partmap/msdos.c

   1 /* pc.c - Read PC style partition tables.  */
   2 /*
   3  *  GRUB  --  GRand Unified Bootloader
   4  *  Copyright (C) 2002,2004,2005,2006,2007,2008,2009  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/partition.h>
  21 #include <grub/msdos_partition.h>
  22 #include <grub/disk.h>
  23 #include <grub/mm.h>
  24 #include <grub/misc.h>
  25 #include <grub/dl.h>
  26
  27 static struct grub_partition_map grub_msdos_partition_map;
  28 \f
  29
  30 /* Parse the partition representation in STR and return a partition.  */
  31 static grub_partition_t
  32 grub_partition_parse (const char *str)
  33 {
  34   grub_partition_t p;
  35   struct grub_msdos_partition *pcdata;
  36
  37   char *s = (char *) str;
  38
  39   p = (grub_partition_t) grub_malloc (sizeof (*p));
  40   if (! p)
  41     return 0;
  42
  43   pcdata = (struct grub_msdos_partition *) grub_malloc (sizeof (*pcdata));
  44   if (! pcdata)
  45     goto fail;
  46
  47   p->data = pcdata;
  48   p->partmap = &grub_msdos_partition_map;
  49
  50   /* Initialize some of the fields with invalid values.  */
  51   pcdata->bsd_part = pcdata->dos_type = pcdata->bsd_type = p->index = -1;
  52
  53   /* Get the DOS partition number. The number is counted from one for
  54      the user interface, and from zero internally.  */
  55   pcdata->dos_part = grub_strtoul (s, &s, 0) - 1;
  56
  57   if (grub_errno)
  58     {
  59       /* Not found. Maybe only a BSD label is specified.  */
  60       pcdata->dos_part = -1;
  61       grub_errno = GRUB_ERR_NONE;
  62     }
  63   else if (*s == ',')
  64     s++;
  65
  66   if (*s)
  67     {
  68       if (*s >= 'a' && *s <= 'h')
  69         {
  70           pcdata->bsd_part = *s - 'a';
  71           s++;
  72         }
  73
  74       if (*s)
  75         goto fail;
  76     }
  77
  78   if (pcdata->dos_part == -1 && pcdata->bsd_part == -1)
  79     goto fail;
  80
  81   return p;
  82
  83  fail:
  84   grub_free (p);
  85   grub_free (pcdata);
  86   grub_error (GRUB_ERR_BAD_FILENAME, "invalid partition");
  87   return 0;
  88 }
  89
  90 static grub_err_t
  91 pc_partition_map_iterate (grub_disk_t disk,
  92                           int (*hook) (grub_disk_t disk,
  93                                        const grub_partition_t partition))
  94 {
  95   struct grub_partition p;
  96   struct grub_msdos_partition pcdata;
  97   struct grub_msdos_partition_mbr mbr;
  98   struct grub_msdos_partition_disk_label label;
  99   struct grub_disk raw;
 100   int labeln = 0;
 101   grub_disk_addr_t lastaddr;
 102
 103   /* Enforce raw disk access.  */
 104   raw = *disk;
 105   raw.partition = 0;
 106
 107   p.offset = 0;
 108   pcdata.ext_offset = 0;
 109   pcdata.dos_part = -1;
 110   p.data = &pcdata;
 111   p.partmap = &grub_msdos_partition_map;
 112
 113   /* Any value different than `p.offset' will satisfy the check during
 114      first loop.  */
 115   lastaddr = !p.offset;
 116
 117   while (1)
 118     {
 119       int i;
 120       struct grub_msdos_partition_entry *e;
 121
 122       /* Read the MBR.  */
 123       if (grub_disk_read (&raw, p.offset, 0, sizeof (mbr), &mbr))
 124         goto finish;
 125
 126       /* This is our loop-detection algorithm. It works the following way:
 127          It saves last position which was a power of two. Then it compares the
 128          saved value with a current one. This way it's guaranteed that the loop
 129          will be broken by at most third walk.
 130        */
 131       if (labeln && lastaddr == p.offset)
 132         return grub_error (GRUB_ERR_BAD_PART_TABLE, "loop detected");
 133
 134       labeln++;
 135       if ((labeln & (labeln - 1)) == 0)
 136         lastaddr = p.offset;
 137
 138       /* Check if it is valid.  */
 139       if (mbr.signature != grub_cpu_to_le16 (GRUB_PC_PARTITION_SIGNATURE))
 140         return grub_error (GRUB_ERR_BAD_PART_TABLE, "no signature");
 141
 142       for (i = 0; i < 4; i++)
 143         if (mbr.entries[i].flag & 0x7f)
 144           return grub_error (GRUB_ERR_BAD_PART_TABLE, "bad boot flag");
 145
 146       /* Analyze DOS partitions.  */
 147       for (p.index = 0; p.index < 4; p.index++)
 148         {
 149           e = mbr.entries + p.index;
 150
 151           p.start = p.offset + grub_le_to_cpu32 (e->start);
 152           p.len = grub_le_to_cpu32 (e->length);
 153           pcdata.bsd_part = -1;
 154           pcdata.dos_type = e->type;
 155           pcdata.bsd_type = -1;
 156
 157           grub_dprintf ("partition",
 158                         "partition %d: flag 0x%x, type 0x%x, start 0x%llx, len 0x%llx\n",
 159                         p.index, e->flag, pcdata.dos_type,
 160                         (unsigned long long) p.start,
 161                         (unsigned long long) p.len);
 162
 163           /* If this is a GPT partition, this MBR is just a dummy.  */
 164           if (e->type == GRUB_PC_PARTITION_TYPE_GPT_DISK && p.index == 0)
 165             return grub_error (GRUB_ERR_BAD_PART_TABLE, "dummy mbr");
 166
 167           /* If this partition is a normal one, call the hook.  */
 168           if (! grub_msdos_partition_is_empty (e->type)
 169               && ! grub_msdos_partition_is_extended (e->type))
 170             {
 171               pcdata.dos_part++;
 172
 173               if (hook (disk, &p))
 174                 return 1;
 175
 176               /* Check if this is a BSD partition.  */
 177               if (grub_msdos_partition_is_bsd (e->type))
 178                 {
 179                   /* Check if the BSD label is within the DOS partition.  */
 180                   if (p.len <= GRUB_PC_PARTITION_BSD_LABEL_SECTOR)
 181                     {
 182                       grub_dprintf ("partition", "no space for disk label\n");
 183                       continue;
 184                     }
 185                   /* Read the BSD label.  */
 186                   if (grub_disk_read (&raw,
 187                                       (p.start
 188                                        + GRUB_PC_PARTITION_BSD_LABEL_SECTOR),
 189                                       0,
 190                                       sizeof (label),
 191                                       &label))
 192                     goto finish;
 193
 194                   /* Check if it is valid.  */
 195                   if (label.magic
 196                       != grub_cpu_to_le32 (GRUB_PC_PARTITION_BSD_LABEL_MAGIC))
 197                     {
 198                       grub_dprintf ("partition",
 199                                     "invalid disk label magic 0x%x on partition %d\n",
 200                                     label.magic, p.index);
 201                       continue;
 202                     }
 203                   for (pcdata.bsd_part = 0;
 204                        pcdata.bsd_part < grub_cpu_to_le16 (label.num_partitions);
 205                        pcdata.bsd_part++)
 206                     {
 207                       struct grub_msdos_partition_bsd_entry *be
 208                         = label.entries + pcdata.bsd_part;
 209
 210                       p.start = grub_le_to_cpu32 (be->offset);
 211                       p.len = grub_le_to_cpu32 (be->size);
 212                       pcdata.bsd_type = be->fs_type;
 213
 214                       if (be->fs_type != GRUB_PC_PARTITION_BSD_TYPE_UNUSED)
 215                         if (hook (disk, &p))
 216                           return 1;
 217                     }
 218                 }
 219             }
 220           else if (pcdata.dos_part < 4)
 221             /* If this partition is a logical one, shouldn't increase the
 222                partition number.  */
 223             pcdata.dos_part++;
 224         }
 225
 226       /* Find an extended partition.  */
 227       for (i = 0; i < 4; i++)
 228         {
 229           e = mbr.entries + i;
 230
 231           if (grub_msdos_partition_is_extended (e->type))
 232             {
 233               p.offset = pcdata.ext_offset + grub_le_to_cpu32 (e->start);
 234               if (! pcdata.ext_offset)
 235                 pcdata.ext_offset = p.offset;
 236
 237               break;
 238             }
 239         }
 240
 241       /* If no extended partition, the end.  */
 242       if (i == 4)
 243         break;
 244     }
 245
 246  finish:
 247   return grub_errno;
 248 }
 249
 250
 251 static grub_partition_t
 252 pc_partition_map_probe (grub_disk_t disk, const char *str)
 253 {
 254   grub_partition_t p;
 255   struct grub_msdos_partition *pcdata;
 256
 257   auto int find_func (grub_disk_t d, const grub_partition_t partition);
 258
 259   int find_func (grub_disk_t d __attribute__ ((unused)),
 260                  const grub_partition_t partition)
 261     {
 262       struct grub_msdos_partition *partdata = partition->data;
 263
 264       if ((pcdata->dos_part == partdata->dos_part || pcdata->dos_part == -1)
 265           && pcdata->bsd_part == partdata->bsd_part)
 266         {
 267           grub_memcpy (p, partition, sizeof (*p));
 268           p->data = pcdata;
 269           grub_memcpy (pcdata, partdata, sizeof (*pcdata));
 270           return 1;
 271         }
 272
 273       return 0;
 274     }
 275
 276   p = grub_partition_parse (str);
 277   if (! p)
 278     return 0;
 279
 280   pcdata = p->data;
 281   pc_partition_map_iterate (disk, find_func);
 282   if (grub_errno)
 283     goto fail;
 284
 285   if (p->index < 0)
 286     {
 287       grub_error (GRUB_ERR_BAD_DEVICE, "no such partition");
 288       goto fail;
 289     }
 290
 291   return p;
 292
 293  fail:
 294   grub_free (p);
 295   grub_free (pcdata);
 296   return 0;
 297 }
 298
 299
 300 static char *
 301 pc_partition_map_get_name (const grub_partition_t p)
 302 {
 303   char *name;
 304   struct grub_msdos_partition *pcdata = p->data;
 305
 306   name = grub_malloc (13);
 307   if (! name)
 308     return 0;
 309
 310   if (pcdata->bsd_part < 0)
 311     grub_sprintf (name, "%d", pcdata->dos_part + 1);
 312   else if (pcdata->dos_part < 0)
 313     grub_sprintf (name, "%c", pcdata->bsd_part + 'a');
 314   else
 315     grub_sprintf (name, "%d,%c", pcdata->dos_part + 1, pcdata->bsd_part + 'a');
 316
 317   return name;
 318 }
 319
 320 \f
 321 /* Partition map type.  */
 322 static struct grub_partition_map grub_msdos_partition_map =
 323   {
 324     .name = "part_msdos",
 325     .iterate = pc_partition_map_iterate,
 326     .probe = pc_partition_map_probe,
 327     .get_name = pc_partition_map_get_name
 328   };
 329
 330 GRUB_MOD_INIT(pc_partition_map)
 331 {
 332   grub_partition_map_register (&grub_msdos_partition_map);
 333 }
 334
 335 GRUB_MOD_FINI(pc_partition_map)
 336 {
 337   grub_partition_map_unregister (&grub_msdos_partition_map);
 338 }