forked from Archive/PX4-Autopilot
246 lines
7.2 KiB
C
246 lines
7.2 KiB
C
/****************************************************************************
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* fs/mmap/fs_rammmap.c
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*
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* Copyright (C) 2011 Gregory Nutt. All rights reserved.
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* Author: Gregory Nutt <gnutt@nuttx.org>
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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* 3. Neither the name NuttX nor the names of its contributors may be
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* used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*
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****************************************************************************/
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/****************************************************************************
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* Included Files
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****************************************************************************/
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#include <nuttx/config.h>
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#include <sys/types.h>
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#include <sys/mman.h>
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#include <string.h>
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#include <unistd.h>
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#include <errno.h>
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#include <debug.h>
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#include <nuttx/kmalloc.h>
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#include "fs_internal.h"
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#include "fs_rammap.h"
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#ifdef CONFIG_FS_RAMMAP
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/****************************************************************************
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* Global Data
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****************************************************************************/
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/* This is the list of all mapped files */
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struct fs_allmaps_s g_rammaps;
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/****************************************************************************
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* Global Functions
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****************************************************************************/
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/****************************************************************************
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* Name: rammap_initialize
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*
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* Description:
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* Verified that this capability has been initialized.
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*
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* Input Parameters:
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* None
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*
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* Returned Value:
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* None
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*
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****************************************************************************/
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void rammap_initialize(void)
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{
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if (!g_rammaps.initialized)
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{
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sem_init(&g_rammaps.exclsem, 0, 1);
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g_rammaps.initialized = true;
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}
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}
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/****************************************************************************
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* Name: rammmap
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*
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* Description:
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* Support simulation of memory mapped files by copying files into RAM.
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*
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* Parameters:
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* fd file descriptor of the backing file -- required.
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* length The length of the mapping. For exception #1 above, this length
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* ignored: The entire underlying media is always accessible.
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* offset The offset into the file to map
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*
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* Returned Value:
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* On success, rammmap() returns a pointer to the mapped area. On error, the
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* value MAP_FAILED is returned, and errno is set appropriately.
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*
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* EBADF
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* 'fd' is not a valid file descriptor.
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* EINVAL
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* 'length' or 'offset' are invalid
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* ENOMEM
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* Insufficient memory is available to map the file.
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*
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****************************************************************************/
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FAR void *rammap(int fd, size_t length, off_t offset)
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{
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FAR struct fs_rammap_s *map;
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FAR uint8_t *alloc;
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FAR uint8_t *rdbuffer;
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ssize_t nread;
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off_t fpos;
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int err;
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int ret;
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/* There is a major design flaw that I have not yet thought of fix for:
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* The goal is to have a single region of memory that represents a single
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* file and can be shared by many threads. That is, given a filename a
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* thread should be able to open the file, get a file descriptor, and
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* call mmap() to get a memory region. Different file descriptors opened
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* with the same file path should get the same memory region when mapped.
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*
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* The design flaw is that I don't have sufficient knowledge to know that
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* these different file descriptors map to the same file. So, for the time
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* being, a new memory region is created each time that rammap() is called.
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* Not very useful!
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*/
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/* Allocate a region of memory of the specified size */
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alloc = (FAR uint8_t *)kmalloc(sizeof(struct fs_rammap_s) + length);
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if (!alloc)
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{
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fdbg("Region allocation failed, length: %d\n", (int)length);
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err = ENOMEM;
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goto errout;
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}
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/* Initialize the region */
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map = (FAR struct fs_rammap_s *)alloc;
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memset(map, 0, sizeof(struct fs_rammap_s));
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map->addr = alloc + sizeof(struct fs_rammap_s);
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map->length = length;
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map->offset = offset;
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/* Seek to the specified file offset */
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fpos = lseek(fd, offset, SEEK_SET);
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if (fpos == (off_t)-1)
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{
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/* Seek failed... errno has already been set, but EINVAL is probably
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* the correct response.
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*/
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fdbg("Seek to position %d failed\n", (int)offset);
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err = EINVAL;
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goto errout_with_region;
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}
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/* Read the file data into the memory region */
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rdbuffer = map->addr;
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while (length > 0)
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{
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nread = read(fd, rdbuffer, length);
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if (nread < 0)
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{
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/* Handle the special case where the read was interrupted by a
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* signal.
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*/
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err = get_errno();
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if (err != EINTR)
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{
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/* All other read errors are bad. errno is already set.
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* (but maybe should be forced to EINVAL?). NOTE that if
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* FS DEBUG is enabled, then the following fdbg() macro will
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* destroy the errno value.
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*/
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fdbg("Read failed: offset=%d errno=%d\n", (int)offset, err);
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#ifdef CONFIG_DEBUG_FS
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goto errout_with_region;
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#else
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goto errout_with_errno;
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#endif
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}
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}
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/* Check for end of file. */
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if (nread == 0)
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{
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break;
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}
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/* Increment number of bytes read */
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rdbuffer += nread;
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length -= nread;
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}
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/* Zero any memory beyond the amount read from the file */
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memset(rdbuffer, 0, length);
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/* Add the buffer to the list of regions */
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rammap_initialize();
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ret = sem_wait(&g_rammaps.exclsem);
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if (ret < 0)
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{
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goto errout_with_errno;
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}
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map->flink = g_rammaps.head;
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g_rammaps.head = map;
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sem_post(&g_rammaps.exclsem);
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return map->addr;
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errout_with_region:
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kfree(alloc);
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errout:
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set_errno(err);
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return MAP_FAILED;
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errout_with_errno:
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kfree(alloc);
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return MAP_FAILED;
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}
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#endif /* CONFIG_FS_RAMMAP */
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