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 } 247 248