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