block/dmg.c

   1 /*
   2  * QEMU Block driver for DMG images
   3  *
   4  * Copyright (c) 2004 Johannes E. Schindelin
   5  *
   6  * Permission is hereby granted, free of charge, to any person obtaining a copy
   7  * of this software and associated documentation files (the "Software"), to deal
   8  * in the Software without restriction, including without limitation the rights
   9  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  10  * copies of the Software, and to permit persons to whom the Software is
  11  * furnished to do so, subject to the following conditions:
  12  *
  13  * The above copyright notice and this permission notice shall be included in
  14  * all copies or substantial portions of the Software.
  15  *
  16  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  17  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  18  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
  19  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  20  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  21  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  22  * THE SOFTWARE.
  23  */
  24 #include "qemu-common.h"
  25 #include "block/block_int.h"
  26 #include "qemu/bswap.h"
  27 #include "qemu/module.h"
  28 #include <zlib.h>
  29 #ifdef CONFIG_BZIP2
  30 #include <bzlib.h>
  31 #endif
  32 #include <glib.h>
  33
  34 enum {
  35     /* Limit chunk sizes to prevent unreasonable amounts of memory being used
  36      * or truncating when converting to 32-bit types
  37      */
  38     DMG_LENGTHS_MAX = 64 * 1024 * 1024, /* 64 MB */
  39     DMG_SECTORCOUNTS_MAX = DMG_LENGTHS_MAX / 512,
  40 };
  41
  42 typedef struct BDRVDMGState {
  43     CoMutex lock;
  44     /* each chunk contains a certain number of sectors,
  45      * offsets[i] is the offset in the .dmg file,
  46      * lengths[i] is the length of the compressed chunk,
  47      * sectors[i] is the sector beginning at offsets[i],
  48      * sectorcounts[i] is the number of sectors in that chunk,
  49      * the sectors array is ordered
  50      * 0<=i<n_chunks */
  51
  52     uint32_t n_chunks;
  53     uint32_t* types;
  54     uint64_t* offsets;
  55     uint64_t* lengths;
  56     uint64_t* sectors;
  57     uint64_t* sectorcounts;
  58     uint32_t current_chunk;
  59     uint8_t *compressed_chunk;
  60     uint8_t *uncompressed_chunk;
  61     z_stream zstream;
  62 #ifdef CONFIG_BZIP2
  63     bz_stream bzstream;
  64 #endif
  65 } BDRVDMGState;
  66
  67 static int dmg_probe(const uint8_t *buf, int buf_size, const char *filename)
  68 {
  69     int len;
  70
  71     if (!filename) {
  72         return 0;
  73     }
  74
  75     len = strlen(filename);
  76     if (len > 4 && !strcmp(filename + len - 4, ".dmg")) {
  77         return 2;
  78     }
  79     return 0;
  80 }
  81
  82 static int read_uint64(BlockDriverState *bs, int64_t offset, uint64_t *result)
  83 {
  84     uint64_t buffer;
  85     int ret;
  86
  87     ret = bdrv_pread(bs->file, offset, &buffer, 8);
  88     if (ret < 0) {
  89         return ret;
  90     }
  91
  92     *result = be64_to_cpu(buffer);
  93     return 0;
  94 }
  95
  96 static int read_uint32(BlockDriverState *bs, int64_t offset, uint32_t *result)
  97 {
  98     uint32_t buffer;
  99     int ret;
 100
 101     ret = bdrv_pread(bs->file, offset, &buffer, 4);
 102     if (ret < 0) {
 103         return ret;
 104     }
 105
 106     *result = be32_to_cpu(buffer);
 107     return 0;
 108 }
 109
 110 static inline uint64_t buff_read_uint64(const uint8_t *buffer, int64_t offset)
 111 {
 112     return be64_to_cpu(*(uint64_t *)&buffer[offset]);
 113 }
 114
 115 static inline uint32_t buff_read_uint32(const uint8_t *buffer, int64_t offset)
 116 {
 117     return be32_to_cpu(*(uint32_t *)&buffer[offset]);
 118 }
 119
 120 /* Increase max chunk sizes, if necessary.  This function is used to calculate
 121  * the buffer sizes needed for compressed/uncompressed chunk I/O.
 122  */
 123 static void update_max_chunk_size(BDRVDMGState *s, uint32_t chunk,
 124                                   uint32_t *max_compressed_size,
 125                                   uint32_t *max_sectors_per_chunk)
 126 {
 127     uint32_t compressed_size = 0;
 128     uint32_t uncompressed_sectors = 0;
 129
 130     switch (s->types[chunk]) {
 131     case 0x80000005: /* zlib compressed */
 132     case 0x80000006: /* bzip2 compressed */
 133         compressed_size = s->lengths[chunk];
 134         uncompressed_sectors = s->sectorcounts[chunk];
 135         break;
 136     case 1: /* copy */
 137         uncompressed_sectors = (s->lengths[chunk] + 511) / 512;
 138         break;
 139     case 2: /* zero */
 140         /* as the all-zeroes block may be large, it is treated specially: the
 141          * sector is not copied from a large buffer, a simple memset is used
 142          * instead. Therefore uncompressed_sectors does not need to be set. */
 143         break;
 144     }
 145
 146     if (compressed_size > *max_compressed_size) {
 147         *max_compressed_size = compressed_size;
 148     }
 149     if (uncompressed_sectors > *max_sectors_per_chunk) {
 150         *max_sectors_per_chunk = uncompressed_sectors;
 151     }
 152 }
 153
 154 static int64_t dmg_find_koly_offset(BlockDriverState *file_bs, Error **errp)
 155 {
 156     int64_t length;
 157     int64_t offset = 0;
 158     uint8_t buffer[515];
 159     int i, ret;
 160
 161     /* bdrv_getlength returns a multiple of block size (512), rounded up. Since
 162      * dmg images can have odd sizes, try to look for the "koly" magic which
 163      * marks the begin of the UDIF trailer (512 bytes). This magic can be found
 164      * in the last 511 bytes of the second-last sector or the first 4 bytes of
 165      * the last sector (search space: 515 bytes) */
 166     length = bdrv_getlength(file_bs);
 167     if (length < 0) {
 168         error_setg_errno(errp, -length,
 169             "Failed to get file size while reading UDIF trailer");
 170         return length;
 171     } else if (length < 512) {
 172         error_setg(errp, "dmg file must be at least 512 bytes long");
 173         return -EINVAL;
 174     }
 175     if (length > 511 + 512) {
 176         offset = length - 511 - 512;
 177     }
 178     length = length < 515 ? length : 515;
 179     ret = bdrv_pread(file_bs, offset, buffer, length);
 180     if (ret < 0) {
 181         error_setg_errno(errp, -ret, "Failed while reading UDIF trailer");
 182         return ret;
 183     }
 184     for (i = 0; i < length - 3; i++) {
 185         if (buffer[i] == 'k' && buffer[i+1] == 'o' &&
 186             buffer[i+2] == 'l' && buffer[i+3] == 'y') {
 187             return offset + i;
 188         }
 189     }
 190     error_setg(errp, "Could not locate UDIF trailer in dmg file");
 191     return -EINVAL;
 192 }
 193
 194 /* used when building the sector table */
 195 typedef struct DmgHeaderState {
 196     /* used internally by dmg_read_mish_block to remember offsets of blocks
 197      * across calls */
 198     uint64_t data_fork_offset;
 199     /* exported for dmg_open */
 200     uint32_t max_compressed_size;
 201     uint32_t max_sectors_per_chunk;
 202 } DmgHeaderState;
 203
 204 static bool dmg_is_known_block_type(uint32_t entry_type)
 205 {
 206     switch (entry_type) {
 207     case 0x00000001:    /* uncompressed */
 208     case 0x00000002:    /* zeroes */
 209     case 0x80000005:    /* zlib */
 210 #ifdef CONFIG_BZIP2
 211     case 0x80000006:    /* bzip2 */
 212 #endif
 213         return true;
 214     default:
 215         return false;
 216     }
 217 }
 218
 219 static int dmg_read_mish_block(BDRVDMGState *s, DmgHeaderState *ds,
 220                                uint8_t *buffer, uint32_t count)
 221 {
 222     uint32_t type, i;
 223     int ret;
 224     size_t new_size;
 225     uint32_t chunk_count;
 226     int64_t offset = 0;
 227     uint64_t data_offset;
 228     uint64_t in_offset = ds->data_fork_offset;
 229     uint64_t out_offset;
 230
 231     type = buff_read_uint32(buffer, offset);
 232     /* skip data that is not a valid MISH block (invalid magic or too small) */
 233     if (type != 0x6d697368 || count < 244) {
 234         /* assume success for now */
 235         return 0;
 236     }
 237
 238     /* chunk offsets are relative to this sector number */
 239     out_offset = buff_read_uint64(buffer, offset + 8);
 240
 241     /* location in data fork for (compressed) blob (in bytes) */
 242     data_offset = buff_read_uint64(buffer, offset + 0x18);
 243     in_offset += data_offset;
 244
 245     /* move to begin of chunk entries */
 246     offset += 204;
 247
 248     chunk_count = (count - 204) / 40;
 249     new_size = sizeof(uint64_t) * (s->n_chunks + chunk_count);
 250     s->types = g_realloc(s->types, new_size / 2);
 251     s->offsets = g_realloc(s->offsets, new_size);
 252     s->lengths = g_realloc(s->lengths, new_size);
 253     s->sectors = g_realloc(s->sectors, new_size);
 254     s->sectorcounts = g_realloc(s->sectorcounts, new_size);
 255
 256     for (i = s->n_chunks; i < s->n_chunks + chunk_count; i++) {
 257         s->types[i] = buff_read_uint32(buffer, offset);
 258         if (!dmg_is_known_block_type(s->types[i])) {
 259             chunk_count--;
 260             i--;
 261             offset += 40;
 262             continue;
 263         }
 264
 265         /* sector number */
 266         s->sectors[i] = buff_read_uint64(buffer, offset + 8);
 267         s->sectors[i] += out_offset;
 268
 269         /* sector count */
 270         s->sectorcounts[i] = buff_read_uint64(buffer, offset + 0x10);
 271
 272         /* all-zeroes sector (type 2) does not need to be "uncompressed" and can
 273          * therefore be unbounded. */
 274         if (s->types[i] != 2 && s->sectorcounts[i] > DMG_SECTORCOUNTS_MAX) {
 275             error_report("sector count %" PRIu64 " for chunk %" PRIu32
 276                          " is larger than max (%u)",
 277                          s->sectorcounts[i], i, DMG_SECTORCOUNTS_MAX);
 278             ret = -EINVAL;
 279             goto fail;
 280         }
 281
 282         /* offset in (compressed) data fork */
 283         s->offsets[i] = buff_read_uint64(buffer, offset + 0x18);
 284         s->offsets[i] += in_offset;
 285
 286         /* length in (compressed) data fork */
 287         s->lengths[i] = buff_read_uint64(buffer, offset + 0x20);
 288
 289         if (s->lengths[i] > DMG_LENGTHS_MAX) {
 290             error_report("length %" PRIu64 " for chunk %" PRIu32
 291                          " is larger than max (%u)",
 292                          s->lengths[i], i, DMG_LENGTHS_MAX);
 293             ret = -EINVAL;
 294             goto fail;
 295         }
 296
 297         update_max_chunk_size(s, i, &ds->max_compressed_size,
 298                               &ds->max_sectors_per_chunk);
 299         offset += 40;
 300     }
 301     s->n_chunks += chunk_count;
 302     return 0;
 303
 304 fail:
 305     return ret;
 306 }
 307
 308 static int dmg_read_resource_fork(BlockDriverState *bs, DmgHeaderState *ds,
 309                                   uint64_t info_begin, uint64_t info_length)
 310 {
 311     BDRVDMGState *s = bs->opaque;
 312     int ret;
 313     uint32_t count, rsrc_data_offset;
 314     uint8_t *buffer = NULL;
 315     uint64_t info_end;
 316     uint64_t offset;
 317
 318     /* read offset from begin of resource fork (info_begin) to resource data */
 319     ret = read_uint32(bs, info_begin, &rsrc_data_offset);
 320     if (ret < 0) {
 321         goto fail;
 322     } else if (rsrc_data_offset > info_length) {
 323         ret = -EINVAL;
 324         goto fail;
 325     }
 326
 327     /* read length of resource data */
 328     ret = read_uint32(bs, info_begin + 8, &count);
 329     if (ret < 0) {
 330         goto fail;
 331     } else if (count == 0 || rsrc_data_offset + count > info_length) {
 332         ret = -EINVAL;
 333         goto fail;
 334     }
 335
 336     /* begin of resource data (consisting of one or more resources) */
 337     offset = info_begin + rsrc_data_offset;
 338
 339     /* end of resource data (there is possibly a following resource map
 340      * which will be ignored). */
 341     info_end = offset + count;
 342
 343     /* read offsets (mish blocks) from one or more resources in resource data */
 344     while (offset < info_end) {
 345         /* size of following resource */
 346         ret = read_uint32(bs, offset, &count);
 347         if (ret < 0) {
 348             goto fail;
 349         } else if (count == 0 || count > info_end - offset) {
 350             ret = -EINVAL;
 351             goto fail;
 352         }
 353         offset += 4;
 354
 355         buffer = g_realloc(buffer, count);
 356         ret = bdrv_pread(bs->file, offset, buffer, count);
 357         if (ret < 0) {
 358             goto fail;
 359         }
 360
 361         ret = dmg_read_mish_block(s, ds, buffer, count);
 362         if (ret < 0) {
 363             goto fail;
 364         }
 365         /* advance offset by size of resource */
 366         offset += count;
 367     }
 368     ret = 0;
 369
 370 fail:
 371     g_free(buffer);
 372     return ret;
 373 }
 374
 375 static int dmg_read_plist_xml(BlockDriverState *bs, DmgHeaderState *ds,
 376                               uint64_t info_begin, uint64_t info_length)
 377 {
 378     BDRVDMGState *s = bs->opaque;
 379     int ret;
 380     uint8_t *buffer = NULL;
 381     char *data_begin, *data_end;
 382
 383     /* Have at least some length to avoid NULL for g_malloc. Attempt to set a
 384      * safe upper cap on the data length. A test sample had a XML length of
 385      * about 1 MiB. */
 386     if (info_length == 0 || info_length > 16 * 1024 * 1024) {
 387         ret = -EINVAL;
 388         goto fail;
 389     }
 390
 391     buffer = g_malloc(info_length + 1);
 392     buffer[info_length] = '\0';
 393     ret = bdrv_pread(bs->file, info_begin, buffer, info_length);
 394     if (ret != info_length) {
 395         ret = -EINVAL;
 396         goto fail;
 397     }
 398
 399     /* look for <data>...</data>. The data is 284 (0x11c) bytes after base64
 400      * decode. The actual data element has 431 (0x1af) bytes which includes tabs
 401      * and line feeds. */
 402     data_end = (char *)buffer;
 403     while ((data_begin = strstr(data_end, "<data>")) != NULL) {
 404         guchar *mish;
 405         gsize out_len = 0;
 406
 407         data_begin += 6;
 408         data_end = strstr(data_begin, "</data>");
 409         /* malformed XML? */
 410         if (data_end == NULL) {
 411             ret = -EINVAL;
 412             goto fail;
 413         }
 414         *data_end++ = '\0';
 415         mish = g_base64_decode(data_begin, &out_len);
 416         ret = dmg_read_mish_block(s, ds, mish, (uint32_t)out_len);
 417         g_free(mish);
 418         if (ret < 0) {
 419             goto fail;
 420         }
 421     }
 422     ret = 0;
 423
 424 fail:
 425     g_free(buffer);
 426     return ret;
 427 }
 428
 429 static int dmg_open(BlockDriverState *bs, QDict *options, int flags,
 430                     Error **errp)
 431 {
 432     BDRVDMGState *s = bs->opaque;
 433     DmgHeaderState ds;
 434     uint64_t rsrc_fork_offset, rsrc_fork_length;
 435     uint64_t plist_xml_offset, plist_xml_length;
 436     int64_t offset;
 437     int ret;
 438
 439     bs->read_only = 1;
 440     s->n_chunks = 0;
 441     s->offsets = s->lengths = s->sectors = s->sectorcounts = NULL;
 442     /* used by dmg_read_mish_block to keep track of the current I/O position */
 443     ds.data_fork_offset = 0;
 444     ds.max_compressed_size = 1;
 445     ds.max_sectors_per_chunk = 1;
 446
 447     /* locate the UDIF trailer */
 448     offset = dmg_find_koly_offset(bs->file, errp);
 449     if (offset < 0) {
 450         ret = offset;
 451         goto fail;
 452     }
 453
 454     /* offset of data fork (DataForkOffset) */
 455     ret = read_uint64(bs, offset + 0x18, &ds.data_fork_offset);
 456     if (ret < 0) {
 457         goto fail;
 458     } else if (ds.data_fork_offset > offset) {
 459         ret = -EINVAL;
 460         goto fail;
 461     }
 462
 463     /* offset of resource fork (RsrcForkOffset) */
 464     ret = read_uint64(bs, offset + 0x28, &rsrc_fork_offset);
 465     if (ret < 0) {
 466         goto fail;
 467     }
 468     ret = read_uint64(bs, offset + 0x30, &rsrc_fork_length);
 469     if (ret < 0) {
 470         goto fail;
 471     }
 472     if (rsrc_fork_offset >= offset ||
 473         rsrc_fork_length > offset - rsrc_fork_offset) {
 474         ret = -EINVAL;
 475         goto fail;
 476     }
 477     /* offset of property list (XMLOffset) */
 478     ret = read_uint64(bs, offset + 0xd8, &plist_xml_offset);
 479     if (ret < 0) {
 480         goto fail;
 481     }
 482     ret = read_uint64(bs, offset + 0xe0, &plist_xml_length);
 483     if (ret < 0) {
 484         goto fail;
 485     }
 486     if (plist_xml_offset >= offset ||
 487         plist_xml_length > offset - plist_xml_offset) {
 488         ret = -EINVAL;
 489         goto fail;
 490     }
 491     ret = read_uint64(bs, offset + 0x1ec, (uint64_t *)&bs->total_sectors);
 492     if (ret < 0) {
 493         goto fail;
 494     }
 495     if (bs->total_sectors < 0) {
 496         ret = -EINVAL;
 497         goto fail;
 498     }
 499     if (rsrc_fork_length != 0) {
 500         ret = dmg_read_resource_fork(bs, &ds,
 501                                      rsrc_fork_offset, rsrc_fork_length);
 502         if (ret < 0) {
 503             goto fail;
 504         }
 505     } else if (plist_xml_length != 0) {
 506         ret = dmg_read_plist_xml(bs, &ds, plist_xml_offset, plist_xml_length);
 507         if (ret < 0) {
 508             goto fail;
 509         }
 510     } else {
 511         ret = -EINVAL;
 512         goto fail;
 513     }
 514
 515     /* initialize zlib engine */
 516     s->compressed_chunk = qemu_try_blockalign(bs->file,
 517                                               ds.max_compressed_size + 1);
 518     s->uncompressed_chunk = qemu_try_blockalign(bs->file,
 519                                                 512 * ds.max_sectors_per_chunk);
 520     if (s->compressed_chunk == NULL || s->uncompressed_chunk == NULL) {
 521         ret = -ENOMEM;
 522         goto fail;
 523     }
 524
 525     if (inflateInit(&s->zstream) != Z_OK) {
 526         ret = -EINVAL;
 527         goto fail;
 528     }
 529
 530     s->current_chunk = s->n_chunks;
 531
 532     qemu_co_mutex_init(&s->lock);
 533     return 0;
 534
 535 fail:
 536     g_free(s->types);
 537     g_free(s->offsets);
 538     g_free(s->lengths);
 539     g_free(s->sectors);
 540     g_free(s->sectorcounts);
 541     qemu_vfree(s->compressed_chunk);
 542     qemu_vfree(s->uncompressed_chunk);
 543     return ret;
 544 }
 545
 546 static inline int is_sector_in_chunk(BDRVDMGState* s,
 547                 uint32_t chunk_num, uint64_t sector_num)
 548 {
 549     if (chunk_num >= s->n_chunks || s->sectors[chunk_num] > sector_num ||
 550             s->sectors[chunk_num] + s->sectorcounts[chunk_num] <= sector_num) {
 551         return 0;
 552     } else {
 553         return -1;
 554     }
 555 }
 556
 557 static inline uint32_t search_chunk(BDRVDMGState *s, uint64_t sector_num)
 558 {
 559     /* binary search */
 560     uint32_t chunk1 = 0, chunk2 = s->n_chunks, chunk3;
 561     while (chunk1 != chunk2) {
 562         chunk3 = (chunk1 + chunk2) / 2;
 563         if (s->sectors[chunk3] > sector_num) {
 564             chunk2 = chunk3;
 565         } else if (s->sectors[chunk3] + s->sectorcounts[chunk3] > sector_num) {
 566             return chunk3;
 567         } else {
 568             chunk1 = chunk3;
 569         }
 570     }
 571     return s->n_chunks; /* error */
 572 }
 573
 574 static inline int dmg_read_chunk(BlockDriverState *bs, uint64_t sector_num)
 575 {
 576     BDRVDMGState *s = bs->opaque;
 577
 578     if (!is_sector_in_chunk(s, s->current_chunk, sector_num)) {
 579         int ret;
 580         uint32_t chunk = search_chunk(s, sector_num);
 581 #ifdef CONFIG_BZIP2
 582         uint64_t total_out;
 583 #endif
 584
 585         if (chunk >= s->n_chunks) {
 586             return -1;
 587         }
 588
 589         s->current_chunk = s->n_chunks;
 590         switch (s->types[chunk]) { /* block entry type */
 591         case 0x80000005: { /* zlib compressed */
 592             /* we need to buffer, because only the chunk as whole can be
 593              * inflated. */
 594             ret = bdrv_pread(bs->file, s->offsets[chunk],
 595                              s->compressed_chunk, s->lengths[chunk]);
 596             if (ret != s->lengths[chunk]) {
 597                 return -1;
 598             }
 599
 600             s->zstream.next_in = s->compressed_chunk;
 601             s->zstream.avail_in = s->lengths[chunk];
 602             s->zstream.next_out = s->uncompressed_chunk;
 603             s->zstream.avail_out = 512 * s->sectorcounts[chunk];
 604             ret = inflateReset(&s->zstream);
 605             if (ret != Z_OK) {
 606                 return -1;
 607             }
 608             ret = inflate(&s->zstream, Z_FINISH);
 609             if (ret != Z_STREAM_END ||
 610                 s->zstream.total_out != 512 * s->sectorcounts[chunk]) {
 611                 return -1;
 612             }
 613             break; }
 614 #ifdef CONFIG_BZIP2
 615         case 0x80000006: /* bzip2 compressed */
 616             /* we need to buffer, because only the chunk as whole can be
 617              * inflated. */
 618             ret = bdrv_pread(bs->file, s->offsets[chunk],
 619                              s->compressed_chunk, s->lengths[chunk]);
 620             if (ret != s->lengths[chunk]) {
 621                 return -1;
 622             }
 623
 624             ret = BZ2_bzDecompressInit(&s->bzstream, 0, 0);
 625             if (ret != BZ_OK) {
 626                 return -1;
 627             }
 628             s->bzstream.next_in = (char *)s->compressed_chunk;
 629             s->bzstream.avail_in = (unsigned int) s->lengths[chunk];
 630             s->bzstream.next_out = (char *)s->uncompressed_chunk;
 631             s->bzstream.avail_out = (unsigned int) 512 * s->sectorcounts[chunk];
 632             ret = BZ2_bzDecompress(&s->bzstream);
 633             total_out = ((uint64_t)s->bzstream.total_out_hi32 << 32) +
 634                         s->bzstream.total_out_lo32;
 635             BZ2_bzDecompressEnd(&s->bzstream);
 636             if (ret != BZ_STREAM_END ||
 637                 total_out != 512 * s->sectorcounts[chunk]) {
 638                 return -1;
 639             }
 640             break;
 641 #endif /* CONFIG_BZIP2 */
 642         case 1: /* copy */
 643             ret = bdrv_pread(bs->file, s->offsets[chunk],
 644                              s->uncompressed_chunk, s->lengths[chunk]);
 645             if (ret != s->lengths[chunk]) {
 646                 return -1;
 647             }
 648             break;
 649         case 2: /* zero */
 650             /* see dmg_read, it is treated specially. No buffer needs to be
 651              * pre-filled, the zeroes can be set directly. */
 652             break;
 653         }
 654         s->current_chunk = chunk;
 655     }
 656     return 0;
 657 }
 658
 659 static int dmg_read(BlockDriverState *bs, int64_t sector_num,
 660                     uint8_t *buf, int nb_sectors)
 661 {
 662     BDRVDMGState *s = bs->opaque;
 663     int i;
 664
 665     for (i = 0; i < nb_sectors; i++) {
 666         uint32_t sector_offset_in_chunk;
 667         if (dmg_read_chunk(bs, sector_num + i) != 0) {
 668             return -1;
 669         }
 670         /* Special case: current chunk is all zeroes. Do not perform a memcpy as
 671          * s->uncompressed_chunk may be too small to cover the large all-zeroes
 672          * section. dmg_read_chunk is called to find s->current_chunk */
 673         if (s->types[s->current_chunk] == 2) { /* all zeroes block entry */
 674             memset(buf + i * 512, 0, 512);
 675             continue;
 676         }
 677         sector_offset_in_chunk = sector_num + i - s->sectors[s->current_chunk];
 678         memcpy(buf + i * 512,
 679                s->uncompressed_chunk + sector_offset_in_chunk * 512, 512);
 680     }
 681     return 0;
 682 }
 683
 684 static coroutine_fn int dmg_co_read(BlockDriverState *bs, int64_t sector_num,
 685                                     uint8_t *buf, int nb_sectors)
 686 {
 687     int ret;
 688     BDRVDMGState *s = bs->opaque;
 689     qemu_co_mutex_lock(&s->lock);
 690     ret = dmg_read(bs, sector_num, buf, nb_sectors);
 691     qemu_co_mutex_unlock(&s->lock);
 692     return ret;
 693 }
 694
 695 static void dmg_close(BlockDriverState *bs)
 696 {
 697     BDRVDMGState *s = bs->opaque;
 698
 699     g_free(s->types);
 700     g_free(s->offsets);
 701     g_free(s->lengths);
 702     g_free(s->sectors);
 703     g_free(s->sectorcounts);
 704     qemu_vfree(s->compressed_chunk);
 705     qemu_vfree(s->uncompressed_chunk);
 706
 707     inflateEnd(&s->zstream);
 708 }
 709
 710 static BlockDriver bdrv_dmg = {
 711     .format_name    = "dmg",
 712     .instance_size  = sizeof(BDRVDMGState),
 713     .bdrv_probe     = dmg_probe,
 714     .bdrv_open      = dmg_open,
 715     .bdrv_read      = dmg_co_read,
 716     .bdrv_close     = dmg_close,
 717 };
 718
 719 static void bdrv_dmg_init(void)
 720 {
 721     bdrv_register(&bdrv_dmg);
 722 }
 723
 724 block_init(bdrv_dmg_init);