/* 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/types.h>
#include <grub/msdos_partition.h>
#include <grub/disk.h>
#include <grub/mm.h>
#include <grub/misc.h>

GRUB_MOD_LICENSE("GPLv3+");

static struct grub_partition_map grub_msdos_partition_map;

grub_err_t
grub_partition_msdos_iterate(grub_disk_t disk,
	grub_partition_iterate_hook_t hook,
	void* hook_data)
{
	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;

		/* If this is a GPT partition, this MBR is just a dummy.  */
		if (p.offset == 0)
			for (i = 0; i < 4; i++)
				if (mbr.entries[i].type == GRUB_PC_PARTITION_TYPE_GPT_DISK)
					return grub_error(GRUB_ERR_BAD_PART_TABLE, "dummy mbr");

		/* 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_compile_time(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_disk_addr_t)grub_le_to_cpu32(e->start)
					<< (disk->log_sector_size - GRUB_DISK_SECTOR_BITS)) - delta;
			p.len = (grub_uint64_t)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 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, hook_data))
					return grub_errno;
			}
			else if (p.number < 3)
				/* 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_disk_addr_t)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;
}

/* Partition map type.  */
static struct grub_partition_map grub_msdos_partition_map =
{
	.name = "msdos",
	.iterate = grub_partition_msdos_iterate,
};

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);
}
