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
  32 /**************************************************************/
  33
  34 #define HEADER_MAGIC "Bochs Virtual HD Image"
  35 #define HEADER_VERSION 0x00020000
  36 #define HEADER_V1 0x00010000
  37 #define HEADER_SIZE 512
  38
  39 #define REDOLOG_TYPE "Redolog"
  40 #define GROWING_TYPE "Growing"
  41
  42 // not allocated: 0xffffffff
  43
  44 // always little-endian
  45 struct bochs_header {
  46     char magic[32];     /* "Bochs Virtual HD Image" */
  47     char type[16];      /* "Redolog" */
  48     char subtype[16];   /* "Undoable" / "Volatile" / "Growing" */
  49     uint32_t version;
  50     uint32_t header;    /* size of header */
  51
  52     uint32_t catalog;   /* num of entries */
  53     uint32_t bitmap;    /* bitmap size */
  54     uint32_t extent;    /* extent size */
  55
  56     union {
  57         struct {
  58             uint32_t reserved;  /* for ??? */
  59             uint64_t disk;      /* disk size */
  60             char padding[HEADER_SIZE - 64 - 20 - 12];
  61         } QEMU_PACKED redolog;
  62         struct {
  63             uint64_t disk;      /* disk size */
  64             char padding[HEADER_SIZE - 64 - 20 - 8];
  65         } QEMU_PACKED redolog_v1;
  66         char padding[HEADER_SIZE - 64 - 20];
  67     } extra;
  68 } QEMU_PACKED;
  69
  70 typedef struct BDRVBochsState {
  71     CoMutex lock;
  72     uint32_t *catalog_bitmap;
  73     uint32_t catalog_size;
  74
  75     uint32_t data_offset;
  76
  77     uint32_t bitmap_blocks;
  78     uint32_t extent_blocks;
  79     uint32_t extent_size;
  80 } BDRVBochsState;
  81
  82 static int bochs_probe(const uint8_t *buf, int buf_size, const char *filename)
  83 {
  84     const struct bochs_header *bochs = (const void *)buf;
  85
  86     if (buf_size < HEADER_SIZE)
  87         return 0;
  88
  89     if (!strcmp(bochs->magic, HEADER_MAGIC) &&
  90         !strcmp(bochs->type, REDOLOG_TYPE) &&
  91         !strcmp(bochs->subtype, GROWING_TYPE) &&
  92         ((le32_to_cpu(bochs->version) == HEADER_VERSION) ||
  93         (le32_to_cpu(bochs->version) == HEADER_V1)))
  94         return 100;
  95
  96     return 0;
  97 }
  98
  99 static int bochs_open(BlockDriverState *bs, QDict *options, int flags,
 100                       Error **errp)
 101 {
 102     BDRVBochsState *s = bs->opaque;
 103     uint32_t i;
 104     struct bochs_header bochs;
 105     int ret;
 106
 107     bs->read_only = true; /* no write support yet */
 108
 109     ret = bdrv_pread(bs->file, 0, &bochs, sizeof(bochs));
 110     if (ret < 0) {
 111         return ret;
 112     }
 113
 114     if (strcmp(bochs.magic, HEADER_MAGIC) ||
 115         strcmp(bochs.type, REDOLOG_TYPE) ||
 116         strcmp(bochs.subtype, GROWING_TYPE) ||
 117         ((le32_to_cpu(bochs.version) != HEADER_VERSION) &&
 118         (le32_to_cpu(bochs.version) != HEADER_V1))) {
 119         error_setg(errp, "Image not in Bochs format");
 120         return -EINVAL;
 121     }
 122
 123     if (le32_to_cpu(bochs.version) == HEADER_V1) {
 124         bs->total_sectors = le64_to_cpu(bochs.extra.redolog_v1.disk) / 512;
 125     } else {
 126         bs->total_sectors = le64_to_cpu(bochs.extra.redolog.disk) / 512;
 127     }
 128
 129     /* Limit to 1M entries to avoid unbounded allocation. This is what is
 130      * needed for the largest image that bximage can create (~8 TB). */
 131     s->catalog_size = le32_to_cpu(bochs.catalog);
 132     if (s->catalog_size > 0x100000) {
 133         error_setg(errp, "Catalog size is too large");
 134         return -EFBIG;
 135     }
 136
 137     s->catalog_bitmap = g_try_new(uint32_t, s->catalog_size);
 138     if (s->catalog_size && s->catalog_bitmap == NULL) {
 139         error_setg(errp, "Could not allocate memory for catalog");
 140         return -ENOMEM;
 141     }
 142
 143     ret = bdrv_pread(bs->file, le32_to_cpu(bochs.header), s->catalog_bitmap,
 144                      s->catalog_size * 4);
 145     if (ret < 0) {
 146         goto fail;
 147     }
 148
 149     for (i = 0; i < s->catalog_size; i++)
 150         le32_to_cpus(&s->catalog_bitmap[i]);
 151
 152     s->data_offset = le32_to_cpu(bochs.header) + (s->catalog_size * 4);
 153
 154     s->bitmap_blocks = 1 + (le32_to_cpu(bochs.bitmap) - 1) / 512;
 155     s->extent_blocks = 1 + (le32_to_cpu(bochs.extent) - 1) / 512;
 156
 157     s->extent_size = le32_to_cpu(bochs.extent);
 158     if (s->extent_size < BDRV_SECTOR_SIZE) {
 159         /* bximage actually never creates extents smaller than 4k */
 160         error_setg(errp, "Extent size must be at least 512");
 161         ret = -EINVAL;
 162         goto fail;
 163     } else if (!is_power_of_2(s->extent_size)) {
 164         error_setg(errp, "Extent size %" PRIu32 " is not a power of two",
 165                    s->extent_size);
 166         ret = -EINVAL;
 167         goto fail;
 168     } else if (s->extent_size > 0x800000) {
 169         error_setg(errp, "Extent size %" PRIu32 " is too large",
 170                    s->extent_size);
 171         ret = -EINVAL;
 172         goto fail;
 173     }
 174
 175     if (s->catalog_size < DIV_ROUND_UP(bs->total_sectors,
 176                                        s->extent_size / BDRV_SECTOR_SIZE))
 177     {
 178         error_setg(errp, "Catalog size is too small for this disk size");
 179         ret = -EINVAL;
 180         goto fail;
 181     }
 182
 183     qemu_co_mutex_init(&s->lock);
 184     return 0;
 185
 186 fail:
 187     g_free(s->catalog_bitmap);
 188     return ret;
 189 }
 190
 191 static void bochs_refresh_limits(BlockDriverState *bs, Error **errp)
 192 {
 193     bs->bl.request_alignment = BDRV_SECTOR_SIZE; /* No sub-sector I/O */
 194 }
 195
 196 static int64_t seek_to_sector(BlockDriverState *bs, int64_t sector_num)
 197 {
 198     BDRVBochsState *s = bs->opaque;
 199     uint64_t offset = sector_num * 512;
 200     uint64_t extent_index, extent_offset, bitmap_offset;
 201     char bitmap_entry;
 202     int ret;
 203
 204     // seek to sector
 205     extent_index = offset / s->extent_size;
 206     extent_offset = (offset % s->extent_size) / 512;
 207
 208     if (s->catalog_bitmap[extent_index] == 0xffffffff) {
 209         return 0; /* not allocated */
 210     }
 211
 212     bitmap_offset = s->data_offset +
 213         (512 * (uint64_t) s->catalog_bitmap[extent_index] *
 214         (s->extent_blocks + s->bitmap_blocks));
 215
 216     /* read in bitmap for current extent */
 217     ret = bdrv_pread(bs->file, bitmap_offset + (extent_offset / 8),
 218                      &bitmap_entry, 1);
 219     if (ret < 0) {
 220         return ret;
 221     }
 222
 223     if (!((bitmap_entry >> (extent_offset % 8)) & 1)) {
 224         return 0; /* not allocated */
 225     }
 226
 227     return bitmap_offset + (512 * (s->bitmap_blocks + extent_offset));
 228 }
 229
 230 static int coroutine_fn
 231 bochs_co_preadv(BlockDriverState *bs, uint64_t offset, uint64_t bytes,
 232                 QEMUIOVector *qiov, int flags)
 233 {
 234     BDRVBochsState *s = bs->opaque;
 235     uint64_t sector_num = offset >> BDRV_SECTOR_BITS;
 236     int nb_sectors = bytes >> BDRV_SECTOR_BITS;
 237     uint64_t bytes_done = 0;
 238     QEMUIOVector local_qiov;
 239     int ret;
 240
 241     assert((offset & (BDRV_SECTOR_SIZE - 1)) == 0);
 242     assert((bytes & (BDRV_SECTOR_SIZE - 1)) == 0);
 243
 244     qemu_iovec_init(&local_qiov, qiov->niov);
 245     qemu_co_mutex_lock(&s->lock);
 246
 247     while (nb_sectors > 0) {
 248         int64_t block_offset = seek_to_sector(bs, sector_num);
 249         if (block_offset < 0) {
 250             ret = block_offset;
 251             goto fail;
 252         }
 253
 254         qemu_iovec_reset(&local_qiov);
 255         qemu_iovec_concat(&local_qiov, qiov, bytes_done, 512);
 256
 257         if (block_offset > 0) {
 258             ret = bdrv_co_preadv(bs->file, block_offset, 512,
 259                                  &local_qiov, 0);
 260             if (ret < 0) {
 261                 goto fail;
 262             }
 263         } else {
 264             qemu_iovec_memset(&local_qiov, 0, 0, 512);
 265         }
 266         nb_sectors--;
 267         sector_num++;
 268         bytes_done += 512;
 269     }
 270
 271     ret = 0;
 272 fail:
 273     qemu_co_mutex_unlock(&s->lock);
 274     qemu_iovec_destroy(&local_qiov);
 275
 276     return ret;
 277 }
 278
 279 static void bochs_close(BlockDriverState *bs)
 280 {
 281     BDRVBochsState *s = bs->opaque;
 282     g_free(s->catalog_bitmap);
 283 }
 284
 285 static BlockDriver bdrv_bochs = {
 286     .format_name        = "bochs",
 287     .instance_size      = sizeof(BDRVBochsState),
 288     .bdrv_probe         = bochs_probe,
 289     .bdrv_open          = bochs_open,
 290     .bdrv_refresh_limits = bochs_refresh_limits,
 291     .bdrv_co_preadv = bochs_co_preadv,
 292     .bdrv_close         = bochs_close,
 293 };
 294
 295 static void bdrv_bochs_init(void)
 296 {
 297     bdrv_register(&bdrv_bochs);
 298 }
 299
 300 block_init(bdrv_bochs_init);