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/dl.h>
  21 #include <grub/misc.h>
  22 #include <grub/file.h>
  23 #include <grub/disk.h>
  24 #include <grub/mm.h>
  25 #include <grub/extcmd.h>
  26
  27 struct grub_loopback
  28 {
  29   char *devname;
  30   char *filename;
  31   int has_partitions;
  32   struct grub_loopback *next;
  33 };
  34
  35 static struct grub_loopback *loopback_list;
  36
  37 static const struct grub_arg_option options[] =
  38   {
  39     {"delete", 'd', 0, "delete the loopback device entry", 0, 0},
  40     {"partitions", 'p', 0, "simulate a hard drive with partitions", 0, 0},
  41     {0, 0, 0, 0, 0, 0}
  42   };
  43
  44 /* Delete the loopback device NAME.  */
  45 static grub_err_t
  46 delete_loopback (const char *name)
  47 {
  48   struct grub_loopback *dev;
  49   struct grub_loopback **prev;
  50
  51   /* Search for the device.  */
  52   for (dev = loopback_list, prev = &loopback_list;
  53        dev;
  54        prev = &dev->next, dev = dev->next)
  55     if (grub_strcmp (dev->devname, name) == 0)
  56       break;
  57
  58   if (! dev)
  59     return grub_error (GRUB_ERR_BAD_DEVICE, "Device not found");
  60
  61   /* Remove the device from the list.  */
  62   *prev = dev->next;
  63
  64   grub_free (dev->devname);
  65   grub_free (dev->filename);
  66   grub_free (dev);
  67
  68   return 0;
  69 }
  70
  71 /* The command to add and remove loopback devices.  */
  72 static grub_err_t
  73 grub_cmd_loopback (grub_extcmd_t cmd, int argc, char **args)
  74 {
  75   struct grub_arg_list *state = state = cmd->state;
  76   grub_file_t file;
  77   struct grub_loopback *newdev;
  78
  79   if (argc < 1)
  80     return grub_error (GRUB_ERR_BAD_ARGUMENT, "device name required");
  81
  82   /* Check if `-d' was used.  */
  83   if (state[0].set)
  84       return delete_loopback (args[0]);
  85
  86   if (argc < 2)
  87     return grub_error (GRUB_ERR_BAD_ARGUMENT, "file name required");
  88
  89   file = grub_file_open (args[1]);
  90   if (! file)
  91     return grub_errno;
  92
  93   /* Close the file, the only reason for opening it is validation.  */
  94   grub_file_close (file);
  95
  96   /* First try to replace the old device.  */
  97   for (newdev = loopback_list; newdev; newdev = newdev->next)
  98     if (grub_strcmp (newdev->devname, args[0]) == 0)
  99       break;
 100
 101   if (newdev)
 102     {
 103       char *newname = grub_strdup (args[1]);
 104       if (! newname)
 105         return grub_errno;
 106
 107       grub_free (newdev->filename);
 108       newdev->filename = newname;
 109
 110       /* Set has_partitions when `--partitions' was used.  */
 111       newdev->has_partitions = state[1].set;
 112
 113       return 0;
 114     }
 115
 116   /* Unable to replace it, make a new entry.  */
 117   newdev = grub_malloc (sizeof (struct grub_loopback));
 118   if (! newdev)
 119     return grub_errno;
 120
 121   newdev->devname = grub_strdup (args[0]);
 122   if (! newdev->devname)
 123     {
 124       grub_free (newdev);
 125       return grub_errno;
 126     }
 127
 128   newdev->filename = grub_strdup (args[1]);
 129   if (! newdev->filename)
 130     {
 131       grub_free (newdev->devname);
 132       grub_free (newdev);
 133       return grub_errno;
 134     }
 135
 136   /* Set has_partitions when `--partitions' was used.  */
 137   newdev->has_partitions = state[1].set;
 138
 139   /* Add the new entry to the list.  */
 140   newdev->next = loopback_list;
 141   loopback_list = newdev;
 142
 143   return 0;
 144 }
 145
 146 \f
 147 static int
 148 grub_loopback_iterate (int (*hook) (const char *name))
 149 {
 150   struct grub_loopback *d;
 151   for (d = loopback_list; d; d = d->next)
 152     {
 153       if (hook (d->devname))
 154         return 1;
 155     }
 156   return 0;
 157 }
 158
 159 static grub_err_t
 160 grub_loopback_open (const char *name, grub_disk_t disk)
 161 {
 162   grub_file_t file;
 163   struct grub_loopback *dev;
 164
 165   for (dev = loopback_list; dev; dev = dev->next)
 166     if (grub_strcmp (dev->devname, name) == 0)
 167       break;
 168
 169   if (! dev)
 170     return grub_error (GRUB_ERR_UNKNOWN_DEVICE, "Can't open device");
 171
 172   file = grub_file_open (dev->filename);
 173   if (! file)
 174     return grub_errno;
 175
 176   /* Use the filesize for the disk size, round up to a complete sector.  */
 177   disk->total_sectors = ((file->size + GRUB_DISK_SECTOR_SIZE - 1)
 178                          / GRUB_DISK_SECTOR_SIZE);
 179   disk->id = (unsigned long) dev;
 180
 181   disk->has_partitions = dev->has_partitions;
 182   disk->data = file;
 183
 184   return 0;
 185 }
 186
 187 static void
 188 grub_loopback_close (grub_disk_t disk)
 189 {
 190   grub_file_t file = (grub_file_t) disk->data;
 191
 192   grub_file_close (file);
 193 }
 194
 195 static grub_err_t
 196 grub_loopback_read (grub_disk_t disk, grub_disk_addr_t sector,
 197                     grub_size_t size, char *buf)
 198 {
 199   grub_file_t file = (grub_file_t) disk->data;
 200   grub_off_t pos;
 201
 202   grub_file_seek (file, sector << GRUB_DISK_SECTOR_BITS);
 203
 204   grub_file_read (file, buf, size << GRUB_DISK_SECTOR_BITS);
 205   if (grub_errno)
 206     return grub_errno;
 207
 208   /* In case there is more data read than there is available, in case
 209      of files that are not a multiple of GRUB_DISK_SECTOR_SIZE, fill
 210      the rest with zeros.  */
 211   pos = (sector + size) << GRUB_DISK_SECTOR_BITS;
 212   if (pos > file->size)
 213     {
 214       grub_size_t amount = pos - file->size;
 215       grub_memset (buf + (size << GRUB_DISK_SECTOR_BITS) - amount, 0, amount);
 216     }
 217
 218   return 0;
 219 }
 220
 221 static grub_err_t
 222 grub_loopback_write (grub_disk_t disk __attribute ((unused)),
 223                      grub_disk_addr_t sector __attribute ((unused)),
 224                      grub_size_t size __attribute ((unused)),
 225                      const char *buf __attribute ((unused)))
 226 {
 227   return GRUB_ERR_NOT_IMPLEMENTED_YET;
 228 }
 229
 230 static struct grub_disk_dev grub_loopback_dev =
 231   {
 232     .name = "loopback",
 233     .id = GRUB_DISK_DEVICE_LOOPBACK_ID,
 234     .iterate = grub_loopback_iterate,
 235     .open = grub_loopback_open,
 236     .close = grub_loopback_close,
 237     .read = grub_loopback_read,
 238     .write = grub_loopback_write,
 239     .next = 0
 240   };
 241
 242 static grub_extcmd_t cmd;
 243
 244 GRUB_MOD_INIT(loop)
 245 {
 246   cmd = grub_register_extcmd ("loopback", grub_cmd_loopback,
 247                               GRUB_COMMAND_FLAG_BOTH,
 248                               "loopback [-d|-p] DEVICENAME FILE",
 249                               "Make a device of a file.", options);
 250   grub_disk_dev_register (&grub_loopback_dev);
 251 }
 252
 253 GRUB_MOD_FINI(loop)
 254 {
 255   grub_unregister_extcmd (cmd);
 256   grub_disk_dev_unregister (&grub_loopback_dev);
 257 }