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incubator-nuttx/fs/mmap/fs_mmap.c

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/****************************************************************************
* fs/mmap/fs_mmap.c
*
* Copyright (C) 2008-2009, 2011, 2019 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 <sys/ioctl.h>
#include <stdint.h>
#include <errno.h>
#include <debug.h>
#include <nuttx/kmalloc.h>
#include "inode/inode.h"
#include "fs_rammap.h"
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: mmap
*
* Description:
* NuttX operates in a flat open address space. Therefore, it generally
* does not require mmap() functionality. There are two exceptions:
*
* 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.
*
* 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.
*
* Input Parameters:
* start A hint at where to map the memory -- ignored. The address
* of the underlying media is fixed and cannot be re-mapped without
* MMU support.
* length The length of the mapping. For exception #1 above, this length
* 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 - Optional
* 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
*
* Returned Value:
* 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 errcode;
int ret;
/* Since only a tiny subset of mmap() functionality, we have to verify many
* things.
*/
#ifdef CONFIG_DEBUG_FEATURES
/* Private mappings and protections are not currently supported. These
* options could be supported in the KERNEL build with an MMU, but that
* logic is not in place.
*/
if (prot == PROT_NONE ||
(flags & (MAP_PRIVATE | MAP_FIXED | MAP_DENYWRITE)) != 0)
{
ferr("ERROR: Unsupported options, prot=%x flags=%04x\n", prot, flags);
errcode = ENOSYS;
goto errout;
}
/* A length of 0 is invalid. Currently only shared mappings are supported.
* Non-shared could be implemented in the KERNEL build with an MMU.
*/
if (length == 0 || (flags & MAP_SHARED) == 0)
{
ferr("ERROR: Invalid options, length=%d flags=%04x\n", length, flags);
errcode = EINVAL;
goto errout;
}
#endif
/* Check if we are just be asked to allocate memory, i.e., MAP_ANONYMOUS
* set meaning that the memory is not backed up from a file. The file
* descriptor should be -1 (or refer to opened /dev/zero) in this case.
* The file descriptor is ignored in either case.
*/
if ((flags & MAP_ANONYMOUS) != 0)
{
FAR void *alloc;
/* REVISIT: Should reside outside of the heap. That is really the
* only purpose of MAP_ANONYMOUS: To get non-heap memory. In KERNEL
* build, this could be accomplished using pgalloc(), provided that
* you had logic in place to assign a virtual address to the mapping.
*/
alloc = kumm_zalloc(length);
if (alloc == NULL)
{
ferr("ERROR: kumm_alloc() failed: %d\n", ret);
errcode = ENOMEM;
goto errout;
}
return alloc;
}
/* Okay now we can assume a shared mapping from a file. This is the
* only other option supported
*
* Perform the ioctl to get the base address of the file in 'mapped'
* in memory. (casting to uintptr_t first eliminates complaints on some
* architectures where the sizeof long is different from the size of
* a pointer).
*/
ret = ioctl(fd, FIOC_MMAP, (unsigned long)((uintptr_t)&addr));
if (ret < 0)
{
/* Not directly mappable, probably because the underlying media does
* not support random access.
*/
#ifdef CONFIG_FS_RAMMAP
/* Allocate memory and copy the file into memory. We would, of course,
* do much better in the KERNEL build using the MMU.
*/
return rammap(fd, length, offset);
#else
/* Error out. The errno value was already set by ioctl() */
ferr("ERROR: ioctl(FIOC_MMAP) failed: %d\n", get_errno());
return MAP_FAILED;
#endif
}
/* Return the offset address */
return (FAR void *)(((FAR uint8_t *)addr) + offset);
errout:
set_errno(errcode);
return MAP_FAILED;
}
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