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 #include "qemu/bswap.h"
  31 #include "qemu/error-report.h"
  32
  33 /**************************************************************/
  34
  35 #define HEADER_MAGIC "Bochs Virtual HD Image"
  36 #define HEADER_VERSION 0x00020000
  37 #define HEADER_V1 0x00010000
  38 #define HEADER_SIZE 512
  39
  40 #define REDOLOG_TYPE "Redolog"
  41 #define GROWING_TYPE "Growing"
  42
  43 // not allocated: 0xffffffff
  44
  45 // always little-endian
  46 struct bochs_header {
  47     char magic[32];     /* "Bochs Virtual HD Image" */
  48     char type[16];      /* "Redolog" */
  49     char subtype[16];   /* "Undoable" / "Volatile" / "Growing" */
  50     uint32_t version;
  51     uint32_t header;    /* size of header */
  52
  53     uint32_t catalog;   /* num of entries */
  54     uint32_t bitmap;    /* bitmap size */
  55     uint32_t extent;    /* extent size */
  56
  57     union {
  58         struct {
  59             uint32_t reserved;  /* for ??? */
  60             uint64_t disk;      /* disk size */
  61             char padding[HEADER_SIZE - 64 - 20 - 12];
  62         } QEMU_PACKED redolog;
  63         struct {
  64             uint64_t disk;      /* disk size */
  65             char padding[HEADER_SIZE - 64 - 20 - 8];
  66         } QEMU_PACKED redolog_v1;
  67         char padding[HEADER_SIZE - 64 - 20];
  68     } extra;
  69 } QEMU_PACKED;
  70
  71 typedef struct BDRVBochsState {
  72     CoMutex lock;
  73     uint32_t *catalog_bitmap;
  74     uint32_t catalog_size;
  75
  76     uint32_t data_offset;
  77
  78     uint32_t bitmap_blocks;
  79     uint32_t extent_blocks;
  80     uint32_t extent_size;
  81 } BDRVBochsState;
  82
  83 static int bochs_probe(const uint8_t *buf, int buf_size, const char *filename)
  84 {
  85     const struct bochs_header *bochs = (const void *)buf;
  86
  87     if (buf_size < HEADER_SIZE)
  88         return 0;
  89
  90     if (!strcmp(bochs->magic, HEADER_MAGIC) &&
  91         !strcmp(bochs->type, REDOLOG_TYPE) &&
  92         !strcmp(bochs->subtype, GROWING_TYPE) &&
  93         ((le32_to_cpu(bochs->version) == HEADER_VERSION) ||
  94         (le32_to_cpu(bochs->version) == HEADER_V1)))
  95         return 100;
  96
  97     return 0;
  98 }
  99
 100 static int bochs_open(BlockDriverState *bs, QDict *options, int flags,
 101                       Error **errp)
 102 {
 103     BDRVBochsState *s = bs->opaque;
 104     uint32_t i;
 105     struct bochs_header bochs;
 106     int ret;
 107
 108     /* No write support yet */
 109     ret = bdrv_apply_auto_read_only(bs, NULL, errp);
 110     if (ret < 0) {
 111         return ret;
 112     }
 113
 114     bs->file = bdrv_open_child(NULL, options, "file", bs, &child_file,
 115                                false, errp);
 116     if (!bs->file) {
 117         return -EINVAL;
 118     }
 119
 120     ret = bdrv_pread(bs->file, 0, &bochs, sizeof(bochs));
 121     if (ret < 0) {
 122         return ret;
 123     }
 124
 125     if (strcmp(bochs.magic, HEADER_MAGIC) ||
 126         strcmp(bochs.type, REDOLOG_TYPE) ||
 127         strcmp(bochs.subtype, GROWING_TYPE) ||
 128         ((le32_to_cpu(bochs.version) != HEADER_VERSION) &&
 129         (le32_to_cpu(bochs.version) != HEADER_V1))) {
 130         error_setg(errp, "Image not in Bochs format");
 131         return -EINVAL;
 132     }
 133
 134     if (le32_to_cpu(bochs.version) == HEADER_V1) {
 135         bs->total_sectors = le64_to_cpu(bochs.extra.redolog_v1.disk) / 512;
 136     } else {
 137         bs->total_sectors = le64_to_cpu(bochs.extra.redolog.disk) / 512;
 138     }
 139
 140     /* Limit to 1M entries to avoid unbounded allocation. This is what is
 141      * needed for the largest image that bximage can create (~8 TB). */
 142     s->catalog_size = le32_to_cpu(bochs.catalog);
 143     if (s->catalog_size > 0x100000) {
 144         error_setg(errp, "Catalog size is too large");
 145         return -EFBIG;
 146     }
 147
 148     s->catalog_bitmap = g_try_new(uint32_t, s->catalog_size);
 149     if (s->catalog_size && s->catalog_bitmap == NULL) {
 150         error_setg(errp, "Could not allocate memory for catalog");
 151         return -ENOMEM;
 152     }
 153
 154     ret = bdrv_pread(bs->file, le32_to_cpu(bochs.header), s->catalog_bitmap,
 155                      s->catalog_size * 4);
 156     if (ret < 0) {
 157         goto fail;
 158     }
 159
 160     for (i = 0; i < s->catalog_size; i++)
 161         le32_to_cpus(&s->catalog_bitmap[i]);
 162
 163     s->data_offset = le32_to_cpu(bochs.header) + (s->catalog_size * 4);
 164
 165     s->bitmap_blocks = 1 + (le32_to_cpu(bochs.bitmap) - 1) / 512;
 166     s->extent_blocks = 1 + (le32_to_cpu(bochs.extent) - 1) / 512;
 167
 168     s->extent_size = le32_to_cpu(bochs.extent);
 169     if (s->extent_size < BDRV_SECTOR_SIZE) {
 170         /* bximage actually never creates extents smaller than 4k */
 171         error_setg(errp, "Extent size must be at least 512");
 172         ret = -EINVAL;
 173         goto fail;
 174     } else if (!is_power_of_2(s->extent_size)) {
 175         error_setg(errp, "Extent size %" PRIu32 " is not a power of two",
 176                    s->extent_size);
 177         ret = -EINVAL;
 178         goto fail;
 179     } else if (s->extent_size > 0x800000) {
 180         error_setg(errp, "Extent size %" PRIu32 " is too large",
 181                    s->extent_size);
 182         ret = -EINVAL;
 183         goto fail;
 184     }
 185
 186     if (s->catalog_size < DIV_ROUND_UP(bs->total_sectors,
 187                                        s->extent_size / BDRV_SECTOR_SIZE))
 188     {
 189         error_setg(errp, "Catalog size is too small for this disk size");
 190         ret = -EINVAL;
 191         goto fail;
 192     }
 193
 194     qemu_co_mutex_init(&s->lock);
 195     return 0;
 196
 197 fail:
 198     g_free(s->catalog_bitmap);
 199     return ret;
 200 }
 201
 202 static void bochs_refresh_limits(BlockDriverState *bs, Error **errp)
 203 {
 204     bs->bl.request_alignment = BDRV_SECTOR_SIZE; /* No sub-sector I/O */
 205 }
 206
 207 static int64_t seek_to_sector(BlockDriverState *bs, int64_t sector_num)
 208 {
 209     BDRVBochsState *s = bs->opaque;
 210     uint64_t offset = sector_num * 512;
 211     uint64_t extent_index, extent_offset, bitmap_offset;
 212     char bitmap_entry;
 213     int ret;
 214
 215     // seek to sector
 216     extent_index = offset / s->extent_size;
 217     extent_offset = (offset % s->extent_size) / 512;
 218
 219     if (s->catalog_bitmap[extent_index] == 0xffffffff) {
 220         return 0; /* not allocated */
 221     }
 222
 223     bitmap_offset = s->data_offset +
 224         (512 * (uint64_t) s->catalog_bitmap[extent_index] *
 225         (s->extent_blocks + s->bitmap_blocks));
 226
 227     /* read in bitmap for current extent */
 228     ret = bdrv_pread(bs->file, bitmap_offset + (extent_offset / 8),
 229                      &bitmap_entry, 1);
 230     if (ret < 0) {
 231         return ret;
 232     }
 233
 234     if (!((bitmap_entry >> (extent_offset % 8)) & 1)) {
 235         return 0; /* not allocated */
 236     }
 237
 238     return bitmap_offset + (512 * (s->bitmap_blocks + extent_offset));
 239 }
 240
 241 static int coroutine_fn
 242 bochs_co_preadv(BlockDriverState *bs, uint64_t offset, uint64_t bytes,
 243                 QEMUIOVector *qiov, int flags)
 244 {
 245     BDRVBochsState *s = bs->opaque;
 246     uint64_t sector_num = offset >> BDRV_SECTOR_BITS;
 247     int nb_sectors = bytes >> BDRV_SECTOR_BITS;
 248     uint64_t bytes_done = 0;
 249     QEMUIOVector local_qiov;
 250     int ret;
 251
 252     assert((offset & (BDRV_SECTOR_SIZE - 1)) == 0);
 253     assert((bytes & (BDRV_SECTOR_SIZE - 1)) == 0);
 254
 255     qemu_iovec_init(&local_qiov, qiov->niov);
 256     qemu_co_mutex_lock(&s->lock);
 257
 258     while (nb_sectors > 0) {
 259         int64_t block_offset = seek_to_sector(bs, sector_num);
 260         if (block_offset < 0) {
 261             ret = block_offset;
 262             goto fail;
 263         }
 264
 265         qemu_iovec_reset(&local_qiov);
 266         qemu_iovec_concat(&local_qiov, qiov, bytes_done, 512);
 267
 268         if (block_offset > 0) {
 269             ret = bdrv_co_preadv(bs->file, block_offset, 512,
 270                                  &local_qiov, 0);
 271             if (ret < 0) {
 272                 goto fail;
 273             }
 274         } else {
 275             qemu_iovec_memset(&local_qiov, 0, 0, 512);
 276         }
 277         nb_sectors--;
 278         sector_num++;
 279         bytes_done += 512;
 280     }
 281
 282     ret = 0;
 283 fail:
 284     qemu_co_mutex_unlock(&s->lock);
 285     qemu_iovec_destroy(&local_qiov);
 286
 287     return ret;
 288 }
 289
 290 static void bochs_close(BlockDriverState *bs)
 291 {
 292     BDRVBochsState *s = bs->opaque;
 293     g_free(s->catalog_bitmap);
 294 }
 295
 296 static BlockDriver bdrv_bochs = {
 297     .format_name        = "bochs",
 298     .instance_size      = sizeof(BDRVBochsState),
 299     .bdrv_probe         = bochs_probe,
 300     .bdrv_open          = bochs_open,
 301     .bdrv_child_perm     = bdrv_format_default_perms,
 302     .bdrv_refresh_limits = bochs_refresh_limits,
 303     .bdrv_co_preadv = bochs_co_preadv,
 304     .bdrv_close         = bochs_close,
 305 };
 306
 307 static void bdrv_bochs_init(void)
 308 {
 309     bdrv_register(&bdrv_bochs);
 310 }
 311
 312 block_init(bdrv_bochs_init);