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