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
  28 /**************************************************************/
  29
  30 #define HEADER_MAGIC "Bochs Virtual HD Image"
  31 #define HEADER_VERSION 0x00020000
  32 #define HEADER_V1 0x00010000
  33 #define HEADER_SIZE 512
  34
  35 #define REDOLOG_TYPE "Redolog"
  36 #define GROWING_TYPE "Growing"
  37
  38 // not allocated: 0xffffffff
  39
  40 // always little-endian
  41 struct bochs_header_v1 {
  42     char magic[32]; // "Bochs Virtual HD Image"
  43     char type[16]; // "Redolog"
  44     char subtype[16]; // "Undoable" / "Volatile" / "Growing"
  45     uint32_t version;
  46     uint32_t header; // size of header
  47
  48     union {
  49         struct {
  50             uint32_t catalog; // num of entries
  51             uint32_t bitmap; // bitmap size
  52             uint32_t extent; // extent size
  53             uint64_t disk; // disk size
  54             char padding[HEADER_SIZE - 64 - 8 - 20];
  55         } redolog;
  56         char padding[HEADER_SIZE - 64 - 8];
  57     } extra;
  58 };
  59
  60 // always little-endian
  61 struct bochs_header {
  62     char magic[32]; // "Bochs Virtual HD Image"
  63     char type[16]; // "Redolog"
  64     char subtype[16]; // "Undoable" / "Volatile" / "Growing"
  65     uint32_t version;
  66     uint32_t header; // size of header
  67
  68     union {
  69         struct {
  70             uint32_t catalog; // num of entries
  71             uint32_t bitmap; // bitmap size
  72             uint32_t extent; // extent size
  73             uint32_t reserved; // for ???
  74             uint64_t disk; // disk size
  75             char padding[HEADER_SIZE - 64 - 8 - 24];
  76         } redolog;
  77         char padding[HEADER_SIZE - 64 - 8];
  78     } extra;
  79 };
  80
  81 typedef struct BDRVBochsState {
  82     int fd;
  83
  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, const char *filename, int flags)
 112 {
 113     BDRVBochsState *s = bs->opaque;
 114     int fd, i;
 115     struct bochs_header bochs;
 116     struct bochs_header_v1 header_v1;
 117
 118     fd = open(filename, O_RDWR | O_BINARY);
 119     if (fd < 0) {
 120         fd = open(filename, O_RDONLY | O_BINARY);
 121         if (fd < 0)
 122             return -1;
 123     }
 124
 125     bs->read_only = 1; // no write support yet
 126
 127     s->fd = fd;
 128
 129     if (read(fd, &bochs, sizeof(bochs)) != sizeof(bochs)) {
 130         goto fail;
 131     }
 132
 133     if (strcmp(bochs.magic, HEADER_MAGIC) ||
 134         strcmp(bochs.type, REDOLOG_TYPE) ||
 135         strcmp(bochs.subtype, GROWING_TYPE) ||
 136         ((le32_to_cpu(bochs.version) != HEADER_VERSION) &&
 137         (le32_to_cpu(bochs.version) != HEADER_V1))) {
 138         goto fail;
 139     }
 140
 141     if (le32_to_cpu(bochs.version) == HEADER_V1) {
 142       memcpy(&header_v1, &bochs, sizeof(bochs));
 143       bs->total_sectors = le64_to_cpu(header_v1.extra.redolog.disk) / 512;
 144     } else {
 145       bs->total_sectors = le64_to_cpu(bochs.extra.redolog.disk) / 512;
 146     }
 147
 148     lseek(s->fd, le32_to_cpu(bochs.header), SEEK_SET);
 149
 150     s->catalog_size = le32_to_cpu(bochs.extra.redolog.catalog);
 151     s->catalog_bitmap = qemu_malloc(s->catalog_size * 4);
 152     if (read(s->fd, s->catalog_bitmap, s->catalog_size * 4) !=
 153         s->catalog_size * 4)
 154         goto fail;
 155     for (i = 0; i < s->catalog_size; i++)
 156         le32_to_cpus(&s->catalog_bitmap[i]);
 157
 158     s->data_offset = le32_to_cpu(bochs.header) + (s->catalog_size * 4);
 159
 160     s->bitmap_blocks = 1 + (le32_to_cpu(bochs.extra.redolog.bitmap) - 1) / 512;
 161     s->extent_blocks = 1 + (le32_to_cpu(bochs.extra.redolog.extent) - 1) / 512;
 162
 163     s->extent_size = le32_to_cpu(bochs.extra.redolog.extent);
 164
 165     return 0;
 166  fail:
 167     close(fd);
 168     return -1;
 169 }
 170
 171 static inline int seek_to_sector(BlockDriverState *bs, int64_t sector_num)
 172 {
 173     BDRVBochsState *s = bs->opaque;
 174     int64_t offset = sector_num * 512;
 175     int64_t extent_index, extent_offset, bitmap_offset, block_offset;
 176     char bitmap_entry;
 177
 178     // seek to sector
 179     extent_index = offset / s->extent_size;
 180     extent_offset = (offset % s->extent_size) / 512;
 181
 182     if (s->catalog_bitmap[extent_index] == 0xffffffff)
 183     {
 184 //      fprintf(stderr, "page not allocated [%x - %x:%x]\n",
 185 //          sector_num, extent_index, extent_offset);
 186         return -1; // not allocated
 187     }
 188
 189     bitmap_offset = s->data_offset + (512 * s->catalog_bitmap[extent_index] *
 190         (s->extent_blocks + s->bitmap_blocks));
 191     block_offset = bitmap_offset + (512 * (s->bitmap_blocks + extent_offset));
 192
 193 //    fprintf(stderr, "sect: %x [ext i: %x o: %x] -> %x bitmap: %x block: %x\n",
 194 //      sector_num, extent_index, extent_offset,
 195 //      le32_to_cpu(s->catalog_bitmap[extent_index]),
 196 //      bitmap_offset, block_offset);
 197
 198     // read in bitmap for current extent
 199     lseek(s->fd, bitmap_offset + (extent_offset / 8), SEEK_SET);
 200
 201     read(s->fd, &bitmap_entry, 1);
 202
 203     if (!((bitmap_entry >> (extent_offset % 8)) & 1))
 204     {
 205 //      fprintf(stderr, "sector (%x) in bitmap not allocated\n",
 206 //          sector_num);
 207         return -1; // not allocated
 208     }
 209
 210     lseek(s->fd, block_offset, SEEK_SET);
 211
 212     return 0;
 213 }
 214
 215 static int bochs_read(BlockDriverState *bs, int64_t sector_num,
 216                     uint8_t *buf, int nb_sectors)
 217 {
 218     BDRVBochsState *s = bs->opaque;
 219     int ret;
 220
 221     while (nb_sectors > 0) {
 222         if (!seek_to_sector(bs, sector_num))
 223         {
 224             ret = read(s->fd, buf, 512);
 225             if (ret != 512)
 226                 return -1;
 227         }
 228         else
 229             memset(buf, 0, 512);
 230         nb_sectors--;
 231         sector_num++;
 232         buf += 512;
 233     }
 234     return 0;
 235 }
 236
 237 static void bochs_close(BlockDriverState *bs)
 238 {
 239     BDRVBochsState *s = bs->opaque;
 240     qemu_free(s->catalog_bitmap);
 241     close(s->fd);
 242 }
 243
 244 BlockDriver bdrv_bochs = {
 245     "bochs",
 246     sizeof(BDRVBochsState),
 247     bochs_probe,
 248     bochs_open,
 249     bochs_read,
 250     NULL,
 251     bochs_close,
 252 };