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_int.h"
  27 #include "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_v1 {
  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     union {
  50         struct {
  51             uint32_t catalog; // num of entries
  52             uint32_t bitmap; // bitmap size
  53             uint32_t extent; // extent size
  54             uint64_t disk; // disk size
  55             char padding[HEADER_SIZE - 64 - 8 - 20];
  56         } redolog;
  57         char padding[HEADER_SIZE - 64 - 8];
  58     } extra;
  59 };
  60
  61 // always little-endian
  62 struct bochs_header {
  63     char magic[32]; // "Bochs Virtual HD Image"
  64     char type[16]; // "Redolog"
  65     char subtype[16]; // "Undoable" / "Volatile" / "Growing"
  66     uint32_t version;
  67     uint32_t header; // size of header
  68
  69     union {
  70         struct {
  71             uint32_t catalog; // num of entries
  72             uint32_t bitmap; // bitmap size
  73             uint32_t extent; // extent size
  74             uint32_t reserved; // for ???
  75             uint64_t disk; // disk size
  76             char padding[HEADER_SIZE - 64 - 8 - 24];
  77         } redolog;
  78         char padding[HEADER_SIZE - 64 - 8];
  79     } extra;
  80 };
  81
  82 typedef struct BDRVBochsState {
  83     uint32_t *catalog_bitmap;
  84     int catalog_size;
  85
  86     int data_offset;
  87
  88     int bitmap_blocks;
  89     int extent_blocks;
  90     int extent_size;
  91 } BDRVBochsState;
  92
  93 static int bochs_probe(const uint8_t *buf, int buf_size, const char *filename)
  94 {
  95     const struct bochs_header *bochs = (const void *)buf;
  96
  97     if (buf_size < HEADER_SIZE)
  98         return 0;
  99
 100     if (!strcmp(bochs->magic, HEADER_MAGIC) &&
 101         !strcmp(bochs->type, REDOLOG_TYPE) &&
 102         !strcmp(bochs->subtype, GROWING_TYPE) &&
 103         ((le32_to_cpu(bochs->version) == HEADER_VERSION) ||
 104         (le32_to_cpu(bochs->version) == HEADER_V1)))
 105         return 100;
 106
 107     return 0;
 108 }
 109
 110 static int bochs_open(BlockDriverState *bs, int flags)
 111 {
 112     BDRVBochsState *s = bs->opaque;
 113     int i;
 114     struct bochs_header bochs;
 115     struct bochs_header_v1 header_v1;
 116
 117     bs->read_only = 1; // no write support yet
 118
 119     if (bdrv_pread(bs->file, 0, &bochs, sizeof(bochs)) != sizeof(bochs)) {
 120         goto fail;
 121     }
 122
 123     if (strcmp(bochs.magic, HEADER_MAGIC) ||
 124         strcmp(bochs.type, REDOLOG_TYPE) ||
 125         strcmp(bochs.subtype, GROWING_TYPE) ||
 126         ((le32_to_cpu(bochs.version) != HEADER_VERSION) &&
 127         (le32_to_cpu(bochs.version) != HEADER_V1))) {
 128         goto fail;
 129     }
 130
 131     if (le32_to_cpu(bochs.version) == HEADER_V1) {
 132       memcpy(&header_v1, &bochs, sizeof(bochs));
 133       bs->total_sectors = le64_to_cpu(header_v1.extra.redolog.disk) / 512;
 134     } else {
 135       bs->total_sectors = le64_to_cpu(bochs.extra.redolog.disk) / 512;
 136     }
 137
 138     s->catalog_size = le32_to_cpu(bochs.extra.redolog.catalog);
 139     s->catalog_bitmap = g_malloc(s->catalog_size * 4);
 140     if (bdrv_pread(bs->file, le32_to_cpu(bochs.header), s->catalog_bitmap,
 141                    s->catalog_size * 4) != s->catalog_size * 4)
 142         goto fail;
 143     for (i = 0; i < s->catalog_size; i++)
 144         le32_to_cpus(&s->catalog_bitmap[i]);
 145
 146     s->data_offset = le32_to_cpu(bochs.header) + (s->catalog_size * 4);
 147
 148     s->bitmap_blocks = 1 + (le32_to_cpu(bochs.extra.redolog.bitmap) - 1) / 512;
 149     s->extent_blocks = 1 + (le32_to_cpu(bochs.extra.redolog.extent) - 1) / 512;
 150
 151     s->extent_size = le32_to_cpu(bochs.extra.redolog.extent);
 152
 153     return 0;
 154  fail:
 155     return -1;
 156 }
 157
 158 static int64_t seek_to_sector(BlockDriverState *bs, int64_t sector_num)
 159 {
 160     BDRVBochsState *s = bs->opaque;
 161     int64_t offset = sector_num * 512;
 162     int64_t extent_index, extent_offset, bitmap_offset;
 163     char bitmap_entry;
 164
 165     // seek to sector
 166     extent_index = offset / s->extent_size;
 167     extent_offset = (offset % s->extent_size) / 512;
 168
 169     if (s->catalog_bitmap[extent_index] == 0xffffffff) {
 170         return -1; /* not allocated */
 171     }
 172
 173     bitmap_offset = s->data_offset + (512 * s->catalog_bitmap[extent_index] *
 174         (s->extent_blocks + s->bitmap_blocks));
 175
 176     /* read in bitmap for current extent */
 177     if (bdrv_pread(bs->file, bitmap_offset + (extent_offset / 8),
 178                    &bitmap_entry, 1) != 1) {
 179         return -1;
 180     }
 181
 182     if (!((bitmap_entry >> (extent_offset % 8)) & 1)) {
 183         return -1; /* not allocated */
 184     }
 185
 186     return bitmap_offset + (512 * (s->bitmap_blocks + extent_offset));
 187 }
 188
 189 static int bochs_read(BlockDriverState *bs, int64_t sector_num,
 190                     uint8_t *buf, int nb_sectors)
 191 {
 192     int ret;
 193
 194     while (nb_sectors > 0) {
 195         int64_t block_offset = seek_to_sector(bs, sector_num);
 196         if (block_offset >= 0) {
 197             ret = bdrv_pread(bs->file, block_offset, buf, 512);
 198             if (ret != 512) {
 199                 return -1;
 200             }
 201         } else
 202             memset(buf, 0, 512);
 203         nb_sectors--;
 204         sector_num++;
 205         buf += 512;
 206     }
 207     return 0;
 208 }
 209
 210 static void bochs_close(BlockDriverState *bs)
 211 {
 212     BDRVBochsState *s = bs->opaque;
 213     g_free(s->catalog_bitmap);
 214 }
 215
 216 static BlockDriver bdrv_bochs = {
 217     .format_name        = "bochs",
 218     .instance_size      = sizeof(BDRVBochsState),
 219     .bdrv_probe         = bochs_probe,
 220     .bdrv_open          = bochs_open,
 221     .bdrv_read          = bochs_read,
 222     .bdrv_close         = bochs_close,
 223 };
 224
 225 static void bdrv_bochs_init(void)
 226 {
 227     bdrv_register(&bdrv_bochs);
 228 }
 229
 230 block_init(bdrv_bochs_init);