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 "klibc_fixups.h"
  37 #include <sys/sysinfo.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 long expected_seqnum = 0;
  48 volatile static int children_waiting;
  49 volatile static int run_msg_q;
  50 volatile static 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_kids(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 %d, '%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 %li 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 %li", 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         strcpy(action, "ACTION=");
 141         strfieldcat(action, msg->action);
 142         strcpy(devpath, "DEVPATH=");
 143         strfieldcat(devpath, msg->devpath);
 144         strcpy(seqnum, "SEQNUM=");
 145         strlongcat(seqnum, msg->seqnum);
 146
 147         pid = fork();
 148         switch (pid) {
 149         case 0:
 150                 /* child */
 151                 execle(udev_bin, "udev", msg->subsystem, NULL, env);
 152                 dbg("exec of child failed");
 153                 exit(1);
 154                 break;
 155         case -1:
 156                 dbg("fork of child failed");
 157                 run_queue_delete(msg);
 158                 /* note: we never managed to run, so we had no impact on
 159                  * running_with_devpath(), so don't bother setting run_exec_q
 160                  */
 161                 break;
 162         default:
 163                 /* get SIGCHLD in main loop */
 164                 dbg("==> exec seq %li [%d] working at '%s'", msg->seqnum, pid, msg->devpath);
 165                 msg->pid = pid;
 166         }
 167 }
 168
 169 /* returns already running task with devpath */
 170 static struct hotplug_msg *running_with_devpath(struct hotplug_msg *msg)
 171 {
 172         struct hotplug_msg *loop_msg;
 173         list_for_each_entry(loop_msg, &running_list, list)
 174                 if (strncmp(loop_msg->devpath, msg->devpath, sizeof(loop_msg->devpath)) == 0)
 175                         return loop_msg;
 176         return NULL;
 177 }
 178
 179 /* exec queue management routine executes the events and delays events for the same devpath */
 180 static void exec_queue_manager()
 181 {
 182         struct hotplug_msg *loop_msg;
 183         struct hotplug_msg *tmp_msg;
 184         struct hotplug_msg *msg;
 185
 186         list_for_each_entry_safe(loop_msg, tmp_msg, &exec_list, list) {
 187                 msg = running_with_devpath(loop_msg);
 188                 if (!msg) {
 189                         /* move event to run list */
 190                         list_move_tail(&loop_msg->list, &running_list);
 191                         udev_run(loop_msg);
 192                         dbg("moved seq %li to running list", loop_msg->seqnum);
 193                 } else {
 194                         dbg("delay seq %li, cause seq %li already working on '%s'",
 195                                 loop_msg->seqnum, msg->seqnum, msg->devpath);
 196                 }
 197         }
 198 }
 199
 200 static void msg_move_exec(struct hotplug_msg *msg)
 201 {
 202         list_move_tail(&msg->list, &exec_list);
 203         run_exec_q = 1;
 204         expected_seqnum = msg->seqnum+1;
 205         dbg("moved seq %li to exec, next expected is %li",
 206                 msg->seqnum, expected_seqnum);
 207 }
 208
 209 /* msg queue management routine handles the timeouts and dispatches the events */
 210 static void msg_queue_manager()
 211 {
 212         struct hotplug_msg *loop_msg;
 213         struct hotplug_msg *tmp_msg;
 214         struct sysinfo info;
 215         long msg_age = 0;
 216
 217         dbg("msg queue manager, next expected is %li", expected_seqnum);
 218 recheck:
 219         list_for_each_entry_safe(loop_msg, tmp_msg, &msg_list, list) {
 220                 /* move event with expected sequence to the exec list */
 221                 if (loop_msg->seqnum == expected_seqnum) {
 222                         msg_move_exec(loop_msg);
 223                         continue;
 224                 }
 225
 226                 /* move event with expired timeout to the exec list */
 227                 sysinfo(&info);
 228                 msg_age = info.uptime - loop_msg->queue_time;
 229                 dbg("seq %li is %li seconds old", loop_msg->seqnum, msg_age);
 230                 if (msg_age > EVENT_TIMEOUT_SEC-1) {
 231                         msg_move_exec(loop_msg);
 232                         goto recheck;
 233                 } else {
 234                         break;
 235                 }
 236         }
 237
 238         msg_dump_queue();
 239
 240         /* set timeout for remaining queued events */
 241         if (list_empty(&msg_list) == 0) {
 242                 struct itimerval itv = {{0, 0}, {EVENT_TIMEOUT_SEC - msg_age, 0}};
 243                 dbg("next event expires in %li seconds", EVENT_TIMEOUT_SEC - msg_age);
 244                 setitimer(ITIMER_REAL, &itv, 0);
 245         }
 246 }
 247
 248 /* receive the msg, do some basic sanity checks, and queue it */
 249 static void handle_msg(int sock)
 250 {
 251         struct hotplug_msg *msg;
 252         int retval;
 253         struct msghdr smsg;
 254         struct cmsghdr *cmsg;
 255         struct iovec iov;
 256         struct ucred *cred;
 257         char cred_msg[CMSG_SPACE(sizeof(struct ucred))];
 258
 259         msg = msg_create();
 260         if (msg == NULL) {
 261                 dbg("unable to store message");
 262                 return;
 263         }
 264
 265         iov.iov_base = msg;
 266         iov.iov_len = sizeof(struct hotplug_msg);
 267
 268         memset(&smsg, 0x00, sizeof(struct msghdr));
 269         smsg.msg_iov = &iov;
 270         smsg.msg_iovlen = 1;
 271         smsg.msg_control = cred_msg;
 272         smsg.msg_controllen = sizeof(cred_msg);
 273
 274         retval = recvmsg(sock, &smsg, 0);
 275         if (retval <  0) {
 276                 if (errno != EINTR)
 277                         dbg("unable to receive message");
 278                 return;
 279         }
 280         cmsg = CMSG_FIRSTHDR(&smsg);
 281         cred = (struct ucred *) CMSG_DATA(cmsg);
 282
 283         if (cmsg == NULL || cmsg->cmsg_type != SCM_CREDENTIALS) {
 284                 dbg("no sender credentials received, message ignored");
 285                 goto skip;
 286         }
 287
 288         if (cred->uid != 0) {
 289                 dbg("sender uid=%i, message ignored", cred->uid);
 290                 goto skip;
 291         }
 292
 293         if (strncmp(msg->magic, UDEV_MAGIC, sizeof(UDEV_MAGIC)) != 0 ) {
 294                 dbg("message magic '%s' doesn't match, ignore it", msg->magic);
 295                 goto skip;
 296         }
 297
 298         /* if no seqnum is given, we move straight to exec queue */
 299         if (msg->seqnum == -1) {
 300                 list_add(&msg->list, &exec_list);
 301                 run_exec_q = 1;
 302         } else {
 303                 msg_queue_insert(msg);
 304         }
 305         return;
 306
 307 skip:
 308         free(msg);
 309         return;
 310 }
 311
 312 asmlinkage static void sig_handler(int signum)
 313 {
 314         int rc;
 315
 316         switch (signum) {
 317                 case SIGINT:
 318                 case SIGTERM:
 319                         exit(20 + signum);
 320                         break;
 321                 case SIGALRM:
 322                         /* set flag, then write to pipe if needed */
 323                         run_msg_q = 1;
 324                         goto do_write;
 325                         break;
 326                 case SIGCHLD:
 327                         /* set flag, then write to pipe if needed */
 328                         children_waiting = 1;
 329                         goto do_write;
 330                         break;
 331                 default:
 332                         dbg("unhandled signal %d", signum);
 333                         return;
 334         }
 335
 336 do_write:
 337         /* if pipe is empty, write to pipe to force select to return
 338          * immediately when it gets called
 339          */
 340         if (!sig_flag) {
 341                 rc = write(pipefds[1],&signum,sizeof(signum));
 342                 if (rc < 0)
 343                         dbg("unable to write to pipe");
 344                 else
 345                         sig_flag = 1;
 346         }
 347 }
 348
 349 static void udev_done(int pid)
 350 {
 351         /* find msg associated with pid and delete it */
 352         struct hotplug_msg *msg;
 353
 354         list_for_each_entry(msg, &running_list, list) {
 355                 if (msg->pid == pid) {
 356                         dbg("<== exec seq %li came back", msg->seqnum);
 357                         run_queue_delete(msg);
 358
 359                         /* we want to run the exec queue manager since there may
 360                          * be events waiting with the devpath of the one that
 361                          * just finished
 362                          */
 363                         run_exec_q = 1;
 364                         return;
 365                 }
 366         }
 367 }
 368
 369 static void reap_kids()
 370 {
 371         /* reap all dead children */
 372         while(1) {
 373                 int pid = waitpid(-1, 0, WNOHANG);
 374                 if ((pid == -1) || (pid == 0))
 375                         break;
 376                 udev_done(pid);
 377         }
 378 }
 379
 380 /* just read everything from the pipe and clear the flag,
 381  * the useful flags were set in the signal handler
 382  */
 383 static void user_sighandler()
 384 {
 385         int sig;
 386         while(1) {
 387                 int rc = read(pipefds[0],&sig,sizeof(sig));
 388                 if (rc < 0)
 389                         break;
 390
 391                 sig_flag = 0;
 392         }
 393 }
 394
 395
 396 int main(int argc, char *argv[])
 397 {
 398         int ssock, maxsockplus;
 399         struct sockaddr_un saddr;
 400         socklen_t addrlen;
 401         int retval;
 402         const int on = 1;
 403         struct sigaction act;
 404         fd_set readfds;
 405
 406         init_logging("udevd");
 407         dbg("version %s", UDEV_VERSION);
 408
 409         if (getuid() != 0) {
 410                 dbg("need to be root, exit");
 411                 exit(1);
 412         }
 413
 414         /* setup signal handler pipe */
 415         retval = pipe(pipefds);
 416         if (retval < 0) {
 417                 dbg("error getting pipes: %s", strerror(errno));
 418                 exit(1);
 419         }
 420
 421         retval = fcntl(pipefds[0], F_SETFL, O_NONBLOCK);
 422                 if (retval < 0) {
 423                 dbg("error fcntl on read pipe: %s", strerror(errno));
 424                 exit(1);
 425         }
 426
 427         retval = fcntl(pipefds[1], F_SETFL, O_NONBLOCK);
 428         if (retval < 0) {
 429                 dbg("error fcntl on write pipe: %s", strerror(errno));
 430                 exit(1);
 431         }
 432
 433         /* set signal handlers */
 434         act.sa_handler = sig_handler;
 435         sigemptyset(&act.sa_mask);
 436         act.sa_flags = SA_RESTART;
 437         sigaction(SIGINT, &act, NULL);
 438         sigaction(SIGTERM, &act, NULL);
 439         sigaction(SIGALRM, &act, NULL);
 440         sigaction(SIGCHLD, &act, NULL);
 441
 442         memset(&saddr, 0x00, sizeof(saddr));
 443         saddr.sun_family = AF_LOCAL;
 444         /* use abstract namespace for socket path */
 445         strcpy(&saddr.sun_path[1], UDEVD_SOCK_PATH);
 446         addrlen = offsetof(struct sockaddr_un, sun_path) + strlen(saddr.sun_path+1) + 1;
 447
 448         ssock = socket(AF_LOCAL, SOCK_DGRAM, 0);
 449         if (ssock == -1) {
 450                 dbg("error getting socket, exit");
 451                 exit(1);
 452         }
 453
 454         /* the bind takes care of ensuring only one copy running */
 455         retval = bind(ssock, (struct sockaddr *) &saddr, addrlen);
 456         if (retval < 0) {
 457                 dbg("bind failed, exit");
 458                 goto exit;
 459         }
 460
 461         /* enable receiving of the sender credentials */
 462         setsockopt(ssock, SOL_SOCKET, SO_PASSCRED, &on, sizeof(on));
 463
 464         /* possible override of udev binary, used for testing */
 465         udev_bin = getenv("UDEV_BIN");
 466         if (udev_bin != NULL)
 467                 dbg("udev binary is set to '%s'", udev_bin);
 468         else
 469                 udev_bin = UDEV_BIN;
 470
 471         FD_ZERO(&readfds);
 472         FD_SET(ssock, &readfds);
 473         FD_SET(pipefds[0], &readfds);
 474         maxsockplus = ssock+1;
 475         while (1) {
 476                 fd_set workreadfds = readfds;
 477                 retval = select(maxsockplus, &workreadfds, NULL, NULL, NULL);
 478
 479                 if (retval < 0) {
 480                         if (errno != EINTR)
 481                                 dbg("error in select: %s", strerror(errno));
 482                         continue;
 483                 }
 484
 485                 if (FD_ISSET(ssock, &workreadfds))
 486                         handle_msg(ssock);
 487
 488                 if (FD_ISSET(pipefds[0], &workreadfds))
 489                         user_sighandler();
 490
 491                 if (children_waiting) {
 492                         children_waiting = 0;
 493                         reap_kids();
 494                 }
 495
 496                 if (run_msg_q) {
 497                         run_msg_q = 0;
 498                         msg_queue_manager();
 499                 }
 500
 501                 if (run_exec_q) {
 502                         /* this is tricky.  exec_queue_manager() loops over exec_list, and
 503                          * calls running_with_devpath(), which loops over running_list. This gives
 504                          * O(N*M), which can get *nasty*.  Clean up running_list before
 505                          * calling exec_queue_manager().
 506                          */
 507                         if (children_waiting) {
 508                                 children_waiting = 0;
 509                                 reap_kids();
 510                         }
 511
 512                         run_exec_q = 0;
 513                         exec_queue_manager();
 514                 }
 515         }
 516 exit:
 517         close(ssock);
 518         exit(1);
 519 }