &fh, sizeof(fhandle_t))) != 0)
                return (error);

        if ((mp = vfs_getvfs(&fh.fh_fsid)) == NULL)
                return (ESTALE);

        if (p != NULL && (p->p_fd->fd_nrdir->nc_flag & NCF_ROOT) == 0 &&
            !chroot_visible_mnt(mp, p))
                return (ESTALE);

        if ((error = VFS_FHTOVP(mp, &fh.fh_fid, &vp)))
                return (error);
        mp = vp->v_mount;
        sp = &mp->mnt_stat;
        vput(vp);
        if ((error = VFS_STATFS(mp, sp, p->p_ucred)) != 0)
                return (error);

        error = cache_fullpath(p, mp->mnt_ncp, &fullpath, &freepath);
        if (error)
                return(error);
        bzero(sp->f_mntonname, sizeof(sp->f_mntonname));
        strlcpy(sp->f_mntonname, fullpath, sizeof(sp->f_mntonname));
        free(freepath, M_TEMP);

        sp->f_flags = mp->mnt_flag & MNT_VISFLAGMASK;
        if (suser(td)) {
                bcopy(sp, &sb, sizeof(sb));
                sb.f_fsid.val[0] = sb.f_fsid.val[1] = 0;
                sp = &sb;
        }
        return (copyout(sp, uap->buf, sizeof(*sp)));
}

/*
 * Syscall to push extended attribute configuration information into the
 * VFS.  Accepts a path, which it converts to a mountpoint, as well as
 * a command (int cmd), and attribute name and misc data.  For now, the
 * attribute name is left in userspace for consumption by the VFS_op.
 * It will probably be changed to be copied into sysspace by the
 * syscall in the future, once issues with various consumers of the
 * attribute code have raised their hands.
 *
 * Currently this is used only by UFS Extended Attributes.
 */
int
extattrctl(struct extattrctl_args *uap)
{
        struct nlookupdata nd;
        struct mount *mp;
        struct vnode *vp;
        int error;

        vp = NULL;
        error = nlookup_init(&nd, uap->path, UIO_USERSPACE, NLC_FOLLOW);
        if (error == 0)
                error = nlookup(&nd);
        if (error == 0) {
                mp = nd.nl_ncp->nc_mount;
                error = VFS_EXTATTRCTL(mp, uap->cmd, 
                                uap->attrname, uap->arg, 
                                nd.nl_cred);
        }
        nlookup_done(&nd);
        return (error);
}

/*
 * Syscall to set a named extended attribute on a file or directory.
 * Accepts attribute name, and a uio structure pointing to the data to set.
 * The uio is consumed in the style of writev().  The real work happens
 * in VOP_SETEXTATTR().
 */
int
extattr_set_file(struct extattr_set_file_args *uap)
{
        char attrname[EXTATTR_MAXNAMELEN];
        struct iovec aiov[UIO_SMALLIOV];
        struct iovec *needfree;
        struct nlookupdata nd;
        struct iovec *iov;
        struct vnode *vp;
        struct uio auio;
        u_int iovlen;
        u_int cnt;
        int error;
        int i;

        error = copyin(uap->attrname, attrname, EXTATTR_MAXNAMELEN);
        if (error)
                return (error);

        vp = NULL;
        error = nlookup_init(&nd, uap->path, UIO_USERSPACE, NLC_FOLLOW);
        if (error == 0)
                error = nlookup(&nd);
        if (error == 0)
                error = cache_vget(nd.nl_ncp, nd.nl_cred, LK_EXCLUSIVE, &vp);
        if (error) {
                nlookup_done(&nd);
                return (error);
        }

        needfree = NULL;
        iovlen = uap->iovcnt * sizeof(struct iovec);
        if (uap->iovcnt > UIO_SMALLIOV) {
                if (uap->iovcnt > UIO_MAXIOV) {
                        error = EINVAL;
                        goto done;
                }
                MALLOC(iov, struct iovec *, iovlen, M_IOV, M_WAITOK);
                needfree = iov;
        } else {
                iov = aiov;
        }
        auio.uio_iov = iov;
        auio.uio_iovcnt = uap->iovcnt;
        auio.uio_rw = UIO_WRITE;
        auio.uio_segflg = UIO_USERSPACE;
        auio.uio_td = nd.nl_td;
        auio.uio_offset = 0;
        if ((error = copyin(uap->iovp, iov, iovlen)))
                goto done;
        auio.uio_resid = 0;
        for (i = 0; i < uap->iovcnt; i++) {
                if (iov->iov_len > INT_MAX - auio.uio_resid) {
                        error = EINVAL;
                        goto done;
                }
                auio.uio_resid += iov->iov_len;
                iov++;
        }
        cnt = auio.uio_resid;
        error = VOP_SETEXTATTR(vp, attrname, &auio, nd.nl_cred);
        cnt -= auio.uio_resid;
        uap->sysmsg_result = cnt;
done:
        vput(vp);
        nlookup_done(&nd);
        if (needfree)
                FREE(needfree, M_IOV);
        return (error);
}

/*
 * Syscall to get a named extended attribute on a file or directory.
 * Accepts attribute name, and a uio structure pointing to a buffer for the
 * data.  The uio is consumed in the style of readv().  The real work
 * happens in VOP_GETEXTATTR();
 */
int
extattr_get_file(struct extattr_get_file_args *uap)
{
        char attrname[EXTATTR_MAXNAMELEN];
        struct iovec aiov[UIO_SMALLIOV];
        struct iovec *needfree;
        struct nlookupdata nd;
        struct iovec *iov;
        struct vnode *vp;
        struct uio auio;
        u_int iovlen;
        u_int cnt;
        int error;
        int i;

        error = copyin(uap->attrname, attrname, EXTATTR_MAXNAMELEN);
        if (error)
                return (error);

        vp = NULL;
        error = nlookup_init(&nd, uap->path, UIO_USERSPACE, NLC_FOLLOW);
        if (error == 0)
                error = nlookup(&nd);
        if (error == 0)
                error = cache_vget(nd.nl_ncp, nd.nl_cred, LK_EXCLUSIVE, &vp);
        if (error) {
                nlookup_done(&nd);
                return (error);
        }

        iovlen = uap->iovcnt * sizeof (struct iovec);
        needfree = NULL;
        if (uap->iovcnt > UIO_SMALLIOV) {
                if (uap->iovcnt > UIO_MAXIOV) {
                        error = EINVAL;
                        goto done;
                }
                MALLOC(iov, struct iovec *, iovlen, M_IOV, M_WAITOK);
                needfree = iov;
        } else {
                iov = aiov;
        }
        auio.uio_iov = iov;
        auio.uio_iovcnt = uap->iovcnt;
        auio.uio_rw = UIO_READ;
        auio.uio_segflg = UIO_USERSPACE;
        auio.uio_td = nd.nl_td;
        auio.uio_offset = 0;
        if ((error = copyin(uap->iovp, iov, iovlen)))
                goto done;
        auio.uio_resid = 0;
        for (i = 0; i < uap->iovcnt; i++) {
                if (iov->iov_len > INT_MAX - auio.uio_resid) {
                        error = EINVAL;
                        goto done;
                }
                auio.uio_resid += iov->iov_len;
                iov++;
        }
        cnt = auio.uio_resid;
        error = VOP_GETEXTATTR(vp, attrname, &auio, nd.nl_cred);
        cnt -= auio.uio_resid;
        uap->sysmsg_result = cnt;
done:
        vput(vp);
        nlookup_done(&nd);
        if (needfree)
                FREE(needfree, M_IOV);
        return(error);
}

/*
 * Syscall to delete a named extended attribute from a file or directory.
 * Accepts attribute name.  The real work happens in VOP_SETEXTATTR().
 */
int
extattr_delete_file(struct extattr_delete_file_args *uap)
{
        char attrname[EXTATTR_MAXNAMELEN];
        struct nlookupdata nd;
        struct vnode *vp;
        int error;

        error = copyin(uap->attrname, attrname, EXTATTR_MAXNAMELEN);
        if (error)
                return(error);

        vp = NULL;
        error = nlookup_init(&nd, uap->path, UIO_USERSPACE, NLC_FOLLOW);
        if (error == 0)
                error = nlookup(&nd);
        if (error == 0)
                error = cache_vget(nd.nl_ncp, nd.nl_cred, LK_EXCLUSIVE, &vp);
        if (error) {
                nlookup_done(&nd);
                return (error);
        }

        error = VOP_SETEXTATTR(vp, attrname, NULL, nd.nl_cred);
        vput(vp);
        nlookup_done(&nd);
        return(error);
}

static int
chroot_visible_mnt(struct mount *mp, struct proc *p)
{
        struct namecache *ncp;
        /*
         * First check if this file system is below
         * the chroot path.
         */
        ncp = mp->mnt_ncp;
        while (ncp != NULL && ncp != p->p_fd->fd_nrdir)
                ncp = ncp->nc_parent;
        if (ncp == NULL) {
                /*
                 * This is not below the chroot path.
                 *
                 * Check if the chroot path is on the same filesystem,
                 * by determing if we have to cross a mount point
                 * before reaching mp->mnt_ncp.
                 */
                ncp = p->p_fd->fd_nrdir;
                while (ncp != NULL && ncp != mp->mnt_ncp) {
                        if (ncp->nc_flag & NCF_MOUNTPT) {
                                ncp = NULL;
                                break;
                        }
                        ncp = ncp->nc_parent;
                }
        }
        return(ncp != NULL);
}