release/src/router/ntfs-3g/libntfs-3g/mst.c

   1 /**
   2  * mst.c - Multi sector fixup handling code. Originated from the Linux-NTFS project.
   3  *
   4  * Copyright (c) 2000-2004 Anton Altaparmakov
   5  * Copyright (c) 2006-2009 Szabolcs Szakacsits
   6  *
   7  * This program/include file is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU General Public License as published
   9  * by the Free Software Foundation; either version 2 of the License, or
  10  * (at your option) any later version.
  11  *
  12  * This program/include file is distributed in the hope that it will be
  13  * useful, but WITHOUT ANY WARRANTY; without even the implied warranty
  14  * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  * GNU General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU General Public License
  18  * along with this program (in the main directory of the NTFS-3G
  19  * distribution in the file COPYING); if not, write to the Free Software
  20  * Foundation,Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  21  */
  22
  23 #ifdef HAVE_CONFIG_H
  24 #include "config.h"
  25 #endif
  26
  27 #ifdef HAVE_ERRNO_H
  28 #include <errno.h>
  29 #endif
  30
  31 #include "mst.h"
  32 #include "logging.h"
  33
  34 /**
  35  * ntfs_mst_post_read_fixup - deprotect multi sector transfer protected data
  36  * @b:          pointer to the data to deprotect
  37  * @size:       size in bytes of @b
  38  *
  39  * Perform the necessary post read multi sector transfer fixups and detect the
  40  * presence of incomplete multi sector transfers. - In that case, overwrite the
  41  * magic of the ntfs record header being processed with "BAAD" (in memory only!)
  42  * and abort processing.
  43  *
  44  * Return 0 on success and -1 on error, with errno set to the error code. The
  45  * following error codes are defined:
  46  *      EINVAL  Invalid arguments or invalid NTFS record in buffer @b.
  47  *      EIO     Multi sector transfer error was detected. Magic of the NTFS
  48  *              record in @b will have been set to "BAAD".
  49  */
  50 int ntfs_mst_post_read_fixup_warn(NTFS_RECORD *b, const u32 size,
  51                                         BOOL warn)
  52 {
  53         u16 usa_ofs, usa_count, usn;
  54         u16 *usa_pos, *data_pos;
  55
  56         ntfs_log_trace("Entering\n");
  57
  58         /* Setup the variables. */
  59         usa_ofs = le16_to_cpu(b->usa_ofs);
  60         /* Decrement usa_count to get number of fixups. */
  61         usa_count = le16_to_cpu(b->usa_count) - 1;
  62         /* Size and alignment checks. */
  63         if (size & (NTFS_BLOCK_SIZE - 1) || usa_ofs & 1 ||
  64                         (u32)(usa_ofs + (usa_count * 2)) > size ||
  65                         (size >> NTFS_BLOCK_SIZE_BITS) != usa_count) {
  66                 errno = EINVAL;
  67                 if (warn) {
  68                         ntfs_log_perror("%s: magic: 0x%08lx  size: %ld "
  69                                         "  usa_ofs: %d  usa_count: %u",
  70                                          __FUNCTION__,
  71                                         (long)le32_to_cpu(*(le32 *)b),
  72                                         (long)size, (int)usa_ofs,
  73                                         (unsigned int)usa_count);
  74                 }
  75                 return -1;
  76         }
  77         /* Position of usn in update sequence array. */
  78         usa_pos = (u16*)b + usa_ofs/sizeof(u16);
  79         /*
  80          * The update sequence number which has to be equal to each of the
  81          * u16 values before they are fixed up. Note no need to care for
  82          * endianness since we are comparing and moving data for on disk
  83          * structures which means the data is consistent. - If it is
  84          * consistency the wrong endianness it doesn't make any difference.
  85          */
  86         usn = *usa_pos;
  87         /*
  88          * Position in protected data of first u16 that needs fixing up.
  89          */
  90         data_pos = (u16*)b + NTFS_BLOCK_SIZE/sizeof(u16) - 1;
  91         /*
  92          * Check for incomplete multi sector transfer(s).
  93          */
  94         while (usa_count--) {
  95                 if (*data_pos != usn) {
  96                         /*
  97                          * Incomplete multi sector transfer detected! )-:
  98                          * Set the magic to "BAAD" and return failure.
  99                          * Note that magic_BAAD is already converted to le32.
 100                          */
 101                         errno = EIO;
 102                         ntfs_log_perror("Incomplete multi-sector transfer: "
 103                                 "magic: 0x%08x  size: %d  usa_ofs: %d  usa_count:"
 104                                 " %d  data: %d  usn: %d", *(le32 *)b, size,
 105                                 usa_ofs, usa_count, *data_pos, usn);
 106                         b->magic = magic_BAAD;
 107                         return -1;
 108                 }
 109                 data_pos += NTFS_BLOCK_SIZE/sizeof(u16);
 110         }
 111         /* Re-setup the variables. */
 112         usa_count = le16_to_cpu(b->usa_count) - 1;
 113         data_pos = (u16*)b + NTFS_BLOCK_SIZE/sizeof(u16) - 1;
 114         /* Fixup all sectors. */
 115         while (usa_count--) {
 116                 /*
 117                  * Increment position in usa and restore original data from
 118                  * the usa into the data buffer.
 119                  */
 120                 *data_pos = *(++usa_pos);
 121                 /* Increment position in data as well. */
 122                 data_pos += NTFS_BLOCK_SIZE/sizeof(u16);
 123         }
 124         return 0;
 125 }
 126
 127 /*
 128  *              Deprotect multi sector transfer protected data
 129  *      with a warning if an error is found.
 130  */
 131
 132 int ntfs_mst_post_read_fixup(NTFS_RECORD *b, const u32 size)
 133 {
 134         return (ntfs_mst_post_read_fixup_warn(b,size,TRUE));
 135 }
 136
 137 /**
 138  * ntfs_mst_pre_write_fixup - apply multi sector transfer protection
 139  * @b:          pointer to the data to protect
 140  * @size:       size in bytes of @b
 141  *
 142  * Perform the necessary pre write multi sector transfer fixup on the data
 143  * pointer to by @b of @size.
 144  *
 145  * Return 0 if fixups applied successfully or -1 if no fixups were performed
 146  * due to errors. In that case errno i set to the error code (EINVAL).
 147  *
 148  * NOTE: We consider the absence / invalidity of an update sequence array to
 149  * mean error. This means that you have to create a valid update sequence
 150  * array header in the ntfs record before calling this function, otherwise it
 151  * will fail (the header needs to contain the position of the update sequence
 152  * array together with the number of elements in the array). You also need to
 153  * initialise the update sequence number before calling this function
 154  * otherwise a random word will be used (whatever was in the record at that
 155  * position at that time).
 156  */
 157 int ntfs_mst_pre_write_fixup(NTFS_RECORD *b, const u32 size)
 158 {
 159         u16 usa_ofs, usa_count, usn;
 160         u16 *usa_pos, *data_pos;
 161
 162         ntfs_log_trace("Entering\n");
 163
 164         /* Sanity check + only fixup if it makes sense. */
 165         if (!b || ntfs_is_baad_record(b->magic) ||
 166                         ntfs_is_hole_record(b->magic)) {
 167                 errno = EINVAL;
 168                 ntfs_log_perror("%s: bad argument", __FUNCTION__);
 169                 return -1;
 170         }
 171         /* Setup the variables. */
 172         usa_ofs = le16_to_cpu(b->usa_ofs);
 173         /* Decrement usa_count to get number of fixups. */
 174         usa_count = le16_to_cpu(b->usa_count) - 1;
 175         /* Size and alignment checks. */
 176         if (size & (NTFS_BLOCK_SIZE - 1) || usa_ofs & 1 ||
 177                         (u32)(usa_ofs + (usa_count * 2)) > size ||
 178                         (size >> NTFS_BLOCK_SIZE_BITS) != usa_count) {
 179                 errno = EINVAL;
 180                 ntfs_log_perror("%s", __FUNCTION__);
 181                 return -1;
 182         }
 183         /* Position of usn in update sequence array. */
 184         usa_pos = (u16*)((u8*)b + usa_ofs);
 185         /*
 186          * Cyclically increment the update sequence number
 187          * (skipping 0 and -1, i.e. 0xffff).
 188          */
 189         usn = le16_to_cpup(usa_pos) + 1;
 190         if (usn == 0xffff || !usn)
 191                 usn = 1;
 192         usn = cpu_to_le16(usn);
 193         *usa_pos = usn;
 194         /* Position in data of first u16 that needs fixing up. */
 195         data_pos = (u16*)b + NTFS_BLOCK_SIZE/sizeof(u16) - 1;
 196         /* Fixup all sectors. */
 197         while (usa_count--) {
 198                 /*
 199                  * Increment the position in the usa and save the
 200                  * original data from the data buffer into the usa.
 201                  */
 202                 *(++usa_pos) = *data_pos;
 203                 /* Apply fixup to data. */
 204                 *data_pos = usn;
 205                 /* Increment position in data as well. */
 206                 data_pos += NTFS_BLOCK_SIZE/sizeof(u16);
 207         }
 208         return 0;
 209 }
 210
 211 /**
 212  * ntfs_mst_post_write_fixup - deprotect multi sector transfer protected data
 213  * @b:          pointer to the data to deprotect
 214  *
 215  * Perform the necessary post write multi sector transfer fixup, not checking
 216  * for any errors, because we assume we have just used
 217  * ntfs_mst_pre_write_fixup(), thus the data will be fine or we would never
 218  * have gotten here.
 219  */
 220 void ntfs_mst_post_write_fixup(NTFS_RECORD *b)
 221 {
 222         u16 *usa_pos, *data_pos;
 223
 224         u16 usa_ofs = le16_to_cpu(b->usa_ofs);
 225         u16 usa_count = le16_to_cpu(b->usa_count) - 1;
 226
 227         ntfs_log_trace("Entering\n");
 228
 229         /* Position of usn in update sequence array. */
 230         usa_pos = (u16*)b + usa_ofs/sizeof(u16);
 231
 232         /* Position in protected data of first u16 that needs fixing up. */
 233         data_pos = (u16*)b + NTFS_BLOCK_SIZE/sizeof(u16) - 1;
 234
 235         /* Fixup all sectors. */
 236         while (usa_count--) {
 237                 /*
 238                  * Increment position in usa and restore original data from
 239                  * the usa into the data buffer.
 240                  */
 241                 *data_pos = *(++usa_pos);
 242
 243                 /* Increment position in data as well. */
 244                 data_pos += NTFS_BLOCK_SIZE/sizeof(u16);
 245         }
 246 }
 247