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diff --git a/libntfs-3g/mst.c b/libntfs-3g/mst.c new file mode 100755 index 0000000..470942d --- a/dev/null +++ b/libntfs-3g/mst.c @@ -0,0 +1,231 @@ +/** + * 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(NTFS_RECORD *b, const u32 size) +{ + 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; + ntfs_log_perror("%s: magic: 0x%08x size: %d usa_ofs: %d " + "usa_count: %d", __FUNCTION__, *(le32 *)b, + size, usa_ofs, 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; +} + +/** + * 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); + } +} + |