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/osdep.h"
  26 #include "qemu-common.h"
  27 #include "block/block_int.h"
  28 #include "qemu/module.h"
  29
  30 /**************************************************************/
  31
  32 #define HEADER_MAGIC "Bochs Virtual HD Image"
  33 #define HEADER_VERSION 0x00020000
  34 #define HEADER_V1 0x00010000
  35 #define HEADER_SIZE 512
  36
  37 #define REDOLOG_TYPE "Redolog"
  38 #define GROWING_TYPE "Growing"
  39
  40 // not allocated: 0xffffffff
  41
  42 // always little-endian
  43 struct bochs_header {
  44     char magic[32];     /* "Bochs Virtual HD Image" */
  45     char type[16];      /* "Redolog" */
  46     char subtype[16];   /* "Undoable" / "Volatile" / "Growing" */
  47     uint32_t version;
  48     uint32_t header;    /* size of header */
  49
  50     uint32_t catalog;   /* num of entries */
  51     uint32_t bitmap;    /* bitmap size */
  52     uint32_t extent;    /* extent size */
  53
  54     union {
  55         struct {
  56             uint32_t reserved;  /* for ??? */
  57             uint64_t disk;      /* disk size */
  58             char padding[HEADER_SIZE - 64 - 20 - 12];
  59         } QEMU_PACKED redolog;
  60         struct {
  61             uint64_t disk;      /* disk size */
  62             char padding[HEADER_SIZE - 64 - 20 - 8];
  63         } QEMU_PACKED redolog_v1;
  64         char padding[HEADER_SIZE - 64 - 20];
  65     } extra;
  66 } QEMU_PACKED;
  67
  68 typedef struct BDRVBochsState {
  69     CoMutex lock;
  70     uint32_t *catalog_bitmap;
  71     uint32_t catalog_size;
  72
  73     uint32_t data_offset;
  74
  75     uint32_t bitmap_blocks;
  76     uint32_t extent_blocks;
  77     uint32_t extent_size;
  78 } BDRVBochsState;
  79
  80 static int bochs_probe(const uint8_t *buf, int buf_size, const char *filename)
  81 {
  82     const struct bochs_header *bochs = (const void *)buf;
  83
  84     if (buf_size < HEADER_SIZE)
  85         return 0;
  86
  87     if (!strcmp(bochs->magic, HEADER_MAGIC) &&
  88         !strcmp(bochs->type, REDOLOG_TYPE) &&
  89         !strcmp(bochs->subtype, GROWING_TYPE) &&
  90         ((le32_to_cpu(bochs->version) == HEADER_VERSION) ||
  91         (le32_to_cpu(bochs->version) == HEADER_V1)))
  92         return 100;
  93
  94     return 0;
  95 }
  96
  97 static int bochs_open(BlockDriverState *bs, QDict *options, int flags,
  98                       Error **errp)
  99 {
 100     BDRVBochsState *s = bs->opaque;
 101     uint32_t i;
 102     struct bochs_header bochs;
 103     int ret;
 104
 105     bs->read_only = 1; // no write support yet
 106
 107     ret = bdrv_pread(bs->file->bs, 0, &bochs, sizeof(bochs));
 108     if (ret < 0) {
 109         return ret;
 110     }
 111
 112     if (strcmp(bochs.magic, HEADER_MAGIC) ||
 113         strcmp(bochs.type, REDOLOG_TYPE) ||
 114         strcmp(bochs.subtype, GROWING_TYPE) ||
 115         ((le32_to_cpu(bochs.version) != HEADER_VERSION) &&
 116         (le32_to_cpu(bochs.version) != HEADER_V1))) {
 117         error_setg(errp, "Image not in Bochs format");
 118         return -EINVAL;
 119     }
 120
 121     if (le32_to_cpu(bochs.version) == HEADER_V1) {
 122         bs->total_sectors = le64_to_cpu(bochs.extra.redolog_v1.disk) / 512;
 123     } else {
 124         bs->total_sectors = le64_to_cpu(bochs.extra.redolog.disk) / 512;
 125     }
 126
 127     /* Limit to 1M entries to avoid unbounded allocation. This is what is
 128      * needed for the largest image that bximage can create (~8 TB). */
 129     s->catalog_size = le32_to_cpu(bochs.catalog);
 130     if (s->catalog_size > 0x100000) {
 131         error_setg(errp, "Catalog size is too large");
 132         return -EFBIG;
 133     }
 134
 135     s->catalog_bitmap = g_try_new(uint32_t, s->catalog_size);
 136     if (s->catalog_size && s->catalog_bitmap == NULL) {
 137         error_setg(errp, "Could not allocate memory for catalog");
 138         return -ENOMEM;
 139     }
 140
 141     ret = bdrv_pread(bs->file->bs, le32_to_cpu(bochs.header), s->catalog_bitmap,
 142                      s->catalog_size * 4);
 143     if (ret < 0) {
 144         goto fail;
 145     }
 146
 147     for (i = 0; i < s->catalog_size; i++)
 148         le32_to_cpus(&s->catalog_bitmap[i]);
 149
 150     s->data_offset = le32_to_cpu(bochs.header) + (s->catalog_size * 4);
 151
 152     s->bitmap_blocks = 1 + (le32_to_cpu(bochs.bitmap) - 1) / 512;
 153     s->extent_blocks = 1 + (le32_to_cpu(bochs.extent) - 1) / 512;
 154
 155     s->extent_size = le32_to_cpu(bochs.extent);
 156     if (s->extent_size < BDRV_SECTOR_SIZE) {
 157         /* bximage actually never creates extents smaller than 4k */
 158         error_setg(errp, "Extent size must be at least 512");
 159         ret = -EINVAL;
 160         goto fail;
 161     } else if (!is_power_of_2(s->extent_size)) {
 162         error_setg(errp, "Extent size %" PRIu32 " is not a power of two",
 163                    s->extent_size);
 164         ret = -EINVAL;
 165         goto fail;
 166     } else if (s->extent_size > 0x800000) {
 167         error_setg(errp, "Extent size %" PRIu32 " is too large",
 168                    s->extent_size);
 169         ret = -EINVAL;
 170         goto fail;
 171     }
 172
 173     if (s->catalog_size < DIV_ROUND_UP(bs->total_sectors,
 174                                        s->extent_size / BDRV_SECTOR_SIZE))
 175     {
 176         error_setg(errp, "Catalog size is too small for this disk size");
 177         ret = -EINVAL;
 178         goto fail;
 179     }
 180
 181     qemu_co_mutex_init(&s->lock);
 182     return 0;
 183
 184 fail:
 185     g_free(s->catalog_bitmap);
 186     return ret;
 187 }
 188
 189 static int64_t seek_to_sector(BlockDriverState *bs, int64_t sector_num)
 190 {
 191     BDRVBochsState *s = bs->opaque;
 192     uint64_t offset = sector_num * 512;
 193     uint64_t extent_index, extent_offset, bitmap_offset;
 194     char bitmap_entry;
 195     int ret;
 196
 197     // seek to sector
 198     extent_index = offset / s->extent_size;
 199     extent_offset = (offset % s->extent_size) / 512;
 200
 201     if (s->catalog_bitmap[extent_index] == 0xffffffff) {
 202         return 0; /* not allocated */
 203     }
 204
 205     bitmap_offset = s->data_offset +
 206         (512 * (uint64_t) s->catalog_bitmap[extent_index] *
 207         (s->extent_blocks + s->bitmap_blocks));
 208
 209     /* read in bitmap for current extent */
 210     ret = bdrv_pread(bs->file->bs, bitmap_offset + (extent_offset / 8),
 211                      &bitmap_entry, 1);
 212     if (ret < 0) {
 213         return ret;
 214     }
 215
 216     if (!((bitmap_entry >> (extent_offset % 8)) & 1)) {
 217         return 0; /* not allocated */
 218     }
 219
 220     return bitmap_offset + (512 * (s->bitmap_blocks + extent_offset));
 221 }
 222
 223 static int bochs_read(BlockDriverState *bs, int64_t sector_num,
 224                     uint8_t *buf, int nb_sectors)
 225 {
 226     int ret;
 227
 228     while (nb_sectors > 0) {
 229         int64_t block_offset = seek_to_sector(bs, sector_num);
 230         if (block_offset < 0) {
 231             return block_offset;
 232         } else if (block_offset > 0) {
 233             ret = bdrv_pread(bs->file->bs, block_offset, buf, 512);
 234             if (ret < 0) {
 235                 return ret;
 236             }
 237         } else {
 238             memset(buf, 0, 512);
 239         }
 240         nb_sectors--;
 241         sector_num++;
 242         buf += 512;
 243     }
 244     return 0;
 245 }
 246
 247 static coroutine_fn int bochs_co_read(BlockDriverState *bs, int64_t sector_num,
 248                                       uint8_t *buf, int nb_sectors)
 249 {
 250     int ret;
 251     BDRVBochsState *s = bs->opaque;
 252     qemu_co_mutex_lock(&s->lock);
 253     ret = bochs_read(bs, sector_num, buf, nb_sectors);
 254     qemu_co_mutex_unlock(&s->lock);
 255     return ret;
 256 }
 257
 258 static void bochs_close(BlockDriverState *bs)
 259 {
 260     BDRVBochsState *s = bs->opaque;
 261     g_free(s->catalog_bitmap);
 262 }
 263
 264 static BlockDriver bdrv_bochs = {
 265     .format_name        = "bochs",
 266     .instance_size      = sizeof(BDRVBochsState),
 267     .bdrv_probe         = bochs_probe,
 268     .bdrv_open          = bochs_open,
 269     .bdrv_read          = bochs_co_read,
 270     .bdrv_close         = bochs_close,
 271 };
 272
 273 static void bdrv_bochs_init(void)
 274 {
 275     bdrv_register(&bdrv_bochs);
 276 }
 277
 278 block_init(bdrv_bochs_init);