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_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
132int 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 */
157int 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 */
220void 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