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