arch/common/grub2/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, "set that the drive has partitions to"
  42      " simulate a harddrive", 0, 0},
  43     {0, 0, 0, 0, 0, 0}
  44   };
  45
  46 /* Delete the loopback device NAME.  */
  47 static grub_err_t
  48 delete_loopback (const char *name)
  49 {
  50   struct grub_loopback *dev;
  51   struct grub_loopback **prev;
  52
  53   /* Search for the device.  */
  54   for (dev = loopback_list, prev = &loopback_list;
  55        dev;
  56        prev = &dev->next, dev = dev->next)
  57     if (grub_strcmp (dev->devname, name) == 0)
  58       break;
  59
  60   if (! dev)
  61     return grub_error (GRUB_ERR_BAD_DEVICE, "Device not found");
  62
  63   /* Remove the device from the list.  */
  64   *prev = dev->next;
  65
  66   grub_free (dev->devname);
  67   grub_free (dev->filename);
  68   grub_free (dev);
  69
  70   return 0;
  71 }
  72
  73 /* The command to add and remove loopback devices.  */
  74 static grub_err_t
  75 grub_cmd_loopback (struct grub_arg_list *state,
  76                    int argc, char **args)
  77 {
  78   grub_file_t file;
  79   struct grub_loopback *newdev;
  80
  81   if (argc < 1)
  82     return grub_error (GRUB_ERR_BAD_ARGUMENT, "device name required");
  83
  84   /* Check if `-d' was used.  */
  85   if (state[0].set)
  86       return delete_loopback (args[0]);
  87
  88   if (argc < 2)
  89     return grub_error (GRUB_ERR_BAD_ARGUMENT, "file name required");
  90
  91   file = grub_file_open (args[1]);
  92   if (! file)
  93     return grub_errno;
  94
  95   /* Close the file, the only reason for opening it is validation.  */
  96   grub_file_close (file);
  97
  98   /* First try to replace the old device.  */
  99   for (newdev = loopback_list; newdev; newdev = newdev->next)
 100     if (grub_strcmp (newdev->devname, args[0]) == 0)
 101       break;
 102
 103   if (newdev)
 104     {
 105       char *newname = grub_strdup (args[1]);
 106       if (! newname)
 107         return grub_errno;
 108
 109       grub_free (newdev->filename);
 110       newdev->filename = newname;
 111
 112       /* Set has_partitions when `--partitions' was used.  */
 113       newdev->has_partitions = state[1].set;
 114
 115       return 0;
 116     }
 117
 118   /* Unable to replace it, make a new entry.  */
 119   newdev = grub_malloc (sizeof (struct grub_loopback));
 120   if (! newdev)
 121     return grub_errno;
 122
 123   newdev->devname = grub_strdup (args[0]);
 124   if (! newdev->devname)
 125     {
 126       grub_free (newdev);
 127       return grub_errno;
 128     }
 129
 130   newdev->filename = grub_strdup (args[1]);
 131   if (! newdev->filename)
 132     {
 133       grub_free (newdev->devname);
 134       grub_free (newdev);
 135       return grub_errno;
 136     }
 137
 138   /* Set has_partitions when `--partitions' was used.  */
 139   newdev->has_partitions = state[1].set;
 140
 141   /* Add the new entry to the list.  */
 142   newdev->next = loopback_list;
 143   loopback_list = newdev;
 144
 145   return 0;
 146 }
 147
 148 \f
 149 static int
 150 grub_loopback_iterate (int (*hook) (const char *name))
 151 {
 152   struct grub_loopback *d;
 153   for (d = loopback_list; d; d = d->next)
 154     {
 155       if (hook (d->devname))
 156         return 1;
 157     }
 158   return 0;
 159 }
 160
 161 static grub_err_t
 162 grub_loopback_open (const char *name, grub_disk_t disk)
 163 {
 164   grub_file_t file;
 165   struct grub_loopback *dev;
 166
 167   for (dev = loopback_list; dev; dev = dev->next)
 168     if (grub_strcmp (dev->devname, name) == 0)
 169       break;
 170
 171   if (! dev)
 172     return grub_error (GRUB_ERR_UNKNOWN_DEVICE, "Can't open device");
 173
 174   file = grub_file_open (dev->filename);
 175   if (! file)
 176     return grub_errno;
 177
 178   /* Use the filesize for the disk size, round up to a complete sector.  */
 179   disk->total_sectors = ((file->size + GRUB_DISK_SECTOR_SIZE - 1)
 180                          / GRUB_DISK_SECTOR_SIZE);
 181   disk->id = (int) dev;
 182
 183   disk->has_partitions = dev->has_partitions;
 184   disk->data = file;
 185
 186   return 0;
 187 }
 188
 189 static void
 190 grub_loopback_close (grub_disk_t disk)
 191 {
 192   grub_file_t file = (grub_file_t) disk->data;
 193
 194   grub_file_close (file);
 195 }
 196
 197 static grub_err_t
 198 grub_loopback_read (grub_disk_t disk, grub_disk_addr_t sector,
 199                     grub_size_t size, char *buf)
 200 {
 201   grub_file_t file = (grub_file_t) disk->data;
 202   grub_off_t pos;
 203
 204   grub_file_seek (file, sector << GRUB_DISK_SECTOR_BITS);
 205
 206   grub_file_read (file, buf, size << GRUB_DISK_SECTOR_BITS);
 207   if (grub_errno)
 208     return grub_errno;
 209
 210   /* In case there is more data read than there is available, in case
 211      of files that are not a multiple of GRUB_DISK_SECTOR_SIZE, fill
 212      the rest with zeros.  */
 213   pos = (sector + size) << GRUB_DISK_SECTOR_BITS;
 214   if (pos > file->size)
 215     {
 216       grub_size_t amount = pos - file->size;
 217       grub_memset (buf + (size << GRUB_DISK_SECTOR_BITS) - amount, 0, amount);
 218     }
 219
 220   return 0;
 221 }
 222
 223 static grub_err_t
 224 grub_loopback_write (grub_disk_t disk __attribute ((unused)),
 225                      grub_disk_addr_t sector __attribute ((unused)),
 226                      grub_size_t size __attribute ((unused)),
 227                      const char *buf __attribute ((unused)))
 228 {
 229   return GRUB_ERR_NOT_IMPLEMENTED_YET;
 230 }
 231
 232 static struct grub_disk_dev grub_loopback_dev =
 233   {
 234     .name = "loopback",
 235     .id = GRUB_DISK_DEVICE_LOOPBACK_ID,
 236     .iterate = grub_loopback_iterate,
 237     .open = grub_loopback_open,
 238     .close = grub_loopback_close,
 239     .read = grub_loopback_read,
 240     .write = grub_loopback_write,
 241     .next = 0
 242   };
 243
 244 \f
 245
 246 GRUB_MOD_INIT(loop)
 247 {
 248   (void) mod;                   /* To stop warning. */
 249   grub_register_command ("loopback", grub_cmd_loopback, GRUB_COMMAND_FLAG_BOTH,
 250                          "loopback [-d|-p] DEVICENAME FILE",
 251                          "Make a device of a file.", options);
 252   grub_disk_dev_register (&grub_loopback_dev);
 253 }
 254
 255 GRUB_MOD_FINI(loop)
 256 {
 257   grub_unregister_command ("loopback");
 258   grub_disk_dev_unregister (&grub_loopback_dev);
 259 }