204 lines
6.9 KiB
C
204 lines
6.9 KiB
C
/*
|
|
* mst.c - NTFS multi sector transfer protection handling code. Part of the
|
|
* Linux-NTFS project.
|
|
*
|
|
* Copyright (c) 2001-2004 Anton Altaparmakov
|
|
*
|
|
* This program/include file 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/include file 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 this program (in the main directory of the Linux-NTFS
|
|
* distribution in the file COPYING); if not, write to the Free Software
|
|
* Foundation,Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
|
|
*/
|
|
|
|
#include "ntfs.h"
|
|
|
|
/**
|
|
* post_read_mst_fixup - deprotect multi sector transfer protected data
|
|
* @b: pointer to the data to deprotect
|
|
* @size: size in bytes of @b
|
|
*
|
|
* Perform the necessary post read multi sector transfer fixup and detect the
|
|
* presence of incomplete multi sector transfers. - In that case, overwrite the
|
|
* magic of the ntfs record header being processed with "BAAD" (in memory only!)
|
|
* and abort processing.
|
|
*
|
|
* Return 0 on success and -EINVAL on error ("BAAD" magic will be present).
|
|
*
|
|
* NOTE: We consider the absence / invalidity of an update sequence array to
|
|
* mean that the structure is not protected at all and hence doesn't need to
|
|
* be fixed up. Thus, we return success and not failure in this case. This is
|
|
* in contrast to pre_write_mst_fixup(), see below.
|
|
*/
|
|
int post_read_mst_fixup(NTFS_RECORD *b, const u32 size)
|
|
{
|
|
u16 usa_ofs, usa_count, usn;
|
|
u16 *usa_pos, *data_pos;
|
|
|
|
/* Setup the variables. */
|
|
usa_ofs = le16_to_cpu(b->usa_ofs);
|
|
/* Decrement usa_count to get number of fixups. */
|
|
usa_count = le16_to_cpu(b->usa_count) - 1;
|
|
/* Size and alignment checks. */
|
|
if ( size & (NTFS_BLOCK_SIZE - 1) ||
|
|
usa_ofs & 1 ||
|
|
usa_ofs + (usa_count * 2) > size ||
|
|
(size >> NTFS_BLOCK_SIZE_BITS) != usa_count)
|
|
return 0;
|
|
/* Position of usn in update sequence array. */
|
|
usa_pos = (u16*)b + usa_ofs/sizeof(u16);
|
|
/*
|
|
* The update sequence number which has to be equal to each of the
|
|
* u16 values before they are fixed up. Note no need to care for
|
|
* endianness since we are comparing and moving data for on disk
|
|
* structures which means the data is consistent. - If it is
|
|
* consistenty the wrong endianness it doesn't make any difference.
|
|
*/
|
|
usn = *usa_pos;
|
|
/*
|
|
* Position in protected data of first u16 that needs fixing up.
|
|
*/
|
|
data_pos = (u16*)b + NTFS_BLOCK_SIZE/sizeof(u16) - 1;
|
|
/*
|
|
* Check for incomplete multi sector transfer(s).
|
|
*/
|
|
while (usa_count--) {
|
|
if (*data_pos != usn) {
|
|
/*
|
|
* Incomplete multi sector transfer detected! )-:
|
|
* Set the magic to "BAAD" and return failure.
|
|
* Note that magic_BAAD is already converted to le32.
|
|
*/
|
|
b->magic = magic_BAAD;
|
|
return -EINVAL;
|
|
}
|
|
data_pos += NTFS_BLOCK_SIZE/sizeof(u16);
|
|
}
|
|
/* Re-setup the variables. */
|
|
usa_count = le16_to_cpu(b->usa_count) - 1;
|
|
data_pos = (u16*)b + NTFS_BLOCK_SIZE/sizeof(u16) - 1;
|
|
/* Fixup all sectors. */
|
|
while (usa_count--) {
|
|
/*
|
|
* Increment position in usa and restore original data from
|
|
* the usa into the data buffer.
|
|
*/
|
|
*data_pos = *(++usa_pos);
|
|
/* Increment position in data as well. */
|
|
data_pos += NTFS_BLOCK_SIZE/sizeof(u16);
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
/**
|
|
* pre_write_mst_fixup - apply multi sector transfer protection
|
|
* @b: pointer to the data to protect
|
|
* @size: size in bytes of @b
|
|
*
|
|
* Perform the necessary pre write multi sector transfer fixup on the data
|
|
* pointer to by @b of @size.
|
|
*
|
|
* Return 0 if fixup applied (success) or -EINVAL if no fixup was performed
|
|
* (assumed not needed). This is in contrast to post_read_mst_fixup() above.
|
|
*
|
|
* NOTE: We consider the absence / invalidity of an update sequence array to
|
|
* mean that the structure is not subject to protection and hence doesn't need
|
|
* to be fixed up. This means that you have to create a valid update sequence
|
|
* array header in the ntfs record before calling this function, otherwise it
|
|
* will fail (the header needs to contain the position of the update sequence
|
|
* array together with the number of elements in the array). You also need to
|
|
* initialise the update sequence number before calling this function
|
|
* otherwise a random word will be used (whatever was in the record at that
|
|
* position at that time).
|
|
*/
|
|
int pre_write_mst_fixup(NTFS_RECORD *b, const u32 size)
|
|
{
|
|
le16 *usa_pos, *data_pos;
|
|
u16 usa_ofs, usa_count, usn;
|
|
le16 le_usn;
|
|
|
|
/* Sanity check + only fixup if it makes sense. */
|
|
if (!b || ntfs_is_baad_record(b->magic) ||
|
|
ntfs_is_hole_record(b->magic))
|
|
return -EINVAL;
|
|
/* Setup the variables. */
|
|
usa_ofs = le16_to_cpu(b->usa_ofs);
|
|
/* Decrement usa_count to get number of fixups. */
|
|
usa_count = le16_to_cpu(b->usa_count) - 1;
|
|
/* Size and alignment checks. */
|
|
if ( size & (NTFS_BLOCK_SIZE - 1) ||
|
|
usa_ofs & 1 ||
|
|
usa_ofs + (usa_count * 2) > size ||
|
|
(size >> NTFS_BLOCK_SIZE_BITS) != usa_count)
|
|
return -EINVAL;
|
|
/* Position of usn in update sequence array. */
|
|
usa_pos = (le16*)((u8*)b + usa_ofs);
|
|
/*
|
|
* Cyclically increment the update sequence number
|
|
* (skipping 0 and -1, i.e. 0xffff).
|
|
*/
|
|
usn = le16_to_cpup(usa_pos) + 1;
|
|
if (usn == 0xffff || !usn)
|
|
usn = 1;
|
|
le_usn = cpu_to_le16(usn);
|
|
*usa_pos = le_usn;
|
|
/* Position in data of first u16 that needs fixing up. */
|
|
data_pos = (le16*)b + NTFS_BLOCK_SIZE/sizeof(le16) - 1;
|
|
/* Fixup all sectors. */
|
|
while (usa_count--) {
|
|
/*
|
|
* Increment the position in the usa and save the
|
|
* original data from the data buffer into the usa.
|
|
*/
|
|
*(++usa_pos) = *data_pos;
|
|
/* Apply fixup to data. */
|
|
*data_pos = le_usn;
|
|
/* Increment position in data as well. */
|
|
data_pos += NTFS_BLOCK_SIZE/sizeof(le16);
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
/**
|
|
* post_write_mst_fixup - fast deprotect multi sector transfer protected data
|
|
* @b: pointer to the data to deprotect
|
|
*
|
|
* Perform the necessary post write multi sector transfer fixup, not checking
|
|
* for any errors, because we assume we have just used pre_write_mst_fixup(),
|
|
* thus the data will be fine or we would never have gotten here.
|
|
*/
|
|
void post_write_mst_fixup(NTFS_RECORD *b)
|
|
{
|
|
le16 *usa_pos, *data_pos;
|
|
|
|
u16 usa_ofs = le16_to_cpu(b->usa_ofs);
|
|
u16 usa_count = le16_to_cpu(b->usa_count) - 1;
|
|
|
|
/* Position of usn in update sequence array. */
|
|
usa_pos = (le16*)b + usa_ofs/sizeof(le16);
|
|
|
|
/* Position in protected data of first u16 that needs fixing up. */
|
|
data_pos = (le16*)b + NTFS_BLOCK_SIZE/sizeof(le16) - 1;
|
|
|
|
/* Fixup all sectors. */
|
|
while (usa_count--) {
|
|
/*
|
|
* Increment position in usa and restore original data from
|
|
* the usa into the data buffer.
|
|
*/
|
|
*data_pos = *(++usa_pos);
|
|
|
|
/* Increment position in data as well. */
|
|
data_pos += NTFS_BLOCK_SIZE/sizeof(le16);
|
|
}
|
|
}
|