/****************************************************************************
* fs/mmap/fs_rammmap.c
*
* Copyright (C) 2011 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 <sys/mman.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <debug.h>
#include <nuttx/kmalloc.h>
#include "inode/inode.h"
#include "fs_rammap.h"
#ifdef CONFIG_FS_RAMMAP
/****************************************************************************
* Global Data
****************************************************************************/
/* This is the list of all mapped files */
struct fs_allmaps_s g_rammaps;
/****************************************************************************
* Global Functions
****************************************************************************/
/****************************************************************************
* Name: rammap_initialize
*
* Description:
* Verified that this capability has been initialized.
*
* Input Parameters:
* None
*
* Returned Value:
* None
*
****************************************************************************/
void rammap_initialize(void)
{
if (!g_rammaps.initialized)
{
sem_init(&g_rammaps.exclsem, 0, 1);
g_rammaps.initialized = true;
}
}
/****************************************************************************
* Name: rammmap
*
* Description:
* Support simulation of memory mapped files by copying files into RAM.
*
* Parameters:
* fd file descriptor of the backing file -- required.
* length The length of the mapping. For exception #1 above, this length
* ignored: The entire underlying media is always accessible.
* offset The offset into the file to map
*
* Returned Value:
* On success, rammmap() returns a pointer to the mapped area. On error, the
* value MAP_FAILED is returned, and errno is set appropriately.
*
* EBADF
* 'fd' is not a valid file descriptor.
* EINVAL
* 'length' or 'offset' are invalid
* ENOMEM
* Insufficient memory is available to map the file.
*
****************************************************************************/
FAR void *rammap(int fd, size_t length, off_t offset)
{
FAR struct fs_rammap_s *map;
FAR uint8_t *alloc;
FAR uint8_t *rdbuffer;
ssize_t nread;
off_t fpos;
int err;
int ret;
/* There is a major design flaw that I have not yet thought of fix for:
* The goal is to have a single region of memory that represents a single
* file and can be shared by many threads. That is, given a filename a
* thread should be able to open the file, get a file descriptor, and
* call mmap() to get a memory region. Different file descriptors opened
* with the same file path should get the same memory region when mapped.
*
* The design flaw is that I don't have sufficient knowledge to know that
* these different file descriptors map to the same file. So, for the time
* being, a new memory region is created each time that rammap() is called.
* Not very useful!
*/
/* Allocate a region of memory of the specified size */
alloc = (FAR uint8_t *)kumm_malloc(sizeof(struct fs_rammap_s) + length);
if (!alloc)
{
fdbg("Region allocation failed, length: %d\n", (int)length);
err = ENOMEM;
goto errout;
}
/* Initialize the region */
map = (FAR struct fs_rammap_s *)alloc;
memset(map, 0, sizeof(struct fs_rammap_s));
map->addr = alloc + sizeof(struct fs_rammap_s);
map->length = length;
map->offset = offset;
/* Seek to the specified file offset */
fpos = lseek(fd, offset, SEEK_SET);
if (fpos == (off_t)-1)
{
/* Seek failed... errno has already been set, but EINVAL is probably
* the correct response.
*/
fdbg("Seek to position %d failed\n", (int)offset);
err = EINVAL;
goto errout_with_region;
}
/* Read the file data into the memory region */
rdbuffer = map->addr;
while (length > 0)
{
nread = read(fd, rdbuffer, length);
if (nread < 0)
{
/* Handle the special case where the read was interrupted by a
* signal.
*/
err = get_errno();
if (err != EINTR)
{
/* All other read errors are bad. errno is already set.
* (but maybe should be forced to EINVAL?). NOTE that if
* FS DEBUG is enabled, then the following fdbg() macro will
* destroy the errno value.
*/
fdbg("Read failed: offset=%d errno=%d\n", (int)offset, err);
#ifdef CONFIG_DEBUG_FS
goto errout_with_region;
#else
goto errout_with_errno;
#endif
}
}
/* Check for end of file. */
if (nread == 0)
{
break;
}
/* Increment number of bytes read */
rdbuffer += nread;
length -= nread;
}
/* Zero any memory beyond the amount read from the file */
memset(rdbuffer, 0, length);
/* Add the buffer to the list of regions */
rammap_initialize();
ret = sem_wait(&g_rammaps.exclsem);
if (ret < 0)
{
goto errout_with_errno;
}
map->flink = g_rammaps.head;
g_rammaps.head = map;
sem_post(&g_rammaps.exclsem);
return map->addr;
errout_with_region:
kumm_free(alloc);
errout:
set_errno(err);
return MAP_FAILED;
errout_with_errno:
kumm_free(alloc);
return MAP_FAILED;
}
#endif /* CONFIG_FS_RAMMAP */
