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