summaryrefslogtreecommitdiff
path: root/libntfs-3g/mst.c (plain)
blob: 470942d64b3592dcf696f86b9ee3eb0056176878
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 */
50int ntfs_mst_post_read_fixup(NTFS_RECORD *b, const u32 size)
51{
52 u16 usa_ofs, usa_count, usn;
53 u16 *usa_pos, *data_pos;
54
55 ntfs_log_trace("Entering\n");
56
57 /* Setup the variables. */
58 usa_ofs = le16_to_cpu(b->usa_ofs);
59 /* Decrement usa_count to get number of fixups. */
60 usa_count = le16_to_cpu(b->usa_count) - 1;
61 /* Size and alignment checks. */
62 if (size & (NTFS_BLOCK_SIZE - 1) || usa_ofs & 1 ||
63 (u32)(usa_ofs + (usa_count * 2)) > size ||
64 (size >> NTFS_BLOCK_SIZE_BITS) != usa_count) {
65 errno = EINVAL;
66 ntfs_log_perror("%s: magic: 0x%08x size: %d usa_ofs: %d "
67 "usa_count: %d", __FUNCTION__, *(le32 *)b,
68 size, usa_ofs, usa_count);
69 return -1;
70 }
71 /* Position of usn in update sequence array. */
72 usa_pos = (u16*)b + usa_ofs/sizeof(u16);
73 /*
74 * The update sequence number which has to be equal to each of the
75 * u16 values before they are fixed up. Note no need to care for
76 * endianness since we are comparing and moving data for on disk
77 * structures which means the data is consistent. - If it is
78 * consistency the wrong endianness it doesn't make any difference.
79 */
80 usn = *usa_pos;
81 /*
82 * Position in protected data of first u16 that needs fixing up.
83 */
84 data_pos = (u16*)b + NTFS_BLOCK_SIZE/sizeof(u16) - 1;
85 /*
86 * Check for incomplete multi sector transfer(s).
87 */
88 while (usa_count--) {
89 if (*data_pos != usn) {
90 /*
91 * Incomplete multi sector transfer detected! )-:
92 * Set the magic to "BAAD" and return failure.
93 * Note that magic_BAAD is already converted to le32.
94 */
95 errno = EIO;
96 ntfs_log_perror("Incomplete multi-sector transfer: "
97 "magic: 0x%08x size: %d usa_ofs: %d usa_count:"
98 " %d data: %d usn: %d", *(le32 *)b, size,
99 usa_ofs, usa_count, *data_pos, usn);
100 b->magic = magic_BAAD;
101 return -1;
102 }
103 data_pos += NTFS_BLOCK_SIZE/sizeof(u16);
104 }
105 /* Re-setup the variables. */
106 usa_count = le16_to_cpu(b->usa_count) - 1;
107 data_pos = (u16*)b + NTFS_BLOCK_SIZE/sizeof(u16) - 1;
108 /* Fixup all sectors. */
109 while (usa_count--) {
110 /*
111 * Increment position in usa and restore original data from
112 * the usa into the data buffer.
113 */
114 *data_pos = *(++usa_pos);
115 /* Increment position in data as well. */
116 data_pos += NTFS_BLOCK_SIZE/sizeof(u16);
117 }
118 return 0;
119}
120
121/**
122 * ntfs_mst_pre_write_fixup - apply multi sector transfer protection
123 * @b: pointer to the data to protect
124 * @size: size in bytes of @b
125 *
126 * Perform the necessary pre write multi sector transfer fixup on the data
127 * pointer to by @b of @size.
128 *
129 * Return 0 if fixups applied successfully or -1 if no fixups were performed
130 * due to errors. In that case errno i set to the error code (EINVAL).
131 *
132 * NOTE: We consider the absence / invalidity of an update sequence array to
133 * mean error. This means that you have to create a valid update sequence
134 * array header in the ntfs record before calling this function, otherwise it
135 * will fail (the header needs to contain the position of the update sequence
136 * array together with the number of elements in the array). You also need to
137 * initialise the update sequence number before calling this function
138 * otherwise a random word will be used (whatever was in the record at that
139 * position at that time).
140 */
141int ntfs_mst_pre_write_fixup(NTFS_RECORD *b, const u32 size)
142{
143 u16 usa_ofs, usa_count, usn;
144 u16 *usa_pos, *data_pos;
145
146 ntfs_log_trace("Entering\n");
147
148 /* Sanity check + only fixup if it makes sense. */
149 if (!b || ntfs_is_baad_record(b->magic) ||
150 ntfs_is_hole_record(b->magic)) {
151 errno = EINVAL;
152 ntfs_log_perror("%s: bad argument", __FUNCTION__);
153 return -1;
154 }
155 /* Setup the variables. */
156 usa_ofs = le16_to_cpu(b->usa_ofs);
157 /* Decrement usa_count to get number of fixups. */
158 usa_count = le16_to_cpu(b->usa_count) - 1;
159 /* Size and alignment checks. */
160 if (size & (NTFS_BLOCK_SIZE - 1) || usa_ofs & 1 ||
161 (u32)(usa_ofs + (usa_count * 2)) > size ||
162 (size >> NTFS_BLOCK_SIZE_BITS) != usa_count) {
163 errno = EINVAL;
164 ntfs_log_perror("%s", __FUNCTION__);
165 return -1;
166 }
167 /* Position of usn in update sequence array. */
168 usa_pos = (u16*)((u8*)b + usa_ofs);
169 /*
170 * Cyclically increment the update sequence number
171 * (skipping 0 and -1, i.e. 0xffff).
172 */
173 usn = le16_to_cpup(usa_pos) + 1;
174 if (usn == 0xffff || !usn)
175 usn = 1;
176 usn = cpu_to_le16(usn);
177 *usa_pos = usn;
178 /* Position in data of first u16 that needs fixing up. */
179 data_pos = (u16*)b + NTFS_BLOCK_SIZE/sizeof(u16) - 1;
180 /* Fixup all sectors. */
181 while (usa_count--) {
182 /*
183 * Increment the position in the usa and save the
184 * original data from the data buffer into the usa.
185 */
186 *(++usa_pos) = *data_pos;
187 /* Apply fixup to data. */
188 *data_pos = usn;
189 /* Increment position in data as well. */
190 data_pos += NTFS_BLOCK_SIZE/sizeof(u16);
191 }
192 return 0;
193}
194
195/**
196 * ntfs_mst_post_write_fixup - deprotect multi sector transfer protected data
197 * @b: pointer to the data to deprotect
198 *
199 * Perform the necessary post write multi sector transfer fixup, not checking
200 * for any errors, because we assume we have just used
201 * ntfs_mst_pre_write_fixup(), thus the data will be fine or we would never
202 * have gotten here.
203 */
204void ntfs_mst_post_write_fixup(NTFS_RECORD *b)
205{
206 u16 *usa_pos, *data_pos;
207
208 u16 usa_ofs = le16_to_cpu(b->usa_ofs);
209 u16 usa_count = le16_to_cpu(b->usa_count) - 1;
210
211 ntfs_log_trace("Entering\n");
212
213 /* Position of usn in update sequence array. */
214 usa_pos = (u16*)b + usa_ofs/sizeof(u16);
215
216 /* Position in protected data of first u16 that needs fixing up. */
217 data_pos = (u16*)b + NTFS_BLOCK_SIZE/sizeof(u16) - 1;
218
219 /* Fixup all sectors. */
220 while (usa_count--) {
221 /*
222 * Increment position in usa and restore original data from
223 * the usa into the data buffer.
224 */
225 *data_pos = *(++usa_pos);
226
227 /* Increment position in data as well. */
228 data_pos += NTFS_BLOCK_SIZE/sizeof(u16);
229 }
230}
231
232
generated by cgit at 2024-05-19 05:17:46 (GMT)