/****************************************************************************
* fs/mmap/fs_munmap.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 <stdint.h>
#include <errno.h>
#include <assert.h>
#include <debug.h>
#include <nuttx/kmalloc.h>
#include "fs_internal.h"
#include "fs_rammap.h"
#ifdef CONFIG_FS_RAMMAP
/****************************************************************************
* Global Functions
****************************************************************************/
/****************************************************************************
* Name: munmap
*
* Description:
*
* munmap() system call deletes mappings for the specified address range.
* All memory starting with 'start' and continuing for a length of 'length'
* bytes are removed.
*
* NuttX operates in a flat open address space. Therefore, it generally
* does not require mmap() and, hence, munmap functionality. There are
* two exceptions where mmap() is available:
*
* 1. mmap() is the API that is used to support direct access to random
* access media under the following very restrictive conditions:
*
* a. The filesystem supports the FIOC_MMAP ioctl command. Any file
* system that maps files contiguously on the media should support
* this ioctl. (vs. file system that scatter files over the media
* in non-contiguous sectors). As of this writing, ROMFS is the
* only file system that meets this requirement.
* b. The underlying block driver supports the BIOC_XIPBASE ioctl
* command that maps the underlying media to a randomly accessible
* address. At present, only the RAM/ROM disk driver does this.
*
* munmap() is still not required in this first case. In this first
* The mapped address is a static address in the MCUs address space
* does not need to be munmapped. Support for munmap() in this case
* provided by the simple definition in sys/mman.h:
*
* #define munmap(start, length)
*
* 2. If CONFIG_FS_RAMMAP is defined in the configuration, then mmap() will
* support simulation of memory mapped files by copying files whole
* into RAM. munmap() is required in this case to free the allocated
* memory holding the shared copy of the file.
*
* Parameters:
* start The start address of the mapping to delete. For this
* simplified munmap() implementation, the *must* be the start
* address of the memory region (the same address returned by
* mmap()).
* length The length region to be umapped.
*
* Returned Value:
* On success, munmap() returns 0, on failure -1, and errno is set
* (probably to EINVAL).
*
****************************************************************************/
int munmap(FAR void *start, size_t length)
{
FAR struct fs_rammap_s *prev;
FAR struct fs_rammap_s *curr;
FAR void *newaddr;
unsigned int offset;
int ret;
int err;
/* Find a region containing this start and length in the list of regions */
rammap_initialize();
ret = sem_wait(&g_rammaps.exclsem);
if (ret < 0)
{
return ERROR;
}
/* Seach the list of regions */
for (prev = NULL, curr = g_rammaps.head; curr; prev = curr, curr = curr->flink)
{
/* Does this region include any part of the specified range? */
if ((uintptr_t)start < (uintptr_t)curr->addr + curr->length &&
(uintptr_t)start + length >= (uintptr_t)curr->addr)
{
break;
}
}
/* Did we find the region */
if (!curr)
{
fdbg("Region not found\n");
err = EINVAL;
goto errout_with_semaphore;
}
/* Get the offset from the beginning of the region and the actual number
* of bytes to "unmap". All mappings must extend to the end of the region.
* There is no support for free a block of memory but leaving a block of
* memory at the end. This is a consequence of using kurealloc() to
* simulate the unmapping.
*/
offset = start - curr->addr;
if (offset + length < curr->length)
{
fdbg("Cannot umap without unmapping to the end\n");
err = ENOSYS;
goto errout_with_semaphore;
}
/* Okay.. the region is beging umapped to the end. Make sure the length
* indicates that.
*/
length = curr->length - offset;
/* Are we unmapping the entire region (offset == 0)? */
if (length >= curr->length)
{
/* Yes.. remove the mapping from the list */
if (prev)
{
prev->flink = curr->flink;
}
else
{
g_rammaps.head = curr->flink;
}
/* Then free the region */
kufree(curr);
}
/* No.. We have been asked to "unmap' only a portion of the memory
* (offset > 0).
*/
else
{
newaddr = kurealloc(curr->addr, sizeof(struct fs_rammap_s) + length);
DEBUGASSERT(newaddr == (FAR void*)(curr->addr));
curr->length = length;
}
sem_post(&g_rammaps.exclsem);
return OK;
errout_with_semaphore:
sem_post(&g_rammaps.exclsem);
errno = err;
return ERROR;
}
#endif /* CONFIG_FS_RAMMAP */
