libntfs/source/mst.c

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/**
* mst.c - Multi sector fixup handling code. Originated from the Linux-NTFS project.
*
* Copyright (c) 2000-2004 Anton Altaparmakov
* Copyright (c) 2006-2009 Szabolcs Szakacsits
*
* 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 NTFS-3G
* distribution in the file COPYING); if not, write to the Free Software
* Foundation,Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#ifdef HAVE_ERRNO_H
#include <errno.h>
#endif
#include "mst.h"
#include "logging.h"
/**
* ntfs_mst_post_read_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 fixups 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 -1 on error, with errno set to the error code. The
* following error codes are defined:
* EINVAL Invalid arguments or invalid NTFS record in buffer @b.
* EIO Multi sector transfer error was detected. Magic of the NTFS
* record in @b will have been set to "BAAD".
*/
int ntfs_mst_post_read_fixup_warn(NTFS_RECORD *b, const u32 size,
BOOL warn)
{
u16 usa_ofs, usa_count, usn;
u16 *usa_pos, *data_pos;
ntfs_log_trace("Entering\n");
/* 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 ||
(u32)(usa_ofs + (usa_count * 2)) > size ||
(size >> NTFS_BLOCK_SIZE_BITS) != usa_count) {
errno = EINVAL;
if (warn) {
ntfs_log_perror("%s: magic: 0x%08lx size: %ld "
" usa_ofs: %d usa_count: %u",
__FUNCTION__,
(long)le32_to_cpu(*(le32 *)b),
(long)size, (int)usa_ofs,
(unsigned int)usa_count);
}
return -1;
}
/* 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
* consistency 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.
*/
errno = EIO;
ntfs_log_perror("Incomplete multi-sector transfer: "
"magic: 0x%08x size: %d usa_ofs: %d usa_count:"
" %d data: %d usn: %d", *(le32 *)b, size,
usa_ofs, usa_count, *data_pos, usn);
b->magic = magic_BAAD;
return -1;
}
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;
}
/*
* Deprotect multi sector transfer protected data
* with a warning if an error is found.
*/
int ntfs_mst_post_read_fixup(NTFS_RECORD *b, const u32 size)
{
return (ntfs_mst_post_read_fixup_warn(b,size,TRUE));
}
/**
* ntfs_mst_pre_write_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 fixups applied successfully or -1 if no fixups were performed
* due to errors. In that case errno i set to the error code (EINVAL).
*
* NOTE: We consider the absence / invalidity of an update sequence array to
* mean error. 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 ntfs_mst_pre_write_fixup(NTFS_RECORD *b, const u32 size)
{
u16 usa_ofs, usa_count, usn;
u16 *usa_pos, *data_pos;
ntfs_log_trace("Entering\n");
/* Sanity check + only fixup if it makes sense. */
if (!b || ntfs_is_baad_record(b->magic) ||
ntfs_is_hole_record(b->magic)) {
errno = EINVAL;
ntfs_log_perror("%s: bad argument", __FUNCTION__);
return -1;
}
/* 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 ||
(u32)(usa_ofs + (usa_count * 2)) > size ||
(size >> NTFS_BLOCK_SIZE_BITS) != usa_count) {
errno = EINVAL;
ntfs_log_perror("%s", __FUNCTION__);
return -1;
}
/* Position of usn in update sequence array. */
usa_pos = (u16*)((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;
usn = cpu_to_le16(usn);
*usa_pos = usn;
/* Position in data of first u16 that needs fixing up. */
data_pos = (u16*)b + NTFS_BLOCK_SIZE/sizeof(u16) - 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 = usn;
/* Increment position in data as well. */
data_pos += NTFS_BLOCK_SIZE/sizeof(u16);
}
return 0;
}
/**
* ntfs_mst_post_write_fixup - 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
* ntfs_mst_pre_write_fixup(), thus the data will be fine or we would never
* have gotten here.
*/
void ntfs_mst_post_write_fixup(NTFS_RECORD *b)
{
u16 *usa_pos, *data_pos;
u16 usa_ofs = le16_to_cpu(b->usa_ofs);
u16 usa_count = le16_to_cpu(b->usa_count) - 1;
ntfs_log_trace("Entering\n");
/* Position of usn in update sequence array. */
usa_pos = (u16*)b + usa_ofs/sizeof(u16);
/* Position in protected data of first u16 that needs fixing up. */
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);
}
}