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Sourcecode: udev version File versions

udevd.c

/*
 * udevd.c - hotplug event serializer
 *
 * Copyright (C) 2004-2005 Kay Sievers <kay.sievers@vrfy.org>
 * Copyright (C) 2004 Chris Friesen <chris_friesen@sympatico.ca>
 *
 *
 *    This program is free software; you can redistribute it and/or modify it
 *    under the terms of the GNU General Public License as published by the
 *    Free Software Foundation version 2 of the License.
 *
 *    This program is distributed in the hope that it will be useful, but
 *    WITHOUT ANY WARRANTY; without even the implied warranty of
 *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 *    General Public License for more details.
 *
 *    You should have received a copy of the GNU General Public License along
 *    with this program; if not, write to the Free Software Foundation, Inc.,
 *    675 Mass Ave, Cambridge, MA 02139, USA.
 *
 */

#include <stddef.h>
#include <signal.h>
#include <unistd.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <dirent.h>
#include <fcntl.h>
#include <sys/select.h>
#include <sys/wait.h>
#include <sys/time.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/un.h>
#include <sys/sysinfo.h>
#include <sys/stat.h>

#include "list.h"
#include "udev_libc_wrapper.h"
#include "udev.h"
#include "udev_version.h"
#include "udev_utils.h"
#include "udevd.h"
#include "logging.h"

/* global variables*/
static int udevsendsock;
static pid_t sid;

static int pipefds[2];
static long startup_time;
static unsigned long long expected_seqnum = 0;
static volatile int sigchilds_waiting;
static volatile int run_msg_q;
static volatile int sig_flag;
static int run_exec_q;

static LIST_HEAD(msg_list);
static LIST_HEAD(exec_list);
static LIST_HEAD(running_list);

static void exec_queue_manager(void);
static void msg_queue_manager(void);
static void user_sighandler(void);
static void reap_sigchilds(void);
char *udev_bin;

#ifdef USE_LOG
void log_message (int level, const char *format, ...)
{
      va_list     args;

      va_start(args, format);
      vsyslog(level, format, args);
      va_end(args);
}
#endif

#define msg_dump(msg) \
      dbg("msg_dump: sequence %llu, '%s', '%s', '%s'", \
      msg->seqnum, msg->action, msg->devpath, msg->subsystem);

static void msg_dump_queue(void)
{
#ifdef DEBUG
      struct hotplug_msg *msg;

      list_for_each_entry(msg, &msg_list, node)
            dbg("sequence %llu in queue", msg->seqnum);
#endif
}

static void run_queue_delete(struct hotplug_msg *msg)
{
      list_del(&msg->node);
      free(msg);
}

/* orders the message in the queue by sequence number */
static void msg_queue_insert(struct hotplug_msg *msg)
{
      struct hotplug_msg *loop_msg;
      struct sysinfo info;

      if (msg->seqnum == 0) {
            dbg("no SEQNUM, move straight to the exec queue");
            list_add(&msg->node, &exec_list);
            run_exec_q = 1;
            return;
      }

      /* don't delay messages with timeout set */
      if (msg->timeout) {
            dbg("move seq %llu with timeout %u to exec queue", msg->seqnum, msg->timeout);
            list_add(&msg->node, &exec_list);
            run_exec_q = 1;
            return;
      }

      /* sort message by sequence number into list */
      list_for_each_entry_reverse(loop_msg, &msg_list, node) {
            if (loop_msg->seqnum < msg->seqnum)
                  break;

            if (loop_msg->seqnum == msg->seqnum) {
                  dbg("ignoring duplicate message seq %llu", msg->seqnum);
                  return;
            }
      }

      /* store timestamp of queuing */
      sysinfo(&info);
      msg->queue_time = info.uptime;

      list_add(&msg->node, &loop_msg->node);
      dbg("queued message seq %llu", msg->seqnum);

      /* run msg queue manager */
      run_msg_q = 1;

      return;
}

/* forks event and removes event from run queue when finished */
static void udev_run(struct hotplug_msg *msg)
{
      char *const argv[] = { "udev", msg->subsystem, NULL };
      pid_t pid;

      pid = fork();
      switch (pid) {
      case 0:
            /* child */
            close(udevsendsock);
            logging_close();

            setpriority(PRIO_PROCESS, 0, UDEV_PRIORITY);
            execve(udev_bin, argv, msg->envp);
            dbg("exec of child failed");
            _exit(1);
            break;
      case -1:
            dbg("fork of child failed");
            run_queue_delete(msg);
            break;
      default:
            /* get SIGCHLD in main loop */
            dbg("==> exec seq %llu [%d] working at '%s'", msg->seqnum, pid, msg->devpath);
            msg->pid = pid;
      }
}

static int running_processes(void)
{
      int f;
      static char buf[4096];
      int len;
      int running;
      const char *pos;

      f = open("/proc/stat", O_RDONLY);
      if (f == -1)
            return -1;

      len = read(f, buf, sizeof(buf));
      close(f);

      if (len <= 0)
            return -1;
      else
            buf[len] = '\0';

      pos = strstr(buf, "procs_running ");
      if (pos == NULL)
            return -1;

      if (sscanf(pos, "procs_running %u", &running) != 1)
            return -1;

      return running;
}

/* return the number of process es in our session, count only until limit */
static int running_processes_in_session(pid_t session, int limit)
{
      DIR *dir;
      struct dirent *dent;
      int running = 0;

      dir = opendir("/proc");
      if (!dir)
            return -1;

      /* read process info from /proc */
      for (dent = readdir(dir); dent != NULL; dent = readdir(dir)) {
            int f;
            char procdir[64];
            char line[256];
            const char *pos;
            char state;
            pid_t ppid, pgrp, sess;
            int len;

            if (!isdigit(dent->d_name[0]))
                  continue;

            snprintf(procdir, sizeof(procdir), "/proc/%s/stat", dent->d_name);
            procdir[sizeof(procdir)-1] = '\0';

            f = open(procdir, O_RDONLY);
            if (f == -1)
                  continue;

            len = read(f, line, sizeof(line));
            close(f);

            if (len <= 0)
                  continue;
            else
                  line[len] = '\0';

            /* skip ugly program name */
            pos = strrchr(line, ')') + 2;
            if (pos == NULL)
                  continue;

            if (sscanf(pos, "%c %d %d %d ", &state, &ppid, &pgrp, &sess) != 4)
                  continue;

            /* count only processes in our session */
            if (sess != session)
                  continue;

            /* count only running, no sleeping processes */
            if (state != 'R')
                  continue;

            running++;
            if (limit > 0 && running >= limit)
                  break;
      }
      closedir(dir);

      return running;
}

static int compare_devpath(const char *running, const char *waiting)
{
      int i;

      for (i = 0; i < PATH_SIZE; i++) {
            /* identical device event found */
            if (running[i] == '\0' && waiting[i] == '\0')
                  return 1;

            /* parent device event found */
            if (running[i] == '\0' && waiting[i] == '/')
                  return 2;

            /* child device event found */
            if (running[i] == '/' && waiting[i] == '\0')
                  return 3;

            /* no matching event */
            if (running[i] != waiting[i])
                  break;
      }

      return 0;
}

/* returns still running task for the same device, its parent or its physical device */
static struct hotplug_msg *running_with_devpath(struct hotplug_msg *msg)
{
      struct hotplug_msg *loop_msg;

      if (msg->devpath == NULL)
            return NULL;

      /* skip any events with a timeout set */
      if (msg->timeout)
            return NULL;

      list_for_each_entry(loop_msg, &running_list, node) {
            if (loop_msg->devpath == NULL)
                  continue;

            /* return running parent/child device event */
            if (compare_devpath(loop_msg->devpath, msg->devpath) != 0)
                  return loop_msg;

            /* return running physical device event */
            if (msg->physdevpath && msg->action && strcmp(msg->action, "add") == 0)
                  if (compare_devpath(loop_msg->devpath, msg->physdevpath) != 0)
                        return loop_msg;
      }

      return NULL;
}

/* exec queue management routine executes the events and serializes events in the same sequence */
static void exec_queue_manager(void)
{
      struct hotplug_msg *loop_msg;
      struct hotplug_msg *tmp_msg;
      struct hotplug_msg *msg;
      int running;

      running = running_processes();
      dbg("%d processes runnning on system", running);
      if (running < 0)
            running = THROTTLE_MAX_RUNNING_CHILDS;

      list_for_each_entry_safe(loop_msg, tmp_msg, &exec_list, node) {
            /* check running processes in our session and possibly throttle */
            if (running >= THROTTLE_MAX_RUNNING_CHILDS) {
                  running = running_processes_in_session(sid, THROTTLE_MAX_RUNNING_CHILDS+10);
                  dbg("%d processes running in session", running);
                  if (running >= THROTTLE_MAX_RUNNING_CHILDS) {
                        dbg("delay seq %llu, cause too many processes already running", loop_msg->seqnum);
                        return;
                  }
            }

            msg = running_with_devpath(loop_msg);
            if (!msg) {
                  /* move event to run list */
                  list_move_tail(&loop_msg->node, &running_list);
                  udev_run(loop_msg);
                  running++;
                  dbg("moved seq %llu to running list", loop_msg->seqnum);
            } else {
                  dbg("delay seq %llu (%s), cause seq %llu (%s) is still running",
                      loop_msg->seqnum, loop_msg->devpath, msg->seqnum, msg->devpath);
            }
      }
}

static void msg_move_exec(struct hotplug_msg *msg)
{
      list_move_tail(&msg->node, &exec_list);
      run_exec_q = 1;
      expected_seqnum = msg->seqnum+1;
      dbg("moved seq %llu to exec, next expected is %llu",
            msg->seqnum, expected_seqnum);
}

/* msg queue management routine handles the timeouts and dispatches the events */
static void msg_queue_manager(void)
{
      struct hotplug_msg *loop_msg;
      struct hotplug_msg *tmp_msg;
      struct sysinfo info;
      long msg_age = 0;
      static int timeout = EVENT_INIT_TIMEOUT_SEC;
      static int init = 1;

      dbg("msg queue manager, next expected is %llu", expected_seqnum);
recheck:
      list_for_each_entry_safe(loop_msg, tmp_msg, &msg_list, node) {
            /* move event with expected sequence to the exec list */
            if (loop_msg->seqnum == expected_seqnum) {
                  msg_move_exec(loop_msg);
                  continue;
            }

            /* see if we are in the initialization phase and wait for the very first events */
            if (init && (info.uptime - startup_time >= INIT_TIME_SEC)) {
                  init = 0;
                  timeout = EVENT_TIMEOUT_SEC;
                  dbg("initialization phase passed, set timeout to %i seconds", EVENT_TIMEOUT_SEC);
            }

            /* move event with expired timeout to the exec list */
            sysinfo(&info);
            msg_age = info.uptime - loop_msg->queue_time;
            dbg("seq %llu is %li seconds old", loop_msg->seqnum, msg_age);
            if (msg_age >= timeout) {
                  msg_move_exec(loop_msg);
                  goto recheck;
            } else {
                  break;
            }
      }

      msg_dump_queue();

      /* set timeout for remaining queued events */
      if (list_empty(&msg_list) == 0) {
            struct itimerval itv = {{0, 0}, {timeout - msg_age, 0}};
            dbg("next event expires in %li seconds", timeout - msg_age);
            setitimer(ITIMER_REAL, &itv, NULL);
      }
}

/* receive the udevsend message and do some sanity checks */
static struct hotplug_msg *get_udevsend_msg(void)
{
      static struct udevsend_msg usend_msg;
      struct hotplug_msg *msg;
      int bufpos;
      int i;
      ssize_t size;
      struct msghdr smsg;
      struct cmsghdr *cmsg;
      struct iovec iov;
      struct ucred *cred;
      char cred_msg[CMSG_SPACE(sizeof(struct ucred))];
      int envbuf_size;

      memset(&usend_msg, 0x00, sizeof(struct udevsend_msg));
      iov.iov_base = &usend_msg;
      iov.iov_len = sizeof(struct udevsend_msg);

      memset(&smsg, 0x00, sizeof(struct msghdr));
      smsg.msg_iov = &iov;
      smsg.msg_iovlen = 1;
      smsg.msg_control = cred_msg;
      smsg.msg_controllen = sizeof(cred_msg);

      size = recvmsg(udevsendsock, &smsg, 0);
      if (size <  0) {
            if (errno != EINTR)
                  dbg("unable to receive udevsend message");
            return NULL;
      }
      cmsg = CMSG_FIRSTHDR(&smsg);
      cred = (struct ucred *) CMSG_DATA(cmsg);

      if (cmsg == NULL || cmsg->cmsg_type != SCM_CREDENTIALS) {
            dbg("no sender credentials received, message ignored");
            return NULL;
      }

      if (cred->uid != 0) {
            dbg("sender uid=%i, message ignored", cred->uid);
            return NULL;
      }

      if (strncmp(usend_msg.magic, UDEV_MAGIC, sizeof(UDEV_MAGIC)) != 0 ) {
            dbg("message magic '%s' doesn't match, ignore it", usend_msg.magic);
            return NULL;
      }

      envbuf_size = size - offsetof(struct udevsend_msg, envbuf);
      dbg("envbuf_size=%i", envbuf_size);
      msg = malloc(sizeof(struct hotplug_msg) + envbuf_size);
      if (msg == NULL)
            return NULL;

      memset(msg, 0x00, sizeof(struct hotplug_msg) + envbuf_size);

      /* copy environment buffer and reconstruct envp */
      memcpy(msg->envbuf, usend_msg.envbuf, envbuf_size);
      bufpos = 0;
      for (i = 0; (bufpos < envbuf_size) && (i < HOTPLUG_NUM_ENVP-2); i++) {
            int keylen;
            char *key;

            key = &msg->envbuf[bufpos];
            keylen = strlen(key);
            msg->envp[i] = key;
            bufpos += keylen + 1;
            dbg("add '%s' to msg.envp[%i]", msg->envp[i], i);

            /* remember some keys for further processing */
            if (strncmp(key, "ACTION=", 7) == 0)
                  msg->action = &key[7];

            if (strncmp(key, "DEVPATH=", 8) == 0)
                  msg->devpath = &key[8];

            if (strncmp(key, "SUBSYSTEM=", 10) == 0)
                  msg->subsystem = &key[10];

            if (strncmp(key, "SEQNUM=", 7) == 0)
                  msg->seqnum = strtoull(&key[7], NULL, 10);

            if (strncmp(key, "PHYSDEVPATH=", 12) == 0)
                  msg->physdevpath = &key[12];

            if (strncmp(key, "TIMEOUT=", 8) == 0)
                  msg->timeout = strtoull(&key[8], NULL, 10);
      }
      msg->envp[i++] = "UDEVD_EVENT=1";
      msg->envp[i] = NULL;

      return msg;
}

static void asmlinkage sig_handler(int signum)
{
      int rc;

      switch (signum) {
            case SIGINT:
            case SIGTERM:
                  exit(20 + signum);
                  break;
            case SIGALRM:
                  /* set flag, then write to pipe if needed */
                  run_msg_q = 1;
                  goto do_write;
                  break;
            case SIGCHLD:
                  /* set flag, then write to pipe if needed */
                  sigchilds_waiting = 1;
                  goto do_write;
                  break;
      }

do_write:
      /* if pipe is empty, write to pipe to force select to return
       * immediately when it gets called
       */
      if (!sig_flag) {
            rc = write(pipefds[1],&signum,sizeof(signum));
            if (rc >= 0)
                  sig_flag = 1;
      }
}

static void udev_done(int pid)
{
      /* find msg associated with pid and delete it */
      struct hotplug_msg *msg;

      list_for_each_entry(msg, &running_list, node) {
            if (msg->pid == pid) {
                  dbg("<== exec seq %llu came back", msg->seqnum);
                  run_queue_delete(msg);

                  /* we want to run the exec queue manager since there may
                   * be events waiting with the devpath of the one that
                   * just finished
                   */
                  run_exec_q = 1;
                  return;
            }
      }
}

static void reap_sigchilds(void)
{
      while(1) {
            int pid = waitpid(-1, NULL, WNOHANG);
            if ((pid == -1) || (pid == 0))
                  break;
            udev_done(pid);
      }
}

/* just read everything from the pipe and clear the flag,
 * the flags was set in the signal handler
 */
static void user_sighandler(void)
{
      int sig;

      while(1) {
            int rc = read(pipefds[0], &sig, sizeof(sig));
            if (rc < 0)
                  break;

            sig_flag = 0;
      }
}

static int init_udevsend_socket(void)
{
      struct sockaddr_un saddr;
      socklen_t addrlen;
      const int feature_on = 1;
      int retval;

      memset(&saddr, 0x00, sizeof(saddr));
      saddr.sun_family = AF_LOCAL;
      /* use abstract namespace for socket path */
      strcpy(&saddr.sun_path[1], UDEVD_SOCK_PATH);
      addrlen = offsetof(struct sockaddr_un, sun_path) + strlen(saddr.sun_path+1) + 1;

      udevsendsock = socket(AF_LOCAL, SOCK_DGRAM, 0);
      if (udevsendsock == -1) {
            dbg("error getting socket, %s", strerror(errno));
            return -1;
      }

      /* the bind takes care of ensuring only one copy running */
      retval = bind(udevsendsock, (struct sockaddr *) &saddr, addrlen);
      if (retval < 0) {
            dbg("bind failed, %s", strerror(errno));
            close(udevsendsock);
            return -1;
      }

      /* enable receiving of the sender credentials */
      setsockopt(udevsendsock, SOL_SOCKET, SO_PASSCRED, &feature_on, sizeof(feature_on));

      return 0;
}

int main(int argc, char *argv[], char *envp[])
{
      struct sysinfo info;
      int maxsockplus;
      int retval;
      int fd;
      struct sigaction act;
      fd_set readfds;
      const char *udevd_expected_seqnum;

      logging_init("udevd");
      dbg("version %s", UDEV_VERSION);

      if (getuid() != 0) {
            dbg("need to be root, exit");
            goto exit;
      }

      /* daemonize on request */
      if (argc == 2 && strcmp(argv[1], "-d") == 0) {
            pid_t pid;

            pid = fork();
            switch (pid) {
            case 0:
                  dbg("damonized fork running");
                  break;
            case -1:
                  dbg("fork of daemon failed");
                  goto exit;
            default:
                  logging_close();
                  exit(0);
            }
      }

      /* become session leader */
      sid = setsid();
      dbg("our session is %d", sid);

      /* make sure we don't lock any path */
      chdir("/");
      umask(umask(077) | 022);

      /*set a reasonable scheduling priority for the daemon */
      setpriority(PRIO_PROCESS, 0, UDEVD_PRIORITY);

      /* Set fds to dev/null */
      fd = open( "/dev/null", O_RDWR );
      if (fd >= 0)  {
            dup2(fd, 0);
            dup2(fd, 1);
            dup2(fd, 2);
            if (fd > 2)
                  close(fd);
      } else
            dbg("error opening /dev/null %s", strerror(errno));

      /* setup signal handler pipe */
      retval = pipe(pipefds);
      if (retval < 0) {
            dbg("error getting pipes: %s", strerror(errno));
            goto exit;
      }

      retval = fcntl(pipefds[0], F_SETFL, O_NONBLOCK);
      if (retval < 0) {
            dbg("error fcntl on read pipe: %s", strerror(errno));
            goto exit;
      }
      retval = fcntl(pipefds[0], F_SETFD, FD_CLOEXEC);
      if (retval < 0)
            dbg("error fcntl on read pipe: %s", strerror(errno));

      retval = fcntl(pipefds[1], F_SETFL, O_NONBLOCK);
      if (retval < 0) {
            dbg("error fcntl on write pipe: %s", strerror(errno));
            goto exit;
      }
      retval = fcntl(pipefds[1], F_SETFD, FD_CLOEXEC);
      if (retval < 0)
            dbg("error fcntl on write pipe: %s", strerror(errno));

      /* set signal handlers */
      memset(&act, 0x00, sizeof(struct sigaction));
      act.sa_handler = (void (*) (int))sig_handler;
      sigemptyset(&act.sa_mask);
      act.sa_flags = SA_RESTART;
      sigaction(SIGINT, &act, NULL);
      sigaction(SIGTERM, &act, NULL);
      sigaction(SIGALRM, &act, NULL);
      sigaction(SIGCHLD, &act, NULL);

      if (init_udevsend_socket() < 0) {
            if (errno == EADDRINUSE)
                  dbg("another udevd running, exit");
            else
                  dbg("error initialising udevsend socket: %s", strerror(errno));

            goto exit;
      }

      /* possible override of udev binary, used for testing */
      udev_bin = getenv("UDEV_BIN");
      if (udev_bin != NULL)
            dbg("udev binary is set to '%s'", udev_bin);
      else
            udev_bin = UDEV_BIN;

      /* possible init of expected_seqnum value */
      udevd_expected_seqnum = getenv("UDEVD_EXPECTED_SEQNUM");
      if (udevd_expected_seqnum != NULL) {
            expected_seqnum = strtoull(udevd_expected_seqnum, NULL, 10);
            dbg("initialize expected_seqnum to %llu", expected_seqnum);
      }

      /* get current time to provide shorter timeout on startup */
      sysinfo(&info);
      startup_time = info.uptime;

      FD_ZERO(&readfds);
      FD_SET(udevsendsock, &readfds);
      FD_SET(pipefds[0], &readfds);
      maxsockplus = udevsendsock+1;
      while (1) {
            struct hotplug_msg *msg;

            fd_set workreadfds = readfds;
            retval = select(maxsockplus, &workreadfds, NULL, NULL, NULL);

            if (retval < 0) {
                  if (errno != EINTR)
                        dbg("error in select: %s", strerror(errno));
                  continue;
            }

            if (FD_ISSET(udevsendsock, &workreadfds)) {
                  msg = get_udevsend_msg();
                  if (msg)
                        msg_queue_insert(msg);
            }

            if (FD_ISSET(pipefds[0], &workreadfds))
                  user_sighandler();

            if (sigchilds_waiting) {
                  sigchilds_waiting = 0;
                  reap_sigchilds();
            }

            if (run_msg_q) {
                  run_msg_q = 0;
                  msg_queue_manager();
            }

            if (run_exec_q) {
                   /* clean up running_list before calling exec_queue_manager() */
                  if (sigchilds_waiting) {
                        sigchilds_waiting = 0;
                        reap_sigchilds();
                  }

                  run_exec_q = 0;
                  exec_queue_manager();
            }
      }

exit:
      logging_close();
      return 1;
}

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