xnu-792.17.14.tar.gz

[apple/xnu.git] / bsd / miscfs / volfs / volfs_vnops.c

/*
 * Copyright (c) 1998-2004 Apple Computer, Inc. All rights reserved.
 *
 * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
 * 
 * This file contains Original Code and/or Modifications of Original Code
 * as defined in and that are subject to the Apple Public Source License
 * Version 2.0 (the 'License'). You may not use this file except in
 * compliance with the License. The rights granted to you under the License
 * may not be used to create, or enable the creation or redistribution of,
 * unlawful or unlicensed copies of an Apple operating system, or to
 * circumvent, violate, or enable the circumvention or violation of, any
 * terms of an Apple operating system software license agreement.
 * 
 * Please obtain a copy of the License at
 * http://www.opensource.apple.com/apsl/ and read it before using this file.
 * 
 * The 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, QUIET ENJOYMENT OR NON-INFRINGEMENT.
 * Please see the License for the specific language governing rights and
 * limitations under the License.
 * 
 * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
 */

#include <mach/mach_types.h>

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/resourcevar.h>
#include <sys/kernel.h>
#include <sys/file.h>
#include <sys/filedesc.h>
#include <sys/stat.h>
#include <sys/proc_internal.h>  /* for p_fd */
#include <sys/kauth.h>
#include <sys/conf.h>
#include <sys/mount_internal.h>
#include <sys/vnode_internal.h>
#include <sys/malloc.h>
#include <sys/dirent.h>
#include <sys/namei.h>
#include <sys/attr.h>
#include <sys/kdebug.h>
#include <sys/queue.h>
#include <sys/uio_internal.h>

#include <sys/vm.h>
#include <sys/errno.h>
#include <vfs/vfs_support.h>

#include <kern/locks.h>

#include "volfs.h"

/*
 * volfs acts as a bridge between the requirements of the MacOS API and the Unix API.
 * MacOS applications describe files by a <Volume ID><Directory ID><File Name> triple.
 * The Unix API describes files by pathname.  Volfs is a virtual file system that sits over
 * the HFS VFS interface and allows files to be described by a <Volume ID>/<Directory ID>/<File Name>
 * pathname.
 *
 * The root of the volfs filesystem consists of directories named the volume ID's of all the
 * currently mounted filesystems which support the VFS vget() routine.  Each of those directories
 * supports the lookup by file ID of all files and directories within the filesystem.  When a
 * file or directory is resolved its vnode from that filesystem rather than a volfs vnode is returned
 * allowing immediate access to the target file or directory.
 *
 * Readdir on the root of the volfs filesystem returns the list of available file systems.  Readdir
 * on a filesystem node, however, returns only . and .. since it is not practical to list all
 * of the file ID's in a timely fashion and furthermore VFS does not provide a mechanism for
 * enumerating all of the file id's.
 *
 * Volume ID's are taken from the low 32 bits of the f_fsid field, formatted as a base 10 ASCII
 * string with no leading zeros (volume ID 1 is represented as "1").
 *
 * File ID's are created in same manner, with their 32 bits formatted as a base 10 ASCII
 * string with no leading zeros.
 *
 * Volfs does create a security hole since it is possible to bypass directory permissions higher
 * in the namespace tree.  This security hole is about the same as the one created by NFS which uses
 * a similar mechanism.
 */

static int  volfs_reclaim  (struct vnop_reclaim_args*);
static int  volfs_getattr  (struct vnop_getattr_args *);
static int  volfs_select   (struct vnop_select_args *);
static int  volfs_rmdir    (struct vnop_rmdir_args *);
static int  volfs_readdir  (struct vnop_readdir_args *);
static int  volfs_pathconf (struct vnop_pathconf_args *);
static int  volfs_lookup   (struct vnop_lookup_args *);

static int volfs_readdir_callback(mount_t, void *);
static int get_filevnode(struct mount *parent_fs, u_int id, vnode_t *ret_vnode, vfs_context_t context);
static int get_fsvnode(struct mount *our_mount, int id, vnode_t *ret_vnode);

/* for the call back function in volfs_readdir */
struct volfs_rdstruct {
        int             validindex;
        vnode_t         vp;
        int             rec_offset;
        struct uio * uio;
};

#define VOPFUNC int (*)(void *)

/* Global vfs data structures for volfs. */
int                 (**volfs_vnodeop_p) (void *);
struct vnodeopv_entry_desc volfs_vnodeop_entries[] = {
    {&vnop_default_desc, (VOPFUNC)vn_default_error},
    {&vnop_strategy_desc, (VOPFUNC)err_strategy},       /* strategy */
    {&vnop_bwrite_desc, (VOPFUNC)err_bwrite},           /* bwrite */
    {&vnop_lookup_desc, (VOPFUNC)volfs_lookup},         /* lookup */
    {&vnop_create_desc, (VOPFUNC)err_create},           /* create */
    {&vnop_whiteout_desc, (VOPFUNC)err_whiteout},       /* whiteout */
    {&vnop_mknod_desc, (VOPFUNC)err_mknod},             /* mknod */
    {&vnop_open_desc, (VOPFUNC)nop_open},               /* open */
    {&vnop_close_desc, (VOPFUNC)nop_close},             /* close */
    {&vnop_getattr_desc, (VOPFUNC)volfs_getattr},       /* getattr */
    {&vnop_setattr_desc, (VOPFUNC)err_setattr},         /* setattr */
    {&vnop_getattrlist_desc, (VOPFUNC)err_getattrlist}, /* getattrlist */
    {&vnop_setattrlist_desc, (VOPFUNC)err_setattrlist}, /* setattrlist */
    {&vnop_read_desc, (VOPFUNC)err_read},               /* read */
    {&vnop_write_desc, (VOPFUNC)err_write},             /* write */
    {&vnop_ioctl_desc, (VOPFUNC)err_ioctl},             /* ioctl */
    {&vnop_select_desc, (VOPFUNC)volfs_select},         /* select */
    {&vnop_exchange_desc, (VOPFUNC)err_exchange},       /* exchange */
    {&vnop_revoke_desc, (VOPFUNC)nop_revoke},           /* revoke */
    {&vnop_mmap_desc, (VOPFUNC)err_mmap},               /* mmap */
    {&vnop_fsync_desc, (VOPFUNC)err_fsync},             /* fsync */
    {&vnop_remove_desc, (VOPFUNC)err_remove},           /* remove */
    {&vnop_link_desc, (VOPFUNC)err_link},               /* link */
    {&vnop_rename_desc, (VOPFUNC)err_rename},           /* rename */
    {&vnop_mkdir_desc, (VOPFUNC)err_mkdir},             /* mkdir */
    {&vnop_rmdir_desc, (VOPFUNC)volfs_rmdir},           /* rmdir */
    {&vnop_symlink_desc, (VOPFUNC)err_symlink},         /* symlink */
    {&vnop_readdir_desc, (VOPFUNC)volfs_readdir},       /* readdir */
    {&vnop_readdirattr_desc, (VOPFUNC)err_readdirattr}, /* readdirattr */
    {&vnop_readlink_desc, (VOPFUNC)err_readlink},       /* readlink */
    {&vnop_inactive_desc, (VOPFUNC)err_inactive},       /* inactive */
    {&vnop_reclaim_desc, (VOPFUNC)volfs_reclaim},       /* reclaim */
    {&vnop_pathconf_desc, (VOPFUNC)volfs_pathconf},     /* pathconf */
    {&vnop_advlock_desc, (VOPFUNC)err_advlock},         /* advlock */
    {&vnop_allocate_desc, (VOPFUNC)err_allocate},       /* allocate */
        {&vnop_pagein_desc, (VOPFUNC)err_pagein},       /* pagein */
        {&vnop_pageout_desc, (VOPFUNC)err_pageout},     /* pageout */
        {&vnop_devblocksize_desc, (VOPFUNC)err_devblocksize},   /* devblocksize */
        {&vnop_searchfs_desc, (VOPFUNC)err_searchfs},   /* searchfs */
        {&vnop_copyfile_desc, (VOPFUNC)err_copyfile },  /* Copyfile */
        {&vnop_blktooff_desc, (VOPFUNC)err_blktooff},   /* blktooff */
        {&vnop_offtoblk_desc, (VOPFUNC)err_offtoblk },  /* offtoblk */
        {&vnop_blockmap_desc, (VOPFUNC)err_blockmap },          /* blockmap */
   {(struct vnodeop_desc *) NULL, (int (*) ()) NULL}
};

/*
 * Oh what a tangled web we weave.  This structure will be used by
 * bsd/vfs/vfs_conf.c to actually do the initialization of volfs_vnodeop_p
 */
struct vnodeopv_desc volfs_vnodeop_opv_desc =
{&volfs_vnodeop_p, volfs_vnodeop_entries};

static char gDotDot[] = "..";

struct finfo {
    fsobj_id_t parID;
};

struct finfoattrbuf {
    unsigned long length;
    struct finfo fi;
};


static int volfs_getattr_callback(mount_t, void *);


/*
 * volfs_reclaim - Reclaim a vnode so that it can be used for other purposes.
 */
static int
volfs_reclaim(ap)
    struct vnop_reclaim_args /* { struct vnode *a_vp; vfs_context_t a_context; } */ *ap;
{
        struct vnode *vp = ap->a_vp;
        void *data = vp->v_data;

        vp->v_data = NULL;
        FREE(data, M_VOLFSNODE);

        return (0);
}

struct volfsgetattr_struct{
        int     numMounts;
        vnode_t a_vp;
};

static int
volfs_getattr_callback(mount_t mp, void * arg)
{
        struct volfsgetattr_struct *vstrp = (struct volfsgetattr_struct *)arg;

        if (mp != vnode_mount(vstrp->a_vp) && validfsnode(mp))
                vstrp->numMounts++;
        return(VFS_RETURNED);
}

/*
 * volfs_getattr - fill in the attributes for this vnode
 */
static int
volfs_getattr(ap)
    struct vnop_getattr_args    /* { struct vnode *a_vp; struct vnode_attr *a_vap;
        vfs_context_t a_context; } */ *ap;
{
    struct volfs_vndata *priv_data;
    struct vnode                *a_vp;
    struct vnode_attr   *a_vap;
    int                 numMounts = 0;
    struct volfsgetattr_struct vstr;
    struct timespec ts;

    a_vp = ap->a_vp;
    a_vap = ap->a_vap;

    priv_data = a_vp->v_data;

    VATTR_RETURN(a_vap, va_type, VDIR);
    VATTR_RETURN(a_vap, va_mode, 0555);
    VATTR_RETURN(a_vap, va_nlink, 2);
    VATTR_RETURN(a_vap, va_uid, 0);
    VATTR_RETURN(a_vap, va_gid, 0);
    VATTR_RETURN(a_vap, va_fsid, (int) a_vp->v_mount->mnt_vfsstat.f_fsid.val[0]);
    VATTR_RETURN(a_vap, va_fileid, (uint64_t)((u_long)priv_data->nodeID));
    VATTR_RETURN(a_vap, va_acl, NULL);

    /*
     * If it's the root vnode calculate its size based on the number of eligible
     * file systems
     */
    if (priv_data->vnode_type == VOLFS_ROOT) {
            vstr.numMounts = 0;
            vstr.a_vp = a_vp;

            vfs_iterate(LK_NOWAIT, volfs_getattr_callback, (void *)&vstr);

            numMounts = vstr.numMounts;

            VATTR_RETURN(a_vap, va_data_size, (numMounts + 2) * VLFSDIRENTLEN);
    } else {
            VATTR_RETURN(a_vap, va_data_size, 2 * VLFSDIRENTLEN);
    }

    VATTR_RETURN(a_vap, va_iosize, 512);
    ts.tv_sec = boottime_sec();
    ts.tv_nsec = 0;
    VATTR_RETURN(a_vap, va_access_time, ts);
    VATTR_RETURN(a_vap, va_modify_time, ts);
    VATTR_RETURN(a_vap, va_change_time, ts);

    VATTR_RETURN(a_vap, va_gen, 0);
    VATTR_RETURN(a_vap, va_flags, 0);
    VATTR_RETURN(a_vap, va_rdev, 0);
    VATTR_RETURN(a_vap, va_filerev, 0);

    return (0);
}

/*
 * volfs_select - just say OK.  Only possible op is readdir
 */
static int
volfs_select(__unused struct vnop_select_args *ap)
{
        return (1);
}

/*
 * vofls_rmdir - not possible to remove directories in volfs
 */
static int
volfs_rmdir(ap)
    struct vnop_rmdir_args      /* { struct vnode *a_dvp; struct vnode *a_vp;
        struct componentname *a_cnp; vfs_context_t a_context; } */ *ap;
{
    if (ap->a_dvp == ap->a_vp) {
                (void) nop_rmdir(ap);
                return (EINVAL);
    } else
                return (err_rmdir(ap));
}



static int
volfs_readdir_callback(mount_t mp, void * v)
{
        struct volfs_rdstruct * vcsp = (struct volfs_rdstruct *)v;
        struct dirent       local_dir;
        int error;

            if ((mp != vnode_mount(vcsp->vp)) && validfsnode(mp))
                                vcsp->validindex++;

            if (vcsp->rec_offset == vcsp->validindex)
              {
                local_dir.d_fileno = mp->mnt_vfsstat.f_fsid.val[0];
                local_dir.d_type = DT_DIR;
                local_dir.d_reclen = VLFSDIRENTLEN;
                local_dir.d_namlen = sprintf(&local_dir.d_name[0], "%d", mp->mnt_vfsstat.f_fsid.val[0]);
                error = uiomove((char *) &local_dir, VLFSDIRENTLEN, vcsp->uio);
                vcsp->rec_offset++;
              }

                return(VFS_RETURNED);
}

/*
 * volfs_readdir - Get directory entries
 *
 * Directory listings are only produced for the root volfs node.  Filesystems
 * just return . & ..
 * Filesystems contained within the volfs root are named by the decimal
 * equivalent of the f_fsid.val[0] from their mount structure (typically
 * the device id of the volume).  The maximum length for a name, then is
 * 10 characters.
 */
static int
volfs_readdir(ap)
    struct vnop_readdir_args    /* { struct vnode *a_vp; struct uio *a_uio;
                                 * int *a_eofflag; int
        *ncookies; u_long **a_cookies; vfs_context_t a_context; } */ *ap;
{
    struct volfs_vndata *priv_data;
    register struct uio *uio = ap->a_uio;
    int                 error = 0;
    size_t              count, lost;
    int                 rec_offset;
    struct dirent       local_dir;
    int                 i;
    int                                 starting_resid;
    off_t               off;
        struct volfs_rdstruct vcs;
    
        off = uio->uio_offset;
    priv_data = ap->a_vp->v_data;
        // LP64todo - fix this!
    starting_resid = count = uio_resid(uio);
 
    /* Make sure we don't return partial entries. */
    count -= (uio->uio_offset + count) & (VLFSDIRENTLEN - 1);
        if (count <= 0) {
                return (EINVAL);
        }
    /*
     * Make sure we're starting on a directory boundary
     */
        if (off & (VLFSDIRENTLEN - 1)) {
                return (EINVAL);
        }
    rec_offset = off / VLFSDIRENTLEN;
        // LP64todo - fix this!
    lost = uio_resid(uio) - count;
    uio_setresid(uio, count);
    uio_iov_len_set(uio, count); 
#if LP64_DEBUG
        if (IS_VALID_UIO_SEGFLG(uio->uio_segflg) == 0) {
                panic("%s :%d - invalid uio_segflg\n", __FILE__, __LINE__); 
        }
#endif /* LP64_DEBUG */

    local_dir.d_reclen = VLFSDIRENTLEN;
    /*
     * We must synthesize . and ..
     */

    if (rec_offset == 0)
      {
        /*
         * Synthesize .
         */
        local_dir.d_fileno = priv_data->nodeID;
        local_dir.d_type = DT_DIR;
        local_dir.d_namlen = 1;
        local_dir.d_name[0] = '.';
        for (i = 1; i < MAXVLFSNAMLEN; i++)
            local_dir.d_name[i] = 0;
        error = uiomove((char *) &local_dir, VLFSDIRENTLEN, uio);
        rec_offset++;
      }
    if (rec_offset == 1)
      {
        /*
         * Synthesize ..
         * We only have two levels in the volfs hierarchy.  Root's
         * .. points to itself and the second level points to root,
         * hence we've hardcoded d_fileno for .. here
         */
        local_dir.d_fileno = ROOT_DIRID;
        local_dir.d_type = DT_DIR;
        local_dir.d_namlen = 2;
        local_dir.d_name[0] = '.';
        local_dir.d_name[1] = '.';
        for (i = 2; i < MAXVLFSNAMLEN; i++)
            local_dir.d_name[i] = 0;
        error = uiomove((char *) &local_dir, VLFSDIRENTLEN, uio);
        rec_offset++;
      }

    /*
     * OK, we've given them the . & .. entries.  If this is a
     * filesystem node then we've gone as far as we're going
     * to go
     */
    if (priv_data->vnode_type == VOLFS_FSNODE)
        {
        *ap->a_eofflag = 1;     /* we got all the way to the end */
        return (error);
        }

    if (rec_offset > 1) {
                vcs.validindex = 1;             /* we always have "." and ".." */
                vcs.rec_offset = rec_offset;
                vcs.vp = ap->a_vp;
                vcs.uio = uio;
                
        
                vfs_iterate(0, volfs_readdir_callback, &vcs);

        //if (mp == (void *) &mountlist)
            *ap->a_eofflag = 1; /* we got all the way to the end */
    }
    uio_setresid(uio, (uio_resid(uio) + lost));

    if (starting_resid == uio_resid(uio))
        uio->uio_offset = 0;

    return (error);
}


/*
 * validfsnode - test to see if a file system supports VGET
 *
 * This can cause context switching, so caller should be lock safe
 */
int
validfsnode(struct mount *fsnode)
{

        /*
         * Just check to see if the the mount flag is set, if it is we assume the
         * file system supports all of volfs symantecs
         */

    if ((! (fsnode->mnt_kern_flag & MNTK_UNMOUNT)) && (fsnode->mnt_flag & MNT_DOVOLFS))
                return 1;
        else 
                return 0;
}

/*
 * volfs_pathconf - Return POSIX pathconf information applicable to ufs filesystems.
 */
static int
volfs_pathconf(ap)
    struct vnop_pathconf_args   /* { struct vnode *a_vp; int a_name; int
        *a_retval; vfs_context_t a_context; } */ *ap;
{
    switch (ap->a_name)
      {
        case _PC_LINK_MAX:
            *ap->a_retval = LINK_MAX;
            return (0);
        case _PC_NAME_MAX:
            *ap->a_retval = NAME_MAX;
            return (0);
        case _PC_PATH_MAX:
            *ap->a_retval = PATH_MAX;
            return (0);
        case _PC_PIPE_BUF:
            *ap->a_retval = PIPE_BUF;
            return (0);
        case _PC_CHOWN_RESTRICTED:
            *ap->a_retval = 1;
            return (0);
        case _PC_NO_TRUNC:
            *ap->a_retval = 1;
            return (0);
        default:
            return (EINVAL);
      }
    /* NOTREACHED */
}

/* 
 * get_parentvp() - internal routine that tries to lookup the parent of vpp.
 * On success, *vpp is the parent vp and is returned with a reference. 
 */
static int
get_parentvp(struct vnode **vpp, struct mount *mp, vfs_context_t context)
{
        int result;
        struct vnode_attr va;
        struct vnode *child_vp = *vpp;
        
        VATTR_INIT(&va);
        VATTR_WANTED(&va, va_parentid);
        result = vnode_getattr(child_vp, &va, context);
        if (result) {
                return result;
        }

        /* Shift attention to the parent directory vnode: */
        result = VFS_VGET(mp, (ino64_t)va.va_parentid, vpp, context);

        if (result == 0 && child_vp->v_parent != *vpp) {
                vnode_update_identity(child_vp, *vpp, NULL, 0, 0, VNODE_UPDATE_PARENT);
        }

        return result;
}       


/*
 * Look up the parent directory of a given vnode.
 */
static int
lookup_parent(vnode_t child_vp, vnode_t *parent_vpp, int is_authorized, vfs_context_t context)
{
        struct componentname cn;
        vnode_t new_vp;
        int error;

        *parent_vpp = NULLVP;

        if (is_authorized == 0) {
                error = vnode_authorize(child_vp, NULL, KAUTH_VNODE_SEARCH, context);
                if (error != 0) {
                        return (error);
                }
        }
        new_vp = child_vp->v_parent;

        if (new_vp != NULLVP) {
                if ( (error = vnode_getwithref(new_vp)) == 0 )
                        *parent_vpp = new_vp;
                return (error);
        }
        bzero(&cn, sizeof(cn));
        cn.cn_nameiop = LOOKUP;
        cn.cn_context = context;
        cn.cn_pnbuf = CAST_DOWN(caddr_t, &gDotDot);
        cn.cn_pnlen = strlen(cn.cn_pnbuf);
        cn.cn_nameptr = cn.cn_pnbuf;
        cn.cn_namelen = cn.cn_pnlen;
        cn.cn_flags = (FOLLOW | LOCKLEAF | ISLASTCN | ISDOTDOT);

        error = VNOP_LOOKUP(child_vp, &new_vp, &cn, context);
        if (error != 0) {
                return(error);
        }
        if (new_vp == child_vp) {
                vnode_put(new_vp);
                return ELOOP;
        }
        if (child_vp->v_parent == NULLVP) {
                vnode_update_identity(child_vp, new_vp, NULL, 0, 0, VNODE_UPDATE_PARENT);
        }
        *parent_vpp = new_vp;
        return 0;
}


/*
 *      verify_fullpathaccess(ret_vnode);
 */

static int
verify_fullpathaccess(struct vnode *targetvp, vfs_context_t context)
{
        struct vnode *vp, *parent_vp;
        struct mount *mp = targetvp->v_mount;
        struct proc *p = vfs_context_proc(context);
        int result;
        int dp_authorized;
        struct filedesc *fdp = p->p_fd; /* pointer to file descriptor state */
        
        vp = targetvp;
        dp_authorized = 0;
        
        /* get the parent directory. */
        if ((vp->v_flag & VROOT) == 0 && vp != fdp->fd_cdir && vp != fdp->fd_rdir) {
                if (vp->v_parent == NULLVP || (vp->v_flag & VISHARDLINK) || (vnode_getwithref(vp->v_parent) != 0)) {
                        if (vp->v_type == VDIR) {
                                result = lookup_parent(vp, &parent_vp, dp_authorized, context);
        
                                /*
                                 * If the lookup fails with EACCES and the vp is a directory,
                                 * we should try again but bypass authorization check. Without this
                                 * workaround directories that you can navigate to but not traverse will 
                                 * disappear when clicked in the Finder.
                                 */
                                if (result == EACCES && (vp->v_flag & VROOT) == 0) {
                                        dp_authorized = 1;  /* bypass auth check */
                                        if (lookup_parent(vp, &parent_vp, dp_authorized, context) == 0) {
                                                result = 0;
                                        }
                                        dp_authorized = 0; /* force us to authorize */
                                }
                                vp = parent_vp;
                        }
                        else {
                                /*
                                 * this is not a directory so we must get parent object ID
                                 */
                                result = get_parentvp(&vp, mp, context);
                                parent_vp = vp;
                        }
                        if (result != 0) 
                                goto err_exit;
                }
                else {
                        /*
                         * we where able to get a reference on v_parent
                         */
                        parent_vp = vp = vp->v_parent;
                }
        } 

        /*
         * Keep going up until either the process's root or the process's working 
         * directory is hit, either one of which are potential valid starting points 
         * for a full pathname
         */
        while (vp != NULLVP) {

                result = reverse_lookup(vp, &parent_vp, fdp, context, &dp_authorized);
                if (result == 0) {
                        /*
                         * we're done and we have access
                         */
                        break;
                }
                if (vp != parent_vp) {
                        /*
                         * we where able to walk up the parent chain so now we don't need
                         * vp any longer
                         */
                        vnode_put(vp);  
                        vp = parent_vp;
                }
                /*
                 * we have a referenced vp at this point... if dp_authorized == 1, than
                 * it's been authorized for search, but v_parent was NULL...
                 * if dp_authorized == 0, than we need to do the authorization check
                 * before looking up the parent
                 */
                if ((vp->v_flag & VROOT) != 0 ||
                    vp == fdp->fd_cdir || vp == fdp->fd_rdir) {
                        /*
                         * we're already at the termination point, which implies that
                         * the authorization check in the cache failed (otherwise we
                         * would have returned 'done' from "reverse_lookup"... so,
                         * do the authorization and bail
                         */
                        result = vnode_authorize(vp, NULL, KAUTH_VNODE_SEARCH, context);
                        goto lookup_exit;
                }
                result = lookup_parent(vp, &parent_vp, dp_authorized, context);
                if (result != 0) {
                        goto lookup_exit;
                }
                if (vp != parent_vp) {
                        /*
                         * got the parent so now we don't need vp any longer
                         */
                        vnode_put(vp);  
                        vp = parent_vp;
                }
        } /* while loop */

        /*
         * Success: the caller has complete access to the initial vnode
         */
        result = 0; 

lookup_exit:
        if (vp != NULLVP && vp != targetvp) {
                vnode_put(vp);
        }
                
err_exit:
        return result;
};


/*
 * get_fsvnode - internal routine to create a vnode for a file system.  Called with mount pointer,
 *   id of filesystem to lookup and pointer to vnode pointer to fill in
 */
static int
get_fsvnode(struct mount *our_mount, int id, vnode_t *ret_vnode)
{
    struct mount       *cur_mount;
        fsid_t                          cur_fsid;
    struct vnode       *cur_vnode;
    struct volfs_vndata *cur_privdata;
        int                                     retval;
        struct vnode_fsparam vfsp;
        int     vid = 0;

    /*
     * OK, first look up the matching mount on the list of mounted file systems
     */
        /* the following will return the mount point with vfs_busy held */
        cur_mount = mount_lookupby_volfsid(id, 1);

    if (cur_mount == NULL) {
        /*
         * No mounted file system by the specified ID currently exists in the system.
         *
         * XXX We could deal with a vnode that is still hanging about for an FS that
         * does not exists or has been unmounted now, or count on the update below
         * to happen later...
         */
        *ret_vnode = NULL;
        return ENOENT;
    };

        cur_fsid = cur_mount->mnt_vfsstat.f_fsid;

    /*
     * Now search the list attached to the mount structure to
     * see if this vnode is already floating around
     */
search_vnodelist:
        mount_lock(our_mount);
        TAILQ_FOREACH(cur_vnode, &our_mount->mnt_vnodelist, v_mntvnodes)  {
        cur_privdata = (struct volfs_vndata *) cur_vnode->v_data;
        if (cur_privdata->nodeID == (unsigned int)id)
            {
            if (cur_privdata->fs_mount != cur_mount) {
                cur_privdata->fs_mount = cur_mount;
                cur_privdata->fs_fsid = cur_fsid;
            };
            break;
            }
        }
        mount_unlock(our_mount);

    if (cur_vnode) {
        vid = vnode_vid(cur_vnode);

        /*
         * use vnode_getwithvid since it will wait for a vnode currently being
         * terminated... if it returns an error, cur_vnode will not be what we
         * think it is, try again
         */
        if (vnode_getwithvid(cur_vnode, vid) != 0) {
            goto search_vnodelist;
        };
        }
    else
      {
        MALLOC(cur_privdata, struct volfs_vndata *,
               sizeof(struct volfs_vndata), M_VOLFSNODE, M_WAITOK);

        cur_privdata->vnode_type = VOLFS_FSNODE;
        cur_privdata->nodeID = id;

        cur_privdata->fs_mount = cur_mount;
        cur_privdata->fs_fsid = cur_fsid;

                vfsp.vnfs_mp = our_mount;
                vfsp.vnfs_vtype = VDIR;
                vfsp.vnfs_str = "volfs";
                vfsp.vnfs_dvp = 0;
                vfsp.vnfs_fsnode = cur_privdata;
                vfsp.vnfs_cnp = 0;
                vfsp.vnfs_vops = volfs_vnodeop_p;
                vfsp.vnfs_rdev = 0;
                vfsp.vnfs_filesize = 0;
                vfsp.vnfs_flags = VNFS_NOCACHE | VNFS_CANTCACHE;
                vfsp.vnfs_marksystem = 0;
                vfsp.vnfs_markroot = 0;

                retval = vnode_create(VNCREATE_FLAVOR, VCREATESIZE, &vfsp, &cur_vnode);
        if (retval != 0) {
            FREE(cur_privdata, M_VOLFSNODE);
                        goto out;
        };
                cur_vnode->v_tag = VT_VOLFS;
                        
      }

    *ret_vnode = cur_vnode;
        retval = 0;
out:
        vfs_unbusy(cur_mount);
    return (retval);
}



/*
 * get_filevnode - returns the vnode for the given id within a filesystem.  The parent vnode
 *         is a filesystem, id is the 32-bit id of the file/directory and ret_vnode is a pointer
 *              to a vnode pointer
 */
static int
get_filevnode(struct mount *parent_fs, u_int id, vnode_t *ret_vnode, vfs_context_t context)
{
    int                 retval;

again:
        /*
         * Special case 2 to mean the root of a file system
         */
        if (id == 2)
                retval = VFS_ROOT(parent_fs, ret_vnode, context);
        else
                retval = VFS_VGET(parent_fs, (ino64_t)id, ret_vnode, context);
        if (retval) goto error;

        retval = verify_fullpathaccess(*ret_vnode, context);
        if (retval) {
                /* An error was encountered verifying that the caller has,
                   in fact, got access all the way from "/" or their working
                   directory to the specified item...
                 */
                vnode_put(*ret_vnode);
                *ret_vnode = NULL;
                /* vnode was recycled during access verification. */
                if (retval == EAGAIN) {
                        goto again;
                }
        };

error:
    return (retval);
}


static int
volfs_lookup(struct vnop_lookup_args *ap)
{
        struct volfs_vndata *priv_data;
        char  *nameptr;
        long  namelen;
        struct mount  *parent_fs;
        vnode_t vp;
        int  isdot_or_dotdot = 0;
        int  ret_err = ENOENT;
        char firstchar;
        int ret_val;

#if 0
        KERNEL_DEBUG((FSDBG_CODE(DBG_FSVN, 8)) | DBG_FUNC_START,
                     (unsigned int)ap->a_dvp, (unsigned int)ap->a_cnp, (unsigned int)p, 0, 0);
#endif
        priv_data = ap->a_dvp->v_data;
        nameptr = ap->a_cnp->cn_nameptr;
        namelen = ap->a_cnp->cn_namelen;
        firstchar = nameptr[0];

        /* First check for "." and ".." */
        if (firstchar == '.') {
                if (namelen == 1) {
                        /* "." requested */
                        isdot_or_dotdot = 1;
                        *ap->a_vpp = ap->a_dvp;
                        vnode_get(*ap->a_vpp);
                        ret_err = 0;
                } else if (nameptr[1] == '.' && namelen == 2) {
                        /* ".." requested */
                        isdot_or_dotdot = 1;
                        ret_err = VFS_ROOT(ap->a_dvp->v_mount, ap->a_vpp, ap->a_context);
                }
        } else if (firstchar == '@') { /* '@' is alias for system root */
                if ((namelen == 1) && (priv_data->vnode_type != VOLFS_ROOT)) {
                        /* the following returns with iteration count on mount point */
                        parent_fs = mount_list_lookupby_fsid(&priv_data->fs_fsid, 0, 1);
                        if (parent_fs) {
                                ret_val = vfs_busy(parent_fs, LK_NOWAIT);
                                mount_iterdrop(parent_fs);
                                if (ret_val !=0) {
                                        *ap->a_vpp = NULL;
                                        ret_err = ENOENT;
                                } else {
                                        ret_err = VFS_ROOT(parent_fs, ap->a_vpp, ap->a_context);
                                        vfs_unbusy(parent_fs);
                                }
                        } else {
                                *ap->a_vpp = NULL;
                                ret_err = ENOENT;
                        }
                } else {
                        *ap->a_vpp = NULL;
                        ret_err = ENOENT;
                }
        } else if (namelen <= 10 && firstchar > '0' && firstchar <= '9') {
                char    *check_ptr;
                u_long  id;

                id = strtoul(nameptr, &check_ptr, 10);

                /*
                 * strtol will leave us at the first non-numeric character.
                 * we've checked to make sure the component name does
                 * begin with a numeric so check_ptr must wind up on
                 * the terminating null or there was other junk following the
                 * number
                 */
                if ((check_ptr - nameptr) == namelen) {
                        if (priv_data->vnode_type == VOLFS_ROOT) {
                                /*
                                 * OPTIMIZATION
                                 *
                                 * Obtain the mountpoint and call VFS_VGET in
                                 * one step (ie without creating a vnode for
                                 * the mountpoint).
                                 */
                                if (check_ptr[0] == '/' &&
                                    check_ptr[1] > '0' && check_ptr[1] <= '9') {
                                        struct mount *mp;
                                        struct vnode *vp;
                                        u_long  id2;
                                        char *endptr;
                
                                        /* this call will return mount point with vfs_busy held */
                                        mp = mount_lookupby_volfsid(id, 1);
                                        if (mp == NULL) {
                                                *ap->a_vpp = NULL;
                                                return ENOENT;
                                        }
                                        id2 = strtoul(&check_ptr[1], &endptr, 10);
                                        if ((endptr[0] == '/' || endptr[0] == '\0') &&
                                            get_filevnode(mp, id2, &vp, ap->a_context) == 0) {
                                                ap->a_cnp->cn_consume = endptr - check_ptr;
                                                *ap->a_vpp = vp;
                                                vfs_unbusy(mp);
                                                return (0);
                                        }
                                        vfs_unbusy(mp);
                                }
                                /* Fall through to default behavior... */

                                ret_err = get_fsvnode(ap->a_dvp->v_mount, id, ap->a_vpp);

                        } else {
                                parent_fs = mount_list_lookupby_fsid(&priv_data->fs_fsid, 0, 1);
                                if (parent_fs) {
                                        ret_val = vfs_busy(parent_fs, LK_NOWAIT);
                                        mount_iterdrop(parent_fs);
                                        if (ret_val !=0) {
                                                *ap->a_vpp = NULL;
                                                ret_err = ENOENT;
                                        } else {
                                                ret_err = get_filevnode(parent_fs, id, ap->a_vpp, ap->a_context);
                                                vfs_unbusy(parent_fs);
                                        }
                                } else {
                                                *ap->a_vpp = NULL;
                                                ret_err = ENOENT;
                                }
                        }
                }
        }
        vp = *ap->a_vpp;

        if ( ret_err == 0 && !isdot_or_dotdot && (vp != NULLVP) && (vp->v_parent == NULLVP))
                vnode_update_identity(vp, ap->a_dvp, NULL, 0, 0, VNODE_UPDATE_PARENT);

#if 0
        KERNEL_DEBUG((FSDBG_CODE(DBG_FSVN, 8)) | DBG_FUNC_START,
                     (unsigned int)ap->a_dvp, (unsigned int)ap->a_cnp, (unsigned int)p, ret_err, 0);
#endif
        return (ret_err);
}