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  * NB1: path parameter needs to have SCRATCH_SIZE scratch bytes
 106  * after NUL, but we promise to not mangle (IOW: to restore if needed)
 107  * path string.
 108  * NB2: "mdev -s" may call us many times, do not leak memory/fds!
 109  */
 110 static void make_device(char *path, int delete)
 111 {
 112         char *device_name;
 113         int major, minor, type, len;
 114         mode_t mode;
 115         parser_t *parser;
 116
 117         /* Try to read major/minor string.  Note that the kernel puts \n after
 118          * the data, so we don't need to worry about null terminating the string
 119          * because sscanf() will stop at the first nondigit, which \n is.
 120          * We also depend on path having writeable space after it.
 121          */
 122         major = -1;
 123         if (!delete) {
 124                 char *dev_maj_min = path + strlen(path);
 125
 126                 strcpy(dev_maj_min, "/dev");
 127                 len = open_read_close(path, dev_maj_min + 1, 64);
 128                 *dev_maj_min = '\0';
 129                 if (len < 1) {
 130                         if (!ENABLE_FEATURE_MDEV_EXEC)
 131                                 return;
 132                         /* no "dev" file, but we can still run scripts
 133                          * based on device name */
 134                 } else if (sscanf(++dev_maj_min, "%u:%u", &major, &minor) != 2) {
 135                         major = -1;
 136                 }
 137         }
 138
 139         /* Determine device name, type, major and minor */
 140         device_name = (char*) bb_basename(path);
 141         /* http://kernel.org/doc/pending/hotplug.txt says that only
 142          * "/sys/block/..." is for block devices. "/sys/bus" etc is not.
 143          * But since 2.6.25 block devices are also in /sys/class/block,
 144          * we use strstr("/block/") to forestall future surprises. */
 145         type = S_IFCHR;
 146         if (strstr(path, "/block/"))
 147                 type = S_IFBLK;
 148
 149         /* Make path point to "subsystem/device_name" */
 150         if (path[5] == 'b') /* legacy /sys/block? */
 151                 path += sizeof("/sys/") - 1;
 152         else
 153                 path += sizeof("/sys/class/") - 1;
 154
 155         /* If we have config file, look up user settings */
 156         if (ENABLE_FEATURE_MDEV_CONF)
 157                 parser = config_open2("/etc/mdev.conf", fopen_for_read);
 158
 159         do {
 160                 int keep_matching;
 161                 struct bb_uidgid_t ugid;
 162                 char *tokens[4];
 163                 char *command = NULL;
 164                 char *alias = NULL;
 165                 char aliaslink = aliaslink; /* for compiler */
 166
 167                 /* Defaults in case we won't match any line */
 168                 ugid.uid = ugid.gid = 0;
 169                 keep_matching = 0;
 170                 mode = 0660;
 171
 172                 if (ENABLE_FEATURE_MDEV_CONF
 173                  && config_read(parser, tokens, 4, 3, "# \t", PARSE_NORMAL)
 174                 ) {
 175                         char *val;
 176                         char *str_to_match;
 177                         regmatch_t off[1 + 9 * ENABLE_FEATURE_MDEV_RENAME_REGEXP];
 178
 179                         val = tokens[0];
 180                         keep_matching = ('-' == val[0]);
 181                         val += keep_matching; /* swallow leading dash */
 182
 183                         /* Match against either "subsystem/device_name"
 184                          * or "device_name" alone */
 185                         str_to_match = strchr(val, '/') ? path : device_name;
 186
 187                         /* Fields: regex uid:gid mode [alias] [cmd] */
 188
 189                         if (val[0] == '@') {
 190                                 /* @major,minor[-minor2] */
 191                                 /* (useful when name is ambiguous:
 192                                  * "/sys/class/usb/lp0" and
 193                                  * "/sys/class/printer/lp0") */
 194                                 int cmaj, cmin0, cmin1, sc;
 195                                 if (major < 0)
 196                                         continue; /* no dev, no match */
 197                                 sc = sscanf(val, "@%u,%u-%u", &cmaj, &cmin0, &cmin1);
 198                                 if (sc < 1 || major != cmaj
 199                                  || (sc == 2 && minor != cmin0)
 200                                  || (sc == 3 && (minor < cmin0 || minor > cmin1))
 201                                 ) {
 202                                         continue; /* this line doesn't match */
 203                                 }
 204                                 goto line_matches;
 205                         }
 206                         if (val[0] == '$') {
 207                                 /* regex to match an environment variable */
 208                                 char *eq = strchr(++val, '=');
 209                                 if (!eq)
 210                                         continue;
 211                                 *eq = '\0';
 212                                 str_to_match = getenv(val);
 213                                 if (!str_to_match)
 214                                         continue;
 215                                 str_to_match -= strlen(val) + 1;
 216                                 *eq = '=';
 217                         }
 218                         /* else: regex to match [subsystem/]device_name */
 219
 220                         {
 221                                 regex_t match;
 222                                 int result;
 223
 224                                 xregcomp(&match, val, REG_EXTENDED);
 225                                 result = regexec(&match, str_to_match, ARRAY_SIZE(off), off, 0);
 226                                 regfree(&match);
 227                                 //bb_error_msg("matches:");
 228                                 //for (int i = 0; i < ARRAY_SIZE(off); i++) {
 229                                 //      if (off[i].rm_so < 0) continue;
 230                                 //      bb_error_msg("match %d: '%.*s'\n", i,
 231                                 //              (int)(off[i].rm_eo - off[i].rm_so),
 232                                 //              device_name + off[i].rm_so);
 233                                 //}
 234
 235                                 /* If no match, skip rest of line */
 236                                 /* (regexec returns whole pattern as "range" 0) */
 237                                 if (result || off[0].rm_so
 238                                  || ((int)off[0].rm_eo != (int)strlen(str_to_match))
 239                                 ) {
 240                                         continue; /* this line doesn't match */
 241                                 }
 242                         }
 243  line_matches:
 244                         /* This line matches. Stop parsing after parsing
 245                          * the rest the line unless keep_matching == 1 */
 246
 247                         /* 2nd field: uid:gid - device ownership */
 248                         if (get_uidgid(&ugid, tokens[1], 1) == 0)
 249                                 bb_error_msg("unknown user/group %s on line %d", tokens[1], parser->lineno);
 250
 251                         /* 3rd field: mode - device permissions */
 252                         /* mode = strtoul(tokens[2], NULL, 8); */
 253                         bb_parse_mode(tokens[2], &mode);
 254
 255                         val = tokens[3];
 256                         /* 4th field (opt): >|=alias */
 257
 258                         if (ENABLE_FEATURE_MDEV_RENAME && val) {
 259                                 aliaslink = val[0];
 260                                 if (aliaslink == '>' || aliaslink == '=') {
 261                                         char *a, *s, *st;
 262                                         char *p;
 263                                         unsigned i, n;
 264
 265                                         a = val;
 266                                         s = strchrnul(val, ' ');
 267                                         st = strchrnul(val, '\t');
 268                                         if (st < s)
 269                                                 s = st;
 270                                         val = (s[0] && s[1]) ? s+1 : NULL;
 271                                         s[0] = '\0';
 272
 273                                         if (ENABLE_FEATURE_MDEV_RENAME_REGEXP) {
 274                                                 /* substitute %1..9 with off[1..9], if any */
 275                                                 n = 0;
 276                                                 s = a;
 277                                                 while (*s)
 278                                                         if (*s++ == '%')
 279                                                                 n++;
 280
 281                                                 p = alias = xzalloc(strlen(a) + n * strlen(str_to_match));
 282                                                 s = a + 1;
 283                                                 while (*s) {
 284                                                         *p = *s;
 285                                                         if ('%' == *s) {
 286                                                                 i = (s[1] - '0');
 287                                                                 if (i <= 9 && off[i].rm_so >= 0) {
 288                                                                         n = off[i].rm_eo - off[i].rm_so;
 289                                                                         strncpy(p, str_to_match + off[i].rm_so, n);
 290                                                                         p += n - 1;
 291                                                                         s++;
 292                                                                 }
 293                                                         }
 294                                                         p++;
 295                                                         s++;
 296                                                 }
 297                                         } else {
 298                                                 alias = xstrdup(a + 1);
 299                                         }
 300                                 }
 301                         }
 302
 303                         if (ENABLE_FEATURE_MDEV_EXEC && val) {
 304                                 const char *s = "$@*";
 305                                 const char *s2 = strchr(s, val[0]);
 306
 307                                 if (!s2) {
 308                                         bb_error_msg("bad line %u", parser->lineno);
 309                                         if (ENABLE_FEATURE_MDEV_RENAME)
 310                                                 free(alias);
 311                                         continue;
 312                                 }
 313
 314                                 /* Are we running this command now?
 315                                  * Run $cmd on delete, @cmd on create, *cmd on both
 316                                  */
 317                                 if (s2-s != delete)
 318                                         command = xstrdup(val + 1);
 319                         }
 320                 }
 321
 322                 /* End of field parsing */
 323
 324                 /* "Execute" the line we found */
 325                 {
 326                         const char *node_name;
 327
 328                         node_name = device_name;
 329                         if (ENABLE_FEATURE_MDEV_RENAME && alias)
 330                                 node_name = alias = build_alias(alias, device_name);
 331
 332                         if (!delete && major >= 0) {
 333                                 if (mknod(node_name, mode | type, makedev(major, minor)) && errno != EEXIST)
 334                                         bb_perror_msg("can't create %s", node_name);
 335                                 if (major == root_major && minor == root_minor)
 336                                         symlink(node_name, "root");
 337                                 if (ENABLE_FEATURE_MDEV_CONF) {
 338                                         chmod(node_name, mode);
 339                                         chown(node_name, ugid.uid, ugid.gid);
 340                                 }
 341                                 if (ENABLE_FEATURE_MDEV_RENAME && alias) {
 342                                         if (aliaslink == '>')
 343                                                 symlink(node_name, device_name);
 344                                 }
 345                         }
 346
 347                         if (ENABLE_FEATURE_MDEV_EXEC && command) {
 348                                 /* setenv will leak memory, use putenv/unsetenv/free */
 349                                 char *s = xasprintf("%s=%s", "MDEV", node_name);
 350                                 char *s1 = xasprintf("%s=%s", "SUBSYSTEM", subsystem);
 351                                 putenv(s);
 352                                 putenv(s1);
 353                                 if (system(command) == -1)
 354                                         bb_perror_msg("can't run '%s'", command);
 355                                 unsetenv("SUBSYSTEM");
 356                                 free(s1);
 357                                 unsetenv("MDEV");
 358                                 free(s);
 359                                 free(command);
 360                         }
 361
 362                         if (delete) {
 363                                 if (ENABLE_FEATURE_MDEV_RENAME && alias) {
 364                                         if (aliaslink == '>')
 365                                                 unlink(device_name);
 366                                 }
 367                                 unlink(node_name);
 368                         }
 369
 370                         if (ENABLE_FEATURE_MDEV_RENAME)
 371                                 free(alias);
 372                 }
 373
 374                 /* We found matching line.
 375                  * Stop unless it was prefixed with '-' */
 376                 if (ENABLE_FEATURE_MDEV_CONF && !keep_matching)
 377                         break;
 378
 379         /* end of "while line is read from /etc/mdev.conf" */
 380         } while (ENABLE_FEATURE_MDEV_CONF);
 381
 382         if (ENABLE_FEATURE_MDEV_CONF)
 383                 config_close(parser);
 384 }
 385
 386 /* File callback for /sys/ traversal */
 387 static int FAST_FUNC fileAction(const char *fileName,
 388                 struct stat *statbuf UNUSED_PARAM,
 389                 void *userData,
 390                 int depth UNUSED_PARAM)
 391 {
 392         size_t len = strlen(fileName) - 4; /* can't underflow */
 393         char *scratch = userData;
 394
 395         /* len check is for paranoid reasons */
 396         if (strcmp(fileName + len, "/dev") != 0 || len >= PATH_MAX)
 397                 return FALSE;
 398
 399         strcpy(scratch, fileName);
 400         scratch[len] = '\0';
 401         make_device(scratch, 0);
 402
 403         return TRUE;
 404 }
 405
 406 /* Directory callback for /sys/ traversal */
 407 static int FAST_FUNC dirAction(const char *fileName UNUSED_PARAM,
 408                 struct stat *statbuf UNUSED_PARAM,
 409                 void *userData UNUSED_PARAM,
 410                 int depth)
 411 {
 412         /* Extract device subsystem -- the name of the directory
 413          * under /sys/class/ */
 414         if (1 == depth) {
 415                 free(subsystem);
 416                 subsystem = strrchr(fileName, '/');
 417                 if (subsystem)
 418                         subsystem = xstrdup(subsystem + 1);
 419         }
 420
 421         return (depth >= MAX_SYSFS_DEPTH ? SKIP : TRUE);
 422 }
 423
 424 /* For the full gory details, see linux/Documentation/firmware_class/README
 425  *
 426  * Firmware loading works like this:
 427  * - kernel sets FIRMWARE env var
 428  * - userspace checks /lib/firmware/$FIRMWARE
 429  * - userspace waits for /sys/$DEVPATH/loading to appear
 430  * - userspace writes "1" to /sys/$DEVPATH/loading
 431  * - userspace copies /lib/firmware/$FIRMWARE into /sys/$DEVPATH/data
 432  * - userspace writes "0" (worked) or "-1" (failed) to /sys/$DEVPATH/loading
 433  * - kernel loads firmware into device
 434  */
 435 static void load_firmware(const char *firmware, const char *sysfs_path)
 436 {
 437         int cnt;
 438         int firmware_fd, loading_fd, data_fd;
 439
 440         /* check for /lib/firmware/$FIRMWARE */
 441         xchdir("/lib/firmware");
 442         firmware_fd = xopen(firmware, O_RDONLY);
 443
 444         /* in case we goto out ... */
 445         data_fd = -1;
 446
 447         /* check for /sys/$DEVPATH/loading ... give 30 seconds to appear */
 448         xchdir(sysfs_path);
 449         for (cnt = 0; cnt < 30; ++cnt) {
 450                 loading_fd = open("loading", O_WRONLY);
 451                 if (loading_fd != -1)
 452                         goto loading;
 453                 sleep(1);
 454         }
 455         goto out;
 456
 457  loading:
 458         /* tell kernel we're loading by "echo 1 > /sys/$DEVPATH/loading" */
 459         if (full_write(loading_fd, "1", 1) != 1)
 460                 goto out;
 461
 462         /* load firmware into /sys/$DEVPATH/data */
 463         data_fd = open("data", O_WRONLY);
 464         if (data_fd == -1)
 465                 goto out;
 466         cnt = bb_copyfd_eof(firmware_fd, data_fd);
 467
 468         /* tell kernel result by "echo [0|-1] > /sys/$DEVPATH/loading" */
 469         if (cnt > 0)
 470                 full_write(loading_fd, "0", 1);
 471         else
 472                 full_write(loading_fd, "-1", 2);
 473
 474  out:
 475         if (ENABLE_FEATURE_CLEAN_UP) {
 476                 close(firmware_fd);
 477                 close(loading_fd);
 478                 close(data_fd);
 479         }
 480 }
 481
 482 int mdev_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 483 int mdev_main(int argc UNUSED_PARAM, char **argv)
 484 {
 485         RESERVE_CONFIG_BUFFER(temp, PATH_MAX + SCRATCH_SIZE);
 486
 487         /* We can be called as hotplug helper */
 488         /* Kernel cannot provide suitable stdio fds for us, do it ourself */
 489         bb_sanitize_stdio();
 490
 491         /* Force the configuration file settings exactly */
 492         umask(0);
 493
 494         xchdir("/dev");
 495
 496         if (argv[1] && strcmp(argv[1], "-s") == 0) {
 497                 /* Scan:
 498                  * mdev -s
 499                  */
 500                 struct stat st;
 501
 502                 xstat("/", &st);
 503                 root_major = major(st.st_dev);
 504                 root_minor = minor(st.st_dev);
 505
 506                 /* ACTION_FOLLOWLINKS is needed since in newer kernels
 507                  * /sys/block/loop* (for example) are symlinks to dirs,
 508                  * not real directories.
 509                  * (kernel's CONFIG_SYSFS_DEPRECATED makes them real dirs,
 510                  * but we can't enforce that on users)
 511                  */
 512                 if (access("/sys/class/block", F_OK) != 0) {
 513                         /* Scan obsolete /sys/block only if /sys/class/block
 514                          * doesn't exist. Otherwise we'll have dupes.
 515                          * Also, do not complain if it doesn't exist.
 516                          * Some people configure kernel to have no blockdevs.
 517                          */
 518                         recursive_action("/sys/block",
 519                                 ACTION_RECURSE | ACTION_FOLLOWLINKS | ACTION_QUIET,
 520                                 fileAction, dirAction, temp, 0);
 521                 }
 522                 recursive_action("/sys/class",
 523                         ACTION_RECURSE | ACTION_FOLLOWLINKS,
 524                         fileAction, dirAction, temp, 0);
 525         } else {
 526                 char *fw;
 527                 char *seq;
 528                 char *action;
 529                 char *env_path;
 530                 static const char keywords[] ALIGN1 = "remove\0add\0";
 531                 enum { OP_remove = 0, OP_add };
 532                 smalluint op;
 533
 534                 /* Hotplug:
 535                  * env ACTION=... DEVPATH=... SUBSYSTEM=... [SEQNUM=...] mdev
 536                  * ACTION can be "add" or "remove"
 537                  * DEVPATH is like "/block/sda" or "/class/input/mice"
 538                  */
 539                 action = getenv("ACTION");
 540                 env_path = getenv("DEVPATH");
 541                 subsystem = getenv("SUBSYSTEM");
 542                 if (!action || !env_path /*|| !subsystem*/)
 543                         bb_show_usage();
 544                 fw = getenv("FIRMWARE");
 545                 op = index_in_strings(keywords, action);
 546                 /* If it exists, does /dev/mdev.seq match $SEQNUM?
 547                  * If it does not match, earlier mdev is running
 548                  * in parallel, and we need to wait */
 549                 seq = getenv("SEQNUM");
 550                 if (seq) {
 551                         int timeout = 2000 / 32; /* 2000 msec */
 552                         do {
 553                                 int seqlen;
 554                                 char seqbuf[sizeof(int)*3 + 2];
 555
 556                                 seqlen = open_read_close("mdev.seq", seqbuf, sizeof(seqbuf-1));
 557                                 if (seqlen < 0) {
 558                                         seq = NULL;
 559                                         break;
 560                                 }
 561                                 seqbuf[seqlen] = '\0';
 562                                 if (seqbuf[0] == '\n' /* seed file? */
 563                                  || strcmp(seq, seqbuf) == 0 /* correct idx? */
 564                                 ) {
 565                                         break;
 566                                 }
 567                                 usleep(32*1000);
 568                         } while (--timeout);
 569                 }
 570
 571                 snprintf(temp, PATH_MAX, "/sys%s", env_path);
 572                 if (op == OP_remove) {
 573                         /* Ignoring "remove firmware". It was reported
 574                          * to happen and to cause erroneous deletion
 575                          * of device nodes. */
 576                         if (!fw)
 577                                 make_device(temp, 1);
 578                 }
 579                 else if (op == OP_add) {
 580                         make_device(temp, 0);
 581                         if (ENABLE_FEATURE_MDEV_LOAD_FIRMWARE) {
 582                                 if (fw)
 583                                         load_firmware(fw, temp);
 584                         }
 585                 }
 586
 587                 if (seq) {
 588                         xopen_xwrite_close("mdev.seq", utoa(xatou(seq) + 1));
 589                 }
 590         }
 591
 592         if (ENABLE_FEATURE_CLEAN_UP)
 593                 RELEASE_CONFIG_BUFFER(temp);
 594
 595         return EXIT_SUCCESS;
 596 }