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1// SPDX-License-Identifier: GPL-2.0-or-later2/* NOMMU mmap support for RomFS on MTD devices3 *4 * Copyright © 2007 Red Hat, Inc. All Rights Reserved.5 * Written by David Howells (dhowells@redhat.com)6 */7 8#include <linux/mm.h>9#include <linux/mtd/super.h>10#include "internal.h"11 12/*13 * try to determine where a shared mapping can be made14 * - only supported for NOMMU at the moment (MMU can't doesn't copy private15 * mappings)16 * - attempts to map through to the underlying MTD device17 */18static unsigned long romfs_get_unmapped_area(struct file *file,19 unsigned long addr,20 unsigned long len,21 unsigned long pgoff,22 unsigned long flags)23{24 struct inode *inode = file->f_mapping->host;25 struct mtd_info *mtd = inode->i_sb->s_mtd;26 unsigned long isize, offset, maxpages, lpages;27 int ret;28 29 if (!mtd)30 return (unsigned long) -ENOSYS;31 32 /* the mapping mustn't extend beyond the EOF */33 lpages = (len + PAGE_SIZE - 1) >> PAGE_SHIFT;34 isize = i_size_read(inode);35 offset = pgoff << PAGE_SHIFT;36 37 maxpages = (isize + PAGE_SIZE - 1) >> PAGE_SHIFT;38 if ((pgoff >= maxpages) || (maxpages - pgoff < lpages))39 return (unsigned long) -EINVAL;40 41 if (addr != 0)42 return (unsigned long) -EINVAL;43 44 if (len > mtd->size || pgoff >= (mtd->size >> PAGE_SHIFT))45 return (unsigned long) -EINVAL;46 47 offset += ROMFS_I(inode)->i_dataoffset;48 if (offset >= mtd->size)49 return (unsigned long) -EINVAL;50 /* the mapping mustn't extend beyond the EOF */51 if ((offset + len) > mtd->size)52 len = mtd->size - offset;53 54 ret = mtd_get_unmapped_area(mtd, len, offset, flags);55 if (ret == -EOPNOTSUPP)56 ret = -ENOSYS;57 return (unsigned long) ret;58}59 60/*61 * permit a R/O mapping to be made directly through onto an MTD device if62 * possible63 */64static int romfs_mmap(struct file *file, struct vm_area_struct *vma)65{66 return is_nommu_shared_mapping(vma->vm_flags) ? 0 : -ENOSYS;67}68 69static unsigned romfs_mmap_capabilities(struct file *file)70{71 struct mtd_info *mtd = file_inode(file)->i_sb->s_mtd;72 73 if (!mtd)74 return NOMMU_MAP_COPY;75 return mtd_mmap_capabilities(mtd);76}77 78const struct file_operations romfs_ro_fops = {79 .llseek = generic_file_llseek,80 .read_iter = generic_file_read_iter,81 .splice_read = filemap_splice_read,82 .mmap = romfs_mmap,83 .get_unmapped_area = romfs_get_unmapped_area,84 .mmap_capabilities = romfs_mmap_capabilities,85};86