vpc.c

/*
 * vpc.c
 * Layered data source for Virtual PC hard disk images.
 *
 * Copyright (c) 2003 Christoph Pfisterer
 *
 * Permission is hereby granted, free of charge, to any person
 * obtaining a copy of this software and associated documentation
 * files (the "Software"), to deal in the Software without
 * restriction, including without limitation the rights to use, copy,
 * modify, merge, publish, distribute, sublicense, and/or sell copies
 * of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be
 * included in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE. 
 */

#include "global.h"

/*
 * types
 */

typedef struct vhd_chunk {
  int present;
  u8 off;
  u1 bitmap[1];
} VHD_CHUNK;

typedef struct vhd_source {
  SOURCE c;
  u8 off;
  u4 chunk_size;
  u4 chunk_count;
  u4 *raw_map;
  VHD_CHUNK **chunks;
} VHD_SOURCE;

/*
 * helper functions
 */

static SOURCE *init_vhd_source(SECTION *section, int level,
			       u8 total_size, u8 sparse_offset);
static int read_block_vhd(SOURCE *s, u8 pos, void *buf);
static void close_vhd(SOURCE *s);

/*
 * cd image detection
 */

void detect_vhd(SECTION *section, int level)
{
  unsigned char *buf;
  int found, type;
  u8 sparse_offset, total_size;
  char s[256];
  SOURCE *src;

  found = 0;

  /* check for info block at the beginning */
  if (get_buffer(section, 0, 511, (void **)&buf) < 511)
    return;
  if (memcmp(buf, "conectix", 8) == 0) {
    found = 1;
  }

  /* check for info block at the end if possible */
  if (!found && section->size > 1024 && !section->source->sequential) {
    if (get_buffer(section, section->size - 511, 511, (void **)&buf) < 511)
      return;
    if (memcmp(buf, "conectix", 8) == 0) {
      found = 1;
    }
  }

  if (!found)
    return;
  /* okay, now buf points to the info block, wherever it was found */

  type = get_be_long(buf + 0x3c);
  total_size = get_be_quad(buf + 0x28);  /* copy at 0x30 ... ??? */

  if (type == 2) {
    print_line(level, "Connectix Virtual PC hard disk image, fixed size");
  } else if (type == 3) {
    print_line(level, "Connectix Virtual PC hard disk image, dynamic size");
  } else if (type == 4) {
    print_line(level, "Connectix Virtual PC hard disk image, differential");
  } else {
    print_line(level, "Connectix Virtual PC hard disk image, unknown type %d",
	       type);
  }
  format_size_verbose(s, total_size);
  print_line(level + 1, "Disk size %s", s);

  if (type == 3) {
    /* dynamically sized, set up a mapping data source */
    sparse_offset = get_be_quad(buf + 16);

    src = init_vhd_source(section, level, total_size, sparse_offset);

    if (src != NULL) {
      /* analyze it */
      analyze_source(src, level);
      close_source(src);
    }
  }

  if (type == 3 || type == 4)
    stop_detect();
}

/*
 * initialize the mapping source
 */

static SOURCE *init_vhd_source(SECTION *section, int level,
			       u8 total_size, u8 sparse_offset)
{
  VHD_SOURCE *vs;
  unsigned char *buf;
  u8 map_offset;
  u4 map_size;
  char s[256];

  /* allocate and init source structure */
  vs = (VHD_SOURCE *)malloc(sizeof(VHD_SOURCE));
  if (vs == NULL)
    bailout("Out of memory");
  memset(vs, 0, sizeof(VHD_SOURCE));

  vs->c.size_known = 1;
  vs->c.size = total_size;
  vs->c.blocksize = 512;
  vs->c.foundation = section->source;
  vs->c.read_block = read_block_vhd;
  vs->c.close = close_vhd;
  vs->off = section->pos;

  /* read sparse information block */
  if (get_buffer(section, sparse_offset, 512, (void **)&buf) < 512) {
    print_line(level + 1, "Error reading the sparse image info block");
    goto errorexit;
  }
  map_offset = get_be_quad(buf + 16);
  vs->chunk_count = get_be_long(buf + 28);
  vs->chunk_size = get_be_long(buf + 32);

  format_size(s, vs->chunk_size);
  print_line(level + 1, "Dynamic sizing uses %lu chunks of %s",
	     vs->chunk_count, s);

  if ((u8)vs->chunk_count * vs->chunk_size < total_size) {
    print_line(level + 1, "Error: Sparse parameters don't match total size");
    goto errorexit;
  }
  if (vs->chunk_size < 4096) {
    print_line(level + 1, "Error: Sparse chunk size too small (%lu bytes)",
	       vs->chunk_size);
    goto errorexit;
  }
  if (vs->chunk_size > 2*1024*1024) {
    /* written-to bitmap wouldn't fit in one sector */
    print_line(level + 1, "Error: Sparse chunk size too large (%lu bytes)",
	       vs->chunk_size);
    goto errorexit;
  }

  /* allocate further data structures */
  map_size = vs->chunk_count * 4;
  vs->raw_map = (u4 *)malloc(map_size);
  if (vs->raw_map == NULL)
    bailout("Out of memory");
  vs->chunks = (VHD_CHUNK **)malloc(vs->chunk_count * sizeof(VHD_CHUNK *));
  if (vs->chunks == NULL)
    bailout("Out of memory");
  memset(vs->chunks, 0, vs->chunk_count * sizeof(VHD_CHUNK *));

  /* read the chunk map */
  if (get_buffer_real(section->source, vs->off + map_offset, map_size,
		      (void *)vs->raw_map, NULL) < map_size) {
    print_line(level + 1, "Error reading the sparse image map");
    goto errorexit;
  }

  return (SOURCE *)vs;

errorexit:
  close_vhd((SOURCE *)vs);
  free(vs);
  return NULL;
}

/*
 * mapping read
 */

static int read_block_vhd(SOURCE *s, u8 pos, void *buf)
{
  VHD_SOURCE *vs = (VHD_SOURCE *)s;
  SOURCE *fs = s->foundation;
  u4 chunk, chunk_start_sector, sector;
  u8 chunk_disk_off, sector_pos;
  unsigned char *filebuf;
  int present;

  chunk = (u4)(pos / vs->chunk_size);
  if (chunk >= vs->chunk_count)
    return 0;

  if (vs->chunks[chunk] == NULL) {
    /* create data structure for the chunk */

    chunk_start_sector = get_be_long(vs->raw_map + chunk);
    /* NOTE: raw_map is a u4*, so C does the arithmetics for us */

    if (chunk_start_sector == 0xffffffff) {
      present = 0;
    } else {
      chunk_disk_off = vs->off + (u8)chunk_start_sector * 512;
      if (get_buffer_real(fs, chunk_disk_off, 512,
			  NULL, (void **)&filebuf) < 512)
	present = 0;
      else
	present = 1;
    }

    if (!present) {
      vs->chunks[chunk] = (VHD_CHUNK *)malloc(sizeof(VHD_CHUNK));
      if (vs->chunks[chunk] == NULL)
	bailout("Out of memory");
      vs->chunks[chunk]->present = 0;
    } else {
      vs->chunks[chunk] = (VHD_CHUNK *)malloc(sizeof(VHD_CHUNK) + 512);
      if (vs->chunks[chunk] == NULL)
	bailout("Out of memory");
      vs->chunks[chunk]->present = 1;
      vs->chunks[chunk]->off = chunk_disk_off + 512;
      memcpy(vs->chunks[chunk]->bitmap, filebuf, 512);
    }
  }

  if (!vs->chunks[chunk]->present) {
    /* whole chunk is missing */
    memset(buf, 0, 512);
    return 1;
  }

  sector = (u4)((pos - (u8)chunk * vs->chunk_size) / 512);
  if (vs->chunks[chunk]->bitmap[sector >> 3] & (128 >> (sector & 7))) {
    /* sector is present and in use */
    sector_pos = vs->chunks[chunk]->off + (u8)sector * 512;
    if (get_buffer_real(fs, sector_pos, 512, buf, NULL) < 512)
      return 0;
  } else {
    /* sector has not been written to (although it's present on disk) */
    memset(buf, 0, 512);
  }
  return 1;
}

/*
 * cleanup
 */

static void close_vhd(SOURCE *s)
{
  VHD_SOURCE *vs = (VHD_SOURCE *)s;
  u4 chunk;

  /* free raw chunk map */
  if (vs->raw_map != NULL)
    free(vs->raw_map);

  /* free chunk info data */
  if (vs->chunks != NULL) {
    for (chunk = 0; chunk < vs->chunk_count; chunk++) {
      if (vs->chunks[chunk] != NULL)
	free(vs->chunks[chunk]);
    }
    free(vs->chunks);
  }
}

/* EOF */