| /**************************************************************************** |
| * apps/fsutils/passwd/passwd_lock.c |
| * |
| * Copyright (C) 2016 Gregory Nutt. All rights reserved. |
| * Author: Gregory Nutt <gnutt@nuttx.org> |
| * |
| * Redistribution and use in source and binary forms, with or without |
| * modification, are permitted provided that the following conditions |
| * are met: |
| * |
| * 1. Redistributions of source code must retain the above copyright |
| * notice, this list of conditions and the following disclaimer. |
| * 2. Redistributions in binary form must reproduce the above copyright |
| * notice, this list of conditions and the following disclaimer in |
| * the documentation and/or other materials provided with the |
| * distribution. |
| * 3. Neither the name NuttX nor the names of its contributors may be |
| * used to endorse or promote products derived from this software |
| * without specific prior written permission. |
| * |
| * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
| * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
| * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS |
| * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE |
| * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, |
| * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, |
| * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS |
| * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED |
| * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT |
| * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN |
| * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE |
| * POSSIBILITY OF SUCH DAMAGE. |
| * |
| ****************************************************************************/ |
| |
| /**************************************************************************** |
| * Included Files |
| ****************************************************************************/ |
| |
| #include <semaphore.h> |
| #include <assert.h> |
| #include <errno.h> |
| |
| #include "passwd.h" |
| |
| /**************************************************************************** |
| * Pre-processor Definitions |
| ****************************************************************************/ |
| |
| #ifdef CONFIG_BUILD_KERNEL |
| /* In the kernel build mode, we need to use a named semaphore so that all |
| * processes will share the same, named semaphore instance. |
| */ |
| |
| # define PASSWD_SEMNAME "pwsem" /* Global named semaphore */ |
| #endif |
| |
| /**************************************************************************** |
| * Private Data |
| ****************************************************************************/ |
| |
| #ifndef CONFIG_BUILD_KERNEL |
| /* In the FLAT and PROTECTED build modes, we do not need to bother with a |
| * named semaphore. We use a single global semaphore in theses cases. |
| */ |
| |
| static sem_t g_passwd_sem = SEM_INITIALIZER(1); |
| #endif |
| |
| /**************************************************************************** |
| * Public Functions |
| ****************************************************************************/ |
| /**************************************************************************** |
| * Name: passwd_lock and passwd_unlock |
| * |
| * Description: |
| * Lock the /etc/passwd file. This is not a real lock at the level of the |
| * file system. Rather, it only prevents concurrent modification of the |
| * /etc/passwd file by passwd_adduser(), passwd_deluser(), and |
| * passwd_update(). Other accesses to /etc/passwd could still cause |
| * concurrency problem and file corruption. |
| * |
| * Input Parameters: |
| * |
| * Returned Value: |
| * Zero (OK) is returned on success; a negated errno value is returned on |
| * failure. |
| * |
| ****************************************************************************/ |
| |
| int passwd_lock(FAR sem_t **semp) |
| { |
| FAR sem_t *sem; |
| |
| #ifdef CONFIG_BUILD_KERNEL |
| /* Open the shared, named semaphore */ |
| |
| sem = sem_open(PASSWD_SEMNAME, O_CREAT, 0644, 1); |
| if (sem == NULL) |
| { |
| int errcode = errno; |
| DEBUGASSERT(errcode > 0); |
| return -errcode; |
| } |
| #else |
| /* Use the global semaphore */ |
| |
| sem = &g_passwd_sem; |
| #endif |
| |
| /* Take the semaphore. Only EINTR errors are expected. */ |
| |
| while (sem_wait(sem) < 0) |
| { |
| int errcode = errno; |
| DEBUGASSERT(errcode == EINTR); |
| UNUSED(errcode); |
| } |
| |
| *semp = sem; |
| return OK; |
| } |
| |
| int passwd_unlock(FAR sem_t *sem) |
| { |
| /* Release our count on the semaphore */ |
| |
| sem_post(sem); |
| |
| #ifdef CONFIG_BUILD_KERNEL |
| /* Close the named semaphore */ |
| |
| (void)sem_close(sem); |
| #endif |
| |
| return OK; |
| } |