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incubator-nuttx/fs/mmap/fs_mmap.c

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/****************************************************************************
* fs/mmap/fs_mmap.c
*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership. The
* ASF licenses this file to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance with the
* License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations
* under the License.
*
****************************************************************************/
/****************************************************************************
* 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 <fcntl.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 - MAP_PRIVATE or MAP_SHARED required
* MAP_PRIVATE - MAP_PRIVATE or MAP_SHARED required
* 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.
*
* EACCES
* The fd argument is not open for read, regardless of the
* protection specified, or fd is not open for write and PROT_WRITE
* was specified for a MAP_SHARED type mapping.
* 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.
* ENOMEM
* Insufficient memory is available to map the file.
*
****************************************************************************/
FAR void *mmap(FAR void *start, size_t length, int prot, int flags,
int fd, off_t offset)
{
FAR void *addr;
FAR struct file *filep;
int ret;
/* Since only a tiny subset of mmap() functionality, we have to verify many
* things.
*/
#ifdef CONFIG_DEBUG_FEATURES
/* Fixed 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_FIXED | MAP_DENYWRITE)) != 0)
{
ferr("ERROR: Unsupported options, prot=%x flags=%04x\n", prot, flags);
ret = -ENOSYS;
goto errout;
}
#ifndef CONFIG_FS_RAMMAP
if ((flags & MAP_PRIVATE) != 0)
{
ferr("ERROR: MAP_PRIVATE is not supported without file mapping"
"emulation\n");
ret = -ENOSYS;
goto errout;
}
#endif /* CONFIG_FS_RAMMAP */
/* A length of 0 is invalid. */
if (length == 0)
{
ferr("ERROR: Invalid length, length=%zu\n", length);
ret = -EINVAL;
goto errout;
}
#endif /* CONFIG_DEBUG_FEATURES */
if (fs_getfilep(fd, &filep) < 0)
{
ferr("ERROR: Invalid file descriptor, fd=%d\n", fd);
ret = -EBADF;
goto errout;
}
if ((filep->f_oflags & O_WROK) == 0 && prot == PROT_WRITE &&
(flags & MAP_SHARED) != 0)
{
ferr("ERROR: Unsupported options for read-only file descriptor,"
"fd=%d prot=%x flags=%04x\n", fd, prot, flags);
ret = -EACCES;
goto errout;
}
if ((filep->f_oflags & O_RDOK) == 0)
{
ferr("ERROR: File descriptor does not have read permission,"
"fd=%d\n", fd);
ret = -EACCES;
goto errout;
}
/* 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);
ret = -ENOMEM;
goto errout;
}
return alloc;
}
if ((flags & MAP_PRIVATE) != 0)
{
#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);
#endif
}
/* 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 = nx_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
ferr("ERROR: nx_ioctl(FIOC_MMAP) failed: %d\n", ret);
goto errout;
#endif
}
/* Return the offset address */
return (FAR void *)(((FAR uint8_t *)addr) + offset);
errout:
set_errno(-ret);
return MAP_FAILED;
}
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