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