/* acorn.c - Read Linux/ADFS partition tables.  */
/*
 *  GRUB  --  GRand Unified Bootloader
 *  Copyright (C) 2005,2007  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 <https://www.gnu.org/licenses/>.
 */

#include <grub/disk.h>
#include <grub/misc.h>
#include <grub/mm.h>
#include <grub/partition.h>
#include <grub/acorn_filecore.h>

#define LINUX_NATIVE_MAGIC grub_cpu_to_le32(0xdeafa1de)
#define LINUX_SWAP_MAGIC grub_cpu_to_le32(0xdeafab1e)
#define LINUX_MAP_ENTRIES (512 / 12)

#define NONADFS_PARTITION_TYPE_LINUX 9
#define NONADFS_PARTITION_TYPE_MASK 15

struct grub_acorn_boot_block {
	grub_uint8_t misc[0x1C0];
	struct grub_filecore_disc_record disc_record;
	grub_uint8_t flags;
	grub_uint16_t start_cylinder;
	grub_uint8_t checksum;
} __attribute__((packed, aligned));

struct linux_part {
	grub_uint32_t magic;
	grub_uint32_t start;
	grub_uint32_t size;
};

struct grub_partition_map grub_acorn_partition_map;

static grub_err_t
acorn_partition_map_find(grub_disk_t disk, struct linux_part *m, grub_disk_addr_t *sector) {
	struct grub_acorn_boot_block boot;
	grub_err_t err;
	unsigned int checksum = 0;
	unsigned int heads;
	unsigned int sectors_per_cylinder;
	int i;

	err = grub_disk_read (disk, 0xC00 / GRUB_DISK_SECTOR_SIZE, 0, sizeof (struct grub_acorn_boot_block), &boot);
	if (err) {
		return err;
	}

	if ((boot.flags & NONADFS_PARTITION_TYPE_MASK) != NONADFS_PARTITION_TYPE_LINUX) {
		goto fail;
	}

	for (i = 0; i != 0x1ff; i++) {
		checksum = (checksum & 0xff) + (checksum >> 8) + boot.misc[i];
	}

	if ((grub_uint8_t)checksum != boot.checksum) {
		goto fail;
	}

	heads = (boot.disc_record.heads + ((boot.disc_record.lowsector >> 6) & 1));
	sectors_per_cylinder = boot.disc_record.secspertrack * heads;
	*sector = grub_le_to_cpu16 (boot.start_cylinder) * sectors_per_cylinder;

	return grub_disk_read (disk, *sector, 0, sizeof (struct linux_part) * LINUX_MAP_ENTRIES, m);

fail:
	return grub_error (GRUB_ERR_BAD_PART_TABLE,
		"Linux/ADFS partition map not found");
}

static grub_err_t
acorn_partition_map_iterate(grub_disk_t disk,
	int (*hook) (grub_disk_t disk,
		const grub_partition_t partition,
		void *closure),
	void *closure) {
	struct grub_partition part;
	struct linux_part map[LINUX_MAP_ENTRIES];
	int i;
	grub_disk_addr_t sector = 0;
	grub_err_t err;

	err = acorn_partition_map_find (disk, map, &sector);
	if (err) {
		return err;
	}

	part.partmap = &grub_acorn_partition_map;

	for (i = 0; i != LINUX_MAP_ENTRIES; i++) {
		if (map[i].magic != LINUX_NATIVE_MAGIC && map[i].magic != LINUX_SWAP_MAGIC) {
			return GRUB_ERR_NONE;
		}

		part.start = sector + map[i].start;
		part.len = map[i].size;
		part.offset = 6;
		part.number = part.index = i;

		if (hook (disk, &part, closure)) {
			return grub_errno;
		}
	}

	return GRUB_ERR_NONE;
}

/* Partition map type.  */
struct grub_partition_map grub_acorn_partition_map = {
	.name = "acorn",
	.iterate = acorn_partition_map_iterate,
};
