barebox/common/partitions/dos.c

/*
 * Copyright (C) 2009...2011 Juergen Beisert, Pengutronix
 *
 * This program 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 2 of
 * the License, or (at your option) any later version.
 *
 * This program 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.
 */

#include <common.h>
#include <disks.h>
#include <init.h>
#include <asm/unaligned.h>
#include <dma.h>
#include <linux/err.h>

#include "parser.h"

/**
 * Guess the size of the disk, based on the partition table entries
 * @param dev device to create partitions for
 * @param table partition table
 * @return sector count
 */
static uint64_t disk_guess_size(struct device_d *dev,
		struct partition_entry *table)
{
	uint64_t size = 0;
	int i;

	for (i = 0; i < 4; i++) {
		if (get_unaligned_le32(&table[i].partition_start) != 0) {
			uint64_t part_end = get_unaligned_le32(&table[i].partition_start) +
				get_unaligned_le32(&table[i].partition_size);

			if (size < part_end)
				size = part_end;
		}
	}

	return size;
}

static void *read_mbr(struct block_device *blk)
{
	void *buf = dma_alloc(SECTOR_SIZE);
	int ret;

	ret = block_read(blk, buf, 0, 1);
	if (ret) {
		free(buf);
		return NULL;
	}

	return buf;
}

static int write_mbr(struct block_device *blk, void *buf)
{
	int ret;

	ret = block_write(blk, buf, 0, 1);
	if (ret)
		return ret;

	return block_flush(blk);
}

struct disk_signature_priv {
	uint32_t signature;
	struct block_device *blk;
};

static int dos_set_disk_signature(struct param_d *p, void *_priv)
{
	struct disk_signature_priv *priv = _priv;
	struct block_device *blk = priv->blk;
	void *buf;
	__le32 *disksigp;
	int ret;

	buf = read_mbr(blk);
	if (!buf)
		return -EIO;

	disksigp = buf + 0x1b8;

	*disksigp = cpu_to_le32(priv->signature);

	ret = write_mbr(blk, buf);

	free(buf);

	return ret;
}

static int dos_get_disk_signature(struct param_d *p, void *_priv)
{
	struct disk_signature_priv *priv = _priv;
	struct block_device *blk = priv->blk;
	void *buf;

	buf = read_mbr(blk);
	if (!buf)
		return -EIO;

	priv->signature = get_unaligned_le32(buf + 0x1b8);

	free(buf);

	return 0;
}

static void dos_extended_partition(struct block_device *blk, struct partition_desc *pd,
		struct partition *partition)
{
	uint8_t *buf = dma_alloc(SECTOR_SIZE);
	uint32_t ebr_sector = partition->first_sec;
	struct partition_entry *table = (struct partition_entry *)&buf[0x1be];

	while (pd->used_entries < ARRAY_SIZE(pd->parts)) {
		int rc, i;
		int n = pd->used_entries;

		dev_dbg(blk->dev, "expect EBR in sector %x\n", ebr_sector);

		rc = block_read(blk, buf, ebr_sector, 1);
		if (rc != 0) {
			dev_err(blk->dev, "Cannot read EBR partition table\n");
			goto out;
		}

		/* sanity checks */
		if (buf[0x1fe] != 0x55 || buf[0x1ff] != 0xaa) {
			dev_err(blk->dev, "sector %x doesn't contain an EBR signature\n", ebr_sector);
			goto out;
		}

		for (i = 0x1de; i < 0x1fe; ++i)
			if (buf[i]) {
				dev_err(blk->dev, "EBR's third or fourth partition non-empty\n");
				goto out;
			}
		/* /sanity checks */

		/* the first entry defines the extended partition */
		pd->parts[n].first_sec = ebr_sector +
			get_unaligned_le32(&table[0].partition_start);
		pd->parts[n].size = get_unaligned_le32(&table[0].partition_size);
		pd->parts[n].dos_partition_type = table[0].type;
		pd->used_entries++;

		/* the second entry defines the start of the next ebr if != 0 */
		if (get_unaligned_le32(&table[1].partition_start))
			ebr_sector = partition->first_sec +
				get_unaligned_le32(&table[1].partition_start);
		else
			break;
	}

out:
	dma_free(buf);
	return;
}

/**
 * Check if a DOS like partition describes this block device
 * @param blk Block device to register to
 * @param pd Where to store the partition information
 *
 * It seems at least on ARM this routine cannot use temp. stack space for the
 * sector. So, keep the malloc/free.
 */
static void dos_partition(void *buf, struct block_device *blk,
			  struct partition_desc *pd)
{
	struct partition_entry *table;
	struct partition pentry;
	struct partition *extended_partition = NULL;
	uint8_t *buffer = buf;
	int i;
	struct disk_signature_priv *dsp;

	table = (struct partition_entry *)&buffer[446];

	/* valid for x86 BIOS based disks only */
	if (IS_ENABLED(CONFIG_DISK_BIOS) && blk->num_blocks == 0)
		blk->num_blocks = disk_guess_size(blk->dev, table);

	for (i = 0; i < 4; i++) {
		pentry.first_sec = get_unaligned_le32(&table[i].partition_start);
		pentry.size = get_unaligned_le32(&table[i].partition_size);
		pentry.dos_partition_type = table[i].type;

		if (pentry.first_sec != 0) {
			int n = pd->used_entries;
			pd->parts[n].first_sec = pentry.first_sec;
			pd->parts[n].size = pentry.size;
			pd->parts[n].dos_partition_type = pentry.dos_partition_type;
			pd->used_entries++;
			/*
			 * Partitions of type 0x05 and 0x0f (and some more)
			 * contain extended partitions. Only check for type 0x0f
			 * here as this is the easiest to parse and common
			 * enough.
			 */
			if (pentry.dos_partition_type == 0x0f) {
				if (!extended_partition)
					extended_partition = &pd->parts[n];
				else
					/*
					 * An DOS MBR must only contain a single
					 * extended partition. Just ignore all
					 * but the first.
					 */
					dev_warn(blk->dev, "Skipping additional extended partition\n");
			}

		} else {
			dev_dbg(blk->dev, "Skipping empty partition %d\n", i);
		}
	}

	if (extended_partition)
		dos_extended_partition(blk, pd, extended_partition);

	dsp = xzalloc(sizeof(*dsp));
	dsp->blk = blk;

	/*
	 * This parameter contains the NT disk signature. This allows to
	 * to specify the Linux rootfs using the following syntax:
	 *
	 *   root=PARTUUID=ssssssss-pp
	 *
	 * where ssssssss is a zero-filled hex representation of the 32-bit
	 * signature and pp is a zero-filled hex representation of the 1-based
	 * partition number.
	 */
	dev_add_param_int(blk->dev, "nt_signature",
			dos_set_disk_signature, dos_get_disk_signature,
			&dsp->signature, "%08x", dsp);
}

static struct partition_parser dos = {
	.parse = dos_partition,
	.type = filetype_mbr,
};

static int dos_partition_init(void)
{
	return partition_parser_register(&dos);
}
postconsole_initcall(dos_partition_init);