genode/repos/os/src/server/part_blk/mbr.h

/*
 * \brief  MBR partition table definitions
 * \author Sebastian Sumpf
 * \author Stefan Kalkowski
 * \author Josef Soentgen
 * \date   2013-12-04
 */

/*
 * Copyright (C) 2013-2014 Genode Labs GmbH
 *
 * This file is part of the Genode OS framework, which is distributed
 * under the terms of the GNU General Public License version 2.
 */

#ifndef _PART_BLK__MBR_H_
#define _PART_BLK__MBR_H_

#include <base/env.h>
#include <base/printf.h>
#include <block_session/client.h>

#include "driver.h"
#include "partition_table.h"


struct Mbr_partition_table : public Block::Partition_table
{
	public:

		class Protective_mbr_found { };

	private:

		typedef Block::Partition_table::Sector Sector;

		/**
		 * Partition table entry format
		 */
		struct Partition_record
		{
			enum { INVALID = 0, EXTENTED = 0x5, PROTECTIVE = 0xee, };
			Genode::uint8_t  _unused[4];
			Genode::uint8_t  _type;       /* partition type */
			Genode::uint8_t  _unused2[3];
			Genode::uint32_t _lba;        /* logical block address */
			Genode::uint32_t _sectors;    /* number of sectors */

			bool is_valid()      { return _type != INVALID; }
			bool is_extented()   { return _type == EXTENTED; }
			bool is_protective() { return _type == PROTECTIVE; }
		} __attribute__((packed));


		/**
		 * Master/Extented boot record format
		 */
		struct Mbr
		{
			Genode::uint8_t  _unused[446];
			Partition_record _records[4];
			Genode::uint16_t _magic;

			bool is_valid()
			{
				/* magic number of partition table */
				enum { MAGIC = 0xaa55 };
				return _magic == MAGIC;
			}
		} __attribute__((packed));


		enum { MAX_PARTITIONS = 32 };

		Block::Partition *_part_list[MAX_PARTITIONS]; /* contains pointers to valid
		                                          partitions or 0 */

		void _parse_extented(Partition_record *record)
		{
			Partition_record *r = record;
			unsigned lba = r->_lba;

			/* first logical partition number */
			int nr = 5;
			do {
				Sector s(lba, 1);
				Mbr *ebr = s.addr<Mbr *>();

				if (!(ebr->is_valid()))
					return;

			/* The first record is the actual logical partition. The lba of this
			 * partition is relative to the lba of the current EBR */
			Partition_record *logical = &(ebr->_records[0]);
			if (logical->is_valid() && nr < MAX_PARTITIONS) {
				_part_list[nr++] = new (Genode::env()->heap())
					Block::Partition(logical->_lba + lba, logical->_sectors);

				PINF("Partition %d: LBA %u (%u blocks) type %x", nr - 1,
				     logical->_lba + lba, logical->_sectors, logical->_type);
			}

			/*
			 * the second record points to the next EBR
			 * (relative form this EBR)
			 */
			r = &(ebr->_records[1]);
			lba += ebr->_records[1]._lba;

			} while (r->is_valid());
		}

		void _parse_mbr(Mbr *mbr)
		{
			/* no partition table, use whole disc as partition 0 */
			if (!(mbr->is_valid()))
				_part_list[0] = new(Genode::env()->heap())
					Block::Partition(0, Block::Driver::driver().blk_cnt() - 1);

			for (int i = 0; i < 4; i++) {
				Partition_record *r = &(mbr->_records[i]);

				if (!r->is_valid())
					continue;

				PINF("Partition %d: LBA %u (%u blocks) type: %x",
				     i + 1, r->_lba, r->_sectors, r->_type);

				if (r->is_protective())
					throw Protective_mbr_found();

				if (r->is_extented()) {
					_parse_extented(r);
					continue;
				}

				_part_list[i + 1] = new(Genode::env()->heap())
					Block::Partition(r->_lba, r->_sectors);
			}
		}

		Mbr_partition_table()
		{
			Sector s(0, 1);
			_parse_mbr(s.addr<Mbr *>());

			/*
			 * we read all partition information,
			 * now it's safe to turn in asynchronous mode
			 */
			Block::Driver::driver().work_asynchronously();
		}

	public:

		Block::Partition *partition(int num) {
			return (num < MAX_PARTITIONS) ? _part_list[num] : 0; }

		bool avail()
		{
			for (unsigned num = 0; num < MAX_PARTITIONS; num++)
				if (_part_list[num])
					return true;
			return false;
		}

		static Mbr_partition_table& table()
		{
			static Mbr_partition_table table;
			return table;
		}
};

#endif /* _PART_BLK__MBR_H_ */