[apple/xnu.git] / bsd / miscfs / devfs / devfs_vnops.c

/*
 * Copyright (c) 2000-2004 Apple Computer, Inc. All rights reserved.
 *
 * @APPLE_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. 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_LICENSE_HEADER_END@
 */
/*
 * Copyright 1997,1998 Julian Elischer.  All rights reserved.
 * julian@freebsd.org
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *  1. Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 *  2. Redistributions in binary form must reproduce the above copyright notice,
 *     this list of conditions and the following disclaimer in the documentation
 *     and/or other materials provided with the distribution.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER ``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 HOLDER 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.
 * 
 * devfs_vnops.c
 */

/*
 * HISTORY
 *  Clark Warner (warner_c@apple.com) Tue Feb 10 2000
 *  - Added err_copyfile to the vnode operations table
 *  Dieter Siegmund (dieter@apple.com) Thu Apr  8 14:08:19 PDT 1999
 *  - instead of duplicating specfs here, created a vnode-ops table
 *    that redirects most operations to specfs (as is done with ufs);
 *  - removed routines that made no sense
 *  - cleaned up reclaim: replaced devfs_vntodn() with a macro VTODN()
 *  - cleaned up symlink, link locking
 *  - added the devfs_lock to protect devfs data structures against
 *    driver's calling devfs_add_devswf()/etc.
 *  Dieter Siegmund (dieter@apple.com) Wed Jul 14 13:37:59 PDT 1999
 *  - free the devfs devnode in devfs_inactive(), not just in devfs_reclaim()
 *    to free up kernel memory as soon as it's available
 *  - got rid of devfsspec_{read, write}
 *  Dieter Siegmund (dieter@apple.com) Fri Sep 17 09:58:38 PDT 1999
 *  - update the mod/access times
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/namei.h>
#include <sys/kernel.h>
#include <sys/fcntl.h>
#include <sys/conf.h>
#include <sys/disklabel.h>
#include <sys/lock.h>
#include <sys/stat.h>
#include <sys/mount_internal.h>
#include <sys/proc.h>
#include <sys/kauth.h>
#include <sys/time.h>
#include <sys/vnode_internal.h>
#include <miscfs/specfs/specdev.h>
#include <sys/dirent.h>
#include <sys/vmmeter.h>
#include <sys/vm.h>
#include <sys/uio_internal.h>

#include "devfsdefs.h"

static int devfs_update(struct vnode *vp, struct timeval *access,
                        struct timeval *modify);


/*
 * Convert a component of a pathname into a pointer to a locked node.
 * This is a very central and rather complicated routine.
 * If the file system is not maintained in a strict tree hierarchy,
 * this can result in a deadlock situation (see comments in code below).
 *
 * 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 and the target of the pathname
 * exists, lookup returns both the target and its parent directory locked.
 * When creating or renaming and LOCKPARENT is specified, the target may
 * not be ".".  When deleting and LOCKPARENT is specified, the target may
 * be "."., but the caller must check to ensure it does an vrele and DNUNLOCK
 * instead of two DNUNLOCKs.
 *
 * Overall outline of devfs_lookup:
 *
 *      check accessibility of directory
 *      null terminate the component (lookup leaves the whole string alone)
 *      look for name in cache, if found, then if at end of path
 *        and deleting or creating, drop it, else return name
 *      search for name in directory, to found or notfound
 * notfound:
 *      if creating, return locked directory,
 *      else return error
 * found:
 *      if at end of path and deleting, return information to allow delete
 *      if at end of path and rewriting (RENAME and LOCKPARENT), lock target
 *        node and return info to allow rewrite
 *      if not at end, add name to cache; if at end and neither creating
 *        nor deleting, add name to cache
 * On return to lookup, remove the null termination we put in at the start.
 *
 * NOTE: (LOOKUP | LOCKPARENT) currently returns the parent node unlocked.
 */
static int
devfs_lookup(struct vnop_lookup_args *ap)
        /*struct vnop_lookup_args {
                struct vnode * a_dvp; directory vnode ptr
                struct vnode ** a_vpp; where to put the result
                struct componentname * a_cnp; the name we want
                vfs_context_t a_context;
        };*/
{
        struct componentname *cnp = ap->a_cnp;
        vfs_context_t ctx = cnp->cn_context;
        struct proc *p = vfs_context_proc(ctx);
        struct vnode *dir_vnode = ap->a_dvp;
        struct vnode **result_vnode = ap->a_vpp;
        devnode_t *   dir_node;       /* the directory we are searching */
        devnode_t *   node = NULL;       /* the node we are searching for */
        devdirent_t * nodename;
        int flags = cnp->cn_flags;
        int op = cnp->cn_nameiop;       /* LOOKUP, CREATE, RENAME, or DELETE */
        int wantparent = flags & (LOCKPARENT|WANTPARENT);
        int error = 0;
        char    heldchar;       /* the char at the end of the name componet */

retry:

        *result_vnode = NULL; /* safe not sorry */ /*XXX*/

        //if (dir_vnode->v_usecount == 0)
            //printf("devfs_lookup: dir had no refs ");
        dir_node = VTODN(dir_vnode);

        /*
         * Make sure that our node is a directory as well.
         */
        if (dir_node->dn_type != DEV_DIR) {
                return (ENOTDIR);
        }

        DEVFS_LOCK();
        /*
         * temporarily terminate string component
         */
        heldchar = cnp->cn_nameptr[cnp->cn_namelen];
        cnp->cn_nameptr[cnp->cn_namelen] = '\0';

        nodename = dev_findname(dir_node, cnp->cn_nameptr);
        /*
         * restore saved character
         */
        cnp->cn_nameptr[cnp->cn_namelen] = heldchar;

        if (nodename) {
                /* entry exists */
                node = nodename->de_dnp;

                /* Do potential vnode allocation here inside the lock 
                 * to make sure that our device node has a non-NULL dn_vn
                 * associated with it.  The device node might otherwise
                 * get deleted out from under us (see devfs_dn_free()).
                 */
                error = devfs_dntovn(node, result_vnode, p);
        }
        DEVFS_UNLOCK();

        if (error) {
                if (error == EAGAIN)
                        goto retry;
                return error;
        }
        if (!nodename) {
                /*
                 * we haven't called devfs_dntovn if we get here
                 * we have not taken a reference on the node.. no
                 * vnode_put is necessary on these error returns
                 *
                 * If it doesn't exist and we're not the last component,
                 * or we're at the last component, but we're not creating
                 * or renaming, return ENOENT.
                 */
                if (!(flags & ISLASTCN) || !(op == CREATE || op == RENAME)) {
                        return ENOENT;
                }
                /*
                 * We return with the directory locked, so that
                 * the parameters we set up above will still be
                 * valid if we actually decide to add a new entry.
                 * We return ni_vp == NULL to indicate that the entry
                 * does not currently exist; we leave a pointer to
                 * the (locked) directory vnode in namei_data->ni_dvp.
                 *
                 * NB - if the directory is unlocked, then this
                 * information cannot be used.
                 */
                return (EJUSTRETURN);
        }
        /*
         * from this point forward, we need to vnode_put the reference
         * picked up in devfs_dntovn if we decide to return an error
         */

        /*
         * If deleting, and at end of pathname, return
         * parameters which can be used to remove file.
         * If the wantparent flag isn't set, we return only
         * the directory (in namei_data->ni_dvp), otherwise we go
         * on and lock the node, being careful with ".".
         */
        if (op == DELETE && (flags & ISLASTCN)) {

                /*
                 * we are trying to delete '.'.  What does this mean? XXX
                 */
                if (dir_node == node) {
                        if (*result_vnode) {
                                vnode_put(*result_vnode);
                                *result_vnode = NULL;
                        }                               
                        if ( ((error = vnode_get(dir_vnode)) == 0) ) {
                                *result_vnode = dir_vnode;
                        }
                        return (error);
                }
                return (0);
        }

        /*
         * If rewriting (RENAME), return the vnode and the
         * information required to rewrite the present directory
         * Must get node of directory entry to verify it's a
         * regular file, or empty directory.
         */
        if (op == RENAME && wantparent && (flags & ISLASTCN)) {

                /*
                 * Careful about locking second node.
                 * This can only occur if the target is ".".
                 */
                if (dir_node == node) {
                        error = EISDIR;
                        goto drop_ref;
                }
                return (0);
        }

        /*
         * Step through the translation in the name.  We do not unlock the
         * directory because we may need it again if a symbolic link
         * is relative to the current directory.  Instead we save it
         * unlocked as "saved_dir_node" XXX.  We must get the target
         * node before unlocking
         * the directory to insure that the node will not be removed
         * before we get it.  We prevent deadlock by always fetching
         * nodes from the root, moving down the directory tree. Thus
         * when following backward pointers ".." we must unlock the
         * parent directory before getting the requested directory.
         * There is a potential race condition here if both the current
         * and parent directories are removed before the lock for the
         * node associated with ".." returns.  We hope that this occurs
         * infrequently since we cannot avoid this race condition without
         * implementing a sophisticated deadlock detection algorithm.
         * Note also that this simple deadlock detection scheme will not
         * work if the file system has any hard links other than ".."
         * that point backwards in the directory structure.
         */
        if ((flags & ISDOTDOT) == 0 && dir_node == node) {
                if (*result_vnode) {
                        vnode_put(*result_vnode);
                        *result_vnode = NULL;
                }
                if ( (error = vnode_get(dir_vnode)) ) {
                        return (error);
                }
                *result_vnode = dir_vnode;
        }
        return (0);

drop_ref:
        if (*result_vnode) {
                vnode_put(*result_vnode);
                *result_vnode = NULL;
        }
        return (error);
}

static int
devfs_getattr(struct vnop_getattr_args *ap)
        /*struct vnop_getattr_args {
                struct vnode *a_vp;
                struct vnode_attr *a_vap;
                kauth_cred_t a_cred;
                struct proc *a_p;
        } */ 
{
        struct vnode *vp = ap->a_vp;
        struct vnode_attr *vap = ap->a_vap;
        devnode_t *     file_node;
        struct timeval now;

        file_node = VTODN(vp);

        DEVFS_LOCK();

        microtime(&now);
        dn_times(file_node, &now, &now, &now);

        VATTR_RETURN(vap, va_mode, file_node->dn_mode);

        switch (file_node->dn_type)
        {
        case    DEV_DIR:
                VATTR_RETURN(vap, va_rdev,  (dev_t)file_node->dn_dvm);
                vap->va_mode |= (S_IFDIR);
                break;
        case    DEV_CDEV:
                VATTR_RETURN(vap, va_rdev, file_node->dn_typeinfo.dev);
                vap->va_mode |= (S_IFCHR);
                break;
        case    DEV_BDEV:
                VATTR_RETURN(vap, va_rdev, file_node->dn_typeinfo.dev);
                vap->va_mode |= (S_IFBLK);
                break;
        case    DEV_SLNK:
                VATTR_RETURN(vap, va_rdev, 0);
                vap->va_mode |= (S_IFLNK);
                break;
        default:
                VATTR_RETURN(vap, va_rdev, 0);  /* default value only */
        }
        VATTR_RETURN(vap, va_type, vp->v_type);
        VATTR_RETURN(vap, va_nlink, file_node->dn_links);
        VATTR_RETURN(vap, va_uid, file_node->dn_uid);
        VATTR_RETURN(vap, va_gid, file_node->dn_gid);
        VATTR_RETURN(vap, va_fsid, (uintptr_t)file_node->dn_dvm);
        VATTR_RETURN(vap, va_fileid, (uintptr_t)file_node);
        VATTR_RETURN(vap, va_data_size, file_node->dn_len);

        /* return an override block size (advisory) */
        if (vp->v_type == VBLK)
                VATTR_RETURN(vap, va_iosize, BLKDEV_IOSIZE);
        else if (vp->v_type == VCHR)
                VATTR_RETURN(vap, va_iosize, MAXPHYSIO);
        else
                VATTR_RETURN(vap, va_iosize, vp->v_mount->mnt_vfsstat.f_iosize);
        /* if the time is bogus, set it to the boot time */
        if (file_node->dn_ctime.tv_sec == 0) {
                file_node->dn_ctime.tv_sec = boottime_sec();
                file_node->dn_ctime.tv_nsec = 0;
        }
        if (file_node->dn_mtime.tv_sec == 0)
            file_node->dn_mtime = file_node->dn_ctime;
        if (file_node->dn_atime.tv_sec == 0)
            file_node->dn_atime = file_node->dn_ctime;
        VATTR_RETURN(vap, va_change_time, file_node->dn_ctime);
        VATTR_RETURN(vap, va_modify_time, file_node->dn_mtime);
        VATTR_RETURN(vap, va_access_time, file_node->dn_atime);
        VATTR_RETURN(vap, va_gen, 0);
        VATTR_RETURN(vap, va_flags, 0);
        VATTR_RETURN(vap, va_filerev, 0);
        VATTR_RETURN(vap, va_acl, NULL);

        DEVFS_UNLOCK();

        return 0;
}

static int
devfs_setattr(struct vnop_setattr_args *ap)
        /*struct vnop_setattr_args  {
          struct vnode *a_vp;
          struct vnode_attr *a_vap;
          vfs_context_t a_context;
          } */ 
{
        struct vnode *vp = ap->a_vp;
        struct vnode_attr *vap = ap->a_vap;
        kauth_cred_t cred = vfs_context_ucred(ap->a_context);
        struct proc *p = vfs_context_proc(ap->a_context);
        int error = 0;
        devnode_t *     file_node;
        struct timeval atimeval, mtimeval;
  
        file_node = VTODN(vp);
  
        DEVFS_LOCK();
        /*
         * Go through the fields and update if set.
         */
        if (VATTR_IS_ACTIVE(vap, va_access_time) || VATTR_IS_ACTIVE(vap, va_modify_time)) {
  
  
                if (VATTR_IS_ACTIVE(vap, va_access_time))
                        file_node->dn_access = 1;
                if (VATTR_IS_ACTIVE(vap, va_modify_time)) {
                        file_node->dn_change = 1;
                        file_node->dn_update = 1;
                }
                atimeval.tv_sec = vap->va_access_time.tv_sec;
                atimeval.tv_usec = vap->va_access_time.tv_nsec / 1000;
                mtimeval.tv_sec = vap->va_modify_time.tv_sec;
                mtimeval.tv_usec = vap->va_modify_time.tv_nsec / 1000;
  
                if ( (error = devfs_update(vp, &atimeval, &mtimeval)) )
                        goto exit;
        }
        VATTR_SET_SUPPORTED(vap, va_access_time);
        VATTR_SET_SUPPORTED(vap, va_change_time);
  
        /*
         * Change the permissions.
         */
        if (VATTR_IS_ACTIVE(vap, va_mode)) {
                file_node->dn_mode &= ~07777;
                file_node->dn_mode |= vap->va_mode & 07777;
        }
        VATTR_SET_SUPPORTED(vap, va_mode);
  
        /*
         * Change the owner.
         */
        if (VATTR_IS_ACTIVE(vap, va_uid))
                file_node->dn_uid = vap->va_uid;
        VATTR_SET_SUPPORTED(vap, va_uid);
  
        /*
         * Change the group.
         */
        if (VATTR_IS_ACTIVE(vap, va_gid))
                file_node->dn_gid = vap->va_gid;
        VATTR_SET_SUPPORTED(vap, va_gid);
        exit:
        DEVFS_UNLOCK();

        return error;
}

static int
devfs_read(struct vnop_read_args *ap)
        /* struct vnop_read_args {
                struct vnode *a_vp;
                struct uio *a_uio;
                int  a_ioflag;
                vfs_context_t a_context;
        } */
{
        devnode_t * dn_p = VTODN(ap->a_vp);

        switch (ap->a_vp->v_type) {
          case VDIR: {
              dn_p->dn_access = 1;

              return VNOP_READDIR(ap->a_vp, ap->a_uio, 0, NULL, NULL, ap->a_context);
          }
          default: {
              printf("devfs_read(): bad file type %d", ap->a_vp->v_type);
              return(EINVAL);
              break;
          }
        }
        return (0); /* not reached */
}

static int
devfs_close(struct vnop_close_args *ap)
        /* struct vnop_close_args {
                struct vnode *a_vp;
                int  a_fflag;
                vfs_context_t a_context;
        } */
{
        struct vnode *          vp = ap->a_vp;
        register devnode_t *    dnp = VTODN(vp);
        struct timeval now;

        if (vnode_isinuse(vp, 1)) {
            DEVFS_LOCK();
            microtime(&now);
            dn_times(dnp, &now, &now, &now);
            DEVFS_UNLOCK();
        }
        return (0);
}

static int
devfsspec_close(struct vnop_close_args *ap)
        /* struct vnop_close_args {
                struct vnode *a_vp;
                int  a_fflag;
                vfs_context_t a_context;
        } */
{
        struct vnode *          vp = ap->a_vp;
        register devnode_t *    dnp = VTODN(vp);
        struct timeval now;

        if (vnode_isinuse(vp, 1)) {
            DEVFS_LOCK();
            microtime(&now);
            dn_times(dnp, &now, &now, &now);
            DEVFS_UNLOCK();
        }
        return (VOCALL (spec_vnodeop_p, VOFFSET(vnop_close), ap));
}

static int
devfsspec_read(struct vnop_read_args *ap)
        /* struct vnop_read_args {
                struct vnode *a_vp;
                struct uio *a_uio;
                int  a_ioflag;
                kauth_cred_t a_cred;
        } */
{
        register devnode_t *    dnp = VTODN(ap->a_vp);

        dnp->dn_access = 1;

        return (VOCALL (spec_vnodeop_p, VOFFSET(vnop_read), ap));
}

static int
devfsspec_write(struct vnop_write_args *ap)
        /* struct vnop_write_args  {
                struct vnode *a_vp;
                struct uio *a_uio;
                int  a_ioflag;
                vfs_context_t a_context;
        } */
{
        register devnode_t *    dnp = VTODN(ap->a_vp);

        dnp->dn_change = 1;
        dnp->dn_update = 1;

        return (VOCALL (spec_vnodeop_p, VOFFSET(vnop_write), ap));
}

/*
 *  Write data to a file or directory.
 */
static int
devfs_write(struct vnop_write_args *ap)
        /* struct vnop_write_args  {
                struct vnode *a_vp;
                struct uio *a_uio;
                int  a_ioflag;
                kauth_cred_t a_cred;
        } */
{
        switch (ap->a_vp->v_type) {
        case VDIR:
                return(EISDIR);
        default:
                printf("devfs_write(): bad file type %d", ap->a_vp->v_type);
                return (EINVAL);
        }
        return 0; /* not reached */
}

static int
devfs_remove(struct vnop_remove_args *ap)
        /* struct vnop_remove_args  {
                struct vnode *a_dvp;
                struct vnode *a_vp;
                struct componentname *a_cnp;
        } */ 
{
        struct vnode *vp = ap->a_vp;
        struct vnode *dvp = ap->a_dvp;
        struct componentname *cnp = ap->a_cnp;
        vfs_context_t ctx = cnp->cn_context;
        devnode_t *  tp;
        devnode_t *  tdp;
        devdirent_t * tnp;
        int doingdirectory = 0;
        int error = 0;
        uid_t ouruid = kauth_cred_getuid(vfs_context_ucred(ctx));

        /*
         * assume that the name is null terminated as they
         * are the end of the path. Get pointers to all our
         * devfs structures.
         */
        tp = VTODN(vp);
        tdp = VTODN(dvp);

        DEVFS_LOCK();

        tnp = dev_findname(tdp, cnp->cn_nameptr);

        if (tnp == NULL) {
                error = ENOENT;
                goto abort;
        }

        /*
         * Make sure that we don't try do something stupid
         */
        if ((tp->dn_type) == DEV_DIR) {
                /*
                 * Avoid ".", "..", and aliases of "." for obvious reasons.
                 */
                if ( (cnp->cn_namelen == 1 && cnp->cn_nameptr[0] == '.') 
                    || (cnp->cn_flags&ISDOTDOT) ) {
                        error = EINVAL;
                        goto abort;
                }
                doingdirectory++;
        }

        /***********************************
         * Start actually doing things.... *
         ***********************************/
        tdp->dn_change = 1;
        tdp->dn_update = 1;

        /*
         * Target must be empty if a directory and have no links
         * to it. Also, ensure source and target are compatible
         * (both directories, or both not directories).
         */
        if (( doingdirectory) && (tp->dn_links > 2)) {
            error = ENOTEMPTY;
            goto abort;
        }
        dev_free_name(tnp);
abort:
        DEVFS_UNLOCK();

        return (error);
}

/*
 */
static int
devfs_link(struct vnop_link_args *ap)
        /*struct vnop_link_args  {
                struct vnode *a_tdvp;
                struct vnode *a_vp;
                struct componentname *a_cnp;
                vfs_context_t a_context;
        } */ 
{
        struct vnode *vp = ap->a_vp;
        struct vnode *tdvp = ap->a_tdvp;
        struct componentname *cnp = ap->a_cnp;
        devnode_t * fp;
        devnode_t * tdp;
        devdirent_t * tnp;
        int error = 0;
        struct timeval now;

        /*
         * First catch an arbitrary restriction for this FS
         */
        if (cnp->cn_namelen > DEVMAXNAMESIZE) {
                error = ENAMETOOLONG;
                goto out1;
        }

        /*
         * Lock our directories and get our name pointers
         * assume that the names are null terminated as they
         * are the end of the path. Get pointers to all our
         * devfs structures.
         */
        tdp = VTODN(tdvp);
        fp = VTODN(vp);
        
        if (tdvp->v_mount != vp->v_mount) {
                return (EXDEV);
        }
        DEVFS_LOCK();


        /***********************************
         * Start actually doing things.... *
         ***********************************/
        fp->dn_change = 1;

        microtime(&now);
        error = devfs_update(vp, &now, &now);

        if (!error) {
            error = dev_add_name(cnp->cn_nameptr, tdp, NULL, fp, &tnp);
        }
out1:
        DEVFS_UNLOCK();

        return (error);
}

/*
 * Rename system call. Seems overly complicated to me...
 *      rename("foo", "bar");
 * is essentially
 *      unlink("bar");
 *      link("foo", "bar");
 *      unlink("foo");
 * but ``atomically''.
 *
 * When the target exists, both the directory
 * and target vnodes are locked.
 * the source and source-parent vnodes are referenced
 *
 *
 * Basic algorithm is:
 *
 * 1) Bump link count on source while we're linking it to the
 *    target.  This also ensure the inode won't be deleted out
 *    from underneath us while we work (it may be truncated by
 *    a concurrent `trunc' or `open' for creation).
 * 2) Link source to destination.  If destination already exists,
 *    delete it first.
 * 3) Unlink source reference to node if still around. If a
 *    directory was moved and the parent of the destination
 *    is different from the source, patch the ".." entry in the
 *    directory.
 */
static int
devfs_rename(struct vnop_rename_args *ap)
        /*struct vnop_rename_args  {
                struct vnode *a_fdvp; 
                struct vnode *a_fvp;  
                struct componentname *a_fcnp;
                struct vnode *a_tdvp;
                struct vnode *a_tvp;
                struct componentname *a_tcnp;
                vfs_context_t a_context;
        } */
{
        struct vnode *tvp = ap->a_tvp;
        struct vnode *tdvp = ap->a_tdvp;
        struct vnode *fvp = ap->a_fvp;
        struct vnode *fdvp = ap->a_fdvp;
        struct componentname *tcnp = ap->a_tcnp;
        struct componentname *fcnp = ap->a_fcnp;
        devnode_t *fp, *fdp, *tp, *tdp;
        devdirent_t *fnp,*tnp;
        int doingdirectory = 0;
        int error = 0;
        struct timeval now;

        DEVFS_LOCK();
        /*
         * First catch an arbitrary restriction for this FS
         */
        if (tcnp->cn_namelen > DEVMAXNAMESIZE) {
                error = ENAMETOOLONG;
                goto out;
        }

        /*
         * assume that the names are null terminated as they
         * are the end of the path. Get pointers to all our
         * devfs structures.
         */
        tdp = VTODN(tdvp);
        fdp = VTODN(fdvp);
        fp = VTODN(fvp);

        fnp = dev_findname(fdp, fcnp->cn_nameptr);

        if (fnp == NULL) {
                error = ENOENT;
                goto out;
        }
        tp = NULL;
        tnp = NULL;

        if (tvp) {
                tnp = dev_findname(tdp, tcnp->cn_nameptr);

                if (tnp == NULL) {
                        error = ENOENT;
                        goto out;
                }
                tp = VTODN(tvp);
        }
        
        /*
         * Make sure that we don't try do something stupid
         */
        if ((fp->dn_type) == DEV_DIR) {
                /*
                 * Avoid ".", "..", and aliases of "." for obvious reasons.
                 */
                if ((fcnp->cn_namelen == 1 && fcnp->cn_nameptr[0] == '.') 
                    || (fcnp->cn_flags&ISDOTDOT) 
                    || (tcnp->cn_namelen == 1 && tcnp->cn_nameptr[0] == '.') 
                    || (tcnp->cn_flags&ISDOTDOT) 
                    || (tdp == fp )) {
                        error = EINVAL;
                        goto out;
                }
                doingdirectory++;
        }

        /*
         * If ".." must be changed (ie the directory gets a new
         * parent) then the source directory must not be in the
         * directory hierarchy above the target, as this would
         * orphan everything below the source directory. Also
         * the user must have write permission in the source so
         * as to be able to change "..". 
         */
        if (doingdirectory && (tdp != fdp)) {
                devnode_t * tmp, *ntmp;
                tmp = tdp;
                do {
                        if(tmp == fp) {
                                /* XXX unlock stuff here probably */
                                error = EINVAL;
                                goto out;
                        }
                        ntmp = tmp;
                } while ((tmp = tmp->dn_typeinfo.Dir.parent) != ntmp);
        }

        /***********************************
         * Start actually doing things.... *
         ***********************************/
        fp->dn_change = 1;
        microtime(&now);

        if ( (error = devfs_update(fvp, &now, &now)) ) {
            goto out;
        }
        /*
         * Check if just deleting a link name.
         */
        if (fvp == tvp) {
                if (fvp->v_type == VDIR) {
                        error = EINVAL;
                        goto out;
                }
                /* Release destination completely. */
                dev_free_name(fnp);

                DEVFS_UNLOCK();
                return 0;
        }
        /*
         * 1) Bump link count while we're moving stuff
         *    around.  If we crash somewhere before
         *    completing our work,  too bad :)
         */
        fp->dn_links++;
        /*
         * If the target exists zap it (unless it's a non-empty directory)
         * We could do that as well but won't
         */
        if (tp) {
                int ouruid = kauth_cred_getuid(vfs_context_ucred(tcnp->cn_context));
                /*
                 * Target must be empty if a directory and have no links
                 * to it. Also, ensure source and target are compatible
                 * (both directories, or both not directories).
                 */
                if (( doingdirectory) && (tp->dn_links > 2)) {
                        error = ENOTEMPTY;
                        goto bad;
                }
                dev_free_name(tnp);
                tp = NULL;
        }
        dev_add_name(tcnp->cn_nameptr,tdp,NULL,fp,&tnp);
        fnp->de_dnp = NULL;
        fp->dn_links--; /* one less link to it.. */

        dev_free_name(fnp);
bad:
        fp->dn_links--; /* we added one earlier*/
out:
        DEVFS_UNLOCK();
        return (error);
}

static int
devfs_symlink(struct vnop_symlink_args *ap)
        /*struct vnop_symlink_args {
                struct vnode *a_dvp;
                struct vnode **a_vpp;
                struct componentname *a_cnp;
                struct vnode_attr *a_vap;
                char *a_target;
                vfs_context_t a_context;
        } */
{
        struct componentname * cnp = ap->a_cnp;
        vfs_context_t ctx = cnp->cn_context;
        struct proc *p = vfs_context_proc(ctx);
        int error = 0;
        devnode_t * dir_p;
        devnode_type_t typeinfo;
        devdirent_t * nm_p;
        devnode_t * dev_p;
        struct vnode_attr *     vap = ap->a_vap;
        struct vnode * * vpp = ap->a_vpp;

        dir_p = VTODN(ap->a_dvp);
        typeinfo.Slnk.name = ap->a_target;
        typeinfo.Slnk.namelen = strlen(ap->a_target);

        DEVFS_LOCK();
        error = dev_add_entry(cnp->cn_nameptr, dir_p, DEV_SLNK, 
                              &typeinfo, NULL, NULL, &nm_p);
        if (error) {
            goto failure;
        }
        dev_p = nm_p->de_dnp;
        dev_p->dn_uid = dir_p->dn_uid;
        dev_p->dn_gid = dir_p->dn_gid;
        dev_p->dn_mode = vap->va_mode;
        dn_copy_times(dev_p, dir_p);

        error = devfs_dntovn(dev_p, vpp, p);
failure:
        DEVFS_UNLOCK();

        return error;
}

/*
 * Mknod vnode call
 */
static int
devfs_mknod(struct vnop_mknod_args *ap)
        /* struct vnop_mknod_args {
                struct vnode *a_dvp;
                struct vnode **a_vpp;
                struct componentname *a_cnp;
                struct vnode_attr *a_vap;
                vfs_context_t a_context;
        } */
{
        struct componentname * cnp = ap->a_cnp;
        vfs_context_t ctx = cnp->cn_context;
        struct proc *p = vfs_context_proc(ctx);
        devnode_t *     dev_p;
        devdirent_t *   devent;
        devnode_t *     dir_p;  /* devnode for parent directory */
        struct vnode *  dvp = ap->a_dvp;
        int             error = 0;
        devnode_type_t  typeinfo;
        struct vnode_attr *     vap = ap->a_vap;
        struct vnode ** vpp = ap->a_vpp;

        *vpp = NULL;
        if (!(vap->va_type == VBLK) && !(vap->va_type == VCHR)) {
                return (EINVAL); /* only support mknod of special files */
        }
        dir_p = VTODN(dvp);
        typeinfo.dev = vap->va_rdev;

        DEVFS_LOCK();
        error = dev_add_entry(cnp->cn_nameptr, dir_p, 
                              (vap->va_type == VBLK) ? DEV_BDEV : DEV_CDEV,
                              &typeinfo, NULL, NULL, &devent);
        if (error) {
                goto failure;
        }
        dev_p = devent->de_dnp;
        error = devfs_dntovn(dev_p, vpp, p);
        if (error)
                goto failure;
        dev_p->dn_uid = vap->va_uid;
        dev_p->dn_gid = vap->va_gid;
        dev_p->dn_mode = vap->va_mode;
        VATTR_SET_SUPPORTED(vap, va_uid);
        VATTR_SET_SUPPORTED(vap, va_gid);
        VATTR_SET_SUPPORTED(vap, va_mode);
failure:
        DEVFS_UNLOCK();

        return (error);
}

/*
 * Vnode op for readdir
 */
static int
devfs_readdir(struct vnop_readdir_args *ap)
        /*struct vnop_readdir_args {
                struct vnode *a_vp;
                struct uio *a_uio;
                int a_flags;
                int *a_eofflag;
                int *a_numdirent;
                vfs_context_t a_context;
        } */
{
        struct vnode *vp = ap->a_vp;
        struct uio *uio = ap->a_uio;
        struct dirent dirent;
        devnode_t * dir_node;
        devdirent_t *   name_node;
        char    *name;
        int error = 0;
        int reclen;
        int nodenumber;
        int     startpos,pos;

        if (ap->a_flags & (VNODE_READDIR_EXTENDED | VNODE_READDIR_REQSEEKOFF))
                return (EINVAL);

        /*  set up refs to dir */
        dir_node = VTODN(vp);
        if (dir_node->dn_type != DEV_DIR)
                return(ENOTDIR);
        pos = 0;
        startpos = uio->uio_offset;

        DEVFS_LOCK();

        name_node = dir_node->dn_typeinfo.Dir.dirlist;
        nodenumber = 0;

        dir_node->dn_access = 1;

        while ((name_node || (nodenumber < 2)) && (uio_resid(uio) > 0))
        {
                switch(nodenumber)
                {
                case    0:
                        dirent.d_fileno = (int32_t)(void *)dir_node;
                        name = ".";
                        dirent.d_namlen = 1;
                        dirent.d_type = DT_DIR;
                        break;
                case    1:
                        if(dir_node->dn_typeinfo.Dir.parent)
                            dirent.d_fileno
                                = (int32_t)dir_node->dn_typeinfo.Dir.parent;
                        else
                                dirent.d_fileno = (u_int32_t)dir_node;
                        name = "..";
                        dirent.d_namlen = 2;
                        dirent.d_type = DT_DIR;
                        break;
                default:
                        dirent.d_fileno = (int32_t)(void *)name_node->de_dnp;
                        dirent.d_namlen = strlen(name_node->de_name);
                        name = name_node->de_name;
                        switch(name_node->de_dnp->dn_type) {
                        case DEV_BDEV:
                                dirent.d_type = DT_BLK;
                                break;
                        case DEV_CDEV:
                                dirent.d_type = DT_CHR;
                                break;
                        case DEV_DIR:
                                dirent.d_type = DT_DIR;
                                break;
                        case DEV_SLNK:
                                dirent.d_type = DT_LNK;
                                break;
                        default:
                                dirent.d_type = DT_UNKNOWN;
                        }
                }
#define GENERIC_DIRSIZ(dp) \
    ((sizeof (struct dirent) - (MAXNAMLEN+1)) + (((dp)->d_namlen+1 + 3) &~ 3))

                reclen = dirent.d_reclen = GENERIC_DIRSIZ(&dirent);

                if(pos >= startpos)     /* made it to the offset yet? */
                {
                        if (uio_resid(uio) < reclen) /* will it fit? */
                                break;
                        strcpy( dirent.d_name,name);
                        if ((error = uiomove ((caddr_t)&dirent,
                                        dirent.d_reclen, uio)) != 0)
                                break;
                }
                pos += reclen;
                if((nodenumber >1) && name_node)
                        name_node = name_node->de_next;
                nodenumber++;
        }
        DEVFS_UNLOCK();
        uio->uio_offset = pos;

        return (error);
}


/*
 */
static int
devfs_readlink(struct vnop_readlink_args *ap)
        /*struct vnop_readlink_args {
                struct vnode *a_vp;
                struct uio *a_uio;
                vfs_context_t a_context;
        } */
{
        struct vnode *vp = ap->a_vp;
        struct uio *uio = ap->a_uio;
        devnode_t * lnk_node;
        int error = 0;

        /*  set up refs to dir */
        lnk_node = VTODN(vp);

        if (lnk_node->dn_type != DEV_SLNK) {
                error = EINVAL;
                goto out;
        }
        error = uiomove(lnk_node->dn_typeinfo.Slnk.name, 
                        lnk_node->dn_typeinfo.Slnk.namelen, uio);
out:    
        return error;
}

static int
devfs_reclaim(struct vnop_reclaim_args *ap)
        /*struct vnop_reclaim_args {
                struct vnode *a_vp;
        } */
{
    struct vnode *      vp = ap->a_vp;
    devnode_t *         dnp = VTODN(vp);
    
    DEVFS_LOCK();

    if (dnp) {
        /* 
         * do the same as devfs_inactive in case it is not called
         * before us (can that ever happen?)
         */
        dnp->dn_vn = NULL;
        vp->v_data = NULL;

        if (dnp->dn_delete) {
            devnode_free(dnp);
        }
    }
    DEVFS_UNLOCK();

    return(0);
}


/*
 * Get configurable pathname variables.
 */
static int
devs_vnop_pathconf(
        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:
                /* arbitrary limit matching HFS; devfs has no hard limit */
                *ap->a_retval = 32767;
                break;
        case _PC_NAME_MAX:
                *ap->a_retval = DEVMAXNAMESIZE - 1;     /* includes NUL */
                break;
        case _PC_PATH_MAX:
                *ap->a_retval = DEVMAXPATHSIZE - 1;     /* XXX nonconformant */
                break;
        case _PC_CHOWN_RESTRICTED:
                *ap->a_retval = 1;
                break;
        case _PC_NO_TRUNC:
                *ap->a_retval = 0;
                break;
        case _PC_CASE_SENSITIVE:
                *ap->a_retval = 1;
                break;
        case _PC_CASE_PRESERVING:
                *ap->a_retval = 1;
                break;
        default:
                return (EINVAL);
        }

        return (0);
}



/**************************************************************************\
* pseudo ops *
\**************************************************************************/

/*
 *
 *      struct vnop_inactive_args {
 *              struct vnode *a_vp;
 *              vfs_context_t a_context;
 *      } 
 */

static int
devfs_inactive(__unused struct vnop_inactive_args *ap)
{
    return (0);
}

/*
 * called with DEVFS_LOCK held
 */
static int
devfs_update(struct vnode *vp, struct timeval *access, struct timeval *modify)
{
        devnode_t * ip;
        struct timeval now;

        ip = VTODN(vp);
        if (vp->v_mount->mnt_flag & MNT_RDONLY) {
                ip->dn_access = 0;
                ip->dn_change = 0;
                ip->dn_update = 0;

                return (0);
        }
        microtime(&now);
        dn_times(ip, access, modify, &now);

        return (0);
}

#define VOPFUNC int (*)(void *)

/* The following ops are used by directories and symlinks */
int (**devfs_vnodeop_p)(void *);
static struct vnodeopv_entry_desc devfs_vnodeop_entries[] = {
        { &vnop_default_desc, (VOPFUNC)vn_default_error },
        { &vnop_lookup_desc, (VOPFUNC)devfs_lookup },           /* lookup */
        { &vnop_create_desc, (VOPFUNC)err_create },             /* create */
        { &vnop_whiteout_desc, (VOPFUNC)err_whiteout },         /* whiteout */
        { &vnop_mknod_desc, (VOPFUNC)devfs_mknod },             /* mknod */
        { &vnop_open_desc, (VOPFUNC)nop_open },                 /* open */
        { &vnop_close_desc, (VOPFUNC)devfs_close },             /* close */
        { &vnop_getattr_desc, (VOPFUNC)devfs_getattr },         /* getattr */
        { &vnop_setattr_desc, (VOPFUNC)devfs_setattr },         /* setattr */
        { &vnop_read_desc, (VOPFUNC)devfs_read },               /* read */
        { &vnop_write_desc, (VOPFUNC)devfs_write },             /* write */
        { &vnop_ioctl_desc, (VOPFUNC)err_ioctl },               /* ioctl */
        { &vnop_select_desc, (VOPFUNC)err_select },             /* select */
        { &vnop_revoke_desc, (VOPFUNC)err_revoke },             /* revoke */
        { &vnop_mmap_desc, (VOPFUNC)err_mmap },                 /* mmap */
        { &vnop_fsync_desc, (VOPFUNC)nop_fsync },               /* fsync */
        { &vnop_remove_desc, (VOPFUNC)devfs_remove },           /* remove */
        { &vnop_link_desc, (VOPFUNC)devfs_link },               /* link */
        { &vnop_rename_desc, (VOPFUNC)devfs_rename },           /* rename */
        { &vnop_mkdir_desc, (VOPFUNC)err_mkdir },               /* mkdir */
        { &vnop_rmdir_desc, (VOPFUNC)err_rmdir },               /* rmdir */
        { &vnop_symlink_desc, (VOPFUNC)devfs_symlink },         /* symlink */
        { &vnop_readdir_desc, (VOPFUNC)devfs_readdir },         /* readdir */
        { &vnop_readlink_desc, (VOPFUNC)devfs_readlink },       /* readlink */
        { &vnop_inactive_desc, (VOPFUNC)devfs_inactive },       /* inactive */
        { &vnop_reclaim_desc, (VOPFUNC)devfs_reclaim },         /* reclaim */
        { &vnop_strategy_desc, (VOPFUNC)err_strategy },         /* strategy */
        { &vnop_pathconf_desc, (VOPFUNC)devs_vnop_pathconf },   /* pathconf */
        { &vnop_advlock_desc, (VOPFUNC)err_advlock },           /* advlock */
        { &vnop_bwrite_desc, (VOPFUNC)err_bwrite },
        { &vnop_pagein_desc, (VOPFUNC)err_pagein },             /* Pagein */
        { &vnop_pageout_desc, (VOPFUNC)err_pageout },           /* Pageout */
        { &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 }
};
struct vnodeopv_desc devfs_vnodeop_opv_desc =
        { &devfs_vnodeop_p, devfs_vnodeop_entries };

/* The following ops are used by the device nodes */
int (**devfs_spec_vnodeop_p)(void *);
static struct vnodeopv_entry_desc devfs_spec_vnodeop_entries[] = {
        { &vnop_default_desc, (VOPFUNC)vn_default_error },
        { &vnop_lookup_desc, (VOPFUNC)spec_lookup },            /* lookup */
        { &vnop_create_desc, (VOPFUNC)spec_create },            /* create */
        { &vnop_mknod_desc, (VOPFUNC)spec_mknod },              /* mknod */
        { &vnop_open_desc, (VOPFUNC)spec_open },                        /* open */
        { &vnop_close_desc, (VOPFUNC)devfsspec_close },         /* close */
        { &vnop_getattr_desc, (VOPFUNC)devfs_getattr },         /* getattr */
        { &vnop_setattr_desc, (VOPFUNC)devfs_setattr },         /* setattr */
        { &vnop_read_desc, (VOPFUNC)devfsspec_read },           /* read */
        { &vnop_write_desc, (VOPFUNC)devfsspec_write },         /* write */
        { &vnop_ioctl_desc, (VOPFUNC)spec_ioctl },              /* ioctl */
        { &vnop_select_desc, (VOPFUNC)spec_select },            /* select */
        { &vnop_revoke_desc, (VOPFUNC)spec_revoke },            /* revoke */
        { &vnop_mmap_desc, (VOPFUNC)spec_mmap },                        /* mmap */
        { &vnop_fsync_desc, (VOPFUNC)spec_fsync },              /* fsync */
        { &vnop_remove_desc, (VOPFUNC)devfs_remove },           /* remove */
        { &vnop_link_desc, (VOPFUNC)devfs_link },               /* link */
        { &vnop_rename_desc, (VOPFUNC)spec_rename },            /* rename */
        { &vnop_mkdir_desc, (VOPFUNC)spec_mkdir },              /* mkdir */
        { &vnop_rmdir_desc, (VOPFUNC)spec_rmdir },              /* rmdir */
        { &vnop_symlink_desc, (VOPFUNC)spec_symlink },          /* symlink */
        { &vnop_readdir_desc, (VOPFUNC)spec_readdir },          /* readdir */
        { &vnop_readlink_desc, (VOPFUNC)spec_readlink },                /* readlink */
        { &vnop_inactive_desc, (VOPFUNC)devfs_inactive },       /* inactive */
        { &vnop_reclaim_desc, (VOPFUNC)devfs_reclaim },         /* reclaim */
        { &vnop_strategy_desc, (VOPFUNC)spec_strategy },                /* strategy */
        { &vnop_pathconf_desc, (VOPFUNC)spec_pathconf },                /* pathconf */
        { &vnop_advlock_desc, (VOPFUNC)spec_advlock },          /* advlock */
        { &vnop_bwrite_desc, (VOPFUNC)vn_bwrite },
        { &vnop_devblocksize_desc, (VOPFUNC)spec_devblocksize },        /* devblocksize */
        { &vnop_pagein_desc, (VOPFUNC)err_pagein },             /* Pagein */
        { &vnop_pageout_desc, (VOPFUNC)err_pageout },           /* Pageout */
        { &vnop_copyfile_desc, (VOPFUNC)err_copyfile },         /* Copyfile */
        { &vnop_blktooff_desc, (VOPFUNC)spec_blktooff },        /* blktooff */
        { &vnop_blktooff_desc, (VOPFUNC)spec_offtoblk  },       /* blkofftoblk */
        { &vnop_blockmap_desc, (VOPFUNC)spec_blockmap },        /* blockmap */
        { (struct vnodeop_desc*)NULL, (int(*)())NULL }
};
struct vnodeopv_desc devfs_spec_vnodeop_opv_desc =
        { &devfs_spec_vnodeop_p, devfs_spec_vnodeop_entries };