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/* vi: set sw=4 ts=4: */
/* Handle locking of password file.
Copyright (C) 1996,98,2000,02 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by Ulrich Drepper <drepper@cygnus.com>, 1996.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library 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
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<http://www.gnu.org/licenses/>. */
#include <features.h>
#include <fcntl.h>
#include <signal.h>
#include <string.h>
#include <unistd.h>
#include <sys/file.h>
#include <paths.h>
#include <shadow.h>
/* How long to wait for getting the lock before returning with an error. */
#define TIMEOUT 15 /* sec */
/* File descriptor for lock file. */
static int lock_fd = -1;
/* Prevent problems in multithreaded program by using mutex. */
#include <bits/uClibc_mutex.h>
__UCLIBC_MUTEX_STATIC(mylock, PTHREAD_MUTEX_INITIALIZER);
/* Prototypes for local functions. */
static void noop_handler (int __sig);
int
lckpwdf (void)
{
sigset_t saved_set; /* Saved set of caught signals. */
struct sigaction saved_act; /* Saved signal action. */
sigset_t new_set; /* New set of caught signals. */
struct sigaction new_act; /* New signal action. */
struct flock fl; /* Information struct for locking. */
int result;
int rv = -1;
if (lock_fd != -1)
/* Still locked by own process. */
return -1;
/* Prevent problems caused by multiple threads. */
__UCLIBC_MUTEX_LOCK(mylock);
lock_fd = open (_PATH_PASSWD, O_WRONLY | O_CLOEXEC);
if (lock_fd == -1) {
goto DONE;
}
#ifndef __ASSUME_O_CLOEXEC
/* Make sure file gets correctly closed when process finished. */
fcntl (lock_fd, F_SETFD, FD_CLOEXEC);
#endif
/* Now we have to get exclusive write access. Since multiple
process could try this we won't stop when it first fails.
Instead we set a timeout for the system call. Once the timer
expires it is likely that there are some problems which cannot be
resolved by waiting. (sa_flags have no SA_RESTART. Thus SIGALRM
will EINTR fcntl(F_SETLKW)
It is important that we don't change the signal state. We must
restore the old signal behaviour. */
memset (&new_act, '\0', sizeof (new_act));
new_act.sa_handler = noop_handler;
__sigfillset (&new_act.sa_mask);
/* Install new action handler for alarm and save old.
* This never fails in Linux. */
sigaction (SIGALRM, &new_act, &saved_act);
/* Now make sure the alarm signal is not blocked. */
__sigemptyset (&new_set);
__sigaddset (&new_set, SIGALRM);
sigprocmask (SIG_UNBLOCK, &new_set, &saved_set);
/* Start timer. If we cannot get the lock in the specified time we
get a signal. */
alarm (TIMEOUT);
/* Try to get the lock. */
memset (&fl, '\0', sizeof (fl));
if (F_WRLCK)
fl.l_type = F_WRLCK;
if (SEEK_SET)
fl.l_whence = SEEK_SET;
result = fcntl (lock_fd, F_SETLKW, &fl);
/* Clear alarm. */
alarm (0);
sigprocmask (SIG_SETMASK, &saved_set, NULL);
sigaction (SIGALRM, &saved_act, NULL);
if (result < 0) {
close(lock_fd);
lock_fd = -1;
goto DONE;
}
rv = 0;
DONE:
__UCLIBC_MUTEX_UNLOCK(mylock);
return rv;
}
int
ulckpwdf (void)
{
int result;
if (lock_fd == -1)
/* There is no lock set. */
result = -1;
else
{
/* Prevent problems caused by multiple threads. */
__UCLIBC_MUTEX_LOCK(mylock);
result = close (lock_fd);
/* Mark descriptor as unused. */
lock_fd = -1;
/* Clear mutex. */
__UCLIBC_MUTEX_UNLOCK(mylock);
}
return result;
}
static void
noop_handler (int sig attribute_unused) {
/* We simply return which makes the `fcntl' call return with an error. */
}
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