udevd.c

   1 /*
   2  * udevd.c - hotplug event serializer
   3  *
   4  * Copyright (C) 2004 Kay Sievers <kay.sievers@vrfy.org>
   5  * Copyright (C) 2004 Chris Friesen <chris_friesen@sympatico.ca>
   6  *
   7  *
   8  *      This program is free software; you can redistribute it and/or modify it
   9  *      under the terms of the GNU General Public License as published by the
  10  *      Free Software Foundation version 2 of the License.
  11  *
  12  *      This program is distributed in the hope that it will be useful, but
  13  *      WITHOUT ANY WARRANTY; without even the implied warranty of
  14  *      MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15  *      General Public License for more details.
  16  *
  17  *      You should have received a copy of the GNU General Public License along
  18  *      with this program; if not, write to the Free Software Foundation, Inc.,
  19  *      675 Mass Ave, Cambridge, MA 02139, USA.
  20  *
  21  */
  22
  23 #include <stddef.h>
  24 #include <sys/wait.h>
  25 #include <signal.h>
  26 #include <unistd.h>
  27 #include <errno.h>
  28 #include <stdio.h>
  29 #include <stdlib.h>
  30 #include <string.h>
  31 #include <sys/time.h>
  32 #include <sys/types.h>
  33 #include <sys/socket.h>
  34 #include <sys/un.h>
  35 #include <fcntl.h>
  36 #include <sys/sysinfo.h>
  37 #include <sys/stat.h>
  38
  39 #include "list.h"
  40 #include "udev.h"
  41 #include "udev_version.h"
  42 #include "udev_utils.h"
  43 #include "udevd.h"
  44 #include "logging.h"
  45
  46 /* global variables*/
  47 static int udevsendsock;
  48
  49 static int pipefds[2];
  50 static unsigned long long expected_seqnum = 0;
  51 static volatile int sigchilds_waiting;
  52 static volatile int run_msg_q;
  53 static volatile int sig_flag;
  54 static int run_exec_q;
  55
  56 static LIST_HEAD(msg_list);
  57 static LIST_HEAD(exec_list);
  58 static LIST_HEAD(running_list);
  59
  60 static void exec_queue_manager(void);
  61 static void msg_queue_manager(void);
  62 static void user_sighandler(void);
  63 static void reap_sigchilds(void);
  64 char *udev_bin;
  65
  66 #ifdef LOG
  67 void log_message (int level, const char *format, ...)
  68 {
  69         va_list args;
  70
  71         va_start(args, format);
  72         vsyslog(level, format, args);
  73         va_end(args);
  74 }
  75 #endif
  76
  77 #define msg_dump(msg) \
  78         dbg("msg_dump: sequence %llu, '%s', '%s', '%s'", \
  79         msg->seqnum, msg->action, msg->devpath, msg->subsystem);
  80
  81 static void msg_dump_queue(void)
  82 {
  83 #ifdef DEBUG
  84         struct hotplug_msg *msg;
  85
  86         list_for_each_entry(msg, &msg_list, list)
  87                 dbg("sequence %llu in queue", msg->seqnum);
  88 #endif
  89 }
  90
  91 static void run_queue_delete(struct hotplug_msg *msg)
  92 {
  93         list_del(&msg->list);
  94         free(msg);
  95 }
  96
  97 /* orders the message in the queue by sequence number */
  98 static void msg_queue_insert(struct hotplug_msg *msg)
  99 {
 100         struct hotplug_msg *loop_msg;
 101         struct sysinfo info;
 102
 103         /* sort message by sequence number into list. events
 104          * will tend to come in order, so scan the list backwards
 105          */
 106         list_for_each_entry_reverse(loop_msg, &msg_list, list)
 107                 if (loop_msg->seqnum < msg->seqnum)
 108                         break;
 109
 110         /* store timestamp of queuing */
 111         sysinfo(&info);
 112         msg->queue_time = info.uptime;
 113
 114         list_add(&msg->list, &loop_msg->list);
 115         dbg("queued message seq %llu", msg->seqnum);
 116
 117         /* run msg queue manager */
 118         run_msg_q = 1;
 119
 120         return ;
 121 }
 122
 123 /* forks event and removes event from run queue when finished */
 124 static void udev_run(struct hotplug_msg *msg)
 125 {
 126         char *const argv[] = { "udev", msg->subsystem, NULL };
 127         pid_t pid;
 128
 129         pid = fork();
 130         switch (pid) {
 131         case 0:
 132                 /* child */
 133                 close(udevsendsock);
 134                 logging_close();
 135                 execve(udev_bin, argv, msg->envp);
 136                 dbg("exec of child failed");
 137                 _exit(1);
 138                 break;
 139         case -1:
 140                 dbg("fork of child failed");
 141                 run_queue_delete(msg);
 142                 /* note: we never managed to run, so we had no impact on
 143                  * running_with_devpath(), so don't bother setting run_exec_q
 144                  */
 145                 break;
 146         default:
 147                 /* get SIGCHLD in main loop */
 148                 dbg("==> exec seq %llu [%d] working at '%s'", msg->seqnum, pid, msg->devpath);
 149                 msg->pid = pid;
 150         }
 151 }
 152
 153 /* returns still running task for the same event sequence */
 154 static struct hotplug_msg *running_with_devpath(struct hotplug_msg *msg)
 155 {
 156         struct hotplug_msg *loop_msg;
 157         int i;
 158
 159         list_for_each_entry(loop_msg, &running_list, list) {
 160                 if (loop_msg->devpath == NULL || msg->devpath == NULL)
 161                         continue;
 162
 163                 /* is a parent or child device event still running */
 164                 for (i = 0; i < DEVPATH_SIZE; i++) {
 165                         if (loop_msg->devpath[i] == '\0' || msg->devpath[i] == '\0')
 166                                 return loop_msg;
 167
 168                         if (loop_msg->devpath[i] != msg->devpath[i])
 169                                 break;
 170                 }
 171
 172                 /* is the physical device event still running on an add sequence */
 173                 if (msg->physdevpath && msg->action && strcmp(msg->action, "add") == 0)
 174                         for (i = 0; i < DEVPATH_SIZE; i++) {
 175                                 if (loop_msg->devpath[i] == '\0' || msg->physdevpath[i] == '\0')
 176                                         return loop_msg;
 177
 178                                 if (loop_msg->devpath[i] != msg->physdevpath[i])
 179                                         break;
 180                         }
 181         }
 182
 183         return NULL;
 184 }
 185
 186 /* exec queue management routine executes the events and serializes events in the same sequence */
 187 static void exec_queue_manager(void)
 188 {
 189         struct hotplug_msg *loop_msg;
 190         struct hotplug_msg *tmp_msg;
 191         struct hotplug_msg *msg;
 192
 193         list_for_each_entry_safe(loop_msg, tmp_msg, &exec_list, list) {
 194                 msg = running_with_devpath(loop_msg);
 195                 if (!msg) {
 196                         /* move event to run list */
 197                         list_move_tail(&loop_msg->list, &running_list);
 198                         udev_run(loop_msg);
 199                         dbg("moved seq %llu to running list", loop_msg->seqnum);
 200                 } else {
 201                         dbg("delay seq %llu (%s), cause seq %llu (%s) is still running",
 202                             loop_msg->seqnum, loop_msg->devpath, msg->seqnum, msg->devpath);
 203                 }
 204         }
 205 }
 206
 207 static void msg_move_exec(struct hotplug_msg *msg)
 208 {
 209         list_move_tail(&msg->list, &exec_list);
 210         run_exec_q = 1;
 211         expected_seqnum = msg->seqnum+1;
 212         dbg("moved seq %llu to exec, next expected is %llu",
 213                 msg->seqnum, expected_seqnum);
 214 }
 215
 216 /* msg queue management routine handles the timeouts and dispatches the events */
 217 static void msg_queue_manager(void)
 218 {
 219         struct hotplug_msg *loop_msg;
 220         struct hotplug_msg *tmp_msg;
 221         struct sysinfo info;
 222         long msg_age = 0;
 223
 224         dbg("msg queue manager, next expected is %llu", expected_seqnum);
 225 recheck:
 226         list_for_each_entry_safe(loop_msg, tmp_msg, &msg_list, list) {
 227                 /* move event with expected sequence to the exec list */
 228                 if (loop_msg->seqnum == expected_seqnum) {
 229                         msg_move_exec(loop_msg);
 230                         continue;
 231                 }
 232
 233                 /* move event with expired timeout to the exec list */
 234                 sysinfo(&info);
 235                 msg_age = info.uptime - loop_msg->queue_time;
 236                 dbg("seq %llu is %li seconds old", loop_msg->seqnum, msg_age);
 237                 if (msg_age > EVENT_TIMEOUT_SEC-1) {
 238                         msg_move_exec(loop_msg);
 239                         goto recheck;
 240                 } else {
 241                         break;
 242                 }
 243         }
 244
 245         msg_dump_queue();
 246
 247         /* set timeout for remaining queued events */
 248         if (list_empty(&msg_list) == 0) {
 249                 struct itimerval itv = {{0, 0}, {EVENT_TIMEOUT_SEC - msg_age, 0}};
 250                 dbg("next event expires in %li seconds", EVENT_TIMEOUT_SEC - msg_age);
 251                 setitimer(ITIMER_REAL, &itv, NULL);
 252         }
 253 }
 254
 255 /* receive the msg, do some basic sanity checks, and queue it */
 256 static void handle_udevsend_msg(int sock)
 257 {
 258         static struct udevsend_msg usend_msg;
 259         struct hotplug_msg *msg;
 260         int bufpos;
 261         int i;
 262         ssize_t size;
 263         struct msghdr smsg;
 264         struct cmsghdr *cmsg;
 265         struct iovec iov;
 266         struct ucred *cred;
 267         char cred_msg[CMSG_SPACE(sizeof(struct ucred))];
 268         int envbuf_size;
 269
 270         memset(&usend_msg, 0x00, sizeof(struct udevsend_msg));
 271         iov.iov_base = &usend_msg;
 272         iov.iov_len = sizeof(struct udevsend_msg);
 273
 274         memset(&smsg, 0x00, sizeof(struct msghdr));
 275         smsg.msg_iov = &iov;
 276         smsg.msg_iovlen = 1;
 277         smsg.msg_control = cred_msg;
 278         smsg.msg_controllen = sizeof(cred_msg);
 279
 280         size = recvmsg(sock, &smsg, 0);
 281         if (size <  0) {
 282                 if (errno != EINTR)
 283                         dbg("unable to receive message");
 284                 return;
 285         }
 286         cmsg = CMSG_FIRSTHDR(&smsg);
 287         cred = (struct ucred *) CMSG_DATA(cmsg);
 288
 289         if (cmsg == NULL || cmsg->cmsg_type != SCM_CREDENTIALS) {
 290                 dbg("no sender credentials received, message ignored");
 291                 goto exit;
 292         }
 293
 294         if (cred->uid != 0) {
 295                 dbg("sender uid=%i, message ignored", cred->uid);
 296                 goto exit;
 297         }
 298
 299         if (strncmp(usend_msg.magic, UDEV_MAGIC, sizeof(UDEV_MAGIC)) != 0 ) {
 300                 dbg("message magic '%s' doesn't match, ignore it", usend_msg.magic);
 301                 goto exit;
 302         }
 303
 304         envbuf_size = size - offsetof(struct udevsend_msg, envbuf);
 305         dbg("envbuf_size=%i", envbuf_size);
 306         msg = malloc(sizeof(struct hotplug_msg) + envbuf_size);
 307         memset(msg, 0x00, sizeof(struct hotplug_msg) + envbuf_size);
 308
 309         /* copy environment buffer and reconstruct envp */
 310         memcpy(msg->envbuf, usend_msg.envbuf, envbuf_size);
 311         bufpos = 0;
 312         for (i = 0; (bufpos < envbuf_size) && (i < HOTPLUG_NUM_ENVP-2); i++) {
 313                 int keylen;
 314                 char *key;
 315
 316                 key = &msg->envbuf[bufpos];
 317                 keylen = strlen(key);
 318                 msg->envp[i] = key;
 319                 bufpos += keylen + 1;
 320                 dbg("add '%s' to msg.envp[%i]", msg->envp[i], i);
 321
 322                 /* remember some keys for further processing */
 323                 if (strncmp(key, "ACTION=", 7) == 0)
 324                         msg->action = &key[7];
 325
 326                 if (strncmp(key, "DEVPATH=", 8) == 0)
 327                         msg->devpath = &key[8];
 328
 329                 if (strncmp(key, "SUBSYSTEM=", 10) == 0)
 330                         msg->subsystem = &key[10];
 331
 332                 if (strncmp(key, "SEQNUM=", 7) == 0)
 333                         msg->seqnum = strtoull(&key[7], NULL, 10);
 334
 335                 if (strncmp(key, "PHYSDEVPATH=", 12) == 0)
 336                         msg->physdevpath = &key[12];
 337         }
 338         msg->envp[i++] = "UDEVD_EVENT=1";
 339         msg->envp[i] = NULL;
 340
 341         /* if no seqnum is given, we move straight to exec queue */
 342         if (msg->seqnum == 0) {
 343                 list_add(&msg->list, &exec_list);
 344                 run_exec_q = 1;
 345         } else {
 346                 msg_queue_insert(msg);
 347         }
 348
 349 exit:
 350         return;
 351 }
 352
 353 static void asmlinkage sig_handler(int signum)
 354 {
 355         int rc;
 356
 357         switch (signum) {
 358                 case SIGINT:
 359                 case SIGTERM:
 360                         exit(20 + signum);
 361                         break;
 362                 case SIGALRM:
 363                         /* set flag, then write to pipe if needed */
 364                         run_msg_q = 1;
 365                         goto do_write;
 366                         break;
 367                 case SIGCHLD:
 368                         /* set flag, then write to pipe if needed */
 369                         sigchilds_waiting = 1;
 370                         goto do_write;
 371                         break;
 372         }
 373
 374 do_write:
 375         /* if pipe is empty, write to pipe to force select to return
 376          * immediately when it gets called
 377          */
 378         if (!sig_flag) {
 379                 rc = write(pipefds[1],&signum,sizeof(signum));
 380                 if (rc >= 0)
 381                         sig_flag = 1;
 382         }
 383 }
 384
 385 static void udev_done(int pid)
 386 {
 387         /* find msg associated with pid and delete it */
 388         struct hotplug_msg *msg;
 389
 390         list_for_each_entry(msg, &running_list, list) {
 391                 if (msg->pid == pid) {
 392                         dbg("<== exec seq %llu came back", msg->seqnum);
 393                         run_queue_delete(msg);
 394
 395                         /* we want to run the exec queue manager since there may
 396                          * be events waiting with the devpath of the one that
 397                          * just finished
 398                          */
 399                         run_exec_q = 1;
 400                         return;
 401                 }
 402         }
 403 }
 404
 405 static void reap_sigchilds(void)
 406 {
 407         while(1) {
 408                 int pid = waitpid(-1, NULL, WNOHANG);
 409                 if ((pid == -1) || (pid == 0))
 410                         break;
 411                 udev_done(pid);
 412         }
 413 }
 414
 415 /* just read everything from the pipe and clear the flag,
 416  * the flags was set in the signal handler
 417  */
 418 static void user_sighandler(void)
 419 {
 420         int sig;
 421         while(1) {
 422                 int rc = read(pipefds[0], &sig, sizeof(sig));
 423                 if (rc < 0)
 424                         break;
 425
 426                 sig_flag = 0;
 427         }
 428 }
 429
 430 int main(int argc, char *argv[], char *envp[])
 431 {
 432         int maxsockplus;
 433         struct sockaddr_un saddr;
 434         socklen_t addrlen;
 435         int retval, fd;
 436         const int feature_on = 1;
 437         struct sigaction act;
 438         fd_set readfds;
 439
 440         logging_init("udevd");
 441         dbg("version %s", UDEV_VERSION);
 442
 443         if (getuid() != 0) {
 444                 dbg("need to be root, exit");
 445                 goto exit;
 446         }
 447
 448         /* make sure we don't lock any path */
 449         chdir("/");
 450         umask(umask(077) | 022);
 451
 452         /* Set fds to dev/null */
 453         fd = open( "/dev/null", O_RDWR );
 454         if ( fd < 0 ) {
 455                 dbg("error opening /dev/null %s", strerror(errno));
 456                 goto exit;
 457         }
 458         dup2(fd, 0);
 459         dup2(fd, 1);
 460         dup2(fd, 2);
 461         if (fd > 2)
 462                 close(fd);
 463
 464         /* become session leader */
 465         setsid();
 466
 467         /* setup signal handler pipe */
 468         retval = pipe(pipefds);
 469         if (retval < 0) {
 470                 dbg("error getting pipes: %s", strerror(errno));
 471                 goto exit;
 472         }
 473
 474         retval = fcntl(pipefds[0], F_SETFL, O_NONBLOCK);
 475         if (retval < 0) {
 476                 dbg("error fcntl on read pipe: %s", strerror(errno));
 477                 goto exit;
 478         }
 479         retval = fcntl(pipefds[0], F_SETFD, FD_CLOEXEC);
 480         if (retval < 0) {
 481                 dbg("error fcntl on read pipe: %s", strerror(errno));
 482                 goto exit;
 483         }
 484
 485         retval = fcntl(pipefds[1], F_SETFL, O_NONBLOCK);
 486         if (retval < 0) {
 487                 dbg("error fcntl on write pipe: %s", strerror(errno));
 488                 goto exit;
 489         }
 490         retval = fcntl(pipefds[1], F_SETFD, FD_CLOEXEC);
 491         if (retval < 0) {
 492                 dbg("error fcntl on write pipe: %s", strerror(errno));
 493                 goto exit;
 494         }
 495
 496         /* set signal handlers */
 497         act.sa_handler = (void (*) (int))sig_handler;
 498         sigemptyset(&act.sa_mask);
 499         act.sa_flags = SA_RESTART;
 500         sigaction(SIGINT, &act, NULL);
 501         sigaction(SIGTERM, &act, NULL);
 502         sigaction(SIGALRM, &act, NULL);
 503         sigaction(SIGCHLD, &act, NULL);
 504
 505         memset(&saddr, 0x00, sizeof(saddr));
 506         saddr.sun_family = AF_LOCAL;
 507         /* use abstract namespace for socket path */
 508         strcpy(&saddr.sun_path[1], UDEVD_SOCK_PATH);
 509         addrlen = offsetof(struct sockaddr_un, sun_path) + strlen(saddr.sun_path+1) + 1;
 510
 511         udevsendsock = socket(AF_LOCAL, SOCK_DGRAM, 0);
 512         if (udevsendsock == -1) {
 513                 dbg("error getting socket, exit");
 514                 goto exit;
 515         }
 516
 517         /* the bind takes care of ensuring only one copy running */
 518         retval = bind(udevsendsock, (struct sockaddr *) &saddr, addrlen);
 519         if (retval < 0) {
 520                 dbg("bind failed, exit");
 521                 close(udevsendsock);
 522                 goto exit;
 523         }
 524
 525         /* enable receiving of the sender credentials */
 526         setsockopt(udevsendsock, SOL_SOCKET, SO_PASSCRED, &feature_on, sizeof(feature_on));
 527
 528         /* possible override of udev binary, used for testing */
 529         udev_bin = getenv("UDEV_BIN");
 530         if (udev_bin != NULL)
 531                 dbg("udev binary is set to '%s'", udev_bin);
 532         else
 533                 udev_bin = UDEV_BIN;
 534
 535         FD_ZERO(&readfds);
 536         FD_SET(udevsendsock, &readfds);
 537         FD_SET(pipefds[0], &readfds);
 538         maxsockplus = udevsendsock+1;
 539         while (1) {
 540                 fd_set workreadfds = readfds;
 541                 retval = select(maxsockplus, &workreadfds, NULL, NULL, NULL);
 542
 543                 if (retval < 0) {
 544                         if (errno != EINTR)
 545                                 dbg("error in select: %s", strerror(errno));
 546                         continue;
 547                 }
 548
 549                 if (FD_ISSET(udevsendsock, &workreadfds))
 550                         handle_udevsend_msg(udevsendsock);
 551
 552                 if (FD_ISSET(pipefds[0], &workreadfds))
 553                         user_sighandler();
 554
 555                 if (sigchilds_waiting) {
 556                         sigchilds_waiting = 0;
 557                         reap_sigchilds();
 558                 }
 559
 560                 if (run_msg_q) {
 561                         run_msg_q = 0;
 562                         msg_queue_manager();
 563                 }
 564
 565                 if (run_exec_q) {
 566                          /* clean up running_list before calling exec_queue_manager() */
 567                         if (sigchilds_waiting) {
 568                                 sigchilds_waiting = 0;
 569                                 reap_sigchilds();
 570                         }
 571
 572                         run_exec_q = 0;
 573                         exec_queue_manager();
 574                 }
 575         }
 576
 577 exit:
 578         logging_close();
 579         return 1;
 580 }