grub/grub-core/partmap/msdos.c

/* pc.c - Read PC style partition tables.  */
/*
 *  GRUB  --  GRand Unified Bootloader
 *  Copyright (C) 2002,2004,2005,2006,2007,2008,2009  Free Software Foundation, Inc.
 *
 *  GRUB is free software: you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation, either version 3 of the License, or
 *  (at your option) any later version.
 *
 *  GRUB is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with GRUB.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <grub/partition.h>
#include <grub/msdos_partition.h>
#include <grub/disk.h>
#include <grub/mm.h>
#include <grub/misc.h>
#include <grub/dl.h>
#include <grub/i18n.h>

GRUB_MOD_LICENSE ("GPLv3+");

static struct grub_partition_map grub_msdos_partition_map;


#ifdef GRUB_UTIL
#include <grub/emu/misc.h>

struct embed_signature
{
  const char *name;
  const char *signature;
  int signature_len;
  enum { TYPE_SOFTWARE, TYPE_RAID } type;
};

const char message_warn[][200] = {
  [TYPE_RAID] = N_("Sector %llu is already in use by raid controller `%s';"
		   " avoiding it.  "
		   "Please ask the manufacturer not to store data in MBR gap"),
  [TYPE_SOFTWARE] = N_("Sector %llu is already in use by the program `%s';"
		       " avoiding it.  "
		       "This software may cause boot or other problems in "
		       "future.  Please ask its authors not to store data "
		       "in the boot track") 
};


/* Signatures of other software that may be using sectors in the embedding
   area.  */
struct embed_signature embed_signatures[] =
  {
    {
      .name = "ZISD",
      .signature = "ZISD",
      .signature_len = 4,
      .type = TYPE_SOFTWARE
    },
    {
      .name = "FlexNet",
      .signature = "\xd4\x41\xa0\xf5\x03\x00\x03\x00",
      .signature_len = 8,
      .type = TYPE_SOFTWARE
    },
    {
      .name = "FlexNet",
      .signature = "\xd8\x41\xa0\xf5\x02\x00\x02\x00",
      .signature_len = 8,
      .type = TYPE_SOFTWARE
    },
    {
      /* from Ryan Perkins */
      .name = "HP Backup and Recovery Manager (?)",
      .signature = "\x70\x8a\x5d\x46\x35\xc5\x1b\x93"
		   "\xae\x3d\x86\xfd\xb1\x55\x3e\xe0",
      .signature_len = 16,
      .type = TYPE_SOFTWARE
    },
    {
      .name = "HighPoint RAID controller",
      .signature = "ycgl",
      .signature_len = 4,
      .type = TYPE_RAID
    }
  };
#endif

grub_err_t
grub_partition_msdos_iterate (grub_disk_t disk,
			      int (*hook) (grub_disk_t disk,
					   const grub_partition_t partition))
{
  struct grub_partition p;
  struct grub_msdos_partition_mbr mbr;
  int labeln = 0;
  grub_disk_addr_t lastaddr;
  grub_disk_addr_t ext_offset;
  grub_disk_addr_t delta = 0;

  if (disk->partition && disk->partition->partmap == &grub_msdos_partition_map)
    {
      if (disk->partition->msdostype == GRUB_PC_PARTITION_TYPE_LINUX_MINIX)
	delta = disk->partition->start;
      else
	return grub_error (GRUB_ERR_BAD_PART_TABLE, "no embedding supported");
    }

  p.offset = 0;
  ext_offset = 0;
  p.number = -1;
  p.partmap = &grub_msdos_partition_map;

  /* Any value different than `p.offset' will satisfy the check during
     first loop.  */
  lastaddr = !p.offset;

  while (1)
    {
      int i;
      struct grub_msdos_partition_entry *e;

      /* Read the MBR.  */
      if (grub_disk_read (disk, p.offset, 0, sizeof (mbr), &mbr))
	goto finish;

      /* This is our loop-detection algorithm. It works the following way:
	 It saves last position which was a power of two. Then it compares the
	 saved value with a current one. This way it's guaranteed that the loop
	 will be broken by at most third walk.
       */
      if (labeln && lastaddr == p.offset)
	return grub_error (GRUB_ERR_BAD_PART_TABLE, "loop detected");

      labeln++;
      if ((labeln & (labeln - 1)) == 0)
	lastaddr = p.offset;

      /* Check if it is valid.  */
      if (mbr.signature != grub_cpu_to_le16 (GRUB_PC_PARTITION_SIGNATURE))
	return grub_error (GRUB_ERR_BAD_PART_TABLE, "no signature");

      for (i = 0; i < 4; i++)
	if (mbr.entries[i].flag & 0x7f)
	  return grub_error (GRUB_ERR_BAD_PART_TABLE, "bad boot flag");

      /* Analyze DOS partitions.  */
      for (p.index = 0; p.index < 4; p.index++)
	{
	  e = mbr.entries + p.index;

	  p.start = p.offset
	    + (grub_le_to_cpu32 (e->start)
	       << (disk->log_sector_size - GRUB_DISK_SECTOR_BITS)) - delta;
	  p.len = grub_le_to_cpu32 (e->length)
	    << (disk->log_sector_size - GRUB_DISK_SECTOR_BITS);
	  p.msdostype = e->type;

	  grub_dprintf ("partition",
			"partition %d: flag 0x%x, type 0x%x, start 0x%llx, len 0x%llx\n",
			p.index, e->flag, e->type,
			(unsigned long long) p.start,
			(unsigned long long) p.len);

	  /* If this is a GPT partition, this MBR is just a dummy.  */
	  if (e->type == GRUB_PC_PARTITION_TYPE_GPT_DISK && p.index == 0)
	    return grub_error (GRUB_ERR_BAD_PART_TABLE, "dummy mbr");

	  /* If this partition is a normal one, call the hook.  */
	  if (! grub_msdos_partition_is_empty (e->type)
	      && ! grub_msdos_partition_is_extended (e->type))
	    {
	      p.number++;

	      if (hook (disk, &p))
		return grub_errno;
	    }
	  else if (p.number < 4)
	    /* If this partition is a logical one, shouldn't increase the
	       partition number.  */
	    p.number++;
	}

      /* Find an extended partition.  */
      for (i = 0; i < 4; i++)
	{
	  e = mbr.entries + i;

	  if (grub_msdos_partition_is_extended (e->type))
	    {
	      p.offset = ext_offset
		+ (grub_le_to_cpu32 (e->start)
		   << (disk->log_sector_size - GRUB_DISK_SECTOR_BITS));
	      if (! ext_offset)
		ext_offset = p.offset;

	      break;
	    }
	}

      /* If no extended partition, the end.  */
      if (i == 4)
	break;
    }

 finish:
  return grub_errno;
}

#ifdef GRUB_UTIL
static grub_err_t
pc_partition_map_embed (struct grub_disk *disk, unsigned int *nsectors,
			unsigned int max_nsectors,
			grub_embed_type_t embed_type,
			grub_disk_addr_t **sectors)
{
  grub_disk_addr_t end = ~0ULL;
  struct grub_msdos_partition_mbr mbr;
  int labeln = 0;
  /* Any value different than `p.offset' will satisfy the check during
     first loop.  */
  grub_disk_addr_t lastaddr = 1;
  grub_disk_addr_t ext_offset = 0;
  grub_disk_addr_t offset = 0;

  if (embed_type != GRUB_EMBED_PCBIOS)
    return grub_error (GRUB_ERR_NOT_IMPLEMENTED_YET,
		       "PC-style partitions curently support "
		       "only PC-BIOS embedding");

  if (disk->partition)
    return grub_error (GRUB_ERR_OUT_OF_RANGE,
		       "Embedding on MSDOS subpartition isn't supported");

  while (1)
    {
      int i;
      struct grub_msdos_partition_entry *e;
      grub_err_t err;

      /* Read the MBR.  */
      err = grub_disk_read (disk, offset, 0, sizeof (mbr), &mbr);
      if (err)
	return err;

      /* This is our loop-detection algorithm. It works the following way:
	 It saves last position which was a power of two. Then it compares the
	 saved value with a current one. This way it's guaranteed that the loop
	 will be broken by at most third walk.
       */
      if (labeln && lastaddr == offset)
	return grub_error (GRUB_ERR_BAD_PART_TABLE, "loop detected");

      labeln++;
      if ((labeln & (labeln - 1)) == 0)
	lastaddr = offset;

      /* Check if it is valid.  */
      if (mbr.signature != grub_cpu_to_le16 (GRUB_PC_PARTITION_SIGNATURE))
	return grub_error (GRUB_ERR_BAD_PART_TABLE, "no signature");

      for (i = 0; i < 4; i++)
	if (mbr.entries[i].flag & 0x7f)
	  return grub_error (GRUB_ERR_BAD_PART_TABLE, "bad boot flag");

      /* Analyze DOS partitions.  */
      for (i = 0; i < 4; i++)
	{
	  e = mbr.entries + i;

	  if (!grub_msdos_partition_is_empty (e->type)
	      && end > offset
	      + (grub_le_to_cpu32 (e->start)
		 << (disk->log_sector_size - GRUB_DISK_SECTOR_BITS)))
	    end = offset + (grub_le_to_cpu32 (e->start)
			    << (disk->log_sector_size - GRUB_DISK_SECTOR_BITS));

	  /* If this is a GPT partition, this MBR is just a dummy.  */
	  if (e->type == GRUB_PC_PARTITION_TYPE_GPT_DISK && i == 0)
	    return grub_error (GRUB_ERR_BAD_PART_TABLE, "dummy mbr");
	}

      /* Find an extended partition.  */
      for (i = 0; i < 4; i++)
	{
	  e = mbr.entries + i;

	  if (grub_msdos_partition_is_extended (e->type))
	    {
	      offset = ext_offset 
		+ (grub_le_to_cpu32 (e->start) 
		   << (disk->log_sector_size - GRUB_DISK_SECTOR_BITS));
	      if (! ext_offset)
		ext_offset = offset;

	      break;
	    }
	}

      /* If no extended partition, the end.  */
      if (i == 4)
	break;
    }

  if (end >= *nsectors + 2)
    {
      unsigned i, j;
      char *embed_signature_check;
      unsigned int orig_nsectors, avail_nsectors;

      orig_nsectors = *nsectors;
      *nsectors = end - 2;
      avail_nsectors = *nsectors;
      if (*nsectors > max_nsectors)
	*nsectors = max_nsectors;
      *sectors = grub_malloc (*nsectors * sizeof (**sectors));
      if (!*sectors)
	return grub_errno;
      for (i = 0; i < *nsectors; i++)
	(*sectors)[i] = 1 + i;

      /* Check for software that is already using parts of the embedding
       * area.
       */
      embed_signature_check = grub_malloc (GRUB_DISK_SECTOR_SIZE);
      for (i = 0; i < *nsectors; i++)
	{
	  if (grub_disk_read (disk, (*sectors)[i], 0, GRUB_DISK_SECTOR_SIZE,
			      embed_signature_check))
	    continue;

	  for (j = 0; j < ARRAY_SIZE (embed_signatures); j++)
	    if (! grub_memcmp (embed_signatures[j].signature,
			       embed_signature_check,
			       embed_signatures[j].signature_len))
	      break;
	  if (j == ARRAY_SIZE (embed_signatures))
	    continue;
	  grub_util_warn (_(message_warn[embed_signatures[j].type]),
			  (*sectors)[i], embed_signatures[j].name);
	  avail_nsectors--;
	  if (avail_nsectors < *nsectors)
	    *nsectors = avail_nsectors;

	  /* Avoid this sector.  */
	  for (j = i; j < *nsectors; j++)
	    (*sectors)[j]++;

	  /* Have we run out of space?  */
	  if (avail_nsectors < orig_nsectors)
	    break;

	  /* Make sure to check the next sector.  */
	  i--;
	}
      grub_free (embed_signature_check);

      if (*nsectors < orig_nsectors)
	return grub_error (GRUB_ERR_OUT_OF_RANGE,
			   N_("other software is using the embedding area, and "
			      "there is not enough room for core.img.  Such "
			      "software is often trying to store data in a way "
			      "that avoids detection.  We recommend you "
			      "investigate"));

      return GRUB_ERR_NONE;
    }

  if (end <= 1)
    return grub_error (GRUB_ERR_FILE_NOT_FOUND,
		       N_("this msdos-style partition label has no "
			  "post-MBR gap; embedding won't be possible"));

  if (*nsectors > 62)
    return grub_error (GRUB_ERR_OUT_OF_RANGE,
		       N_("your core.img is unusually large.  "
			  "It won't fit in the embedding area"));

  return grub_error (GRUB_ERR_OUT_OF_RANGE,
		     N_("your embedding area is unusually small.  "
			"core.img won't fit in it."));
}
#endif


/* Partition map type.  */
static struct grub_partition_map grub_msdos_partition_map =
  {
    .name = "msdos",
    .iterate = grub_partition_msdos_iterate,
#ifdef GRUB_UTIL
    .embed = pc_partition_map_embed
#endif
  };

GRUB_MOD_INIT(part_msdos)
{
  grub_partition_map_register (&grub_msdos_partition_map);
}

GRUB_MOD_FINI(part_msdos)
{
  grub_partition_map_unregister (&grub_msdos_partition_map);
}