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 unsigned char logname[LOGNAME_SIZE];
  68 void log_message (int level, const char *format, ...)
  69 {
  70         va_list args;
  71
  72         va_start(args, format);
  73         vsyslog(level, format, args);
  74         va_end(args);
  75 }
  76 #endif
  77
  78 #define msg_dump(msg) \
  79         dbg("msg_dump: sequence %llu, '%s', '%s', '%s'", \
  80         msg->seqnum, msg->action, msg->devpath, msg->subsystem);
  81
  82 static void msg_dump_queue(void)
  83 {
  84 #ifdef DEBUG
  85         struct hotplug_msg *msg;
  86
  87         list_for_each_entry(msg, &msg_list, list)
  88                 dbg("sequence %llu in queue", msg->seqnum);
  89 #endif
  90 }
  91
  92 static void run_queue_delete(struct hotplug_msg *msg)
  93 {
  94         list_del(&msg->list);
  95         free(msg);
  96 }
  97
  98 /* orders the message in the queue by sequence number */
  99 static void msg_queue_insert(struct hotplug_msg *msg)
 100 {
 101         struct hotplug_msg *loop_msg;
 102         struct sysinfo info;
 103
 104         /* sort message by sequence number into list. events
 105          * will tend to come in order, so scan the list backwards
 106          */
 107         list_for_each_entry_reverse(loop_msg, &msg_list, list)
 108                 if (loop_msg->seqnum < msg->seqnum)
 109                         break;
 110
 111         /* store timestamp of queuing */
 112         sysinfo(&info);
 113         msg->queue_time = info.uptime;
 114
 115         list_add(&msg->list, &loop_msg->list);
 116         dbg("queued message seq %llu", msg->seqnum);
 117
 118         /* run msg queue manager */
 119         run_msg_q = 1;
 120
 121         return ;
 122 }
 123
 124 /* forks event and removes event from run queue when finished */
 125 static void udev_run(struct hotplug_msg *msg)
 126 {
 127         char *const argv[] = { "udev", msg->subsystem, NULL };
 128         pid_t pid;
 129
 130         pid = fork();
 131         switch (pid) {
 132         case 0:
 133                 /* child */
 134                 close(udevsendsock);
 135                 logging_close();
 136                 execve(udev_bin, argv, msg->envp);
 137                 dbg("exec of child failed");
 138                 _exit(1);
 139                 break;
 140         case -1:
 141                 dbg("fork of child failed");
 142                 run_queue_delete(msg);
 143                 /* note: we never managed to run, so we had no impact on
 144                  * running_with_devpath(), so don't bother setting run_exec_q
 145                  */
 146                 break;
 147         default:
 148                 /* get SIGCHLD in main loop */
 149                 dbg("==> exec seq %llu [%d] working at '%s'", msg->seqnum, pid, msg->devpath);
 150                 msg->pid = pid;
 151         }
 152 }
 153
 154 /* returns still running task for the same event sequence */
 155 static struct hotplug_msg *running_with_devpath(struct hotplug_msg *msg)
 156 {
 157         struct hotplug_msg *loop_msg;
 158         int i;
 159
 160         list_for_each_entry(loop_msg, &running_list, list) {
 161                 if (loop_msg->devpath == NULL || msg->devpath == NULL)
 162                         continue;
 163
 164                 /* is a parent or child device event still running */
 165                 for (i = 0; i < DEVPATH_SIZE; i++) {
 166                         if (loop_msg->devpath[i] == '\0' || msg->devpath[i] == '\0')
 167                                 return loop_msg;
 168
 169                         if (loop_msg->devpath[i] != msg->devpath[i])
 170                                 break;
 171                 }
 172
 173                 /* is the physical device event still running on an add sequence */
 174                 if (msg->physdevpath && msg->action && strcmp(msg->action, "add") == 0)
 175                         for (i = 0; i < DEVPATH_SIZE; i++) {
 176                                 if (loop_msg->devpath[i] == '\0' || msg->physdevpath[i] == '\0')
 177                                         return loop_msg;
 178
 179                                 if (loop_msg->devpath[i] != msg->physdevpath[i])
 180                                         break;
 181                         }
 182         }
 183
 184         return NULL;
 185 }
 186
 187 /* exec queue management routine executes the events and serializes events in the same sequence */
 188 static void exec_queue_manager(void)
 189 {
 190         struct hotplug_msg *loop_msg;
 191         struct hotplug_msg *tmp_msg;
 192         struct hotplug_msg *msg;
 193
 194         list_for_each_entry_safe(loop_msg, tmp_msg, &exec_list, list) {
 195                 msg = running_with_devpath(loop_msg);
 196                 if (!msg) {
 197                         /* move event to run list */
 198                         list_move_tail(&loop_msg->list, &running_list);
 199                         udev_run(loop_msg);
 200                         dbg("moved seq %llu to running list", loop_msg->seqnum);
 201                 } else {
 202                         dbg("delay seq %llu (%s), cause seq %llu (%s) is still running",
 203                             loop_msg->seqnum, loop_msg->devpath, msg->seqnum, msg->devpath);
 204                 }
 205         }
 206 }
 207
 208 static void msg_move_exec(struct hotplug_msg *msg)
 209 {
 210         list_move_tail(&msg->list, &exec_list);
 211         run_exec_q = 1;
 212         expected_seqnum = msg->seqnum+1;
 213         dbg("moved seq %llu to exec, next expected is %llu",
 214                 msg->seqnum, expected_seqnum);
 215 }
 216
 217 /* msg queue management routine handles the timeouts and dispatches the events */
 218 static void msg_queue_manager(void)
 219 {
 220         struct hotplug_msg *loop_msg;
 221         struct hotplug_msg *tmp_msg;
 222         struct sysinfo info;
 223         long msg_age = 0;
 224
 225         dbg("msg queue manager, next expected is %llu", expected_seqnum);
 226 recheck:
 227         list_for_each_entry_safe(loop_msg, tmp_msg, &msg_list, list) {
 228                 /* move event with expected sequence to the exec list */
 229                 if (loop_msg->seqnum == expected_seqnum) {
 230                         msg_move_exec(loop_msg);
 231                         continue;
 232                 }
 233
 234                 /* move event with expired timeout to the exec list */
 235                 sysinfo(&info);
 236                 msg_age = info.uptime - loop_msg->queue_time;
 237                 dbg("seq %llu is %li seconds old", loop_msg->seqnum, msg_age);
 238                 if (msg_age > EVENT_TIMEOUT_SEC-1) {
 239                         msg_move_exec(loop_msg);
 240                         goto recheck;
 241                 } else {
 242                         break;
 243                 }
 244         }
 245
 246         msg_dump_queue();
 247
 248         /* set timeout for remaining queued events */
 249         if (list_empty(&msg_list) == 0) {
 250                 struct itimerval itv = {{0, 0}, {EVENT_TIMEOUT_SEC - msg_age, 0}};
 251                 dbg("next event expires in %li seconds", EVENT_TIMEOUT_SEC - msg_age);
 252                 setitimer(ITIMER_REAL, &itv, NULL);
 253         }
 254 }
 255
 256 /* receive the msg, do some basic sanity checks, and queue it */
 257 static void handle_udevsend_msg(int sock)
 258 {
 259         static struct udevsend_msg usend_msg;
 260         struct hotplug_msg *msg;
 261         int bufpos;
 262         int i;
 263         ssize_t size;
 264         struct msghdr smsg;
 265         struct cmsghdr *cmsg;
 266         struct iovec iov;
 267         struct ucred *cred;
 268         char cred_msg[CMSG_SPACE(sizeof(struct ucred))];
 269         int envbuf_size;
 270
 271         memset(&usend_msg, 0x00, sizeof(struct udevsend_msg));
 272         iov.iov_base = &usend_msg;
 273         iov.iov_len = sizeof(struct udevsend_msg);
 274
 275         memset(&smsg, 0x00, sizeof(struct msghdr));
 276         smsg.msg_iov = &iov;
 277         smsg.msg_iovlen = 1;
 278         smsg.msg_control = cred_msg;
 279         smsg.msg_controllen = sizeof(cred_msg);
 280
 281         size = recvmsg(sock, &smsg, 0);
 282         if (size <  0) {
 283                 if (errno != EINTR)
 284                         dbg("unable to receive message");
 285                 return;
 286         }
 287         cmsg = CMSG_FIRSTHDR(&smsg);
 288         cred = (struct ucred *) CMSG_DATA(cmsg);
 289
 290         if (cmsg == NULL || cmsg->cmsg_type != SCM_CREDENTIALS) {
 291                 dbg("no sender credentials received, message ignored");
 292                 goto exit;
 293         }
 294
 295         if (cred->uid != 0) {
 296                 dbg("sender uid=%i, message ignored", cred->uid);
 297                 goto exit;
 298         }
 299
 300         if (strncmp(usend_msg.magic, UDEV_MAGIC, sizeof(UDEV_MAGIC)) != 0 ) {
 301                 dbg("message magic '%s' doesn't match, ignore it", usend_msg.magic);
 302                 goto exit;
 303         }
 304
 305         envbuf_size = size - offsetof(struct udevsend_msg, envbuf);
 306         dbg("envbuf_size=%i", envbuf_size);
 307         msg = malloc(sizeof(struct hotplug_msg) + envbuf_size);
 308         memset(msg, 0x00, sizeof(struct hotplug_msg) + envbuf_size);
 309
 310         /* copy environment buffer and reconstruct envp */
 311         memcpy(msg->envbuf, usend_msg.envbuf, envbuf_size);
 312         bufpos = 0;
 313         for (i = 0; (bufpos < envbuf_size) && (i < HOTPLUG_NUM_ENVP-2); i++) {
 314                 int keylen;
 315                 char *key;
 316
 317                 key = &msg->envbuf[bufpos];
 318                 keylen = strlen(key);
 319                 msg->envp[i] = key;
 320                 bufpos += keylen + 1;
 321                 dbg("add '%s' to msg.envp[%i]", msg->envp[i], i);
 322
 323                 /* remember some keys for further processing */
 324                 if (strncmp(key, "ACTION=", 7) == 0)
 325                         msg->action = &key[7];
 326
 327                 if (strncmp(key, "DEVPATH=", 8) == 0)
 328                         msg->devpath = &key[8];
 329
 330                 if (strncmp(key, "SUBSYSTEM=", 10) == 0)
 331                         msg->subsystem = &key[10];
 332
 333                 if (strncmp(key, "SEQNUM=", 7) == 0)
 334                         msg->seqnum = strtoull(&key[7], NULL, 10);
 335
 336                 if (strncmp(key, "PHYSDEVPATH=", 12) == 0)
 337                         msg->physdevpath = &key[12];
 338         }
 339         msg->envp[i++] = "MANAGED_EVENT=1";
 340         msg->envp[i] = NULL;
 341
 342         /* if no seqnum is given, we move straight to exec queue */
 343         if (msg->seqnum == 0) {
 344                 list_add(&msg->list, &exec_list);
 345                 run_exec_q = 1;
 346         } else {
 347                 msg_queue_insert(msg);
 348         }
 349
 350 exit:
 351         return;
 352 }
 353
 354 static void asmlinkage sig_handler(int signum)
 355 {
 356         int rc;
 357
 358         switch (signum) {
 359                 case SIGINT:
 360                 case SIGTERM:
 361                         exit(20 + signum);
 362                         break;
 363                 case SIGALRM:
 364                         /* set flag, then write to pipe if needed */
 365                         run_msg_q = 1;
 366                         goto do_write;
 367                         break;
 368                 case SIGCHLD:
 369                         /* set flag, then write to pipe if needed */
 370                         sigchilds_waiting = 1;
 371                         goto do_write;
 372                         break;
 373         }
 374
 375 do_write:
 376         /* if pipe is empty, write to pipe to force select to return
 377          * immediately when it gets called
 378          */
 379         if (!sig_flag) {
 380                 rc = write(pipefds[1],&signum,sizeof(signum));
 381                 if (rc >= 0)
 382                         sig_flag = 1;
 383         }
 384 }
 385
 386 static void udev_done(int pid)
 387 {
 388         /* find msg associated with pid and delete it */
 389         struct hotplug_msg *msg;
 390
 391         list_for_each_entry(msg, &running_list, list) {
 392                 if (msg->pid == pid) {
 393                         dbg("<== exec seq %llu came back", msg->seqnum);
 394                         run_queue_delete(msg);
 395
 396                         /* we want to run the exec queue manager since there may
 397                          * be events waiting with the devpath of the one that
 398                          * just finished
 399                          */
 400                         run_exec_q = 1;
 401                         return;
 402                 }
 403         }
 404 }
 405
 406 static void reap_sigchilds(void)
 407 {
 408         while(1) {
 409                 int pid = waitpid(-1, NULL, WNOHANG);
 410                 if ((pid == -1) || (pid == 0))
 411                         break;
 412                 udev_done(pid);
 413         }
 414 }
 415
 416 /* just read everything from the pipe and clear the flag,
 417  * the flags was set in the signal handler
 418  */
 419 static void user_sighandler(void)
 420 {
 421         int sig;
 422         while(1) {
 423                 int rc = read(pipefds[0], &sig, sizeof(sig));
 424                 if (rc < 0)
 425                         break;
 426
 427                 sig_flag = 0;
 428         }
 429 }
 430
 431 int main(int argc, char *argv[], char *envp[])
 432 {
 433         int maxsockplus;
 434         struct sockaddr_un saddr;
 435         socklen_t addrlen;
 436         int retval, fd;
 437         const int feature_on = 1;
 438         struct sigaction act;
 439         fd_set readfds;
 440
 441         logging_init("udevd");
 442         dbg("version %s", UDEV_VERSION);
 443
 444         if (getuid() != 0) {
 445                 dbg("need to be root, exit");
 446                 goto exit;
 447         }
 448
 449         /* make sure we don't lock any path */
 450         chdir("/");
 451         umask(umask(077) | 022);
 452
 453         /* Set fds to dev/null */
 454         fd = open( "/dev/null", O_RDWR );
 455         if ( fd < 0 ) {
 456                 dbg("error opening /dev/null %s", strerror(errno));
 457                 goto exit;
 458         }
 459         dup2(fd, 0);
 460         dup2(fd, 1);
 461         dup2(fd, 2);
 462         if (fd > 2)
 463                 close(fd);
 464
 465         /* become session leader */
 466         setsid();
 467
 468         /* setup signal handler pipe */
 469         retval = pipe(pipefds);
 470         if (retval < 0) {
 471                 dbg("error getting pipes: %s", strerror(errno));
 472                 goto exit;
 473         }
 474
 475         retval = fcntl(pipefds[0], F_SETFL, O_NONBLOCK);
 476         if (retval < 0) {
 477                 dbg("error fcntl on read pipe: %s", strerror(errno));
 478                 goto exit;
 479         }
 480         retval = fcntl(pipefds[0], F_SETFD, FD_CLOEXEC);
 481         if (retval < 0) {
 482                 dbg("error fcntl on read pipe: %s", strerror(errno));
 483                 goto exit;
 484         }
 485
 486         retval = fcntl(pipefds[1], F_SETFL, O_NONBLOCK);
 487         if (retval < 0) {
 488                 dbg("error fcntl on write pipe: %s", strerror(errno));
 489                 goto exit;
 490         }
 491         retval = fcntl(pipefds[1], F_SETFD, FD_CLOEXEC);
 492         if (retval < 0) {
 493                 dbg("error fcntl on write pipe: %s", strerror(errno));
 494                 goto exit;
 495         }
 496
 497         /* set signal handlers */
 498         act.sa_handler = (void (*) (int))sig_handler;
 499         sigemptyset(&act.sa_mask);
 500         act.sa_flags = SA_RESTART;
 501         sigaction(SIGINT, &act, NULL);
 502         sigaction(SIGTERM, &act, NULL);
 503         sigaction(SIGALRM, &act, NULL);
 504         sigaction(SIGCHLD, &act, NULL);
 505
 506         memset(&saddr, 0x00, sizeof(saddr));
 507         saddr.sun_family = AF_LOCAL;
 508         /* use abstract namespace for socket path */
 509         strcpy(&saddr.sun_path[1], UDEVD_SOCK_PATH);
 510         addrlen = offsetof(struct sockaddr_un, sun_path) + strlen(saddr.sun_path+1) + 1;
 511
 512         udevsendsock = socket(AF_LOCAL, SOCK_DGRAM, 0);
 513         if (udevsendsock == -1) {
 514                 dbg("error getting socket, exit");
 515                 goto exit;
 516         }
 517
 518         /* the bind takes care of ensuring only one copy running */
 519         retval = bind(udevsendsock, (struct sockaddr *) &saddr, addrlen);
 520         if (retval < 0) {
 521                 dbg("bind failed, exit");
 522                 close(udevsendsock);
 523                 goto exit;
 524         }
 525
 526         /* enable receiving of the sender credentials */
 527         setsockopt(udevsendsock, SOL_SOCKET, SO_PASSCRED, &feature_on, sizeof(feature_on));
 528
 529         /* possible override of udev binary, used for testing */
 530         udev_bin = getenv("UDEV_BIN");
 531         if (udev_bin != NULL)
 532                 dbg("udev binary is set to '%s'", udev_bin);
 533         else
 534                 udev_bin = UDEV_BIN;
 535
 536         FD_ZERO(&readfds);
 537         FD_SET(udevsendsock, &readfds);
 538         FD_SET(pipefds[0], &readfds);
 539         maxsockplus = udevsendsock+1;
 540         while (1) {
 541                 fd_set workreadfds = readfds;
 542                 retval = select(maxsockplus, &workreadfds, NULL, NULL, NULL);
 543
 544                 if (retval < 0) {
 545                         if (errno != EINTR)
 546                                 dbg("error in select: %s", strerror(errno));
 547                         continue;
 548                 }
 549
 550                 if (FD_ISSET(udevsendsock, &workreadfds))
 551                         handle_udevsend_msg(udevsendsock);
 552
 553                 if (FD_ISSET(pipefds[0], &workreadfds))
 554                         user_sighandler();
 555
 556                 if (sigchilds_waiting) {
 557                         sigchilds_waiting = 0;
 558                         reap_sigchilds();
 559                 }
 560
 561                 if (run_msg_q) {
 562                         run_msg_q = 0;
 563                         msg_queue_manager();
 564                 }
 565
 566                 if (run_exec_q) {
 567                          /* clean up running_list before calling exec_queue_manager() */
 568                         if (sigchilds_waiting) {
 569                                 sigchilds_waiting = 0;
 570                                 reap_sigchilds();
 571                         }
 572
 573                         run_exec_q = 0;
 574                         exec_queue_manager();
 575                 }
 576         }
 577
 578 exit:
 579         logging_close();
 580         return 1;
 581 }