aboutsummaryrefslogtreecommitdiff
path: root/util-linux/mdev.c
blob: 69e1e6937bd3949d14e780a0bd45aee5eeff16c7 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
/* vi: set sw=4 ts=4: */
/*
 * mdev - Mini udev for busybox
 *
 * Copyright 2005 Rob Landley <rob@landley.net>
 * Copyright 2005 Frank Sorenson <frank@tuxrocks.com>
 *
 * Licensed under GPL version 2, see file LICENSE in this tarball for details.
 */
#include "libbb.h"
#include "xregex.h"

/* "mdev -s" scans /sys/class/xxx, looking for directories which have dev
 * file (it is of the form "M:m\n"). Example: /sys/class/tty/tty0/dev
 * contains "4:0\n". Directory name is taken as device name, path component
 * directly after /sys/class/ as subsystem. In this example, "tty0" and "tty".
 * Then mdev creates the /dev/device_name node.
 * If /sys/class/.../dev file does not exist, mdev still may act
 * on this device: see "@|$|*command args..." parameter in config file.
 *
 * mdev w/o parameters is called as hotplug helper. It takes device
 * and subsystem names from $DEVPATH and $SUBSYSTEM, extracts
 * maj,min from "/sys/$DEVPATH/dev" and also examines
 * $ACTION ("add"/"delete") and $FIRMWARE.
 *
 * If action is "add", mdev creates /dev/device_name similarly to mdev -s.
 * (todo: explain "delete" and $FIRMWARE)
 *
 * If /etc/mdev.conf exists, it may modify /dev/device_name's properties.
 * /etc/mdev.conf file format:
 *
 * [-][subsystem/]device  user:grp  mode  [>|=path] [@|$|*command args...]
 * [-]@maj,min[-min2]     user:grp  mode  [>|=path] [@|$|*command args...]
 * [-]$envvar=val         user:grp  mode  [>|=path] [@|$|*command args...]
 *
 * Leading minus in 1st field means "don't stop on this line", otherwise
 * search is stopped after the matching line is encountered.
 *
 * The device name or "subsystem/device" combo is matched against 1st field
 * (which is a regex), or maj,min is matched against 1st field,
 * or specified environment variable (as regex) is matched against 1st field.
 *
 * $envvar=val format is useful for loading modules for hot-plugged devices
 * which do not have driver loaded yet. In this case /sys/class/.../dev
 * does not exist, but $MODALIAS is set to needed module's name
 * (actually, an alias to it) by kernel. This rule instructs mdev
 * to load the module and exit:
 *    $MODALIAS=.* 0:0 660 @modprobe "$MODALIAS"
 * The kernel will generate another hotplug event when /sys/class/.../dev
 * file appears.
 *
 * When line matches, the device node is created, chmod'ed and chown'ed,
 * moved to path, and if >path, a symlink to moved node is created,
 * all this if /sys/class/.../dev exists.
 *    Examples:
 *    =loop/      - moves to /dev/loop
 *    >disk/sda%1 - moves to /dev/disk/sdaN, makes /dev/sdaN a symlink
 *
 * Then "command args..." is executed (via sh -c 'command args...').
 * @:execute on creation, $:on deletion, *:on both.
 * This happens regardless of /sys/class/.../dev existence.
 */

struct globals {
	int root_major, root_minor;
	char *subsystem;
} FIX_ALIASING;
#define G (*(struct globals*)&bb_common_bufsiz1)
#define root_major (G.root_major)
#define root_minor (G.root_minor)
#define subsystem  (G.subsystem )

/* Prevent infinite loops in /sys symlinks */
#define MAX_SYSFS_DEPTH 3

/* We use additional 64+ bytes in make_device() */
#define SCRATCH_SIZE 80

/* Builds an alias path.
 * This function potentionally reallocates the alias parameter.
 * Only used for ENABLE_FEATURE_MDEV_RENAME
 */
static char *build_alias(char *alias, const char *device_name)
{
	char *dest;

	/* ">bar/": rename to bar/device_name */
	/* ">bar[/]baz": rename to bar[/]baz */
	dest = strrchr(alias, '/');
	if (dest) { /* ">bar/[baz]" ? */
		*dest = '\0'; /* mkdir bar */
		bb_make_directory(alias, 0755, FILEUTILS_RECUR);
		*dest = '/';
		if (dest[1] == '\0') { /* ">bar/" => ">bar/device_name" */
			dest = alias;
			alias = concat_path_file(alias, device_name);
			free(dest);
		}
	}

	return alias;
}

/* mknod in /dev based on a path like "/sys/block/hda/hda1"
 * NB1: path parameter needs to have SCRATCH_SIZE scratch bytes
 * after NUL, but we promise to not mangle (IOW: to restore if needed)
 * path string.
 * NB2: "mdev -s" may call us many times, do not leak memory/fds!
 */
static void make_device(char *path, int delete)
{
	char *device_name;
	int major, minor, type, len;
	mode_t mode;
	parser_t *parser;

	/* Try to read major/minor string.  Note that the kernel puts \n after
	 * the data, so we don't need to worry about null terminating the string
	 * because sscanf() will stop at the first nondigit, which \n is.
	 * We also depend on path having writeable space after it.
	 */
	major = -1;
	if (!delete) {
		char *dev_maj_min = path + strlen(path);

		strcpy(dev_maj_min, "/dev");
		len = open_read_close(path, dev_maj_min + 1, 64);
		*dev_maj_min = '\0';
		if (len < 1) {
			if (!ENABLE_FEATURE_MDEV_EXEC)
				return;
			/* no "dev" file, but we can still run scripts
			 * based on device name */
		} else if (sscanf(++dev_maj_min, "%u:%u", &major, &minor) != 2) {
			major = -1;
		}
	}

	/* Determine device name, type, major and minor */
	device_name = (char*) bb_basename(path);
	/* http://kernel.org/doc/pending/hotplug.txt says that only
	 * "/sys/block/..." is for block devices. "/sys/bus" etc is not.
	 * But since 2.6.25 block devices are also in /sys/class/block,
	 * we use strstr("/block/") to forestall future surprises. */
	type = S_IFCHR;
	if (strstr(path, "/block/"))
		type = S_IFBLK;

	/* Make path point to "subsystem/device_name" */
	if (path[5] == 'b') /* legacy /sys/block? */
		path += sizeof("/sys/") - 1;
	else
		path += sizeof("/sys/class/") - 1;

	/* If we have config file, look up user settings */
	if (ENABLE_FEATURE_MDEV_CONF)
		parser = config_open2("/etc/mdev.conf", fopen_for_read);

	do {
		int keep_matching;
		struct bb_uidgid_t ugid;
		char *tokens[4];
		char *command = NULL;
		char *alias = NULL;
		char aliaslink = aliaslink; /* for compiler */

		/* Defaults in case we won't match any line */
		ugid.uid = ugid.gid = 0;
		keep_matching = 0;
		mode = 0660;

		if (ENABLE_FEATURE_MDEV_CONF
		 && config_read(parser, tokens, 4, 3, "# \t", PARSE_NORMAL)
		) {
			char *val;
			char *str_to_match;
			regmatch_t off[1 + 9 * ENABLE_FEATURE_MDEV_RENAME_REGEXP];

			val = tokens[0];
			keep_matching = ('-' == val[0]);
			val += keep_matching; /* swallow leading dash */

			/* Match against either "subsystem/device_name"
			 * or "device_name" alone */
			str_to_match = strchr(val, '/') ? path : device_name;

			/* Fields: regex uid:gid mode [alias] [cmd] */

			if (val[0] == '@') {
				/* @major,minor[-minor2] */
				/* (useful when name is ambiguous:
				 * "/sys/class/usb/lp0" and
				 * "/sys/class/printer/lp0") */
				int cmaj, cmin0, cmin1, sc;
				if (major < 0)
					continue; /* no dev, no match */
				sc = sscanf(val, "@%u,%u-%u", &cmaj, &cmin0, &cmin1);
				if (sc < 1 || major != cmaj
				 || (sc == 2 && minor != cmin0)
				 || (sc == 3 && (minor < cmin0 || minor > cmin1))
				) {
					continue; /* this line doesn't match */
				}
				goto line_matches;
			}
			if (val[0] == '$') {
				/* regex to match an environment variable */
				char *eq = strchr(++val, '=');
				if (!eq)
					continue;
				*eq = '\0';
				str_to_match = getenv(val);
				if (!str_to_match)
					continue;
				str_to_match -= strlen(val) + 1;
				*eq = '=';
			}
			/* else: regex to match [subsystem/]device_name */

			{
				regex_t match;
				int result;

				xregcomp(&match, val, REG_EXTENDED);
				result = regexec(&match, str_to_match, ARRAY_SIZE(off), off, 0);
				regfree(&match);
				//bb_error_msg("matches:");
				//for (int i = 0; i < ARRAY_SIZE(off); i++) {
				//	if (off[i].rm_so < 0) continue;
				//	bb_error_msg("match %d: '%.*s'\n", i,
				//		(int)(off[i].rm_eo - off[i].rm_so),
				//		device_name + off[i].rm_so);
				//}

				/* If no match, skip rest of line */
				/* (regexec returns whole pattern as "range" 0) */
				if (result || off[0].rm_so
				 || ((int)off[0].rm_eo != (int)strlen(str_to_match))
				) {
					continue; /* this line doesn't match */
				}
			}
 line_matches:
			/* This line matches. Stop parsing after parsing
			 * the rest the line unless keep_matching == 1 */

			/* 2nd field: uid:gid - device ownership */
			if (get_uidgid(&ugid, tokens[1], 1) == 0)
				bb_error_msg("unknown user/group %s on line %d", tokens[1], parser->lineno);

			/* 3rd field: mode - device permissions */
			/* mode = strtoul(tokens[2], NULL, 8); */
			bb_parse_mode(tokens[2], &mode);

			val = tokens[3];
			/* 4th field (opt): >|=alias */

			if (ENABLE_FEATURE_MDEV_RENAME && val) {
				aliaslink = val[0];
				if (aliaslink == '>' || aliaslink == '=') {
					char *a, *s, *st;
					char *p;
					unsigned i, n;

					a = val;
					s = strchrnul(val, ' ');
					st = strchrnul(val, '\t');
					if (st < s)
						s = st;
					val = (s[0] && s[1]) ? s+1 : NULL;
					s[0] = '\0';

					if (ENABLE_FEATURE_MDEV_RENAME_REGEXP) {
						/* substitute %1..9 with off[1..9], if any */
						n = 0;
						s = a;
						while (*s)
							if (*s++ == '%')
								n++;

						p = alias = xzalloc(strlen(a) + n * strlen(str_to_match));
						s = a + 1;
						while (*s) {
							*p = *s;
							if ('%' == *s) {
								i = (s[1] - '0');
								if (i <= 9 && off[i].rm_so >= 0) {
									n = off[i].rm_eo - off[i].rm_so;
									strncpy(p, str_to_match + off[i].rm_so, n);
									p += n - 1;
									s++;
								}
							}
							p++;
							s++;
						}
					} else {
						alias = xstrdup(a + 1);
					}
				}
			}

			if (ENABLE_FEATURE_MDEV_EXEC && val) {
				const char *s = "$@*";
				const char *s2 = strchr(s, val[0]);

				if (!s2) {
					bb_error_msg("bad line %u", parser->lineno);
					if (ENABLE_FEATURE_MDEV_RENAME)
						free(alias);
					continue;
				}

				/* Are we running this command now?
				 * Run $cmd on delete, @cmd on create, *cmd on both
				 */
				if (s2-s != delete)
					command = xstrdup(val + 1);
			}
		}

		/* End of field parsing */

		/* "Execute" the line we found */
		{
			const char *node_name;

			node_name = device_name;
			if (ENABLE_FEATURE_MDEV_RENAME && alias)
				node_name = alias = build_alias(alias, device_name);

			if (!delete && major >= 0) {
				if (mknod(node_name, mode | type, makedev(major, minor)) && errno != EEXIST)
					bb_perror_msg("can't create %s", node_name);
				if (major == root_major && minor == root_minor)
					symlink(node_name, "root");
				if (ENABLE_FEATURE_MDEV_CONF) {
					chmod(node_name, mode);
					chown(node_name, ugid.uid, ugid.gid);
				}
				if (ENABLE_FEATURE_MDEV_RENAME && alias) {
					if (aliaslink == '>')
						symlink(node_name, device_name);
				}
			}

			if (ENABLE_FEATURE_MDEV_EXEC && command) {
				/* setenv will leak memory, use putenv/unsetenv/free */
				char *s = xasprintf("%s=%s", "MDEV", node_name);
				char *s1 = xasprintf("%s=%s", "SUBSYSTEM", subsystem);
				putenv(s);
				putenv(s1);
				if (system(command) == -1)
					bb_perror_msg("can't run '%s'", command);
				unsetenv("SUBSYSTEM");
				free(s1);
				unsetenv("MDEV");
				free(s);
				free(command);
			}

			if (delete) {
				if (ENABLE_FEATURE_MDEV_RENAME && alias) {
					if (aliaslink == '>')
						unlink(device_name);
				}
				unlink(node_name);
			}

			if (ENABLE_FEATURE_MDEV_RENAME)
				free(alias);
		}

		/* We found matching line.
		 * Stop unless it was prefixed with '-' */
		if (ENABLE_FEATURE_MDEV_CONF && !keep_matching)
			break;

	/* end of "while line is read from /etc/mdev.conf" */
	} while (ENABLE_FEATURE_MDEV_CONF);

	if (ENABLE_FEATURE_MDEV_CONF)
		config_close(parser);
}

/* File callback for /sys/ traversal */
static int FAST_FUNC fileAction(const char *fileName,
		struct stat *statbuf UNUSED_PARAM,
		void *userData,
		int depth UNUSED_PARAM)
{
	size_t len = strlen(fileName) - 4; /* can't underflow */
	char *scratch = userData;

	/* len check is for paranoid reasons */
	if (strcmp(fileName + len, "/dev") != 0 || len >= PATH_MAX)
		return FALSE;

	strcpy(scratch, fileName);
	scratch[len] = '\0';
	make_device(scratch, 0);

	return TRUE;
}

/* Directory callback for /sys/ traversal */
static int FAST_FUNC dirAction(const char *fileName UNUSED_PARAM,
		struct stat *statbuf UNUSED_PARAM,
		void *userData UNUSED_PARAM,
		int depth)
{
	/* Extract device subsystem -- the name of the directory
	 * under /sys/class/ */
	if (1 == depth) {
		free(subsystem);
		subsystem = strrchr(fileName, '/');
		if (subsystem)
			subsystem = xstrdup(subsystem + 1);
	}

	return (depth >= MAX_SYSFS_DEPTH ? SKIP : TRUE);
}

/* For the full gory details, see linux/Documentation/firmware_class/README
 *
 * Firmware loading works like this:
 * - kernel sets FIRMWARE env var
 * - userspace checks /lib/firmware/$FIRMWARE
 * - userspace waits for /sys/$DEVPATH/loading to appear
 * - userspace writes "1" to /sys/$DEVPATH/loading
 * - userspace copies /lib/firmware/$FIRMWARE into /sys/$DEVPATH/data
 * - userspace writes "0" (worked) or "-1" (failed) to /sys/$DEVPATH/loading
 * - kernel loads firmware into device
 */
static void load_firmware(const char *firmware, const char *sysfs_path)
{
	int cnt;
	int firmware_fd, loading_fd, data_fd;

	/* check for /lib/firmware/$FIRMWARE */
	xchdir("/lib/firmware");
	firmware_fd = xopen(firmware, O_RDONLY);

	/* in case we goto out ... */
	data_fd = -1;

	/* check for /sys/$DEVPATH/loading ... give 30 seconds to appear */
	xchdir(sysfs_path);
	for (cnt = 0; cnt < 30; ++cnt) {
		loading_fd = open("loading", O_WRONLY);
		if (loading_fd != -1)
			goto loading;
		sleep(1);
	}
	goto out;

 loading:
	/* tell kernel we're loading by "echo 1 > /sys/$DEVPATH/loading" */
	if (full_write(loading_fd, "1", 1) != 1)
		goto out;

	/* load firmware into /sys/$DEVPATH/data */
	data_fd = open("data", O_WRONLY);
	if (data_fd == -1)
		goto out;
	cnt = bb_copyfd_eof(firmware_fd, data_fd);

	/* tell kernel result by "echo [0|-1] > /sys/$DEVPATH/loading" */
	if (cnt > 0)
		full_write(loading_fd, "0", 1);
	else
		full_write(loading_fd, "-1", 2);

 out:
	if (ENABLE_FEATURE_CLEAN_UP) {
		close(firmware_fd);
		close(loading_fd);
		close(data_fd);
	}
}

int mdev_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int mdev_main(int argc UNUSED_PARAM, char **argv)
{
	RESERVE_CONFIG_BUFFER(temp, PATH_MAX + SCRATCH_SIZE);

	/* We can be called as hotplug helper */
	/* Kernel cannot provide suitable stdio fds for us, do it ourself */
	bb_sanitize_stdio();

	/* Force the configuration file settings exactly */
	umask(0);

	xchdir("/dev");

	if (argv[1] && strcmp(argv[1], "-s") == 0) {
		/* Scan:
		 * mdev -s
		 */
		struct stat st;

		xstat("/", &st);
		root_major = major(st.st_dev);
		root_minor = minor(st.st_dev);

		/* ACTION_FOLLOWLINKS is needed since in newer kernels
		 * /sys/block/loop* (for example) are symlinks to dirs,
		 * not real directories.
		 * (kernel's CONFIG_SYSFS_DEPRECATED makes them real dirs,
		 * but we can't enforce that on users)
		 */
		if (access("/sys/class/block", F_OK) != 0) {
			/* Scan obsolete /sys/block only if /sys/class/block
			 * doesn't exist. Otherwise we'll have dupes.
			 * Also, do not complain if it doesn't exist.
			 * Some people configure kernel to have no blockdevs.
			 */
			recursive_action("/sys/block",
				ACTION_RECURSE | ACTION_FOLLOWLINKS | ACTION_QUIET,
				fileAction, dirAction, temp, 0);
		}
		recursive_action("/sys/class",
			ACTION_RECURSE | ACTION_FOLLOWLINKS,
			fileAction, dirAction, temp, 0);
	} else {
		char *fw;
		char *seq;
		char *action;
		char *env_path;
		static const char keywords[] ALIGN1 = "remove\0add\0";
		enum { OP_remove = 0, OP_add };
		smalluint op;

		/* Hotplug:
		 * env ACTION=... DEVPATH=... SUBSYSTEM=... [SEQNUM=...] mdev
		 * ACTION can be "add" or "remove"
		 * DEVPATH is like "/block/sda" or "/class/input/mice"
		 */
		action = getenv("ACTION");
		env_path = getenv("DEVPATH");
		subsystem = getenv("SUBSYSTEM");
		if (!action || !env_path /*|| !subsystem*/)
			bb_show_usage();
		fw = getenv("FIRMWARE");
		op = index_in_strings(keywords, action);
		/* If it exists, does /dev/mdev.seq match $SEQNUM?
		 * If it does not match, earlier mdev is running
		 * in parallel, and we need to wait */
		seq = getenv("SEQNUM");
		if (seq) {
			int timeout = 2000 / 32; /* 2000 msec */
			do {
				int seqlen;
				char seqbuf[sizeof(int)*3 + 2];

				seqlen = open_read_close("mdev.seq", seqbuf, sizeof(seqbuf-1));
				if (seqlen < 0) {
					seq = NULL;
					break;
				}
				seqbuf[seqlen] = '\0';
				if (seqbuf[0] == '\n' /* seed file? */
				 || strcmp(seq, seqbuf) == 0 /* correct idx? */
				) {
					break;
				}
				usleep(32*1000);
			} while (--timeout);
		}

		snprintf(temp, PATH_MAX, "/sys%s", env_path);
		if (op == OP_remove) {
			/* Ignoring "remove firmware". It was reported
			 * to happen and to cause erroneous deletion
			 * of device nodes. */
			if (!fw)
				make_device(temp, 1);
		}
		else if (op == OP_add) {
			make_device(temp, 0);
			if (ENABLE_FEATURE_MDEV_LOAD_FIRMWARE) {
				if (fw)
					load_firmware(fw, temp);
			}
		}

		if (seq) {
			xopen_xwrite_close("mdev.seq", utoa(xatou(seq) + 1));
		}
	}

	if (ENABLE_FEATURE_CLEAN_UP)
		RELEASE_CONFIG_BUFFER(temp);

	return EXIT_SUCCESS;
}