disk/loopback.c

   1 /* loopback.c - command to add loopback devices.  */
   2 /*
   3  *  GRUB  --  GRand Unified Bootloader
   4  *  Copyright (C) 2005,2006,2007  Free Software Foundation, Inc.
   5  *
   6  *  GRUB is free software: you can redistribute it and/or modify
   7  *  it under the terms of the GNU General Public License as published by
   8  *  the Free Software Foundation, either version 3 of the License, or
   9  *  (at your option) any later version.
  10  *
  11  *  GRUB is distributed in the hope that it will be useful,
  12  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  *  GNU General Public License for more details.
  15  *
  16  *  You should have received a copy of the GNU General Public License
  17  *  along with GRUB.  If not, see <http://www.gnu.org/licenses/>.
  18  */
  19
  20 #include <grub/normal.h>
  21 #include <grub/dl.h>
  22 #include <grub/arg.h>
  23 #include <grub/misc.h>
  24 #include <grub/file.h>
  25 #include <grub/disk.h>
  26 #include <grub/mm.h>
  27
  28 struct grub_loopback
  29 {
  30   char *devname;
  31   char *filename;
  32   int has_partitions;
  33   struct grub_loopback *next;
  34 };
  35
  36 static struct grub_loopback *loopback_list;
  37
  38 static const struct grub_arg_option options[] =
  39   {
  40     {"delete", 'd', 0, "delete the loopback device entry", 0, 0},
  41     {"partitions", 'p', 0, "simulate a hard drive with partitions", 0, 0},
  42     {0, 0, 0, 0, 0, 0}
  43   };
  44
  45 /* Delete the loopback device NAME.  */
  46 static grub_err_t
  47 delete_loopback (const char *name)
  48 {
  49   struct grub_loopback *dev;
  50   struct grub_loopback **prev;
  51
  52   /* Search for the device.  */
  53   for (dev = loopback_list, prev = &loopback_list;
  54        dev;
  55        prev = &dev->next, dev = dev->next)
  56     if (grub_strcmp (dev->devname, name) == 0)
  57       break;
  58
  59   if (! dev)
  60     return grub_error (GRUB_ERR_BAD_DEVICE, "Device not found");
  61
  62   /* Remove the device from the list.  */
  63   *prev = dev->next;
  64
  65   grub_free (dev->devname);
  66   grub_free (dev->filename);
  67   grub_free (dev);
  68
  69   return 0;
  70 }
  71
  72 /* The command to add and remove loopback devices.  */
  73 static grub_err_t
  74 grub_cmd_loopback (struct grub_arg_list *state,
  75                    int argc, char **args)
  76 {
  77   grub_file_t file;
  78   struct grub_loopback *newdev;
  79
  80   if (argc < 1)
  81     return grub_error (GRUB_ERR_BAD_ARGUMENT, "device name required");
  82
  83   /* Check if `-d' was used.  */
  84   if (state[0].set)
  85       return delete_loopback (args[0]);
  86
  87   if (argc < 2)
  88     return grub_error (GRUB_ERR_BAD_ARGUMENT, "file name required");
  89
  90   file = grub_file_open (args[1]);
  91   if (! file)
  92     return grub_errno;
  93
  94   /* Close the file, the only reason for opening it is validation.  */
  95   grub_file_close (file);
  96
  97   /* First try to replace the old device.  */
  98   for (newdev = loopback_list; newdev; newdev = newdev->next)
  99     if (grub_strcmp (newdev->devname, args[0]) == 0)
 100       break;
 101
 102   if (newdev)
 103     {
 104       char *newname = grub_strdup (args[1]);
 105       if (! newname)
 106         return grub_errno;
 107
 108       grub_free (newdev->filename);
 109       newdev->filename = newname;
 110
 111       /* Set has_partitions when `--partitions' was used.  */
 112       newdev->has_partitions = state[1].set;
 113
 114       return 0;
 115     }
 116
 117   /* Unable to replace it, make a new entry.  */
 118   newdev = grub_malloc (sizeof (struct grub_loopback));
 119   if (! newdev)
 120     return grub_errno;
 121
 122   newdev->devname = grub_strdup (args[0]);
 123   if (! newdev->devname)
 124     {
 125       grub_free (newdev);
 126       return grub_errno;
 127     }
 128
 129   newdev->filename = grub_strdup (args[1]);
 130   if (! newdev->filename)
 131     {
 132       grub_free (newdev->devname);
 133       grub_free (newdev);
 134       return grub_errno;
 135     }
 136
 137   /* Set has_partitions when `--partitions' was used.  */
 138   newdev->has_partitions = state[1].set;
 139
 140   /* Add the new entry to the list.  */
 141   newdev->next = loopback_list;
 142   loopback_list = newdev;
 143
 144   return 0;
 145 }
 146
 147 \f
 148 static int
 149 grub_loopback_iterate (int (*hook) (const char *name))
 150 {
 151   struct grub_loopback *d;
 152   for (d = loopback_list; d; d = d->next)
 153     {
 154       if (hook (d->devname))
 155         return 1;
 156     }
 157   return 0;
 158 }
 159
 160 static grub_err_t
 161 grub_loopback_open (const char *name, grub_disk_t disk)
 162 {
 163   grub_file_t file;
 164   struct grub_loopback *dev;
 165
 166   for (dev = loopback_list; dev; dev = dev->next)
 167     if (grub_strcmp (dev->devname, name) == 0)
 168       break;
 169
 170   if (! dev)
 171     return grub_error (GRUB_ERR_UNKNOWN_DEVICE, "Can't open device");
 172
 173   file = grub_file_open (dev->filename);
 174   if (! file)
 175     return grub_errno;
 176
 177   /* Use the filesize for the disk size, round up to a complete sector.  */
 178   disk->total_sectors = ((file->size + GRUB_DISK_SECTOR_SIZE - 1)
 179                          / GRUB_DISK_SECTOR_SIZE);
 180   disk->id = (unsigned long) dev;
 181
 182   disk->has_partitions = dev->has_partitions;
 183   disk->data = file;
 184
 185   return 0;
 186 }
 187
 188 static void
 189 grub_loopback_close (grub_disk_t disk)
 190 {
 191   grub_file_t file = (grub_file_t) disk->data;
 192
 193   grub_file_close (file);
 194 }
 195
 196 static grub_err_t
 197 grub_loopback_read (grub_disk_t disk, grub_disk_addr_t sector,
 198                     grub_size_t size, char *buf)
 199 {
 200   grub_file_t file = (grub_file_t) disk->data;
 201   grub_off_t pos;
 202
 203   grub_file_seek (file, sector << GRUB_DISK_SECTOR_BITS);
 204
 205   grub_file_read (file, buf, size << GRUB_DISK_SECTOR_BITS);
 206   if (grub_errno)
 207     return grub_errno;
 208
 209   /* In case there is more data read than there is available, in case
 210      of files that are not a multiple of GRUB_DISK_SECTOR_SIZE, fill
 211      the rest with zeros.  */
 212   pos = (sector + size) << GRUB_DISK_SECTOR_BITS;
 213   if (pos > file->size)
 214     {
 215       grub_size_t amount = pos - file->size;
 216       grub_memset (buf + (size << GRUB_DISK_SECTOR_BITS) - amount, 0, amount);
 217     }
 218
 219   return 0;
 220 }
 221
 222 static grub_err_t
 223 grub_loopback_write (grub_disk_t disk __attribute ((unused)),
 224                      grub_disk_addr_t sector __attribute ((unused)),
 225                      grub_size_t size __attribute ((unused)),
 226                      const char *buf __attribute ((unused)))
 227 {
 228   return GRUB_ERR_NOT_IMPLEMENTED_YET;
 229 }
 230
 231 static struct grub_disk_dev grub_loopback_dev =
 232   {
 233     .name = "loopback",
 234     .id = GRUB_DISK_DEVICE_LOOPBACK_ID,
 235     .iterate = grub_loopback_iterate,
 236     .open = grub_loopback_open,
 237     .close = grub_loopback_close,
 238     .read = grub_loopback_read,
 239     .write = grub_loopback_write,
 240     .next = 0
 241   };
 242
 243 \f
 244
 245 GRUB_MOD_INIT(loop)
 246 {
 247   (void) mod;                   /* To stop warning. */
 248   grub_register_command ("loopback", grub_cmd_loopback, GRUB_COMMAND_FLAG_BOTH,
 249                          "loopback [-d|-p] DEVICENAME FILE",
 250                          "Make a device of a file.", options);
 251   grub_disk_dev_register (&grub_loopback_dev);
 252 }
 253
 254 GRUB_MOD_FINI(loop)
 255 {
 256   grub_unregister_command ("loopback");
 257   grub_disk_dev_unregister (&grub_loopback_dev);
 258 }