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
  31 /**************************************************************/
  32
  33 #define HEADER_MAGIC "Bochs Virtual HD Image"
  34 #define HEADER_VERSION 0x00020000
  35 #define HEADER_V1 0x00010000
  36 #define HEADER_SIZE 512
  37
  38 #define REDOLOG_TYPE "Redolog"
  39 #define GROWING_TYPE "Growing"
  40
  41 // not allocated: 0xffffffff
  42
  43 // always little-endian
  44 struct bochs_header {
  45     char magic[32];     /* "Bochs Virtual HD Image" */
  46     char type[16];      /* "Redolog" */
  47     char subtype[16];   /* "Undoable" / "Volatile" / "Growing" */
  48     uint32_t version;
  49     uint32_t header;    /* size of header */
  50
  51     uint32_t catalog;   /* num of entries */
  52     uint32_t bitmap;    /* bitmap size */
  53     uint32_t extent;    /* extent size */
  54
  55     union {
  56         struct {
  57             uint32_t reserved;  /* for ??? */
  58             uint64_t disk;      /* disk size */
  59             char padding[HEADER_SIZE - 64 - 20 - 12];
  60         } QEMU_PACKED redolog;
  61         struct {
  62             uint64_t disk;      /* disk size */
  63             char padding[HEADER_SIZE - 64 - 20 - 8];
  64         } QEMU_PACKED redolog_v1;
  65         char padding[HEADER_SIZE - 64 - 20];
  66     } extra;
  67 } QEMU_PACKED;
  68
  69 typedef struct BDRVBochsState {
  70     CoMutex lock;
  71     uint32_t *catalog_bitmap;
  72     uint32_t catalog_size;
  73
  74     uint32_t data_offset;
  75
  76     uint32_t bitmap_blocks;
  77     uint32_t extent_blocks;
  78     uint32_t extent_size;
  79 } BDRVBochsState;
  80
  81 static int bochs_probe(const uint8_t *buf, int buf_size, const char *filename)
  82 {
  83     const struct bochs_header *bochs = (const void *)buf;
  84
  85     if (buf_size < HEADER_SIZE)
  86         return 0;
  87
  88     if (!strcmp(bochs->magic, HEADER_MAGIC) &&
  89         !strcmp(bochs->type, REDOLOG_TYPE) &&
  90         !strcmp(bochs->subtype, GROWING_TYPE) &&
  91         ((le32_to_cpu(bochs->version) == HEADER_VERSION) ||
  92         (le32_to_cpu(bochs->version) == HEADER_V1)))
  93         return 100;
  94
  95     return 0;
  96 }
  97
  98 static int bochs_open(BlockDriverState *bs, QDict *options, int flags,
  99                       Error **errp)
 100 {
 101     BDRVBochsState *s = bs->opaque;
 102     uint32_t i;
 103     struct bochs_header bochs;
 104     int ret;
 105
 106     bs->read_only = 1; // no write support yet
 107
 108     ret = bdrv_pread(bs->file->bs, 0, &bochs, sizeof(bochs));
 109     if (ret < 0) {
 110         return ret;
 111     }
 112
 113     if (strcmp(bochs.magic, HEADER_MAGIC) ||
 114         strcmp(bochs.type, REDOLOG_TYPE) ||
 115         strcmp(bochs.subtype, GROWING_TYPE) ||
 116         ((le32_to_cpu(bochs.version) != HEADER_VERSION) &&
 117         (le32_to_cpu(bochs.version) != HEADER_V1))) {
 118         error_setg(errp, "Image not in Bochs format");
 119         return -EINVAL;
 120     }
 121
 122     if (le32_to_cpu(bochs.version) == HEADER_V1) {
 123         bs->total_sectors = le64_to_cpu(bochs.extra.redolog_v1.disk) / 512;
 124     } else {
 125         bs->total_sectors = le64_to_cpu(bochs.extra.redolog.disk) / 512;
 126     }
 127
 128     /* Limit to 1M entries to avoid unbounded allocation. This is what is
 129      * needed for the largest image that bximage can create (~8 TB). */
 130     s->catalog_size = le32_to_cpu(bochs.catalog);
 131     if (s->catalog_size > 0x100000) {
 132         error_setg(errp, "Catalog size is too large");
 133         return -EFBIG;
 134     }
 135
 136     s->catalog_bitmap = g_try_new(uint32_t, s->catalog_size);
 137     if (s->catalog_size && s->catalog_bitmap == NULL) {
 138         error_setg(errp, "Could not allocate memory for catalog");
 139         return -ENOMEM;
 140     }
 141
 142     ret = bdrv_pread(bs->file->bs, le32_to_cpu(bochs.header), s->catalog_bitmap,
 143                      s->catalog_size * 4);
 144     if (ret < 0) {
 145         goto fail;
 146     }
 147
 148     for (i = 0; i < s->catalog_size; i++)
 149         le32_to_cpus(&s->catalog_bitmap[i]);
 150
 151     s->data_offset = le32_to_cpu(bochs.header) + (s->catalog_size * 4);
 152
 153     s->bitmap_blocks = 1 + (le32_to_cpu(bochs.bitmap) - 1) / 512;
 154     s->extent_blocks = 1 + (le32_to_cpu(bochs.extent) - 1) / 512;
 155
 156     s->extent_size = le32_to_cpu(bochs.extent);
 157     if (s->extent_size < BDRV_SECTOR_SIZE) {
 158         /* bximage actually never creates extents smaller than 4k */
 159         error_setg(errp, "Extent size must be at least 512");
 160         ret = -EINVAL;
 161         goto fail;
 162     } else if (!is_power_of_2(s->extent_size)) {
 163         error_setg(errp, "Extent size %" PRIu32 " is not a power of two",
 164                    s->extent_size);
 165         ret = -EINVAL;
 166         goto fail;
 167     } else if (s->extent_size > 0x800000) {
 168         error_setg(errp, "Extent size %" PRIu32 " is too large",
 169                    s->extent_size);
 170         ret = -EINVAL;
 171         goto fail;
 172     }
 173
 174     if (s->catalog_size < DIV_ROUND_UP(bs->total_sectors,
 175                                        s->extent_size / BDRV_SECTOR_SIZE))
 176     {
 177         error_setg(errp, "Catalog size is too small for this disk size");
 178         ret = -EINVAL;
 179         goto fail;
 180     }
 181
 182     qemu_co_mutex_init(&s->lock);
 183     return 0;
 184
 185 fail:
 186     g_free(s->catalog_bitmap);
 187     return ret;
 188 }
 189
 190 static int64_t seek_to_sector(BlockDriverState *bs, int64_t sector_num)
 191 {
 192     BDRVBochsState *s = bs->opaque;
 193     uint64_t offset = sector_num * 512;
 194     uint64_t extent_index, extent_offset, bitmap_offset;
 195     char bitmap_entry;
 196     int ret;
 197
 198     // seek to sector
 199     extent_index = offset / s->extent_size;
 200     extent_offset = (offset % s->extent_size) / 512;
 201
 202     if (s->catalog_bitmap[extent_index] == 0xffffffff) {
 203         return 0; /* not allocated */
 204     }
 205
 206     bitmap_offset = s->data_offset +
 207         (512 * (uint64_t) s->catalog_bitmap[extent_index] *
 208         (s->extent_blocks + s->bitmap_blocks));
 209
 210     /* read in bitmap for current extent */
 211     ret = bdrv_pread(bs->file->bs, bitmap_offset + (extent_offset / 8),
 212                      &bitmap_entry, 1);
 213     if (ret < 0) {
 214         return ret;
 215     }
 216
 217     if (!((bitmap_entry >> (extent_offset % 8)) & 1)) {
 218         return 0; /* not allocated */
 219     }
 220
 221     return bitmap_offset + (512 * (s->bitmap_blocks + extent_offset));
 222 }
 223
 224 static int bochs_read(BlockDriverState *bs, int64_t sector_num,
 225                     uint8_t *buf, int nb_sectors)
 226 {
 227     int ret;
 228
 229     while (nb_sectors > 0) {
 230         int64_t block_offset = seek_to_sector(bs, sector_num);
 231         if (block_offset < 0) {
 232             return block_offset;
 233         } else if (block_offset > 0) {
 234             ret = bdrv_pread(bs->file->bs, block_offset, buf, 512);
 235             if (ret < 0) {
 236                 return ret;
 237             }
 238         } else {
 239             memset(buf, 0, 512);
 240         }
 241         nb_sectors--;
 242         sector_num++;
 243         buf += 512;
 244     }
 245     return 0;
 246 }
 247
 248 static coroutine_fn int bochs_co_read(BlockDriverState *bs, int64_t sector_num,
 249                                       uint8_t *buf, int nb_sectors)
 250 {
 251     int ret;
 252     BDRVBochsState *s = bs->opaque;
 253     qemu_co_mutex_lock(&s->lock);
 254     ret = bochs_read(bs, sector_num, buf, nb_sectors);
 255     qemu_co_mutex_unlock(&s->lock);
 256     return ret;
 257 }
 258
 259 static void bochs_close(BlockDriverState *bs)
 260 {
 261     BDRVBochsState *s = bs->opaque;
 262     g_free(s->catalog_bitmap);
 263 }
 264
 265 static BlockDriver bdrv_bochs = {
 266     .format_name        = "bochs",
 267     .instance_size      = sizeof(BDRVBochsState),
 268     .bdrv_probe         = bochs_probe,
 269     .bdrv_open          = bochs_open,
 270     .bdrv_read          = bochs_co_read,
 271     .bdrv_close         = bochs_close,
 272 };
 273
 274 static void bdrv_bochs_init(void)
 275 {
 276     bdrv_register(&bdrv_bochs);
 277 }
 278
 279 block_init(bdrv_bochs_init);