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-common.h"
  26 #include "block/block_int.h"
  27 #include "qemu/module.h"
  28
  29 /**************************************************************/
  30
  31 #define HEADER_MAGIC "Bochs Virtual HD Image"
  32 #define HEADER_VERSION 0x00020000
  33 #define HEADER_V1 0x00010000
  34 #define HEADER_SIZE 512
  35
  36 #define REDOLOG_TYPE "Redolog"
  37 #define GROWING_TYPE "Growing"
  38
  39 // not allocated: 0xffffffff
  40
  41 // always little-endian
  42 struct bochs_header {
  43     char magic[32];     /* "Bochs Virtual HD Image" */
  44     char type[16];      /* "Redolog" */
  45     char subtype[16];   /* "Undoable" / "Volatile" / "Growing" */
  46     uint32_t version;
  47     uint32_t header;    /* size of header */
  48
  49     uint32_t catalog;   /* num of entries */
  50     uint32_t bitmap;    /* bitmap size */
  51     uint32_t extent;    /* extent size */
  52
  53     union {
  54         struct {
  55             uint32_t reserved;  /* for ??? */
  56             uint64_t disk;      /* disk size */
  57             char padding[HEADER_SIZE - 64 - 20 - 12];
  58         } QEMU_PACKED redolog;
  59         struct {
  60             uint64_t disk;      /* disk size */
  61             char padding[HEADER_SIZE - 64 - 20 - 8];
  62         } QEMU_PACKED redolog_v1;
  63         char padding[HEADER_SIZE - 64 - 20];
  64     } extra;
  65 } QEMU_PACKED;
  66
  67 typedef struct BDRVBochsState {
  68     CoMutex lock;
  69     uint32_t *catalog_bitmap;
  70     uint32_t catalog_size;
  71
  72     uint32_t data_offset;
  73
  74     uint32_t bitmap_blocks;
  75     uint32_t extent_blocks;
  76     uint32_t extent_size;
  77 } BDRVBochsState;
  78
  79 static int bochs_probe(const uint8_t *buf, int buf_size, const char *filename)
  80 {
  81     const struct bochs_header *bochs = (const void *)buf;
  82
  83     if (buf_size < HEADER_SIZE)
  84         return 0;
  85
  86     if (!strcmp(bochs->magic, HEADER_MAGIC) &&
  87         !strcmp(bochs->type, REDOLOG_TYPE) &&
  88         !strcmp(bochs->subtype, GROWING_TYPE) &&
  89         ((le32_to_cpu(bochs->version) == HEADER_VERSION) ||
  90         (le32_to_cpu(bochs->version) == HEADER_V1)))
  91         return 100;
  92
  93     return 0;
  94 }
  95
  96 static int bochs_open(BlockDriverState *bs, QDict *options, int flags,
  97                       Error **errp)
  98 {
  99     BDRVBochsState *s = bs->opaque;
 100     uint32_t i;
 101     struct bochs_header bochs;
 102     int ret;
 103
 104     bs->read_only = 1; // no write support yet
 105
 106     ret = bdrv_pread(bs->file, 0, &bochs, sizeof(bochs));
 107     if (ret < 0) {
 108         return ret;
 109     }
 110
 111     if (strcmp(bochs.magic, HEADER_MAGIC) ||
 112         strcmp(bochs.type, REDOLOG_TYPE) ||
 113         strcmp(bochs.subtype, GROWING_TYPE) ||
 114         ((le32_to_cpu(bochs.version) != HEADER_VERSION) &&
 115         (le32_to_cpu(bochs.version) != HEADER_V1))) {
 116         error_setg(errp, "Image not in Bochs format");
 117         return -EINVAL;
 118     }
 119
 120     if (le32_to_cpu(bochs.version) == HEADER_V1) {
 121         bs->total_sectors = le64_to_cpu(bochs.extra.redolog_v1.disk) / 512;
 122     } else {
 123         bs->total_sectors = le64_to_cpu(bochs.extra.redolog.disk) / 512;
 124     }
 125
 126     /* Limit to 1M entries to avoid unbounded allocation. This is what is
 127      * needed for the largest image that bximage can create (~8 TB). */
 128     s->catalog_size = le32_to_cpu(bochs.catalog);
 129     if (s->catalog_size > 0x100000) {
 130         error_setg(errp, "Catalog size is too large");
 131         return -EFBIG;
 132     }
 133
 134     s->catalog_bitmap = g_try_malloc(s->catalog_size * 4);
 135     if (s->catalog_size && s->catalog_bitmap == NULL) {
 136         error_setg(errp, "Could not allocate memory for catalog");
 137         return -ENOMEM;
 138     }
 139
 140     ret = bdrv_pread(bs->file, le32_to_cpu(bochs.header), s->catalog_bitmap,
 141                      s->catalog_size * 4);
 142     if (ret < 0) {
 143         goto fail;
 144     }
 145
 146     for (i = 0; i < s->catalog_size; i++)
 147         le32_to_cpus(&s->catalog_bitmap[i]);
 148
 149     s->data_offset = le32_to_cpu(bochs.header) + (s->catalog_size * 4);
 150
 151     s->bitmap_blocks = 1 + (le32_to_cpu(bochs.bitmap) - 1) / 512;
 152     s->extent_blocks = 1 + (le32_to_cpu(bochs.extent) - 1) / 512;
 153
 154     s->extent_size = le32_to_cpu(bochs.extent);
 155     if (s->extent_size < BDRV_SECTOR_SIZE) {
 156         /* bximage actually never creates extents smaller than 4k */
 157         error_setg(errp, "Extent size must be at least 512");
 158         ret = -EINVAL;
 159         goto fail;
 160     } else if (!is_power_of_2(s->extent_size)) {
 161         error_setg(errp, "Extent size %" PRIu32 " is not a power of two",
 162                    s->extent_size);
 163         ret = -EINVAL;
 164         goto fail;
 165     } else if (s->extent_size > 0x800000) {
 166         error_setg(errp, "Extent size %" PRIu32 " is too large",
 167                    s->extent_size);
 168         ret = -EINVAL;
 169         goto fail;
 170     }
 171
 172     if (s->catalog_size < DIV_ROUND_UP(bs->total_sectors,
 173                                        s->extent_size / BDRV_SECTOR_SIZE))
 174     {
 175         error_setg(errp, "Catalog size is too small for this disk size");
 176         ret = -EINVAL;
 177         goto fail;
 178     }
 179
 180     qemu_co_mutex_init(&s->lock);
 181     return 0;
 182
 183 fail:
 184     g_free(s->catalog_bitmap);
 185     return ret;
 186 }
 187
 188 static int64_t seek_to_sector(BlockDriverState *bs, int64_t sector_num)
 189 {
 190     BDRVBochsState *s = bs->opaque;
 191     uint64_t offset = sector_num * 512;
 192     uint64_t extent_index, extent_offset, bitmap_offset;
 193     char bitmap_entry;
 194     int ret;
 195
 196     // seek to sector
 197     extent_index = offset / s->extent_size;
 198     extent_offset = (offset % s->extent_size) / 512;
 199
 200     if (s->catalog_bitmap[extent_index] == 0xffffffff) {
 201         return 0; /* not allocated */
 202     }
 203
 204     bitmap_offset = s->data_offset +
 205         (512 * (uint64_t) s->catalog_bitmap[extent_index] *
 206         (s->extent_blocks + s->bitmap_blocks));
 207
 208     /* read in bitmap for current extent */
 209     ret = bdrv_pread(bs->file, bitmap_offset + (extent_offset / 8),
 210                      &bitmap_entry, 1);
 211     if (ret < 0) {
 212         return ret;
 213     }
 214
 215     if (!((bitmap_entry >> (extent_offset % 8)) & 1)) {
 216         return 0; /* not allocated */
 217     }
 218
 219     return bitmap_offset + (512 * (s->bitmap_blocks + extent_offset));
 220 }
 221
 222 static int bochs_read(BlockDriverState *bs, int64_t sector_num,
 223                     uint8_t *buf, int nb_sectors)
 224 {
 225     int ret;
 226
 227     while (nb_sectors > 0) {
 228         int64_t block_offset = seek_to_sector(bs, sector_num);
 229         if (block_offset < 0) {
 230             return block_offset;
 231         } else if (block_offset > 0) {
 232             ret = bdrv_pread(bs->file, block_offset, buf, 512);
 233             if (ret < 0) {
 234                 return ret;
 235             }
 236         } else {
 237             memset(buf, 0, 512);
 238         }
 239         nb_sectors--;
 240         sector_num++;
 241         buf += 512;
 242     }
 243     return 0;
 244 }
 245
 246 static coroutine_fn int bochs_co_read(BlockDriverState *bs, int64_t sector_num,
 247                                       uint8_t *buf, int nb_sectors)
 248 {
 249     int ret;
 250     BDRVBochsState *s = bs->opaque;
 251     qemu_co_mutex_lock(&s->lock);
 252     ret = bochs_read(bs, sector_num, buf, nb_sectors);
 253     qemu_co_mutex_unlock(&s->lock);
 254     return ret;
 255 }
 256
 257 static void bochs_close(BlockDriverState *bs)
 258 {
 259     BDRVBochsState *s = bs->opaque;
 260     g_free(s->catalog_bitmap);
 261 }
 262
 263 static BlockDriver bdrv_bochs = {
 264     .format_name        = "bochs",
 265     .instance_size      = sizeof(BDRVBochsState),
 266     .bdrv_probe         = bochs_probe,
 267     .bdrv_open          = bochs_open,
 268     .bdrv_read          = bochs_co_read,
 269     .bdrv_close         = bochs_close,
 270 };
 271
 272 static void bdrv_bochs_init(void)
 273 {
 274     bdrv_register(&bdrv_bochs);
 275 }
 276
 277 block_init(bdrv_bochs_init);