/**************************************************************************** * fs/mmap/fs_mmap.c * * Copyright (C) 2008-2009, 2011, 2019 Gregory Nutt. All rights reserved. * Author: Gregory Nutt * * 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 #include #include #include #include #include #include #include #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. * * 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 = -1; /* 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); errcode = ENOSYS; goto errout; } /* A length of 0 is invalid. */ if (length == 0) { ferr("ERROR: Invalid length, length=%d\n", length); 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; } /* 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). */ if ((flags & MAP_PRIVATE) == 0) { 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()); errcode = ENOSYS; goto errout; #endif } /* Return the offset address */ return (FAR void *)(((FAR uint8_t *)addr) + offset); errout: set_errno(errcode); return MAP_FAILED; }