util-linux/mdev.c

   1 /* vi: set sw=4 ts=4: */
   2 /*
   3  * mdev - Mini udev for busybox
   4  *
   5  * Copyright 2005 Rob Landley <rob@landley.net>
   6  * Copyright 2005 Frank Sorenson <frank@tuxrocks.com>
   7  *
   8  * Licensed under GPL version 2, see file LICENSE in this tarball for details.
   9  */
  10 #include "libbb.h"
  11 #include "xregex.h"
  12
  13 /* "mdev -s" scans /sys/class/xxx, looking for directories which have dev
  14  * file (it is of the form "M:m\n"). Example: /sys/class/tty/tty0/dev
  15  * contains "4:0\n". Directory name is taken as device name, path component
  16  * directly after /sys/class/ as subsystem. In this example, "tty0" and "tty".
  17  * Then mdev creates the /dev/device_name node.
  18  *
  19  * mdev w/o parameters is called as hotplug helper. It takes device
  20  * and subsystem names from $DEVPATH and $SUBSYSTEM, extracts
  21  * maj,min from "/sys/$DEVPATH/dev" and also examines
  22  * $ACTION ("add"/"delete") and $FIRMWARE.
  23  *
  24  * If action is "add", mdev creates /dev/device_name similarly to mdev -s.
  25  * (todo: explain "delete" and $FIRMWARE)
  26  *
  27  * If /etc/mdev.conf exists, it may modify /dev/device_name's properties.
  28  * /etc/mdev.conf file format:
  29  *
  30  * [-][subsystem/]device  user:grp  mode  [>|=path] [@|$|*command args...]
  31  * [-]@maj,min[-min2]     user:grp  mode  [>|=path] [@|$|*command args...]
  32  *
  33  * The device name or "subsystem/device" combo is matched against 1st field
  34  * (which is a regex), or maj,min is matched against 1st field.
  35  *
  36  * Leading minus in 1st field means "don't stop on this line", otherwise
  37  * search is stopped after the matching line is encountered.
  38  *
  39  * When line matches, the device node is created, chmod'ed and chown'ed.
  40  * Then it moved to path, and if >path, a symlink to moved node is created
  41  *    Examples:
  42  *    =loop/      - moves to /dev/loop
  43  *    >disk/sda%1 - moves to /dev/disk/sdaN, makes /dev/sdaN a symlink
  44  * Then "command args" is executed (via sh -c 'command args').
  45  * @:execute on creation, $:on deletion, *:on both.
  46  */
  47
  48 struct globals {
  49         int root_major, root_minor;
  50         char *subsystem;
  51 };
  52 #define G (*(struct globals*)&bb_common_bufsiz1)
  53 #define root_major (G.root_major)
  54 #define root_minor (G.root_minor)
  55 #define subsystem  (G.subsystem )
  56
  57 /* Prevent infinite loops in /sys symlinks */
  58 #define MAX_SYSFS_DEPTH 3
  59
  60 /* We use additional 64+ bytes in make_device() */
  61 #define SCRATCH_SIZE 80
  62
  63 /* Builds an alias path.
  64  * This function potentionally reallocates the alias parameter.
  65  * Only used for ENABLE_FEATURE_MDEV_RENAME
  66  */
  67 static char *build_alias(char *alias, const char *device_name)
  68 {
  69         char *dest;
  70
  71         /* ">bar/": rename to bar/device_name */
  72         /* ">bar[/]baz": rename to bar[/]baz */
  73         dest = strrchr(alias, '/');
  74         if (dest) { /* ">bar/[baz]" ? */
  75                 *dest = '\0'; /* mkdir bar */
  76                 bb_make_directory(alias, 0755, FILEUTILS_RECUR);
  77                 *dest = '/';
  78                 if (dest[1] == '\0') { /* ">bar/" => ">bar/device_name" */
  79                         dest = alias;
  80                         alias = concat_path_file(alias, device_name);
  81                         free(dest);
  82                 }
  83         }
  84
  85         return alias;
  86 }
  87
  88 /* mknod in /dev based on a path like "/sys/block/hda/hda1" */
  89 /* NB: "mdev -s" may call us many times, do not leak memory/fds! */
  90 static void make_device(char *path, int delete)
  91 {
  92         const char *device_name;
  93         int major, minor, type, len;
  94         int mode;
  95         char *dev_maj_min = path + strlen(path);
  96         parser_t *parser;
  97
  98         /* Force the configuration file settings exactly. */
  99         umask(0);
 100
 101         /* Try to read major/minor string.  Note that the kernel puts \n after
 102          * the data, so we don't need to worry about null terminating the string
 103          * because sscanf() will stop at the first nondigit, which \n is.
 104          * We also depend on path having writeable space after it.
 105          */
 106         major = -1;
 107         if (!delete) {
 108                 strcpy(dev_maj_min, "/dev");
 109                 len = open_read_close(path, dev_maj_min + 1, 64);
 110                 *dev_maj_min++ = '\0';
 111                 if (len < 1) {
 112                         if (!ENABLE_FEATURE_MDEV_EXEC)
 113                                 return;
 114                         /* no "dev" file, so just try to run script */
 115                         *dev_maj_min = '\0';
 116                 } else if (sscanf(dev_maj_min, "%u:%u", &major, &minor) != 2) {
 117                         major = -1;
 118                 }
 119         }
 120
 121         /* Determine device name, type, major and minor */
 122         device_name = bb_basename(path);
 123         /* http://kernel.org/doc/pending/hotplug.txt says that only
 124          * "/sys/block/..." is for block devices. "/sys/bus" etc is not.
 125          * But since 2.6.25 block devices are also in /sys/class/block,
 126          * we use strstr("/block/") to forestall future surprises. */
 127         type = S_IFCHR;
 128         if (strstr(path, "/block/"))
 129                 type = S_IFBLK;
 130
 131         /* Make path point to "subsystem/device_name" */
 132         if (path[5] == 'b') /* legacy /sys/block? */
 133                 path += sizeof("/sys/") - 1;
 134         else
 135                 path += sizeof("/sys/class/") - 1;
 136
 137         /* If we have config file, look up user settings */
 138         if (ENABLE_FEATURE_MDEV_CONF)
 139                 parser = config_open2("/etc/mdev.conf", fopen_for_read);
 140
 141         do {
 142                 regmatch_t off[1 + 9 * ENABLE_FEATURE_MDEV_RENAME_REGEXP];
 143                 int keep_matching;
 144                 char *val, *name;
 145                 struct bb_uidgid_t ugid;
 146                 char *tokens[4];
 147                 char *command = NULL;
 148                 char *alias = NULL;
 149                 char aliaslink = aliaslink; /* for compiler */
 150
 151                 /* Defaults in case we won't match any line */
 152                 ugid.uid = ugid.gid = 0;
 153                 keep_matching = 0;
 154                 mode = 0660;
 155
 156                 if (ENABLE_FEATURE_MDEV_CONF
 157                  && config_read(parser, tokens, 4, 3, "# \t", PARSE_NORMAL)
 158                 ) {
 159                         val = tokens[0];
 160                         keep_matching = ('-' == val[0]);
 161                         val += keep_matching; /* swallow leading dash */
 162
 163                         /* Match against either "subsystem/device_name"
 164                          * or "device_name" alone */
 165                         name = strchr(val, '/') ? path : (char *) device_name;
 166
 167                         /* Fields: regex uid:gid mode [alias] [cmd] */
 168
 169                         /* 1st field: @<numeric maj,min>... */
 170                         if (val[0] == '@') {
 171                                 /* @major,minor[-last] */
 172                                 /* (useful when name is ambiguous:
 173                                  * "/sys/class/usb/lp0" and
 174                                  * "/sys/class/printer/lp0") */
 175                                 int cmaj, cmin0, cmin1, sc;
 176                                 if (major < 0)
 177                                         continue; /* no dev, no match */
 178                                 sc = sscanf(val, "@%u,%u-%u", &cmaj, &cmin0, &cmin1);
 179                                 if (sc < 1 || major != cmaj
 180                                  || (sc == 2 && minor != cmin0)
 181                                  || (sc == 3 && (minor < cmin0 || minor > cmin1))
 182                                 ) {
 183                                         continue; /* this line doesn't match */
 184                                 }
 185                         } else { /* ... or regex to match device name */
 186                                 regex_t match;
 187                                 int result;
 188
 189                                 /* Is this it? */
 190                                 xregcomp(&match, val, REG_EXTENDED);
 191                                 result = regexec(&match, name, ARRAY_SIZE(off), off, 0);
 192                                 regfree(&match);
 193
 194                                 //bb_error_msg("matches:");
 195                                 //for (int i = 0; i < ARRAY_SIZE(off); i++) {
 196                                 //      if (off[i].rm_so < 0) continue;
 197                                 //      bb_error_msg("match %d: '%.*s'\n", i,
 198                                 //              (int)(off[i].rm_eo - off[i].rm_so),
 199                                 //              device_name + off[i].rm_so);
 200                                 //}
 201
 202                                 /* If not this device, skip rest of line */
 203                                 /* (regexec returns whole pattern as "range" 0) */
 204                                 if (result || off[0].rm_so
 205                                  || ((int)off[0].rm_eo != (int)strlen(name))
 206                                 ) {
 207                                         continue; /* this line doesn't match */
 208                                 }
 209                         }
 210
 211                         /* This line matches: stop parsing the file after parsing
 212                          * the rest of fields unless keep_matching == 1 */
 213
 214                         /* 2nd field: uid:gid - device ownership */
 215                         parse_chown_usergroup_or_die(&ugid, tokens[1]);
 216
 217                         /* 3rd field: mode - device permissions */
 218                         mode = strtoul(tokens[2], NULL, 8);
 219
 220                         val = tokens[3];
 221                         /* 4th field (opt): >|=alias */
 222
 223                         if (ENABLE_FEATURE_MDEV_RENAME && val) {
 224                                 aliaslink = val[0];
 225                                 if (aliaslink == '>' || aliaslink == '=') {
 226                                         char *a, *s, *st;
 227                                         char *p;
 228                                         unsigned i, n;
 229
 230                                         a = val;
 231                                         s = strchrnul(val, ' ');
 232                                         st = strchrnul(val, '\t');
 233                                         if (st < s)
 234                                                 s = st;
 235                                         val = (s[0] && s[1]) ? s+1 : NULL;
 236                                         s[0] = '\0';
 237
 238                                         if (ENABLE_FEATURE_MDEV_RENAME_REGEXP) {
 239                                                 /* substitute %1..9 with off[1..9], if any */
 240                                                 n = 0;
 241                                                 s = a;
 242                                                 while (*s)
 243                                                         if (*s++ == '%')
 244                                                                 n++;
 245
 246                                                 p = alias = xzalloc(strlen(a) + n * strlen(name));
 247                                                 s = a + 1;
 248                                                 while (*s) {
 249                                                         *p = *s;
 250                                                         if ('%' == *s) {
 251                                                                 i = (s[1] - '0');
 252                                                                 if (i <= 9 && off[i].rm_so >= 0) {
 253                                                                         n = off[i].rm_eo - off[i].rm_so;
 254                                                                         strncpy(p, name + off[i].rm_so, n);
 255                                                                         p += n - 1;
 256                                                                         s++;
 257                                                                 }
 258                                                         }
 259                                                         p++;
 260                                                         s++;
 261                                                 }
 262                                         } else {
 263                                                 alias = xstrdup(a + 1);
 264                                         }
 265                                 }
 266                         }
 267
 268                         if (ENABLE_FEATURE_MDEV_EXEC && val) {
 269                                 const char *s = "$@*";
 270                                 const char *s2 = strchr(s, val[0]);
 271
 272                                 if (!s2)
 273                                         bb_error_msg_and_die("bad line %u", parser->lineno);
 274
 275                                 /* Are we running this command now?
 276                                  * Run $cmd on delete, @cmd on create, *cmd on both
 277                                  */
 278                                 if (s2-s != delete)
 279                                         command = xstrdup(val + 1);
 280                         }
 281                 }
 282
 283                 /* End of field parsing */
 284
 285                 /* "Execute" the line we found */
 286
 287                 if (!delete && major >= 0) {
 288                         if (ENABLE_FEATURE_MDEV_RENAME)
 289                                 unlink(device_name);
 290                         if (mknod(device_name, mode | type, makedev(major, minor)) && errno != EEXIST)
 291                                 bb_perror_msg_and_die("mknod %s", device_name);
 292                         if (major == root_major && minor == root_minor)
 293                                 symlink(device_name, "root");
 294                         if (ENABLE_FEATURE_MDEV_CONF) {
 295                                 chmod(device_name, mode);
 296                                 chown(device_name, ugid.uid, ugid.gid);
 297                         }
 298                         if (ENABLE_FEATURE_MDEV_RENAME && alias) {
 299                                 alias = build_alias(alias, device_name);
 300                                 /* move the device, and optionally
 301                                  * make a symlink to moved device node */
 302                                 if (rename(device_name, alias) == 0 && aliaslink == '>')
 303                                         symlink(alias, device_name);
 304                                 free(alias);
 305                         }
 306                 }
 307
 308                 if (ENABLE_FEATURE_MDEV_EXEC && command) {
 309                         /* setenv will leak memory, use putenv/unsetenv/free */
 310                         char *s = xasprintf("%s=%s", "MDEV", device_name);
 311                         char *s1 = xasprintf("%s=%s", "SUBSYSTEM", subsystem);
 312                         putenv(s);
 313                         putenv(s1);
 314                         if (system(command) == -1)
 315                                 bb_perror_msg_and_die("can't run '%s'", command);
 316                         unsetenv("SUBSYSTEM");
 317                         free(s1);
 318                         unsetenv("MDEV");
 319                         free(s);
 320                         free(command);
 321                 }
 322
 323                 if (delete) {
 324                         unlink(device_name);
 325                         /* At creation time, device might have been moved
 326                          * and a symlink might have been created. Undo that. */
 327
 328                         if (ENABLE_FEATURE_MDEV_RENAME && alias) {
 329                                 alias = build_alias(alias, device_name);
 330                                 unlink(alias);
 331                                 free(alias);
 332                         }
 333                 }
 334
 335                 /* We found matching line.
 336                  * Stop unless it was prefixed with '-' */
 337                 if (ENABLE_FEATURE_MDEV_CONF && !keep_matching)
 338                         break;
 339
 340         /* end of "while line is read from /etc/mdev.conf" */
 341         } while (ENABLE_FEATURE_MDEV_CONF);
 342
 343         if (ENABLE_FEATURE_MDEV_CONF)
 344                 config_close(parser);
 345 }
 346
 347 /* File callback for /sys/ traversal */
 348 static int FAST_FUNC fileAction(const char *fileName,
 349                 struct stat *statbuf UNUSED_PARAM,
 350                 void *userData,
 351                 int depth UNUSED_PARAM)
 352 {
 353         size_t len = strlen(fileName) - 4; /* can't underflow */
 354         char *scratch = userData;
 355
 356         /* len check is for paranoid reasons */
 357         if (strcmp(fileName + len, "/dev") != 0 || len >= PATH_MAX)
 358                 return FALSE;
 359
 360         strcpy(scratch, fileName);
 361         scratch[len] = '\0';
 362         make_device(scratch, 0);
 363
 364         return TRUE;
 365 }
 366
 367 /* Directory callback for /sys/ traversal */
 368 static int FAST_FUNC dirAction(const char *fileName UNUSED_PARAM,
 369                 struct stat *statbuf UNUSED_PARAM,
 370                 void *userData UNUSED_PARAM,
 371                 int depth)
 372 {
 373         /* Extract device subsystem -- the name of the directory
 374          * under /sys/class/ */
 375         if (1 == depth) {
 376                 free(subsystem);
 377                 subsystem = strrchr(fileName, '/');
 378                 if (subsystem)
 379                         subsystem = xstrdup(subsystem + 1);
 380         }
 381
 382         return (depth >= MAX_SYSFS_DEPTH ? SKIP : TRUE);
 383 }
 384
 385 /* For the full gory details, see linux/Documentation/firmware_class/README
 386  *
 387  * Firmware loading works like this:
 388  * - kernel sets FIRMWARE env var
 389  * - userspace checks /lib/firmware/$FIRMWARE
 390  * - userspace waits for /sys/$DEVPATH/loading to appear
 391  * - userspace writes "1" to /sys/$DEVPATH/loading
 392  * - userspace copies /lib/firmware/$FIRMWARE into /sys/$DEVPATH/data
 393  * - userspace writes "0" (worked) or "-1" (failed) to /sys/$DEVPATH/loading
 394  * - kernel loads firmware into device
 395  */
 396 static void load_firmware(const char *firmware, const char *sysfs_path)
 397 {
 398         int cnt;
 399         int firmware_fd, loading_fd, data_fd;
 400
 401         /* check for /lib/firmware/$FIRMWARE */
 402         xchdir("/lib/firmware");
 403         firmware_fd = xopen(firmware, O_RDONLY);
 404
 405         /* in case we goto out ... */
 406         data_fd = -1;
 407
 408         /* check for /sys/$DEVPATH/loading ... give 30 seconds to appear */
 409         xchdir(sysfs_path);
 410         for (cnt = 0; cnt < 30; ++cnt) {
 411                 loading_fd = open("loading", O_WRONLY);
 412                 if (loading_fd != -1)
 413                         goto loading;
 414                 sleep(1);
 415         }
 416         goto out;
 417
 418  loading:
 419         /* tell kernel we're loading by "echo 1 > /sys/$DEVPATH/loading" */
 420         if (full_write(loading_fd, "1", 1) != 1)
 421                 goto out;
 422
 423         /* load firmware into /sys/$DEVPATH/data */
 424         data_fd = open("data", O_WRONLY);
 425         if (data_fd == -1)
 426                 goto out;
 427         cnt = bb_copyfd_eof(firmware_fd, data_fd);
 428
 429         /* tell kernel result by "echo [0|-1] > /sys/$DEVPATH/loading" */
 430         if (cnt > 0)
 431                 full_write(loading_fd, "0", 1);
 432         else
 433                 full_write(loading_fd, "-1", 2);
 434
 435  out:
 436         if (ENABLE_FEATURE_CLEAN_UP) {
 437                 close(firmware_fd);
 438                 close(loading_fd);
 439                 close(data_fd);
 440         }
 441 }
 442
 443 int mdev_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 444 int mdev_main(int argc UNUSED_PARAM, char **argv)
 445 {
 446         RESERVE_CONFIG_BUFFER(temp, PATH_MAX + SCRATCH_SIZE);
 447
 448         /* We can be called as hotplug helper */
 449         /* Kernel cannot provide suitable stdio fds for us, do it ourself */
 450
 451         bb_sanitize_stdio();
 452
 453         xchdir("/dev");
 454
 455         if (argv[1] && strcmp(argv[1], "-s") == 0) {
 456                 /* Scan:
 457                  * mdev -s
 458                  */
 459                 struct stat st;
 460
 461                 xstat("/", &st);
 462                 root_major = major(st.st_dev);
 463                 root_minor = minor(st.st_dev);
 464
 465                 /* ACTION_FOLLOWLINKS is needed since in newer kernels
 466                  * /sys/block/loop* (for example) are symlinks to dirs,
 467                  * not real directories.
 468                  * (kernel's CONFIG_SYSFS_DEPRECATED makes them real dirs,
 469                  * but we can't enforce that on users)
 470                  */
 471                 if (access("/sys/class/block", F_OK) != 0) {
 472                         /* Scan obsolete /sys/block only if /sys/class/block
 473                          * doesn't exist. Otherwise we'll have dupes.
 474                          * Also, do not complain if it doesn't exist.
 475                          * Some people configure kernel to have no blockdevs.
 476                          */
 477                         recursive_action("/sys/block",
 478                                 ACTION_RECURSE | ACTION_FOLLOWLINKS | ACTION_QUIET,
 479                                 fileAction, dirAction, temp, 0);
 480                 }
 481                 recursive_action("/sys/class",
 482                         ACTION_RECURSE | ACTION_FOLLOWLINKS,
 483                         fileAction, dirAction, temp, 0);
 484         } else {
 485                 char *fw;
 486                 char *seq;
 487                 char *action;
 488                 char *env_path;
 489
 490                 /* Hotplug:
 491                  * env ACTION=... DEVPATH=... SUBSYSTEM=... [SEQNUM=...] mdev
 492                  * ACTION can be "add" or "remove"
 493                  * DEVPATH is like "/block/sda" or "/class/input/mice"
 494                  */
 495                 action = getenv("ACTION");
 496                 env_path = getenv("DEVPATH");
 497                 subsystem = getenv("SUBSYSTEM");
 498                 if (!action || !env_path /*|| !subsystem*/)
 499                         bb_show_usage();
 500                 fw = getenv("FIRMWARE");
 501
 502                 /* If it exists, does /dev/mdev.seq match $SEQNUM?
 503                  * If it does not match, earlier mdev is running
 504                  * in parallel, and we need to wait */
 505                 seq = getenv("SEQNUM");
 506                 if (seq) {
 507                         int timeout = 2000 / 32; /* 2000 msec */
 508                         do {
 509                                 int seqlen;
 510                                 char seqbuf[sizeof(int)*3 + 2];
 511
 512                                 seqlen = open_read_close("mdev.seq", seqbuf, sizeof(seqbuf-1));
 513                                 if (seqlen < 0) {
 514                                         seq = NULL;
 515                                         break;
 516                                 }
 517                                 seqbuf[seqlen] = '\0';
 518                                 if (seqbuf[0] == '\n' /* seed file? */
 519                                  || strcmp(seq, seqbuf) == 0 /* correct idx? */
 520                                 ) {
 521                                         break;
 522                                 }
 523                                 usleep(32*1000);
 524                         } while (--timeout);
 525                 }
 526
 527                 snprintf(temp, PATH_MAX, "/sys%s", env_path);
 528                 if (strcmp(action, "remove") == 0) {
 529                         /* Ignoring "remove firmware". It was reported
 530                          * to happen and to cause erroneous deletion
 531                          * of device nodes. */
 532                         if (!fw)
 533                                 make_device(temp, 1);
 534                 }
 535                 else if (strcmp(action, "add") == 0) {
 536                         make_device(temp, 0);
 537                         if (ENABLE_FEATURE_MDEV_LOAD_FIRMWARE) {
 538                                 if (fw)
 539                                         load_firmware(fw, temp);
 540                         }
 541                 }
 542
 543                 if (seq) {
 544                         xopen_xwrite_close("mdev.seq", utoa(xatou(seq) + 1));
 545                 }
 546         }
 547
 548         if (ENABLE_FEATURE_CLEAN_UP)
 549                 RELEASE_CONFIG_BUFFER(temp);
 550
 551         return EXIT_SUCCESS;
 552 }