block/bochs.c

   1 /*
   2  * Block driver for the various disk image formats used by Bochs
   3  * Currently only for "growing" type in read-only mode
   4  *
   5  * Copyright (c) 2005 Alex Beregszaszi
   6  *
   7  * Permission is hereby granted, free of charge, to any person obtaining a copy
   8  * of this software and associated documentation files (the "Software"), to deal
   9  * in the Software without restriction, including without limitation the rights
  10  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  11  * copies of the Software, and to permit persons to whom the Software is
  12  * furnished to do so, subject to the following conditions:
  13  *
  14  * The above copyright notice and this permission notice shall be included in
  15  * all copies or substantial portions of the Software.
  16  *
  17  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  18  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  19  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
  20  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  21  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  22  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  23  * THE SOFTWARE.
  24  */
  25 #include "qemu/osdep.h"
  26 #include "qapi/error.h"
  27 #include "qemu-common.h"
  28 #include "block/block_int.h"
  29 #include "qemu/module.h"
  30 #include "qemu/bswap.h"
  31 #include "qemu/error-report.h"
  32
  33 /**************************************************************/
  34
  35 #define HEADER_MAGIC "Bochs Virtual HD Image"
  36 #define HEADER_VERSION 0x00020000
  37 #define HEADER_V1 0x00010000
  38 #define HEADER_SIZE 512
  39
  40 #define REDOLOG_TYPE "Redolog"
  41 #define GROWING_TYPE "Growing"
  42
  43 // not allocated: 0xffffffff
  44
  45 // always little-endian
  46 struct bochs_header {
  47     char magic[32];     /* "Bochs Virtual HD Image" */
  48     char type[16];      /* "Redolog" */
  49     char subtype[16];   /* "Undoable" / "Volatile" / "Growing" */
  50     uint32_t version;
  51     uint32_t header;    /* size of header */
  52
  53     uint32_t catalog;   /* num of entries */
  54     uint32_t bitmap;    /* bitmap size */
  55     uint32_t extent;    /* extent size */
  56
  57     union {
  58         struct {
  59             uint32_t reserved;  /* for ??? */
  60             uint64_t disk;      /* disk size */
  61             char padding[HEADER_SIZE - 64 - 20 - 12];
  62         } QEMU_PACKED redolog;
  63         struct {
  64             uint64_t disk;      /* disk size */
  65             char padding[HEADER_SIZE - 64 - 20 - 8];
  66         } QEMU_PACKED redolog_v1;
  67         char padding[HEADER_SIZE - 64 - 20];
  68     } extra;
  69 } QEMU_PACKED;
  70
  71 typedef struct BDRVBochsState {
  72     CoMutex lock;
  73     uint32_t *catalog_bitmap;
  74     uint32_t catalog_size;
  75
  76     uint32_t data_offset;
  77
  78     uint32_t bitmap_blocks;
  79     uint32_t extent_blocks;
  80     uint32_t extent_size;
  81 } BDRVBochsState;
  82
  83 static int bochs_probe(const uint8_t *buf, int buf_size, const char *filename)
  84 {
  85     const struct bochs_header *bochs = (const void *)buf;
  86
  87     if (buf_size < HEADER_SIZE)
  88         return 0;
  89
  90     if (!strcmp(bochs->magic, HEADER_MAGIC) &&
  91         !strcmp(bochs->type, REDOLOG_TYPE) &&
  92         !strcmp(bochs->subtype, GROWING_TYPE) &&
  93         ((le32_to_cpu(bochs->version) == HEADER_VERSION) ||
  94         (le32_to_cpu(bochs->version) == HEADER_V1)))
  95         return 100;
  96
  97     return 0;
  98 }
  99
 100 static int bochs_open(BlockDriverState *bs, QDict *options, int flags,
 101                       Error **errp)
 102 {
 103     BDRVBochsState *s = bs->opaque;
 104     uint32_t i;
 105     struct bochs_header bochs;
 106     int ret;
 107
 108     bs->file = bdrv_open_child(NULL, options, "file", bs, &child_file,
 109                                false, errp);
 110     if (!bs->file) {
 111         return -EINVAL;
 112     }
 113
 114     if (!bdrv_is_read_only(bs)) {
 115         error_report("Opening bochs images without an explicit read-only=on "
 116                      "option is deprecated. Future versions will refuse to "
 117                      "open the image instead of automatically marking the "
 118                      "image read-only.");
 119         ret = bdrv_set_read_only(bs, true, errp); /* no write support yet */
 120         if (ret < 0) {
 121             return ret;
 122         }
 123     }
 124
 125     ret = bdrv_pread(bs->file, 0, &bochs, sizeof(bochs));
 126     if (ret < 0) {
 127         return ret;
 128     }
 129
 130     if (strcmp(bochs.magic, HEADER_MAGIC) ||
 131         strcmp(bochs.type, REDOLOG_TYPE) ||
 132         strcmp(bochs.subtype, GROWING_TYPE) ||
 133         ((le32_to_cpu(bochs.version) != HEADER_VERSION) &&
 134         (le32_to_cpu(bochs.version) != HEADER_V1))) {
 135         error_setg(errp, "Image not in Bochs format");
 136         return -EINVAL;
 137     }
 138
 139     if (le32_to_cpu(bochs.version) == HEADER_V1) {
 140         bs->total_sectors = le64_to_cpu(bochs.extra.redolog_v1.disk) / 512;
 141     } else {
 142         bs->total_sectors = le64_to_cpu(bochs.extra.redolog.disk) / 512;
 143     }
 144
 145     /* Limit to 1M entries to avoid unbounded allocation. This is what is
 146      * needed for the largest image that bximage can create (~8 TB). */
 147     s->catalog_size = le32_to_cpu(bochs.catalog);
 148     if (s->catalog_size > 0x100000) {
 149         error_setg(errp, "Catalog size is too large");
 150         return -EFBIG;
 151     }
 152
 153     s->catalog_bitmap = g_try_new(uint32_t, s->catalog_size);
 154     if (s->catalog_size && s->catalog_bitmap == NULL) {
 155         error_setg(errp, "Could not allocate memory for catalog");
 156         return -ENOMEM;
 157     }
 158
 159     ret = bdrv_pread(bs->file, le32_to_cpu(bochs.header), s->catalog_bitmap,
 160                      s->catalog_size * 4);
 161     if (ret < 0) {
 162         goto fail;
 163     }
 164
 165     for (i = 0; i < s->catalog_size; i++)
 166         le32_to_cpus(&s->catalog_bitmap[i]);
 167
 168     s->data_offset = le32_to_cpu(bochs.header) + (s->catalog_size * 4);
 169
 170     s->bitmap_blocks = 1 + (le32_to_cpu(bochs.bitmap) - 1) / 512;
 171     s->extent_blocks = 1 + (le32_to_cpu(bochs.extent) - 1) / 512;
 172
 173     s->extent_size = le32_to_cpu(bochs.extent);
 174     if (s->extent_size < BDRV_SECTOR_SIZE) {
 175         /* bximage actually never creates extents smaller than 4k */
 176         error_setg(errp, "Extent size must be at least 512");
 177         ret = -EINVAL;
 178         goto fail;
 179     } else if (!is_power_of_2(s->extent_size)) {
 180         error_setg(errp, "Extent size %" PRIu32 " is not a power of two",
 181                    s->extent_size);
 182         ret = -EINVAL;
 183         goto fail;
 184     } else if (s->extent_size > 0x800000) {
 185         error_setg(errp, "Extent size %" PRIu32 " is too large",
 186                    s->extent_size);
 187         ret = -EINVAL;
 188         goto fail;
 189     }
 190
 191     if (s->catalog_size < DIV_ROUND_UP(bs->total_sectors,
 192                                        s->extent_size / BDRV_SECTOR_SIZE))
 193     {
 194         error_setg(errp, "Catalog size is too small for this disk size");
 195         ret = -EINVAL;
 196         goto fail;
 197     }
 198
 199     qemu_co_mutex_init(&s->lock);
 200     return 0;
 201
 202 fail:
 203     g_free(s->catalog_bitmap);
 204     return ret;
 205 }
 206
 207 static void bochs_refresh_limits(BlockDriverState *bs, Error **errp)
 208 {
 209     bs->bl.request_alignment = BDRV_SECTOR_SIZE; /* No sub-sector I/O */
 210 }
 211
 212 static int64_t seek_to_sector(BlockDriverState *bs, int64_t sector_num)
 213 {
 214     BDRVBochsState *s = bs->opaque;
 215     uint64_t offset = sector_num * 512;
 216     uint64_t extent_index, extent_offset, bitmap_offset;
 217     char bitmap_entry;
 218     int ret;
 219
 220     // seek to sector
 221     extent_index = offset / s->extent_size;
 222     extent_offset = (offset % s->extent_size) / 512;
 223
 224     if (s->catalog_bitmap[extent_index] == 0xffffffff) {
 225         return 0; /* not allocated */
 226     }
 227
 228     bitmap_offset = s->data_offset +
 229         (512 * (uint64_t) s->catalog_bitmap[extent_index] *
 230         (s->extent_blocks + s->bitmap_blocks));
 231
 232     /* read in bitmap for current extent */
 233     ret = bdrv_pread(bs->file, bitmap_offset + (extent_offset / 8),
 234                      &bitmap_entry, 1);
 235     if (ret < 0) {
 236         return ret;
 237     }
 238
 239     if (!((bitmap_entry >> (extent_offset % 8)) & 1)) {
 240         return 0; /* not allocated */
 241     }
 242
 243     return bitmap_offset + (512 * (s->bitmap_blocks + extent_offset));
 244 }
 245
 246 static int coroutine_fn
 247 bochs_co_preadv(BlockDriverState *bs, uint64_t offset, uint64_t bytes,
 248                 QEMUIOVector *qiov, int flags)
 249 {
 250     BDRVBochsState *s = bs->opaque;
 251     uint64_t sector_num = offset >> BDRV_SECTOR_BITS;
 252     int nb_sectors = bytes >> BDRV_SECTOR_BITS;
 253     uint64_t bytes_done = 0;
 254     QEMUIOVector local_qiov;
 255     int ret;
 256
 257     assert((offset & (BDRV_SECTOR_SIZE - 1)) == 0);
 258     assert((bytes & (BDRV_SECTOR_SIZE - 1)) == 0);
 259
 260     qemu_iovec_init(&local_qiov, qiov->niov);
 261     qemu_co_mutex_lock(&s->lock);
 262
 263     while (nb_sectors > 0) {
 264         int64_t block_offset = seek_to_sector(bs, sector_num);
 265         if (block_offset < 0) {
 266             ret = block_offset;
 267             goto fail;
 268         }
 269
 270         qemu_iovec_reset(&local_qiov);
 271         qemu_iovec_concat(&local_qiov, qiov, bytes_done, 512);
 272
 273         if (block_offset > 0) {
 274             ret = bdrv_co_preadv(bs->file, block_offset, 512,
 275                                  &local_qiov, 0);
 276             if (ret < 0) {
 277                 goto fail;
 278             }
 279         } else {
 280             qemu_iovec_memset(&local_qiov, 0, 0, 512);
 281         }
 282         nb_sectors--;
 283         sector_num++;
 284         bytes_done += 512;
 285     }
 286
 287     ret = 0;
 288 fail:
 289     qemu_co_mutex_unlock(&s->lock);
 290     qemu_iovec_destroy(&local_qiov);
 291
 292     return ret;
 293 }
 294
 295 static void bochs_close(BlockDriverState *bs)
 296 {
 297     BDRVBochsState *s = bs->opaque;
 298     g_free(s->catalog_bitmap);
 299 }
 300
 301 static BlockDriver bdrv_bochs = {
 302     .format_name        = "bochs",
 303     .instance_size      = sizeof(BDRVBochsState),
 304     .bdrv_probe         = bochs_probe,
 305     .bdrv_open          = bochs_open,
 306     .bdrv_child_perm     = bdrv_format_default_perms,
 307     .bdrv_refresh_limits = bochs_refresh_limits,
 308     .bdrv_co_preadv = bochs_co_preadv,
 309     .bdrv_close         = bochs_close,
 310 };
 311
 312 static void bdrv_bochs_init(void)
 313 {
 314     bdrv_register(&bdrv_bochs);
 315 }
 316
 317 block_init(bdrv_bochs_init);