util-linux/mdev.c

   1 /* vi: set sw=4 ts=4: */
   2 /*
   3  *
   4  * mdev - Mini udev for busybox
   5  *
   6  * Copyright 2005 Rob Landley <rob@landley.net>
   7  * Copyright 2005 Frank Sorenson <frank@tuxrocks.com>
   8  *
   9  * Licensed under GPL version 2, see file LICENSE in this tarball for details.
  10  */
  11
  12 #include "libbb.h"
  13 #include "xregex.h"
  14
  15 struct globals {
  16         int root_major, root_minor;
  17 };
  18 #define G (*(struct globals*)&bb_common_bufsiz1)
  19 #define root_major (G.root_major)
  20 #define root_minor (G.root_minor)
  21
  22 #define MAX_SYSFS_DEPTH 3 /* prevent infinite loops in /sys symlinks */
  23
  24 /* We use additional 64+ bytes in make_device() */
  25 #define SCRATCH_SIZE 80
  26
  27 static char *next_field(char *s)
  28 {
  29         char *end = skip_non_whitespace(s);
  30         s = skip_whitespace(end);
  31         *end = '\0';
  32         if (*s == '\0')
  33                 s = NULL;
  34         return s;
  35 }
  36
  37 /* mknod in /dev based on a path like "/sys/block/hda/hda1" */
  38 /* NB: "mdev -s" may call us many times, do not leak memory/fds! */
  39 static void make_device(char *path, int delete)
  40 {
  41         const char *device_name;
  42         int major, minor, type, len;
  43         int mode = 0660;
  44         uid_t uid = 0;
  45         gid_t gid = 0;
  46         char *dev_maj_min = path + strlen(path);
  47         char *command = NULL;
  48         char *alias = NULL;
  49
  50         /* Force the configuration file settings exactly. */
  51         umask(0);
  52
  53         /* Try to read major/minor string.  Note that the kernel puts \n after
  54          * the data, so we don't need to worry about null terminating the string
  55          * because sscanf() will stop at the first nondigit, which \n is.  We
  56          * also depend on path having writeable space after it.
  57          */
  58         if (!delete) {
  59                 strcpy(dev_maj_min, "/dev");
  60                 len = open_read_close(path, dev_maj_min + 1, 64);
  61                 *dev_maj_min++ = '\0';
  62                 if (len < 1) {
  63                         if (!ENABLE_FEATURE_MDEV_EXEC)
  64                                 return;
  65                         /* no "dev" file, so just try to run script */
  66                         *dev_maj_min = '\0';
  67                 }
  68         }
  69
  70         /* Determine device name, type, major and minor */
  71         device_name = bb_basename(path);
  72         /* http://kernel.org/doc/pending/hotplug.txt says that only
  73          * "/sys/block/..." is for block devices. "sys/bus" etc is not! */
  74         type = (strncmp(&path[5], "block/", 6) == 0 ? S_IFBLK : S_IFCHR);
  75
  76         if (ENABLE_FEATURE_MDEV_CONF) {
  77                 FILE *fp;
  78                 char *line, *val, *next;
  79                 unsigned lineno = 0;
  80
  81                 /* If we have config file, look up user settings */
  82                 fp = fopen_or_warn("/etc/mdev.conf", "r");
  83                 if (!fp)
  84                         goto end_parse;
  85
  86                 while ((line = xmalloc_fgetline(fp)) != NULL) {
  87                         ++lineno;
  88                         trim(line);
  89                         if (!line[0])
  90                                 goto next_line;
  91
  92                         /* Fields: regex uid:gid mode [alias] [cmd] */
  93
  94                         /* 1st field: regex to match this device */
  95                         next = next_field(line);
  96                         {
  97                                 regex_t match;
  98                                 regmatch_t off;
  99                                 int result;
 100
 101                                 /* Is this it? */
 102                                 xregcomp(&match, line, REG_EXTENDED);
 103                                 result = regexec(&match, device_name, 1, &off, 0);
 104                                 regfree(&match);
 105
 106                                 /* If not this device, skip rest of line */
 107                                 if (result || off.rm_so || off.rm_eo != strlen(device_name))
 108                                         goto next_line;
 109                         }
 110
 111                         /* This line matches: stop parsing the file
 112                          * after parsing the rest of fields */
 113
 114                         /* 2nd field: uid:gid - device ownership */
 115                         if (!next) /* field must exist */
 116                                 bb_error_msg_and_die("bad line %u", lineno);
 117                         val = next;
 118                         next = next_field(val);
 119                         {
 120                                 struct passwd *pass;
 121                                 struct group *grp;
 122                                 char *str_uid = val;
 123                                 char *str_gid = strchrnul(val, ':');
 124
 125                                 if (*str_gid)
 126                                         *str_gid++ = '\0';
 127                                 /* Parse UID */
 128                                 pass = getpwnam(str_uid);
 129                                 if (pass)
 130                                         uid = pass->pw_uid;
 131                                 else
 132                                         uid = strtoul(str_uid, NULL, 10);
 133                                 /* Parse GID */
 134                                 grp = getgrnam(str_gid);
 135                                 if (grp)
 136                                         gid = grp->gr_gid;
 137                                 else
 138                                         gid = strtoul(str_gid, NULL, 10);
 139                         }
 140
 141                         /* 3rd field: mode - device permissions */
 142                         if (!next) /* field must exist */
 143                                 bb_error_msg_and_die("bad line %u", lineno);
 144                         val = next;
 145                         next = next_field(val);
 146                         mode = strtoul(val, NULL, 8);
 147
 148                         /* 4th field (opt): >alias */
 149                         if (ENABLE_FEATURE_MDEV_RENAME) {
 150                                 if (!next)
 151                                         break;
 152                                 val = next;
 153                                 next = next_field(val);
 154                                 if (*val == '>') {
 155                                         alias = xstrdup(val + 1);
 156                                 }
 157                         }
 158
 159                         /* The rest (opt): command to run */
 160                         if (!next)
 161                                 break;
 162                         val = next;
 163                         if (ENABLE_FEATURE_MDEV_EXEC) {
 164                                 const char *s = "@$*";
 165                                 const char *s2 = strchr(s, *val);
 166
 167                                 if (!s2)
 168                                         bb_error_msg_and_die("bad line %u", lineno);
 169
 170                                 /* Correlate the position in the "@$*" with the delete
 171                                  * step so that we get the proper behavior:
 172                                  * @cmd: run on create
 173                                  * $cmd: run on delete
 174                                  * *cmd: run on both
 175                                  */
 176                                 if ((s2 - s + 1) /*1/2/3*/ & /*1/2*/ (1 + delete)) {
 177                                         command = xstrdup(val + 1);
 178                                 }
 179                         }
 180                         /* end of field parsing */
 181                         break; /* we found matching line, stop */
 182  next_line:
 183                         free(line);
 184                 } /* end of "while line is read from /etc/mdev.conf" */
 185
 186                 free(line); /* in case we used "break" to get here */
 187                 fclose(fp);
 188         }
 189  end_parse:
 190
 191         if (!delete && sscanf(dev_maj_min, "%u:%u", &major, &minor) == 2) {
 192
 193                 if (ENABLE_FEATURE_MDEV_RENAME)
 194                         unlink(device_name);
 195
 196                 if (mknod(device_name, mode | type, makedev(major, minor)) && errno != EEXIST)
 197                         bb_perror_msg_and_die("mknod %s", device_name);
 198
 199                 if (major == root_major && minor == root_minor)
 200                         symlink(device_name, "root");
 201
 202                 if (ENABLE_FEATURE_MDEV_CONF) {
 203                         chown(device_name, uid, gid);
 204
 205                         if (ENABLE_FEATURE_MDEV_RENAME && alias) {
 206                                 char *dest;
 207
 208                                 /* ">bar/": rename to bar/device_name */
 209                                 /* ">bar[/]baz": rename to bar[/]baz */
 210                                 dest = strrchr(alias, '/');
 211                                 if (dest) { /* ">bar/[baz]" ? */
 212                                         *dest = '\0'; /* mkdir bar */
 213                                         bb_make_directory(alias, 0755, FILEUTILS_RECUR);
 214                                         *dest = '/';
 215                                         if (dest[1] == '\0') { /* ">bar/" => ">bar/device_name" */
 216                                                 dest = alias;
 217                                                 alias = concat_path_file(alias, device_name);
 218                                                 free(dest);
 219                                         }
 220                                 }
 221
 222                                 /* recreate device_name as a symlink to moved device node */
 223                                 if (rename(device_name, alias) == 0) {
 224                                         symlink(alias, device_name);
 225                                 }
 226
 227                                 free(alias);
 228                         }
 229                 }
 230         }
 231
 232         if (ENABLE_FEATURE_MDEV_EXEC && command) {
 233                 /* setenv will leak memory, use putenv/unsetenv/free */
 234                 char *s = xasprintf("MDEV=%s", device_name);
 235                 putenv(s);
 236                 if (system(command) == -1)
 237                         bb_perror_msg_and_die("can't run '%s'", command);
 238                 s[4] = '\0';
 239                 unsetenv(s);
 240                 free(s);
 241                 free(command);
 242         }
 243
 244         if (delete)
 245                 unlink(device_name);
 246 }
 247
 248 /* File callback for /sys/ traversal */
 249 static int fileAction(const char *fileName,
 250                       struct stat *statbuf ATTRIBUTE_UNUSED,
 251                       void *userData,
 252                       int depth ATTRIBUTE_UNUSED)
 253 {
 254         size_t len = strlen(fileName) - 4; /* can't underflow */
 255         char *scratch = userData;
 256
 257         /* len check is for paranoid reasons */
 258         if (strcmp(fileName + len, "/dev") || len >= PATH_MAX)
 259                 return FALSE;
 260
 261         strcpy(scratch, fileName);
 262         scratch[len] = '\0';
 263         make_device(scratch, 0);
 264
 265         return TRUE;
 266 }
 267
 268 /* Directory callback for /sys/ traversal */
 269 static int dirAction(const char *fileName ATTRIBUTE_UNUSED,
 270                       struct stat *statbuf ATTRIBUTE_UNUSED,
 271                       void *userData ATTRIBUTE_UNUSED,
 272                       int depth)
 273 {
 274         return (depth >= MAX_SYSFS_DEPTH ? SKIP : TRUE);
 275 }
 276
 277 /* For the full gory details, see linux/Documentation/firmware_class/README
 278  *
 279  * Firmware loading works like this:
 280  * - kernel sets FIRMWARE env var
 281  * - userspace checks /lib/firmware/$FIRMWARE
 282  * - userspace waits for /sys/$DEVPATH/loading to appear
 283  * - userspace writes "1" to /sys/$DEVPATH/loading
 284  * - userspace copies /lib/firmware/$FIRMWARE into /sys/$DEVPATH/data
 285  * - userspace writes "0" (worked) or "-1" (failed) to /sys/$DEVPATH/loading
 286  * - kernel loads firmware into device
 287  */
 288 static void load_firmware(const char *const firmware, const char *const sysfs_path)
 289 {
 290         int cnt;
 291         int firmware_fd, loading_fd, data_fd;
 292
 293         /* check for /lib/firmware/$FIRMWARE */
 294         xchdir("/lib/firmware");
 295         firmware_fd = xopen(firmware, O_RDONLY);
 296
 297         /* in case we goto out ... */
 298         data_fd = -1;
 299
 300         /* check for /sys/$DEVPATH/loading ... give 30 seconds to appear */
 301         xchdir(sysfs_path);
 302         for (cnt = 0; cnt < 30; ++cnt) {
 303                 loading_fd = open("loading", O_WRONLY);
 304                 if (loading_fd != -1)
 305                         goto loading;
 306                 sleep(1);
 307         }
 308         goto out;
 309
 310  loading:
 311         /* tell kernel we're loading by `echo 1 > /sys/$DEVPATH/loading` */
 312         if (full_write(loading_fd, "1", 1) != 1)
 313                 goto out;
 314
 315         /* load firmware by `cat /lib/firmware/$FIRMWARE > /sys/$DEVPATH/data */
 316         data_fd = open("data", O_WRONLY);
 317         if (data_fd == -1)
 318                 goto out;
 319         cnt = bb_copyfd_eof(firmware_fd, data_fd);
 320
 321         /* tell kernel result by `echo [0|-1] > /sys/$DEVPATH/loading` */
 322         if (cnt > 0)
 323                 full_write(loading_fd, "0", 1);
 324         else
 325                 full_write(loading_fd, "-1", 2);
 326
 327  out:
 328         if (ENABLE_FEATURE_CLEAN_UP) {
 329                 close(firmware_fd);
 330                 close(loading_fd);
 331                 close(data_fd);
 332         }
 333 }
 334
 335 int mdev_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 336 int mdev_main(int argc, char **argv)
 337 {
 338         char *action;
 339         char *env_path;
 340         RESERVE_CONFIG_BUFFER(temp, PATH_MAX + SCRATCH_SIZE);
 341
 342         xchdir("/dev");
 343
 344         if (argc == 2 && !strcmp(argv[1], "-s")) {
 345                 /* Scan:
 346                  * mdev -s
 347                  */
 348                 struct stat st;
 349
 350                 xstat("/", &st);
 351                 root_major = major(st.st_dev);
 352                 root_minor = minor(st.st_dev);
 353
 354                 recursive_action("/sys/block",
 355                         ACTION_RECURSE | ACTION_FOLLOWLINKS,
 356                         fileAction, dirAction, temp, 0);
 357
 358                 recursive_action("/sys/class",
 359                         ACTION_RECURSE | ACTION_FOLLOWLINKS,
 360                         fileAction, dirAction, temp, 0);
 361
 362         } else {
 363                 /* Hotplug:
 364                  * env ACTION=... DEVPATH=... mdev
 365                  * ACTION can be "add" or "remove"
 366                  * DEVPATH is like "/block/sda" or "/class/input/mice"
 367                  */
 368                 action = getenv("ACTION");
 369                 env_path = getenv("DEVPATH");
 370                 if (!action || !env_path)
 371                         bb_show_usage();
 372
 373                 snprintf(temp, PATH_MAX, "/sys%s", env_path);
 374                 if (!strcmp(action, "remove"))
 375                         make_device(temp, 1);
 376                 else if (!strcmp(action, "add")) {
 377                         make_device(temp, 0);
 378
 379                         if (ENABLE_FEATURE_MDEV_LOAD_FIRMWARE) {
 380                                 char *fw = getenv("FIRMWARE");
 381                                 if (fw)
 382                                         load_firmware(fw, temp);
 383                         }
 384                 }
 385         }
 386
 387         if (ENABLE_FEATURE_CLEAN_UP)
 388                 RELEASE_CONFIG_BUFFER(temp);
 389
 390         return 0;
 391 }