linux/fs/partitions/msdos.c
<<
>>
Prefs
   1/*
   2 *  fs/partitions/msdos.c
   3 *
   4 *  Code extracted from drivers/block/genhd.c
   5 *  Copyright (C) 1991-1998  Linus Torvalds
   6 *
   7 *  Thanks to Branko Lankester, lankeste@fwi.uva.nl, who found a bug
   8 *  in the early extended-partition checks and added DM partitions
   9 *
  10 *  Support for DiskManager v6.0x added by Mark Lord,
  11 *  with information provided by OnTrack.  This now works for linux fdisk
  12 *  and LILO, as well as loadlin and bootln.  Note that disks other than
  13 *  /dev/hda *must* have a "DOS" type 0x51 partition in the first slot (hda1).
  14 *
  15 *  More flexible handling of extended partitions - aeb, 950831
  16 *
  17 *  Check partition table on IDE disks for common CHS translations
  18 *
  19 *  Re-organised Feb 1998 Russell King
  20 */
  21#include <linux/msdos_fs.h>
  22
  23#include "check.h"
  24#include "msdos.h"
  25#include "efi.h"
  26
  27/*
  28 * Many architectures don't like unaligned accesses, while
  29 * the nr_sects and start_sect partition table entries are
  30 * at a 2 (mod 4) address.
  31 */
  32#include <asm/unaligned.h>
  33
  34#define SYS_IND(p)      (get_unaligned(&p->sys_ind))
  35#define NR_SECTS(p)     ({ __le32 __a = get_unaligned(&p->nr_sects);    \
  36                                le32_to_cpu(__a); \
  37                        })
  38
  39#define START_SECT(p)   ({ __le32 __a = get_unaligned(&p->start_sect);  \
  40                                le32_to_cpu(__a); \
  41                        })
  42
  43static inline int is_extended_partition(struct partition *p)
  44{
  45        return (SYS_IND(p) == DOS_EXTENDED_PARTITION ||
  46                SYS_IND(p) == WIN98_EXTENDED_PARTITION ||
  47                SYS_IND(p) == LINUX_EXTENDED_PARTITION);
  48}
  49
  50#define MSDOS_LABEL_MAGIC1      0x55
  51#define MSDOS_LABEL_MAGIC2      0xAA
  52
  53static inline int
  54msdos_magic_present(unsigned char *p)
  55{
  56        return (p[0] == MSDOS_LABEL_MAGIC1 && p[1] == MSDOS_LABEL_MAGIC2);
  57}
  58
  59/* Value is EBCDIC 'IBMA' */
  60#define AIX_LABEL_MAGIC1        0xC9
  61#define AIX_LABEL_MAGIC2        0xC2
  62#define AIX_LABEL_MAGIC3        0xD4
  63#define AIX_LABEL_MAGIC4        0xC1
  64static int aix_magic_present(unsigned char *p, struct block_device *bdev)
  65{
  66        struct partition *pt = (struct partition *) (p + 0x1be);
  67        Sector sect;
  68        unsigned char *d;
  69        int slot, ret = 0;
  70
  71        if (!(p[0] == AIX_LABEL_MAGIC1 &&
  72                p[1] == AIX_LABEL_MAGIC2 &&
  73                p[2] == AIX_LABEL_MAGIC3 &&
  74                p[3] == AIX_LABEL_MAGIC4))
  75                return 0;
  76        /* Assume the partition table is valid if Linux partitions exists */
  77        for (slot = 1; slot <= 4; slot++, pt++) {
  78                if (pt->sys_ind == LINUX_SWAP_PARTITION ||
  79                        pt->sys_ind == LINUX_RAID_PARTITION ||
  80                        pt->sys_ind == LINUX_DATA_PARTITION ||
  81                        pt->sys_ind == LINUX_LVM_PARTITION ||
  82                        is_extended_partition(pt))
  83                        return 0;
  84        }
  85        d = read_dev_sector(bdev, 7, &sect);
  86        if (d) {
  87                if (d[0] == '_' && d[1] == 'L' && d[2] == 'V' && d[3] == 'M')
  88                        ret = 1;
  89                put_dev_sector(sect);
  90        };
  91        return ret;
  92}
  93
  94/*
  95 * Create devices for each logical partition in an extended partition.
  96 * The logical partitions form a linked list, with each entry being
  97 * a partition table with two entries.  The first entry
  98 * is the real data partition (with a start relative to the partition
  99 * table start).  The second is a pointer to the next logical partition
 100 * (with a start relative to the entire extended partition).
 101 * We do not create a Linux partition for the partition tables, but
 102 * only for the actual data partitions.
 103 */
 104
 105static void
 106parse_extended(struct parsed_partitions *state, struct block_device *bdev,
 107                        u32 first_sector, u32 first_size)
 108{
 109        struct partition *p;
 110        Sector sect;
 111        unsigned char *data;
 112        u32 this_sector, this_size;
 113        int sector_size = bdev_hardsect_size(bdev) / 512;
 114        int loopct = 0;         /* number of links followed
 115                                   without finding a data partition */
 116        int i;
 117
 118        this_sector = first_sector;
 119        this_size = first_size;
 120
 121        while (1) {
 122                if (++loopct > 100)
 123                        return;
 124                if (state->next == state->limit)
 125                        return;
 126                data = read_dev_sector(bdev, this_sector, &sect);
 127                if (!data)
 128                        return;
 129
 130                if (!msdos_magic_present(data + 510))
 131                        goto done; 
 132
 133                p = (struct partition *) (data + 0x1be);
 134
 135                /*
 136                 * Usually, the first entry is the real data partition,
 137                 * the 2nd entry is the next extended partition, or empty,
 138                 * and the 3rd and 4th entries are unused.
 139                 * However, DRDOS sometimes has the extended partition as
 140                 * the first entry (when the data partition is empty),
 141                 * and OS/2 seems to use all four entries.
 142                 */
 143
 144                /* 
 145                 * First process the data partition(s)
 146                 */
 147                for (i=0; i<4; i++, p++) {
 148                        u32 offs, size, next;
 149                        if (!NR_SECTS(p) || is_extended_partition(p))
 150                                continue;
 151
 152                        /* Check the 3rd and 4th entries -
 153                           these sometimes contain random garbage */
 154                        offs = START_SECT(p)*sector_size;
 155                        size = NR_SECTS(p)*sector_size;
 156                        next = this_sector + offs;
 157                        if (i >= 2) {
 158                                if (offs + size > this_size)
 159                                        continue;
 160                                if (next < first_sector)
 161                                        continue;
 162                                if (next + size > first_sector + first_size)
 163                                        continue;
 164                        }
 165
 166                        put_partition(state, state->next, next, size);
 167                        if (SYS_IND(p) == LINUX_RAID_PARTITION)
 168                                state->parts[state->next].flags = ADDPART_FLAG_RAID;
 169                        loopct = 0;
 170                        if (++state->next == state->limit)
 171                                goto done;
 172                }
 173                /*
 174                 * Next, process the (first) extended partition, if present.
 175                 * (So far, there seems to be no reason to make
 176                 *  parse_extended()  recursive and allow a tree
 177                 *  of extended partitions.)
 178                 * It should be a link to the next logical partition.
 179                 */
 180                p -= 4;
 181                for (i=0; i<4; i++, p++)
 182                        if (NR_SECTS(p) && is_extended_partition(p))
 183                                break;
 184                if (i == 4)
 185                        goto done;       /* nothing left to do */
 186
 187                this_sector = first_sector + START_SECT(p) * sector_size;
 188                this_size = NR_SECTS(p) * sector_size;
 189                put_dev_sector(sect);
 190        }
 191done:
 192        put_dev_sector(sect);
 193}
 194
 195/* james@bpgc.com: Solaris has a nasty indicator: 0x82 which also
 196   indicates linux swap.  Be careful before believing this is Solaris. */
 197
 198static void
 199parse_solaris_x86(struct parsed_partitions *state, struct block_device *bdev,
 200                        u32 offset, u32 size, int origin)
 201{
 202#ifdef CONFIG_SOLARIS_X86_PARTITION
 203        Sector sect;
 204        struct solaris_x86_vtoc *v;
 205        int i;
 206        short max_nparts;
 207
 208        v = (struct solaris_x86_vtoc *)read_dev_sector(bdev, offset+1, &sect);
 209        if (!v)
 210                return;
 211        if (le32_to_cpu(v->v_sanity) != SOLARIS_X86_VTOC_SANE) {
 212                put_dev_sector(sect);
 213                return;
 214        }
 215        printk(" %s%d: <solaris:", state->name, origin);
 216        if (le32_to_cpu(v->v_version) != 1) {
 217                printk("  cannot handle version %d vtoc>\n",
 218                        le32_to_cpu(v->v_version));
 219                put_dev_sector(sect);
 220                return;
 221        }
 222        /* Ensure we can handle previous case of VTOC with 8 entries gracefully */
 223        max_nparts = le16_to_cpu (v->v_nparts) > 8 ? SOLARIS_X86_NUMSLICE : 8;
 224        for (i=0; i<max_nparts && state->next<state->limit; i++) {
 225                struct solaris_x86_slice *s = &v->v_slice[i];
 226                if (s->s_size == 0)
 227                        continue;
 228                printk(" [s%d]", i);
 229                /* solaris partitions are relative to current MS-DOS
 230                 * one; must add the offset of the current partition */
 231                put_partition(state, state->next++,
 232                                 le32_to_cpu(s->s_start)+offset,
 233                                 le32_to_cpu(s->s_size));
 234        }
 235        put_dev_sector(sect);
 236        printk(" >\n");
 237#endif
 238}
 239
 240#if defined(CONFIG_BSD_DISKLABEL)
 241/* 
 242 * Create devices for BSD partitions listed in a disklabel, under a
 243 * dos-like partition. See parse_extended() for more information.
 244 */
 245static void
 246parse_bsd(struct parsed_partitions *state, struct block_device *bdev,
 247                u32 offset, u32 size, int origin, char *flavour,
 248                int max_partitions)
 249{
 250        Sector sect;
 251        struct bsd_disklabel *l;
 252        struct bsd_partition *p;
 253
 254        l = (struct bsd_disklabel *)read_dev_sector(bdev, offset+1, &sect);
 255        if (!l)
 256                return;
 257        if (le32_to_cpu(l->d_magic) != BSD_DISKMAGIC) {
 258                put_dev_sector(sect);
 259                return;
 260        }
 261        printk(" %s%d: <%s:", state->name, origin, flavour);
 262
 263        if (le16_to_cpu(l->d_npartitions) < max_partitions)
 264                max_partitions = le16_to_cpu(l->d_npartitions);
 265        for (p = l->d_partitions; p - l->d_partitions < max_partitions; p++) {
 266                u32 bsd_start, bsd_size;
 267
 268                if (state->next == state->limit)
 269                        break;
 270                if (p->p_fstype == BSD_FS_UNUSED) 
 271                        continue;
 272                bsd_start = le32_to_cpu(p->p_offset);
 273                bsd_size = le32_to_cpu(p->p_size);
 274                if (offset == bsd_start && size == bsd_size)
 275                        /* full parent partition, we have it already */
 276                        continue;
 277                if (offset > bsd_start || offset+size < bsd_start+bsd_size) {
 278                        printk("bad subpartition - ignored\n");
 279                        continue;
 280                }
 281                put_partition(state, state->next++, bsd_start, bsd_size);
 282        }
 283        put_dev_sector(sect);
 284        if (le16_to_cpu(l->d_npartitions) > max_partitions)
 285                printk(" (ignored %d more)",
 286                       le16_to_cpu(l->d_npartitions) - max_partitions);
 287        printk(" >\n");
 288}
 289#endif
 290
 291static void
 292parse_freebsd(struct parsed_partitions *state, struct block_device *bdev,
 293                u32 offset, u32 size, int origin)
 294{
 295#ifdef CONFIG_BSD_DISKLABEL
 296        parse_bsd(state, bdev, offset, size, origin,
 297                        "bsd", BSD_MAXPARTITIONS);
 298#endif
 299}
 300
 301static void
 302parse_netbsd(struct parsed_partitions *state, struct block_device *bdev,
 303                u32 offset, u32 size, int origin)
 304{
 305#ifdef CONFIG_BSD_DISKLABEL
 306        parse_bsd(state, bdev, offset, size, origin,
 307                        "netbsd", BSD_MAXPARTITIONS);
 308#endif
 309}
 310
 311static void
 312parse_openbsd(struct parsed_partitions *state, struct block_device *bdev,
 313                u32 offset, u32 size, int origin)
 314{
 315#ifdef CONFIG_BSD_DISKLABEL
 316        parse_bsd(state, bdev, offset, size, origin,
 317                        "openbsd", OPENBSD_MAXPARTITIONS);
 318#endif
 319}
 320
 321/*
 322 * Create devices for Unixware partitions listed in a disklabel, under a
 323 * dos-like partition. See parse_extended() for more information.
 324 */
 325static void
 326parse_unixware(struct parsed_partitions *state, struct block_device *bdev,
 327                u32 offset, u32 size, int origin)
 328{
 329#ifdef CONFIG_UNIXWARE_DISKLABEL
 330        Sector sect;
 331        struct unixware_disklabel *l;
 332        struct unixware_slice *p;
 333
 334        l = (struct unixware_disklabel *)read_dev_sector(bdev, offset+29, &sect);
 335        if (!l)
 336                return;
 337        if (le32_to_cpu(l->d_magic) != UNIXWARE_DISKMAGIC ||
 338            le32_to_cpu(l->vtoc.v_magic) != UNIXWARE_DISKMAGIC2) {
 339                put_dev_sector(sect);
 340                return;
 341        }
 342        printk(" %s%d: <unixware:", state->name, origin);
 343        p = &l->vtoc.v_slice[1];
 344        /* I omit the 0th slice as it is the same as whole disk. */
 345        while (p - &l->vtoc.v_slice[0] < UNIXWARE_NUMSLICE) {
 346                if (state->next == state->limit)
 347                        break;
 348
 349                if (p->s_label != UNIXWARE_FS_UNUSED)
 350                        put_partition(state, state->next++,
 351                                                START_SECT(p), NR_SECTS(p));
 352                p++;
 353        }
 354        put_dev_sector(sect);
 355        printk(" >\n");
 356#endif
 357}
 358
 359/*
 360 * Minix 2.0.0/2.0.2 subpartition support.
 361 * Anand Krishnamurthy <anandk@wiproge.med.ge.com>
 362 * Rajeev V. Pillai    <rajeevvp@yahoo.com>
 363 */
 364static void
 365parse_minix(struct parsed_partitions *state, struct block_device *bdev,
 366                u32 offset, u32 size, int origin)
 367{
 368#ifdef CONFIG_MINIX_SUBPARTITION
 369        Sector sect;
 370        unsigned char *data;
 371        struct partition *p;
 372        int i;
 373
 374        data = read_dev_sector(bdev, offset, &sect);
 375        if (!data)
 376                return;
 377
 378        p = (struct partition *)(data + 0x1be);
 379
 380        /* The first sector of a Minix partition can have either
 381         * a secondary MBR describing its subpartitions, or
 382         * the normal boot sector. */
 383        if (msdos_magic_present (data + 510) &&
 384            SYS_IND(p) == MINIX_PARTITION) { /* subpartition table present */
 385
 386                printk(" %s%d: <minix:", state->name, origin);
 387                for (i = 0; i < MINIX_NR_SUBPARTITIONS; i++, p++) {
 388                        if (state->next == state->limit)
 389                                break;
 390                        /* add each partition in use */
 391                        if (SYS_IND(p) == MINIX_PARTITION)
 392                                put_partition(state, state->next++,
 393                                              START_SECT(p), NR_SECTS(p));
 394                }
 395                printk(" >\n");
 396        }
 397        put_dev_sector(sect);
 398#endif /* CONFIG_MINIX_SUBPARTITION */
 399}
 400
 401static struct {
 402        unsigned char id;
 403        void (*parse)(struct parsed_partitions *, struct block_device *,
 404                        u32, u32, int);
 405} subtypes[] = {
 406        {FREEBSD_PARTITION, parse_freebsd},
 407        {NETBSD_PARTITION, parse_netbsd},
 408        {OPENBSD_PARTITION, parse_openbsd},
 409        {MINIX_PARTITION, parse_minix},
 410        {UNIXWARE_PARTITION, parse_unixware},
 411        {SOLARIS_X86_PARTITION, parse_solaris_x86},
 412        {NEW_SOLARIS_X86_PARTITION, parse_solaris_x86},
 413        {0, NULL},
 414};
 415 
 416int msdos_partition(struct parsed_partitions *state, struct block_device *bdev)
 417{
 418        int sector_size = bdev_hardsect_size(bdev) / 512;
 419        Sector sect;
 420        unsigned char *data;
 421        struct partition *p;
 422        struct fat_boot_sector *fb;
 423        int slot;
 424
 425        data = read_dev_sector(bdev, 0, &sect);
 426        if (!data)
 427                return -1;
 428        if (!msdos_magic_present(data + 510)) {
 429                put_dev_sector(sect);
 430                return 0;
 431        }
 432
 433        if (aix_magic_present(data, bdev)) {
 434                put_dev_sector(sect);
 435                printk( " [AIX]");
 436                return 0;
 437        }
 438
 439        /*
 440         * Now that the 55aa signature is present, this is probably
 441         * either the boot sector of a FAT filesystem or a DOS-type
 442         * partition table. Reject this in case the boot indicator
 443         * is not 0 or 0x80.
 444         */
 445        p = (struct partition *) (data + 0x1be);
 446        for (slot = 1; slot <= 4; slot++, p++) {
 447                if (p->boot_ind != 0 && p->boot_ind != 0x80) {
 448                        /*
 449                         * Even without a valid boot inidicator value
 450                         * its still possible this is valid FAT filesystem
 451                         * without a partition table.
 452                         */
 453                        fb = (struct fat_boot_sector *) data;
 454                        if (slot == 1 && fb->reserved && fb->fats
 455                                && fat_valid_media(fb->media)) {
 456                                printk("\n");
 457                                put_dev_sector(sect);
 458                                return 1;
 459                        } else {
 460                                put_dev_sector(sect);
 461                                return 0;
 462                        }
 463                }
 464        }
 465
 466#ifdef CONFIG_EFI_PARTITION
 467        p = (struct partition *) (data + 0x1be);
 468        for (slot = 1 ; slot <= 4 ; slot++, p++) {
 469                /* If this is an EFI GPT disk, msdos should ignore it. */
 470                if (SYS_IND(p) == EFI_PMBR_OSTYPE_EFI_GPT) {
 471                        put_dev_sector(sect);
 472                        return 0;
 473                }
 474        }
 475#endif
 476        p = (struct partition *) (data + 0x1be);
 477
 478        /*
 479         * Look for partitions in two passes:
 480         * First find the primary and DOS-type extended partitions.
 481         * On the second pass look inside *BSD, Unixware and Solaris partitions.
 482         */
 483
 484        state->next = 5;
 485        for (slot = 1 ; slot <= 4 ; slot++, p++) {
 486                u32 start = START_SECT(p)*sector_size;
 487                u32 size = NR_SECTS(p)*sector_size;
 488                if (!size)
 489                        continue;
 490                if (is_extended_partition(p)) {
 491                        /* prevent someone doing mkfs or mkswap on an
 492                           extended partition, but leave room for LILO */
 493                        put_partition(state, slot, start, size == 1 ? 1 : 2);
 494                        printk(" <");
 495                        parse_extended(state, bdev, start, size);
 496                        printk(" >");
 497                        continue;
 498                }
 499                put_partition(state, slot, start, size);
 500                if (SYS_IND(p) == LINUX_RAID_PARTITION)
 501                        state->parts[slot].flags = 1;
 502                if (SYS_IND(p) == DM6_PARTITION)
 503                        printk("[DM]");
 504                if (SYS_IND(p) == EZD_PARTITION)
 505                        printk("[EZD]");
 506        }
 507
 508        printk("\n");
 509
 510        /* second pass - output for each on a separate line */
 511        p = (struct partition *) (0x1be + data);
 512        for (slot = 1 ; slot <= 4 ; slot++, p++) {
 513                unsigned char id = SYS_IND(p);
 514                int n;
 515
 516                if (!NR_SECTS(p))
 517                        continue;
 518
 519                for (n = 0; subtypes[n].parse && id != subtypes[n].id; n++)
 520                        ;
 521
 522                if (!subtypes[n].parse)
 523                        continue;
 524                subtypes[n].parse(state, bdev, START_SECT(p)*sector_size,
 525                                                NR_SECTS(p)*sector_size, slot);
 526        }
 527        put_dev_sector(sect);
 528        return 1;
 529}
 530
lxr.linux.no kindly hosted by Redpill Linpro AS, provider of Linux consulting and operations services since 1995.