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