util-linux/mdev.c

/* 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.
 *
 * 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...]
 *
 * The device name or "subsystem/device" combo is matched against 1st field
 * (which is a regex), or maj,min is matched against 1st field.
 *
 * Leading minus in 1st field means "don't stop on this line", otherwise
 * search is stopped after the matching line is encountered.
 *
 * When line matches, the device node is created, chmod'ed and chown'ed.
 * Then it moved to path, and if >path, a symlink to moved node is created
 *    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.
 */

struct globals {
	int root_major, root_minor;
	char *subsystem;
};
#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

#if ENABLE_FEATURE_MDEV_RENAME
/* Builds an alias path.
 * This function potentionally reallocates the alias parameter.
 */
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;
}
#endif

/* mknod in /dev based on a path like "/sys/block/hda/hda1" */
/* NB: "mdev -s" may call us many times, do not leak memory/fds! */
static void make_device(char *path, int delete)
{
#if ENABLE_FEATURE_MDEV_CONF
	parser_t *parser;
#endif
	const char *device_name;
	int major, minor, type, len;
	int mode;
	char *dev_maj_min = path + strlen(path);

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

	/* 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) {
		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, so just try to run script */
			*dev_maj_min = '\0';
		} else if (sscanf(dev_maj_min, "%u:%u", &major, &minor) != 2) {
			major = -1;
		}
	}

	/* Determine device name, type, major and minor */
	device_name = 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 !ENABLE_FEATURE_MDEV_CONF
	mode = 0660;
#else
	/* If we have config file, look up user settings */
	parser = config_open2("/etc/mdev.conf", fopen_for_read);
	while (1) {
		regmatch_t off[1 + 9 * ENABLE_FEATURE_MDEV_RENAME_REGEXP];
		int keep_matching;
		char *val, *name;
		struct bb_uidgid_t ugid;
		char *tokens[4];
# if ENABLE_FEATURE_MDEV_EXEC
		char *command = NULL;
# endif
# if ENABLE_FEATURE_MDEV_RENAME
		char *alias = NULL;
		char aliaslink = aliaslink; /* for compiler */
# endif
		/* Defaults in case we won't match any line */
		ugid.uid = ugid.gid = 0;
		keep_matching = 0;
		mode = 0660;

		if (!config_read(parser, tokens, 4, 3, "# \t", PARSE_NORMAL)) {
			/* End of file, create dev node with default params */
			goto line_matches;
		}

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

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

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

		/* 1st field: @<numeric maj,min>... */
		if (val[0] == '@') {
			/* @major,minor[-last] */
			/* (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 */
			}
		} else { /* ... or regex to match device name */
			regex_t match;
			int result;

			/* Is this it? */
			xregcomp(&match, val, REG_EXTENDED);
			result = regexec(&match, name, 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 not this device, skip rest of line */
			/* (regexec returns whole pattern as "range" 0) */
			if (result || off[0].rm_so
			 || ((int)off[0].rm_eo != (int)strlen(name))
			) {
				continue; /* this line doesn't match */
			}
		}

		/* This line matches: stop parsing the file after parsing
		 * the rest of fields unless keep_matching == 1 */

		/* 2nd field: uid:gid - device ownership */
		parse_chown_usergroup_or_die(&ugid, tokens[1]);

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

		val = tokens[3];
		/* 4th field (opt): >|=alias */
# if ENABLE_FEATURE_MDEV_RENAME
		if (!val)
			goto line_matches;
		aliaslink = val[0];
		if (aliaslink == '>' || aliaslink == '=') {
			char *a, *s, *st;
#  if ENABLE_FEATURE_MDEV_RENAME_REGEXP
			char *p;
			unsigned i, n;
#  endif
			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(name));
			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, name + off[i].rm_so, n);
						p += n - 1;
						s++;
					}
				}
				p++;
				s++;
			}
#  else
			alias = xstrdup(a + 1);
#  endif
		}
# endif /* ENABLE_FEATURE_MDEV_RENAME */

# if ENABLE_FEATURE_MDEV_EXEC
		/* The rest (opt): @|$|*command */
		if (!val)
			goto line_matches;
		{
			const char *s = "@$*";
			const char *s2 = strchr(s, val[0]);

			if (!s2)
				bb_error_msg_and_die("bad line %u", parser->lineno);

			/* Correlate the position in the "@$*" with the delete
			 * step so that we get the proper behavior:
			 * @cmd: run on create
			 * $cmd: run on delete
			 * *cmd: run on both
			 */
			if ((s2 - s + 1) /*1/2/3*/ & /*1/2*/ (1 + delete)) {
				command = xstrdup(val + 1);
			}
		}
# endif
		/* End of field parsing */
 line_matches:
#endif /* ENABLE_FEATURE_MDEV_CONF */

		/* "Execute" the line we found */

		if (!delete && major >= 0) {
			if (ENABLE_FEATURE_MDEV_RENAME)
				unlink(device_name);
			if (mknod(device_name, mode | type, makedev(major, minor)) && errno != EEXIST)
				bb_perror_msg_and_die("mknod %s", device_name);
			if (major == root_major && minor == root_minor)
				symlink(device_name, "root");
#if ENABLE_FEATURE_MDEV_CONF
			chmod(device_name, mode);
			chown(device_name, ugid.uid, ugid.gid);
# if ENABLE_FEATURE_MDEV_RENAME
			if (alias) {
				alias = build_alias(alias, device_name);
				/* move the device, and optionally
				 * make a symlink to moved device node */
				if (rename(device_name, alias) == 0 && aliaslink == '>')
					symlink(alias, device_name);
				free(alias);
			}
# endif
#endif
		}
#if ENABLE_FEATURE_MDEV_EXEC
		if (command) {
			/* setenv will leak memory, use putenv/unsetenv/free */
			char *s = xasprintf("%s=%s", "MDEV", device_name);
			char *s1 = xasprintf("%s=%s", "SUBSYSTEM", subsystem);
			putenv(s);
			putenv(s1);
			if (system(command) == -1)
				bb_perror_msg_and_die("can't run '%s'", command);
			unsetenv("SUBSYSTEM");
			free(s1);
			unsetenv("MDEV");
			free(s);
			free(command);
		}
#endif
		if (delete) {
			unlink(device_name);
			/* At creation time, device might have been moved
			 * and a symlink might have been created. Undo that. */
#if ENABLE_FEATURE_MDEV_RENAME
			if (alias) {
				alias = build_alias(alias, device_name);
				unlink(alias);
				free(alias);
			}
#endif
		}

#if ENABLE_FEATURE_MDEV_CONF
		/* We found matching line.
		 * Stop unless it was prefixed with '-' */
		if (!keep_matching)
			break;
	} /* end of "while line is read from /etc/mdev.conf" */

	config_close(parser);
#endif /* ENABLE_FEATURE_MDEV_CONF */
}

/* 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 *const firmware, const char *const 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 */
#if 1
	bb_sanitize_stdio();
#else
	/* Debug code */
	/* Replace LOGFILE by other file or device name if you need */
#define LOGFILE "/dev/console"
	/* Just making sure fd 0 is not closed,
	 * we don't really intend to read from it */
	xmove_fd(xopen("/", O_RDONLY), STDIN_FILENO);
	xmove_fd(xopen(LOGFILE, O_WRONLY|O_APPEND), STDOUT_FILENO);
	xmove_fd(xopen(LOGFILE, O_WRONLY|O_APPEND), STDERR_FILENO);
#endif

	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;

		/* 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");

		/* 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 (strcmp(action, "remove") == 0) {
			/* Ignoring "remove firmware". It was reported
			 * to happen and to cause erroneous deletion
			 * of device nodes. */
			if (!fw)
				make_device(temp, 1);
		}
		else if (strcmp(action, "add") == 0) {
			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;
}