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David Howellsda4458b2009-02-12 10:40:10 +00001/* RomFS storage access routines
2 *
3 * Copyright © 2007 Red Hat, Inc. All Rights Reserved.
4 * Written by David Howells (dhowells@redhat.com)
5 *
6 * This program is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU General Public License
8 * as published by the Free Software Foundation; either version
9 * 2 of the License, or (at your option) any later version.
10 */
11
12#include <linux/fs.h>
13#include <linux/mtd/super.h>
14#include <linux/buffer_head.h>
15#include "internal.h"
16
17#if !defined(CONFIG_ROMFS_ON_MTD) && !defined(CONFIG_ROMFS_ON_BLOCK)
18#error no ROMFS backing store interface configured
19#endif
20
21#ifdef CONFIG_ROMFS_ON_MTD
22#define ROMFS_MTD_READ(sb, ...) ((sb)->s_mtd->read((sb)->s_mtd, ##__VA_ARGS__))
23
24/*
25 * read data from an romfs image on an MTD device
26 */
27static int romfs_mtd_read(struct super_block *sb, unsigned long pos,
28 void *buf, size_t buflen)
29{
30 size_t rlen;
31 int ret;
32
33 ret = ROMFS_MTD_READ(sb, pos, buflen, &rlen, buf);
34 return (ret < 0 || rlen != buflen) ? -EIO : 0;
35}
36
37/*
38 * determine the length of a string in a romfs image on an MTD device
39 */
40static ssize_t romfs_mtd_strnlen(struct super_block *sb,
41 unsigned long pos, size_t maxlen)
42{
43 ssize_t n = 0;
44 size_t segment;
45 u_char buf[16], *p;
46 size_t len;
47 int ret;
48
49 /* scan the string up to 16 bytes at a time */
50 while (maxlen > 0) {
51 segment = min_t(size_t, maxlen, 16);
52 ret = ROMFS_MTD_READ(sb, pos, segment, &len, buf);
53 if (ret < 0)
54 return ret;
55 p = memchr(buf, 0, len);
56 if (p)
57 return n + (p - buf);
58 maxlen -= len;
59 pos += len;
60 n += len;
61 }
62
63 return n;
64}
65
66/*
67 * compare a string to one in a romfs image on MTD
68 * - return 1 if matched, 0 if differ, -ve if error
69 */
David Howells84baf742009-04-23 16:41:13 +010070static int romfs_mtd_strcmp(struct super_block *sb, unsigned long pos,
71 const char *str, size_t size)
David Howellsda4458b2009-02-12 10:40:10 +000072{
David Howells84baf742009-04-23 16:41:13 +010073 u_char buf[17];
David Howellsda4458b2009-02-12 10:40:10 +000074 size_t len, segment;
75 int ret;
76
David Howells84baf742009-04-23 16:41:13 +010077 /* scan the string up to 16 bytes at a time, and attempt to grab the
78 * trailing NUL whilst we're at it */
79 buf[0] = 0xff;
80
David Howellsda4458b2009-02-12 10:40:10 +000081 while (size > 0) {
David Howells84baf742009-04-23 16:41:13 +010082 segment = min_t(size_t, size + 1, 17);
David Howellsda4458b2009-02-12 10:40:10 +000083 ret = ROMFS_MTD_READ(sb, pos, segment, &len, buf);
84 if (ret < 0)
85 return ret;
David Howells84baf742009-04-23 16:41:13 +010086 len--;
David Howellsda4458b2009-02-12 10:40:10 +000087 if (memcmp(buf, str, len) != 0)
88 return 0;
David Howells84baf742009-04-23 16:41:13 +010089 buf[0] = buf[len];
David Howellsda4458b2009-02-12 10:40:10 +000090 size -= len;
91 pos += len;
92 str += len;
93 }
94
David Howells84baf742009-04-23 16:41:13 +010095 /* check the trailing NUL was */
96 if (buf[0])
97 return 0;
98
David Howellsda4458b2009-02-12 10:40:10 +000099 return 1;
100}
101#endif /* CONFIG_ROMFS_ON_MTD */
102
103#ifdef CONFIG_ROMFS_ON_BLOCK
104/*
105 * read data from an romfs image on a block device
106 */
107static int romfs_blk_read(struct super_block *sb, unsigned long pos,
108 void *buf, size_t buflen)
109{
110 struct buffer_head *bh;
111 unsigned long offset;
112 size_t segment;
113
114 /* copy the string up to blocksize bytes at a time */
115 while (buflen > 0) {
116 offset = pos & (ROMBSIZE - 1);
117 segment = min_t(size_t, buflen, ROMBSIZE - offset);
118 bh = sb_bread(sb, pos >> ROMBSBITS);
119 if (!bh)
120 return -EIO;
121 memcpy(buf, bh->b_data + offset, segment);
122 brelse(bh);
123 buflen -= segment;
124 pos += segment;
125 }
126
127 return 0;
128}
129
130/*
131 * determine the length of a string in romfs on a block device
132 */
133static ssize_t romfs_blk_strnlen(struct super_block *sb,
134 unsigned long pos, size_t limit)
135{
136 struct buffer_head *bh;
137 unsigned long offset;
138 ssize_t n = 0;
139 size_t segment;
140 u_char *buf, *p;
141
142 /* scan the string up to blocksize bytes at a time */
143 while (limit > 0) {
144 offset = pos & (ROMBSIZE - 1);
145 segment = min_t(size_t, limit, ROMBSIZE - offset);
146 bh = sb_bread(sb, pos >> ROMBSBITS);
147 if (!bh)
148 return -EIO;
149 buf = bh->b_data + offset;
150 p = memchr(buf, 0, segment);
151 brelse(bh);
152 if (p)
153 return n + (p - buf);
154 limit -= segment;
155 pos += segment;
156 n += segment;
157 }
158
159 return n;
160}
161
162/*
163 * compare a string to one in a romfs image on a block device
164 * - return 1 if matched, 0 if differ, -ve if error
165 */
David Howells84baf742009-04-23 16:41:13 +0100166static int romfs_blk_strcmp(struct super_block *sb, unsigned long pos,
167 const char *str, size_t size)
David Howellsda4458b2009-02-12 10:40:10 +0000168{
169 struct buffer_head *bh;
170 unsigned long offset;
171 size_t segment;
David Howells84baf742009-04-23 16:41:13 +0100172 bool matched, terminated = false;
David Howellsda4458b2009-02-12 10:40:10 +0000173
David Howells84baf742009-04-23 16:41:13 +0100174 /* compare string up to a block at a time */
David Howellsda4458b2009-02-12 10:40:10 +0000175 while (size > 0) {
176 offset = pos & (ROMBSIZE - 1);
177 segment = min_t(size_t, size, ROMBSIZE - offset);
178 bh = sb_bread(sb, pos >> ROMBSBITS);
179 if (!bh)
180 return -EIO;
David Howells84baf742009-04-23 16:41:13 +0100181 matched = (memcmp(bh->b_data + offset, str, segment) == 0);
182
David Howellsda4458b2009-02-12 10:40:10 +0000183 size -= segment;
184 pos += segment;
185 str += segment;
David Howells84baf742009-04-23 16:41:13 +0100186 if (matched && size == 0 && offset + segment < ROMBSIZE) {
187 if (!bh->b_data[offset + segment])
188 terminated = true;
189 else
190 matched = false;
191 }
192 brelse(bh);
193 if (!matched)
194 return 0;
195 }
196
197 if (!terminated) {
198 /* the terminating NUL must be on the first byte of the next
199 * block */
200 BUG_ON((pos & (ROMBSIZE - 1)) != 0);
201 bh = sb_bread(sb, pos >> ROMBSBITS);
202 if (!bh)
203 return -EIO;
204 matched = !bh->b_data[0];
205 brelse(bh);
206 if (!matched)
207 return 0;
David Howellsda4458b2009-02-12 10:40:10 +0000208 }
209
210 return 1;
211}
212#endif /* CONFIG_ROMFS_ON_BLOCK */
213
214/*
215 * read data from the romfs image
216 */
217int romfs_dev_read(struct super_block *sb, unsigned long pos,
218 void *buf, size_t buflen)
219{
220 size_t limit;
221
222 limit = romfs_maxsize(sb);
223 if (pos >= limit)
224 return -EIO;
225 if (buflen > limit - pos)
226 buflen = limit - pos;
227
228#ifdef CONFIG_ROMFS_ON_MTD
229 if (sb->s_mtd)
230 return romfs_mtd_read(sb, pos, buf, buflen);
231#endif
232#ifdef CONFIG_ROMFS_ON_BLOCK
233 if (sb->s_bdev)
234 return romfs_blk_read(sb, pos, buf, buflen);
235#endif
236 return -EIO;
237}
238
239/*
240 * determine the length of a string in romfs
241 */
242ssize_t romfs_dev_strnlen(struct super_block *sb,
243 unsigned long pos, size_t maxlen)
244{
245 size_t limit;
246
247 limit = romfs_maxsize(sb);
248 if (pos >= limit)
249 return -EIO;
250 if (maxlen > limit - pos)
251 maxlen = limit - pos;
252
253#ifdef CONFIG_ROMFS_ON_MTD
254 if (sb->s_mtd)
255 return romfs_mtd_strnlen(sb, pos, limit);
256#endif
257#ifdef CONFIG_ROMFS_ON_BLOCK
258 if (sb->s_bdev)
259 return romfs_blk_strnlen(sb, pos, limit);
260#endif
261 return -EIO;
262}
263
264/*
265 * compare a string to one in romfs
David Howells84baf742009-04-23 16:41:13 +0100266 * - the string to be compared to, str, may not be NUL-terminated; instead the
267 * string is of the specified size
David Howellsda4458b2009-02-12 10:40:10 +0000268 * - return 1 if matched, 0 if differ, -ve if error
269 */
David Howells84baf742009-04-23 16:41:13 +0100270int romfs_dev_strcmp(struct super_block *sb, unsigned long pos,
271 const char *str, size_t size)
David Howellsda4458b2009-02-12 10:40:10 +0000272{
273 size_t limit;
274
275 limit = romfs_maxsize(sb);
276 if (pos >= limit)
277 return -EIO;
278 if (size > ROMFS_MAXFN)
279 return -ENAMETOOLONG;
David Howells84baf742009-04-23 16:41:13 +0100280 if (size + 1 > limit - pos)
David Howellsda4458b2009-02-12 10:40:10 +0000281 return -EIO;
282
283#ifdef CONFIG_ROMFS_ON_MTD
284 if (sb->s_mtd)
David Howells84baf742009-04-23 16:41:13 +0100285 return romfs_mtd_strcmp(sb, pos, str, size);
David Howellsda4458b2009-02-12 10:40:10 +0000286#endif
287#ifdef CONFIG_ROMFS_ON_BLOCK
288 if (sb->s_bdev)
David Howells84baf742009-04-23 16:41:13 +0100289 return romfs_blk_strcmp(sb, pos, str, size);
David Howellsda4458b2009-02-12 10:40:10 +0000290#endif
291 return -EIO;
292}