209 lines
7.2 KiB
C
209 lines
7.2 KiB
C
/****************************************************************************
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* fs/mmap/fs_mmap.c
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*
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership. The
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* ASF licenses this file to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance with the
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* License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations
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* under the License.
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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 <sys/ioctl.h>
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#include <stdint.h>
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#include <errno.h>
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#include <debug.h>
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#include <nuttx/kmalloc.h>
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#include "inode/inode.h"
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#include "fs_rammap.h"
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: mmap
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*
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* Description:
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* NuttX operates in a flat open address space. Therefore, it generally
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* does not require mmap() functionality. There are two exceptions:
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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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* 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.
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*
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* Input Parameters:
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* start A hint at where to map the memory -- ignored. The address
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* of the underlying media is fixed and cannot be re-mapped without
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* MMU support.
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* length The length of the mapping. For exception #1 above, this length
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* ignored: The entire underlying media is always accessible.
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* prot See the PROT_* definitions in sys/mman.h.
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* PROT_NONE - Will cause an error
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* PROT_READ - PROT_WRITE and PROT_EXEC also assumed
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* PROT_WRITE - PROT_READ and PROT_EXEC also assumed
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* PROT_EXEC - PROT_READ and PROT_WRITE also assumed
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* flags See the MAP_* definitions in sys/mman.h.
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* MAP_SHARED - MAP_PRIVATE or MAP_SHARED required
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* MAP_PRIVATE - MAP_PRIVATE or MAP_SHARED required
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* MAP_FIXED - Will cause an error
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* MAP_FILE - Ignored
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* MAP_ANONYMOUS - Optional
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* MAP_ANON - Will cause an error
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* MAP_GROWSDOWN - Ignored
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* MAP_DENYWRITE - Will cause an error
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* MAP_EXECUTABLE - Ignored
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* MAP_LOCKED - Ignored
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* MAP_NORESERVE - Ignored
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* MAP_POPULATE - Ignored
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* MAP_NONBLOCK - Ignored
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* fd file descriptor of the backing file -- required.
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* offset The offset into the file to map
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*
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* Returned Value:
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* On success, mmap() returns a pointer to the mapped area. On error, the
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* value MAP_FAILED is returned, and errno is set appropriately.
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*
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* ENOSYS
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* Returned if any of the unsupported mmap() features are attempted
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* EBADF
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* 'fd' is not a valid file descriptor.
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* EINVAL
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* Length is 0. flags contained neither MAP_PRIVATE or MAP_SHARED, or
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* contained both of these values.
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* ENODEV
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* The underlying filesystem of the specified file does not support
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* memory mapping.
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*
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****************************************************************************/
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FAR void *mmap(FAR void *start, size_t length, int prot, int flags,
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int fd, off_t offset)
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{
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FAR void *addr;
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int ret = -1;
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/* Since only a tiny subset of mmap() functionality, we have to verify many
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* things.
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*/
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#ifdef CONFIG_DEBUG_FEATURES
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/* Fixed mappings and protections are not currently supported. These
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* options could be supported in the KERNEL build with an MMU, but that
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* logic is not in place.
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*/
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if (prot == PROT_NONE ||
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(flags & (MAP_FIXED | MAP_DENYWRITE)) != 0)
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{
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ferr("ERROR: Unsupported options, prot=%x flags=%04x\n", prot, flags);
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ret = -ENOSYS;
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goto errout;
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}
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/* A length of 0 is invalid. */
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if (length == 0)
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{
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ferr("ERROR: Invalid length, length=%zu\n", length);
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ret = -EINVAL;
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goto errout;
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}
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#endif
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/* Check if we are just be asked to allocate memory, i.e., MAP_ANONYMOUS
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* set meaning that the memory is not backed up from a file. The file
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* descriptor should be -1 (or refer to opened /dev/zero) in this case.
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* The file descriptor is ignored in either case.
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*/
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if ((flags & MAP_ANONYMOUS) != 0)
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{
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FAR void *alloc;
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/* REVISIT: Should reside outside of the heap. That is really the
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* only purpose of MAP_ANONYMOUS: To get non-heap memory. In KERNEL
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* build, this could be accomplished using pgalloc(), provided that
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* you had logic in place to assign a virtual address to the mapping.
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*/
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alloc = kumm_zalloc(length);
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if (alloc == NULL)
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{
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ferr("ERROR: kumm_alloc() failed: %d\n", ret);
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ret = -ENOMEM;
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goto errout;
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}
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return alloc;
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}
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/* Perform the ioctl to get the base address of the file in 'mapped'
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* in memory. (casting to uintptr_t first eliminates complaints on some
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* architectures where the sizeof long is different from the size of
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* a pointer).
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*/
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if ((flags & MAP_PRIVATE) == 0)
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{
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ret = nx_ioctl(fd, FIOC_MMAP, (unsigned long)((uintptr_t)&addr));
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}
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if (ret < 0)
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{
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/* Not directly mappable, probably because the underlying media does
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* not support random access.
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*/
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#ifdef CONFIG_FS_RAMMAP
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/* Allocate memory and copy the file into memory. We would, of course,
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* do much better in the KERNEL build using the MMU.
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*/
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return rammap(fd, length, offset);
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#else
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ferr("ERROR: nx_ioctl(FIOC_MMAP) failed: %d\n", ret);
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goto errout;
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#endif
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}
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/* Return the offset address */
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return (FAR void *)(((FAR uint8_t *)addr) + offset);
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errout:
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set_errno(-ret);
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return MAP_FAILED;
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}
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