xnu-792.2.4.tar.gz

[apple/xnu.git] / bsd / vfs / vfs_lookup.c

/*
 * Copyright (c) 2000-2004 Apple Computer, Inc. All rights reserved.
 *
 * @APPLE_LICENSE_HEADER_START@
 * 
 * The contents of this file constitute Original Code as defined in and
 * are subject to the Apple Public Source License Version 1.1 (the
 * "License").  You may not use this file except in compliance with the
 * License.  Please obtain a copy of the License at
 * http://www.apple.com/publicsource and read it before using this file.
 * 
 * This Original Code and all software distributed under the License are
 * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT.  Please see the
 * License for the specific language governing rights and limitations
 * under the License.
 * 
 * @APPLE_LICENSE_HEADER_END@
 */
/* Copyright (c) 1995 NeXT Computer, Inc. All Rights Reserved */
/*
 * Copyright (c) 1982, 1986, 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_lookup.c        8.10 (Berkeley) 5/27/95
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/syslimits.h>
#include <sys/time.h>
#include <sys/namei.h>
#include <sys/vm.h>
#include <sys/vnode_internal.h>
#include <sys/mount_internal.h>
#include <sys/errno.h>
#include <sys/malloc.h>
#include <sys/filedesc.h>
#include <sys/proc_internal.h>
#include <sys/kdebug.h>
#include <sys/unistd.h>         /* For _PC_NAME_MAX */
#include <sys/uio_internal.h>
#include <sys/kauth.h>

#include <bsm/audit_kernel.h>

#if KTRACE
#include <sys/ktrace.h>
#endif


static  void kdebug_lookup(struct vnode *dp, struct componentname *cnp);

/*
 * Convert a pathname into a pointer to a locked inode.
 *
 * The FOLLOW flag is set when symbolic links are to be followed
 * when they occur at the end of the name translation process.
 * Symbolic links are always followed for all other pathname
 * components other than the last.
 *
 * The segflg defines whether the name is to be copied from user
 * space or kernel space.
 *
 * Overall outline of namei:
 *
 *      copy in name
 *      get starting directory
 *      while (!done && !error) {
 *              call lookup to search path.
 *              if symbolic link, massage name in buffer and continue
 *      }
 */

int
namei(ndp)
        register struct nameidata *ndp;
{
        register struct filedesc *fdp;  /* pointer to file descriptor state */
        register char *cp;              /* pointer into pathname argument */
        register struct vnode *dp;      /* the directory we are searching */
        uio_t auio;
        int error;
        struct componentname *cnp = &ndp->ni_cnd;
        vfs_context_t ctx = cnp->cn_context;
        struct proc *p = vfs_context_proc(ctx);
        char *tmppn;
        char uio_buf[ UIO_SIZEOF(1) ];

#if DIAGNOSTIC
        if (!vfs_context_ucred(ctx) || !p)
                panic ("namei: bad cred/proc");
        if (cnp->cn_nameiop & (~OPMASK))
                panic ("namei: nameiop contaminated with flags");
        if (cnp->cn_flags & OPMASK)
                panic ("namei: flags contaminated with nameiops");
#endif
        fdp = p->p_fd;

        /*
         * Get a buffer for the name to be translated, and copy the
         * name into the buffer.
         */
        if ((cnp->cn_flags & HASBUF) == 0) {
                cnp->cn_pnbuf = &ndp->ni_pathbuf;
                cnp->cn_pnlen = PATHBUFLEN;
        }
#if LP64_DEBUG
        if (IS_VALID_UIO_SEGFLG(ndp->ni_segflg) == 0) {
                panic("%s :%d - invalid ni_segflg\n", __FILE__, __LINE__); 
        }
#endif /* LP64_DEBUG */

retry_copy:
        if (UIO_SEG_IS_USER_SPACE(ndp->ni_segflg))
                error = copyinstr(ndp->ni_dirp, cnp->cn_pnbuf,
                            cnp->cn_pnlen, (size_t *)&ndp->ni_pathlen);
        else
                error = copystr(CAST_DOWN(void *, ndp->ni_dirp), cnp->cn_pnbuf,
                            cnp->cn_pnlen, (size_t *)&ndp->ni_pathlen);

        if (error == ENAMETOOLONG && !(cnp->cn_flags & HASBUF)) {
                MALLOC_ZONE(cnp->cn_pnbuf, caddr_t,
                            MAXPATHLEN, M_NAMEI, M_WAITOK);

                cnp->cn_flags |= HASBUF;
                cnp->cn_pnlen = MAXPATHLEN;
                
                goto retry_copy;
        }
        if (error)
                goto error_out;

        /* If we are auditing the kernel pathname, save the user pathname */
        if (cnp->cn_flags & AUDITVNPATH1)
                AUDIT_ARG(upath, p, cnp->cn_pnbuf, ARG_UPATH1); 
        if (cnp->cn_flags & AUDITVNPATH2)
                AUDIT_ARG(upath, p, cnp->cn_pnbuf, ARG_UPATH2); 

        /*
         * Do not allow empty pathnames
         */
        if (*cnp->cn_pnbuf == '\0') {
                error = ENOENT;
                goto error_out;
        }
        ndp->ni_loopcnt = 0;
#if KTRACE
        if (KTRPOINT(p, KTR_NAMEI))
                ktrnamei(p->p_tracep, cnp->cn_pnbuf);
#endif

        /*
         * determine the starting point for the translation.
         */
        if ((ndp->ni_rootdir = fdp->fd_rdir) == NULLVP) {
                if ( !(fdp->fd_flags & FD_CHROOT))
                        ndp->ni_rootdir = rootvnode;
        }
        cnp->cn_nameptr = cnp->cn_pnbuf;

        ndp->ni_usedvp = NULLVP;

        if (*(cnp->cn_nameptr) == '/') {
                while (*(cnp->cn_nameptr) == '/') {
                        cnp->cn_nameptr++;
                        ndp->ni_pathlen--;
                }
                dp = ndp->ni_rootdir;
        } else if (cnp->cn_flags & USEDVP) {
                dp = ndp->ni_dvp;
                ndp->ni_usedvp = dp;
        } else
                dp = fdp->fd_cdir;

        if (dp == NULLVP) {
                error = ENOENT;
                goto error_out;
        }
        ndp->ni_dvp = NULLVP;
        ndp->ni_vp  = NULLVP;

        for (;;) {
                int need_newpathbuf;
                int linklen;

                ndp->ni_startdir = dp;

                if ( (error = lookup(ndp)) ) {
                        goto error_out;
                }
                /*
                 * Check for symbolic link
                 */
                if ((cnp->cn_flags & ISSYMLINK) == 0) {
                        return (0);
                }
                if ((cnp->cn_flags & FSNODELOCKHELD)) {
                        cnp->cn_flags &= ~FSNODELOCKHELD;
                        unlock_fsnode(ndp->ni_dvp, NULL);
                }       
                if (ndp->ni_loopcnt++ >= MAXSYMLINKS) {
                        error = ELOOP;
                        break;
                }
                if (ndp->ni_pathlen > 1 || !(cnp->cn_flags & HASBUF))
                        need_newpathbuf = 1;
                else
                        need_newpathbuf = 0;

                if (need_newpathbuf) {
                        MALLOC_ZONE(cp, char *, MAXPATHLEN, M_NAMEI, M_WAITOK);
                } else {
                        cp = cnp->cn_pnbuf;
                }
                auio = uio_createwithbuffer(1, 0, UIO_SYSSPACE, UIO_READ, &uio_buf[0], sizeof(uio_buf));

                uio_addiov(auio, CAST_USER_ADDR_T(cp), MAXPATHLEN);

                error = VNOP_READLINK(ndp->ni_vp, auio, ctx);
                if (error) {
                        if (need_newpathbuf)
                                FREE_ZONE(cp, MAXPATHLEN, M_NAMEI);
                        break;
                }
                // LP64todo - fix this
                linklen = MAXPATHLEN - uio_resid(auio);
                if (linklen + ndp->ni_pathlen > MAXPATHLEN) {
                        if (need_newpathbuf)
                                FREE_ZONE(cp, MAXPATHLEN, M_NAMEI);

                        error = ENAMETOOLONG;
                        break;
                }
                if (need_newpathbuf) {
                        long len = cnp->cn_pnlen;

                        tmppn = cnp->cn_pnbuf;
                        bcopy(ndp->ni_next, cp + linklen, ndp->ni_pathlen);
                        cnp->cn_pnbuf = cp;
                        cnp->cn_pnlen = MAXPATHLEN;

                        if ( (cnp->cn_flags & HASBUF) )
                                FREE_ZONE(tmppn, len, M_NAMEI);
                        else
                                cnp->cn_flags |= HASBUF;
                } else
                        cnp->cn_pnbuf[linklen] = '\0';

                ndp->ni_pathlen += linklen;
                cnp->cn_nameptr = cnp->cn_pnbuf;

                /*
                 * starting point for 'relative'
                 * symbolic link path
                 */
                dp = ndp->ni_dvp;
                /*
                 * get rid of references returned via 'lookup'
                 */
                vnode_put(ndp->ni_vp);
                vnode_put(ndp->ni_dvp);

                ndp->ni_vp = NULLVP;
                ndp->ni_dvp = NULLVP;

                /*
                 * Check if symbolic link restarts us at the root
                 */
                if (*(cnp->cn_nameptr) == '/') {
                        while (*(cnp->cn_nameptr) == '/') {
                                cnp->cn_nameptr++;
                                ndp->ni_pathlen--;
                        }
                        if ((dp = ndp->ni_rootdir) == NULLVP) {
                                error = ENOENT;
                                goto error_out;
                        }
                }
        }
        /*
         * only come here if we fail to handle a SYMLINK...
         * if either ni_dvp or ni_vp is non-NULL, then
         * we need to drop the iocount that was picked
         * up in the lookup routine
         */
        if (ndp->ni_dvp)
                vnode_put(ndp->ni_dvp);
        if (ndp->ni_vp)
                vnode_put(ndp->ni_vp);
 error_out:
        if ( (cnp->cn_flags & HASBUF) ) {
                cnp->cn_flags &= ~HASBUF;
                FREE_ZONE(cnp->cn_pnbuf, cnp->cn_pnlen, M_NAMEI);
        }
        cnp->cn_pnbuf = NULL;
        ndp->ni_vp = NULLVP;

        return (error);
}


/*
 * Search a pathname.
 * This is a very central and rather complicated routine.
 *
 * The pathname is pointed to by ni_ptr and is of length ni_pathlen.
 * The starting directory is taken from ni_startdir. The pathname is
 * descended until done, or a symbolic link is encountered. The variable
 * ni_more is clear if the path is completed; it is set to one if a
 * symbolic link needing interpretation is encountered.
 *
 * The flag argument is LOOKUP, CREATE, RENAME, or DELETE depending on
 * whether the name is to be looked up, created, renamed, or deleted.
 * When CREATE, RENAME, or DELETE is specified, information usable in
 * creating, renaming, or deleting a directory entry may be calculated.
 * If flag has LOCKPARENT or'ed into it, the parent directory is returned
 * locked. If flag has WANTPARENT or'ed into it, the parent directory is
 * returned unlocked. Otherwise the parent directory is not returned. If
 * the target of the pathname exists and LOCKLEAF is or'ed into the flag
 * the target is returned locked, otherwise it is returned unlocked.
 * When creating or renaming and LOCKPARENT is specified, the target may not
 * be ".".  When deleting and LOCKPARENT is specified, the target may be ".".
 * 
 * Overall outline of lookup:
 *
 * dirloop:
 *      identify next component of name at ndp->ni_ptr
 *      handle degenerate case where name is null string
 *      if .. and crossing mount points and on mounted filesys, find parent
 *      call VNOP_LOOKUP routine for next component name
 *          directory vnode returned in ni_dvp, unlocked unless LOCKPARENT set
 *          component vnode returned in ni_vp (if it exists), locked.
 *      if result vnode is mounted on and crossing mount points,
 *          find mounted on vnode
 *      if more components of name, do next level at dirloop
 *      return the answer in ni_vp, locked if LOCKLEAF set
 *          if LOCKPARENT set, return locked parent in ni_dvp
 *          if WANTPARENT set, return unlocked parent in ni_dvp
 */
int
lookup(ndp)
        register struct nameidata *ndp;
{
        register char   *cp;            /* pointer into pathname argument */
        vnode_t         tdp;            /* saved dp */
        vnode_t         dp;             /* the directory we are searching */
        mount_t         mp;             /* mount table entry */
        int docache = 1;                /* == 0 do not cache last component */
        int wantparent;                 /* 1 => wantparent or lockparent flag */
        int rdonly;                     /* lookup read-only flag bit */
        int trailing_slash = 0;
        int dp_authorized = 0;
        int error = 0;
        struct componentname *cnp = &ndp->ni_cnd;
        vfs_context_t ctx = cnp->cn_context;

        /*
         * Setup: break out flag bits into variables.
         */
        if (cnp->cn_flags & (NOCACHE | DOWHITEOUT)) {
                if ((cnp->cn_flags & NOCACHE) || (cnp->cn_nameiop == DELETE))
                        docache = 0;
        }
        wantparent = cnp->cn_flags & (LOCKPARENT | WANTPARENT);
        rdonly = cnp->cn_flags & RDONLY;
        cnp->cn_flags &= ~ISSYMLINK;
        cnp->cn_consume = 0;

        dp = ndp->ni_startdir;
        ndp->ni_startdir = NULLVP;

        cp = cnp->cn_nameptr;

        if (*cp == '\0') {
                if ( (vnode_getwithref(dp)) ) {
                        dp = NULLVP;
                        error = ENOENT;
                        goto bad;
                }
                goto emptyname;
        }
dirloop: 
        ndp->ni_vp = NULLVP;

        if ( (error = cache_lookup_path(ndp, cnp, dp, ctx, &trailing_slash, &dp_authorized)) ) {
                dp = NULLVP;
                goto bad;
        }
        if ((cnp->cn_flags & ISLASTCN)) {
                if (docache)
                        cnp->cn_flags |= MAKEENTRY;
        } else
                cnp->cn_flags |= MAKEENTRY;

        dp = ndp->ni_dvp;

        if (ndp->ni_vp != NULLVP) {
                /*
                 * cache_lookup_path returned a non-NULL ni_vp then,
                 * we're guaranteed that the dp is a VDIR, it's 
                 * been authorized, and vp is not ".."
                 */
                goto returned_from_lookup_path;
        }

        /*
         * Handle "..": two special cases.
         * 1. If at root directory (e.g. after chroot)
         *    or at absolute root directory
         *    then ignore it so can't get out.
         * 2. If this vnode is the root of a mounted
         *    filesystem, then replace it with the
         *    vnode which was mounted on so we take the
         *    .. in the other file system.
         */
        if ( (cnp->cn_flags & ISDOTDOT) ) {
                for (;;) {
                        if (dp == ndp->ni_rootdir || dp == rootvnode) {
                                ndp->ni_dvp = dp;
                                ndp->ni_vp = dp;
                                /*
                                 * we're pinned at the root
                                 * we've already got one reference on 'dp'
                                 * courtesy of cache_lookup_path... take
                                 * another one for the ".."
                                 * if we fail to get the new reference, we'll
                                 * drop our original down in 'bad'
                                 */
                                if ( (vnode_get(dp)) ) {
                                        error = ENOENT;
                                        goto bad;
                                }
                                goto nextname;
                        }
                        if ((dp->v_flag & VROOT) == 0 ||
                            (cnp->cn_flags & NOCROSSMOUNT))
                                break;
                        if (dp->v_mount == NULL) {      /* forced umount */
                                error = EBADF;
                                goto bad;
                        }
                        tdp = dp;
                        dp = tdp->v_mount->mnt_vnodecovered;

                        vnode_put(tdp);

                        if ( (vnode_getwithref(dp)) ) {
                                dp = NULLVP;
                                error = ENOENT;
                                goto bad;
                        }
                        ndp->ni_dvp = dp;
                        dp_authorized = 0;
                }
        }

        /*
         * We now have a segment name to search for, and a directory to search.
         */
unionlookup:
        ndp->ni_vp = NULLVP;

        if (dp->v_type != VDIR) {
                error = ENOTDIR;
                goto lookup_error;
        }
        if ( !(dp_authorized || (cnp->cn_flags & DONOTAUTH)) ) {
                if ( (error = vnode_authorize(dp, NULL, KAUTH_VNODE_SEARCH, ctx)) )
                        goto lookup_error;
        }
        if ( (error = VNOP_LOOKUP(dp, &ndp->ni_vp, cnp, ctx)) ) {
lookup_error:
                if ((error == ENOENT) &&
                    (dp->v_flag & VROOT) && (dp->v_mount != NULL) &&
                    (dp->v_mount->mnt_flag & MNT_UNION)) {
                        if ((cnp->cn_flags & FSNODELOCKHELD)) {
                                cnp->cn_flags &= ~FSNODELOCKHELD;
                                unlock_fsnode(dp, NULL);
                        }       
                        tdp = dp;
                        dp = tdp->v_mount->mnt_vnodecovered;

                        vnode_put(tdp);

                        if ( (vnode_getwithref(dp)) ) {
                                dp = NULLVP;
                                error = ENOENT;
                                goto bad;
                        }
                        ndp->ni_dvp = dp;
                        dp_authorized = 0;
                        goto unionlookup;
                }

                if (error != EJUSTRETURN)
                        goto bad;

                if (ndp->ni_vp != NULLVP)
                        panic("leaf should be empty");

                /*
                 * If creating and at end of pathname, then can consider
                 * allowing file to be created.
                 */
                if (rdonly) {
                        error = EROFS;
                        goto bad;
                }
                if ((cnp->cn_flags & ISLASTCN) && trailing_slash && !(cnp->cn_flags & WILLBEDIR)) {
                        error = ENOENT;
                        goto bad;
                }
                /*
                 * We return with ni_vp NULL to indicate that the entry
                 * doesn't currently exist, leaving a pointer to the
                 * referenced directory vnode in ndp->ni_dvp.
                 */
                if (cnp->cn_flags & SAVESTART) {
                        if ( (vnode_get(ndp->ni_dvp)) ) {
                                error = ENOENT;
                                goto bad;
                        }
                        ndp->ni_startdir = ndp->ni_dvp;
                }
                if (!wantparent)
                        vnode_put(ndp->ni_dvp);

                if (kdebug_enable)
                        kdebug_lookup(ndp->ni_dvp, cnp);
                return (0);
        }
returned_from_lookup_path:
        dp = ndp->ni_vp;

        /*
         * Take into account any additional components consumed by
         * the underlying filesystem.
         */
        if (cnp->cn_consume > 0) {
                cnp->cn_nameptr += cnp->cn_consume;
                ndp->ni_next += cnp->cn_consume;
                ndp->ni_pathlen -= cnp->cn_consume;
                cnp->cn_consume = 0;
        } else {
                if (dp->v_name == NULL || dp->v_parent == NULLVP) {
                        int isdot_or_dotdot;
                        int  update_flags = 0;

                        isdot_or_dotdot = (cnp->cn_namelen == 1 && cnp->cn_nameptr[0] == '.') || (cnp->cn_flags & ISDOTDOT);
            
                        if (isdot_or_dotdot == 0) {
                                if (dp->v_name == NULL)
                                        update_flags |= VNODE_UPDATE_NAME;
                                if (ndp->ni_dvp != NULLVP && dp->v_parent == NULLVP)
                                        update_flags |= VNODE_UPDATE_PARENT;

                                if (update_flags)
                                        vnode_update_identity(dp, ndp->ni_dvp, cnp->cn_nameptr, cnp->cn_namelen, cnp->cn_hash, update_flags);
                        }
                }

                if ( (cnp->cn_flags & MAKEENTRY) && (dp->v_flag & VNCACHEABLE) && LIST_FIRST(&dp->v_nclinks) == NULL) {
                        /*
                         * missing from name cache, but should
                         * be in it... this can happen if volfs
                         * causes the vnode to be created or the
                         * name cache entry got recycled but the
                         * vnode didn't...
                         * check to make sure that ni_dvp is valid
                         * cache_lookup_path may return a NULL
                         */
                        if (ndp->ni_dvp != NULL)
                                cache_enter(ndp->ni_dvp, dp, cnp);
                }
        }

        /*
         * Check to see if the vnode has been mounted on...
         * if so find the root of the mounted file system.
         */
check_mounted_on:
        if ((dp->v_type == VDIR) && dp->v_mountedhere &&
            ((cnp->cn_flags & NOCROSSMOUNT) == 0)) {
          
                vnode_lock(dp);

                if ((dp->v_type == VDIR) && (mp = dp->v_mountedhere)) {

                        mp->mnt_crossref++;
                        vnode_unlock(dp);

                        if (vfs_busy(mp, 0)) {
                                mount_dropcrossref(mp, dp, 0);
                                goto check_mounted_on;
                        }
                        error = VFS_ROOT(mp, &tdp, ctx);
                        /*
                         * mount_dropcrossref does a vnode_put
                         * on dp if the 3rd arg is non-zero
                         */
                        mount_dropcrossref(mp, dp, 1);
                        dp = NULL;
                        vfs_unbusy(mp);

                        if (error) {
                                goto bad2;
                        }
                        ndp->ni_vp = dp = tdp;
                        
                        goto check_mounted_on;
                } 
                vnode_unlock(dp);
        }

        /*
         * Check for symbolic link
         */
        if ((dp->v_type == VLNK) &&
            ((cnp->cn_flags & FOLLOW) || trailing_slash || *ndp->ni_next == '/')) {
                cnp->cn_flags |= ISSYMLINK;
                return (0);
        }

        /*
         * Check for bogus trailing slashes.
         */
        if (trailing_slash) {
                if (dp->v_type != VDIR) {
                        error = ENOTDIR;
                        goto bad2;
                }
                trailing_slash = 0;
        }

nextname:
        /*
         * Not a symbolic link.  If more pathname,
         * continue at next component, else return.
         */
        if (*ndp->ni_next == '/') {
                cnp->cn_nameptr = ndp->ni_next + 1;
                ndp->ni_pathlen--;
                while (*cnp->cn_nameptr == '/') {
                        cnp->cn_nameptr++;
                        ndp->ni_pathlen--;
                }
                vnode_put(ndp->ni_dvp);

                cp = cnp->cn_nameptr;

                if (*cp == '\0')
                        goto emptyname;

                vnode_put(dp);
                goto dirloop;
        }
                                  
        /*
         * Disallow directory write attempts on read-only file systems.
         */
        if (rdonly &&
            (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME)) {
                error = EROFS;
                goto bad2;
        }
        if (cnp->cn_flags & SAVESTART) {
                /*      
                 * note that we already hold a reference
                 * on both dp and ni_dvp, but for some reason
                 * can't get another one... in this case we
                 * need to do vnode_put on dp in 'bad2'
                 */
                if ( (vnode_get(ndp->ni_dvp)) ) {
                        error = ENOENT;
                        goto bad2;
                }
                ndp->ni_startdir = ndp->ni_dvp;
        }
        if (!wantparent && ndp->ni_dvp)
                vnode_put(ndp->ni_dvp);

        if (cnp->cn_flags & AUDITVNPATH1)
                AUDIT_ARG(vnpath, dp, ARG_VNODE1);
        else if (cnp->cn_flags & AUDITVNPATH2)
                AUDIT_ARG(vnpath, dp, ARG_VNODE2);

        if (kdebug_enable)
                kdebug_lookup(dp, cnp);
        return (0);

emptyname:
        cnp->cn_namelen = 0;
        /*
         * A degenerate name (e.g. / or "") which is a way of
         * talking about a directory, e.g. like "/." or ".".
         */
        if (dp->v_type != VDIR) {
                error = ENOTDIR;
                goto bad;
        }
        if (cnp->cn_nameiop != LOOKUP) {
                error = EISDIR;
                goto bad;
        }
        if (wantparent) {
                /*      
                 * note that we already hold a reference
                 * on dp, but for some reason can't
                 * get another one... in this case we
                 * need to do vnode_put on dp in 'bad'
                 */
                if ( (vnode_get(dp)) ) {
                        error = ENOENT;
                        goto bad;
                }
                ndp->ni_dvp = dp;
        }
        cnp->cn_flags &= ~ISDOTDOT;
        cnp->cn_flags |= ISLASTCN;
        ndp->ni_next = cp;
        ndp->ni_vp = dp;

        if (cnp->cn_flags & AUDITVNPATH1)
                AUDIT_ARG(vnpath, dp, ARG_VNODE1);
        else if (cnp->cn_flags & AUDITVNPATH2)
                AUDIT_ARG(vnpath, dp, ARG_VNODE2);
        if (cnp->cn_flags & SAVESTART)
                panic("lookup: SAVESTART");
        return (0);

bad2:
        if ((cnp->cn_flags & FSNODELOCKHELD)) {
                cnp->cn_flags &= ~FSNODELOCKHELD;
                unlock_fsnode(ndp->ni_dvp, NULL);
        }
        if (ndp->ni_dvp)
                vnode_put(ndp->ni_dvp);
        if (dp)
                vnode_put(dp);
        ndp->ni_vp = NULLVP;

        if (kdebug_enable)
                kdebug_lookup(dp, cnp);
        return (error);

bad:
        if ((cnp->cn_flags & FSNODELOCKHELD)) {
                cnp->cn_flags &= ~FSNODELOCKHELD;
                unlock_fsnode(ndp->ni_dvp, NULL);
        }       
        if (dp)
                vnode_put(dp);
        ndp->ni_vp = NULLVP;

        if (kdebug_enable)
                kdebug_lookup(dp, cnp);
        return (error);
}

/*
 * relookup - lookup a path name component
 *    Used by lookup to re-aquire things.
 */
int
relookup(dvp, vpp, cnp)
        struct vnode *dvp, **vpp;
        struct componentname *cnp;
{
        struct vnode *dp = 0;           /* the directory we are searching */
        int wantparent;                 /* 1 => wantparent or lockparent flag */
        int rdonly;                     /* lookup read-only flag bit */
        int error = 0;
#ifdef NAMEI_DIAGNOSTIC
        int i, newhash;                 /* DEBUG: check name hash */
        char *cp;                       /* DEBUG: check name ptr/len */
#endif
        vfs_context_t ctx = cnp->cn_context;;

        /*
         * Setup: break out flag bits into variables.
         */
        wantparent = cnp->cn_flags & (LOCKPARENT|WANTPARENT);
        rdonly = cnp->cn_flags & RDONLY;
        cnp->cn_flags &= ~ISSYMLINK;

        if (cnp->cn_flags & NOCACHE)
                cnp->cn_flags &= ~MAKEENTRY;
        else
                cnp->cn_flags |= MAKEENTRY;

        dp = dvp;

        /*
         * Check for degenerate name (e.g. / or "")
         * which is a way of talking about a directory,
         * e.g. like "/." or ".".
         */
        if (cnp->cn_nameptr[0] == '\0') {
                if (cnp->cn_nameiop != LOOKUP || wantparent) {
                        error = EISDIR;
                        goto bad;
                }
                if (dp->v_type != VDIR) {
                        error = ENOTDIR;
                        goto bad;
                }
                if ( (vnode_get(dp)) ) {
                        error = ENOENT;
                        goto bad;
                }
                *vpp = dp;

                if (cnp->cn_flags & SAVESTART)
                        panic("lookup: SAVESTART");
                return (0);
        }
        /*
         * We now have a segment name to search for, and a directory to search.
         */
        if ( (error = VNOP_LOOKUP(dp, vpp, cnp, ctx)) ) {
                if (error != EJUSTRETURN)
                        goto bad;
#if DIAGNOSTIC
                if (*vpp != NULL)
                        panic("leaf should be empty");
#endif
                /*
                 * If creating and at end of pathname, then can consider
                 * allowing file to be created.
                 */
                if (rdonly) {
                        error = EROFS;
                        goto bad;
                }
                /*
                 * We return with ni_vp NULL to indicate that the entry
                 * doesn't currently exist, leaving a pointer to the
                 * (possibly locked) directory inode in ndp->ni_dvp.
                 */
                return (0);
        }
        dp = *vpp;

#if DIAGNOSTIC
        /*
         * Check for symbolic link
         */
        if (dp->v_type == VLNK && (cnp->cn_flags & FOLLOW))
                panic ("relookup: symlink found.\n");
#endif

        /*
         * Disallow directory write attempts on read-only file systems.
         */
        if (rdonly &&
            (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME)) {
                error = EROFS;
                goto bad2;
        }
        /* ASSERT(dvp == ndp->ni_startdir) */
        
        return (0);

bad2:
        vnode_put(dp);
bad:    
        *vpp = NULL;

        return (error);
}

/*
 * Free pathname buffer
 */
void
nameidone(struct nameidata *ndp)
{
        if ((ndp->ni_cnd.cn_flags & FSNODELOCKHELD)) {
                ndp->ni_cnd.cn_flags &= ~FSNODELOCKHELD;
                unlock_fsnode(ndp->ni_dvp, NULL);
        }       
        if (ndp->ni_cnd.cn_flags & HASBUF) {
                char *tmp = ndp->ni_cnd.cn_pnbuf;

                ndp->ni_cnd.cn_pnbuf = NULL;
                ndp->ni_cnd.cn_flags &= ~HASBUF;
                FREE_ZONE(tmp, ndp->ni_cnd.cn_pnlen, M_NAMEI);
        }
}


#define NUMPARMS 23

static void
kdebug_lookup(dp, cnp)
        struct vnode *dp;
        struct componentname *cnp;
{
        register unsigned int i, n;
        register int dbg_namelen;
        register int save_dbg_namelen;
        register char *dbg_nameptr;
        long dbg_parms[NUMPARMS];
        char dbg_buf[4];
        static char *dbg_filler = ">>>>";

        /* Collect the pathname for tracing */
        dbg_namelen = (cnp->cn_nameptr - cnp->cn_pnbuf) + cnp->cn_namelen;
        dbg_nameptr = cnp->cn_nameptr + cnp->cn_namelen;

        if (dbg_namelen > sizeof(dbg_parms))
            dbg_namelen = sizeof(dbg_parms);
        dbg_nameptr -= dbg_namelen;
        save_dbg_namelen = dbg_namelen;

        i = 0;

        while (dbg_namelen > 0) {
            if (dbg_namelen >= 4) {
                dbg_parms[i++] = *(long *)dbg_nameptr;
                dbg_nameptr += sizeof(long);
                dbg_namelen -= sizeof(long);
            } else {
                for (n = 0; n < dbg_namelen; n++)
                    dbg_buf[n] = *dbg_nameptr++;
                while (n <= 3) {
                    if (*dbg_nameptr)
                        dbg_buf[n++] = '>';
                    else
                        dbg_buf[n++] = 0;
                }
                dbg_parms[i++] = *(long *)&dbg_buf[0];

                break;
            }
        }
        while (i < NUMPARMS) {
            if (*dbg_nameptr)
                dbg_parms[i++] = *(long *)dbg_filler;
            else
                dbg_parms[i++] = 0;
        }

        /*
          In the event that we collect multiple, consecutive pathname
          entries, we must mark the start of the path's string.
        */
        KERNEL_DEBUG_CONSTANT((FSDBG_CODE(DBG_FSRW,36)) | DBG_FUNC_START,
                (unsigned int)dp, dbg_parms[0], dbg_parms[1], dbg_parms[2], 0);

        for (dbg_namelen = save_dbg_namelen-12, i=3;
             dbg_namelen > 0;
             dbg_namelen -=(4 * sizeof(long)), i+= 4)
          {
            KERNEL_DEBUG_CONSTANT((FSDBG_CODE(DBG_FSRW,36)) | DBG_FUNC_NONE,
                                  dbg_parms[i], dbg_parms[i+1], dbg_parms[i+2], dbg_parms[i+3], 0);
          }
}