block/partitions/msdos.c

/* [<][>][^][v][top][bottom][index][help] */
This source file includes following definitions.
nr_sects
start_sect
is_extended_partition
msdos_magic_present
aix_magic_present
set_info
parse_extended
parse_solaris_x86
parse_bsd
parse_freebsd
parse_netbsd
parse_openbsd
parse_unixware
parse_minix
msdos_partition
   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  *  fs/partitions/msdos.c
   4  *
   5  *  Code extracted from drivers/block/genhd.c
   6  *  Copyright (C) 1991-1998  Linus Torvalds
   7  *
   8  *  Thanks to Branko Lankester, lankeste@fwi.uva.nl, who found a bug
   9  *  in the early extended-partition checks and added DM partitions
  10  *
  11  *  Support for DiskManager v6.0x added by Mark Lord,
  12  *  with information provided by OnTrack.  This now works for linux fdisk
  13  *  and LILO, as well as loadlin and bootln.  Note that disks other than
  14  *  /dev/hda *must* have a "DOS" type 0x51 partition in the first slot (hda1).
  15  *
  16  *  More flexible handling of extended partitions - aeb, 950831
  17  *
  18  *  Check partition table on IDE disks for common CHS translations
  19  *
  20  *  Re-organised Feb 1998 Russell King
  21  */
  22 #include <linux/msdos_fs.h>
  23 
  24 #include "check.h"
  25 #include "msdos.h"
  26 #include "efi.h"
  27 #include "aix.h"
  28 
  29 /*
  30  * Many architectures don't like unaligned accesses, while
  31  * the nr_sects and start_sect partition table entries are
  32  * at a 2 (mod 4) address.
  33  */
  34 #include <asm/unaligned.h>
  35 
  36 #define SYS_IND(p)      get_unaligned(&p->sys_ind)
  37 
  38 static inline sector_t nr_sects(struct partition *p)
  39 {
  40         return (sector_t)get_unaligned_le32(&p->nr_sects);
  41 }
  42 
  43 static inline sector_t start_sect(struct partition *p)
  44 {
  45         return (sector_t)get_unaligned_le32(&p->start_sect);
  46 }
  47 
  48 static inline int is_extended_partition(struct partition *p)
  49 {
  50         return (SYS_IND(p) == DOS_EXTENDED_PARTITION ||
  51                 SYS_IND(p) == WIN98_EXTENDED_PARTITION ||
  52                 SYS_IND(p) == LINUX_EXTENDED_PARTITION);
  53 }
  54 
  55 #define MSDOS_LABEL_MAGIC1      0x55
  56 #define MSDOS_LABEL_MAGIC2      0xAA
  57 
  58 static inline int
  59 msdos_magic_present(unsigned char *p)
  60 {
  61         return (p[0] == MSDOS_LABEL_MAGIC1 && p[1] == MSDOS_LABEL_MAGIC2);
  62 }
  63 
  64 /* Value is EBCDIC 'IBMA' */
  65 #define AIX_LABEL_MAGIC1        0xC9
  66 #define AIX_LABEL_MAGIC2        0xC2
  67 #define AIX_LABEL_MAGIC3        0xD4
  68 #define AIX_LABEL_MAGIC4        0xC1
  69 static int aix_magic_present(struct parsed_partitions *state, unsigned char *p)
  70 {
  71         struct partition *pt = (struct partition *) (p + 0x1be);
  72         Sector sect;
  73         unsigned char *d;
  74         int slot, ret = 0;
  75 
  76         if (!(p[0] == AIX_LABEL_MAGIC1 &&
  77                 p[1] == AIX_LABEL_MAGIC2 &&
  78                 p[2] == AIX_LABEL_MAGIC3 &&
  79                 p[3] == AIX_LABEL_MAGIC4))
  80                 return 0;
  81         /* Assume the partition table is valid if Linux partitions exists */
  82         for (slot = 1; slot <= 4; slot++, pt++) {
  83                 if (pt->sys_ind == LINUX_SWAP_PARTITION ||
  84                         pt->sys_ind == LINUX_RAID_PARTITION ||
  85                         pt->sys_ind == LINUX_DATA_PARTITION ||
  86                         pt->sys_ind == LINUX_LVM_PARTITION ||
  87                         is_extended_partition(pt))
  88                         return 0;
  89         }
  90         d = read_part_sector(state, 7, &sect);
  91         if (d) {
  92                 if (d[0] == '_' && d[1] == 'L' && d[2] == 'V' && d[3] == 'M')
  93                         ret = 1;
  94                 put_dev_sector(sect);
  95         }
  96         return ret;
  97 }
  98 
  99 static void set_info(struct parsed_partitions *state, int slot,
 100                      u32 disksig)
 101 {
 102         struct partition_meta_info *info = &state->parts[slot].info;
 103 
 104         snprintf(info->uuid, sizeof(info->uuid), "%08x-%02x", disksig,
 105                  slot);
 106         info->volname[0] = 0;
 107         state->parts[slot].has_info = true;
 108 }
 109 
 110 /*
 111  * Create devices for each logical partition in an extended partition.
 112  * The logical partitions form a linked list, with each entry being
 113  * a partition table with two entries.  The first entry
 114  * is the real data partition (with a start relative to the partition
 115  * table start).  The second is a pointer to the next logical partition
 116  * (with a start relative to the entire extended partition).
 117  * We do not create a Linux partition for the partition tables, but
 118  * only for the actual data partitions.
 119  */
 120 
 121 static void parse_extended(struct parsed_partitions *state,
 122                            sector_t first_sector, sector_t first_size,
 123                            u32 disksig)
 124 {
 125         struct partition *p;
 126         Sector sect;
 127         unsigned char *data;
 128         sector_t this_sector, this_size;
 129         sector_t sector_size = bdev_logical_block_size(state->bdev) / 512;
 130         int loopct = 0;         /* number of links followed
 131                                    without finding a data partition */
 132         int i;
 133 
 134         this_sector = first_sector;
 135         this_size = first_size;
 136 
 137         while (1) {
 138                 if (++loopct > 100)
 139                         return;
 140                 if (state->next == state->limit)
 141                         return;
 142                 data = read_part_sector(state, this_sector, &sect);
 143                 if (!data)
 144                         return;
 145 
 146                 if (!msdos_magic_present(data + 510))
 147                         goto done;
 148 
 149                 p = (struct partition *) (data + 0x1be);
 150 
 151                 /*
 152                  * Usually, the first entry is the real data partition,
 153                  * the 2nd entry is the next extended partition, or empty,
 154                  * and the 3rd and 4th entries are unused.
 155                  * However, DRDOS sometimes has the extended partition as
 156                  * the first entry (when the data partition is empty),
 157                  * and OS/2 seems to use all four entries.
 158                  */
 159 
 160                 /*
 161                  * First process the data partition(s)
 162                  */
 163                 for (i = 0; i < 4; i++, p++) {
 164                         sector_t offs, size, next;
 165 
 166                         if (!nr_sects(p) || is_extended_partition(p))
 167                                 continue;
 168 
 169                         /* Check the 3rd and 4th entries -
 170                            these sometimes contain random garbage */
 171                         offs = start_sect(p)*sector_size;
 172                         size = nr_sects(p)*sector_size;
 173                         next = this_sector + offs;
 174                         if (i >= 2) {
 175                                 if (offs + size > this_size)
 176                                         continue;
 177                                 if (next < first_sector)
 178                                         continue;
 179                                 if (next + size > first_sector + first_size)
 180                                         continue;
 181                         }
 182 
 183                         put_partition(state, state->next, next, size);
 184                         set_info(state, state->next, disksig);
 185                         if (SYS_IND(p) == LINUX_RAID_PARTITION)
 186                                 state->parts[state->next].flags = ADDPART_FLAG_RAID;
 187                         loopct = 0;
 188                         if (++state->next == state->limit)
 189                                 goto done;
 190                 }
 191                 /*
 192                  * Next, process the (first) extended partition, if present.
 193                  * (So far, there seems to be no reason to make
 194                  *  parse_extended()  recursive and allow a tree
 195                  *  of extended partitions.)
 196                  * It should be a link to the next logical partition.
 197                  */
 198                 p -= 4;
 199                 for (i = 0; i < 4; i++, p++)
 200                         if (nr_sects(p) && is_extended_partition(p))
 201                                 break;
 202                 if (i == 4)
 203                         goto done;       /* nothing left to do */
 204 
 205                 this_sector = first_sector + start_sect(p) * sector_size;
 206                 this_size = nr_sects(p) * sector_size;
 207                 put_dev_sector(sect);
 208         }
 209 done:
 210         put_dev_sector(sect);
 211 }
 212 
 213 /* james@bpgc.com: Solaris has a nasty indicator: 0x82 which also
 214    indicates linux swap.  Be careful before believing this is Solaris. */
 215 
 216 static void parse_solaris_x86(struct parsed_partitions *state,
 217                               sector_t offset, sector_t size, int origin)
 218 {
 219 #ifdef CONFIG_SOLARIS_X86_PARTITION
 220         Sector sect;
 221         struct solaris_x86_vtoc *v;
 222         int i;
 223         short max_nparts;
 224 
 225         v = read_part_sector(state, offset + 1, &sect);
 226         if (!v)
 227                 return;
 228         if (le32_to_cpu(v->v_sanity) != SOLARIS_X86_VTOC_SANE) {
 229                 put_dev_sector(sect);
 230                 return;
 231         }
 232         {
 233                 char tmp[1 + BDEVNAME_SIZE + 10 + 11 + 1];
 234 
 235                 snprintf(tmp, sizeof(tmp), " %s%d: <solaris:", state->name, origin);
 236                 strlcat(state->pp_buf, tmp, PAGE_SIZE);
 237         }
 238         if (le32_to_cpu(v->v_version) != 1) {
 239                 char tmp[64];
 240 
 241                 snprintf(tmp, sizeof(tmp), "  cannot handle version %d vtoc>\n",
 242                          le32_to_cpu(v->v_version));
 243                 strlcat(state->pp_buf, tmp, PAGE_SIZE);
 244                 put_dev_sector(sect);
 245                 return;
 246         }
 247         /* Ensure we can handle previous case of VTOC with 8 entries gracefully */
 248         max_nparts = le16_to_cpu(v->v_nparts) > 8 ? SOLARIS_X86_NUMSLICE : 8;
 249         for (i = 0; i < max_nparts && state->next < state->limit; i++) {
 250                 struct solaris_x86_slice *s = &v->v_slice[i];
 251                 char tmp[3 + 10 + 1 + 1];
 252 
 253                 if (s->s_size == 0)
 254                         continue;
 255                 snprintf(tmp, sizeof(tmp), " [s%d]", i);
 256                 strlcat(state->pp_buf, tmp, PAGE_SIZE);
 257                 /* solaris partitions are relative to current MS-DOS
 258                  * one; must add the offset of the current partition */
 259                 put_partition(state, state->next++,
 260                                  le32_to_cpu(s->s_start)+offset,
 261                                  le32_to_cpu(s->s_size));
 262         }
 263         put_dev_sector(sect);
 264         strlcat(state->pp_buf, " >\n", PAGE_SIZE);
 265 #endif
 266 }
 267 
 268 #if defined(CONFIG_BSD_DISKLABEL)
 269 /*
 270  * Create devices for BSD partitions listed in a disklabel, under a
 271  * dos-like partition. See parse_extended() for more information.
 272  */
 273 static void parse_bsd(struct parsed_partitions *state,
 274                       sector_t offset, sector_t size, int origin, char *flavour,
 275                       int max_partitions)
 276 {
 277         Sector sect;
 278         struct bsd_disklabel *l;
 279         struct bsd_partition *p;
 280         char tmp[64];
 281 
 282         l = read_part_sector(state, offset + 1, &sect);
 283         if (!l)
 284                 return;
 285         if (le32_to_cpu(l->d_magic) != BSD_DISKMAGIC) {
 286                 put_dev_sector(sect);
 287                 return;
 288         }
 289 
 290         snprintf(tmp, sizeof(tmp), " %s%d: <%s:", state->name, origin, flavour);
 291         strlcat(state->pp_buf, tmp, PAGE_SIZE);
 292 
 293         if (le16_to_cpu(l->d_npartitions) < max_partitions)
 294                 max_partitions = le16_to_cpu(l->d_npartitions);
 295         for (p = l->d_partitions; p - l->d_partitions < max_partitions; p++) {
 296                 sector_t bsd_start, bsd_size;
 297 
 298                 if (state->next == state->limit)
 299                         break;
 300                 if (p->p_fstype == BSD_FS_UNUSED)
 301                         continue;
 302                 bsd_start = le32_to_cpu(p->p_offset);
 303                 bsd_size = le32_to_cpu(p->p_size);
 304                 /* FreeBSD has relative offset if C partition offset is zero */
 305                 if (memcmp(flavour, "bsd\0", 4) == 0 &&
 306                     le32_to_cpu(l->d_partitions[2].p_offset) == 0)
 307                         bsd_start += offset;
 308                 if (offset == bsd_start && size == bsd_size)
 309                         /* full parent partition, we have it already */
 310                         continue;
 311                 if (offset > bsd_start || offset+size < bsd_start+bsd_size) {
 312                         strlcat(state->pp_buf, "bad subpartition - ignored\n", PAGE_SIZE);
 313                         continue;
 314                 }
 315                 put_partition(state, state->next++, bsd_start, bsd_size);
 316         }
 317         put_dev_sector(sect);
 318         if (le16_to_cpu(l->d_npartitions) > max_partitions) {
 319                 snprintf(tmp, sizeof(tmp), " (ignored %d more)",
 320                          le16_to_cpu(l->d_npartitions) - max_partitions);
 321                 strlcat(state->pp_buf, tmp, PAGE_SIZE);
 322         }
 323         strlcat(state->pp_buf, " >\n", PAGE_SIZE);
 324 }
 325 #endif
 326 
 327 static void parse_freebsd(struct parsed_partitions *state,
 328                           sector_t offset, sector_t size, int origin)
 329 {
 330 #ifdef CONFIG_BSD_DISKLABEL
 331         parse_bsd(state, offset, size, origin, "bsd", BSD_MAXPARTITIONS);
 332 #endif
 333 }
 334 
 335 static void parse_netbsd(struct parsed_partitions *state,
 336                          sector_t offset, sector_t size, int origin)
 337 {
 338 #ifdef CONFIG_BSD_DISKLABEL
 339         parse_bsd(state, offset, size, origin, "netbsd", BSD_MAXPARTITIONS);
 340 #endif
 341 }
 342 
 343 static void parse_openbsd(struct parsed_partitions *state,
 344                           sector_t offset, sector_t size, int origin)
 345 {
 346 #ifdef CONFIG_BSD_DISKLABEL
 347         parse_bsd(state, offset, size, origin, "openbsd",
 348                   OPENBSD_MAXPARTITIONS);
 349 #endif
 350 }
 351 
 352 /*
 353  * Create devices for Unixware partitions listed in a disklabel, under a
 354  * dos-like partition. See parse_extended() for more information.
 355  */
 356 static void parse_unixware(struct parsed_partitions *state,
 357                            sector_t offset, sector_t size, int origin)
 358 {
 359 #ifdef CONFIG_UNIXWARE_DISKLABEL
 360         Sector sect;
 361         struct unixware_disklabel *l;
 362         struct unixware_slice *p;
 363 
 364         l = read_part_sector(state, offset + 29, &sect);
 365         if (!l)
 366                 return;
 367         if (le32_to_cpu(l->d_magic) != UNIXWARE_DISKMAGIC ||
 368             le32_to_cpu(l->vtoc.v_magic) != UNIXWARE_DISKMAGIC2) {
 369                 put_dev_sector(sect);
 370                 return;
 371         }
 372         {
 373                 char tmp[1 + BDEVNAME_SIZE + 10 + 12 + 1];
 374 
 375                 snprintf(tmp, sizeof(tmp), " %s%d: <unixware:", state->name, origin);
 376                 strlcat(state->pp_buf, tmp, PAGE_SIZE);
 377         }
 378         p = &l->vtoc.v_slice[1];
 379         /* I omit the 0th slice as it is the same as whole disk. */
 380         while (p - &l->vtoc.v_slice[0] < UNIXWARE_NUMSLICE) {
 381                 if (state->next == state->limit)
 382                         break;
 383 
 384                 if (p->s_label != UNIXWARE_FS_UNUSED)
 385                         put_partition(state, state->next++,
 386                                       le32_to_cpu(p->start_sect),
 387                                       le32_to_cpu(p->nr_sects));
 388                 p++;
 389         }
 390         put_dev_sector(sect);
 391         strlcat(state->pp_buf, " >\n", PAGE_SIZE);
 392 #endif
 393 }
 394 
 395 /*
 396  * Minix 2.0.0/2.0.2 subpartition support.
 397  * Anand Krishnamurthy <anandk@wiproge.med.ge.com>
 398  * Rajeev V. Pillai    <rajeevvp@yahoo.com>
 399  */
 400 static void parse_minix(struct parsed_partitions *state,
 401                         sector_t offset, sector_t size, int origin)
 402 {
 403 #ifdef CONFIG_MINIX_SUBPARTITION
 404         Sector sect;
 405         unsigned char *data;
 406         struct partition *p;
 407         int i;
 408 
 409         data = read_part_sector(state, offset, &sect);
 410         if (!data)
 411                 return;
 412 
 413         p = (struct partition *)(data + 0x1be);
 414 
 415         /* The first sector of a Minix partition can have either
 416          * a secondary MBR describing its subpartitions, or
 417          * the normal boot sector. */
 418         if (msdos_magic_present(data + 510) &&
 419             SYS_IND(p) == MINIX_PARTITION) { /* subpartition table present */
 420                 char tmp[1 + BDEVNAME_SIZE + 10 + 9 + 1];
 421 
 422                 snprintf(tmp, sizeof(tmp), " %s%d: <minix:", state->name, origin);
 423                 strlcat(state->pp_buf, tmp, PAGE_SIZE);
 424                 for (i = 0; i < MINIX_NR_SUBPARTITIONS; i++, p++) {
 425                         if (state->next == state->limit)
 426                                 break;
 427                         /* add each partition in use */
 428                         if (SYS_IND(p) == MINIX_PARTITION)
 429                                 put_partition(state, state->next++,
 430                                               start_sect(p), nr_sects(p));
 431                 }
 432                 strlcat(state->pp_buf, " >\n", PAGE_SIZE);
 433         }
 434         put_dev_sector(sect);
 435 #endif /* CONFIG_MINIX_SUBPARTITION */
 436 }
 437 
 438 static struct {
 439         unsigned char id;
 440         void (*parse)(struct parsed_partitions *, sector_t, sector_t, int);
 441 } subtypes[] = {
 442         {FREEBSD_PARTITION, parse_freebsd},
 443         {NETBSD_PARTITION, parse_netbsd},
 444         {OPENBSD_PARTITION, parse_openbsd},
 445         {MINIX_PARTITION, parse_minix},
 446         {UNIXWARE_PARTITION, parse_unixware},
 447         {SOLARIS_X86_PARTITION, parse_solaris_x86},
 448         {NEW_SOLARIS_X86_PARTITION, parse_solaris_x86},
 449         {0, NULL},
 450 };
 451 
 452 int msdos_partition(struct parsed_partitions *state)
 453 {
 454         sector_t sector_size = bdev_logical_block_size(state->bdev) / 512;
 455         Sector sect;
 456         unsigned char *data;
 457         struct partition *p;
 458         struct fat_boot_sector *fb;
 459         int slot;
 460         u32 disksig;
 461 
 462         data = read_part_sector(state, 0, &sect);
 463         if (!data)
 464                 return -1;
 465 
 466         /*
 467          * Note order! (some AIX disks, e.g. unbootable kind,
 468          * have no MSDOS 55aa)
 469          */
 470         if (aix_magic_present(state, data)) {
 471                 put_dev_sector(sect);
 472 #ifdef CONFIG_AIX_PARTITION
 473                 return aix_partition(state);
 474 #else
 475                 strlcat(state->pp_buf, " [AIX]", PAGE_SIZE);
 476                 return 0;
 477 #endif
 478         }
 479 
 480         if (!msdos_magic_present(data + 510)) {
 481                 put_dev_sector(sect);
 482                 return 0;
 483         }
 484 
 485         /*
 486          * Now that the 55aa signature is present, this is probably
 487          * either the boot sector of a FAT filesystem or a DOS-type
 488          * partition table. Reject this in case the boot indicator
 489          * is not 0 or 0x80.
 490          */
 491         p = (struct partition *) (data + 0x1be);
 492         for (slot = 1; slot <= 4; slot++, p++) {
 493                 if (p->boot_ind != 0 && p->boot_ind != 0x80) {
 494                         /*
 495                          * Even without a valid boot inidicator value
 496                          * its still possible this is valid FAT filesystem
 497                          * without a partition table.
 498                          */
 499                         fb = (struct fat_boot_sector *) data;
 500                         if (slot == 1 && fb->reserved && fb->fats
 501                                 && fat_valid_media(fb->media)) {
 502                                 strlcat(state->pp_buf, "\n", PAGE_SIZE);
 503                                 put_dev_sector(sect);
 504                                 return 1;
 505                         } else {
 506                                 put_dev_sector(sect);
 507                                 return 0;
 508                         }
 509                 }
 510         }
 511 
 512 #ifdef CONFIG_EFI_PARTITION
 513         p = (struct partition *) (data + 0x1be);
 514         for (slot = 1 ; slot <= 4 ; slot++, p++) {
 515                 /* If this is an EFI GPT disk, msdos should ignore it. */
 516                 if (SYS_IND(p) == EFI_PMBR_OSTYPE_EFI_GPT) {
 517                         put_dev_sector(sect);
 518                         return 0;
 519                 }
 520         }
 521 #endif
 522         p = (struct partition *) (data + 0x1be);
 523 
 524         disksig = le32_to_cpup((__le32 *)(data + 0x1b8));
 525 
 526         /*
 527          * Look for partitions in two passes:
 528          * First find the primary and DOS-type extended partitions.
 529          * On the second pass look inside *BSD, Unixware and Solaris partitions.
 530          */
 531 
 532         state->next = 5;
 533         for (slot = 1 ; slot <= 4 ; slot++, p++) {
 534                 sector_t start = start_sect(p)*sector_size;
 535                 sector_t size = nr_sects(p)*sector_size;
 536 
 537                 if (!size)
 538                         continue;
 539                 if (is_extended_partition(p)) {
 540                         /*
 541                          * prevent someone doing mkfs or mkswap on an
 542                          * extended partition, but leave room for LILO
 543                          * FIXME: this uses one logical sector for > 512b
 544                          * sector, although it may not be enough/proper.
 545                          */
 546                         sector_t n = 2;
 547 
 548                         n = min(size, max(sector_size, n));
 549                         put_partition(state, slot, start, n);
 550 
 551                         strlcat(state->pp_buf, " <", PAGE_SIZE);
 552                         parse_extended(state, start, size, disksig);
 553                         strlcat(state->pp_buf, " >", PAGE_SIZE);
 554                         continue;
 555                 }
 556                 put_partition(state, slot, start, size);
 557                 set_info(state, slot, disksig);
 558                 if (SYS_IND(p) == LINUX_RAID_PARTITION)
 559                         state->parts[slot].flags = ADDPART_FLAG_RAID;
 560                 if (SYS_IND(p) == DM6_PARTITION)
 561                         strlcat(state->pp_buf, "[DM]", PAGE_SIZE);
 562                 if (SYS_IND(p) == EZD_PARTITION)
 563                         strlcat(state->pp_buf, "[EZD]", PAGE_SIZE);
 564         }
 565 
 566         strlcat(state->pp_buf, "\n", PAGE_SIZE);
 567 
 568         /* second pass - output for each on a separate line */
 569         p = (struct partition *) (0x1be + data);
 570         for (slot = 1 ; slot <= 4 ; slot++, p++) {
 571                 unsigned char id = SYS_IND(p);
 572                 int n;
 573 
 574                 if (!nr_sects(p))
 575                         continue;
 576 
 577                 for (n = 0; subtypes[n].parse && id != subtypes[n].id; n++)
 578                         ;
 579 
 580                 if (!subtypes[n].parse)
 581                         continue;
 582                 subtypes[n].parse(state, start_sect(p) * sector_size,
 583                                   nr_sects(p) * sector_size, slot);
 584         }
 585         put_dev_sector(sect);
 586         return 1;
 587 }
/* [<][>][^][v][top][bottom][index][help] */
root/block/partitions/msdos.c

DEFINITIONS
