block-qcow.c

   1 /*
   2  * Block driver for the QCOW format
   3  *
   4  * Copyright (c) 2004 Fabrice Bellard
   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 "vl.h"
  25 #include "block_int.h"
  26 #include <zlib.h>
  27 #include "aes.h"
  28
  29 /**************************************************************/
  30 /* QEMU COW block driver with compression and encryption support */
  31
  32 #define QCOW_MAGIC (('Q' << 24) | ('F' << 16) | ('I' << 8) | 0xfb)
  33 #define QCOW_VERSION 1
  34
  35 #define QCOW_CRYPT_NONE 0
  36 #define QCOW_CRYPT_AES  1
  37
  38 #define QCOW_OFLAG_COMPRESSED (1LL << 63)
  39
  40 typedef struct QCowHeader {
  41     uint32_t magic;
  42     uint32_t version;
  43     uint64_t backing_file_offset;
  44     uint32_t backing_file_size;
  45     uint32_t mtime;
  46     uint64_t size; /* in bytes */
  47     uint8_t cluster_bits;
  48     uint8_t l2_bits;
  49     uint32_t crypt_method;
  50     uint64_t l1_table_offset;
  51 } QCowHeader;
  52
  53 #define L2_CACHE_SIZE 16
  54
  55 typedef struct BDRVQcowState {
  56     int fd;
  57     int cluster_bits;
  58     int cluster_size;
  59     int cluster_sectors;
  60     int l2_bits;
  61     int l2_size;
  62     int l1_size;
  63     uint64_t cluster_offset_mask;
  64     uint64_t l1_table_offset;
  65     uint64_t *l1_table;
  66     uint64_t *l2_cache;
  67     uint64_t l2_cache_offsets[L2_CACHE_SIZE];
  68     uint32_t l2_cache_counts[L2_CACHE_SIZE];
  69     uint8_t *cluster_cache;
  70     uint8_t *cluster_data;
  71     uint64_t cluster_cache_offset;
  72     uint32_t crypt_method; /* current crypt method, 0 if no key yet */
  73     uint32_t crypt_method_header;
  74     AES_KEY aes_encrypt_key;
  75     AES_KEY aes_decrypt_key;
  76 } BDRVQcowState;
  77
  78 static int decompress_cluster(BDRVQcowState *s, uint64_t cluster_offset);
  79
  80 static int qcow_probe(const uint8_t *buf, int buf_size, const char *filename)
  81 {
  82     const QCowHeader *cow_header = (const void *)buf;
  83
  84     if (buf_size >= sizeof(QCowHeader) &&
  85         be32_to_cpu(cow_header->magic) == QCOW_MAGIC &&
  86         be32_to_cpu(cow_header->version) == QCOW_VERSION)
  87         return 100;
  88     else
  89         return 0;
  90 }
  91
  92 static int qcow_open(BlockDriverState *bs, const char *filename)
  93 {
  94     BDRVQcowState *s = bs->opaque;
  95     int fd, len, i, shift;
  96     QCowHeader header;
  97
  98     fd = open(filename, O_RDWR | O_BINARY | O_LARGEFILE);
  99     if (fd < 0) {
 100         fd = open(filename, O_RDONLY | O_BINARY | O_LARGEFILE);
 101         if (fd < 0)
 102             return -1;
 103     }
 104     s->fd = fd;
 105     if (read(fd, &header, sizeof(header)) != sizeof(header))
 106         goto fail;
 107     be32_to_cpus(&header.magic);
 108     be32_to_cpus(&header.version);
 109     be64_to_cpus(&header.backing_file_offset);
 110     be32_to_cpus(&header.backing_file_size);
 111     be32_to_cpus(&header.mtime);
 112     be64_to_cpus(&header.size);
 113     be32_to_cpus(&header.crypt_method);
 114     be64_to_cpus(&header.l1_table_offset);
 115
 116     if (header.magic != QCOW_MAGIC || header.version != QCOW_VERSION)
 117         goto fail;
 118     if (header.size <= 1 || header.cluster_bits < 9)
 119         goto fail;
 120     if (header.crypt_method > QCOW_CRYPT_AES)
 121         goto fail;
 122     s->crypt_method_header = header.crypt_method;
 123     if (s->crypt_method_header)
 124         bs->encrypted = 1;
 125     s->cluster_bits = header.cluster_bits;
 126     s->cluster_size = 1 << s->cluster_bits;
 127     s->cluster_sectors = 1 << (s->cluster_bits - 9);
 128     s->l2_bits = header.l2_bits;
 129     s->l2_size = 1 << s->l2_bits;
 130     bs->total_sectors = header.size / 512;
 131     s->cluster_offset_mask = (1LL << (63 - s->cluster_bits)) - 1;
 132
 133     /* read the level 1 table */
 134     shift = s->cluster_bits + s->l2_bits;
 135     s->l1_size = (header.size + (1LL << shift) - 1) >> shift;
 136
 137     s->l1_table_offset = header.l1_table_offset;
 138     s->l1_table = qemu_malloc(s->l1_size * sizeof(uint64_t));
 139     if (!s->l1_table)
 140         goto fail;
 141     lseek(fd, s->l1_table_offset, SEEK_SET);
 142     if (read(fd, s->l1_table, s->l1_size * sizeof(uint64_t)) !=
 143         s->l1_size * sizeof(uint64_t))
 144         goto fail;
 145     for(i = 0;i < s->l1_size; i++) {
 146         be64_to_cpus(&s->l1_table[i]);
 147     }
 148     /* alloc L2 cache */
 149     s->l2_cache = qemu_malloc(s->l2_size * L2_CACHE_SIZE * sizeof(uint64_t));
 150     if (!s->l2_cache)
 151         goto fail;
 152     s->cluster_cache = qemu_malloc(s->cluster_size);
 153     if (!s->cluster_cache)
 154         goto fail;
 155     s->cluster_data = qemu_malloc(s->cluster_size);
 156     if (!s->cluster_data)
 157         goto fail;
 158     s->cluster_cache_offset = -1;
 159
 160     /* read the backing file name */
 161     if (header.backing_file_offset != 0) {
 162         len = header.backing_file_size;
 163         if (len > 1023)
 164             len = 1023;
 165         lseek(fd, header.backing_file_offset, SEEK_SET);
 166         if (read(fd, bs->backing_file, len) != len)
 167             goto fail;
 168         bs->backing_file[len] = '\0';
 169     }
 170     return 0;
 171
 172  fail:
 173     qemu_free(s->l1_table);
 174     qemu_free(s->l2_cache);
 175     qemu_free(s->cluster_cache);
 176     qemu_free(s->cluster_data);
 177     close(fd);
 178     return -1;
 179 }
 180
 181 static int qcow_set_key(BlockDriverState *bs, const char *key)
 182 {
 183     BDRVQcowState *s = bs->opaque;
 184     uint8_t keybuf[16];
 185     int len, i;
 186
 187     memset(keybuf, 0, 16);
 188     len = strlen(key);
 189     if (len > 16)
 190         len = 16;
 191     /* XXX: we could compress the chars to 7 bits to increase
 192        entropy */
 193     for(i = 0;i < len;i++) {
 194         keybuf[i] = key[i];
 195     }
 196     s->crypt_method = s->crypt_method_header;
 197
 198     if (AES_set_encrypt_key(keybuf, 128, &s->aes_encrypt_key) != 0)
 199         return -1;
 200     if (AES_set_decrypt_key(keybuf, 128, &s->aes_decrypt_key) != 0)
 201         return -1;
 202 #if 0
 203     /* test */
 204     {
 205         uint8_t in[16];
 206         uint8_t out[16];
 207         uint8_t tmp[16];
 208         for(i=0;i<16;i++)
 209             in[i] = i;
 210         AES_encrypt(in, tmp, &s->aes_encrypt_key);
 211         AES_decrypt(tmp, out, &s->aes_decrypt_key);
 212         for(i = 0; i < 16; i++)
 213             printf(" %02x", tmp[i]);
 214         printf("\n");
 215         for(i = 0; i < 16; i++)
 216             printf(" %02x", out[i]);
 217         printf("\n");
 218     }
 219 #endif
 220     return 0;
 221 }
 222
 223 /* The crypt function is compatible with the linux cryptoloop
 224    algorithm for < 4 GB images. NOTE: out_buf == in_buf is
 225    supported */
 226 static void encrypt_sectors(BDRVQcowState *s, int64_t sector_num,
 227                             uint8_t *out_buf, const uint8_t *in_buf,
 228                             int nb_sectors, int enc,
 229                             const AES_KEY *key)
 230 {
 231     union {
 232         uint64_t ll[2];
 233         uint8_t b[16];
 234     } ivec;
 235     int i;
 236
 237     for(i = 0; i < nb_sectors; i++) {
 238         ivec.ll[0] = cpu_to_le64(sector_num);
 239         ivec.ll[1] = 0;
 240         AES_cbc_encrypt(in_buf, out_buf, 512, key,
 241                         ivec.b, enc);
 242         sector_num++;
 243         in_buf += 512;
 244         out_buf += 512;
 245     }
 246 }
 247
 248 /* 'allocate' is:
 249  *
 250  * 0 to not allocate.
 251  *
 252  * 1 to allocate a normal cluster (for sector indexes 'n_start' to
 253  * 'n_end')
 254  *
 255  * 2 to allocate a compressed cluster of size
 256  * 'compressed_size'. 'compressed_size' must be > 0 and <
 257  * cluster_size
 258  *
 259  * return 0 if not allocated.
 260  */
 261 static uint64_t get_cluster_offset(BlockDriverState *bs,
 262                                    uint64_t offset, int allocate,
 263                                    int compressed_size,
 264                                    int n_start, int n_end)
 265 {
 266     BDRVQcowState *s = bs->opaque;
 267     int min_index, i, j, l1_index, l2_index;
 268     uint64_t l2_offset, *l2_table, cluster_offset, tmp;
 269     uint32_t min_count;
 270     int new_l2_table;
 271
 272     l1_index = offset >> (s->l2_bits + s->cluster_bits);
 273     l2_offset = s->l1_table[l1_index];
 274     new_l2_table = 0;
 275     if (!l2_offset) {
 276         if (!allocate)
 277             return 0;
 278         /* allocate a new l2 entry */
 279         l2_offset = lseek(s->fd, 0, SEEK_END);
 280         /* round to cluster size */
 281         l2_offset = (l2_offset + s->cluster_size - 1) & ~(s->cluster_size - 1);
 282         /* update the L1 entry */
 283         s->l1_table[l1_index] = l2_offset;
 284         tmp = cpu_to_be64(l2_offset);
 285         lseek(s->fd, s->l1_table_offset + l1_index * sizeof(tmp), SEEK_SET);
 286         if (write(s->fd, &tmp, sizeof(tmp)) != sizeof(tmp))
 287             return 0;
 288         new_l2_table = 1;
 289     }
 290     for(i = 0; i < L2_CACHE_SIZE; i++) {
 291         if (l2_offset == s->l2_cache_offsets[i]) {
 292             /* increment the hit count */
 293             if (++s->l2_cache_counts[i] == 0xffffffff) {
 294                 for(j = 0; j < L2_CACHE_SIZE; j++) {
 295                     s->l2_cache_counts[j] >>= 1;
 296                 }
 297             }
 298             l2_table = s->l2_cache + (i << s->l2_bits);
 299             goto found;
 300         }
 301     }
 302     /* not found: load a new entry in the least used one */
 303     min_index = 0;
 304     min_count = 0xffffffff;
 305     for(i = 0; i < L2_CACHE_SIZE; i++) {
 306         if (s->l2_cache_counts[i] < min_count) {
 307             min_count = s->l2_cache_counts[i];
 308             min_index = i;
 309         }
 310     }
 311     l2_table = s->l2_cache + (min_index << s->l2_bits);
 312     lseek(s->fd, l2_offset, SEEK_SET);
 313     if (new_l2_table) {
 314         memset(l2_table, 0, s->l2_size * sizeof(uint64_t));
 315         if (write(s->fd, l2_table, s->l2_size * sizeof(uint64_t)) !=
 316             s->l2_size * sizeof(uint64_t))
 317             return 0;
 318     } else {
 319         if (read(s->fd, l2_table, s->l2_size * sizeof(uint64_t)) !=
 320             s->l2_size * sizeof(uint64_t))
 321             return 0;
 322     }
 323     s->l2_cache_offsets[min_index] = l2_offset;
 324     s->l2_cache_counts[min_index] = 1;
 325  found:
 326     l2_index = (offset >> s->cluster_bits) & (s->l2_size - 1);
 327     cluster_offset = be64_to_cpu(l2_table[l2_index]);
 328     if (!cluster_offset ||
 329         ((cluster_offset & QCOW_OFLAG_COMPRESSED) && allocate == 1)) {
 330         if (!allocate)
 331             return 0;
 332         /* allocate a new cluster */
 333         if ((cluster_offset & QCOW_OFLAG_COMPRESSED) &&
 334             (n_end - n_start) < s->cluster_sectors) {
 335             /* if the cluster is already compressed, we must
 336                decompress it in the case it is not completely
 337                overwritten */
 338             if (decompress_cluster(s, cluster_offset) < 0)
 339                 return 0;
 340             cluster_offset = lseek(s->fd, 0, SEEK_END);
 341             cluster_offset = (cluster_offset + s->cluster_size - 1) &
 342                 ~(s->cluster_size - 1);
 343             /* write the cluster content */
 344             lseek(s->fd, cluster_offset, SEEK_SET);
 345             if (write(s->fd, s->cluster_cache, s->cluster_size) !=
 346                 s->cluster_size)
 347                 return -1;
 348         } else {
 349             cluster_offset = lseek(s->fd, 0, SEEK_END);
 350             if (allocate == 1) {
 351                 /* round to cluster size */
 352                 cluster_offset = (cluster_offset + s->cluster_size - 1) &
 353                     ~(s->cluster_size - 1);
 354                 ftruncate(s->fd, cluster_offset + s->cluster_size);
 355                 /* if encrypted, we must initialize the cluster
 356                    content which won't be written */
 357                 if (s->crypt_method &&
 358                     (n_end - n_start) < s->cluster_sectors) {
 359                     uint64_t start_sect;
 360                     start_sect = (offset & ~(s->cluster_size - 1)) >> 9;
 361                     memset(s->cluster_data + 512, 0xaa, 512);
 362                     for(i = 0; i < s->cluster_sectors; i++) {
 363                         if (i < n_start || i >= n_end) {
 364                             encrypt_sectors(s, start_sect + i,
 365                                             s->cluster_data,
 366                                             s->cluster_data + 512, 1, 1,
 367                                             &s->aes_encrypt_key);
 368                             lseek(s->fd, cluster_offset + i * 512, SEEK_SET);
 369                             if (write(s->fd, s->cluster_data, 512) != 512)
 370                                 return -1;
 371                         }
 372                     }
 373                 }
 374             } else {
 375                 cluster_offset |= QCOW_OFLAG_COMPRESSED |
 376                     (uint64_t)compressed_size << (63 - s->cluster_bits);
 377             }
 378         }
 379         /* update L2 table */
 380         tmp = cpu_to_be64(cluster_offset);
 381         l2_table[l2_index] = tmp;
 382         lseek(s->fd, l2_offset + l2_index * sizeof(tmp), SEEK_SET);
 383         if (write(s->fd, &tmp, sizeof(tmp)) != sizeof(tmp))
 384             return 0;
 385     }
 386     return cluster_offset;
 387 }
 388
 389 static int qcow_is_allocated(BlockDriverState *bs, int64_t sector_num,
 390                              int nb_sectors, int *pnum)
 391 {
 392     BDRVQcowState *s = bs->opaque;
 393     int index_in_cluster, n;
 394     uint64_t cluster_offset;
 395
 396     cluster_offset = get_cluster_offset(bs, sector_num << 9, 0, 0, 0, 0);
 397     index_in_cluster = sector_num & (s->cluster_sectors - 1);
 398     n = s->cluster_sectors - index_in_cluster;
 399     if (n > nb_sectors)
 400         n = nb_sectors;
 401     *pnum = n;
 402     return (cluster_offset != 0);
 403 }
 404
 405 static int decompress_buffer(uint8_t *out_buf, int out_buf_size,
 406                              const uint8_t *buf, int buf_size)
 407 {
 408     z_stream strm1, *strm = &strm1;
 409     int ret, out_len;
 410
 411     memset(strm, 0, sizeof(*strm));
 412
 413     strm->next_in = (uint8_t *)buf;
 414     strm->avail_in = buf_size;
 415     strm->next_out = out_buf;
 416     strm->avail_out = out_buf_size;
 417
 418     ret = inflateInit2(strm, -12);
 419     if (ret != Z_OK)
 420         return -1;
 421     ret = inflate(strm, Z_FINISH);
 422     out_len = strm->next_out - out_buf;
 423     if ((ret != Z_STREAM_END && ret != Z_BUF_ERROR) ||
 424         out_len != out_buf_size) {
 425         inflateEnd(strm);
 426         return -1;
 427     }
 428     inflateEnd(strm);
 429     return 0;
 430 }
 431
 432 static int decompress_cluster(BDRVQcowState *s, uint64_t cluster_offset)
 433 {
 434     int ret, csize;
 435     uint64_t coffset;
 436
 437     coffset = cluster_offset & s->cluster_offset_mask;
 438     if (s->cluster_cache_offset != coffset) {
 439         csize = cluster_offset >> (63 - s->cluster_bits);
 440         csize &= (s->cluster_size - 1);
 441         lseek(s->fd, coffset, SEEK_SET);
 442         ret = read(s->fd, s->cluster_data, csize);
 443         if (ret != csize)
 444             return -1;
 445         if (decompress_buffer(s->cluster_cache, s->cluster_size,
 446                               s->cluster_data, csize) < 0) {
 447             return -1;
 448         }
 449         s->cluster_cache_offset = coffset;
 450     }
 451     return 0;
 452 }
 453
 454 static int qcow_read(BlockDriverState *bs, int64_t sector_num,
 455                      uint8_t *buf, int nb_sectors)
 456 {
 457     BDRVQcowState *s = bs->opaque;
 458     int ret, index_in_cluster, n;
 459     uint64_t cluster_offset;
 460
 461     while (nb_sectors > 0) {
 462         cluster_offset = get_cluster_offset(bs, sector_num << 9, 0, 0, 0, 0);
 463         index_in_cluster = sector_num & (s->cluster_sectors - 1);
 464         n = s->cluster_sectors - index_in_cluster;
 465         if (n > nb_sectors)
 466             n = nb_sectors;
 467         if (!cluster_offset) {
 468             memset(buf, 0, 512 * n);
 469         } else if (cluster_offset & QCOW_OFLAG_COMPRESSED) {
 470             if (decompress_cluster(s, cluster_offset) < 0)
 471                 return -1;
 472             memcpy(buf, s->cluster_cache + index_in_cluster * 512, 512 * n);
 473         } else {
 474             lseek(s->fd, cluster_offset + index_in_cluster * 512, SEEK_SET);
 475             ret = read(s->fd, buf, n * 512);
 476             if (ret != n * 512)
 477                 return -1;
 478             if (s->crypt_method) {
 479                 encrypt_sectors(s, sector_num, buf, buf, n, 0,
 480                                 &s->aes_decrypt_key);
 481             }
 482         }
 483         nb_sectors -= n;
 484         sector_num += n;
 485         buf += n * 512;
 486     }
 487     return 0;
 488 }
 489
 490 static int qcow_write(BlockDriverState *bs, int64_t sector_num,
 491                      const uint8_t *buf, int nb_sectors)
 492 {
 493     BDRVQcowState *s = bs->opaque;
 494     int ret, index_in_cluster, n;
 495     uint64_t cluster_offset;
 496
 497     while (nb_sectors > 0) {
 498         index_in_cluster = sector_num & (s->cluster_sectors - 1);
 499         n = s->cluster_sectors - index_in_cluster;
 500         if (n > nb_sectors)
 501             n = nb_sectors;
 502         cluster_offset = get_cluster_offset(bs, sector_num << 9, 1, 0,
 503                                             index_in_cluster,
 504                                             index_in_cluster + n);
 505         if (!cluster_offset)
 506             return -1;
 507         lseek(s->fd, cluster_offset + index_in_cluster * 512, SEEK_SET);
 508         if (s->crypt_method) {
 509             encrypt_sectors(s, sector_num, s->cluster_data, buf, n, 1,
 510                             &s->aes_encrypt_key);
 511             ret = write(s->fd, s->cluster_data, n * 512);
 512         } else {
 513             ret = write(s->fd, buf, n * 512);
 514         }
 515         if (ret != n * 512)
 516             return -1;
 517         nb_sectors -= n;
 518         sector_num += n;
 519         buf += n * 512;
 520     }
 521     s->cluster_cache_offset = -1; /* disable compressed cache */
 522     return 0;
 523 }
 524
 525 static void qcow_close(BlockDriverState *bs)
 526 {
 527     BDRVQcowState *s = bs->opaque;
 528     qemu_free(s->l1_table);
 529     qemu_free(s->l2_cache);
 530     qemu_free(s->cluster_cache);
 531     qemu_free(s->cluster_data);
 532     close(s->fd);
 533 }
 534
 535 static int qcow_create(const char *filename, int64_t total_size,
 536                       const char *backing_file, int flags)
 537 {
 538     int fd, header_size, backing_filename_len, l1_size, i, shift;
 539     QCowHeader header;
 540     char backing_filename[1024];
 541     uint64_t tmp;
 542     struct stat st;
 543
 544     fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC | O_BINARY | O_LARGEFILE,
 545               0644);
 546     if (fd < 0)
 547         return -1;
 548     memset(&header, 0, sizeof(header));
 549     header.magic = cpu_to_be32(QCOW_MAGIC);
 550     header.version = cpu_to_be32(QCOW_VERSION);
 551     header.size = cpu_to_be64(total_size * 512);
 552     header_size = sizeof(header);
 553     backing_filename_len = 0;
 554     if (backing_file) {
 555         if (strcmp(backing_file, "fat:")) {
 556             const char *p;
 557             /* XXX: this is a hack: we do not attempt to check for URL
 558                like syntax */
 559             p = strchr(backing_file, ':');
 560             if (p && (p - backing_file) >= 2) {
 561                 /* URL like but exclude "c:" like filenames */
 562                 pstrcpy(backing_filename, sizeof(backing_filename),
 563                         backing_file);
 564             } else {
 565                 realpath(backing_file, backing_filename);
 566                 if (stat(backing_filename, &st) != 0) {
 567                     return -1;
 568                 }
 569             }
 570             header.backing_file_offset = cpu_to_be64(header_size);
 571             backing_filename_len = strlen(backing_filename);
 572             header.backing_file_size = cpu_to_be32(backing_filename_len);
 573             header_size += backing_filename_len;
 574         } else
 575             backing_file = NULL;
 576         header.mtime = cpu_to_be32(st.st_mtime);
 577         header.cluster_bits = 9; /* 512 byte cluster to avoid copying
 578                                     unmodifyed sectors */
 579         header.l2_bits = 12; /* 32 KB L2 tables */
 580     } else {
 581         header.cluster_bits = 12; /* 4 KB clusters */
 582         header.l2_bits = 9; /* 4 KB L2 tables */
 583     }
 584     header_size = (header_size + 7) & ~7;
 585     shift = header.cluster_bits + header.l2_bits;
 586     l1_size = ((total_size * 512) + (1LL << shift) - 1) >> shift;
 587
 588     header.l1_table_offset = cpu_to_be64(header_size);
 589     if (flags) {
 590         header.crypt_method = cpu_to_be32(QCOW_CRYPT_AES);
 591     } else {
 592         header.crypt_method = cpu_to_be32(QCOW_CRYPT_NONE);
 593     }
 594
 595     /* write all the data */
 596     write(fd, &header, sizeof(header));
 597     if (backing_file) {
 598         write(fd, backing_filename, backing_filename_len);
 599     }
 600     lseek(fd, header_size, SEEK_SET);
 601     tmp = 0;
 602     for(i = 0;i < l1_size; i++) {
 603         write(fd, &tmp, sizeof(tmp));
 604     }
 605     close(fd);
 606     return 0;
 607 }
 608
 609 int qcow_make_empty(BlockDriverState *bs)
 610 {
 611     BDRVQcowState *s = bs->opaque;
 612     uint32_t l1_length = s->l1_size * sizeof(uint64_t);
 613
 614     memset(s->l1_table, 0, l1_length);
 615     lseek(s->fd, s->l1_table_offset, SEEK_SET);
 616     if (write(s->fd, s->l1_table, l1_length) < 0)
 617         return -1;
 618     ftruncate(s->fd, s->l1_table_offset + l1_length);
 619
 620     memset(s->l2_cache, 0, s->l2_size * L2_CACHE_SIZE * sizeof(uint64_t));
 621     memset(s->l2_cache_offsets, 0, L2_CACHE_SIZE * sizeof(uint64_t));
 622     memset(s->l2_cache_counts, 0, L2_CACHE_SIZE * sizeof(uint32_t));
 623
 624     return 0;
 625 }
 626
 627 int qcow_get_cluster_size(BlockDriverState *bs)
 628 {
 629     BDRVQcowState *s = bs->opaque;
 630     if (bs->drv != &bdrv_qcow)
 631         return -1;
 632     return s->cluster_size;
 633 }
 634
 635 /* XXX: put compressed sectors first, then all the cluster aligned
 636    tables to avoid losing bytes in alignment */
 637 int qcow_compress_cluster(BlockDriverState *bs, int64_t sector_num,
 638                           const uint8_t *buf)
 639 {
 640     BDRVQcowState *s = bs->opaque;
 641     z_stream strm;
 642     int ret, out_len;
 643     uint8_t *out_buf;
 644     uint64_t cluster_offset;
 645
 646     if (bs->drv != &bdrv_qcow)
 647         return -1;
 648
 649     out_buf = qemu_malloc(s->cluster_size + (s->cluster_size / 1000) + 128);
 650     if (!out_buf)
 651         return -1;
 652
 653     /* best compression, small window, no zlib header */
 654     memset(&strm, 0, sizeof(strm));
 655     ret = deflateInit2(&strm, Z_DEFAULT_COMPRESSION,
 656                        Z_DEFLATED, -12,
 657                        9, Z_DEFAULT_STRATEGY);
 658     if (ret != 0) {
 659         qemu_free(out_buf);
 660         return -1;
 661     }
 662
 663     strm.avail_in = s->cluster_size;
 664     strm.next_in = (uint8_t *)buf;
 665     strm.avail_out = s->cluster_size;
 666     strm.next_out = out_buf;
 667
 668     ret = deflate(&strm, Z_FINISH);
 669     if (ret != Z_STREAM_END && ret != Z_OK) {
 670         qemu_free(out_buf);
 671         deflateEnd(&strm);
 672         return -1;
 673     }
 674     out_len = strm.next_out - out_buf;
 675
 676     deflateEnd(&strm);
 677
 678     if (ret != Z_STREAM_END || out_len >= s->cluster_size) {
 679         /* could not compress: write normal cluster */
 680         qcow_write(bs, sector_num, buf, s->cluster_sectors);
 681     } else {
 682         cluster_offset = get_cluster_offset(bs, sector_num << 9, 2,
 683                                             out_len, 0, 0);
 684         cluster_offset &= s->cluster_offset_mask;
 685         lseek(s->fd, cluster_offset, SEEK_SET);
 686         if (write(s->fd, out_buf, out_len) != out_len) {
 687             qemu_free(out_buf);
 688             return -1;
 689         }
 690     }
 691
 692     qemu_free(out_buf);
 693     return 0;
 694 }
 695
 696 static void qcow_flush(BlockDriverState *bs)
 697 {
 698     BDRVQcowState *s = bs->opaque;
 699     fsync(s->fd);
 700 }
 701
 702 BlockDriver bdrv_qcow = {
 703     "qcow",
 704     sizeof(BDRVQcowState),
 705     qcow_probe,
 706     qcow_open,
 707     qcow_read,
 708     qcow_write,
 709     qcow_close,
 710     qcow_create,
 711     qcow_flush,
 712     qcow_is_allocated,
 713     qcow_set_key,
 714     qcow_make_empty
 715 };
 716
 717