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  * If /sys/class/.../dev file does not exist, mdev still may act
  19  * on this device: see "@|$|*command args..." parameter in config file.
  20  *
  21  * mdev w/o parameters is called as hotplug helper. It takes device
  22  * and subsystem names from $DEVPATH and $SUBSYSTEM, extracts
  23  * maj,min from "/sys/$DEVPATH/dev" and also examines
  24  * $ACTION ("add"/"delete") and $FIRMWARE.
  25  *
  26  * If action is "add", mdev creates /dev/device_name similarly to mdev -s.
  27  * (todo: explain "delete" and $FIRMWARE)
  28  *
  29  * If /etc/mdev.conf exists, it may modify /dev/device_name's properties.
  30  * /etc/mdev.conf file format:
  31  *
  32  * [-][subsystem/]device  user:grp  mode  [>|=path] [@|$|*command args...]
  33  * [-]@maj,min[-min2]     user:grp  mode  [>|=path] [@|$|*command args...]
  34  * [-]$envvar=val         user:grp  mode  [>|=path] [@|$|*command args...]
  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  * The device name or "subsystem/device" combo is matched against 1st field
  40  * (which is a regex), or maj,min is matched against 1st field,
  41  * or specified environment variable (as regex) is matched against 1st field.
  42  *
  43  * $envvar=val format is useful for loading modules for hot-plugged devices
  44  * which do not have driver loaded yet. In this case /sys/class/.../dev
  45  * does not exist, but $MODALIAS is set to needed module's name
  46  * (actually, an alias to it) by kernel. This rule instructs mdev
  47  * to load the module and exit:
  48  *    $MODALIAS=.* 0:0 660 @modprobe "$MODALIAS"
  49  * The kernel will generate another hotplug event when /sys/class/.../dev
  50  * file appears.
  51  *
  52  * When line matches, the device node is created, chmod'ed and chown'ed,
  53  * moved to path, and if >path, a symlink to moved node is created,
  54  * all this if /sys/class/.../dev exists.
  55  *    Examples:
  56  *    =loop/      - moves to /dev/loop
  57  *    >disk/sda%1 - moves to /dev/disk/sdaN, makes /dev/sdaN a symlink
  58  *
  59  * Then "command args..." is executed (via sh -c 'command args...').
  60  * @:execute on creation, $:on deletion, *:on both.
  61  * This happens regardless of /sys/class/.../dev existence.
  62  */
  63
  64 struct globals {
  65         int root_major, root_minor;
  66         char *subsystem;
  67 };
  68 #define G (*(struct globals*)&bb_common_bufsiz1)
  69 #define root_major (G.root_major)
  70 #define root_minor (G.root_minor)
  71 #define subsystem  (G.subsystem )
  72
  73 /* Prevent infinite loops in /sys symlinks */
  74 #define MAX_SYSFS_DEPTH 3
  75
  76 /* We use additional 64+ bytes in make_device() */
  77 #define SCRATCH_SIZE 80
  78
  79 /* Builds an alias path.
  80  * This function potentionally reallocates the alias parameter.
  81  * Only used for ENABLE_FEATURE_MDEV_RENAME
  82  */
  83 static char *build_alias(char *alias, const char *device_name)
  84 {
  85         char *dest;
  86
  87         /* ">bar/": rename to bar/device_name */
  88         /* ">bar[/]baz": rename to bar[/]baz */
  89         dest = strrchr(alias, '/');
  90         if (dest) { /* ">bar/[baz]" ? */
  91                 *dest = '\0'; /* mkdir bar */
  92                 bb_make_directory(alias, 0755, FILEUTILS_RECUR);
  93                 *dest = '/';
  94                 if (dest[1] == '\0') { /* ">bar/" => ">bar/device_name" */
  95                         dest = alias;
  96                         alias = concat_path_file(alias, device_name);
  97                         free(dest);
  98                 }
  99         }
 100
 101         return alias;
 102 }
 103
 104 /* mknod in /dev based on a path like "/sys/block/hda/hda1" */
 105 /* NB: "mdev -s" may call us many times, do not leak memory/fds! */
 106 static void make_device(char *path, int delete)
 107 {
 108         char *device_name;
 109         int major, minor, type, len;
 110         int mode;
 111         parser_t *parser;
 112
 113         /* Try to read major/minor string.  Note that the kernel puts \n after
 114          * the data, so we don't need to worry about null terminating the string
 115          * because sscanf() will stop at the first nondigit, which \n is.
 116          * We also depend on path having writeable space after it.
 117          */
 118         major = -1;
 119         if (!delete) {
 120                 char *dev_maj_min = path + strlen(path);
 121
 122                 strcpy(dev_maj_min, "/dev");
 123                 len = open_read_close(path, dev_maj_min + 1, 64);
 124                 *dev_maj_min = '\0';
 125                 if (len < 1) {
 126                         if (!ENABLE_FEATURE_MDEV_EXEC)
 127                                 return;
 128                         /* no "dev" file, but we can still run scripts
 129                          * based on device name */
 130                 } else if (sscanf(++dev_maj_min, "%u:%u", &major, &minor) != 2) {
 131                         major = -1;
 132                 }
 133         }
 134
 135         /* Determine device name, type, major and minor */
 136         device_name = (char*) bb_basename(path);
 137         /* http://kernel.org/doc/pending/hotplug.txt says that only
 138          * "/sys/block/..." is for block devices. "/sys/bus" etc is not.
 139          * But since 2.6.25 block devices are also in /sys/class/block,
 140          * we use strstr("/block/") to forestall future surprises. */
 141         type = S_IFCHR;
 142         if (strstr(path, "/block/"))
 143                 type = S_IFBLK;
 144
 145         /* Make path point to "subsystem/device_name" */
 146         if (path[5] == 'b') /* legacy /sys/block? */
 147                 path += sizeof("/sys/") - 1;
 148         else
 149                 path += sizeof("/sys/class/") - 1;
 150
 151         /* If we have config file, look up user settings */
 152         if (ENABLE_FEATURE_MDEV_CONF)
 153                 parser = config_open2("/etc/mdev.conf", fopen_for_read);
 154
 155         do {
 156                 int keep_matching;
 157                 struct bb_uidgid_t ugid;
 158                 char *tokens[4];
 159                 char *command = NULL;
 160                 char *alias = NULL;
 161                 char aliaslink = aliaslink; /* for compiler */
 162
 163                 /* Defaults in case we won't match any line */
 164                 ugid.uid = ugid.gid = 0;
 165                 keep_matching = 0;
 166                 mode = 0660;
 167
 168                 if (ENABLE_FEATURE_MDEV_CONF
 169                  && config_read(parser, tokens, 4, 3, "# \t", PARSE_NORMAL)
 170                 ) {
 171                         char *val;
 172                         char *str_to_match;
 173                         regmatch_t off[1 + 9 * ENABLE_FEATURE_MDEV_RENAME_REGEXP];
 174
 175                         val = tokens[0];
 176                         keep_matching = ('-' == val[0]);
 177                         val += keep_matching; /* swallow leading dash */
 178
 179                         /* Match against either "subsystem/device_name"
 180                          * or "device_name" alone */
 181                         str_to_match = strchr(val, '/') ? path : device_name;
 182
 183                         /* Fields: regex uid:gid mode [alias] [cmd] */
 184
 185                         if (val[0] == '@') {
 186                                 /* @major,minor[-minor2] */
 187                                 /* (useful when name is ambiguous:
 188                                  * "/sys/class/usb/lp0" and
 189                                  * "/sys/class/printer/lp0") */
 190                                 int cmaj, cmin0, cmin1, sc;
 191                                 if (major < 0)
 192                                         continue; /* no dev, no match */
 193                                 sc = sscanf(val, "@%u,%u-%u", &cmaj, &cmin0, &cmin1);
 194                                 if (sc < 1 || major != cmaj
 195                                  || (sc == 2 && minor != cmin0)
 196                                  || (sc == 3 && (minor < cmin0 || minor > cmin1))
 197                                 ) {
 198                                         continue; /* this line doesn't match */
 199                                 }
 200                                 goto line_matches;
 201                         }
 202                         if (val[0] == '$') {
 203                                 /* regex to match an environment variable */
 204                                 char *eq = strchr(++val, '=');
 205                                 if (!eq)
 206                                         continue;
 207                                 *eq = '\0';
 208                                 str_to_match = getenv(val);
 209                                 if (!str_to_match)
 210                                         continue;
 211                                 str_to_match -= strlen(val) + 1;
 212                                 *eq = '=';
 213                         }
 214                         /* else: regex to match [subsystem/]device_name */
 215
 216                         {
 217                                 regex_t match;
 218                                 int result;
 219
 220                                 xregcomp(&match, val, REG_EXTENDED);
 221                                 result = regexec(&match, str_to_match, ARRAY_SIZE(off), off, 0);
 222                                 regfree(&match);
 223                                 //bb_error_msg("matches:");
 224                                 //for (int i = 0; i < ARRAY_SIZE(off); i++) {
 225                                 //      if (off[i].rm_so < 0) continue;
 226                                 //      bb_error_msg("match %d: '%.*s'\n", i,
 227                                 //              (int)(off[i].rm_eo - off[i].rm_so),
 228                                 //              device_name + off[i].rm_so);
 229                                 //}
 230
 231                                 /* If no match, skip rest of line */
 232                                 /* (regexec returns whole pattern as "range" 0) */
 233                                 if (result || off[0].rm_so
 234                                  || ((int)off[0].rm_eo != (int)strlen(str_to_match))
 235                                 ) {
 236                                         continue; /* this line doesn't match */
 237                                 }
 238                         }
 239  line_matches:
 240                         /* This line matches. Stop parsing after parsing
 241                          * the rest the line unless keep_matching == 1 */
 242
 243                         /* 2nd field: uid:gid - device ownership */
 244                         parse_chown_usergroup_or_die(&ugid, tokens[1]);
 245
 246                         /* 3rd field: mode - device permissions */
 247                         mode = strtoul(tokens[2], NULL, 8);
 248
 249                         val = tokens[3];
 250                         /* 4th field (opt): >|=alias */
 251
 252                         if (ENABLE_FEATURE_MDEV_RENAME && val) {
 253                                 aliaslink = val[0];
 254                                 if (aliaslink == '>' || aliaslink == '=') {
 255                                         char *a, *s, *st;
 256                                         char *p;
 257                                         unsigned i, n;
 258
 259                                         a = val;
 260                                         s = strchrnul(val, ' ');
 261                                         st = strchrnul(val, '\t');
 262                                         if (st < s)
 263                                                 s = st;
 264                                         val = (s[0] && s[1]) ? s+1 : NULL;
 265                                         s[0] = '\0';
 266
 267                                         if (ENABLE_FEATURE_MDEV_RENAME_REGEXP) {
 268                                                 /* substitute %1..9 with off[1..9], if any */
 269                                                 n = 0;
 270                                                 s = a;
 271                                                 while (*s)
 272                                                         if (*s++ == '%')
 273                                                                 n++;
 274
 275                                                 p = alias = xzalloc(strlen(a) + n * strlen(str_to_match));
 276                                                 s = a + 1;
 277                                                 while (*s) {
 278                                                         *p = *s;
 279                                                         if ('%' == *s) {
 280                                                                 i = (s[1] - '0');
 281                                                                 if (i <= 9 && off[i].rm_so >= 0) {
 282                                                                         n = off[i].rm_eo - off[i].rm_so;
 283                                                                         strncpy(p, str_to_match + off[i].rm_so, n);
 284                                                                         p += n - 1;
 285                                                                         s++;
 286                                                                 }
 287                                                         }
 288                                                         p++;
 289                                                         s++;
 290                                                 }
 291                                         } else {
 292                                                 alias = xstrdup(a + 1);
 293                                         }
 294                                 }
 295                         }
 296
 297                         if (ENABLE_FEATURE_MDEV_EXEC && val) {
 298                                 const char *s = "$@*";
 299                                 const char *s2 = strchr(s, val[0]);
 300
 301                                 if (!s2)
 302                                         bb_error_msg_and_die("bad line %u", parser->lineno);
 303
 304                                 /* Are we running this command now?
 305                                  * Run $cmd on delete, @cmd on create, *cmd on both
 306                                  */
 307                                 if (s2-s != delete)
 308                                         command = xstrdup(val + 1);
 309                         }
 310                 }
 311
 312                 /* End of field parsing */
 313
 314                 /* "Execute" the line we found */
 315
 316                 if (!delete && major >= 0) {
 317                         if (ENABLE_FEATURE_MDEV_RENAME)
 318                                 unlink(device_name);
 319                         if (mknod(device_name, mode | type, makedev(major, minor)) && errno != EEXIST)
 320                                 bb_perror_msg_and_die("mknod %s", device_name);
 321                         if (major == root_major && minor == root_minor)
 322                                 symlink(device_name, "root");
 323                         if (ENABLE_FEATURE_MDEV_CONF) {
 324                                 chmod(device_name, mode);
 325                                 chown(device_name, ugid.uid, ugid.gid);
 326                         }
 327                         if (ENABLE_FEATURE_MDEV_RENAME && alias) {
 328                                 alias = build_alias(alias, device_name);
 329                                 /* move the device, and optionally
 330                                  * make a symlink to moved device node */
 331                                 if (rename(device_name, alias) == 0 && aliaslink == '>')
 332                                         symlink(alias, device_name);
 333                                 free(alias);
 334                         }
 335                 }
 336
 337                 if (ENABLE_FEATURE_MDEV_EXEC && command) {
 338                         /* setenv will leak memory, use putenv/unsetenv/free */
 339                         char *s = xasprintf("%s=%s", "MDEV", device_name);
 340                         char *s1 = xasprintf("%s=%s", "SUBSYSTEM", subsystem);
 341                         putenv(s);
 342                         putenv(s1);
 343                         if (system(command) == -1)
 344                                 bb_perror_msg_and_die("can't run '%s'", command);
 345                         unsetenv("SUBSYSTEM");
 346                         free(s1);
 347                         unsetenv("MDEV");
 348                         free(s);
 349                         free(command);
 350                 }
 351
 352                 if (delete) {
 353                         unlink(device_name);
 354                         /* At creation time, device might have been moved
 355                          * and a symlink might have been created. Undo that. */
 356
 357                         if (ENABLE_FEATURE_MDEV_RENAME && alias) {
 358                                 alias = build_alias(alias, device_name);
 359                                 unlink(alias);
 360                                 free(alias);
 361                         }
 362                 }
 363
 364                 /* We found matching line.
 365                  * Stop unless it was prefixed with '-' */
 366                 if (ENABLE_FEATURE_MDEV_CONF && !keep_matching)
 367                         break;
 368
 369         /* end of "while line is read from /etc/mdev.conf" */
 370         } while (ENABLE_FEATURE_MDEV_CONF);
 371
 372         if (ENABLE_FEATURE_MDEV_CONF)
 373                 config_close(parser);
 374 }
 375
 376 /* File callback for /sys/ traversal */
 377 static int FAST_FUNC fileAction(const char *fileName,
 378                 struct stat *statbuf UNUSED_PARAM,
 379                 void *userData,
 380                 int depth UNUSED_PARAM)
 381 {
 382         size_t len = strlen(fileName) - 4; /* can't underflow */
 383         char *scratch = userData;
 384
 385         /* len check is for paranoid reasons */
 386         if (strcmp(fileName + len, "/dev") != 0 || len >= PATH_MAX)
 387                 return FALSE;
 388
 389         strcpy(scratch, fileName);
 390         scratch[len] = '\0';
 391         make_device(scratch, 0);
 392
 393         return TRUE;
 394 }
 395
 396 /* Directory callback for /sys/ traversal */
 397 static int FAST_FUNC dirAction(const char *fileName UNUSED_PARAM,
 398                 struct stat *statbuf UNUSED_PARAM,
 399                 void *userData UNUSED_PARAM,
 400                 int depth)
 401 {
 402         /* Extract device subsystem -- the name of the directory
 403          * under /sys/class/ */
 404         if (1 == depth) {
 405                 free(subsystem);
 406                 subsystem = strrchr(fileName, '/');
 407                 if (subsystem)
 408                         subsystem = xstrdup(subsystem + 1);
 409         }
 410
 411         return (depth >= MAX_SYSFS_DEPTH ? SKIP : TRUE);
 412 }
 413
 414 /* For the full gory details, see linux/Documentation/firmware_class/README
 415  *
 416  * Firmware loading works like this:
 417  * - kernel sets FIRMWARE env var
 418  * - userspace checks /lib/firmware/$FIRMWARE
 419  * - userspace waits for /sys/$DEVPATH/loading to appear
 420  * - userspace writes "1" to /sys/$DEVPATH/loading
 421  * - userspace copies /lib/firmware/$FIRMWARE into /sys/$DEVPATH/data
 422  * - userspace writes "0" (worked) or "-1" (failed) to /sys/$DEVPATH/loading
 423  * - kernel loads firmware into device
 424  */
 425 static void load_firmware(const char *firmware, const char *sysfs_path)
 426 {
 427         int cnt;
 428         int firmware_fd, loading_fd, data_fd;
 429
 430         /* check for /lib/firmware/$FIRMWARE */
 431         xchdir("/lib/firmware");
 432         firmware_fd = xopen(firmware, O_RDONLY);
 433
 434         /* in case we goto out ... */
 435         data_fd = -1;
 436
 437         /* check for /sys/$DEVPATH/loading ... give 30 seconds to appear */
 438         xchdir(sysfs_path);
 439         for (cnt = 0; cnt < 30; ++cnt) {
 440                 loading_fd = open("loading", O_WRONLY);
 441                 if (loading_fd != -1)
 442                         goto loading;
 443                 sleep(1);
 444         }
 445         goto out;
 446
 447  loading:
 448         /* tell kernel we're loading by "echo 1 > /sys/$DEVPATH/loading" */
 449         if (full_write(loading_fd, "1", 1) != 1)
 450                 goto out;
 451
 452         /* load firmware into /sys/$DEVPATH/data */
 453         data_fd = open("data", O_WRONLY);
 454         if (data_fd == -1)
 455                 goto out;
 456         cnt = bb_copyfd_eof(firmware_fd, data_fd);
 457
 458         /* tell kernel result by "echo [0|-1] > /sys/$DEVPATH/loading" */
 459         if (cnt > 0)
 460                 full_write(loading_fd, "0", 1);
 461         else
 462                 full_write(loading_fd, "-1", 2);
 463
 464  out:
 465         if (ENABLE_FEATURE_CLEAN_UP) {
 466                 close(firmware_fd);
 467                 close(loading_fd);
 468                 close(data_fd);
 469         }
 470 }
 471
 472 int mdev_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 473 int mdev_main(int argc UNUSED_PARAM, char **argv)
 474 {
 475         RESERVE_CONFIG_BUFFER(temp, PATH_MAX + SCRATCH_SIZE);
 476
 477         /* We can be called as hotplug helper */
 478         /* Kernel cannot provide suitable stdio fds for us, do it ourself */
 479         bb_sanitize_stdio();
 480
 481         /* Force the configuration file settings exactly */
 482         umask(0);
 483
 484         xchdir("/dev");
 485
 486         if (argv[1] && strcmp(argv[1], "-s") == 0) {
 487                 /* Scan:
 488                  * mdev -s
 489                  */
 490                 struct stat st;
 491
 492                 xstat("/", &st);
 493                 root_major = major(st.st_dev);
 494                 root_minor = minor(st.st_dev);
 495
 496                 /* ACTION_FOLLOWLINKS is needed since in newer kernels
 497                  * /sys/block/loop* (for example) are symlinks to dirs,
 498                  * not real directories.
 499                  * (kernel's CONFIG_SYSFS_DEPRECATED makes them real dirs,
 500                  * but we can't enforce that on users)
 501                  */
 502                 if (access("/sys/class/block", F_OK) != 0) {
 503                         /* Scan obsolete /sys/block only if /sys/class/block
 504                          * doesn't exist. Otherwise we'll have dupes.
 505                          * Also, do not complain if it doesn't exist.
 506                          * Some people configure kernel to have no blockdevs.
 507                          */
 508                         recursive_action("/sys/block",
 509                                 ACTION_RECURSE | ACTION_FOLLOWLINKS | ACTION_QUIET,
 510                                 fileAction, dirAction, temp, 0);
 511                 }
 512                 recursive_action("/sys/class",
 513                         ACTION_RECURSE | ACTION_FOLLOWLINKS,
 514                         fileAction, dirAction, temp, 0);
 515         } else {
 516                 char *fw;
 517                 char *seq;
 518                 char *action;
 519                 char *env_path;
 520
 521                 /* Hotplug:
 522                  * env ACTION=... DEVPATH=... SUBSYSTEM=... [SEQNUM=...] mdev
 523                  * ACTION can be "add" or "remove"
 524                  * DEVPATH is like "/block/sda" or "/class/input/mice"
 525                  */
 526                 action = getenv("ACTION");
 527                 env_path = getenv("DEVPATH");
 528                 subsystem = getenv("SUBSYSTEM");
 529                 if (!action || !env_path /*|| !subsystem*/)
 530                         bb_show_usage();
 531                 fw = getenv("FIRMWARE");
 532
 533                 /* If it exists, does /dev/mdev.seq match $SEQNUM?
 534                  * If it does not match, earlier mdev is running
 535                  * in parallel, and we need to wait */
 536                 seq = getenv("SEQNUM");
 537                 if (seq) {
 538                         int timeout = 2000 / 32; /* 2000 msec */
 539                         do {
 540                                 int seqlen;
 541                                 char seqbuf[sizeof(int)*3 + 2];
 542
 543                                 seqlen = open_read_close("mdev.seq", seqbuf, sizeof(seqbuf-1));
 544                                 if (seqlen < 0) {
 545                                         seq = NULL;
 546                                         break;
 547                                 }
 548                                 seqbuf[seqlen] = '\0';
 549                                 if (seqbuf[0] == '\n' /* seed file? */
 550                                  || strcmp(seq, seqbuf) == 0 /* correct idx? */
 551                                 ) {
 552                                         break;
 553                                 }
 554                                 usleep(32*1000);
 555                         } while (--timeout);
 556                 }
 557
 558                 snprintf(temp, PATH_MAX, "/sys%s", env_path);
 559                 if (strcmp(action, "remove") == 0) {
 560                         /* Ignoring "remove firmware". It was reported
 561                          * to happen and to cause erroneous deletion
 562                          * of device nodes. */
 563                         if (!fw)
 564                                 make_device(temp, 1);
 565                 }
 566                 else if (strcmp(action, "add") == 0) {
 567                         /* make_device mangles its parameter, use a copy */
 568                         char *s = xstrdup(temp);
 569                         make_device(s, 0);
 570                         free(s);
 571                         if (ENABLE_FEATURE_MDEV_LOAD_FIRMWARE) {
 572                                 if (fw)
 573                                         load_firmware(fw, temp);
 574                         }
 575                 }
 576
 577                 if (seq) {
 578                         xopen_xwrite_close("mdev.seq", utoa(xatou(seq) + 1));
 579                 }
 580         }
 581
 582         if (ENABLE_FEATURE_CLEAN_UP)
 583                 RELEASE_CONFIG_BUFFER(temp);
 584
 585         return EXIT_SUCCESS;
 586 }