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