mirror of
https://git.code.sf.net/p/ntfs-3g/ntfs-3g.git
synced 2024-11-27 20:14:10 +08:00
253 lines
8.5 KiB
C
253 lines
8.5 KiB
C
/*
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* bootsect.c - Boot sector handling code. Part of the Linux-NTFS project.
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*
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* Copyright (c) 2000-2004 Anton Altaparmakov
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*
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* This program/include file is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as published
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* by the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program/include file is distributed in the hope that it will be
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* useful, but WITHOUT ANY WARRANTY; without even the implied warranty
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* of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program (in the main directory of the Linux-NTFS
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* distribution in the file COPYING); if not, write to the Free Software
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* Foundation,Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*/
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#include "config.h"
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <errno.h>
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#include "compat.h"
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#include "bootsect.h"
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#include "debug.h"
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/**
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* ntfs_boot_sector_is_ntfs - check if buffer contains a valid ntfs boot sector
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* @b: buffer containing putative boot sector to analyze
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* @silent: if zero, output progress messages to stderr
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*
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* Check if the buffer @b contains a valid ntfs boot sector. The buffer @b
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* must be at least 512 bytes in size.
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*
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* If @silent is zero, output progress messages to stderr. Otherwise, do not
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* output any messages (except when configured with --enable-debug in which
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* case warning/debug messages may be displayed).
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*
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* Return TRUE if @b contains a valid ntfs boot sector and FALSE if not.
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*/
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BOOL ntfs_boot_sector_is_ntfs(NTFS_BOOT_SECTOR *b, const BOOL silent)
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{
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u32 i;
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Sprintf(silent, "\nBeginning bootsector check...\n");
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/* Calculate the checksum. Note, this is just a simple addition of
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all u32 values in the bootsector starting at the beginning and
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finishing at the offset of the checksum itself (i.e. not including
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the checksum...). */
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if ((void*)b < (void*)&b->checksum) {
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u32 *u = (u32 *)b;
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u32 *bi = (u32 *)(&b->checksum);
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Sprintf(silent, "Calculating bootsector checksum... ");
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for (i = 0; u < bi; ++u)
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i += le32_to_cpup(u);
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if (le32_to_cpu(b->checksum) && le32_to_cpu(b->checksum) != i)
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goto not_ntfs;
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Sprintf(silent, "OK\n");
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}
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/* Check OEMidentifier is "NTFS " */
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Sprintf(silent, "Checking OEMid... ");
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if (b->oem_id != cpu_to_le64(0x202020205346544eULL)) /* "NTFS " */
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goto not_ntfs;
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Sprintf(silent, "OK\n");
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/* Check bytes per sector value is between 256 and 4096. */
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Sprintf(silent, "Checking bytes per sector... ");
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if (le16_to_cpu(b->bpb.bytes_per_sector) < 0x100 ||
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le16_to_cpu(b->bpb.bytes_per_sector) > 0x1000)
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goto not_ntfs;
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Sprintf(silent, "OK\n");
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/* Check sectors per cluster value is valid. */
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Sprintf(silent, "Checking sectors per cluster... ");
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switch (b->bpb.sectors_per_cluster) {
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case 1: case 2: case 4: case 8: case 16:
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case 32: case 64: case 128:
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break;
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default:
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goto not_ntfs;
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}
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Sprintf(silent, "OK\n");
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/* Check the cluster size is not above 65536 bytes. */
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Sprintf(silent, "Checking cluster size... ");
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if ((u32)le16_to_cpu(b->bpb.bytes_per_sector) *
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b->bpb.sectors_per_cluster > 0x10000)
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goto not_ntfs;
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Sprintf(silent, "OK\n");
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/* Check reserved/unused fields are really zero. */
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Sprintf(silent, "Checking reserved fields are zero... ");
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if (le16_to_cpu(b->bpb.reserved_sectors) ||
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le16_to_cpu(b->bpb.root_entries) ||
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le16_to_cpu(b->bpb.sectors) ||
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le16_to_cpu(b->bpb.sectors_per_fat) ||
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le32_to_cpu(b->bpb.large_sectors) ||
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b->bpb.fats)
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goto not_ntfs;
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Sprintf(silent, "OK\n");
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/* Check clusters per file mft record value is valid. */
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Sprintf(silent, "Checking clusters per mft record... ");
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if ((u8)b->clusters_per_mft_record < 0xe1 ||
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(u8)b->clusters_per_mft_record > 0xf7) {
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switch (b->clusters_per_mft_record) {
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case 1: case 2: case 4: case 8: case 0x10: case 0x20: case 0x40:
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break;
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default:
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goto not_ntfs;
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}
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}
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Sprintf(silent, "OK\n");
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/* Check clusters per index block value is valid. */
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Sprintf(silent, "Checking clusters per index block... ");
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if ((u8)b->clusters_per_index_record < 0xe1 ||
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(u8)b->clusters_per_index_record > 0xf7) {
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switch (b->clusters_per_index_record) {
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case 1: case 2: case 4: case 8: case 0x10: case 0x20: case 0x40:
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break;
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default:
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goto not_ntfs;
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}
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}
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Sprintf(silent, "OK\n");
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if (b->end_of_sector_marker != cpu_to_le16(0xaa55))
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Dputs("Warning: Bootsector has invalid end of sector marker.");
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Sprintf(silent, "Bootsector check completed successfully.\n");
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return TRUE;
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not_ntfs:
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Sprintf(silent, "FAILED\n");
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Sprintf(silent, "Bootsector check failed. Aborting...\n");
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return FALSE;
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}
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/**
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* ntfs_boot_sector_parse - setup an ntfs volume from an ntfs boot sector
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* @vol: ntfs_volume to setup
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* @bs: buffer containing ntfs boot sector to parse
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*
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* Parse the ntfs bootsector @bs and setup the ntfs volume @vol with the
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* obtained values.
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*
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* Return 0 on success or -1 on error with errno set to the error code EINVAL.
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*/
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int ntfs_boot_sector_parse(ntfs_volume *vol, const NTFS_BOOT_SECTOR *bs)
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{
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u8 sectors_per_cluster;
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s8 c;
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/* We return -1 with errno = EINVAL on error. */
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errno = EINVAL;
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vol->sector_size = le16_to_cpu(bs->bpb.bytes_per_sector);
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vol->sector_size_bits = ffs(vol->sector_size) - 1;
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Dprintf("SectorSize = 0x%x\n", vol->sector_size);
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Dprintf("SectorSizeBits = %u\n", vol->sector_size_bits);
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/*
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* The bounds checks on mft_lcn and mft_mirr_lcn (i.e. them being
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* below or equal the number_of_clusters) really belong in the
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* ntfs_boot_sector_is_ntfs but in this way we can just do this once.
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*/
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sectors_per_cluster = bs->bpb.sectors_per_cluster;
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Dprintf("NumberOfSectors = %lli\n", sle64_to_cpu(bs->number_of_sectors));
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Dprintf("SectorsPerCluster = 0x%x\n", sectors_per_cluster);
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if (sectors_per_cluster & (sectors_per_cluster - 1)) {
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Dprintf("Error: %s is not a valid NTFS partition! "
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"sectors_per_cluster is not a power of 2.\n",
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vol->dev->d_name);
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return -1;
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}
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vol->nr_clusters = sle64_to_cpu(bs->number_of_sectors) >>
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(ffs(sectors_per_cluster) - 1);
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vol->mft_lcn = sle64_to_cpu(bs->mft_lcn);
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vol->mftmirr_lcn = sle64_to_cpu(bs->mftmirr_lcn);
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Dprintf("MFT LCN = 0x%llx\n", vol->mft_lcn);
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Dprintf("MFTMirr LCN = 0x%llx\n", vol->mftmirr_lcn);
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if (vol->mft_lcn > vol->nr_clusters ||
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vol->mftmirr_lcn > vol->nr_clusters) {
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Dprintf("Error: %s is not a valid NTFS partition! ($Mft LCN "
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"or\n$MftMirr LCN is greater than the number "
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"of clusters!\n", vol->dev->d_name);
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return -1;
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}
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vol->cluster_size = sectors_per_cluster * vol->sector_size;
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if (vol->cluster_size & (vol->cluster_size - 1)) {
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Dprintf("Error: %s is not a valid NTFS partition! "
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"cluster_size is not a power of 2.\n",
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vol->dev->d_name);
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return -1;
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}
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vol->cluster_size_bits = ffs(vol->cluster_size) - 1;
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/*
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* Need to get the clusters per mft record and handle it if it is
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* negative. Then calculate the mft_record_size. A value of 0x80 is
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* illegal, thus signed char is actually ok!
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*/
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c = bs->clusters_per_mft_record;
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Dprintf("ClusterSize = 0x%x\n", vol->cluster_size);
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Dprintf("ClusterSizeBits = %u\n", vol->cluster_size_bits);
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Dprintf("ClustersPerMftRecord = 0x%x\n", c);
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/*
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* When clusters_per_mft_record is negative, it means that it is to
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* be taken to be the negative base 2 logarithm of the mft_record_size
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* min bytes. Then:
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* mft_record_size = 2^(-clusters_per_mft_record) bytes.
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*/
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if (c < 0)
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vol->mft_record_size = 1 << -c;
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else
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vol->mft_record_size = vol->cluster_size * c;
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if (vol->mft_record_size & (vol->mft_record_size - 1)) {
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Dprintf("Error: %s is not a valid NTFS partition! "
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"mft_record_size is not a power of 2.\n",
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vol->dev->d_name);
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return -1;
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}
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vol->mft_record_size_bits = ffs(vol->mft_record_size) - 1;
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Dprintf("MftRecordSize = 0x%x\n", vol->mft_record_size);
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Dprintf("MftRecordSizeBits = %u\n", vol->mft_record_size_bits);
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/*
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* Work out the size of the MFT mirror in number of mft records. If the
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* cluster size is less than or equal to the size taken by four mft
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* records, the mft mirror stores the first four mft records. If the
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* cluster size is bigger than the size taken by four mft records, the
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* mft mirror contains as many mft records as will fit into one
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* cluster.
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*/
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if (vol->cluster_size <= 4 * vol->mft_record_size)
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vol->mftmirr_size = 4;
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else
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vol->mftmirr_size = vol->cluster_size / vol->mft_record_size;
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return 0;
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}
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