xref: /openbmc/qemu/block/dmg.c (revision 5cf434b5)
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 "block/block_int.h"
27 #include "qemu/bswap.h"
28 #include "qemu/error-report.h"
29 #include "qemu/module.h"
30 #include "qemu/memalign.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 int (*dmg_uncompress_lzfse)(char *next_in, unsigned int avail_in,
37                             char *next_out, unsigned int avail_out);
38 
39 enum {
40     /* Limit chunk sizes to prevent unreasonable amounts of memory being used
41      * or truncating when converting to 32-bit types
42      */
43     DMG_LENGTHS_MAX = 64 * 1024 * 1024, /* 64 MB */
44     DMG_SECTORCOUNTS_MAX = DMG_LENGTHS_MAX / 512,
45 };
46 
47 enum {
48     /* DMG Block Type */
49     UDZE = 0, /* Zeroes */
50     UDRW,     /* RAW type */
51     UDIG,     /* Ignore */
52     UDCO = 0x80000004,
53     UDZO,
54     UDBZ,
55     ULFO,
56     UDCM = 0x7ffffffe, /* Comments */
57     UDLE = 0xffffffff  /* Last Entry */
58 };
59 
60 static int dmg_probe(const uint8_t *buf, int buf_size, const char *filename)
61 {
62     int len;
63 
64     if (!filename) {
65         return 0;
66     }
67 
68     len = strlen(filename);
69     if (len > 4 && !strcmp(filename + len - 4, ".dmg")) {
70         return 2;
71     }
72     return 0;
73 }
74 
75 static int read_uint64(BlockDriverState *bs, int64_t offset, uint64_t *result)
76 {
77     uint64_t buffer;
78     int ret;
79 
80     ret = bdrv_pread(bs->file, offset, &buffer, 8);
81     if (ret < 0) {
82         return ret;
83     }
84 
85     *result = be64_to_cpu(buffer);
86     return 0;
87 }
88 
89 static int read_uint32(BlockDriverState *bs, int64_t offset, uint32_t *result)
90 {
91     uint32_t buffer;
92     int ret;
93 
94     ret = bdrv_pread(bs->file, offset, &buffer, 4);
95     if (ret < 0) {
96         return ret;
97     }
98 
99     *result = be32_to_cpu(buffer);
100     return 0;
101 }
102 
103 static inline uint64_t buff_read_uint64(const uint8_t *buffer, int64_t offset)
104 {
105     return be64_to_cpu(*(uint64_t *)&buffer[offset]);
106 }
107 
108 static inline uint32_t buff_read_uint32(const uint8_t *buffer, int64_t offset)
109 {
110     return be32_to_cpu(*(uint32_t *)&buffer[offset]);
111 }
112 
113 /* Increase max chunk sizes, if necessary.  This function is used to calculate
114  * the buffer sizes needed for compressed/uncompressed chunk I/O.
115  */
116 static void update_max_chunk_size(BDRVDMGState *s, uint32_t chunk,
117                                   uint32_t *max_compressed_size,
118                                   uint32_t *max_sectors_per_chunk)
119 {
120     uint32_t compressed_size = 0;
121     uint32_t uncompressed_sectors = 0;
122 
123     switch (s->types[chunk]) {
124     case UDZO: /* zlib compressed */
125     case UDBZ: /* bzip2 compressed */
126     case ULFO: /* lzfse compressed */
127         compressed_size = s->lengths[chunk];
128         uncompressed_sectors = s->sectorcounts[chunk];
129         break;
130     case UDRW: /* copy */
131         uncompressed_sectors = DIV_ROUND_UP(s->lengths[chunk], 512);
132         break;
133     case UDZE: /* zero */
134     case UDIG: /* ignore */
135         /* as the all-zeroes block may be large, it is treated specially: the
136          * sector is not copied from a large buffer, a simple memset is used
137          * instead. Therefore uncompressed_sectors does not need to be set. */
138         break;
139     }
140 
141     if (compressed_size > *max_compressed_size) {
142         *max_compressed_size = compressed_size;
143     }
144     if (uncompressed_sectors > *max_sectors_per_chunk) {
145         *max_sectors_per_chunk = uncompressed_sectors;
146     }
147 }
148 
149 static int64_t dmg_find_koly_offset(BdrvChild *file, Error **errp)
150 {
151     BlockDriverState *file_bs = file->bs;
152     int64_t length;
153     int64_t offset = 0;
154     uint8_t buffer[515];
155     int i, ret;
156 
157     /* bdrv_getlength returns a multiple of block size (512), rounded up. Since
158      * dmg images can have odd sizes, try to look for the "koly" magic which
159      * marks the begin of the UDIF trailer (512 bytes). This magic can be found
160      * in the last 511 bytes of the second-last sector or the first 4 bytes of
161      * the last sector (search space: 515 bytes) */
162     length = bdrv_getlength(file_bs);
163     if (length < 0) {
164         error_setg_errno(errp, -length,
165             "Failed to get file size while reading UDIF trailer");
166         return length;
167     } else if (length < 512) {
168         error_setg(errp, "dmg file must be at least 512 bytes long");
169         return -EINVAL;
170     }
171     if (length > 511 + 512) {
172         offset = length - 511 - 512;
173     }
174     length = length < 515 ? length : 515;
175     ret = bdrv_pread(file, offset, buffer, length);
176     if (ret < 0) {
177         error_setg_errno(errp, -ret, "Failed while reading UDIF trailer");
178         return ret;
179     }
180     for (i = 0; i < length - 3; i++) {
181         if (buffer[i] == 'k' && buffer[i+1] == 'o' &&
182             buffer[i+2] == 'l' && buffer[i+3] == 'y') {
183             return offset + i;
184         }
185     }
186     error_setg(errp, "Could not locate UDIF trailer in dmg file");
187     return -EINVAL;
188 }
189 
190 /* used when building the sector table */
191 typedef struct DmgHeaderState {
192     /* used internally by dmg_read_mish_block to remember offsets of blocks
193      * across calls */
194     uint64_t data_fork_offset;
195     /* exported for dmg_open */
196     uint32_t max_compressed_size;
197     uint32_t max_sectors_per_chunk;
198 } DmgHeaderState;
199 
200 static bool dmg_is_known_block_type(uint32_t entry_type)
201 {
202     switch (entry_type) {
203     case UDZE:    /* zeros */
204     case UDRW:    /* uncompressed */
205     case UDIG:    /* ignore */
206     case UDZO:    /* zlib */
207         return true;
208     case UDBZ:    /* bzip2 */
209         return !!dmg_uncompress_bz2;
210     case ULFO:    /* lzfse */
211         return !!dmg_uncompress_lzfse;
212     default:
213         return false;
214     }
215 }
216 
217 static int dmg_read_mish_block(BDRVDMGState *s, DmgHeaderState *ds,
218                                uint8_t *buffer, uint32_t count)
219 {
220     uint32_t type, i;
221     int ret;
222     size_t new_size;
223     uint32_t chunk_count;
224     int64_t offset = 0;
225     uint64_t data_offset;
226     uint64_t in_offset = ds->data_fork_offset;
227     uint64_t out_offset;
228 
229     type = buff_read_uint32(buffer, offset);
230     /* skip data that is not a valid MISH block (invalid magic or too small) */
231     if (type != 0x6d697368 || count < 244) {
232         /* assume success for now */
233         return 0;
234     }
235 
236     /* chunk offsets are relative to this sector number */
237     out_offset = buff_read_uint64(buffer, offset + 8);
238 
239     /* location in data fork for (compressed) blob (in bytes) */
240     data_offset = buff_read_uint64(buffer, offset + 0x18);
241     in_offset += data_offset;
242 
243     /* move to begin of chunk entries */
244     offset += 204;
245 
246     chunk_count = (count - 204) / 40;
247     new_size = sizeof(uint64_t) * (s->n_chunks + chunk_count);
248     s->types = g_realloc(s->types, new_size / 2);
249     s->offsets = g_realloc(s->offsets, new_size);
250     s->lengths = g_realloc(s->lengths, new_size);
251     s->sectors = g_realloc(s->sectors, new_size);
252     s->sectorcounts = g_realloc(s->sectorcounts, new_size);
253 
254     for (i = s->n_chunks; i < s->n_chunks + chunk_count; i++) {
255         s->types[i] = buff_read_uint32(buffer, offset);
256         if (!dmg_is_known_block_type(s->types[i])) {
257             chunk_count--;
258             i--;
259             offset += 40;
260             continue;
261         }
262 
263         /* sector number */
264         s->sectors[i] = buff_read_uint64(buffer, offset + 8);
265         s->sectors[i] += out_offset;
266 
267         /* sector count */
268         s->sectorcounts[i] = buff_read_uint64(buffer, offset + 0x10);
269 
270         /* all-zeroes sector (type UDZE and UDIG) does not need to be
271          * "uncompressed" and can therefore be unbounded. */
272         if (s->types[i] != UDZE && s->types[i] != UDIG
273             && s->sectorcounts[i] > DMG_SECTORCOUNTS_MAX) {
274             error_report("sector count %" PRIu64 " for chunk %" PRIu32
275                          " is larger than max (%u)",
276                          s->sectorcounts[i], i, DMG_SECTORCOUNTS_MAX);
277             ret = -EINVAL;
278             goto fail;
279         }
280 
281         /* offset in (compressed) data fork */
282         s->offsets[i] = buff_read_uint64(buffer, offset + 0x18);
283         s->offsets[i] += in_offset;
284 
285         /* length in (compressed) data fork */
286         s->lengths[i] = buff_read_uint64(buffer, offset + 0x20);
287 
288         if (s->lengths[i] > DMG_LENGTHS_MAX) {
289             error_report("length %" PRIu64 " for chunk %" PRIu32
290                          " is larger than max (%u)",
291                          s->lengths[i], i, DMG_LENGTHS_MAX);
292             ret = -EINVAL;
293             goto fail;
294         }
295 
296         update_max_chunk_size(s, i, &ds->max_compressed_size,
297                               &ds->max_sectors_per_chunk);
298         offset += 40;
299     }
300     s->n_chunks += chunk_count;
301     return 0;
302 
303 fail:
304     return ret;
305 }
306 
307 static int dmg_read_resource_fork(BlockDriverState *bs, DmgHeaderState *ds,
308                                   uint64_t info_begin, uint64_t info_length)
309 {
310     BDRVDMGState *s = bs->opaque;
311     int ret;
312     uint32_t count, rsrc_data_offset;
313     uint8_t *buffer = NULL;
314     uint64_t info_end;
315     uint64_t offset;
316 
317     /* read offset from begin of resource fork (info_begin) to resource data */
318     ret = read_uint32(bs, info_begin, &rsrc_data_offset);
319     if (ret < 0) {
320         goto fail;
321     } else if (rsrc_data_offset > info_length) {
322         ret = -EINVAL;
323         goto fail;
324     }
325 
326     /* read length of resource data */
327     ret = read_uint32(bs, info_begin + 8, &count);
328     if (ret < 0) {
329         goto fail;
330     } else if (count == 0 || rsrc_data_offset + count > info_length) {
331         ret = -EINVAL;
332         goto fail;
333     }
334 
335     /* begin of resource data (consisting of one or more resources) */
336     offset = info_begin + rsrc_data_offset;
337 
338     /* end of resource data (there is possibly a following resource map
339      * which will be ignored). */
340     info_end = offset + count;
341 
342     /* read offsets (mish blocks) from one or more resources in resource data */
343     while (offset < info_end) {
344         /* size of following resource */
345         ret = read_uint32(bs, offset, &count);
346         if (ret < 0) {
347             goto fail;
348         } else if (count == 0 || count > info_end - offset) {
349             ret = -EINVAL;
350             goto fail;
351         }
352         offset += 4;
353 
354         buffer = g_realloc(buffer, count);
355         ret = bdrv_pread(bs->file, offset, buffer, count);
356         if (ret < 0) {
357             goto fail;
358         }
359 
360         ret = dmg_read_mish_block(s, ds, buffer, count);
361         if (ret < 0) {
362             goto fail;
363         }
364         /* advance offset by size of resource */
365         offset += count;
366     }
367     ret = 0;
368 
369 fail:
370     g_free(buffer);
371     return ret;
372 }
373 
374 static int dmg_read_plist_xml(BlockDriverState *bs, DmgHeaderState *ds,
375                               uint64_t info_begin, uint64_t info_length)
376 {
377     BDRVDMGState *s = bs->opaque;
378     int ret;
379     uint8_t *buffer = NULL;
380     char *data_begin, *data_end;
381 
382     /* Have at least some length to avoid NULL for g_malloc. Attempt to set a
383      * safe upper cap on the data length. A test sample had a XML length of
384      * about 1 MiB. */
385     if (info_length == 0 || info_length > 16 * 1024 * 1024) {
386         ret = -EINVAL;
387         goto fail;
388     }
389 
390     buffer = g_malloc(info_length + 1);
391     buffer[info_length] = '\0';
392     ret = bdrv_pread(bs->file, info_begin, buffer, info_length);
393     if (ret != info_length) {
394         ret = -EINVAL;
395         goto fail;
396     }
397 
398     /* look for <data>...</data>. The data is 284 (0x11c) bytes after base64
399      * decode. The actual data element has 431 (0x1af) bytes which includes tabs
400      * and line feeds. */
401     data_end = (char *)buffer;
402     while ((data_begin = strstr(data_end, "<data>")) != NULL) {
403         guchar *mish;
404         gsize out_len = 0;
405 
406         data_begin += 6;
407         data_end = strstr(data_begin, "</data>");
408         /* malformed XML? */
409         if (data_end == NULL) {
410             ret = -EINVAL;
411             goto fail;
412         }
413         *data_end++ = '\0';
414         mish = g_base64_decode(data_begin, &out_len);
415         ret = dmg_read_mish_block(s, ds, mish, (uint32_t)out_len);
416         g_free(mish);
417         if (ret < 0) {
418             goto fail;
419         }
420     }
421     ret = 0;
422 
423 fail:
424     g_free(buffer);
425     return ret;
426 }
427 
428 static int dmg_open(BlockDriverState *bs, QDict *options, int flags,
429                     Error **errp)
430 {
431     BDRVDMGState *s = bs->opaque;
432     DmgHeaderState ds;
433     uint64_t rsrc_fork_offset, rsrc_fork_length;
434     uint64_t plist_xml_offset, plist_xml_length;
435     int64_t offset;
436     int ret;
437 
438     ret = bdrv_apply_auto_read_only(bs, NULL, errp);
439     if (ret < 0) {
440         return ret;
441     }
442 
443     bs->file = bdrv_open_child(NULL, options, "file", bs, &child_of_bds,
444                                BDRV_CHILD_IMAGE, false, errp);
445     if (!bs->file) {
446         return -EINVAL;
447     }
448 
449     block_module_load_one("dmg-bz2");
450     block_module_load_one("dmg-lzfse");
451 
452     s->n_chunks = 0;
453     s->offsets = s->lengths = s->sectors = s->sectorcounts = NULL;
454     /* used by dmg_read_mish_block to keep track of the current I/O position */
455     ds.data_fork_offset = 0;
456     ds.max_compressed_size = 1;
457     ds.max_sectors_per_chunk = 1;
458 
459     /* locate the UDIF trailer */
460     offset = dmg_find_koly_offset(bs->file, errp);
461     if (offset < 0) {
462         ret = offset;
463         goto fail;
464     }
465 
466     /* offset of data fork (DataForkOffset) */
467     ret = read_uint64(bs, offset + 0x18, &ds.data_fork_offset);
468     if (ret < 0) {
469         goto fail;
470     } else if (ds.data_fork_offset > offset) {
471         ret = -EINVAL;
472         goto fail;
473     }
474 
475     /* offset of resource fork (RsrcForkOffset) */
476     ret = read_uint64(bs, offset + 0x28, &rsrc_fork_offset);
477     if (ret < 0) {
478         goto fail;
479     }
480     ret = read_uint64(bs, offset + 0x30, &rsrc_fork_length);
481     if (ret < 0) {
482         goto fail;
483     }
484     if (rsrc_fork_offset >= offset ||
485         rsrc_fork_length > offset - rsrc_fork_offset) {
486         ret = -EINVAL;
487         goto fail;
488     }
489     /* offset of property list (XMLOffset) */
490     ret = read_uint64(bs, offset + 0xd8, &plist_xml_offset);
491     if (ret < 0) {
492         goto fail;
493     }
494     ret = read_uint64(bs, offset + 0xe0, &plist_xml_length);
495     if (ret < 0) {
496         goto fail;
497     }
498     if (plist_xml_offset >= offset ||
499         plist_xml_length > offset - plist_xml_offset) {
500         ret = -EINVAL;
501         goto fail;
502     }
503     ret = read_uint64(bs, offset + 0x1ec, (uint64_t *)&bs->total_sectors);
504     if (ret < 0) {
505         goto fail;
506     }
507     if (bs->total_sectors < 0) {
508         ret = -EINVAL;
509         goto fail;
510     }
511     if (rsrc_fork_length != 0) {
512         ret = dmg_read_resource_fork(bs, &ds,
513                                      rsrc_fork_offset, rsrc_fork_length);
514         if (ret < 0) {
515             goto fail;
516         }
517     } else if (plist_xml_length != 0) {
518         ret = dmg_read_plist_xml(bs, &ds, plist_xml_offset, plist_xml_length);
519         if (ret < 0) {
520             goto fail;
521         }
522     } else {
523         ret = -EINVAL;
524         goto fail;
525     }
526 
527     /* initialize zlib engine */
528     s->compressed_chunk = qemu_try_blockalign(bs->file->bs,
529                                               ds.max_compressed_size + 1);
530     s->uncompressed_chunk = qemu_try_blockalign(bs->file->bs,
531                                                 512 * ds.max_sectors_per_chunk);
532     if (s->compressed_chunk == NULL || s->uncompressed_chunk == NULL) {
533         ret = -ENOMEM;
534         goto fail;
535     }
536 
537     if (inflateInit(&s->zstream) != Z_OK) {
538         ret = -EINVAL;
539         goto fail;
540     }
541 
542     s->current_chunk = s->n_chunks;
543 
544     qemu_co_mutex_init(&s->lock);
545     return 0;
546 
547 fail:
548     g_free(s->types);
549     g_free(s->offsets);
550     g_free(s->lengths);
551     g_free(s->sectors);
552     g_free(s->sectorcounts);
553     qemu_vfree(s->compressed_chunk);
554     qemu_vfree(s->uncompressed_chunk);
555     return ret;
556 }
557 
558 static void dmg_refresh_limits(BlockDriverState *bs, Error **errp)
559 {
560     bs->bl.request_alignment = BDRV_SECTOR_SIZE; /* No sub-sector I/O */
561 }
562 
563 static inline int is_sector_in_chunk(BDRVDMGState *s,
564                 uint32_t chunk_num, uint64_t sector_num)
565 {
566     if (chunk_num >= s->n_chunks || s->sectors[chunk_num] > sector_num ||
567             s->sectors[chunk_num] + s->sectorcounts[chunk_num] <= sector_num) {
568         return 0;
569     } else {
570         return -1;
571     }
572 }
573 
574 static inline uint32_t search_chunk(BDRVDMGState *s, uint64_t sector_num)
575 {
576     /* binary search */
577     uint32_t chunk1 = 0, chunk2 = s->n_chunks, chunk3;
578     while (chunk1 <= chunk2) {
579         chunk3 = (chunk1 + chunk2) / 2;
580         if (s->sectors[chunk3] > sector_num) {
581             if (chunk3 == 0) {
582                 goto err;
583             }
584             chunk2 = chunk3 - 1;
585         } else if (s->sectors[chunk3] + s->sectorcounts[chunk3] > sector_num) {
586             return chunk3;
587         } else {
588             chunk1 = chunk3 + 1;
589         }
590     }
591 err:
592     return s->n_chunks; /* error */
593 }
594 
595 static inline int dmg_read_chunk(BlockDriverState *bs, uint64_t sector_num)
596 {
597     BDRVDMGState *s = bs->opaque;
598 
599     if (!is_sector_in_chunk(s, s->current_chunk, sector_num)) {
600         int ret;
601         uint32_t chunk = search_chunk(s, sector_num);
602 
603         if (chunk >= s->n_chunks) {
604             return -1;
605         }
606 
607         s->current_chunk = s->n_chunks;
608         switch (s->types[chunk]) { /* block entry type */
609         case UDZO: { /* zlib compressed */
610             /* we need to buffer, because only the chunk as whole can be
611              * inflated. */
612             ret = bdrv_pread(bs->file, s->offsets[chunk],
613                              s->compressed_chunk, s->lengths[chunk]);
614             if (ret != s->lengths[chunk]) {
615                 return -1;
616             }
617 
618             s->zstream.next_in = s->compressed_chunk;
619             s->zstream.avail_in = s->lengths[chunk];
620             s->zstream.next_out = s->uncompressed_chunk;
621             s->zstream.avail_out = 512 * s->sectorcounts[chunk];
622             ret = inflateReset(&s->zstream);
623             if (ret != Z_OK) {
624                 return -1;
625             }
626             ret = inflate(&s->zstream, Z_FINISH);
627             if (ret != Z_STREAM_END ||
628                 s->zstream.total_out != 512 * s->sectorcounts[chunk]) {
629                 return -1;
630             }
631             break; }
632         case UDBZ: /* bzip2 compressed */
633             if (!dmg_uncompress_bz2) {
634                 break;
635             }
636             /* we need to buffer, because only the chunk as whole can be
637              * inflated. */
638             ret = bdrv_pread(bs->file, s->offsets[chunk],
639                              s->compressed_chunk, s->lengths[chunk]);
640             if (ret != s->lengths[chunk]) {
641                 return -1;
642             }
643 
644             ret = dmg_uncompress_bz2((char *)s->compressed_chunk,
645                                      (unsigned int) s->lengths[chunk],
646                                      (char *)s->uncompressed_chunk,
647                                      (unsigned int)
648                                          (512 * s->sectorcounts[chunk]));
649             if (ret < 0) {
650                 return ret;
651             }
652             break;
653         case ULFO:
654             if (!dmg_uncompress_lzfse) {
655                 break;
656             }
657             /* we need to buffer, because only the chunk as whole can be
658              * inflated. */
659             ret = bdrv_pread(bs->file, s->offsets[chunk],
660                              s->compressed_chunk, s->lengths[chunk]);
661             if (ret != s->lengths[chunk]) {
662                 return -1;
663             }
664 
665             ret = dmg_uncompress_lzfse((char *)s->compressed_chunk,
666                                        (unsigned int) s->lengths[chunk],
667                                        (char *)s->uncompressed_chunk,
668                                        (unsigned int)
669                                            (512 * s->sectorcounts[chunk]));
670             if (ret < 0) {
671                 return ret;
672             }
673             break;
674         case UDRW: /* copy */
675             ret = bdrv_pread(bs->file, s->offsets[chunk],
676                              s->uncompressed_chunk, s->lengths[chunk]);
677             if (ret != s->lengths[chunk]) {
678                 return -1;
679             }
680             break;
681         case UDZE: /* zeros */
682         case UDIG: /* ignore */
683             /* see dmg_read, it is treated specially. No buffer needs to be
684              * pre-filled, the zeroes can be set directly. */
685             break;
686         }
687         s->current_chunk = chunk;
688     }
689     return 0;
690 }
691 
692 static int coroutine_fn
693 dmg_co_preadv(BlockDriverState *bs, int64_t offset, int64_t bytes,
694               QEMUIOVector *qiov, BdrvRequestFlags flags)
695 {
696     BDRVDMGState *s = bs->opaque;
697     uint64_t sector_num = offset >> BDRV_SECTOR_BITS;
698     int nb_sectors = bytes >> BDRV_SECTOR_BITS;
699     int ret, i;
700 
701     assert(QEMU_IS_ALIGNED(offset, BDRV_SECTOR_SIZE));
702     assert(QEMU_IS_ALIGNED(bytes, BDRV_SECTOR_SIZE));
703 
704     qemu_co_mutex_lock(&s->lock);
705 
706     for (i = 0; i < nb_sectors; i++) {
707         uint32_t sector_offset_in_chunk;
708         void *data;
709 
710         if (dmg_read_chunk(bs, sector_num + i) != 0) {
711             ret = -EIO;
712             goto fail;
713         }
714         /* Special case: current chunk is all zeroes. Do not perform a memcpy as
715          * s->uncompressed_chunk may be too small to cover the large all-zeroes
716          * section. dmg_read_chunk is called to find s->current_chunk */
717         if (s->types[s->current_chunk] == UDZE
718             || s->types[s->current_chunk] == UDIG) { /* all zeroes block entry */
719             qemu_iovec_memset(qiov, i * 512, 0, 512);
720             continue;
721         }
722         sector_offset_in_chunk = sector_num + i - s->sectors[s->current_chunk];
723         data = s->uncompressed_chunk + sector_offset_in_chunk * 512;
724         qemu_iovec_from_buf(qiov, i * 512, data, 512);
725     }
726 
727     ret = 0;
728 fail:
729     qemu_co_mutex_unlock(&s->lock);
730     return ret;
731 }
732 
733 static void dmg_close(BlockDriverState *bs)
734 {
735     BDRVDMGState *s = bs->opaque;
736 
737     g_free(s->types);
738     g_free(s->offsets);
739     g_free(s->lengths);
740     g_free(s->sectors);
741     g_free(s->sectorcounts);
742     qemu_vfree(s->compressed_chunk);
743     qemu_vfree(s->uncompressed_chunk);
744 
745     inflateEnd(&s->zstream);
746 }
747 
748 static BlockDriver bdrv_dmg = {
749     .format_name    = "dmg",
750     .instance_size  = sizeof(BDRVDMGState),
751     .bdrv_probe     = dmg_probe,
752     .bdrv_open      = dmg_open,
753     .bdrv_refresh_limits = dmg_refresh_limits,
754     .bdrv_child_perm     = bdrv_default_perms,
755     .bdrv_co_preadv = dmg_co_preadv,
756     .bdrv_close     = dmg_close,
757     .is_format      = true,
758 };
759 
760 static void bdrv_dmg_init(void)
761 {
762     bdrv_register(&bdrv_dmg);
763 }
764 
765 block_init(bdrv_dmg_init);
766