1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /* RomFS storage access routines
3 *
4 * Copyright © 2007 Red Hat, Inc. All Rights Reserved.
5 * Written by David Howells (dhowells@redhat.com)
6 */
7
8 #include <linux/fs.h>
9 #include <linux/mtd/super.h>
10 #include <linux/buffer_head.h>
11 #include "internal.h"
12
13 #if !defined(CONFIG_ROMFS_ON_MTD) && !defined(CONFIG_ROMFS_ON_BLOCK)
14 #error no ROMFS backing store interface configured
15 #endif
16
17 #ifdef CONFIG_ROMFS_ON_MTD
18 #define ROMFS_MTD_READ(sb, ...) mtd_read((sb)->s_mtd, ##__VA_ARGS__)
19
20 /*
21 * read data from an romfs image on an MTD device
22 */
romfs_mtd_read(struct super_block * sb,unsigned long pos,void * buf,size_t buflen)23 static int romfs_mtd_read(struct super_block *sb, unsigned long pos,
24 void *buf, size_t buflen)
25 {
26 size_t rlen;
27 int ret;
28
29 ret = ROMFS_MTD_READ(sb, pos, buflen, &rlen, buf);
30 return (ret < 0 || rlen != buflen) ? -EIO : 0;
31 }
32
33 /*
34 * determine the length of a string in a romfs image on an MTD device
35 */
romfs_mtd_strnlen(struct super_block * sb,unsigned long pos,size_t maxlen)36 static ssize_t romfs_mtd_strnlen(struct super_block *sb,
37 unsigned long pos, size_t maxlen)
38 {
39 ssize_t n = 0;
40 size_t segment;
41 u_char buf[16], *p;
42 size_t len;
43 int ret;
44
45 /* scan the string up to 16 bytes at a time */
46 while (maxlen > 0) {
47 segment = min_t(size_t, maxlen, 16);
48 ret = ROMFS_MTD_READ(sb, pos, segment, &len, buf);
49 if (ret < 0)
50 return ret;
51 p = memchr(buf, 0, len);
52 if (p)
53 return n + (p - buf);
54 maxlen -= len;
55 pos += len;
56 n += len;
57 }
58
59 return n;
60 }
61
62 /*
63 * compare a string to one in a romfs image on MTD
64 * - return 1 if matched, 0 if differ, -ve if error
65 */
romfs_mtd_strcmp(struct super_block * sb,unsigned long pos,const char * str,size_t size)66 static int romfs_mtd_strcmp(struct super_block *sb, unsigned long pos,
67 const char *str, size_t size)
68 {
69 u_char buf[17];
70 size_t len, segment;
71 int ret;
72
73 /* scan the string up to 16 bytes at a time, and attempt to grab the
74 * trailing NUL whilst we're at it */
75 buf[0] = 0xff;
76
77 while (size > 0) {
78 segment = min_t(size_t, size + 1, 17);
79 ret = ROMFS_MTD_READ(sb, pos, segment, &len, buf);
80 if (ret < 0)
81 return ret;
82 len--;
83 if (memcmp(buf, str, len) != 0)
84 return 0;
85 buf[0] = buf[len];
86 size -= len;
87 pos += len;
88 str += len;
89 }
90
91 /* check the trailing NUL was */
92 if (buf[0])
93 return 0;
94
95 return 1;
96 }
97 #endif /* CONFIG_ROMFS_ON_MTD */
98
99 #ifdef CONFIG_ROMFS_ON_BLOCK
100 /*
101 * read data from an romfs image on a block device
102 */
romfs_blk_read(struct super_block * sb,unsigned long pos,void * buf,size_t buflen)103 static int romfs_blk_read(struct super_block *sb, unsigned long pos,
104 void *buf, size_t buflen)
105 {
106 struct buffer_head *bh;
107 unsigned long offset;
108 size_t segment;
109
110 /* copy the string up to blocksize bytes at a time */
111 while (buflen > 0) {
112 offset = pos & (ROMBSIZE - 1);
113 segment = min_t(size_t, buflen, ROMBSIZE - offset);
114 bh = sb_bread(sb, pos >> ROMBSBITS);
115 if (!bh)
116 return -EIO;
117 memcpy(buf, bh->b_data + offset, segment);
118 brelse(bh);
119 buf += segment;
120 buflen -= segment;
121 pos += segment;
122 }
123
124 return 0;
125 }
126
127 /*
128 * determine the length of a string in romfs on a block device
129 */
romfs_blk_strnlen(struct super_block * sb,unsigned long pos,size_t limit)130 static ssize_t romfs_blk_strnlen(struct super_block *sb,
131 unsigned long pos, size_t limit)
132 {
133 struct buffer_head *bh;
134 unsigned long offset;
135 ssize_t n = 0;
136 size_t segment;
137 u_char *buf, *p;
138
139 /* scan the string up to blocksize bytes at a time */
140 while (limit > 0) {
141 offset = pos & (ROMBSIZE - 1);
142 segment = min_t(size_t, limit, ROMBSIZE - offset);
143 bh = sb_bread(sb, pos >> ROMBSBITS);
144 if (!bh)
145 return -EIO;
146 buf = bh->b_data + offset;
147 p = memchr(buf, 0, segment);
148 brelse(bh);
149 if (p)
150 return n + (p - buf);
151 limit -= segment;
152 pos += segment;
153 n += segment;
154 }
155
156 return n;
157 }
158
159 /*
160 * compare a string to one in a romfs image on a block device
161 * - return 1 if matched, 0 if differ, -ve if error
162 */
romfs_blk_strcmp(struct super_block * sb,unsigned long pos,const char * str,size_t size)163 static int romfs_blk_strcmp(struct super_block *sb, unsigned long pos,
164 const char *str, size_t size)
165 {
166 struct buffer_head *bh;
167 unsigned long offset;
168 size_t segment;
169 bool matched, terminated = false;
170
171 /* compare string up to a block at a time */
172 while (size > 0) {
173 offset = pos & (ROMBSIZE - 1);
174 segment = min_t(size_t, size, ROMBSIZE - offset);
175 bh = sb_bread(sb, pos >> ROMBSBITS);
176 if (!bh)
177 return -EIO;
178 matched = (memcmp(bh->b_data + offset, str, segment) == 0);
179
180 size -= segment;
181 pos += segment;
182 str += segment;
183 if (matched && size == 0 && offset + segment < ROMBSIZE) {
184 if (!bh->b_data[offset + segment])
185 terminated = true;
186 else
187 matched = false;
188 }
189 brelse(bh);
190 if (!matched)
191 return 0;
192 }
193
194 if (!terminated) {
195 /* the terminating NUL must be on the first byte of the next
196 * block */
197 BUG_ON((pos & (ROMBSIZE - 1)) != 0);
198 bh = sb_bread(sb, pos >> ROMBSBITS);
199 if (!bh)
200 return -EIO;
201 matched = !bh->b_data[0];
202 brelse(bh);
203 if (!matched)
204 return 0;
205 }
206
207 return 1;
208 }
209 #endif /* CONFIG_ROMFS_ON_BLOCK */
210
211 /*
212 * read data from the romfs image
213 */
romfs_dev_read(struct super_block * sb,unsigned long pos,void * buf,size_t buflen)214 int romfs_dev_read(struct super_block *sb, unsigned long pos,
215 void *buf, size_t buflen)
216 {
217 size_t limit;
218
219 limit = romfs_maxsize(sb);
220 if (pos >= limit || buflen > limit - pos)
221 return -EIO;
222
223 #ifdef CONFIG_ROMFS_ON_MTD
224 if (sb->s_mtd)
225 return romfs_mtd_read(sb, pos, buf, buflen);
226 #endif
227 #ifdef CONFIG_ROMFS_ON_BLOCK
228 if (sb->s_bdev)
229 return romfs_blk_read(sb, pos, buf, buflen);
230 #endif
231 return -EIO;
232 }
233
234 /*
235 * determine the length of a string in romfs
236 */
romfs_dev_strnlen(struct super_block * sb,unsigned long pos,size_t maxlen)237 ssize_t romfs_dev_strnlen(struct super_block *sb,
238 unsigned long pos, size_t maxlen)
239 {
240 size_t limit;
241
242 limit = romfs_maxsize(sb);
243 if (pos >= limit)
244 return -EIO;
245 if (maxlen > limit - pos)
246 maxlen = limit - pos;
247
248 #ifdef CONFIG_ROMFS_ON_MTD
249 if (sb->s_mtd)
250 return romfs_mtd_strnlen(sb, pos, maxlen);
251 #endif
252 #ifdef CONFIG_ROMFS_ON_BLOCK
253 if (sb->s_bdev)
254 return romfs_blk_strnlen(sb, pos, maxlen);
255 #endif
256 return -EIO;
257 }
258
259 /*
260 * compare a string to one in romfs
261 * - the string to be compared to, str, may not be NUL-terminated; instead the
262 * string is of the specified size
263 * - return 1 if matched, 0 if differ, -ve if error
264 */
romfs_dev_strcmp(struct super_block * sb,unsigned long pos,const char * str,size_t size)265 int romfs_dev_strcmp(struct super_block *sb, unsigned long pos,
266 const char *str, size_t size)
267 {
268 size_t limit;
269
270 limit = romfs_maxsize(sb);
271 if (pos >= limit)
272 return -EIO;
273 if (size > ROMFS_MAXFN)
274 return -ENAMETOOLONG;
275 if (size + 1 > limit - pos)
276 return -EIO;
277
278 #ifdef CONFIG_ROMFS_ON_MTD
279 if (sb->s_mtd)
280 return romfs_mtd_strcmp(sb, pos, str, size);
281 #endif
282 #ifdef CONFIG_ROMFS_ON_BLOCK
283 if (sb->s_bdev)
284 return romfs_blk_strcmp(sb, pos, str, size);
285 #endif
286 return -EIO;
287 }
288