ntfs.c

在Linux2.6内核下的udev文件系统的源码

/*
 * volume_id - reads filesystem label and uuid
 *
 * Copyright (C) 2004 Kay Sievers <[e-mail]>
 *
 *	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 version 2 of the License.
 */

#ifndef _GNU_SOURCE
#define _GNU_SOURCE 1
#endif

#ifdef HAVE_CONFIG_H
#  include <config.h>
#endif

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>
#include <ctype.h>

#include "libvolume_id.h"
#include "util.h"

static struct ntfs_super_block {
	uint8_t		jump[3];
	uint8_t		oem_id[8];
	uint16_t	bytes_per_sector;
	uint8_t		sectors_per_cluster;
	uint16_t	reserved_sectors;
	uint8_t		fats;
	uint16_t	root_entries;
	uint16_t	sectors;
	uint8_t		media_type;
	uint16_t	sectors_per_fat;
	uint16_t	sectors_per_track;
	uint16_t	heads;
	uint32_t	hidden_sectors;
	uint32_t	large_sectors;
	uint16_t	unused[2];
	uint64_t	number_of_sectors;
	uint64_t	mft_cluster_location;
	uint64_t	mft_mirror_cluster_location;
	int8_t		cluster_per_mft_record;
	uint8_t		reserved1[3];
	int8_t		cluster_per_index_record;
	uint8_t		reserved2[3];
	uint8_t		volume_serial[8];
	uint16_t	checksum;
} PACKED *ns;

static struct master_file_table_record {
	uint8_t		magic[4];
	uint16_t	usa_ofs;
	uint16_t	usa_count;
	uint64_t	lsn;
	uint16_t	sequence_number;
	uint16_t	link_count;
	uint16_t	attrs_offset;
	uint16_t	flags;
	uint32_t	bytes_in_use;
	uint32_t	bytes_allocated;
} PACKED *mftr;

static struct file_attribute {
	uint32_t	type;
	uint32_t	len;
	uint8_t		non_resident;
	uint8_t		name_len;
	uint16_t	name_offset;
	uint16_t	flags;
	uint16_t	instance;
	uint32_t	value_len;
	uint16_t	value_offset;
} PACKED *attr;

static struct volume_info {
	uint64_t	reserved;
	uint8_t		major_ver;
	uint8_t		minor_ver;
} PACKED *info;

#define MFT_RECORD_VOLUME			3
#define MFT_RECORD_ATTR_VOLUME_NAME		0x60
#define MFT_RECORD_ATTR_VOLUME_INFO		0x70
#define MFT_RECORD_ATTR_OBJECT_ID		0x40
#define MFT_RECORD_ATTR_END			0xffffffffu

int volume_id_probe_ntfs(struct volume_id *id, uint64_t off, uint64_t size)
{
	unsigned int sector_size;
	unsigned int cluster_size;
	uint64_t mft_cluster;
	uint64_t mft_off;
	unsigned int mft_record_size;
	unsigned int attr_type;
	unsigned int attr_off;
	unsigned int attr_len;
	unsigned int val_off;
	unsigned int val_len;
	const uint8_t *buf;
	const uint8_t *val;

	info("probing at offset 0x%llx", (unsigned long long) off);

	ns = (struct ntfs_super_block *) volume_id_get_buffer(id, off, 0x200);
	if (ns == NULL)
		return -1;

	if (memcmp(ns->oem_id, "NTFS", 4) != 0)
		return -1;

	volume_id_set_uuid(id, ns->volume_serial, 0, UUID_64BIT_LE);

	sector_size = le16_to_cpu(ns->bytes_per_sector);
	cluster_size = ns->sectors_per_cluster * sector_size;
	mft_cluster = le64_to_cpu(ns->mft_cluster_location);
	mft_off = mft_cluster * cluster_size;

	if (ns->cluster_per_mft_record < 0)
		/* size = -log2(mft_record_size); normally 1024 Bytes */
		mft_record_size = 1 << -ns->cluster_per_mft_record;
	else
		mft_record_size = ns->cluster_per_mft_record * cluster_size;

	dbg("sectorsize  0x%x", sector_size);
	dbg("clustersize 0x%x", cluster_size);
	dbg("mftcluster  %llu", (unsigned long long) mft_cluster);
	dbg("mftoffset  0x%llx", (unsigned long long) mft_off);
	dbg("cluster per mft_record  %i", ns->cluster_per_mft_record);
	dbg("mft record size  %i", mft_record_size);

	buf = volume_id_get_buffer(id, off + mft_off + (MFT_RECORD_VOLUME * mft_record_size),
			 mft_record_size);
	if (buf == NULL)
		goto found;

	mftr = (struct master_file_table_record*) buf;

	dbg("mftr->magic '%c%c%c%c'", mftr->magic[0], mftr->magic[1], mftr->magic[2], mftr->magic[3]);
	if (memcmp(mftr->magic, "FILE", 4) != 0)
		goto found;

	attr_off = le16_to_cpu(mftr->attrs_offset);
	dbg("file $Volume's attributes are at offset %i", attr_off);

	while (1) {
		attr = (struct file_attribute*) &buf[attr_off];
		attr_type = le32_to_cpu(attr->type);
		attr_len = le16_to_cpu(attr->len);
		val_off = le16_to_cpu(attr->value_offset);
		val_len = le32_to_cpu(attr->value_len);
		attr_off += attr_len;

		if (attr_len == 0)
			break;

		if (attr_off >= mft_record_size)
			break;

		if (attr_type == MFT_RECORD_ATTR_END)
			break;

		dbg("found attribute type 0x%x, len %i, at offset %i",
		    attr_type, attr_len, attr_off);

		if (attr_type == MFT_RECORD_ATTR_VOLUME_INFO) {
			dbg("found info, len %i", val_len);
			info = (struct volume_info*) (((uint8_t *) attr) + val_off);
			snprintf(id->type_version, sizeof(id->type_version)-1,
				 "%u.%u", info->major_ver, info->minor_ver);
		}

		if (attr_type == MFT_RECORD_ATTR_VOLUME_NAME) {
			dbg("found label, len %i", val_len);
			if (val_len > VOLUME_ID_LABEL_SIZE)
				val_len = VOLUME_ID_LABEL_SIZE;

			val = ((uint8_t *) attr) + val_off;
			volume_id_set_label_raw(id, val, val_len);
			volume_id_set_label_unicode16(id, val, LE, val_len);
		}
	}

found:
	volume_id_set_usage(id, VOLUME_ID_FILESYSTEM);
	id->type = "ntfs";

	return 0;
}