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/osdep.h"
  26#include "qapi/error.h"
  27#include "qemu-common.h"
  28#include "block/block_int.h"
  29#include "qemu/module.h"
  30
  31/**************************************************************/
  32
  33#define HEADER_MAGIC "Bochs Virtual HD Image"
  34#define HEADER_VERSION 0x00020000
  35#define HEADER_V1 0x00010000
  36#define HEADER_SIZE 512
  37
  38#define REDOLOG_TYPE "Redolog"
  39#define GROWING_TYPE "Growing"
  40
  41// not allocated: 0xffffffff
  42
  43// always little-endian
  44struct bochs_header {
  45    char magic[32];     /* "Bochs Virtual HD Image" */
  46    char type[16];      /* "Redolog" */
  47    char subtype[16];   /* "Undoable" / "Volatile" / "Growing" */
  48    uint32_t version;
  49    uint32_t header;    /* size of header */
  50
  51    uint32_t catalog;   /* num of entries */
  52    uint32_t bitmap;    /* bitmap size */
  53    uint32_t extent;    /* extent size */
  54
  55    union {
  56        struct {
  57            uint32_t reserved;  /* for ??? */
  58            uint64_t disk;      /* disk size */
  59            char padding[HEADER_SIZE - 64 - 20 - 12];
  60        } QEMU_PACKED redolog;
  61        struct {
  62            uint64_t disk;      /* disk size */
  63            char padding[HEADER_SIZE - 64 - 20 - 8];
  64        } QEMU_PACKED redolog_v1;
  65        char padding[HEADER_SIZE - 64 - 20];
  66    } extra;
  67} QEMU_PACKED;
  68
  69typedef struct BDRVBochsState {
  70    CoMutex lock;
  71    uint32_t *catalog_bitmap;
  72    uint32_t catalog_size;
  73
  74    uint32_t data_offset;
  75
  76    uint32_t bitmap_blocks;
  77    uint32_t extent_blocks;
  78    uint32_t extent_size;
  79} BDRVBochsState;
  80
  81static int bochs_probe(const uint8_t *buf, int buf_size, const char *filename)
  82{
  83    const struct bochs_header *bochs = (const void *)buf;
  84
  85    if (buf_size < HEADER_SIZE)
  86        return 0;
  87
  88    if (!strcmp(bochs->magic, HEADER_MAGIC) &&
  89        !strcmp(bochs->type, REDOLOG_TYPE) &&
  90        !strcmp(bochs->subtype, GROWING_TYPE) &&
  91        ((le32_to_cpu(bochs->version) == HEADER_VERSION) ||
  92        (le32_to_cpu(bochs->version) == HEADER_V1)))
  93        return 100;
  94
  95    return 0;
  96}
  97
  98static int bochs_open(BlockDriverState *bs, QDict *options, int flags,
  99                      Error **errp)
 100{
 101    BDRVBochsState *s = bs->opaque;
 102    uint32_t i;
 103    struct bochs_header bochs;
 104    int ret;
 105
 106    bs->read_only = 1; // no write support yet
 107
 108    ret = bdrv_pread(bs->file->bs, 0, &bochs, sizeof(bochs));
 109    if (ret < 0) {
 110        return ret;
 111    }
 112
 113    if (strcmp(bochs.magic, HEADER_MAGIC) ||
 114        strcmp(bochs.type, REDOLOG_TYPE) ||
 115        strcmp(bochs.subtype, GROWING_TYPE) ||
 116        ((le32_to_cpu(bochs.version) != HEADER_VERSION) &&
 117        (le32_to_cpu(bochs.version) != HEADER_V1))) {
 118        error_setg(errp, "Image not in Bochs format");
 119        return -EINVAL;
 120    }
 121
 122    if (le32_to_cpu(bochs.version) == HEADER_V1) {
 123        bs->total_sectors = le64_to_cpu(bochs.extra.redolog_v1.disk) / 512;
 124    } else {
 125        bs->total_sectors = le64_to_cpu(bochs.extra.redolog.disk) / 512;
 126    }
 127
 128    /* Limit to 1M entries to avoid unbounded allocation. This is what is
 129     * needed for the largest image that bximage can create (~8 TB). */
 130    s->catalog_size = le32_to_cpu(bochs.catalog);
 131    if (s->catalog_size > 0x100000) {
 132        error_setg(errp, "Catalog size is too large");
 133        return -EFBIG;
 134    }
 135
 136    s->catalog_bitmap = g_try_new(uint32_t, s->catalog_size);
 137    if (s->catalog_size && s->catalog_bitmap == NULL) {
 138        error_setg(errp, "Could not allocate memory for catalog");
 139        return -ENOMEM;
 140    }
 141
 142    ret = bdrv_pread(bs->file->bs, le32_to_cpu(bochs.header), s->catalog_bitmap,
 143                     s->catalog_size * 4);
 144    if (ret < 0) {
 145        goto fail;
 146    }
 147
 148    for (i = 0; i < s->catalog_size; i++)
 149        le32_to_cpus(&s->catalog_bitmap[i]);
 150
 151    s->data_offset = le32_to_cpu(bochs.header) + (s->catalog_size * 4);
 152
 153    s->bitmap_blocks = 1 + (le32_to_cpu(bochs.bitmap) - 1) / 512;
 154    s->extent_blocks = 1 + (le32_to_cpu(bochs.extent) - 1) / 512;
 155
 156    s->extent_size = le32_to_cpu(bochs.extent);
 157    if (s->extent_size < BDRV_SECTOR_SIZE) {
 158        /* bximage actually never creates extents smaller than 4k */
 159        error_setg(errp, "Extent size must be at least 512");
 160        ret = -EINVAL;
 161        goto fail;
 162    } else if (!is_power_of_2(s->extent_size)) {
 163        error_setg(errp, "Extent size %" PRIu32 " is not a power of two",
 164                   s->extent_size);
 165        ret = -EINVAL;
 166        goto fail;
 167    } else if (s->extent_size > 0x800000) {
 168        error_setg(errp, "Extent size %" PRIu32 " is too large",
 169                   s->extent_size);
 170        ret = -EINVAL;
 171        goto fail;
 172    }
 173
 174    if (s->catalog_size < DIV_ROUND_UP(bs->total_sectors,
 175                                       s->extent_size / BDRV_SECTOR_SIZE))
 176    {
 177        error_setg(errp, "Catalog size is too small for this disk size");
 178        ret = -EINVAL;
 179        goto fail;
 180    }
 181
 182    qemu_co_mutex_init(&s->lock);
 183    return 0;
 184
 185fail:
 186    g_free(s->catalog_bitmap);
 187    return ret;
 188}
 189
 190static int64_t seek_to_sector(BlockDriverState *bs, int64_t sector_num)
 191{
 192    BDRVBochsState *s = bs->opaque;
 193    uint64_t offset = sector_num * 512;
 194    uint64_t extent_index, extent_offset, bitmap_offset;
 195    char bitmap_entry;
 196    int ret;
 197
 198    // seek to sector
 199    extent_index = offset / s->extent_size;
 200    extent_offset = (offset % s->extent_size) / 512;
 201
 202    if (s->catalog_bitmap[extent_index] == 0xffffffff) {
 203        return 0; /* not allocated */
 204    }
 205
 206    bitmap_offset = s->data_offset +
 207        (512 * (uint64_t) s->catalog_bitmap[extent_index] *
 208        (s->extent_blocks + s->bitmap_blocks));
 209
 210    /* read in bitmap for current extent */
 211    ret = bdrv_pread(bs->file->bs, bitmap_offset + (extent_offset / 8),
 212                     &bitmap_entry, 1);
 213    if (ret < 0) {
 214        return ret;
 215    }
 216
 217    if (!((bitmap_entry >> (extent_offset % 8)) & 1)) {
 218        return 0; /* not allocated */
 219    }
 220
 221    return bitmap_offset + (512 * (s->bitmap_blocks + extent_offset));
 222}
 223
 224static int bochs_read(BlockDriverState *bs, int64_t sector_num,
 225                    uint8_t *buf, int nb_sectors)
 226{
 227    int ret;
 228
 229    while (nb_sectors > 0) {
 230        int64_t block_offset = seek_to_sector(bs, sector_num);
 231        if (block_offset < 0) {
 232            return block_offset;
 233        } else if (block_offset > 0) {
 234            ret = bdrv_pread(bs->file->bs, block_offset, buf, 512);
 235            if (ret < 0) {
 236                return ret;
 237            }
 238        } else {
 239            memset(buf, 0, 512);
 240        }
 241        nb_sectors--;
 242        sector_num++;
 243        buf += 512;
 244    }
 245    return 0;
 246}
 247
 248static coroutine_fn int bochs_co_read(BlockDriverState *bs, int64_t sector_num,
 249                                      uint8_t *buf, int nb_sectors)
 250{
 251    int ret;
 252    BDRVBochsState *s = bs->opaque;
 253    qemu_co_mutex_lock(&s->lock);
 254    ret = bochs_read(bs, sector_num, buf, nb_sectors);
 255    qemu_co_mutex_unlock(&s->lock);
 256    return ret;
 257}
 258
 259static void bochs_close(BlockDriverState *bs)
 260{
 261    BDRVBochsState *s = bs->opaque;
 262    g_free(s->catalog_bitmap);
 263}
 264
 265static BlockDriver bdrv_bochs = {
 266    .format_name        = "bochs",
 267    .instance_size      = sizeof(BDRVBochsState),
 268    .bdrv_probe         = bochs_probe,
 269    .bdrv_open          = bochs_open,
 270    .bdrv_read          = bochs_co_read,
 271    .bdrv_close         = bochs_close,
 272};
 273
 274static void bdrv_bochs_init(void)
 275{
 276    bdrv_register(&bdrv_bochs);
 277}
 278
 279block_init(bdrv_bochs_init);
 280