/**************************************************************************** * 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 #include #include #include #include #include #include #include #include #include "inode/inode.h" #include "fs_rammap.h" /**************************************************************************** * Private Functions ****************************************************************************/ /**************************************************************************** * Name: file_mmap_ ****************************************************************************/ static int file_mmap_(FAR struct file *filep, FAR void *start, size_t length, int prot, int flags, off_t offset, bool kernel, FAR void **mapped) { FAR void *addr; 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 ((flags & (MAP_FIXED | MAP_DENYWRITE)) != 0) { ferr("ERROR: Unsupported options, prot=%x flags=%04x\n", prot, flags); return -ENOSYS; } #ifndef CONFIG_FS_RAMMAP if ((flags & MAP_PRIVATE) != 0) { ferr("ERROR: MAP_PRIVATE is not supported without file mapping" "emulation\n"); return -ENOSYS; } #endif /* CONFIG_FS_RAMMAP */ /* A length of 0 is invalid. */ if (length == 0) { ferr("ERROR: Invalid length, length=%zu\n", length); return -EINVAL; } #endif /* CONFIG_DEBUG_FEATURES */ if ((filep->f_oflags & O_WROK) == 0 && prot == PROT_WRITE && (flags & MAP_SHARED) != 0) { ferr("ERROR: Unsupported options for read-only file descriptor," "prot=%x flags=%04x\n", prot, flags); return -EACCES; } if ((filep->f_oflags & O_RDOK) == 0) { ferr("ERROR: File descriptor does not have read permission\n"); return -EACCES; } /* 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) { /* 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. */ *mapped = kernel ? kmm_zalloc(length) : kumm_zalloc(length); if (*mapped == NULL) { ferr("ERROR: kumm_alloc() failed: %d\n", ret); return -ENOMEM; } return OK; } 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(filep, length, offset, kernel, mapped); #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 = file_ioctl(filep, 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(filep, length, offset, kernel, mapped); #else ferr("ERROR: file_ioctl(FIOC_MMAP) failed: %d\n", ret); return ret; #endif } /* Return the offset address */ *mapped = (FAR void *)(((FAR uint8_t *)addr) + offset); return OK; } /**************************************************************************** * Public Functions ****************************************************************************/ /**************************************************************************** * Name: file_mmap * * Description: * Equivalent to the standard mmap() function except that is accepts * a struct file instance instead of a file descriptor and it does not set * the errno variable. * ****************************************************************************/ int file_mmap(FAR struct file *filep, FAR void *start, size_t length, int prot, int flags, off_t offset, FAR void **mapped) { return file_mmap_(filep, start, length, prot, flags, offset, true, mapped); } /**************************************************************************** * 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 struct file *filep; FAR void *mapped; int ret; if (fs_getfilep(fd, &filep) < 0) { ferr("ERROR: Invalid file descriptor, fd=%d\n", fd); ret = -EBADF; goto errout; } ret = file_mmap_(filep, start, length, prot, flags, offset, false, &mapped); if (ret < 0) { goto errout; } return mapped; errout: set_errno(-ret); return MAP_FAILED; }