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nuttx/fs/fs_syslog.c

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/****************************************************************************
* fs/syslog.c
*
* Copyright (C) 2012 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 <nuttx/config.h>
#include <sys/types.h>
#include <stdint.h>
#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>
#include <semaphore.h>
#include <errno.h>
#include <assert.h>
#include <nuttx/fs/fs.h>
#include <nuttx/arch.h>
#include <nuttx/syslog/syslog.h>
#include "fs_internal.h"
#if defined(CONFIG_SYSLOG) && defined(CONFIG_SYSLOG_CHAR)
/****************************************************************************
* Pre-processor Definitions
****************************************************************************/
/* Open the device/file write-only, try to create (file) it if it doesn't
* exist, if the file that already exists, then append the new log data to
* end of the file.
*/
#define SYSLOG_OFLAGS (O_WRONLY | O_CREAT | O_APPEND)
/* An invalid thread ID */
#define NO_HOLDER ((pid_t)-1)
/****************************************************************************
* Private Types
****************************************************************************/
/* This enumeration represents the state of the SYSLOG device interface */
enum syslog_state_e
{
SYSLOG_UNINITIALIZED = 0, /* SYSLOG has not been initialized */
SYSLOG_INITIALIZING, /* SYSLOG is being initialized */
SYSLOG_REOPEN, /* SYSLOG open failed... try again later */
SYSLOG_FAILURE, /* SYSLOG open failed... don't try again */
SYSLOG_OPENED, /* SYSLOG device is open and ready to use */
};
/* This structure contains all SYSLOGing state information */
struct syslog_dev_s
{
uint8_t sl_state; /* See enum syslog_state_e */
sem_t sl_sem; /* Enforces mutually exclusive access */
pid_t sl_holder; /* PID of the thread that holds the semaphore */
struct file sl_file; /* The syslog file structure */
};
/****************************************************************************
* Private Function Prototypes
****************************************************************************/
/****************************************************************************
* Private Data
****************************************************************************/
/* This is the device structure for the console or syslogging function. */
static struct syslog_dev_s g_sysdev;
static const uint8_t g_syscrlf[2] = { '\r', '\n' };
/****************************************************************************
* Private Functions
****************************************************************************/
/****************************************************************************
* Name: syslog_takesem
*
* Description:
* Write to the syslog device
*
****************************************************************************/
static inline int syslog_takesem(void)
{
pid_t me = getpid();
int ret;
/* Does this thread already hold the semaphore? That could happen if
* we wer called recursively, i.e., if the logic kicked off by
* syslog_write() where to generate more debug output. Return an error
* in that case.
*/
if (g_sysdev.sl_holder == me)
{
/* Return an error (instead of deadlocking) */
return -EWOULDBLOCK;
}
/* Either the semaphore is available or is currently held by another
* thread. Wait for it to become available.
*/
ret = sem_wait(&g_sysdev.sl_sem);
if (ret < 0)
{
return -get_errno();
}
/* We hold the semaphore. We can safely mark ourself as the holder
* of the semaphore.
*/
g_sysdev.sl_holder = me;
return OK;
}
/****************************************************************************
* Name: syslog_givesem
*
* Description:
* Write to the syslog device
*
****************************************************************************/
static inline void syslog_givesem(void)
{
#ifdef CONFIG_DEBUG
pid_t me = getpid();
DEBUGASSERT(g_sysdev.sl_holder == me);
#endif
/* Relinquish the semaphore */
g_sysdev.sl_holder = NO_HOLDER;
sem_post(&g_sysdev.sl_sem);
}
/****************************************************************************
* Name: syslog_write
*
* Description:
* Write to the syslog device
*
****************************************************************************/
static inline ssize_t syslog_write(FAR const void *buf, size_t nbytes)
{
FAR struct inode *inode;
/* Let the driver perform the write */
inode = g_sysdev.sl_file.f_inode;
return inode->u.i_ops->write(&g_sysdev.sl_file, buf, nbytes);
}
/****************************************************************************
* Name: syslog_flush
*
* Description:
* Flush any buffer data in the file system to media.
*
****************************************************************************/
#ifndef CONFIG_DISABLE_MOUNTPOINT
static inline void syslog_flush(void)
{
FAR struct inode *inode = g_sysdev.sl_file.f_inode;
/* Is this a mountpoint? Does it support the sync method? */
if (INODE_IS_MOUNTPT(inode) && inode->u.i_mops->sync)
{
/* Yes... synchronize to the stream */
(void)inode->u.i_mops->sync(&g_sysdev.sl_file);
}
}
#endif
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: syslog_initialize
*
* Description:
* Initialize to use the character device (or file) at
* CONFIG_SYSLOG_DEVPATH as the SYSLOG sink.
*
* NOTE that this implementation excludes using a network connection as
* SYSLOG device. That would be a good extension.
*
****************************************************************************/
int syslog_initialize(void)
{
FAR struct inode *inode;
FAR const char *relpath = NULL;
int ret;
/* At this point, the only expected states are SYSLOG_UNINITIALIZED or
* SYSLOG_REOPEN.. Not SYSLOG_INITIALIZING, SYSLOG_FAILURE, SYSLOG_OPENED.
*/
DEBUGASSERT(g_sysdev.sl_state == SYSLOG_UNINITIALIZED ||
g_sysdev.sl_state == SYSLOG_REOPEN);
g_sysdev.sl_state = SYSLOG_INITIALIZING;
/* Try to open the device.
*
* Note that we cannot just call open. The syslog device must work on all
* threads. Open returns a file descriptor that is valid only for the
* task that opened the device (and its pthread children). Instead, we
* essentially re-implement the guts of open() here so that we can get to
* the thread-independent structures of the inode.
*/
/* Get an inode for this file/device */
inode = inode_find(CONFIG_SYSLOG_DEVPATH, &relpath);
if (!inode)
{
/* The inode was not found. In this case, we will attempt to re-open
* the device repeatedly. The assumption is that the device path is
* valid but that the driver has not yet been registered.
*/
g_sysdev.sl_state = SYSLOG_REOPEN;
return -ENOENT;
}
/* Verify that the inode is valid and either a character driver or a
* mountpoint.
*/
#ifndef CONFIG_DISABLE_MOUNTPOINT
if ((!INODE_IS_DRIVER(inode) && !INODE_IS_MOUNTPT(inode)))
#else
if (!INODE_IS_DRIVER(inode))
#endif
{
ret = -ENXIO;
goto errout_with_inode;
}
/* Make sure that the "entity" at this inode supports write access */
if (!inode->u.i_ops || !inode->u.i_ops->write)
{
ret = -EACCES;
goto errout_with_inode;
}
/* Initialize the file structure */
g_sysdev.sl_file.f_oflags = SYSLOG_OFLAGS;
g_sysdev.sl_file.f_pos = 0;
g_sysdev.sl_file.f_inode = inode;
/* Perform the low-level open operation. */
ret = OK;
if (inode->u.i_ops->open)
{
/* Is the inode a mountpoint? */
#ifndef CONFIG_DISABLE_MOUNTPOINT
if (INODE_IS_MOUNTPT(inode))
{
/* Yes. Open the device write-only, try to create it if it
* doesn't exist, if the file that already exists, then append the
* new log data to end of the file.
*/
ret = inode->u.i_mops->open(&g_sysdev.sl_file, relpath,
SYSLOG_OFLAGS, 0666);
}
/* No... then it must be a character driver in the NuttX pseudo-
* file system.
*/
else
#endif
{
ret = inode->u.i_ops->open(&g_sysdev.sl_file);
}
}
/* Was the file/device successfully opened? */
if (ret < 0)
{
ret = -ret;
goto errout_with_inode;
}
/* The SYSLOG device is open and ready for writing. */
sem_init(&g_sysdev.sl_sem, 0, 1);
g_sysdev.sl_holder = NO_HOLDER;
g_sysdev.sl_state = SYSLOG_OPENED;
return OK;
errout_with_inode:
inode_release(inode);
g_sysdev.sl_state = SYSLOG_FAILURE;
return ret;
}
/****************************************************************************
* Name: syslog_putc
*
* Description:
* This is the low-level system logging interface. The debugging/syslogging
* interfaces are syslog() and lowsyslog(). The difference is is that
* the syslog() function writes to fd=1 (stdout) whereas lowsyslog() uses
* a lower level interface that works from interrupt handlers. This
* function is a a low-level interface used to implement lowsyslog().
*
****************************************************************************/
int syslog_putc(int ch)
{
ssize_t nbytes;
uint8_t uch;
int errcode;
int ret;
/* Ignore any output:
*
* (1) Before the SYSLOG device has been initialized. This could happen
* from debug output that occurs early in the boot sequence before
* syslog_initialize() is called (SYSLOG_UNINITIALIZED).
* (2) While the device is being initialized. The case could happen if
* debug output is generated while syslog_initialize() executes
* (SYSLOG_INITIALIZING).
* (3) While we are generating SYSLOG output. The case could happen if
* debug output is generated while syslog_putc() executes
* (This case is actually handled inside of syslog_semtake()).
* (4) Any debug output generated from interrupt handlers. A disadvantage
* of using the generic character device for the SYSLOG is that it
* cannot handle debug output generated from interrupt level handlers.
* (5) Any debug output generated from the IDLE loop. The character
* driver interface is blocking and the IDLE thread is not permitted
* to block.
* (6) If an irrecoverable failure occurred during initialization. In
* this case, we won't ever bother to try again (ever).
*
* NOTE: That the third case is different. It applies only to the thread
* that currently holds the sl_sem sempaphore. Other threads should wait.
* that is why that case is handled in syslog_semtake().
*/
/* Cases (4) and (5) */
if (up_interrupt_context() || getpid() == 0)
{
errcode = ENOSYS;
goto errout_with_errcode;
}
/* We can save checks in the usual case: That after the SYSLOG device
* has been successfully opened.
*/
if (g_sysdev.sl_state != SYSLOG_OPENED)
{
/* Case (1) and (2) */
if (g_sysdev.sl_state == SYSLOG_UNINITIALIZED ||
g_sysdev.sl_state == SYSLOG_INITIALIZING)
{
errcode = EAGAIN; /* Can't access the SYSLOG now... maybe next time? */
goto errout_with_errcode;
}
/* Case (6) */
if (g_sysdev.sl_state == SYSLOG_FAILURE)
{
errcode = ENXIO; /* There is no SYSLOG device */
goto errout_with_errcode;
}
/* syslog_initialize() is called as soon as enough of the operating
* system is in place to support the open operation... but it is
* possible that the SYSLOG device is not yet registered at that time.
* In this case, we know that the system is sufficiently initialized
* to support an attempt to re-open the SYSLOG device.
*
* NOTE that the scheduler is locked. That is because we do not have
* fully initialized semaphore capability until the SYSLOG device is
* successfully initialized
*/
sched_lock();
if (g_sysdev.sl_state == SYSLOG_REOPEN)
{
/* Try again to initialize the device. We may do this repeatedly
* because the log device might be something that was not ready
* the first time that syslog_initializee() was called (such as a
* USB serial device that has not yet been connected or a file in
* an NFS mounted file system that has not yet been mounted).
*/
ret = syslog_initialize();
if (ret < 0)
{
sched_unlock();
errcode = -ret;
goto errout_with_errcode;
}
}
sched_unlock();
DEBUGASSERT(g_sysdev.sl_state == SYSLOG_OPENED);
}
/* Ignore carriage returns */
if (ch == '\r')
{
return ch;
}
/* The syslog device is ready for writing and we have something of
* value to write.
*/
ret = syslog_takesem();
if (ret < 0)
{
/* We probably already hold the semaphore and were probably
* re-entered by the logic kicked off by syslog_write().
* We might also have been interrupted by a signal. Either
* way, we are outta here.
*/
errcode = -ret;
goto errout_with_errcode;
}
/* Pre-pend a newline with a carriage return. */
if (ch == '\n')
{
/* Write the CR-LF sequence */
nbytes = syslog_write(g_syscrlf, 2);
/* Synchronize the file when each CR-LF is encountered (i.e.,
* implements line buffering always).
*/
#ifndef CONFIG_DISABLE_MOUNTPOINT
if (nbytes > 0)
{
syslog_flush();
}
#endif
}
else
{
/* Write the non-newline character (and don't flush) */
uch = (uint8_t)ch;
nbytes = syslog_write(&uch, 1);
}
syslog_givesem();
/* Check if the write was successful. If not, nbytes will be
* a negated errno value.
*/
if (nbytes < 0)
{
errcode = -ret;
goto errout_with_errcode;
}
return ch;
errout_with_errcode:
set_errno(errcode);
return EOF;
}
#endif /* CONFIG_SYSLOG && CONFIG_SYSLOG_CHAR */
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