1 // SPDX-License-Identifier: GPL-2.0-or-later
3  * mst.c - NTFS multi sector transfer protection handling code. Part of the
4  *	   Linux-NTFS project.
6  * Copyright (c) 2001-2004 Anton Altaparmakov
12  * post_read_mst_fixup - deprotect multi sector transfer protected data
13  * @b:		pointer to the data to deprotect
16  * Perform the necessary post read multi sector transfer fixup and detect the
17  * presence of incomplete multi sector transfers. - In that case, overwrite the
21  * Return 0 on success and -EINVAL on error ("BAAD" magic will be present).
34 	usa_ofs = le16_to_cpu(b->usa_ofs);  in post_read_mst_fixup()
36 	usa_count = le16_to_cpu(b->usa_count) - 1;  in post_read_mst_fixup()
38 	if ( size & (NTFS_BLOCK_SIZE - 1)	||  in post_read_mst_fixup()
48 	 * endianness since we are comparing and moving data for on disk  in post_read_mst_fixup()
49 	 * structures which means the data is consistent. - If it is  in post_read_mst_fixup()
54 	 * Position in protected data of first u16 that needs fixing up.  in post_read_mst_fixup()
56 	data_pos = (u16*)b + NTFS_BLOCK_SIZE/sizeof(u16) - 1;  in post_read_mst_fixup()
58 	 * Check for incomplete multi sector transfer(s).  in post_read_mst_fixup()
60 	while (usa_count--) {  in post_read_mst_fixup()
63 			 * Incomplete multi sector transfer detected! )-:  in post_read_mst_fixup()
67 			b->magic = magic_BAAD;  in post_read_mst_fixup()
68 			return -EINVAL;  in post_read_mst_fixup()
72 	/* Re-setup the variables. */  in post_read_mst_fixup()
73 	usa_count = le16_to_cpu(b->usa_count) - 1;  in post_read_mst_fixup()
74 	data_pos = (u16*)b + NTFS_BLOCK_SIZE/sizeof(u16) - 1;  in post_read_mst_fixup()
76 	while (usa_count--) {  in post_read_mst_fixup()
78 		 * Increment position in usa and restore original data from  in post_read_mst_fixup()
79 		 * the usa into the data buffer.  in post_read_mst_fixup()
82 		/* Increment position in data as well. */  in post_read_mst_fixup()
89  * pre_write_mst_fixup - apply multi sector transfer protection
90  * @b:		pointer to the data to protect
93  * Perform the necessary pre write multi sector transfer fixup on the data
96  * Return 0 if fixup applied (success) or -EINVAL if no fixup was performed
116 	if (!b || ntfs_is_baad_record(b->magic) ||  in pre_write_mst_fixup()
117 			ntfs_is_hole_record(b->magic))  in pre_write_mst_fixup()
118 		return -EINVAL;  in pre_write_mst_fixup()
120 	usa_ofs = le16_to_cpu(b->usa_ofs);  in pre_write_mst_fixup()
122 	usa_count = le16_to_cpu(b->usa_count) - 1;  in pre_write_mst_fixup()
124 	if ( size & (NTFS_BLOCK_SIZE - 1)	||  in pre_write_mst_fixup()
128 		return -EINVAL;  in pre_write_mst_fixup()
133 	 * (skipping 0 and -1, i.e. 0xffff).  in pre_write_mst_fixup()
140 	/* Position in data of first u16 that needs fixing up. */  in pre_write_mst_fixup()
141 	data_pos = (le16*)b + NTFS_BLOCK_SIZE/sizeof(le16) - 1;  in pre_write_mst_fixup()
143 	while (usa_count--) {  in pre_write_mst_fixup()
146 		 * original data from the data buffer into the usa.  in pre_write_mst_fixup()
149 		/* Apply fixup to data. */  in pre_write_mst_fixup()
151 		/* Increment position in data as well. */  in pre_write_mst_fixup()
158  * post_write_mst_fixup - fast deprotect multi sector transfer protected data
159  * @b:		pointer to the data to deprotect
161  * Perform the necessary post write multi sector transfer fixup, not checking
163  * thus the data will be fine or we would never have gotten here.
169 	u16 usa_ofs = le16_to_cpu(b->usa_ofs);  in post_write_mst_fixup()
170 	u16 usa_count = le16_to_cpu(b->usa_count) - 1;  in post_write_mst_fixup()
175 	/* Position in protected data of first u16 that needs fixing up. */  in post_write_mst_fixup()
176 	data_pos = (le16*)b + NTFS_BLOCK_SIZE/sizeof(le16) - 1;  in post_write_mst_fixup()
179 	while (usa_count--) {  in post_write_mst_fixup()
181 		 * Increment position in usa and restore original data from  in post_write_mst_fixup()
182 		 * the usa into the data buffer.  in post_write_mst_fixup()
186 		/* Increment position in data as well. */  in post_write_mst_fixup()