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 GPLv2, see file LICENSE in this source tree.
   9  */
  10 //config:config MDEV
  11 //config:       bool "mdev (17 kb)"
  12 //config:       default y
  13 //config:       select PLATFORM_LINUX
  14 //config:       help
  15 //config:       mdev is a mini-udev implementation for dynamically creating device
  16 //config:       nodes in the /dev directory.
  17 //config:
  18 //config:       For more information, please see docs/mdev.txt
  19 //config:
  20 //config:config FEATURE_MDEV_CONF
  21 //config:       bool "Support /etc/mdev.conf"
  22 //config:       default y
  23 //config:       depends on MDEV
  24 //config:       help
  25 //config:       Add support for the mdev config file to control ownership and
  26 //config:       permissions of the device nodes.
  27 //config:
  28 //config:       For more information, please see docs/mdev.txt
  29 //config:
  30 //config:config FEATURE_MDEV_RENAME
  31 //config:       bool "Support subdirs/symlinks"
  32 //config:       default y
  33 //config:       depends on FEATURE_MDEV_CONF
  34 //config:       help
  35 //config:       Add support for renaming devices and creating symlinks.
  36 //config:
  37 //config:       For more information, please see docs/mdev.txt
  38 //config:
  39 //config:config FEATURE_MDEV_RENAME_REGEXP
  40 //config:       bool "Support regular expressions substitutions when renaming device"
  41 //config:       default y
  42 //config:       depends on FEATURE_MDEV_RENAME
  43 //config:       help
  44 //config:       Add support for regular expressions substitutions when renaming
  45 //config:       device.
  46 //config:
  47 //config:config FEATURE_MDEV_EXEC
  48 //config:       bool "Support command execution at device addition/removal"
  49 //config:       default y
  50 //config:       depends on FEATURE_MDEV_CONF
  51 //config:       help
  52 //config:       This adds support for an optional field to /etc/mdev.conf for
  53 //config:       executing commands when devices are created/removed.
  54 //config:
  55 //config:       For more information, please see docs/mdev.txt
  56 //config:
  57 //config:config FEATURE_MDEV_LOAD_FIRMWARE
  58 //config:       bool "Support loading of firmware"
  59 //config:       default y
  60 //config:       depends on MDEV
  61 //config:       help
  62 //config:       Some devices need to load firmware before they can be usable.
  63 //config:
  64 //config:       These devices will request userspace look up the files in
  65 //config:       /lib/firmware/ and if it exists, send it to the kernel for
  66 //config:       loading into the hardware.
  67 //config:
  68 //config:config FEATURE_MDEV_DAEMON
  69 //config:       bool "Support daemon mode"
  70 //config:       default y
  71 //config:       depends on MDEV
  72 //config:       help
  73 //config:       Adds the -d option to run mdev in daemon mode handling hotplug
  74 //config:       events from the kernel like udev. If the system generates many
  75 //config:       hotplug events this mode of operation will consume less
  76 //config:       resources than registering mdev as hotplug helper or using the
  77 //config:       uevent applet.
  78
  79 //applet:IF_MDEV(APPLET(mdev, BB_DIR_SBIN, BB_SUID_DROP))
  80
  81 //kbuild:lib-$(CONFIG_MDEV) += mdev.o
  82
  83 //usage:#define mdev_trivial_usage
  84 //usage:       "[-s]" IF_FEATURE_MDEV_DAEMON(" | [-df]")
  85 //usage:#define mdev_full_usage "\n\n"
  86 //usage:       "mdev -s is to be run during boot to scan /sys and populate /dev.\n"
  87 //usage:        IF_FEATURE_MDEV_DAEMON(
  88 //usage:       "mdev -d[f]: daemon, listen on netlink.\n"
  89 //usage:       "        -f: stay in foreground.\n"
  90 //usage:        )
  91 //usage:       "\n"
  92 //usage:       "Bare mdev is a kernel hotplug helper. To activate it:\n"
  93 //usage:       "        echo /sbin/mdev >/proc/sys/kernel/hotplug\n"
  94 //usage:        IF_FEATURE_MDEV_CONF(
  95 //usage:       "\n"
  96 //usage:       "It uses /etc/mdev.conf with lines\n"
  97 //usage:       "        [-][ENV=regex;]...DEVNAME UID:GID PERM"
  98 //usage:                        IF_FEATURE_MDEV_RENAME(" [>|=PATH]|[!]")
  99 //usage:                        IF_FEATURE_MDEV_EXEC(" [@|$|*PROG]")
 100 //usage:       "\n"
 101 //usage:       "where DEVNAME is device name regex, @major,minor[-minor2], or\n"
 102 //usage:       "environment variable regex. A common use of the latter is\n"
 103 //usage:       "to load modules for hotplugged devices:\n"
 104 //usage:       "        $MODALIAS=.* 0:0 660 @modprobe \"$MODALIAS\"\n"
 105 //usage:        )
 106 //usage:       "\n"
 107 //usage:       "If /dev/mdev.seq file exists, mdev will wait for its value\n"
 108 //usage:       "to match $SEQNUM variable. This prevents plug/unplug races.\n"
 109 //usage:       "To activate this feature, create empty /dev/mdev.seq at boot.\n"
 110 //usage:       "\n"
 111 //usage:       "If /dev/mdev.log file exists, debug log will be appended to it."
 112
 113 #include "libbb.h"
 114 #include "common_bufsiz.h"
 115 #include "xregex.h"
 116 #include <linux/netlink.h>
 117
 118 /* "mdev -s" scans /sys/class/xxx, looking for directories which have dev
 119  * file (it is of the form "M:m\n"). Example: /sys/class/tty/tty0/dev
 120  * contains "4:0\n". Directory name is taken as device name, path component
 121  * directly after /sys/class/ as subsystem. In this example, "tty0" and "tty".
 122  * Then mdev creates the /dev/device_name node.
 123  * If /sys/class/.../dev file does not exist, mdev still may act
 124  * on this device: see "@|$|*command args..." parameter in config file.
 125  *
 126  * mdev w/o parameters is called as hotplug helper. It takes device
 127  * and subsystem names from $DEVPATH and $SUBSYSTEM, extracts
 128  * maj,min from "/sys/$DEVPATH/dev" and also examines
 129  * $ACTION ("add"/"delete") and $FIRMWARE.
 130  *
 131  * If action is "add", mdev creates /dev/device_name similarly to mdev -s.
 132  * (todo: explain "delete" and $FIRMWARE)
 133  *
 134  * If /etc/mdev.conf exists, it may modify /dev/device_name's properties.
 135  *
 136  * Leading minus in 1st field means "don't stop on this line", otherwise
 137  * search is stopped after the matching line is encountered.
 138  *
 139  * $envvar=regex format is useful for loading modules for hot-plugged devices
 140  * which do not have driver loaded yet. In this case /sys/class/.../dev
 141  * does not exist, but $MODALIAS is set to needed module's name
 142  * (actually, an alias to it) by kernel. This rule instructs mdev
 143  * to load the module and exit:
 144  *    $MODALIAS=.* 0:0 660 @modprobe "$MODALIAS"
 145  * The kernel will generate another hotplug event when /sys/class/.../dev
 146  * file appears.
 147  *
 148  * When line matches, the device node is created, chmod'ed and chown'ed,
 149  * moved to path, and if >path, a symlink to moved node is created,
 150  * all this if /sys/class/.../dev exists.
 151  *    Examples:
 152  *    =loop/      - moves to /dev/loop
 153  *    >disk/sda%1 - moves to /dev/disk/sdaN, makes /dev/sdaN a symlink
 154  *
 155  * Then "command args..." is executed (via sh -c 'command args...').
 156  * @:execute on creation, $:on deletion, *:on both.
 157  * This happens regardless of /sys/class/.../dev existence.
 158  */
 159
 160 /* Kernel's hotplug environment constantly changes.
 161  * Here are new cases I observed on 3.1.0:
 162  *
 163  * Case with $DEVNAME and $DEVICE, not just $DEVPATH:
 164  * ACTION=add
 165  * BUSNUM=001
 166  * DEVICE=/proc/bus/usb/001/003
 167  * DEVNAME=bus/usb/001/003
 168  * DEVNUM=003
 169  * DEVPATH=/devices/pci0000:00/0000:00:02.1/usb1/1-5
 170  * DEVTYPE=usb_device
 171  * MAJOR=189
 172  * MINOR=2
 173  * PRODUCT=18d1/4e12/227
 174  * SUBSYSTEM=usb
 175  * TYPE=0/0/0
 176  *
 177  * Case with $DEVICE, but no $DEVNAME - apparenty, usb iface notification?
 178  * "Please load me a module" thing?
 179  * ACTION=add
 180  * DEVICE=/proc/bus/usb/001/003
 181  * DEVPATH=/devices/pci0000:00/0000:00:02.1/usb1/1-5/1-5:1.0
 182  * DEVTYPE=usb_interface
 183  * INTERFACE=8/6/80
 184  * MODALIAS=usb:v18D1p4E12d0227dc00dsc00dp00ic08isc06ip50
 185  * PRODUCT=18d1/4e12/227
 186  * SUBSYSTEM=usb
 187  * TYPE=0/0/0
 188  *
 189  * ACTION=add
 190  * DEVPATH=/devices/pci0000:00/0000:00:02.1/usb1/1-5/1-5:1.0/host5
 191  * DEVTYPE=scsi_host
 192  * SUBSYSTEM=scsi
 193  *
 194  * ACTION=add
 195  * DEVPATH=/devices/pci0000:00/0000:00:02.1/usb1/1-5/1-5:1.0/host5/scsi_host/host5
 196  * SUBSYSTEM=scsi_host
 197  *
 198  * ACTION=add
 199  * DEVPATH=/devices/pci0000:00/0000:00:02.1/usb1/1-5/1-5:1.0/host5/target5:0:0
 200  * DEVTYPE=scsi_target
 201  * SUBSYSTEM=scsi
 202  *
 203  * Case with strange $MODALIAS:
 204  * ACTION=add
 205  * DEVPATH=/devices/pci0000:00/0000:00:02.1/usb1/1-5/1-5:1.0/host5/target5:0:0/5:0:0:0
 206  * DEVTYPE=scsi_device
 207  * MODALIAS=scsi:t-0x00
 208  * SUBSYSTEM=scsi
 209  *
 210  * ACTION=add
 211  * DEVPATH=/devices/pci0000:00/0000:00:02.1/usb1/1-5/1-5:1.0/host5/target5:0:0/5:0:0:0/scsi_disk/5:0:0:0
 212  * SUBSYSTEM=scsi_disk
 213  *
 214  * ACTION=add
 215  * DEVPATH=/devices/pci0000:00/0000:00:02.1/usb1/1-5/1-5:1.0/host5/target5:0:0/5:0:0:0/scsi_device/5:0:0:0
 216  * SUBSYSTEM=scsi_device
 217  *
 218  * Case with explicit $MAJOR/$MINOR (no need to read /sys/$DEVPATH/dev?):
 219  * ACTION=add
 220  * DEVNAME=bsg/5:0:0:0
 221  * DEVPATH=/devices/pci0000:00/0000:00:02.1/usb1/1-5/1-5:1.0/host5/target5:0:0/5:0:0:0/bsg/5:0:0:0
 222  * MAJOR=253
 223  * MINOR=1
 224  * SUBSYSTEM=bsg
 225  *
 226  * ACTION=add
 227  * DEVPATH=/devices/virtual/bdi/8:16
 228  * SUBSYSTEM=bdi
 229  *
 230  * ACTION=add
 231  * DEVNAME=sdb
 232  * DEVPATH=/block/sdb
 233  * DEVTYPE=disk
 234  * MAJOR=8
 235  * MINOR=16
 236  * SUBSYSTEM=block
 237  *
 238  * Case with ACTION=change:
 239  * ACTION=change
 240  * DEVNAME=sdb
 241  * DEVPATH=/block/sdb
 242  * DEVTYPE=disk
 243  * DISK_MEDIA_CHANGE=1
 244  * MAJOR=8
 245  * MINOR=16
 246  * SUBSYSTEM=block
 247  */
 248
 249 #define DEBUG_LVL 2
 250
 251 #if DEBUG_LVL >= 1
 252 # define dbg1(...) do { if (G.verbose) bb_error_msg(__VA_ARGS__); } while(0)
 253 #else
 254 # define dbg1(...) ((void)0)
 255 #endif
 256 #if DEBUG_LVL >= 2
 257 # define dbg2(...) do { if (G.verbose >= 2) bb_error_msg(__VA_ARGS__); } while(0)
 258 #else
 259 # define dbg2(...) ((void)0)
 260 #endif
 261 #if DEBUG_LVL >= 3
 262 # define dbg3(...) do { if (G.verbose >= 3) bb_error_msg(__VA_ARGS__); } while(0)
 263 #else
 264 # define dbg3(...) ((void)0)
 265 #endif
 266
 267
 268 #ifndef SO_RCVBUFFORCE
 269 #define SO_RCVBUFFORCE 33
 270 #endif
 271 static const char keywords[] ALIGN1 = "add\0remove\0"; // "change\0"
 272 enum { OP_add, OP_remove };
 273
 274 struct envmatch {
 275         struct envmatch *next;
 276         char *envname;
 277         regex_t match;
 278 };
 279
 280 struct rule {
 281         bool keep_matching;
 282         bool regex_compiled;
 283         mode_t mode;
 284         int maj, min0, min1;
 285         struct bb_uidgid_t ugid;
 286         char *envvar;
 287         char *ren_mov;
 288         IF_FEATURE_MDEV_EXEC(char *r_cmd;)
 289         regex_t match;
 290         struct envmatch *envmatch;
 291 };
 292
 293 struct globals {
 294         int root_major, root_minor;
 295         smallint verbose;
 296         char *subsystem;
 297         char *subsys_env; /* for putenv("SUBSYSTEM=subsystem") */
 298 #if ENABLE_FEATURE_MDEV_CONF
 299         const char *filename;
 300         parser_t *parser;
 301         struct rule **rule_vec;
 302         unsigned rule_idx;
 303 #endif
 304         struct rule cur_rule;
 305         char timestr[sizeof("HH:MM:SS.123456")];
 306 } FIX_ALIASING;
 307 #define G (*(struct globals*)bb_common_bufsiz1)
 308 #define INIT_G() do { \
 309         setup_common_bufsiz(); \
 310         IF_NOT_FEATURE_MDEV_CONF(G.cur_rule.maj = -1;) \
 311         IF_NOT_FEATURE_MDEV_CONF(G.cur_rule.mode = 0660;) \
 312 } while (0)
 313
 314
 315 /* Prevent infinite loops in /sys symlinks */
 316 #define MAX_SYSFS_DEPTH 3
 317
 318 /* We use additional bytes in make_device() */
 319 #define SCRATCH_SIZE 128
 320
 321 #if ENABLE_FEATURE_MDEV_CONF
 322
 323 static void make_default_cur_rule(void)
 324 {
 325         memset(&G.cur_rule, 0, sizeof(G.cur_rule));
 326         G.cur_rule.maj = -1; /* "not a @major,minor rule" */
 327         G.cur_rule.mode = 0660;
 328 }
 329
 330 static void clean_up_cur_rule(void)
 331 {
 332         struct envmatch *e;
 333
 334         free(G.cur_rule.envvar);
 335         free(G.cur_rule.ren_mov);
 336         if (G.cur_rule.regex_compiled)
 337                 regfree(&G.cur_rule.match);
 338         IF_FEATURE_MDEV_EXEC(free(G.cur_rule.r_cmd);)
 339         e = G.cur_rule.envmatch;
 340         while (e) {
 341                 free(e->envname);
 342                 regfree(&e->match);
 343                 e = e->next;
 344         }
 345         make_default_cur_rule();
 346 }
 347
 348 static char *parse_envmatch_pfx(char *val)
 349 {
 350         struct envmatch **nextp = &G.cur_rule.envmatch;
 351
 352         for (;;) {
 353                 struct envmatch *e;
 354                 char *semicolon;
 355                 char *eq = strchr(val, '=');
 356                 if (!eq /* || eq == val? */)
 357                         return val;
 358                 if (endofname(val) != eq)
 359                         return val;
 360                 semicolon = strchr(eq, ';');
 361                 if (!semicolon)
 362                         return val;
 363                 /* ENVVAR=regex;... */
 364                 *nextp = e = xzalloc(sizeof(*e));
 365                 nextp = &e->next;
 366                 e->envname = xstrndup(val, eq - val);
 367                 *semicolon = '\0';
 368                 xregcomp(&e->match, eq + 1, REG_EXTENDED);
 369                 *semicolon = ';';
 370                 val = semicolon + 1;
 371         }
 372 }
 373
 374 static void parse_next_rule(void)
 375 {
 376         /* Note: on entry, G.cur_rule is set to default */
 377         while (1) {
 378                 char *tokens[4];
 379                 char *val;
 380
 381                 /* No PARSE_EOL_COMMENTS, because command may contain '#' chars */
 382                 if (!config_read(G.parser, tokens, 4, 3, "# \t", PARSE_NORMAL & ~PARSE_EOL_COMMENTS))
 383                         break;
 384
 385                 /* Fields: [-]regex uid:gid mode [alias] [cmd] */
 386                 dbg3("token1:'%s'", tokens[1]);
 387
 388                 /* 1st field */
 389                 val = tokens[0];
 390                 G.cur_rule.keep_matching = ('-' == val[0]);
 391                 val += G.cur_rule.keep_matching; /* swallow leading dash */
 392                 val = parse_envmatch_pfx(val);
 393                 if (val[0] == '@') {
 394                         /* @major,minor[-minor2] */
 395                         /* (useful when name is ambiguous:
 396                          * "/sys/class/usb/lp0" and
 397                          * "/sys/class/printer/lp0")
 398                          */
 399                         int sc = sscanf(val, "@%u,%u-%u", &G.cur_rule.maj, &G.cur_rule.min0, &G.cur_rule.min1);
 400                         if (sc < 2 || G.cur_rule.maj < 0) {
 401                                 bb_error_msg("bad @maj,min on line %d", G.parser->lineno);
 402                                 goto next_rule;
 403                         }
 404                         if (sc == 2)
 405                                 G.cur_rule.min1 = G.cur_rule.min0;
 406                 } else {
 407                         char *eq = strchr(val, '=');
 408                         if (val[0] == '$') {
 409                                 /* $ENVVAR=regex ... */
 410                                 val++;
 411                                 if (!eq) {
 412                                         bb_error_msg("bad $envvar=regex on line %d", G.parser->lineno);
 413                                         goto next_rule;
 414                                 }
 415                                 G.cur_rule.envvar = xstrndup(val, eq - val);
 416                                 val = eq + 1;
 417                         }
 418                         xregcomp(&G.cur_rule.match, val, REG_EXTENDED);
 419                         G.cur_rule.regex_compiled = 1;
 420                 }
 421
 422                 /* 2nd field: uid:gid - device ownership */
 423                 if (get_uidgid(&G.cur_rule.ugid, tokens[1]) == 0) {
 424                         bb_error_msg("unknown user/group '%s' on line %d", tokens[1], G.parser->lineno);
 425                         goto next_rule;
 426                 }
 427
 428                 /* 3rd field: mode - device permissions */
 429                 G.cur_rule.mode = bb_parse_mode(tokens[2], G.cur_rule.mode);
 430
 431                 /* 4th field (opt): ">|=alias" or "!" to not create the node */
 432                 val = tokens[3];
 433                 if (ENABLE_FEATURE_MDEV_RENAME && val && strchr(">=!", val[0])) {
 434                         char *s = skip_non_whitespace(val);
 435                         G.cur_rule.ren_mov = xstrndup(val, s - val);
 436                         val = skip_whitespace(s);
 437                 }
 438
 439                 if (ENABLE_FEATURE_MDEV_EXEC && val && val[0]) {
 440                         const char *s = "$@*";
 441                         const char *s2 = strchr(s, val[0]);
 442                         if (!s2) {
 443                                 bb_error_msg("bad line %u", G.parser->lineno);
 444                                 goto next_rule;
 445                         }
 446                         IF_FEATURE_MDEV_EXEC(G.cur_rule.r_cmd = xstrdup(val);)
 447                 }
 448
 449                 return;
 450  next_rule:
 451                 clean_up_cur_rule();
 452         } /* while (config_read) */
 453
 454         dbg3("config_close(G.parser)");
 455         config_close(G.parser);
 456         G.parser = NULL;
 457
 458         return;
 459 }
 460
 461 /* If mdev -s, we remember rules in G.rule_vec[].
 462  * Otherwise, there is no point in doing it, and we just
 463  * save only one parsed rule in G.cur_rule.
 464  */
 465 static const struct rule *next_rule(void)
 466 {
 467         struct rule *rule;
 468
 469         /* Open conf file if we didn't do it yet */
 470         if (!G.parser && G.filename) {
 471                 dbg3("config_open('%s')", G.filename);
 472                 G.parser = config_open2(G.filename, fopen_for_read);
 473                 G.filename = NULL;
 474         }
 475
 476         if (G.rule_vec) {
 477                 /* mdev -s */
 478                 /* Do we have rule parsed already? */
 479                 if (G.rule_vec[G.rule_idx]) {
 480                         dbg3("< G.rule_vec[G.rule_idx:%d]=%p", G.rule_idx, G.rule_vec[G.rule_idx]);
 481                         return G.rule_vec[G.rule_idx++];
 482                 }
 483                 make_default_cur_rule();
 484         } else {
 485                 /* not mdev -s */
 486                 clean_up_cur_rule();
 487         }
 488
 489         /* Parse one more rule if file isn't fully read */
 490         rule = &G.cur_rule;
 491         if (G.parser) {
 492                 parse_next_rule();
 493                 if (G.rule_vec) { /* mdev -s */
 494                         rule = xmemdup(&G.cur_rule, sizeof(G.cur_rule));
 495                         G.rule_vec = xrealloc_vector(G.rule_vec, 4, G.rule_idx);
 496                         G.rule_vec[G.rule_idx++] = rule;
 497                         dbg3("> G.rule_vec[G.rule_idx:%d]=%p", G.rule_idx, G.rule_vec[G.rule_idx]);
 498                 }
 499         }
 500
 501         return rule;
 502 }
 503
 504 static int env_matches(struct envmatch *e)
 505 {
 506         while (e) {
 507                 int r;
 508                 char *val = getenv(e->envname);
 509                 if (!val)
 510                         return 0;
 511                 r = regexec(&e->match, val, /*size*/ 0, /*range[]*/ NULL, /*eflags*/ 0);
 512                 if (r != 0) /* no match */
 513                         return 0;
 514                 e = e->next;
 515         }
 516         return 1;
 517 }
 518
 519 #else
 520
 521 # define next_rule() (&G.cur_rule)
 522
 523 #endif
 524
 525 static void mkdir_recursive(char *name)
 526 {
 527         /* if name has many levels ("dir1/dir2"),
 528          * bb_make_directory() will create dir1 according to umask,
 529          * not according to its "mode" parameter.
 530          * Since we run with umask=0, need to temporarily switch it.
 531          */
 532         umask(022); /* "dir1" (if any) will be 0755 too */
 533         bb_make_directory(name, 0755, FILEUTILS_RECUR);
 534         umask(0);
 535 }
 536
 537 /* Builds an alias path.
 538  * This function potentionally reallocates the alias parameter.
 539  * Only used for ENABLE_FEATURE_MDEV_RENAME
 540  */
 541 static char *build_alias(char *alias, const char *device_name)
 542 {
 543         char *dest;
 544
 545         /* ">bar/": rename to bar/device_name */
 546         /* ">bar[/]baz": rename to bar[/]baz */
 547         dest = strrchr(alias, '/');
 548         if (dest) { /* ">bar/[baz]" ? */
 549                 *dest = '\0'; /* mkdir bar */
 550                 mkdir_recursive(alias);
 551                 *dest = '/';
 552                 if (dest[1] == '\0') { /* ">bar/" => ">bar/device_name" */
 553                         dest = alias;
 554                         alias = concat_path_file(alias, device_name);
 555                         free(dest);
 556                 }
 557         }
 558
 559         return alias;
 560 }
 561
 562 /* mknod in /dev based on a path like "/sys/block/hda/hda1"
 563  * NB1: path parameter needs to have SCRATCH_SIZE scratch bytes
 564  * after NUL, but we promise to not mangle it (IOW: to restore NUL if needed).
 565  * NB2: "mdev -s" may call us many times, do not leak memory/fds!
 566  *
 567  * device_name = $DEVNAME (may be NULL)
 568  * path        = /sys/$DEVPATH
 569  */
 570 static void make_device(char *device_name, char *path, int operation)
 571 {
 572         int major, minor, type, len;
 573         char *path_end = path + strlen(path);
 574
 575         /* Try to read major/minor string.  Note that the kernel puts \n after
 576          * the data, so we don't need to worry about null terminating the string
 577          * because sscanf() will stop at the first nondigit, which \n is.
 578          * We also depend on path having writeable space after it.
 579          */
 580         major = -1;
 581         if (operation == OP_add) {
 582                 strcpy(path_end, "/dev");
 583                 len = open_read_close(path, path_end + 1, SCRATCH_SIZE - 1);
 584                 *path_end = '\0';
 585                 if (len < 1) {
 586                         if (!ENABLE_FEATURE_MDEV_EXEC)
 587                                 return;
 588                         /* no "dev" file, but we can still run scripts
 589                          * based on device name */
 590                 } else if (sscanf(path_end + 1, "%u:%u", &major, &minor) == 2) {
 591                         dbg1("dev %u,%u", major, minor);
 592                 } else {
 593                         major = -1;
 594                 }
 595         }
 596         /* else: for delete, -1 still deletes the node, but < -1 suppresses that */
 597
 598         /* Determine device name */
 599         if (!device_name) {
 600                 /*
 601                  * There was no $DEVNAME envvar (for example, mdev -s never has).
 602                  * But it is very useful: it contains the *path*, not only basename,
 603                  * Thankfully, uevent file has it.
 604                  * Example of .../sound/card0/controlC0/uevent file on Linux-3.7.7:
 605                  * MAJOR=116
 606                  * MINOR=7
 607                  * DEVNAME=snd/controlC0
 608                  */
 609                 strcpy(path_end, "/uevent");
 610                 len = open_read_close(path, path_end + 1, SCRATCH_SIZE - 1);
 611                 if (len < 0)
 612                         len = 0;
 613                 *path_end = '\0';
 614                 path_end[1 + len] = '\0';
 615                 device_name = strstr(path_end + 1, "\nDEVNAME=");
 616                 if (device_name) {
 617                         device_name += sizeof("\nDEVNAME=")-1;
 618                         strchrnul(device_name, '\n')[0] = '\0';
 619                 } else {
 620                         /* Fall back to just basename */
 621                         device_name = (char*) bb_basename(path);
 622                 }
 623         }
 624         /* Determine device type */
 625         /*
 626          * http://kernel.org/doc/pending/hotplug.txt says that only
 627          * "/sys/block/..." is for block devices. "/sys/bus" etc is not.
 628          * But since 2.6.25 block devices are also in /sys/class/block.
 629          * We use strstr("/block/") to forestall future surprises.
 630          */
 631         type = S_IFCHR;
 632         if (strstr(path, "/block/") || (G.subsystem && is_prefixed_with(G.subsystem, "block")))
 633                 type = S_IFBLK;
 634
 635 #if ENABLE_FEATURE_MDEV_CONF
 636         G.rule_idx = 0; /* restart from the beginning (think mdev -s) */
 637 #endif
 638         for (;;) {
 639                 const char *str_to_match;
 640                 regmatch_t off[1 + 9 * ENABLE_FEATURE_MDEV_RENAME_REGEXP];
 641                 char *command;
 642                 char *alias;
 643                 char aliaslink = aliaslink; /* for compiler */
 644                 char *node_name;
 645                 const struct rule *rule;
 646
 647                 str_to_match = device_name;
 648
 649                 rule = next_rule();
 650
 651 #if ENABLE_FEATURE_MDEV_CONF
 652                 if (!env_matches(rule->envmatch))
 653                         continue;
 654                 if (rule->maj >= 0) {  /* @maj,min rule */
 655                         if (major != rule->maj)
 656                                 continue;
 657                         if (minor < rule->min0 || minor > rule->min1)
 658                                 continue;
 659                         memset(off, 0, sizeof(off));
 660                         goto rule_matches;
 661                 }
 662                 if (rule->envvar) { /* $envvar=regex rule */
 663                         str_to_match = getenv(rule->envvar);
 664                         dbg3("getenv('%s'):'%s'", rule->envvar, str_to_match);
 665                         if (!str_to_match)
 666                                 continue;
 667                 }
 668                 /* else: str_to_match = device_name */
 669
 670                 if (rule->regex_compiled) {
 671                         int regex_match = regexec(&rule->match, str_to_match, ARRAY_SIZE(off), off, 0);
 672                         dbg3("regex_match for '%s':%d", str_to_match, regex_match);
 673                         //bb_error_msg("matches:");
 674                         //for (int i = 0; i < ARRAY_SIZE(off); i++) {
 675                         //      if (off[i].rm_so < 0) continue;
 676                         //      bb_error_msg("match %d: '%.*s'\n", i,
 677                         //              (int)(off[i].rm_eo - off[i].rm_so),
 678                         //              device_name + off[i].rm_so);
 679                         //}
 680
 681                         if (regex_match != 0
 682                         /* regexec returns whole pattern as "range" 0 */
 683                          || off[0].rm_so != 0
 684                          || (int)off[0].rm_eo != (int)strlen(str_to_match)
 685                         ) {
 686                                 continue; /* this rule doesn't match */
 687                         }
 688                 }
 689                 /* else: it's final implicit "match-all" rule */
 690  rule_matches:
 691                 dbg2("rule matched, line %d", G.parser ? G.parser->lineno : -1);
 692 #endif
 693                 /* Build alias name */
 694                 alias = NULL;
 695                 if (ENABLE_FEATURE_MDEV_RENAME && rule->ren_mov) {
 696                         aliaslink = rule->ren_mov[0];
 697                         if (aliaslink == '!') {
 698                                 /* "!": suppress node creation/deletion */
 699                                 major = -2;
 700                         }
 701                         else if (aliaslink == '>' || aliaslink == '=') {
 702                                 if (ENABLE_FEATURE_MDEV_RENAME_REGEXP) {
 703                                         char *s;
 704                                         char *p;
 705                                         unsigned n;
 706
 707                                         /* substitute %1..9 with off[1..9], if any */
 708                                         n = 0;
 709                                         s = rule->ren_mov;
 710                                         while (*s)
 711                                                 if (*s++ == '%')
 712                                                         n++;
 713
 714                                         p = alias = xzalloc(strlen(rule->ren_mov) + n * strlen(str_to_match));
 715                                         s = rule->ren_mov + 1;
 716                                         while (*s) {
 717                                                 *p = *s;
 718                                                 if ('%' == *s) {
 719                                                         unsigned i = (s[1] - '0');
 720                                                         if (i <= 9 && off[i].rm_so >= 0) {
 721                                                                 n = off[i].rm_eo - off[i].rm_so;
 722                                                                 strncpy(p, str_to_match + off[i].rm_so, n);
 723                                                                 p += n - 1;
 724                                                                 s++;
 725                                                         }
 726                                                 }
 727                                                 p++;
 728                                                 s++;
 729                                         }
 730                                 } else {
 731                                         alias = xstrdup(rule->ren_mov + 1);
 732                                 }
 733                         }
 734                 }
 735                 dbg3("alias:'%s'", alias);
 736
 737                 command = NULL;
 738                 IF_FEATURE_MDEV_EXEC(command = rule->r_cmd;)
 739                 if (command) {
 740                         /* Are we running this command now?
 741                          * Run @cmd on create, $cmd on delete, *cmd on any
 742                          */
 743                         if ((command[0] == '@' && operation == OP_add)
 744                          || (command[0] == '$' && operation == OP_remove)
 745                          || (command[0] == '*')
 746                         ) {
 747                                 command++;
 748                         } else {
 749                                 command = NULL;
 750                         }
 751                 }
 752                 dbg3("command:'%s'", command);
 753
 754                 /* "Execute" the line we found */
 755                 node_name = device_name;
 756                 if (ENABLE_FEATURE_MDEV_RENAME && alias) {
 757                         node_name = alias = build_alias(alias, device_name);
 758                         dbg3("alias2:'%s'", alias);
 759                 }
 760
 761                 if (operation == OP_add && major >= 0) {
 762                         char *slash = strrchr(node_name, '/');
 763                         if (slash) {
 764                                 *slash = '\0';
 765                                 mkdir_recursive(node_name);
 766                                 *slash = '/';
 767                         }
 768                         if (ENABLE_FEATURE_MDEV_CONF) {
 769                                 dbg1("mknod %s (%d,%d) %o"
 770                                         " %u:%u",
 771                                         node_name, major, minor, rule->mode | type,
 772                                         rule->ugid.uid, rule->ugid.gid
 773                                 );
 774                         } else {
 775                                 dbg1("mknod %s (%d,%d) %o",
 776                                         node_name, major, minor, rule->mode | type
 777                                 );
 778                         }
 779                         if (mknod(node_name, rule->mode | type, makedev(major, minor)) && errno != EEXIST)
 780                                 bb_perror_msg("can't create '%s'", node_name);
 781                         if (ENABLE_FEATURE_MDEV_CONF) {
 782                                 chmod(node_name, rule->mode);
 783                                 chown(node_name, rule->ugid.uid, rule->ugid.gid);
 784                         }
 785                         if (major == G.root_major && minor == G.root_minor)
 786                                 symlink(node_name, "root");
 787                         if (ENABLE_FEATURE_MDEV_RENAME && alias) {
 788                                 if (aliaslink == '>') {
 789 //TODO: on devtmpfs, device_name already exists and symlink() fails.
 790 //End result is that instead of symlink, we have two nodes.
 791 //What should be done?
 792                                         dbg1("symlink: %s", device_name);
 793                                         symlink(node_name, device_name);
 794                                 }
 795                         }
 796                 }
 797
 798                 if (ENABLE_FEATURE_MDEV_EXEC && command) {
 799                         /* setenv will leak memory, use putenv/unsetenv/free */
 800                         char *s = xasprintf("%s=%s", "MDEV", node_name);
 801                         putenv(s);
 802                         dbg1("running: %s", command);
 803                         if (system(command) == -1)
 804                                 bb_perror_msg("can't run '%s'", command);
 805                         bb_unsetenv_and_free(s);
 806                 }
 807
 808                 if (operation == OP_remove && major >= -1) {
 809                         if (ENABLE_FEATURE_MDEV_RENAME && alias) {
 810                                 if (aliaslink == '>') {
 811                                         dbg1("unlink: %s", device_name);
 812                                         unlink(device_name);
 813                                 }
 814                         }
 815                         dbg1("unlink: %s", node_name);
 816                         unlink(node_name);
 817                 }
 818
 819                 if (ENABLE_FEATURE_MDEV_RENAME)
 820                         free(alias);
 821
 822                 /* We found matching line.
 823                  * Stop unless it was prefixed with '-'
 824                  */
 825                 if (!ENABLE_FEATURE_MDEV_CONF || !rule->keep_matching)
 826                         break;
 827         } /* for (;;) */
 828 }
 829
 830 static ssize_t readlink2(char *buf, size_t bufsize)
 831 {
 832         // Grr... gcc 8.1.1:
 833         // "passing argument 2 to restrict-qualified parameter aliases with argument 1"
 834         // dance around that...
 835         char *obuf FIX_ALIASING;
 836         obuf = buf;
 837         return readlink(buf, obuf, bufsize);
 838 }
 839
 840 /* File callback for /sys/ traversal.
 841  * We act only on "/sys/.../dev" (pseudo)file
 842  */
 843 static int FAST_FUNC fileAction(const char *fileName,
 844                 struct stat *statbuf UNUSED_PARAM,
 845                 void *userData,
 846                 int depth UNUSED_PARAM)
 847 {
 848         size_t len = strlen(fileName) - 4; /* can't underflow */
 849         char *path = userData;  /* char array[PATH_MAX + SCRATCH_SIZE] */
 850         char subsys[PATH_MAX];
 851         int res;
 852
 853         /* Is it a ".../dev" file? (len check is for paranoid reasons) */
 854         if (strcmp(fileName + len, "/dev") != 0 || len >= PATH_MAX - 32)
 855                 return FALSE; /* not .../dev */
 856
 857         strcpy(path, fileName);
 858         path[len] = '\0';
 859
 860         /* Read ".../subsystem" symlink in the same directory where ".../dev" is */
 861         strcpy(subsys, path);
 862         strcpy(subsys + len, "/subsystem");
 863         res = readlink2(subsys, sizeof(subsys)-1);
 864         if (res > 0) {
 865                 subsys[res] = '\0';
 866                 free(G.subsystem);
 867                 if (G.subsys_env) {
 868                         bb_unsetenv_and_free(G.subsys_env);
 869                         G.subsys_env = NULL;
 870                 }
 871                 /* Set G.subsystem and $SUBSYSTEM from symlink's last component */
 872                 G.subsystem = strrchr(subsys, '/');
 873                 if (G.subsystem) {
 874                         G.subsystem = xstrdup(G.subsystem + 1);
 875                         G.subsys_env = xasprintf("%s=%s", "SUBSYSTEM", G.subsystem);
 876                         putenv(G.subsys_env);
 877                 }
 878         }
 879
 880         make_device(/*DEVNAME:*/ NULL, path, OP_add);
 881
 882         return TRUE;
 883 }
 884
 885 /* Directory callback for /sys/ traversal */
 886 static int FAST_FUNC dirAction(const char *fileName UNUSED_PARAM,
 887                 struct stat *statbuf UNUSED_PARAM,
 888                 void *userData UNUSED_PARAM,
 889                 int depth)
 890 {
 891         return (depth >= MAX_SYSFS_DEPTH ? SKIP : TRUE);
 892 }
 893
 894 /* For the full gory details, see linux/Documentation/firmware_class/README
 895  *
 896  * Firmware loading works like this:
 897  * - kernel sets FIRMWARE env var
 898  * - userspace checks /lib/firmware/$FIRMWARE
 899  * - userspace waits for /sys/$DEVPATH/loading to appear
 900  * - userspace writes "1" to /sys/$DEVPATH/loading
 901  * - userspace copies /lib/firmware/$FIRMWARE into /sys/$DEVPATH/data
 902  * - userspace writes "0" (worked) or "-1" (failed) to /sys/$DEVPATH/loading
 903  * - kernel loads firmware into device
 904  */
 905 static void load_firmware(const char *firmware, const char *sysfs_path)
 906 {
 907         int cnt;
 908         int firmware_fd, loading_fd;
 909
 910         /* check for /lib/firmware/$FIRMWARE */
 911         firmware_fd = -1;
 912         if (chdir("/lib/firmware") == 0)
 913                 firmware_fd = open(firmware, O_RDONLY); /* can fail */
 914
 915         /* check for /sys/$DEVPATH/loading ... give 30 seconds to appear */
 916         xchdir(sysfs_path);
 917         for (cnt = 0; cnt < 30; ++cnt) {
 918                 loading_fd = open("loading", O_WRONLY);
 919                 if (loading_fd >= 0)
 920                         goto loading;
 921                 sleep(1);
 922         }
 923         goto out;
 924
 925  loading:
 926         cnt = 0;
 927         if (firmware_fd >= 0) {
 928                 int data_fd;
 929
 930                 /* tell kernel we're loading by "echo 1 > /sys/$DEVPATH/loading" */
 931                 if (full_write(loading_fd, "1", 1) != 1)
 932                         goto out;
 933
 934                 /* load firmware into /sys/$DEVPATH/data */
 935                 data_fd = open("data", O_WRONLY);
 936                 if (data_fd < 0)
 937                         goto out;
 938                 cnt = bb_copyfd_eof(firmware_fd, data_fd);
 939                 if (ENABLE_FEATURE_CLEAN_UP)
 940                         close(data_fd);
 941         }
 942
 943         /* Tell kernel result by "echo [0|-1] > /sys/$DEVPATH/loading"
 944          * Note: we emit -1 also if firmware file wasn't found.
 945          * There are cases when otherwise kernel would wait for minutes
 946          * before timing out.
 947          */
 948         if (cnt > 0)
 949                 full_write(loading_fd, "0", 1);
 950         else
 951                 full_write(loading_fd, "-1", 2);
 952
 953  out:
 954         xchdir("/dev");
 955         if (ENABLE_FEATURE_CLEAN_UP) {
 956                 close(firmware_fd);
 957                 close(loading_fd);
 958         }
 959 }
 960
 961 static char *curtime(void)
 962 {
 963         struct timeval tv;
 964         gettimeofday(&tv, NULL);
 965         sprintf(
 966                 strftime_HHMMSS(G.timestr, sizeof(G.timestr), &tv.tv_sec),
 967                 ".%06u",
 968                 (unsigned)tv.tv_usec
 969         );
 970         return G.timestr;
 971 }
 972
 973 static void open_mdev_log(const char *seq, unsigned my_pid)
 974 {
 975         int logfd = open("mdev.log", O_WRONLY | O_APPEND);
 976         if (logfd >= 0) {
 977                 xmove_fd(logfd, STDERR_FILENO);
 978                 G.verbose = 2;
 979                 applet_name = xasprintf("%s[%s]", applet_name, seq ? seq : utoa(my_pid));
 980         }
 981 }
 982
 983 /* If it exists, does /dev/mdev.seq match $SEQNUM?
 984  * If it does not match, earlier mdev is running
 985  * in parallel, and we need to wait.
 986  * Active mdev pokes us with SIGCHLD to check the new file.
 987  */
 988 static int
 989 wait_for_seqfile(unsigned expected_seq)
 990 {
 991         /* We time out after 2 sec */
 992         static const struct timespec ts = { 0, 32*1000*1000 };
 993         int timeout = 2000 / 32;
 994         int seq_fd = -1;
 995         int do_once = 1;
 996         sigset_t set_CHLD;
 997
 998         sigemptyset(&set_CHLD);
 999         sigaddset(&set_CHLD, SIGCHLD);
1000         sigprocmask(SIG_BLOCK, &set_CHLD, NULL);
1001
1002         for (;;) {
1003                 int seqlen;
1004                 char seqbuf[sizeof(long)*3 + 2];
1005                 unsigned seqbufnum;
1006
1007                 if (seq_fd < 0) {
1008                         seq_fd = open("mdev.seq", O_RDWR);
1009                         if (seq_fd < 0)
1010                                 break;
1011                         close_on_exec_on(seq_fd);
1012                 }
1013                 seqlen = pread(seq_fd, seqbuf, sizeof(seqbuf) - 1, 0);
1014                 if (seqlen < 0) {
1015                         close(seq_fd);
1016                         seq_fd = -1;
1017                         break;
1018                 }
1019                 seqbuf[seqlen] = '\0';
1020                 if (seqbuf[0] == '\n' || seqbuf[0] == '\0') {
1021                         /* seed file: write out seq ASAP */
1022                         xwrite_str(seq_fd, utoa(expected_seq));
1023                         xlseek(seq_fd, 0, SEEK_SET);
1024                         dbg2("first seq written");
1025                         break;
1026                 }
1027                 seqbufnum = atoll(seqbuf);
1028                 if (seqbufnum == expected_seq) {
1029                         /* correct idx */
1030                         break;
1031                 }
1032                 if (seqbufnum > expected_seq) {
1033                         /* a later mdev runs already (this was seen by users to happen) */
1034                         /* do not overwrite seqfile on exit */
1035                         close(seq_fd);
1036                         seq_fd = -1;
1037                         break;
1038                 }
1039                 if (do_once) {
1040                         dbg2("%s mdev.seq='%s', need '%u'", curtime(), seqbuf, expected_seq);
1041                         do_once = 0;
1042                 }
1043                 if (sigtimedwait(&set_CHLD, NULL, &ts) >= 0) {
1044                         dbg3("woken up");
1045                         continue; /* don't decrement timeout! */
1046                 }
1047                 if (--timeout == 0) {
1048                         dbg1("%s mdev.seq='%s'", "timed out", seqbuf);
1049                         break;
1050                 }
1051         }
1052         sigprocmask(SIG_UNBLOCK, &set_CHLD, NULL);
1053         return seq_fd;
1054 }
1055
1056 static void signal_mdevs(unsigned my_pid)
1057 {
1058         procps_status_t* p = NULL;
1059         while ((p = procps_scan(p, PSSCAN_ARGV0)) != NULL) {
1060                 if (p->pid != my_pid
1061                  && p->argv0
1062                  && strcmp(bb_basename(p->argv0), "mdev") == 0
1063                 ) {
1064                         kill(p->pid, SIGCHLD);
1065                 }
1066         }
1067 }
1068
1069 static void process_action(char *temp, unsigned my_pid)
1070 {
1071         char *fw;
1072         char *seq;
1073         char *action;
1074         char *env_devname;
1075         char *env_devpath;
1076         unsigned seqnum = seqnum; /* for compiler */
1077         int seq_fd;
1078         smalluint op;
1079
1080         /* Hotplug:
1081          * env ACTION=... DEVPATH=... SUBSYSTEM=... [SEQNUM=...] mdev
1082          * ACTION can be "add", "remove", "change"
1083          * DEVPATH is like "/block/sda" or "/class/input/mice"
1084          */
1085         env_devname = getenv("DEVNAME"); /* can be NULL */
1086         G.subsystem = getenv("SUBSYSTEM");
1087         action = getenv("ACTION");
1088         env_devpath = getenv("DEVPATH");
1089         if (!action || !env_devpath /*|| !G.subsystem*/)
1090                 bb_show_usage();
1091         fw = getenv("FIRMWARE");
1092         seq = getenv("SEQNUM");
1093         op = index_in_strings(keywords, action);
1094
1095         if (my_pid)
1096                 open_mdev_log(seq, my_pid);
1097
1098         seq_fd = -1;
1099         if (my_pid && seq) {
1100                 seqnum = atoll(seq);
1101                 seq_fd = wait_for_seqfile(seqnum);
1102         }
1103
1104         dbg1("%s "
1105                 "ACTION:%s SEQNUM:%s SUBSYSTEM:%s DEVNAME:%s DEVPATH:%s"
1106                 "%s%s",
1107                 curtime(),
1108                 action, seq, G.subsystem, env_devname, env_devpath,
1109                 fw ? " FW:" : "", fw ? fw : ""
1110         );
1111
1112         snprintf(temp, PATH_MAX, "/sys%s", env_devpath);
1113         if (op == OP_remove) {
1114                 /* Ignoring "remove firmware". It was reported
1115                  * to happen and to cause erroneous deletion
1116                  * of device nodes. */
1117                 if (!fw)
1118                         make_device(env_devname, temp, op);
1119         }
1120         else {
1121                 make_device(env_devname, temp, op);
1122                 if (ENABLE_FEATURE_MDEV_LOAD_FIRMWARE) {
1123                         if (op == OP_add && fw)
1124                                 load_firmware(fw, temp);
1125                 }
1126         }
1127
1128         if (seq_fd >= 0) {
1129                 xwrite_str(seq_fd, utoa(seqnum + 1));
1130                 signal_mdevs(my_pid);
1131         }
1132 }
1133
1134 static void initial_scan(char *temp)
1135 {
1136         struct stat st;
1137
1138         xstat("/", &st);
1139         G.root_major = major(st.st_dev);
1140         G.root_minor = minor(st.st_dev);
1141
1142         putenv((char*)"ACTION=add");
1143
1144         /* Create all devices from /sys/dev hierarchy */
1145         recursive_action("/sys/dev",
1146                          ACTION_RECURSE | ACTION_FOLLOWLINKS,
1147                          fileAction, dirAction, temp, 0);
1148 }
1149
1150 #if ENABLE_FEATURE_MDEV_DAEMON
1151
1152 /* uevent applet uses 16k buffer, and mmaps it before every read */
1153 # define BUFFER_SIZE (2 * 1024)
1154 # define RCVBUF (2 * 1024 * 1024)
1155 # define MAX_ENV 32
1156
1157 static void daemon_loop(char *temp, int fd)
1158 {
1159         for (;;) {
1160                 char netbuf[BUFFER_SIZE];
1161                 char *env[MAX_ENV];
1162                 char *s, *end;
1163                 ssize_t len;
1164                 int idx;
1165
1166                 len = safe_read(fd, netbuf, sizeof(netbuf) - 1);
1167                 if (len < 0) {
1168                         bb_perror_msg_and_die("read");
1169                 }
1170                 end = netbuf + len;
1171                 *end = '\0';
1172
1173                 idx = 0;
1174                 s = netbuf;
1175                 while (s < end && idx < MAX_ENV) {
1176                         if (endofname(s)[0] == '=') {
1177                                 env[idx++] = s;
1178                                 putenv(s);
1179                         }
1180                         s += strlen(s) + 1;
1181                 }
1182
1183                 process_action(temp, 0);
1184
1185                 while (idx)
1186                         bb_unsetenv(env[--idx]);
1187         }
1188 }
1189 #endif
1190
1191 int mdev_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
1192 int mdev_main(int argc UNUSED_PARAM, char **argv)
1193 {
1194         enum {
1195                 MDEV_OPT_SCAN       = 1 << 0,
1196                 MDEV_OPT_DAEMON     = 1 << 1,
1197                 MDEV_OPT_FOREGROUND = 1 << 2,
1198         };
1199         int opt;
1200         RESERVE_CONFIG_BUFFER(temp, PATH_MAX + SCRATCH_SIZE);
1201
1202         INIT_G();
1203
1204         /* We can be called as hotplug helper */
1205         /* Kernel cannot provide suitable stdio fds for us, do it ourself */
1206         bb_sanitize_stdio();
1207
1208         /* Force the configuration file settings exactly */
1209         umask(0);
1210
1211         xchdir("/dev");
1212
1213         opt = getopt32(argv, "s" IF_FEATURE_MDEV_DAEMON("df"));
1214
1215 #if ENABLE_FEATURE_MDEV_CONF
1216         G.filename = "/etc/mdev.conf";
1217         if (opt & (MDEV_OPT_SCAN|MDEV_OPT_DAEMON)) {
1218                 /* Same as xrealloc_vector(NULL, 4, 0): */
1219                 G.rule_vec = xzalloc((1 << 4) * sizeof(*G.rule_vec));
1220         }
1221 #endif
1222
1223 #if ENABLE_FEATURE_MDEV_DAEMON
1224         if (opt & MDEV_OPT_DAEMON) {
1225                 /*
1226                  * Daemon mode listening on uevent netlink socket.
1227                  */
1228                 struct sockaddr_nl sa;
1229                 int fd;
1230
1231 //TODO: reuse same code in uevent
1232                 // Subscribe for UEVENT kernel messages
1233                 sa.nl_family = AF_NETLINK;
1234                 sa.nl_pad = 0;
1235                 sa.nl_pid = getpid();
1236                 sa.nl_groups = 1 << 0;
1237                 fd = xsocket(AF_NETLINK, SOCK_DGRAM, NETLINK_KOBJECT_UEVENT);
1238                 xbind(fd, (struct sockaddr *) &sa, sizeof(sa));
1239                 close_on_exec_on(fd);
1240
1241                 // Without a sufficiently big RCVBUF, a ton of simultaneous events
1242                 // can trigger ENOBUFS on read, which is unrecoverable.
1243                 // Reproducer:
1244                 //      mdev -d
1245                 //      find /sys -name uevent -exec sh -c 'echo add >"{}"' ';'
1246                 //
1247                 // SO_RCVBUFFORCE (root only) can go above net.core.rmem_max sysctl
1248                 setsockopt_SOL_SOCKET_int(fd, SO_RCVBUF,      RCVBUF);
1249                 setsockopt_SOL_SOCKET_int(fd, SO_RCVBUFFORCE, RCVBUF);
1250
1251                 /*
1252                  * Make inital scan after the uevent socket is alive and
1253                  * _before_ we fork away.
1254                  */
1255                 initial_scan(temp);
1256
1257                 if (!(opt & MDEV_OPT_FOREGROUND))
1258                         bb_daemonize_or_rexec(0, argv);
1259
1260                 open_mdev_log(NULL, getpid());
1261
1262                 daemon_loop(temp, fd);
1263         }
1264 #endif
1265         if (opt & MDEV_OPT_SCAN) {
1266                 /*
1267                  * Scan: mdev -s
1268                  */
1269                 initial_scan(temp);
1270         } else {
1271                 process_action(temp, getpid());
1272
1273                 dbg1("%s exiting", curtime());
1274         }
1275
1276         if (ENABLE_FEATURE_CLEAN_UP)
1277                 RELEASE_CONFIG_BUFFER(temp);
1278
1279         return EXIT_SUCCESS;
1280 }