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 "dmg.h"
  32
  33 int (*dmg_uncompress_bz2)(char *next_in, unsigned int avail_in,
  34                           char *next_out, unsigned int avail_out);
  35
  36 enum {
  37     /* Limit chunk sizes to prevent unreasonable amounts of memory being used
  38      * or truncating when converting to 32-bit types
  39      */
  40     DMG_LENGTHS_MAX = 64 * 1024 * 1024, /* 64 MB */
  41     DMG_SECTORCOUNTS_MAX = DMG_LENGTHS_MAX / 512,
  42 };
  43
  44 static int dmg_probe(const uint8_t *buf, int buf_size, const char *filename)
  45 {
  46     int len;
  47
  48     if (!filename) {
  49         return 0;
  50     }
  51
  52     len = strlen(filename);
  53     if (len > 4 && !strcmp(filename + len - 4, ".dmg")) {
  54         return 2;
  55     }
  56     return 0;
  57 }
  58
  59 static int read_uint64(BlockDriverState *bs, int64_t offset, uint64_t *result)
  60 {
  61     uint64_t buffer;
  62     int ret;
  63
  64     ret = bdrv_pread(bs->file, offset, &buffer, 8);
  65     if (ret < 0) {
  66         return ret;
  67     }
  68
  69     *result = be64_to_cpu(buffer);
  70     return 0;
  71 }
  72
  73 static int read_uint32(BlockDriverState *bs, int64_t offset, uint32_t *result)
  74 {
  75     uint32_t buffer;
  76     int ret;
  77
  78     ret = bdrv_pread(bs->file, offset, &buffer, 4);
  79     if (ret < 0) {
  80         return ret;
  81     }
  82
  83     *result = be32_to_cpu(buffer);
  84     return 0;
  85 }
  86
  87 static inline uint64_t buff_read_uint64(const uint8_t *buffer, int64_t offset)
  88 {
  89     return be64_to_cpu(*(uint64_t *)&buffer[offset]);
  90 }
  91
  92 static inline uint32_t buff_read_uint32(const uint8_t *buffer, int64_t offset)
  93 {
  94     return be32_to_cpu(*(uint32_t *)&buffer[offset]);
  95 }
  96
  97 /* Increase max chunk sizes, if necessary.  This function is used to calculate
  98  * the buffer sizes needed for compressed/uncompressed chunk I/O.
  99  */
 100 static void update_max_chunk_size(BDRVDMGState *s, uint32_t chunk,
 101                                   uint32_t *max_compressed_size,
 102                                   uint32_t *max_sectors_per_chunk)
 103 {
 104     uint32_t compressed_size = 0;
 105     uint32_t uncompressed_sectors = 0;
 106
 107     switch (s->types[chunk]) {
 108     case 0x80000005: /* zlib compressed */
 109     case 0x80000006: /* bzip2 compressed */
 110         compressed_size = s->lengths[chunk];
 111         uncompressed_sectors = s->sectorcounts[chunk];
 112         break;
 113     case 1: /* copy */
 114         uncompressed_sectors = DIV_ROUND_UP(s->lengths[chunk], 512);
 115         break;
 116     case 2: /* zero */
 117         /* as the all-zeroes block may be large, it is treated specially: the
 118          * sector is not copied from a large buffer, a simple memset is used
 119          * instead. Therefore uncompressed_sectors does not need to be set. */
 120         break;
 121     }
 122
 123     if (compressed_size > *max_compressed_size) {
 124         *max_compressed_size = compressed_size;
 125     }
 126     if (uncompressed_sectors > *max_sectors_per_chunk) {
 127         *max_sectors_per_chunk = uncompressed_sectors;
 128     }
 129 }
 130
 131 static int64_t dmg_find_koly_offset(BdrvChild *file, Error **errp)
 132 {
 133     BlockDriverState *file_bs = file->bs;
 134     int64_t length;
 135     int64_t offset = 0;
 136     uint8_t buffer[515];
 137     int i, ret;
 138
 139     /* bdrv_getlength returns a multiple of block size (512), rounded up. Since
 140      * dmg images can have odd sizes, try to look for the "koly" magic which
 141      * marks the begin of the UDIF trailer (512 bytes). This magic can be found
 142      * in the last 511 bytes of the second-last sector or the first 4 bytes of
 143      * the last sector (search space: 515 bytes) */
 144     length = bdrv_getlength(file_bs);
 145     if (length < 0) {
 146         error_setg_errno(errp, -length,
 147             "Failed to get file size while reading UDIF trailer");
 148         return length;
 149     } else if (length < 512) {
 150         error_setg(errp, "dmg file must be at least 512 bytes long");
 151         return -EINVAL;
 152     }
 153     if (length > 511 + 512) {
 154         offset = length - 511 - 512;
 155     }
 156     length = length < 515 ? length : 515;
 157     ret = bdrv_pread(file, offset, buffer, length);
 158     if (ret < 0) {
 159         error_setg_errno(errp, -ret, "Failed while reading UDIF trailer");
 160         return ret;
 161     }
 162     for (i = 0; i < length - 3; i++) {
 163         if (buffer[i] == 'k' && buffer[i+1] == 'o' &&
 164             buffer[i+2] == 'l' && buffer[i+3] == 'y') {
 165             return offset + i;
 166         }
 167     }
 168     error_setg(errp, "Could not locate UDIF trailer in dmg file");
 169     return -EINVAL;
 170 }
 171
 172 /* used when building the sector table */
 173 typedef struct DmgHeaderState {
 174     /* used internally by dmg_read_mish_block to remember offsets of blocks
 175      * across calls */
 176     uint64_t data_fork_offset;
 177     /* exported for dmg_open */
 178     uint32_t max_compressed_size;
 179     uint32_t max_sectors_per_chunk;
 180 } DmgHeaderState;
 181
 182 static bool dmg_is_known_block_type(uint32_t entry_type)
 183 {
 184     switch (entry_type) {
 185     case 0x00000001:    /* uncompressed */
 186     case 0x00000002:    /* zeroes */
 187     case 0x80000005:    /* zlib */
 188         return true;
 189     case 0x80000006:    /* bzip2 */
 190         return !!dmg_uncompress_bz2;
 191     default:
 192         return false;
 193     }
 194 }
 195
 196 static int dmg_read_mish_block(BDRVDMGState *s, DmgHeaderState *ds,
 197                                uint8_t *buffer, uint32_t count)
 198 {
 199     uint32_t type, i;
 200     int ret;
 201     size_t new_size;
 202     uint32_t chunk_count;
 203     int64_t offset = 0;
 204     uint64_t data_offset;
 205     uint64_t in_offset = ds->data_fork_offset;
 206     uint64_t out_offset;
 207
 208     type = buff_read_uint32(buffer, offset);
 209     /* skip data that is not a valid MISH block (invalid magic or too small) */
 210     if (type != 0x6d697368 || count < 244) {
 211         /* assume success for now */
 212         return 0;
 213     }
 214
 215     /* chunk offsets are relative to this sector number */
 216     out_offset = buff_read_uint64(buffer, offset + 8);
 217
 218     /* location in data fork for (compressed) blob (in bytes) */
 219     data_offset = buff_read_uint64(buffer, offset + 0x18);
 220     in_offset += data_offset;
 221
 222     /* move to begin of chunk entries */
 223     offset += 204;
 224
 225     chunk_count = (count - 204) / 40;
 226     new_size = sizeof(uint64_t) * (s->n_chunks + chunk_count);
 227     s->types = g_realloc(s->types, new_size / 2);
 228     s->offsets = g_realloc(s->offsets, new_size);
 229     s->lengths = g_realloc(s->lengths, new_size);
 230     s->sectors = g_realloc(s->sectors, new_size);
 231     s->sectorcounts = g_realloc(s->sectorcounts, new_size);
 232
 233     for (i = s->n_chunks; i < s->n_chunks + chunk_count; i++) {
 234         s->types[i] = buff_read_uint32(buffer, offset);
 235         if (!dmg_is_known_block_type(s->types[i])) {
 236             chunk_count--;
 237             i--;
 238             offset += 40;
 239             continue;
 240         }
 241
 242         /* sector number */
 243         s->sectors[i] = buff_read_uint64(buffer, offset + 8);
 244         s->sectors[i] += out_offset;
 245
 246         /* sector count */
 247         s->sectorcounts[i] = buff_read_uint64(buffer, offset + 0x10);
 248
 249         /* all-zeroes sector (type 2) does not need to be "uncompressed" and can
 250          * therefore be unbounded. */
 251         if (s->types[i] != 2 && s->sectorcounts[i] > DMG_SECTORCOUNTS_MAX) {
 252             error_report("sector count %" PRIu64 " for chunk %" PRIu32
 253                          " is larger than max (%u)",
 254                          s->sectorcounts[i], i, DMG_SECTORCOUNTS_MAX);
 255             ret = -EINVAL;
 256             goto fail;
 257         }
 258
 259         /* offset in (compressed) data fork */
 260         s->offsets[i] = buff_read_uint64(buffer, offset + 0x18);
 261         s->offsets[i] += in_offset;
 262
 263         /* length in (compressed) data fork */
 264         s->lengths[i] = buff_read_uint64(buffer, offset + 0x20);
 265
 266         if (s->lengths[i] > DMG_LENGTHS_MAX) {
 267             error_report("length %" PRIu64 " for chunk %" PRIu32
 268                          " is larger than max (%u)",
 269                          s->lengths[i], i, DMG_LENGTHS_MAX);
 270             ret = -EINVAL;
 271             goto fail;
 272         }
 273
 274         update_max_chunk_size(s, i, &ds->max_compressed_size,
 275                               &ds->max_sectors_per_chunk);
 276         offset += 40;
 277     }
 278     s->n_chunks += chunk_count;
 279     return 0;
 280
 281 fail:
 282     return ret;
 283 }
 284
 285 static int dmg_read_resource_fork(BlockDriverState *bs, DmgHeaderState *ds,
 286                                   uint64_t info_begin, uint64_t info_length)
 287 {
 288     BDRVDMGState *s = bs->opaque;
 289     int ret;
 290     uint32_t count, rsrc_data_offset;
 291     uint8_t *buffer = NULL;
 292     uint64_t info_end;
 293     uint64_t offset;
 294
 295     /* read offset from begin of resource fork (info_begin) to resource data */
 296     ret = read_uint32(bs, info_begin, &rsrc_data_offset);
 297     if (ret < 0) {
 298         goto fail;
 299     } else if (rsrc_data_offset > info_length) {
 300         ret = -EINVAL;
 301         goto fail;
 302     }
 303
 304     /* read length of resource data */
 305     ret = read_uint32(bs, info_begin + 8, &count);
 306     if (ret < 0) {
 307         goto fail;
 308     } else if (count == 0 || rsrc_data_offset + count > info_length) {
 309         ret = -EINVAL;
 310         goto fail;
 311     }
 312
 313     /* begin of resource data (consisting of one or more resources) */
 314     offset = info_begin + rsrc_data_offset;
 315
 316     /* end of resource data (there is possibly a following resource map
 317      * which will be ignored). */
 318     info_end = offset + count;
 319
 320     /* read offsets (mish blocks) from one or more resources in resource data */
 321     while (offset < info_end) {
 322         /* size of following resource */
 323         ret = read_uint32(bs, offset, &count);
 324         if (ret < 0) {
 325             goto fail;
 326         } else if (count == 0 || count > info_end - offset) {
 327             ret = -EINVAL;
 328             goto fail;
 329         }
 330         offset += 4;
 331
 332         buffer = g_realloc(buffer, count);
 333         ret = bdrv_pread(bs->file, offset, buffer, count);
 334         if (ret < 0) {
 335             goto fail;
 336         }
 337
 338         ret = dmg_read_mish_block(s, ds, buffer, count);
 339         if (ret < 0) {
 340             goto fail;
 341         }
 342         /* advance offset by size of resource */
 343         offset += count;
 344     }
 345     ret = 0;
 346
 347 fail:
 348     g_free(buffer);
 349     return ret;
 350 }
 351
 352 static int dmg_read_plist_xml(BlockDriverState *bs, DmgHeaderState *ds,
 353                               uint64_t info_begin, uint64_t info_length)
 354 {
 355     BDRVDMGState *s = bs->opaque;
 356     int ret;
 357     uint8_t *buffer = NULL;
 358     char *data_begin, *data_end;
 359
 360     /* Have at least some length to avoid NULL for g_malloc. Attempt to set a
 361      * safe upper cap on the data length. A test sample had a XML length of
 362      * about 1 MiB. */
 363     if (info_length == 0 || info_length > 16 * 1024 * 1024) {
 364         ret = -EINVAL;
 365         goto fail;
 366     }
 367
 368     buffer = g_malloc(info_length + 1);
 369     buffer[info_length] = '\0';
 370     ret = bdrv_pread(bs->file, info_begin, buffer, info_length);
 371     if (ret != info_length) {
 372         ret = -EINVAL;
 373         goto fail;
 374     }
 375
 376     /* look for <data>...</data>. The data is 284 (0x11c) bytes after base64
 377      * decode. The actual data element has 431 (0x1af) bytes which includes tabs
 378      * and line feeds. */
 379     data_end = (char *)buffer;
 380     while ((data_begin = strstr(data_end, "<data>")) != NULL) {
 381         guchar *mish;
 382         gsize out_len = 0;
 383
 384         data_begin += 6;
 385         data_end = strstr(data_begin, "</data>");
 386         /* malformed XML? */
 387         if (data_end == NULL) {
 388             ret = -EINVAL;
 389             goto fail;
 390         }
 391         *data_end++ = '\0';
 392         mish = g_base64_decode(data_begin, &out_len);
 393         ret = dmg_read_mish_block(s, ds, mish, (uint32_t)out_len);
 394         g_free(mish);
 395         if (ret < 0) {
 396             goto fail;
 397         }
 398     }
 399     ret = 0;
 400
 401 fail:
 402     g_free(buffer);
 403     return ret;
 404 }
 405
 406 static int dmg_open(BlockDriverState *bs, QDict *options, int flags,
 407                     Error **errp)
 408 {
 409     BDRVDMGState *s = bs->opaque;
 410     DmgHeaderState ds;
 411     uint64_t rsrc_fork_offset, rsrc_fork_length;
 412     uint64_t plist_xml_offset, plist_xml_length;
 413     int64_t offset;
 414     int ret;
 415
 416     bs->file = bdrv_open_child(NULL, options, "file", bs, &child_file,
 417                                false, errp);
 418     if (!bs->file) {
 419         return -EINVAL;
 420     }
 421
 422     if (!bdrv_is_read_only(bs)) {
 423         error_report("Opening dmg images without an explicit read-only=on "
 424                      "option is deprecated. Future versions will refuse to "
 425                      "open the image instead of automatically marking the "
 426                      "image read-only.");
 427         ret = bdrv_set_read_only(bs, true, errp);
 428         if (ret < 0) {
 429             return ret;
 430         }
 431     }
 432
 433     block_module_load_one("dmg-bz2");
 434
 435     s->n_chunks = 0;
 436     s->offsets = s->lengths = s->sectors = s->sectorcounts = NULL;
 437     /* used by dmg_read_mish_block to keep track of the current I/O position */
 438     ds.data_fork_offset = 0;
 439     ds.max_compressed_size = 1;
 440     ds.max_sectors_per_chunk = 1;
 441
 442     /* locate the UDIF trailer */
 443     offset = dmg_find_koly_offset(bs->file, errp);
 444     if (offset < 0) {
 445         ret = offset;
 446         goto fail;
 447     }
 448
 449     /* offset of data fork (DataForkOffset) */
 450     ret = read_uint64(bs, offset + 0x18, &ds.data_fork_offset);
 451     if (ret < 0) {
 452         goto fail;
 453     } else if (ds.data_fork_offset > offset) {
 454         ret = -EINVAL;
 455         goto fail;
 456     }
 457
 458     /* offset of resource fork (RsrcForkOffset) */
 459     ret = read_uint64(bs, offset + 0x28, &rsrc_fork_offset);
 460     if (ret < 0) {
 461         goto fail;
 462     }
 463     ret = read_uint64(bs, offset + 0x30, &rsrc_fork_length);
 464     if (ret < 0) {
 465         goto fail;
 466     }
 467     if (rsrc_fork_offset >= offset ||
 468         rsrc_fork_length > offset - rsrc_fork_offset) {
 469         ret = -EINVAL;
 470         goto fail;
 471     }
 472     /* offset of property list (XMLOffset) */
 473     ret = read_uint64(bs, offset + 0xd8, &plist_xml_offset);
 474     if (ret < 0) {
 475         goto fail;
 476     }
 477     ret = read_uint64(bs, offset + 0xe0, &plist_xml_length);
 478     if (ret < 0) {
 479         goto fail;
 480     }
 481     if (plist_xml_offset >= offset ||
 482         plist_xml_length > offset - plist_xml_offset) {
 483         ret = -EINVAL;
 484         goto fail;
 485     }
 486     ret = read_uint64(bs, offset + 0x1ec, (uint64_t *)&bs->total_sectors);
 487     if (ret < 0) {
 488         goto fail;
 489     }
 490     if (bs->total_sectors < 0) {
 491         ret = -EINVAL;
 492         goto fail;
 493     }
 494     if (rsrc_fork_length != 0) {
 495         ret = dmg_read_resource_fork(bs, &ds,
 496                                      rsrc_fork_offset, rsrc_fork_length);
 497         if (ret < 0) {
 498             goto fail;
 499         }
 500     } else if (plist_xml_length != 0) {
 501         ret = dmg_read_plist_xml(bs, &ds, plist_xml_offset, plist_xml_length);
 502         if (ret < 0) {
 503             goto fail;
 504         }
 505     } else {
 506         ret = -EINVAL;
 507         goto fail;
 508     }
 509
 510     /* initialize zlib engine */
 511     s->compressed_chunk = qemu_try_blockalign(bs->file->bs,
 512                                               ds.max_compressed_size + 1);
 513     s->uncompressed_chunk = qemu_try_blockalign(bs->file->bs,
 514                                                 512 * ds.max_sectors_per_chunk);
 515     if (s->compressed_chunk == NULL || s->uncompressed_chunk == NULL) {
 516         ret = -ENOMEM;
 517         goto fail;
 518     }
 519
 520     if (inflateInit(&s->zstream) != Z_OK) {
 521         ret = -EINVAL;
 522         goto fail;
 523     }
 524
 525     s->current_chunk = s->n_chunks;
 526
 527     qemu_co_mutex_init(&s->lock);
 528     return 0;
 529
 530 fail:
 531     g_free(s->types);
 532     g_free(s->offsets);
 533     g_free(s->lengths);
 534     g_free(s->sectors);
 535     g_free(s->sectorcounts);
 536     qemu_vfree(s->compressed_chunk);
 537     qemu_vfree(s->uncompressed_chunk);
 538     return ret;
 539 }
 540
 541 static void dmg_refresh_limits(BlockDriverState *bs, Error **errp)
 542 {
 543     bs->bl.request_alignment = BDRV_SECTOR_SIZE; /* No sub-sector I/O */
 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
 582         if (chunk >= s->n_chunks) {
 583             return -1;
 584         }
 585
 586         s->current_chunk = s->n_chunks;
 587         switch (s->types[chunk]) { /* block entry type */
 588         case 0x80000005: { /* zlib compressed */
 589             /* we need to buffer, because only the chunk as whole can be
 590              * inflated. */
 591             ret = bdrv_pread(bs->file, s->offsets[chunk],
 592                              s->compressed_chunk, s->lengths[chunk]);
 593             if (ret != s->lengths[chunk]) {
 594                 return -1;
 595             }
 596
 597             s->zstream.next_in = s->compressed_chunk;
 598             s->zstream.avail_in = s->lengths[chunk];
 599             s->zstream.next_out = s->uncompressed_chunk;
 600             s->zstream.avail_out = 512 * s->sectorcounts[chunk];
 601             ret = inflateReset(&s->zstream);
 602             if (ret != Z_OK) {
 603                 return -1;
 604             }
 605             ret = inflate(&s->zstream, Z_FINISH);
 606             if (ret != Z_STREAM_END ||
 607                 s->zstream.total_out != 512 * s->sectorcounts[chunk]) {
 608                 return -1;
 609             }
 610             break; }
 611         case 0x80000006: /* bzip2 compressed */
 612             if (!dmg_uncompress_bz2) {
 613                 break;
 614             }
 615             /* we need to buffer, because only the chunk as whole can be
 616              * inflated. */
 617             ret = bdrv_pread(bs->file, s->offsets[chunk],
 618                              s->compressed_chunk, s->lengths[chunk]);
 619             if (ret != s->lengths[chunk]) {
 620                 return -1;
 621             }
 622
 623             ret = dmg_uncompress_bz2((char *)s->compressed_chunk,
 624                                      (unsigned int) s->lengths[chunk],
 625                                      (char *)s->uncompressed_chunk,
 626                                      (unsigned int)
 627                                          (512 * s->sectorcounts[chunk]));
 628             if (ret < 0) {
 629                 return ret;
 630             }
 631             break;
 632         case 1: /* copy */
 633             ret = bdrv_pread(bs->file, s->offsets[chunk],
 634                              s->uncompressed_chunk, s->lengths[chunk]);
 635             if (ret != s->lengths[chunk]) {
 636                 return -1;
 637             }
 638             break;
 639         case 2: /* zero */
 640             /* see dmg_read, it is treated specially. No buffer needs to be
 641              * pre-filled, the zeroes can be set directly. */
 642             break;
 643         }
 644         s->current_chunk = chunk;
 645     }
 646     return 0;
 647 }
 648
 649 static int coroutine_fn
 650 dmg_co_preadv(BlockDriverState *bs, uint64_t offset, uint64_t bytes,
 651               QEMUIOVector *qiov, int flags)
 652 {
 653     BDRVDMGState *s = bs->opaque;
 654     uint64_t sector_num = offset >> BDRV_SECTOR_BITS;
 655     int nb_sectors = bytes >> BDRV_SECTOR_BITS;
 656     int ret, i;
 657
 658     assert((offset & (BDRV_SECTOR_SIZE - 1)) == 0);
 659     assert((bytes & (BDRV_SECTOR_SIZE - 1)) == 0);
 660
 661     qemu_co_mutex_lock(&s->lock);
 662
 663     for (i = 0; i < nb_sectors; i++) {
 664         uint32_t sector_offset_in_chunk;
 665         void *data;
 666
 667         if (dmg_read_chunk(bs, sector_num + i) != 0) {
 668             ret = -EIO;
 669             goto fail;
 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             qemu_iovec_memset(qiov, i * 512, 0, 512);
 676             continue;
 677         }
 678         sector_offset_in_chunk = sector_num + i - s->sectors[s->current_chunk];
 679         data = s->uncompressed_chunk + sector_offset_in_chunk * 512;
 680         qemu_iovec_from_buf(qiov, i * 512, data, 512);
 681     }
 682
 683     ret = 0;
 684 fail:
 685     qemu_co_mutex_unlock(&s->lock);
 686     return ret;
 687 }
 688
 689 static void dmg_close(BlockDriverState *bs)
 690 {
 691     BDRVDMGState *s = bs->opaque;
 692
 693     g_free(s->types);
 694     g_free(s->offsets);
 695     g_free(s->lengths);
 696     g_free(s->sectors);
 697     g_free(s->sectorcounts);
 698     qemu_vfree(s->compressed_chunk);
 699     qemu_vfree(s->uncompressed_chunk);
 700
 701     inflateEnd(&s->zstream);
 702 }
 703
 704 static BlockDriver bdrv_dmg = {
 705     .format_name    = "dmg",
 706     .instance_size  = sizeof(BDRVDMGState),
 707     .bdrv_probe     = dmg_probe,
 708     .bdrv_open      = dmg_open,
 709     .bdrv_refresh_limits = dmg_refresh_limits,
 710     .bdrv_child_perm     = bdrv_format_default_perms,
 711     .bdrv_co_preadv = dmg_co_preadv,
 712     .bdrv_close     = dmg_close,
 713 };
 714
 715 static void bdrv_dmg_init(void)
 716 {
 717     bdrv_register(&bdrv_dmg);
 718 }
 719
 720 block_init(bdrv_dmg_init);