/****************************************************************************
* fs/fs_mmap.c
*
* Copyright (C) 2008 Gregory Nutt. All rights reserved.
* Author: Gregory Nutt <spudmonkey@racsa.co.cr>
*
* 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 <sys/ioctl.h>
#include <errno.h>
#include <debug.h>
#include "fs_internal.h"
/****************************************************************************
* Global Functions
****************************************************************************/
/****************************************************************************
* Name: mmap
*
* Description:
* NuttX operates in a flat open address space. Therefore, it generally
* does not require mmap() functionality. There is one one exception:
* mmap() is the API that is used to support direct access to random
* access media under the following very restrictive conditions:
*
* 1. 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.
* 2. The underly 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.
*
* Parameters:
* start A hint at where to map the memory -- ignored. The address
* of the underlying media is fixed and cannot be re-mapped withou
* MMU support.
* length The length of the mapping -- ignored. The entire underlying
* media is always accessible.
* prot See the PROT_* definitions in sys/mman.h.
* PROT_NONE - Will cause an error
* PROT_READ - PROT_WRITE and PROT_EXEC also assumed
* PROT_WRITE - PROT_READ and PROT_EXEC also assumed
* PROT_EXEC - PROT_READ and PROT_WRITE also assumed
* flags See the MAP_* definitions in sys/mman.h.
* MAP_SHARED - Required
* MAP_PRIVATE - Will cause an error
* MAP_FIXED - Will cause an error
* MAP_FILE - Ignored
* MAP_ANONYMOUS - Will cause an error
* MAP_ANON - Will cause an error
* MAP_GROWSDOWN - Ignored
* MAP_DENYWRITE - Will cause an error
* MAP_EXECUTABLE - Ignored
* MAP_LOCKED - Ignored
* MAP_NORESERVE - Ignored
* MAP_POPULATE - Ignored
* MAP_NONBLOCK - Ignored
* fd file descriptor of the backing file -- required.
* offset The offset into the file to map
*
* Return:
* On success, mmap() returns a pointer to the mapped area.
* On error, the value MAP_FAILED is returned, and errno is set appropriately.
*
* ENOSYS
* Returned if any of the unsupported mmap() features are attempted
* EBADF
* 'fd' is not a valid file descriptor.
* EINVAL
* Length is 0. flags contained neither MAP_PRIVATE or MAP_SHARED, or
* contained both of these values.
* ENODEV
* The underlying filesystem of the specified file does not support
* memory mapping.
*
****************************************************************************/
FAR void *mmap(FAR void *start, size_t length, int prot, int flags,
int fd, off_t offset)
{
FAR void *addr;
int ret;
/* Since only a tiny subset of mmap() functionality, we have to verify many
* things.
*/
#ifdef CONFIG_DEBUG
if (prot == PROT_NONE ||
(flags & (MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS|MAP_DENYWRITE)) != 0)
{
fdbg("Unsupported options, prot=%x flags=%04x\n", prot, flags);
ret = ENOSYS;
goto errout_with_ret;
}
if (length == 0 ||
(flags & MAP_SHARED) == 0)
{
fdbg("Invalid options, lengt=%d flags=%04x\n", length, flags);
ret = EINVAL;
goto errout_with_ret;
}
#endif
/* Okay now we can assume a shared mapping from a file. This is the
* only option supported
*
* Perform the ioctl to get the base address of the file in 'mapped'
* in memory.
*/
ret = ioctl(fd, FIOC_MMAP, (unsigned long)&addr);
if (ret < 0)
{
fdbg("ioctl(FIOC_MMAP) failed: %d\n", errno);
goto errout;
}
/* Return the offset address */
return (void*)(((ubyte*)addr) + offset);
#ifdef CONFIG_DEBUG
errout_with_ret:
errno = ret;
#endif
errout:
return MAP_FAILED;
}
