1 /*
2 * read.c - read the blkid cache from disk, to avoid scanning all devices
3 *
4 * Copyright (C) 2001, 2003 Theodore Y. Ts'o
5 * Copyright (C) 2001 Andreas Dilger
6 *
7 * %Begin-Header%
8 * This file may be redistributed under the terms of the
9 * GNU Lesser General Public License.
10 * %End-Header%
11 */
12
13
14 #include <stdio.h>
15 #include <ctype.h>
16 #include <string.h>
17 #include <time.h>
18 #include <sys/types.h>
19 #include <sys/stat.h>
20 #include <fcntl.h>
21 #include <unistd.h>
22 #ifdef HAVE_ERRNO_H
23 #include <errno.h>
24 #endif
25
26 #include "blkidP.h"
27
28 #ifdef HAVE_STDLIB_H
29 # ifndef _XOPEN_SOURCE
30 # define _XOPEN_SOURCE 600 /* for inclusion of strtoull */
31 # endif
32 # include <stdlib.h>
33 #endif
34
35 /*
36 * File format:
37 *
38 * <device [<NAME="value"> ...]>device_name</device>
39 *
40 * The following tags are required for each entry:
41 * <ID="id"> unique (within this file) ID number of this device
42 * <TIME="sec.usec"> (time_t and suseconds_t) time this entry was last
43 * read from disk
44 * <TYPE="type"> (detected) type of filesystem/data for this partition
45 *
46 * The following tags may be present, depending on the device contents
47 * <LABEL="label"> (user supplied) label (volume name, etc)
48 * <UUID="uuid"> (generated) universally unique identifier (serial no)
49 */
50
51 static char *skip_over_blank(char *cp)
52 {
53 while (*cp && isspace(*cp))
54 cp++;
55 return cp;
56 }
57
58 static char *skip_over_word(char *cp)
59 {
60 char ch;
61
62 while ((ch = *cp)) {
63 /* If we see a backslash, skip the next character */
64 if (ch == '\\') {
65 cp++;
66 if (*cp == '\0')
67 break;
68 cp++;
69 continue;
70 }
71 if (isspace(ch) || ch == '<' || ch == '>')
72 break;
73 cp++;
74 }
75 return cp;
76 }
77
78 static char *strip_line(char *line)
79 {
80 char *p;
81
82 line = skip_over_blank(line);
83
84 p = line + strlen(line) - 1;
85
86 while (*line) {
87 if (isspace(*p))
88 *p-- = '\0';
89 else
90 break;
91 }
92
93 return line;
94 }
95
96 #if 0
97 static char *parse_word(char **buf)
98 {
99 char *word, *next;
100
101 word = *buf;
102 if (*word == '\0')
103 return NULL;
104
105 word = skip_over_blank(word);
106 next = skip_over_word(word);
107 if (*next) {
108 char *end = next - 1;
109 if (*end == '"' || *end == '\'')
110 *end = '\0';
111 *next++ = '\0';
112 }
113 *buf = next;
114
115 if (*word == '"' || *word == '\'')
116 word++;
117 return word;
118 }
119 #endif
120
121 /*
122 * Start parsing a new line from the cache.
123 *
124 * line starts with "<device" return 1 -> continue parsing line
125 * line starts with "<foo", empty, or # return 0 -> skip line
126 * line starts with other, return -BLKID_ERR_CACHE -> error
127 */
128 static int parse_start(char **cp)
129 {
130 char *p;
131
132 p = strip_line(*cp);
133
134 /* Skip comment or blank lines. We can't just NUL the first '#' char,
135 * in case it is inside quotes, or escaped.
136 */
137 if (*p == '\0' || *p == '#')
138 return 0;
139
140 if (!strncmp(p, "<device", 7)) {
141 DBG(READ, ul_debug("found device header: %8s", p));
142 p += 7;
143
144 *cp = p;
145 return 1;
146 }
147
148 if (*p == '<')
149 return 0;
150
151 return -BLKID_ERR_CACHE;
152 }
153
154 /* Consume the remaining XML on the line (cosmetic only) */
155 static int parse_end(char **cp)
156 {
157 *cp = skip_over_blank(*cp);
158
159 if (!strncmp(*cp, "</device>", 9)) {
160 DBG(READ, ul_debug("found device trailer %9s", *cp));
161 *cp += 9;
162 return 0;
163 }
164
165 return -BLKID_ERR_CACHE;
166 }
167
168 /*
169 * Allocate a new device struct with device name filled in. Will handle
170 * finding the device on lines of the form:
171 * <device foo=bar>devname</device>
172 * <device>devname<foo>bar</foo></device>
173 */
174 static int parse_dev(blkid_cache cache, blkid_dev *dev, char **cp)
175 {
176 char *start, *tmp, *end, *name;
177 int ret;
178
179 if ((ret = parse_start(cp)) <= 0)
180 return ret;
181
182 start = tmp = strchr(*cp, '>');
183 if (!start) {
184 DBG(READ, ul_debug("blkid: short line parsing dev: %s", *cp));
185 return -BLKID_ERR_CACHE;
186 }
187 start = skip_over_blank(start + 1);
188 end = skip_over_word(start);
189
190 DBG(READ, ul_debug("device should be %*s",
191 (int)(end - start), start));
192
193 if (**cp == '>')
194 *cp = end;
195 else
196 (*cp)++;
197
198 *tmp = '\0';
199
200 if (!(tmp = strrchr(end, '<')) || parse_end(&tmp) < 0) {
201 DBG(READ, ul_debug("blkid: missing </device> ending: %s", end));
202 } else if (tmp)
203 *tmp = '\0';
204
205 if (end - start <= 1) {
206 DBG(READ, ul_debug("blkid: empty device name: %s", *cp));
207 return -BLKID_ERR_CACHE;
208 }
209
210 name = strndup(start, end - start);
211 if (name == NULL)
212 return -BLKID_ERR_MEM;
213
214 DBG(READ, ul_debug("found dev %s", name));
215
216 if (!(*dev = blkid_get_dev(cache, name, BLKID_DEV_CREATE))) {
217 free(name);
218 return -BLKID_ERR_MEM;
219 }
220
221 free(name);
222 return 1;
223 }
224
225 /*
226 * Extract a tag of the form NAME="value" from the line.
227 */
228 static int parse_token(char **name, char **value, char **cp)
229 {
230 char *end;
231
232 if (!name || !value || !cp)
233 return -BLKID_ERR_PARAM;
234
235 if (!(*value = strchr(*cp, '=')))
236 return 0;
237
238 **value = '\0';
239 *name = strip_line(*cp);
240 *value = skip_over_blank(*value + 1);
241
242 if (**value == '"') {
243 char *p = end = *value + 1;
244
245 /* convert 'foo\"bar' to 'foo"bar' */
246 while (*p) {
247 if (*p == '\\') {
248 p++;
249 *end = *p;
250 } else {
251 *end = *p;
252 if (*p == '"')
253 break;
254 }
255 p++;
256 end++;
257 }
258
259 if (*end != '"') {
260 DBG(READ, ul_debug("unbalanced quotes at: %s", *value));
261 *cp = *value;
262 return -BLKID_ERR_CACHE;
263 }
264 (*value)++;
265 *end = '\0';
266 end = ++p;
267 } else {
268 end = skip_over_word(*value);
269 if (*end) {
270 *end = '\0';
271 end++;
272 }
273 }
274 *cp = end;
275
276 return 1;
277 }
278
279 /*
280 * Extract a tag from the line.
281 *
282 * Return 1 if a valid tag was found.
283 * Return 0 if no tag found.
284 * Return -ve error code.
285 */
286 static int parse_tag(blkid_cache cache, blkid_dev dev, char **cp)
287 {
288 char *name = NULL;
289 char *value = NULL;
290 int ret;
291
292 if (!cache || !dev)
293 return -BLKID_ERR_PARAM;
294
295 if ((ret = parse_token(&name, &value, cp)) <= 0)
296 return ret;
297
298 DBG(READ, ul_debug("tag: %s=\"%s\"", name, value));
299
300 errno = 0;
301
302 /* Some tags are stored directly in the device struct */
303 if (!strcmp(name, "DEVNO")) {
304 dev->bid_devno = strtoull(value, NULL, 0);
305 if (errno)
306 return -errno;
307 } else if (!strcmp(name, "PRI")) {
308 dev->bid_pri = strtol(value, NULL, 0);
309 if (errno)
310 return -errno;
311 } else if (!strcmp(name, "TIME")) {
312 char *end = NULL;
313
314 dev->bid_time = strtoull(value, &end, 0);
315 if (errno == 0 && end && *end == '.')
316 dev->bid_utime = strtoull(end + 1, NULL, 0);
317 if (errno)
318 return -errno;
319 } else
320 ret = blkid_set_tag(dev, name, value, strlen(value));
321
322 return ret < 0 ? ret : 1;
323 }
324
325 /*
326 * Parse a single line of data, and return a newly allocated dev struct.
327 * Add the new device to the cache struct, if one was read.
328 *
329 * Lines are of the form <device [TAG="value" ...]>/dev/foo</device>
330 *
331 * Returns -ve value on error.
332 * Returns 0 otherwise.
333 * If a valid device was read, *dev_p is non-NULL, otherwise it is NULL
334 * (e.g. comment lines, unknown XML content, etc).
335 */
336 static int blkid_parse_line(blkid_cache cache, blkid_dev *dev_p, char *cp)
337 {
338 blkid_dev dev;
339 int ret;
340
341 if (!cache || !dev_p)
342 return -BLKID_ERR_PARAM;
343
344 *dev_p = NULL;
345
346 DBG(READ, ul_debug("line: %s", cp));
347
348 if ((ret = parse_dev(cache, dev_p, &cp)) <= 0)
349 return ret;
350
351 dev = *dev_p;
352
353 while ((ret = parse_tag(cache, dev, &cp)) > 0) {
354 ;
355 }
356
357 if (dev->bid_type == NULL) {
358 DBG(READ, ul_debug("blkid: device %s has no TYPE",dev->bid_name));
359 blkid_free_dev(dev);
360 goto done;
361 }
362
363 done:
364 return ret;
365 }
366
367 /*
368 * Parse the specified filename, and return the data in the supplied or
369 * a newly allocated cache struct. If the file doesn't exist, return a
370 * new empty cache struct.
371 */
372 void blkid_read_cache(blkid_cache cache)
373 {
374 FILE *file;
375 char buf[4096];
376 int fd, lineno = 0;
377 struct stat st;
378
379 /*
380 * If the file doesn't exist, then we just return an empty
381 * struct so that the cache can be populated.
382 */
383 if ((fd = open(cache->bic_filename, O_RDONLY|O_CLOEXEC)) < 0)
384 return;
385 if (fstat(fd, &st) < 0)
386 goto errout;
387 if ((st.st_mtime == cache->bic_ftime) ||
388 (cache->bic_flags & BLKID_BIC_FL_CHANGED)) {
389 DBG(CACHE, ul_debug("skipping re-read of %s",
390 cache->bic_filename));
391 goto errout;
392 }
393
394 DBG(CACHE, ul_debug("reading cache file %s",
395 cache->bic_filename));
396
397 file = fdopen(fd, "r" UL_CLOEXECSTR);
398 if (!file)
399 goto errout;
400
401 while (fgets(buf, sizeof(buf), file)) {
402 blkid_dev dev;
403 unsigned int end;
404
405 lineno++;
406 if (buf[0] == 0)
407 continue;
408 end = strlen(buf) - 1;
409 /* Continue reading next line if it ends with a backslash */
410 while (end < (sizeof(buf) - 2) && buf[end] == '\\' &&
411 fgets(buf + end, sizeof(buf) - end, file)) {
412 end = strlen(buf) - 1;
413 lineno++;
414 }
415
416 if (blkid_parse_line(cache, &dev, buf) < 0) {
417 DBG(READ, ul_debug("blkid: bad format on line %d", lineno));
418 continue;
419 }
420 }
421 fclose(file);
422
423 /*
424 * Initially we do not need to write out the cache file.
425 */
426 cache->bic_flags &= ~BLKID_BIC_FL_CHANGED;
427 cache->bic_ftime = st.st_mtime;
428
429 return;
430 errout:
431 close(fd);
432 }
433
434 #ifdef TEST_PROGRAM
435
436 int main(int argc, char**argv)
437 {
438 blkid_cache cache = NULL;
439 int ret;
440
441 blkid_init_debug(BLKID_DEBUG_ALL);
442 if (argc > 2) {
443 fprintf(stderr, "Usage: %s [filename]\n"
444 "Test parsing of the cache (filename)\n", argv[0]);
445 exit(1);
446 }
447 if ((ret = blkid_get_cache(&cache, argv[1])) < 0)
448 fprintf(stderr, "error %d reading cache file %s\n", ret,
449 argv[1] ? argv[1] : blkid_get_cache_filename(NULL));
450
451 blkid_put_cache(cache);
452
453 return ret;
454 }
455 #endif