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/osdep.h"
  25 #include "qapi/error.h"
  26 #include "qemu-common.h"
  27 #include "block/block_int.h"
  28 #include "qemu/bswap.h"
  29 #include "qemu/error-report.h"
  30 #include "qemu/module.h"
  31 #include <zlib.h>
  32 #ifdef CONFIG_BZIP2
  33 #include <bzlib.h>
  34 #endif
  35 #include <glib.h>
  36
  37 enum {
  38     /* Limit chunk sizes to prevent unreasonable amounts of memory being used
  39      * or truncating when converting to 32-bit types
  40      */
  41     DMG_LENGTHS_MAX = 64 * 1024 * 1024, /* 64 MB */
  42     DMG_SECTORCOUNTS_MAX = DMG_LENGTHS_MAX / 512,
  43 };
  44
  45 typedef struct BDRVDMGState {
  46     CoMutex lock;
  47     /* each chunk contains a certain number of sectors,
  48      * offsets[i] is the offset in the .dmg file,
  49      * lengths[i] is the length of the compressed chunk,
  50      * sectors[i] is the sector beginning at offsets[i],
  51      * sectorcounts[i] is the number of sectors in that chunk,
  52      * the sectors array is ordered
  53      * 0<=i<n_chunks */
  54
  55     uint32_t n_chunks;
  56     uint32_t* types;
  57     uint64_t* offsets;
  58     uint64_t* lengths;
  59     uint64_t* sectors;
  60     uint64_t* sectorcounts;
  61     uint32_t current_chunk;
  62     uint8_t *compressed_chunk;
  63     uint8_t *uncompressed_chunk;
  64     z_stream zstream;
  65 #ifdef CONFIG_BZIP2
  66     bz_stream bzstream;
  67 #endif
  68 } BDRVDMGState;
  69
  70 static int dmg_probe(const uint8_t *buf, int buf_size, const char *filename)
  71 {
  72     int len;
  73
  74     if (!filename) {
  75         return 0;
  76     }
  77
  78     len = strlen(filename);
  79     if (len > 4 && !strcmp(filename + len - 4, ".dmg")) {
  80         return 2;
  81     }
  82     return 0;
  83 }
  84
  85 static int read_uint64(BlockDriverState *bs, int64_t offset, uint64_t *result)
  86 {
  87     uint64_t buffer;
  88     int ret;
  89
  90     ret = bdrv_pread(bs->file->bs, offset, &buffer, 8);
  91     if (ret < 0) {
  92         return ret;
  93     }
  94
  95     *result = be64_to_cpu(buffer);
  96     return 0;
  97 }
  98
  99 static int read_uint32(BlockDriverState *bs, int64_t offset, uint32_t *result)
 100 {
 101     uint32_t buffer;
 102     int ret;
 103
 104     ret = bdrv_pread(bs->file->bs, offset, &buffer, 4);
 105     if (ret < 0) {
 106         return ret;
 107     }
 108
 109     *result = be32_to_cpu(buffer);
 110     return 0;
 111 }
 112
 113 static inline uint64_t buff_read_uint64(const uint8_t *buffer, int64_t offset)
 114 {
 115     return be64_to_cpu(*(uint64_t *)&buffer[offset]);
 116 }
 117
 118 static inline uint32_t buff_read_uint32(const uint8_t *buffer, int64_t offset)
 119 {
 120     return be32_to_cpu(*(uint32_t *)&buffer[offset]);
 121 }
 122
 123 /* Increase max chunk sizes, if necessary.  This function is used to calculate
 124  * the buffer sizes needed for compressed/uncompressed chunk I/O.
 125  */
 126 static void update_max_chunk_size(BDRVDMGState *s, uint32_t chunk,
 127                                   uint32_t *max_compressed_size,
 128                                   uint32_t *max_sectors_per_chunk)
 129 {
 130     uint32_t compressed_size = 0;
 131     uint32_t uncompressed_sectors = 0;
 132
 133     switch (s->types[chunk]) {
 134     case 0x80000005: /* zlib compressed */
 135     case 0x80000006: /* bzip2 compressed */
 136         compressed_size = s->lengths[chunk];
 137         uncompressed_sectors = s->sectorcounts[chunk];
 138         break;
 139     case 1: /* copy */
 140         uncompressed_sectors = (s->lengths[chunk] + 511) / 512;
 141         break;
 142     case 2: /* zero */
 143         /* as the all-zeroes block may be large, it is treated specially: the
 144          * sector is not copied from a large buffer, a simple memset is used
 145          * instead. Therefore uncompressed_sectors does not need to be set. */
 146         break;
 147     }
 148
 149     if (compressed_size > *max_compressed_size) {
 150         *max_compressed_size = compressed_size;
 151     }
 152     if (uncompressed_sectors > *max_sectors_per_chunk) {
 153         *max_sectors_per_chunk = uncompressed_sectors;
 154     }
 155 }
 156
 157 static int64_t dmg_find_koly_offset(BlockDriverState *file_bs, Error **errp)
 158 {
 159     int64_t length;
 160     int64_t offset = 0;
 161     uint8_t buffer[515];
 162     int i, ret;
 163
 164     /* bdrv_getlength returns a multiple of block size (512), rounded up. Since
 165      * dmg images can have odd sizes, try to look for the "koly" magic which
 166      * marks the begin of the UDIF trailer (512 bytes). This magic can be found
 167      * in the last 511 bytes of the second-last sector or the first 4 bytes of
 168      * the last sector (search space: 515 bytes) */
 169     length = bdrv_getlength(file_bs);
 170     if (length < 0) {
 171         error_setg_errno(errp, -length,
 172             "Failed to get file size while reading UDIF trailer");
 173         return length;
 174     } else if (length < 512) {
 175         error_setg(errp, "dmg file must be at least 512 bytes long");
 176         return -EINVAL;
 177     }
 178     if (length > 511 + 512) {
 179         offset = length - 511 - 512;
 180     }
 181     length = length < 515 ? length : 515;
 182     ret = bdrv_pread(file_bs, offset, buffer, length);
 183     if (ret < 0) {
 184         error_setg_errno(errp, -ret, "Failed while reading UDIF trailer");
 185         return ret;
 186     }
 187     for (i = 0; i < length - 3; i++) {
 188         if (buffer[i] == 'k' && buffer[i+1] == 'o' &&
 189             buffer[i+2] == 'l' && buffer[i+3] == 'y') {
 190             return offset + i;
 191         }
 192     }
 193     error_setg(errp, "Could not locate UDIF trailer in dmg file");
 194     return -EINVAL;
 195 }
 196
 197 /* used when building the sector table */
 198 typedef struct DmgHeaderState {
 199     /* used internally by dmg_read_mish_block to remember offsets of blocks
 200      * across calls */
 201     uint64_t data_fork_offset;
 202     /* exported for dmg_open */
 203     uint32_t max_compressed_size;
 204     uint32_t max_sectors_per_chunk;
 205 } DmgHeaderState;
 206
 207 static bool dmg_is_known_block_type(uint32_t entry_type)
 208 {
 209     switch (entry_type) {
 210     case 0x00000001:    /* uncompressed */
 211     case 0x00000002:    /* zeroes */
 212     case 0x80000005:    /* zlib */
 213 #ifdef CONFIG_BZIP2
 214     case 0x80000006:    /* bzip2 */
 215 #endif
 216         return true;
 217     default:
 218         return false;
 219     }
 220 }
 221
 222 static int dmg_read_mish_block(BDRVDMGState *s, DmgHeaderState *ds,
 223                                uint8_t *buffer, uint32_t count)
 224 {
 225     uint32_t type, i;
 226     int ret;
 227     size_t new_size;
 228     uint32_t chunk_count;
 229     int64_t offset = 0;
 230     uint64_t data_offset;
 231     uint64_t in_offset = ds->data_fork_offset;
 232     uint64_t out_offset;
 233
 234     type = buff_read_uint32(buffer, offset);
 235     /* skip data that is not a valid MISH block (invalid magic or too small) */
 236     if (type != 0x6d697368 || count < 244) {
 237         /* assume success for now */
 238         return 0;
 239     }
 240
 241     /* chunk offsets are relative to this sector number */
 242     out_offset = buff_read_uint64(buffer, offset + 8);
 243
 244     /* location in data fork for (compressed) blob (in bytes) */
 245     data_offset = buff_read_uint64(buffer, offset + 0x18);
 246     in_offset += data_offset;
 247
 248     /* move to begin of chunk entries */
 249     offset += 204;
 250
 251     chunk_count = (count - 204) / 40;
 252     new_size = sizeof(uint64_t) * (s->n_chunks + chunk_count);
 253     s->types = g_realloc(s->types, new_size / 2);
 254     s->offsets = g_realloc(s->offsets, new_size);
 255     s->lengths = g_realloc(s->lengths, new_size);
 256     s->sectors = g_realloc(s->sectors, new_size);
 257     s->sectorcounts = g_realloc(s->sectorcounts, new_size);
 258
 259     for (i = s->n_chunks; i < s->n_chunks + chunk_count; i++) {
 260         s->types[i] = buff_read_uint32(buffer, offset);
 261         if (!dmg_is_known_block_type(s->types[i])) {
 262             chunk_count--;
 263             i--;
 264             offset += 40;
 265             continue;
 266         }
 267
 268         /* sector number */
 269         s->sectors[i] = buff_read_uint64(buffer, offset + 8);
 270         s->sectors[i] += out_offset;
 271
 272         /* sector count */
 273         s->sectorcounts[i] = buff_read_uint64(buffer, offset + 0x10);
 274
 275         /* all-zeroes sector (type 2) does not need to be "uncompressed" and can
 276          * therefore be unbounded. */
 277         if (s->types[i] != 2 && s->sectorcounts[i] > DMG_SECTORCOUNTS_MAX) {
 278             error_report("sector count %" PRIu64 " for chunk %" PRIu32
 279                          " is larger than max (%u)",
 280                          s->sectorcounts[i], i, DMG_SECTORCOUNTS_MAX);
 281             ret = -EINVAL;
 282             goto fail;
 283         }
 284
 285         /* offset in (compressed) data fork */
 286         s->offsets[i] = buff_read_uint64(buffer, offset + 0x18);
 287         s->offsets[i] += in_offset;
 288
 289         /* length in (compressed) data fork */
 290         s->lengths[i] = buff_read_uint64(buffer, offset + 0x20);
 291
 292         if (s->lengths[i] > DMG_LENGTHS_MAX) {
 293             error_report("length %" PRIu64 " for chunk %" PRIu32
 294                          " is larger than max (%u)",
 295                          s->lengths[i], i, DMG_LENGTHS_MAX);
 296             ret = -EINVAL;
 297             goto fail;
 298         }
 299
 300         update_max_chunk_size(s, i, &ds->max_compressed_size,
 301                               &ds->max_sectors_per_chunk);
 302         offset += 40;
 303     }
 304     s->n_chunks += chunk_count;
 305     return 0;
 306
 307 fail:
 308     return ret;
 309 }
 310
 311 static int dmg_read_resource_fork(BlockDriverState *bs, DmgHeaderState *ds,
 312                                   uint64_t info_begin, uint64_t info_length)
 313 {
 314     BDRVDMGState *s = bs->opaque;
 315     int ret;
 316     uint32_t count, rsrc_data_offset;
 317     uint8_t *buffer = NULL;
 318     uint64_t info_end;
 319     uint64_t offset;
 320
 321     /* read offset from begin of resource fork (info_begin) to resource data */
 322     ret = read_uint32(bs, info_begin, &rsrc_data_offset);
 323     if (ret < 0) {
 324         goto fail;
 325     } else if (rsrc_data_offset > info_length) {
 326         ret = -EINVAL;
 327         goto fail;
 328     }
 329
 330     /* read length of resource data */
 331     ret = read_uint32(bs, info_begin + 8, &count);
 332     if (ret < 0) {
 333         goto fail;
 334     } else if (count == 0 || rsrc_data_offset + count > info_length) {
 335         ret = -EINVAL;
 336         goto fail;
 337     }
 338
 339     /* begin of resource data (consisting of one or more resources) */
 340     offset = info_begin + rsrc_data_offset;
 341
 342     /* end of resource data (there is possibly a following resource map
 343      * which will be ignored). */
 344     info_end = offset + count;
 345
 346     /* read offsets (mish blocks) from one or more resources in resource data */
 347     while (offset < info_end) {
 348         /* size of following resource */
 349         ret = read_uint32(bs, offset, &count);
 350         if (ret < 0) {
 351             goto fail;
 352         } else if (count == 0 || count > info_end - offset) {
 353             ret = -EINVAL;
 354             goto fail;
 355         }
 356         offset += 4;
 357
 358         buffer = g_realloc(buffer, count);
 359         ret = bdrv_pread(bs->file->bs, offset, buffer, count);
 360         if (ret < 0) {
 361             goto fail;
 362         }
 363
 364         ret = dmg_read_mish_block(s, ds, buffer, count);
 365         if (ret < 0) {
 366             goto fail;
 367         }
 368         /* advance offset by size of resource */
 369         offset += count;
 370     }
 371     ret = 0;
 372
 373 fail:
 374     g_free(buffer);
 375     return ret;
 376 }
 377
 378 static int dmg_read_plist_xml(BlockDriverState *bs, DmgHeaderState *ds,
 379                               uint64_t info_begin, uint64_t info_length)
 380 {
 381     BDRVDMGState *s = bs->opaque;
 382     int ret;
 383     uint8_t *buffer = NULL;
 384     char *data_begin, *data_end;
 385
 386     /* Have at least some length to avoid NULL for g_malloc. Attempt to set a
 387      * safe upper cap on the data length. A test sample had a XML length of
 388      * about 1 MiB. */
 389     if (info_length == 0 || info_length > 16 * 1024 * 1024) {
 390         ret = -EINVAL;
 391         goto fail;
 392     }
 393
 394     buffer = g_malloc(info_length + 1);
 395     buffer[info_length] = '\0';
 396     ret = bdrv_pread(bs->file->bs, info_begin, buffer, info_length);
 397     if (ret != info_length) {
 398         ret = -EINVAL;
 399         goto fail;
 400     }
 401
 402     /* look for <data>...</data>. The data is 284 (0x11c) bytes after base64
 403      * decode. The actual data element has 431 (0x1af) bytes which includes tabs
 404      * and line feeds. */
 405     data_end = (char *)buffer;
 406     while ((data_begin = strstr(data_end, "<data>")) != NULL) {
 407         guchar *mish;
 408         gsize out_len = 0;
 409
 410         data_begin += 6;
 411         data_end = strstr(data_begin, "</data>");
 412         /* malformed XML? */
 413         if (data_end == NULL) {
 414             ret = -EINVAL;
 415             goto fail;
 416         }
 417         *data_end++ = '\0';
 418         mish = g_base64_decode(data_begin, &out_len);
 419         ret = dmg_read_mish_block(s, ds, mish, (uint32_t)out_len);
 420         g_free(mish);
 421         if (ret < 0) {
 422             goto fail;
 423         }
 424     }
 425     ret = 0;
 426
 427 fail:
 428     g_free(buffer);
 429     return ret;
 430 }
 431
 432 static int dmg_open(BlockDriverState *bs, QDict *options, int flags,
 433                     Error **errp)
 434 {
 435     BDRVDMGState *s = bs->opaque;
 436     DmgHeaderState ds;
 437     uint64_t rsrc_fork_offset, rsrc_fork_length;
 438     uint64_t plist_xml_offset, plist_xml_length;
 439     int64_t offset;
 440     int ret;
 441
 442     bs->read_only = 1;
 443     s->n_chunks = 0;
 444     s->offsets = s->lengths = s->sectors = s->sectorcounts = NULL;
 445     /* used by dmg_read_mish_block to keep track of the current I/O position */
 446     ds.data_fork_offset = 0;
 447     ds.max_compressed_size = 1;
 448     ds.max_sectors_per_chunk = 1;
 449
 450     /* locate the UDIF trailer */
 451     offset = dmg_find_koly_offset(bs->file->bs, errp);
 452     if (offset < 0) {
 453         ret = offset;
 454         goto fail;
 455     }
 456
 457     /* offset of data fork (DataForkOffset) */
 458     ret = read_uint64(bs, offset + 0x18, &ds.data_fork_offset);
 459     if (ret < 0) {
 460         goto fail;
 461     } else if (ds.data_fork_offset > offset) {
 462         ret = -EINVAL;
 463         goto fail;
 464     }
 465
 466     /* offset of resource fork (RsrcForkOffset) */
 467     ret = read_uint64(bs, offset + 0x28, &rsrc_fork_offset);
 468     if (ret < 0) {
 469         goto fail;
 470     }
 471     ret = read_uint64(bs, offset + 0x30, &rsrc_fork_length);
 472     if (ret < 0) {
 473         goto fail;
 474     }
 475     if (rsrc_fork_offset >= offset ||
 476         rsrc_fork_length > offset - rsrc_fork_offset) {
 477         ret = -EINVAL;
 478         goto fail;
 479     }
 480     /* offset of property list (XMLOffset) */
 481     ret = read_uint64(bs, offset + 0xd8, &plist_xml_offset);
 482     if (ret < 0) {
 483         goto fail;
 484     }
 485     ret = read_uint64(bs, offset + 0xe0, &plist_xml_length);
 486     if (ret < 0) {
 487         goto fail;
 488     }
 489     if (plist_xml_offset >= offset ||
 490         plist_xml_length > offset - plist_xml_offset) {
 491         ret = -EINVAL;
 492         goto fail;
 493     }
 494     ret = read_uint64(bs, offset + 0x1ec, (uint64_t *)&bs->total_sectors);
 495     if (ret < 0) {
 496         goto fail;
 497     }
 498     if (bs->total_sectors < 0) {
 499         ret = -EINVAL;
 500         goto fail;
 501     }
 502     if (rsrc_fork_length != 0) {
 503         ret = dmg_read_resource_fork(bs, &ds,
 504                                      rsrc_fork_offset, rsrc_fork_length);
 505         if (ret < 0) {
 506             goto fail;
 507         }
 508     } else if (plist_xml_length != 0) {
 509         ret = dmg_read_plist_xml(bs, &ds, plist_xml_offset, plist_xml_length);
 510         if (ret < 0) {
 511             goto fail;
 512         }
 513     } else {
 514         ret = -EINVAL;
 515         goto fail;
 516     }
 517
 518     /* initialize zlib engine */
 519     s->compressed_chunk = qemu_try_blockalign(bs->file->bs,
 520                                               ds.max_compressed_size + 1);
 521     s->uncompressed_chunk = qemu_try_blockalign(bs->file->bs,
 522                                                 512 * ds.max_sectors_per_chunk);
 523     if (s->compressed_chunk == NULL || s->uncompressed_chunk == NULL) {
 524         ret = -ENOMEM;
 525         goto fail;
 526     }
 527
 528     if (inflateInit(&s->zstream) != Z_OK) {
 529         ret = -EINVAL;
 530         goto fail;
 531     }
 532
 533     s->current_chunk = s->n_chunks;
 534
 535     qemu_co_mutex_init(&s->lock);
 536     return 0;
 537
 538 fail:
 539     g_free(s->types);
 540     g_free(s->offsets);
 541     g_free(s->lengths);
 542     g_free(s->sectors);
 543     g_free(s->sectorcounts);
 544     qemu_vfree(s->compressed_chunk);
 545     qemu_vfree(s->uncompressed_chunk);
 546     return ret;
 547 }
 548
 549 static inline int is_sector_in_chunk(BDRVDMGState* s,
 550                 uint32_t chunk_num, uint64_t sector_num)
 551 {
 552     if (chunk_num >= s->n_chunks || s->sectors[chunk_num] > sector_num ||
 553             s->sectors[chunk_num] + s->sectorcounts[chunk_num] <= sector_num) {
 554         return 0;
 555     } else {
 556         return -1;
 557     }
 558 }
 559
 560 static inline uint32_t search_chunk(BDRVDMGState *s, uint64_t sector_num)
 561 {
 562     /* binary search */
 563     uint32_t chunk1 = 0, chunk2 = s->n_chunks, chunk3;
 564     while (chunk1 != chunk2) {
 565         chunk3 = (chunk1 + chunk2) / 2;
 566         if (s->sectors[chunk3] > sector_num) {
 567             chunk2 = chunk3;
 568         } else if (s->sectors[chunk3] + s->sectorcounts[chunk3] > sector_num) {
 569             return chunk3;
 570         } else {
 571             chunk1 = chunk3;
 572         }
 573     }
 574     return s->n_chunks; /* error */
 575 }
 576
 577 static inline int dmg_read_chunk(BlockDriverState *bs, uint64_t sector_num)
 578 {
 579     BDRVDMGState *s = bs->opaque;
 580
 581     if (!is_sector_in_chunk(s, s->current_chunk, sector_num)) {
 582         int ret;
 583         uint32_t chunk = search_chunk(s, sector_num);
 584 #ifdef CONFIG_BZIP2
 585         uint64_t total_out;
 586 #endif
 587
 588         if (chunk >= s->n_chunks) {
 589             return -1;
 590         }
 591
 592         s->current_chunk = s->n_chunks;
 593         switch (s->types[chunk]) { /* block entry type */
 594         case 0x80000005: { /* zlib compressed */
 595             /* we need to buffer, because only the chunk as whole can be
 596              * inflated. */
 597             ret = bdrv_pread(bs->file->bs, s->offsets[chunk],
 598                              s->compressed_chunk, s->lengths[chunk]);
 599             if (ret != s->lengths[chunk]) {
 600                 return -1;
 601             }
 602
 603             s->zstream.next_in = s->compressed_chunk;
 604             s->zstream.avail_in = s->lengths[chunk];
 605             s->zstream.next_out = s->uncompressed_chunk;
 606             s->zstream.avail_out = 512 * s->sectorcounts[chunk];
 607             ret = inflateReset(&s->zstream);
 608             if (ret != Z_OK) {
 609                 return -1;
 610             }
 611             ret = inflate(&s->zstream, Z_FINISH);
 612             if (ret != Z_STREAM_END ||
 613                 s->zstream.total_out != 512 * s->sectorcounts[chunk]) {
 614                 return -1;
 615             }
 616             break; }
 617 #ifdef CONFIG_BZIP2
 618         case 0x80000006: /* bzip2 compressed */
 619             /* we need to buffer, because only the chunk as whole can be
 620              * inflated. */
 621             ret = bdrv_pread(bs->file->bs, s->offsets[chunk],
 622                              s->compressed_chunk, s->lengths[chunk]);
 623             if (ret != s->lengths[chunk]) {
 624                 return -1;
 625             }
 626
 627             ret = BZ2_bzDecompressInit(&s->bzstream, 0, 0);
 628             if (ret != BZ_OK) {
 629                 return -1;
 630             }
 631             s->bzstream.next_in = (char *)s->compressed_chunk;
 632             s->bzstream.avail_in = (unsigned int) s->lengths[chunk];
 633             s->bzstream.next_out = (char *)s->uncompressed_chunk;
 634             s->bzstream.avail_out = (unsigned int) 512 * s->sectorcounts[chunk];
 635             ret = BZ2_bzDecompress(&s->bzstream);
 636             total_out = ((uint64_t)s->bzstream.total_out_hi32 << 32) +
 637                         s->bzstream.total_out_lo32;
 638             BZ2_bzDecompressEnd(&s->bzstream);
 639             if (ret != BZ_STREAM_END ||
 640                 total_out != 512 * s->sectorcounts[chunk]) {
 641                 return -1;
 642             }
 643             break;
 644 #endif /* CONFIG_BZIP2 */
 645         case 1: /* copy */
 646             ret = bdrv_pread(bs->file->bs, s->offsets[chunk],
 647                              s->uncompressed_chunk, s->lengths[chunk]);
 648             if (ret != s->lengths[chunk]) {
 649                 return -1;
 650             }
 651             break;
 652         case 2: /* zero */
 653             /* see dmg_read, it is treated specially. No buffer needs to be
 654              * pre-filled, the zeroes can be set directly. */
 655             break;
 656         }
 657         s->current_chunk = chunk;
 658     }
 659     return 0;
 660 }
 661
 662 static int dmg_read(BlockDriverState *bs, int64_t sector_num,
 663                     uint8_t *buf, int nb_sectors)
 664 {
 665     BDRVDMGState *s = bs->opaque;
 666     int i;
 667
 668     for (i = 0; i < nb_sectors; i++) {
 669         uint32_t sector_offset_in_chunk;
 670         if (dmg_read_chunk(bs, sector_num + i) != 0) {
 671             return -1;
 672         }
 673         /* Special case: current chunk is all zeroes. Do not perform a memcpy as
 674          * s->uncompressed_chunk may be too small to cover the large all-zeroes
 675          * section. dmg_read_chunk is called to find s->current_chunk */
 676         if (s->types[s->current_chunk] == 2) { /* all zeroes block entry */
 677             memset(buf + i * 512, 0, 512);
 678             continue;
 679         }
 680         sector_offset_in_chunk = sector_num + i - s->sectors[s->current_chunk];
 681         memcpy(buf + i * 512,
 682                s->uncompressed_chunk + sector_offset_in_chunk * 512, 512);
 683     }
 684     return 0;
 685 }
 686
 687 static coroutine_fn int dmg_co_read(BlockDriverState *bs, int64_t sector_num,
 688                                     uint8_t *buf, int nb_sectors)
 689 {
 690     int ret;
 691     BDRVDMGState *s = bs->opaque;
 692     qemu_co_mutex_lock(&s->lock);
 693     ret = dmg_read(bs, sector_num, buf, nb_sectors);
 694     qemu_co_mutex_unlock(&s->lock);
 695     return ret;
 696 }
 697
 698 static void dmg_close(BlockDriverState *bs)
 699 {
 700     BDRVDMGState *s = bs->opaque;
 701
 702     g_free(s->types);
 703     g_free(s->offsets);
 704     g_free(s->lengths);
 705     g_free(s->sectors);
 706     g_free(s->sectorcounts);
 707     qemu_vfree(s->compressed_chunk);
 708     qemu_vfree(s->uncompressed_chunk);
 709
 710     inflateEnd(&s->zstream);
 711 }
 712
 713 static BlockDriver bdrv_dmg = {
 714     .format_name    = "dmg",
 715     .instance_size  = sizeof(BDRVDMGState),
 716     .bdrv_probe     = dmg_probe,
 717     .bdrv_open      = dmg_open,
 718     .bdrv_read      = dmg_co_read,
 719     .bdrv_close     = dmg_close,
 720 };
 721
 722 static void bdrv_dmg_init(void)
 723 {
 724     bdrv_register(&bdrv_dmg);
 725 }
 726
 727 block_init(bdrv_dmg_init);