sbin/mount_null/mount_null.c

   1 /*
   2  * Copyright (c) 1992, 1993, 1994
   3  *      The Regents of the University of California.  All rights reserved.
   4  *
   5  * This code is derived from software donated to Berkeley by
   6  * Jan-Simon Pendry.
   7  *
   8  * Redistribution and use in source and binary forms, with or without
   9  * modification, are permitted provided that the following conditions
  10  * are met:
  11  * 1. Redistributions of source code must retain the above copyright
  12  *    notice, this list of conditions and the following disclaimer.
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in the
  15  *    documentation and/or other materials provided with the distribution.
  16  * 3. All advertising materials mentioning features or use of this software
  17  *    must display the following acknowledgement:
  18  *      This product includes software developed by the University of
  19  *      California, Berkeley and its contributors.
  20  * 4. Neither the name of the University nor the names of its contributors
  21  *    may be used to endorse or promote products derived from this software
  22  *    without specific prior written permission.
  23  *
  24  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  25  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  26  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  27  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  28  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  29  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  30  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  31  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  32  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  33  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  34  * SUCH DAMAGE.
  35  *
  36  * @(#) Copyright (c) 1992, 1993, 1994 The Regents of the University of California.  All rights reserved.
  37  * @(#)mount_null.c     8.6 (Berkeley) 4/26/95
  38  * $FreeBSD: src/sbin/mount_null/mount_null.c,v 1.13 1999/10/09 11:54:11 phk Exp $
  39  * $DragonFly: src/sbin/mount_null/mount_null.c,v 1.11 2008/09/18 16:08:31 dillon Exp $
  40  */
  41
  42 #include <sys/param.h>
  43 #include <sys/mount.h>
  44 #include <vfs/nullfs/null.h>
  45
  46 #include <err.h>
  47 #include <stdio.h>
  48 #include <stdlib.h>
  49 #include <string.h>
  50 #include <sysexits.h>
  51 #include <unistd.h>
  52
  53 #include "mntopts.h"
  54
  55 struct mntopt mopts[] = {
  56         MOPT_STDOPTS,
  57         MOPT_UPDATE,
  58         MOPT_NULL
  59 };
  60
  61 static void     usage(void) __dead2;
  62
  63 int
  64 main(int argc, char **argv)
  65 {
  66         struct null_args args;
  67         int ch, mntflags;
  68         char source[MAXPATHLEN];
  69         char target[MAXPATHLEN];
  70         struct vfsconf vfc;
  71         int error;
  72
  73         bzero(&args, sizeof(args));
  74         mntflags = 0;
  75         while ((ch = getopt(argc, argv, "o:u")) != -1)
  76                 switch(ch) {
  77                 case 'o':
  78                         getmntopts(optarg, mopts, &mntflags, 0);
  79                         break;
  80                 case 'u':
  81                         mntflags |= MNT_UPDATE;
  82                         break;
  83                 case '?':
  84                 default:
  85                         usage();
  86                 }
  87         argc -= optind;
  88         argv += optind;
  89
  90         /*
  91          * Resolve target and source with realpath(3).  Only the mount point
  92          * needs be specified in update mode, but mount(8) passes us two
  93          * arguments, the second of which is the source directory.
  94          */
  95         if ((mntflags & MNT_UPDATE) && argc == 1) {
  96                 args.target = NULL;
  97                 checkpath(argv[0], source);
  98         } else if (argc == 2) {
  99                 args.target = target;
 100                 checkpath(argv[0], target);
 101                 checkpath(argv[1], source);
 102         } else
 103                 usage();
 104
 105         /*
 106          * Mount points that did not use distinct paths (e.g. / on /mnt)
 107          * used to be disallowed because mount linkages were stored in
 108          * vnodes and would lead to endlessly recursive trees.  DragonFly
 109          * stores mount linkages in the namecache topology and does not
 110          * have this problem, so paths no longer need to be distinct.
 111          */
 112
 113         error = getvfsbyname("null", &vfc);
 114         if (error && vfsisloadable("null")) {
 115                 if(vfsload("null"))
 116                         err(EX_OSERR, "vfsload(null)");
 117                 endvfsent();
 118                 error = getvfsbyname("null", &vfc);
 119         }
 120         if (error)
 121                 errx(EX_OSERR, "null/loopback filesystem is not available");
 122
 123         if (mount(vfc.vfc_name, source, mntflags, &args))
 124                 err(1, NULL);
 125         exit(0);
 126 }
 127
 128 static void
 129 usage(void)
 130 {
 131         fprintf(stderr,
 132             "usage: mount_null [-o options] target_fs mount_point\n");
 133         fprintf(stderr,
 134             "       mount_null -u [-o options] mount_point\n");
 135         exit(1);
 136 }