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