sys/kern/subr_diskmbr.c

   1 /*-
   2  * Copyright (c) 1994 Bruce D. Evans.
   3  * All rights reserved.
   4  *
   5  * Copyright (c) 1982, 1986, 1988 Regents of the University of California.
   6  * All rights reserved.
   7  *
   8  * Redistribution and use in source and binary forms, with or without
   9  * modification, are permitted provided that the following conditions
  10  * are met:
  11  * 1. Redistributions of source code must retain the above copyright
  12  *    notice, this list of conditions and the following disclaimer.
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in the
  15  *    documentation and/or other materials provided with the distribution.
  16  * 3. All advertising materials mentioning features or use of this software
  17  *    must display the following acknowledgement:
  18  *      This product includes software developed by the University of
  19  *      California, Berkeley and its contributors.
  20  * 4. Neither the name of the University nor the names of its contributors
  21  *    may be used to endorse or promote products derived from this software
  22  *    without specific prior written permission.
  23  *
  24  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  25  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  26  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  27  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  28  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  29  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  30  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  31  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  32  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  33  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  34  * SUCH DAMAGE.
  35  *
  36  *      from: @(#)ufs_disksubr.c        7.16 (Berkeley) 5/4/91
  37  *      from: ufs_disksubr.c,v 1.8 1994/06/07 01:21:39 phk Exp $
  38  * $FreeBSD: src/sys/kern/subr_diskmbr.c,v 1.45 2000/01/28 10:22:07 bde Exp $
  39  * $DragonFly: src/sys/kern/subr_diskmbr.c,v 1.26 2007/06/19 06:07:57 dillon Exp $
  40  */
  41
  42 #include <sys/param.h>
  43 #include <sys/systm.h>
  44 #include <sys/buf.h>
  45 #include <sys/conf.h>
  46 #include <sys/diskslice.h>
  47 #define DOSPTYP_EXTENDED        5
  48 #define DOSPTYP_EXTENDEDX       15
  49 #define DOSPTYP_ONTRACK         84
  50 #include <sys/diskslice.h>
  51 #include <sys/diskmbr.h>
  52 #include <sys/disk.h>
  53 #include <sys/malloc.h>
  54 #include <sys/syslog.h>
  55 #include <sys/device.h>
  56
  57 #define TRACE(str)      do { if (dsi_debug) kprintf str; } while (0)
  58
  59 static volatile u_char dsi_debug;
  60
  61 /*
  62  * This is what we have embedded in every boot1 for supporting the bogus
  63  * "Dangerously Dedicated" mode. However, the old table is broken because
  64  * it has an illegal geometry in it - it specifies 256 heads (heads = end
  65  * head + 1) which causes nasty stuff when that wraps to zero in bios code.
  66  * eg: divide by zero etc. This caused the dead-thinkpad problem, numerous
  67  * SCSI bios crashes, EFI to crash, etc.
  68  *
  69  * We still have to recognize the old table though, even though we stopped
  70  * inflicting it upon the world.
  71  */
  72 static struct dos_partition historical_bogus_partition_table[NDOSPART] = {
  73         { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, },
  74         { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, },
  75         { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, },
  76         { 0x80, 0, 1, 0, DOSPTYP_386BSD, 255, 255, 255, 0, 50000, },
  77 };
  78 static struct dos_partition historical_bogus_partition_table_fixed[NDOSPART] = {
  79         { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, },
  80         { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, },
  81         { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, },
  82         { 0x80, 0, 1, 0, DOSPTYP_386BSD, 254, 255, 255, 0, 50000, },
  83 };
  84
  85 static int check_part (char *sname, struct dos_partition *dp,
  86                            u_int64_t offset, int nsectors, int ntracks,
  87                            u_int64_t mbr_offset);
  88 static void mbr_extended (cdev_t dev, struct disk_info *info,
  89                               struct diskslices *ssp, u_int64_t ext_offset,
  90                               u_int64_t ext_size, u_int64_t base_ext_offset,
  91                               int nsectors, int ntracks, u_int64_t mbr_offset,
  92                               int level);
  93 static int mbr_setslice (char *sname, struct disk_info *info,
  94                              struct diskslice *sp, struct dos_partition *dp,
  95                              u_int64_t br_offset);
  96
  97
  98 int
  99 mbrinit(cdev_t dev, struct disk_info *info, struct diskslices **sspp)
 100 {
 101         struct buf *bp;
 102         u_char  *cp;
 103         int     dospart;
 104         struct dos_partition *dp;
 105         struct dos_partition *dp0;
 106         struct dos_partition dpcopy[NDOSPART];
 107         int     error;
 108         int     max_ncyls;
 109         int     max_nsectors;
 110         int     max_ntracks;
 111         u_int64_t mbr_offset;
 112         char    partname[2];
 113         u_long  secpercyl;
 114         char    *sname = "tempname";
 115         struct diskslice *sp;
 116         struct diskslices *ssp;
 117         cdev_t wdev;
 118
 119         mbr_offset = DOSBBSECTOR;
 120 reread_mbr:
 121         /*
 122          * Don't bother if the block size is weird or the
 123          * media size is 0 (probably means no media present).
 124          */
 125         if (info->d_media_blksize & DEV_BMASK)
 126                 return (EIO);
 127         if (info->d_media_size == 0)
 128                 return (EIO);
 129
 130         /*
 131          * Read master boot record.
 132          */
 133         wdev = dev;
 134         bp = geteblk((int)info->d_media_blksize);
 135         bp->b_bio1.bio_offset = (off_t)mbr_offset * info->d_media_blksize;
 136         bp->b_bio1.bio_done = biodone_sync;
 137         bp->b_bio1.bio_flags |= BIO_SYNC;
 138         bp->b_bcount = info->d_media_blksize;
 139         bp->b_cmd = BUF_CMD_READ;
 140         dev_dstrategy(wdev, &bp->b_bio1);
 141         if (biowait(&bp->b_bio1, "mbrrd") != 0) {
 142                 if ((info->d_dsflags & DSO_MBRQUIET) == 0) {
 143                         diskerr(&bp->b_bio1, wdev,
 144                                 "reading primary partition table: error",
 145                                 LOG_PRINTF, 0);
 146                         kprintf("\n");
 147                 }
 148                 error = EIO;
 149                 goto done;
 150         }
 151
 152         /* Weakly verify it. */
 153         cp = bp->b_data;
 154         sname = dsname(dev, 0, 0, 0, NULL);
 155         if (cp[0x1FE] != 0x55 || cp[0x1FF] != 0xAA) {
 156                 if (bootverbose)
 157                         kprintf("%s: invalid primary partition table: no magic\n",
 158                                sname);
 159                 error = EINVAL;
 160                 goto done;
 161         }
 162
 163         /* Make a copy of the partition table to avoid alignment problems. */
 164         memcpy(&dpcopy[0], cp + DOSPARTOFF, sizeof(dpcopy));
 165
 166         dp0 = &dpcopy[0];
 167
 168         /*
 169          * Check for "Ontrack Diskmanager" or GPT.  If a GPT is found in
 170          * the first dos partition, ignore the rest of the MBR and go
 171          * to GPT processing.
 172          */
 173         for (dospart = 0, dp = dp0; dospart < NDOSPART; dospart++, dp++) {
 174                 if (dospart == 0 &&
 175                     (dp->dp_typ == DOSPTYP_PMBR || dp->dp_typ == DOSPTYP_GPT)) {
 176                         if (bootverbose)
 177                                 kprintf(
 178             "%s: Found GPT in slice #%d\n", sname, dospart + 1);
 179                         error = gptinit(dev, info, sspp);
 180                         goto done;
 181                 }
 182
 183                 if (dp->dp_typ == DOSPTYP_ONTRACK) {
 184                         if (bootverbose)
 185                                 kprintf(
 186             "%s: Found \"Ontrack Disk Manager\" on this disk.\n", sname);
 187                         bp->b_flags |= B_INVAL | B_AGE;
 188                         brelse(bp);
 189                         mbr_offset = 63;
 190                         goto reread_mbr;
 191                 }
 192         }
 193
 194         if (bcmp(dp0, historical_bogus_partition_table,
 195                  sizeof historical_bogus_partition_table) == 0 ||
 196             bcmp(dp0, historical_bogus_partition_table_fixed,
 197                  sizeof historical_bogus_partition_table_fixed) == 0) {
 198 #if 0
 199                 TRACE(("%s: invalid primary partition table: historical\n",
 200                        sname));
 201 #endif /* 0 */
 202                 if (bootverbose)
 203                         kprintf(
 204      "%s: invalid primary partition table: Dangerously Dedicated (ignored)\n",
 205                                sname);
 206                 error = EINVAL;
 207                 goto done;
 208         }
 209
 210         /* Guess the geometry. */
 211         /*
 212          * TODO:
 213          * Perhaps skip entries with 0 size.
 214          * Perhaps only look at entries of type DOSPTYP_386BSD.
 215          */
 216         max_ncyls = 0;
 217         max_nsectors = 0;
 218         max_ntracks = 0;
 219         for (dospart = 0, dp = dp0; dospart < NDOSPART; dospart++, dp++) {
 220                 int     ncyls;
 221                 int     nsectors;
 222                 int     ntracks;
 223
 224                 ncyls = DPCYL(dp->dp_ecyl, dp->dp_esect) + 1;
 225                 if (max_ncyls < ncyls)
 226                         max_ncyls = ncyls;
 227                 nsectors = DPSECT(dp->dp_esect);
 228                 if (max_nsectors < nsectors)
 229                         max_nsectors = nsectors;
 230                 ntracks = dp->dp_ehd + 1;
 231                 if (max_ntracks < ntracks)
 232                         max_ntracks = ntracks;
 233         }
 234
 235         /*
 236          * Check that we have guessed the geometry right by checking the
 237          * partition entries.
 238          */
 239         /*
 240          * TODO:
 241          * As above.
 242          * Check for overlaps.
 243          * Check against d_secperunit if the latter is reliable.
 244          */
 245         error = 0;
 246         for (dospart = 0, dp = dp0; dospart < NDOSPART; dospart++, dp++) {
 247                 if (dp->dp_scyl == 0 && dp->dp_shd == 0 && dp->dp_ssect == 0
 248                     && dp->dp_start == 0 && dp->dp_size == 0)
 249                         continue;
 250                 //sname = dsname(dev, dkunit(dev), BASE_SLICE + dospart,
 251                 //             WHOLE_SLICE_PART, partname);
 252
 253                 /*
 254                  * Temporarily ignore errors from this check.  We could
 255                  * simplify things by accepting the table eariler if we
 256                  * always ignore errors here.  Perhaps we should always
 257                  * accept the table if the magic is right but not let
 258                  * bad entries affect the geometry.
 259                  */
 260                 check_part(sname, dp, mbr_offset, max_nsectors, max_ntracks,
 261                            mbr_offset);
 262         }
 263         if (error != 0)
 264                 goto done;
 265
 266         /*
 267          * Accept the DOS partition table.
 268          *
 269          * Adjust the disk information structure with updated CHS
 270          * conversion parameters, but only use values extracted from
 271          * the primary partition table.
 272          *
 273          * NOTE!  Regardless of our having to deal with this old cruft,
 274          * we do not screw around with the info->d_media* parameters.
 275          */
 276         secpercyl = (u_long)max_nsectors * max_ntracks;
 277         if (secpercyl != 0 && mbr_offset == DOSBBSECTOR) {
 278                 info->d_secpertrack = max_nsectors;
 279                 info->d_nheads = max_ntracks;
 280                 info->d_secpercyl = secpercyl;
 281                 info->d_ncylinders = info->d_media_blocks / secpercyl;
 282         }
 283
 284         /*
 285          * We are passed a pointer to a suitably initialized minimal
 286          * slices "struct" with no dangling pointers in it.  Replace it
 287          * by a maximal one.  This usually oversizes the "struct", but
 288          * enlarging it while searching for logical drives would be
 289          * inconvenient.
 290          */
 291         kfree(*sspp, M_DEVBUF);
 292         ssp = dsmakeslicestruct(MAX_SLICES, info);
 293         *sspp = ssp;
 294
 295         /* Initialize normal slices. */
 296         sp = &ssp->dss_slices[BASE_SLICE];
 297         for (dospart = 0, dp = dp0; dospart < NDOSPART; dospart++, dp++, sp++) {
 298                 sname = dsname(dev, dkunit(dev), BASE_SLICE + dospart,
 299                                WHOLE_SLICE_PART, partname);
 300                 (void)mbr_setslice(sname, info, sp, dp, mbr_offset);
 301         }
 302         ssp->dss_nslices = BASE_SLICE + NDOSPART;
 303
 304         /* Handle extended partitions. */
 305         sp -= NDOSPART;
 306         for (dospart = 0; dospart < NDOSPART; dospart++, sp++) {
 307                 if (sp->ds_type == DOSPTYP_EXTENDED ||
 308                     sp->ds_type == DOSPTYP_EXTENDEDX) {
 309                         mbr_extended(wdev, info, ssp,
 310                                      sp->ds_offset, sp->ds_size, sp->ds_offset,
 311                                      max_nsectors, max_ntracks, mbr_offset, 1);
 312                 }
 313         }
 314
 315         /*
 316          * mbr_extended() abuses ssp->dss_nslices for the number of slices
 317          * that would be found if there were no limit on the number of slices
 318          * in *ssp.  Cut it back now.
 319          */
 320         if (ssp->dss_nslices > MAX_SLICES)
 321                 ssp->dss_nslices = MAX_SLICES;
 322
 323 done:
 324         bp->b_flags |= B_INVAL | B_AGE;
 325         brelse(bp);
 326         if (error == EINVAL)
 327                 error = 0;
 328         return (error);
 329 }
 330
 331 static int
 332 check_part(char *sname, struct dos_partition *dp, u_int64_t offset,
 333             int nsectors, int ntracks, u_int64_t mbr_offset)
 334 {
 335         int     chs_ecyl;
 336         int     chs_esect;
 337         int     chs_scyl;
 338         int     chs_ssect;
 339         int     error;
 340         u_long  secpercyl;
 341         u_int64_t esector;
 342         u_int64_t esector1;
 343         u_int64_t ssector;
 344         u_int64_t ssector1;
 345
 346         secpercyl = (u_long)nsectors * ntracks;
 347         chs_scyl = DPCYL(dp->dp_scyl, dp->dp_ssect);
 348         chs_ssect = DPSECT(dp->dp_ssect);
 349         ssector = chs_ssect - 1 + dp->dp_shd * nsectors + chs_scyl * secpercyl
 350                   + mbr_offset;
 351         ssector1 = offset + dp->dp_start;
 352
 353         /*
 354          * If ssector1 is on a cylinder >= 1024, then ssector can't be right.
 355          * Allow the C/H/S for it to be 1023/ntracks-1/nsectors, or correct
 356          * apart from the cylinder being reduced modulo 1024.  Always allow
 357          * 1023/255/63, because this is the official way to represent
 358          * pure-LBA for the starting position.
 359          */
 360         if ((ssector < ssector1
 361              && ((chs_ssect == nsectors && dp->dp_shd == ntracks - 1
 362                   && chs_scyl == 1023)
 363                  || (secpercyl != 0
 364                      && (ssector1 - ssector) % (1024 * secpercyl) == 0)))
 365             || (dp->dp_scyl == 255 && dp->dp_shd == 255
 366                 && dp->dp_ssect == 255)) {
 367                 TRACE(("%s: C/H/S start %d/%d/%d, start %llu: allow\n",
 368                        sname, chs_scyl, dp->dp_shd, chs_ssect,
 369                        (long long)ssector1));
 370                 ssector = ssector1;
 371         }
 372
 373         chs_ecyl = DPCYL(dp->dp_ecyl, dp->dp_esect);
 374         chs_esect = DPSECT(dp->dp_esect);
 375         esector = chs_esect - 1 + dp->dp_ehd * nsectors + chs_ecyl * secpercyl
 376                   + mbr_offset;
 377         esector1 = ssector1 + dp->dp_size - 1;
 378
 379         /*
 380          * Allow certain bogus C/H/S values for esector, as above. However,
 381          * heads == 255 isn't really legal and causes some BIOS crashes. The
 382          * correct value to indicate a pure-LBA end is 1023/heads-1/sectors -
 383          * usually 1023/254/63. "heads" is base 0, "sectors" is base 1.
 384          */
 385         if ((esector < esector1
 386              && ((chs_esect == nsectors && dp->dp_ehd == ntracks - 1
 387                   && chs_ecyl == 1023)
 388                  || (secpercyl != 0
 389                      && (esector1 - esector) % (1024 * secpercyl) == 0)))
 390             || (dp->dp_ecyl == 255 && dp->dp_ehd == 255
 391                 && dp->dp_esect == 255)) {
 392                 TRACE(("%s: C/H/S end %d/%d/%d, end %llu: allow\n",
 393                        sname, chs_ecyl, dp->dp_ehd, chs_esect,
 394                        (long long)esector1));
 395                 esector = esector1;
 396         }
 397
 398         error = (ssector == ssector1 && esector == esector1) ? 0 : EINVAL;
 399         if (bootverbose)
 400                 kprintf("%s: type 0x%x, start %llu, end = %llu, size %u %s\n",
 401                        sname, dp->dp_typ,
 402                        (long long)ssector1, (long long)esector1,
 403                        dp->dp_size, (error ? "" : ": OK"));
 404         if (ssector != ssector1 && bootverbose)
 405                 kprintf("%s: C/H/S start %d/%d/%d (%llu) != start %llu: invalid\n",
 406                        sname, chs_scyl, dp->dp_shd, chs_ssect,
 407                        (long long)ssector, (long long)ssector1);
 408         if (esector != esector1 && bootverbose)
 409                 kprintf("%s: C/H/S end %d/%d/%d (%llu) != end %llu: invalid\n",
 410                        sname, chs_ecyl, dp->dp_ehd, chs_esect,
 411                        (long long)esector, (long long)esector1);
 412         return (error);
 413 }
 414
 415 static
 416 void
 417 mbr_extended(cdev_t dev, struct disk_info *info, struct diskslices *ssp,
 418             u_int64_t ext_offset, u_int64_t ext_size, u_int64_t base_ext_offset,
 419             int nsectors, int ntracks, u_int64_t mbr_offset, int level)
 420 {
 421         struct buf *bp;
 422         u_char  *cp;
 423         int     dospart;
 424         struct dos_partition *dp;
 425         struct dos_partition dpcopy[NDOSPART];
 426         u_int64_t ext_offsets[NDOSPART];
 427         u_int64_t ext_sizes[NDOSPART];
 428         char    partname[2];
 429         int     slice;
 430         char    *sname;
 431         struct diskslice *sp;
 432
 433         if (level >= 16) {
 434                 kprintf(
 435         "%s: excessive recursion in search for slices; aborting search\n",
 436                        devtoname(dev));
 437                 return;
 438         }
 439
 440         /* Read extended boot record. */
 441         bp = geteblk((int)info->d_media_blksize);
 442         bp->b_bio1.bio_offset = (off_t)ext_offset * info->d_media_blksize;
 443         bp->b_bio1.bio_done = biodone_sync;
 444         bp->b_bio1.bio_flags |= BIO_SYNC;
 445         bp->b_bcount = info->d_media_blksize;
 446         bp->b_cmd = BUF_CMD_READ;
 447         dev_dstrategy(dev, &bp->b_bio1);
 448         if (biowait(&bp->b_bio1, "mbrrd") != 0) {
 449                 diskerr(&bp->b_bio1, dev,
 450                         "reading extended partition table: error",
 451                         LOG_PRINTF, 0);
 452                 kprintf("\n");
 453                 goto done;
 454         }
 455
 456         /* Weakly verify it. */
 457         cp = bp->b_data;
 458         if (cp[0x1FE] != 0x55 || cp[0x1FF] != 0xAA) {
 459                 sname = dsname(dev, dkunit(dev), WHOLE_DISK_SLICE, WHOLE_SLICE_PART,
 460                                partname);
 461                 if (bootverbose)
 462                         kprintf("%s: invalid extended partition table: no magic\n",
 463                                sname);
 464                 goto done;
 465         }
 466
 467         /* Make a copy of the partition table to avoid alignment problems. */
 468         memcpy(&dpcopy[0], cp + DOSPARTOFF, sizeof(dpcopy));
 469
 470         slice = ssp->dss_nslices;
 471         for (dospart = 0, dp = &dpcopy[0]; dospart < NDOSPART;
 472             dospart++, dp++) {
 473                 ext_sizes[dospart] = 0;
 474                 if (dp->dp_scyl == 0 && dp->dp_shd == 0 && dp->dp_ssect == 0
 475                     && dp->dp_start == 0 && dp->dp_size == 0)
 476                         continue;
 477                 if (dp->dp_typ == DOSPTYP_EXTENDED ||
 478                     dp->dp_typ == DOSPTYP_EXTENDEDX) {
 479                         static char buf[32];
 480
 481                         sname = dsname(dev, dkunit(dev), WHOLE_DISK_SLICE,
 482                                        WHOLE_SLICE_PART, partname);
 483                         ksnprintf(buf, sizeof(buf), "%s", sname);
 484                         if (strlen(buf) < sizeof buf - 11)
 485                                 strcat(buf, "<extended>");
 486                         check_part(buf, dp, base_ext_offset, nsectors,
 487                                    ntracks, mbr_offset);
 488                         ext_offsets[dospart] = base_ext_offset + dp->dp_start;
 489                         ext_sizes[dospart] = dp->dp_size;
 490                 } else {
 491                         sname = dsname(dev, dkunit(dev), slice, WHOLE_SLICE_PART,
 492                                        partname);
 493                         check_part(sname, dp, ext_offset, nsectors, ntracks,
 494                                    mbr_offset);
 495                         if (slice >= MAX_SLICES) {
 496                                 kprintf("%s: too many slices\n", sname);
 497                                 slice++;
 498                                 continue;
 499                         }
 500                         sp = &ssp->dss_slices[slice];
 501                         if (mbr_setslice(sname, info, sp, dp, ext_offset) != 0)
 502                                 continue;
 503                         slice++;
 504                 }
 505         }
 506         ssp->dss_nslices = slice;
 507
 508         /* If we found any more slices, recursively find all the subslices. */
 509         for (dospart = 0; dospart < NDOSPART; dospart++) {
 510                 if (ext_sizes[dospart] != 0) {
 511                         mbr_extended(dev, info, ssp, ext_offsets[dospart],
 512                                      ext_sizes[dospart], base_ext_offset,
 513                                      nsectors, ntracks, mbr_offset, ++level);
 514                 }
 515         }
 516
 517 done:
 518         bp->b_flags |= B_INVAL | B_AGE;
 519         brelse(bp);
 520 }
 521
 522 static int
 523 mbr_setslice(char *sname, struct disk_info *info, struct diskslice *sp,
 524             struct dos_partition *dp, u_int64_t br_offset)
 525 {
 526         u_int64_t       offset;
 527         u_int64_t       size;
 528
 529         offset = br_offset + dp->dp_start;
 530         if (offset > info->d_media_blocks || offset < br_offset) {
 531                 kprintf(
 532                 "%s: slice starts beyond end of the disk: rejecting it\n",
 533                        sname);
 534                 return (1);
 535         }
 536         size = info->d_media_blocks - offset;
 537         if (size >= dp->dp_size) {
 538                 if (dp->dp_size == 0xFFFFFFFFU) {
 539                         kprintf("%s: slice >2TB, using media size instead "
 540                                 "of slice table size\n", sname);
 541                 } else {
 542                         size = dp->dp_size;
 543                 }
 544         } else {
 545                 kprintf("%s: slice extends beyond end of disk: "
 546                         "truncating from %u to %llu sectors\n",
 547                         sname, dp->dp_size, (unsigned long long)size);
 548         }
 549         sp->ds_offset = offset;
 550         sp->ds_size = size;
 551         sp->ds_type = dp->dp_typ;
 552         bzero(&sp->ds_type_uuid, sizeof(sp->ds_type_uuid));
 553         bzero(&sp->ds_stor_uuid, sizeof(sp->ds_type_uuid));
 554
 555         /*
 556          * Slices do not overlap with the parent (if any).
 557          */
 558         sp->ds_reserved = 0;
 559         return (0);
 560 }