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