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_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     CoMutex lock;
  84     uint32_t *catalog_bitmap;
  85     int catalog_size;
  86
  87     int data_offset;
  88
  89     int bitmap_blocks;
  90     int extent_blocks;
  91     int extent_size;
  92 } BDRVBochsState;
  93
  94 static int bochs_probe(const uint8_t *buf, int buf_size, const char *filename)
  95 {
  96     const struct bochs_header *bochs = (const void *)buf;
  97
  98     if (buf_size < HEADER_SIZE)
  99         return 0;
 100
 101     if (!strcmp(bochs->magic, HEADER_MAGIC) &&
 102         !strcmp(bochs->type, REDOLOG_TYPE) &&
 103         !strcmp(bochs->subtype, GROWING_TYPE) &&
 104         ((le32_to_cpu(bochs->version) == HEADER_VERSION) ||
 105         (le32_to_cpu(bochs->version) == HEADER_V1)))
 106         return 100;
 107
 108     return 0;
 109 }
 110
 111 static int bochs_open(BlockDriverState *bs, int flags)
 112 {
 113     BDRVBochsState *s = bs->opaque;
 114     int i;
 115     struct bochs_header bochs;
 116     struct bochs_header_v1 header_v1;
 117
 118     bs->read_only = 1; // no write support yet
 119
 120     if (bdrv_pread(bs->file, 0, &bochs, sizeof(bochs)) != sizeof(bochs)) {
 121         goto fail;
 122     }
 123
 124     if (strcmp(bochs.magic, HEADER_MAGIC) ||
 125         strcmp(bochs.type, REDOLOG_TYPE) ||
 126         strcmp(bochs.subtype, GROWING_TYPE) ||
 127         ((le32_to_cpu(bochs.version) != HEADER_VERSION) &&
 128         (le32_to_cpu(bochs.version) != HEADER_V1))) {
 129         goto fail;
 130     }
 131
 132     if (le32_to_cpu(bochs.version) == HEADER_V1) {
 133       memcpy(&header_v1, &bochs, sizeof(bochs));
 134       bs->total_sectors = le64_to_cpu(header_v1.extra.redolog.disk) / 512;
 135     } else {
 136       bs->total_sectors = le64_to_cpu(bochs.extra.redolog.disk) / 512;
 137     }
 138
 139     s->catalog_size = le32_to_cpu(bochs.extra.redolog.catalog);
 140     s->catalog_bitmap = g_malloc(s->catalog_size * 4);
 141     if (bdrv_pread(bs->file, le32_to_cpu(bochs.header), s->catalog_bitmap,
 142                    s->catalog_size * 4) != s->catalog_size * 4)
 143         goto fail;
 144     for (i = 0; i < s->catalog_size; i++)
 145         le32_to_cpus(&s->catalog_bitmap[i]);
 146
 147     s->data_offset = le32_to_cpu(bochs.header) + (s->catalog_size * 4);
 148
 149     s->bitmap_blocks = 1 + (le32_to_cpu(bochs.extra.redolog.bitmap) - 1) / 512;
 150     s->extent_blocks = 1 + (le32_to_cpu(bochs.extra.redolog.extent) - 1) / 512;
 151
 152     s->extent_size = le32_to_cpu(bochs.extra.redolog.extent);
 153
 154     qemu_co_mutex_init(&s->lock);
 155     return 0;
 156  fail:
 157     return -1;
 158 }
 159
 160 static int64_t seek_to_sector(BlockDriverState *bs, int64_t sector_num)
 161 {
 162     BDRVBochsState *s = bs->opaque;
 163     int64_t offset = sector_num * 512;
 164     int64_t extent_index, extent_offset, bitmap_offset;
 165     char bitmap_entry;
 166
 167     // seek to sector
 168     extent_index = offset / s->extent_size;
 169     extent_offset = (offset % s->extent_size) / 512;
 170
 171     if (s->catalog_bitmap[extent_index] == 0xffffffff) {
 172         return -1; /* not allocated */
 173     }
 174
 175     bitmap_offset = s->data_offset + (512 * s->catalog_bitmap[extent_index] *
 176         (s->extent_blocks + s->bitmap_blocks));
 177
 178     /* read in bitmap for current extent */
 179     if (bdrv_pread(bs->file, bitmap_offset + (extent_offset / 8),
 180                    &bitmap_entry, 1) != 1) {
 181         return -1;
 182     }
 183
 184     if (!((bitmap_entry >> (extent_offset % 8)) & 1)) {
 185         return -1; /* not allocated */
 186     }
 187
 188     return bitmap_offset + (512 * (s->bitmap_blocks + extent_offset));
 189 }
 190
 191 static int bochs_read(BlockDriverState *bs, int64_t sector_num,
 192                     uint8_t *buf, int nb_sectors)
 193 {
 194     int ret;
 195
 196     while (nb_sectors > 0) {
 197         int64_t block_offset = seek_to_sector(bs, sector_num);
 198         if (block_offset >= 0) {
 199             ret = bdrv_pread(bs->file, block_offset, buf, 512);
 200             if (ret != 512) {
 201                 return -1;
 202             }
 203         } else
 204             memset(buf, 0, 512);
 205         nb_sectors--;
 206         sector_num++;
 207         buf += 512;
 208     }
 209     return 0;
 210 }
 211
 212 static coroutine_fn int bochs_co_read(BlockDriverState *bs, int64_t sector_num,
 213                                       uint8_t *buf, int nb_sectors)
 214 {
 215     int ret;
 216     BDRVBochsState *s = bs->opaque;
 217     qemu_co_mutex_lock(&s->lock);
 218     ret = bochs_read(bs, sector_num, buf, nb_sectors);
 219     qemu_co_mutex_unlock(&s->lock);
 220     return ret;
 221 }
 222
 223 static void bochs_close(BlockDriverState *bs)
 224 {
 225     BDRVBochsState *s = bs->opaque;
 226     g_free(s->catalog_bitmap);
 227 }
 228
 229 static BlockDriver bdrv_bochs = {
 230     .format_name        = "bochs",
 231     .instance_size      = sizeof(BDRVBochsState),
 232     .bdrv_probe         = bochs_probe,
 233     .bdrv_open          = bochs_open,
 234     .bdrv_read          = bochs_co_read,
 235     .bdrv_close         = bochs_close,
 236 };
 237
 238 static void bdrv_bochs_init(void)
 239 {
 240     bdrv_register(&bdrv_bochs);
 241 }
 242
 243 block_init(bdrv_bochs_init);