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 "vl.h"
  26 #include "block_int.h"
  27
  28 /**************************************************************/
  29
  30 #define HEADER_MAGIC "Bochs Virtual HD Image"
  31 #define HEADER_VERSION 0x00010000
  32 #define HEADER_SIZE 512
  33
  34 #define REDOLOG_TYPE "Redolog"
  35 #define GROWING_TYPE "Growing"
  36
  37 // not allocated: 0xffffffff
  38
  39 // always little-endian
  40 struct bochs_header {
  41     char magic[32]; // "Bochs Virtual HD Image"
  42     char type[16]; // "Redolog"
  43     char subtype[16]; // "Undoable" / "Volatile" / "Growing"
  44     uint32_t version;
  45     uint32_t header; // size of header
  46
  47     union {
  48         struct {
  49             uint32_t catalog; // num of entries
  50             uint32_t bitmap; // bitmap size
  51             uint32_t extent; // extent size
  52             uint64_t disk; // disk size
  53             char padding[HEADER_SIZE - 64 - 8 - 20];
  54         } redolog;
  55         char padding[HEADER_SIZE - 64 - 8];
  56     } extra;
  57 };
  58
  59 typedef struct BDRVBochsState {
  60     int fd;
  61
  62     uint32_t *catalog_bitmap;
  63     int catalog_size;
  64
  65     int data_offset;
  66
  67     int bitmap_blocks;
  68     int extent_blocks;
  69     int extent_size;
  70 } BDRVBochsState;
  71
  72 static int bochs_probe(const uint8_t *buf, int buf_size, const char *filename)
  73 {
  74     const struct bochs_header *bochs = (const void *)buf;
  75
  76     if (buf_size < HEADER_SIZE)
  77         return 0;
  78
  79     if (!strcmp(bochs->magic, HEADER_MAGIC) &&
  80         !strcmp(bochs->type, REDOLOG_TYPE) &&
  81         !strcmp(bochs->subtype, GROWING_TYPE) &&
  82         (le32_to_cpu(bochs->version) == HEADER_VERSION))
  83         return 100;
  84
  85     return 0;
  86 }
  87
  88 static int bochs_open(BlockDriverState *bs, const char *filename)
  89 {
  90     BDRVBochsState *s = bs->opaque;
  91     int fd, i;
  92     struct bochs_header bochs;
  93
  94     fd = open(filename, O_RDWR | O_BINARY | O_LARGEFILE);
  95     if (fd < 0) {
  96         fd = open(filename, O_RDONLY | O_BINARY | O_LARGEFILE);
  97         if (fd < 0)
  98             return -1;
  99     }
 100
 101     bs->read_only = 1; // no write support yet
 102
 103     s->fd = fd;
 104
 105     if (read(fd, &bochs, sizeof(bochs)) != sizeof(bochs)) {
 106         goto fail;
 107     }
 108
 109     if (strcmp(bochs.magic, HEADER_MAGIC) ||
 110         strcmp(bochs.type, REDOLOG_TYPE) ||
 111         strcmp(bochs.subtype, GROWING_TYPE) ||
 112         (le32_to_cpu(bochs.version) != HEADER_VERSION)) {
 113         goto fail;
 114     }
 115
 116     bs->total_sectors = le64_to_cpu(bochs.extra.redolog.disk) / 512;
 117
 118     lseek(s->fd, le32_to_cpu(bochs.header), SEEK_SET);
 119
 120     s->catalog_size = le32_to_cpu(bochs.extra.redolog.catalog);
 121     s->catalog_bitmap = qemu_malloc(s->catalog_size * 4);
 122     if (!s->catalog_bitmap)
 123         goto fail;
 124     if (read(s->fd, s->catalog_bitmap, s->catalog_size * 4) !=
 125         s->catalog_size * 4)
 126         goto fail;
 127     for (i = 0; i < s->catalog_size; i++)
 128         le32_to_cpus(&s->catalog_bitmap[i]);
 129
 130     s->data_offset = le32_to_cpu(bochs.header) + (s->catalog_size * 4);
 131
 132     s->bitmap_blocks = 1 + (le32_to_cpu(bochs.extra.redolog.bitmap) - 1) / 512;
 133     s->extent_blocks = 1 + (le32_to_cpu(bochs.extra.redolog.extent) - 1) / 512;
 134
 135     s->extent_size = le32_to_cpu(bochs.extra.redolog.extent);
 136
 137     return 0;
 138  fail:
 139     close(fd);
 140     return -1;
 141 }
 142
 143 static inline int seek_to_sector(BlockDriverState *bs, int64_t sector_num)
 144 {
 145     BDRVBochsState *s = bs->opaque;
 146     int64_t offset = sector_num * 512;
 147     int64_t extent_index, extent_offset, bitmap_offset, block_offset;
 148     char bitmap_entry;
 149
 150     // seek to sector
 151     extent_index = offset / s->extent_size;
 152     extent_offset = (offset % s->extent_size) / 512;
 153
 154     if (s->catalog_bitmap[extent_index] == 0xffffffff)
 155     {
 156 //      fprintf(stderr, "page not allocated [%x - %x:%x]\n",
 157 //          sector_num, extent_index, extent_offset);
 158         return -1; // not allocated
 159     }
 160
 161     bitmap_offset = s->data_offset + (512 * s->catalog_bitmap[extent_index] *
 162         (s->extent_blocks + s->bitmap_blocks));
 163     block_offset = bitmap_offset + (512 * (s->bitmap_blocks + extent_offset));
 164
 165 //    fprintf(stderr, "sect: %x [ext i: %x o: %x] -> %x bitmap: %x block: %x\n",
 166 //      sector_num, extent_index, extent_offset,
 167 //      le32_to_cpu(s->catalog_bitmap[extent_index]),
 168 //      bitmap_offset, block_offset);
 169
 170     // read in bitmap for current extent
 171     lseek(s->fd, bitmap_offset + (extent_offset / 8), SEEK_SET);
 172
 173     read(s->fd, &bitmap_entry, 1);
 174
 175     if (!((bitmap_entry >> (extent_offset % 8)) & 1))
 176     {
 177 //      fprintf(stderr, "sector (%x) in bitmap not allocated\n",
 178 //          sector_num);
 179         return -1; // not allocated
 180     }
 181
 182     lseek(s->fd, block_offset, SEEK_SET);
 183
 184     return 0;
 185 }
 186
 187 static int bochs_read(BlockDriverState *bs, int64_t sector_num,
 188                     uint8_t *buf, int nb_sectors)
 189 {
 190     BDRVBochsState *s = bs->opaque;
 191     int ret;
 192
 193     while (nb_sectors > 0) {
 194         if (!seek_to_sector(bs, sector_num))
 195         {
 196             ret = read(s->fd, buf, 512);
 197             if (ret != 512)
 198                 return -1;
 199         }
 200         else
 201             memset(buf, 0, 512);
 202         nb_sectors--;
 203         sector_num++;
 204         buf += 512;
 205     }
 206     return 0;
 207 }
 208
 209 static void bochs_close(BlockDriverState *bs)
 210 {
 211     BDRVBochsState *s = bs->opaque;
 212     qemu_free(s->catalog_bitmap);
 213     close(s->fd);
 214 }
 215
 216 BlockDriver bdrv_bochs = {
 217     "bochs",
 218     sizeof(BDRVBochsState),
 219     bochs_probe,
 220     bochs_open,
 221     bochs_read,
 222     NULL,
 223     bochs_close,
 224 };