fs/romfs/mmap-nommu.c

0001 // SPDX-License-Identifier: GPL-2.0-or-later
0002 /* NOMMU mmap support for RomFS on MTD devices
0003  *
0004  * Copyright © 2007 Red Hat, Inc. All Rights Reserved.
0005  * Written by David Howells (dhowells@redhat.com)
0006  */
0007
0008 #include <linux/mm.h>
0009 #include <linux/mtd/super.h>
0010 #include "internal.h"
0011
0012 /*
0013  * try to determine where a shared mapping can be made
0014  * - only supported for NOMMU at the moment (MMU can't doesn't copy private
0015  *   mappings)
0016  * - attempts to map through to the underlying MTD device
0017  */
0018 static unsigned long romfs_get_unmapped_area(struct file *file,
0019                          unsigned long addr,
0020                          unsigned long len,
0021                          unsigned long pgoff,
0022                          unsigned long flags)
0023 {
0024     struct inode *inode = file->f_mapping->host;
0025     struct mtd_info *mtd = inode->i_sb->s_mtd;
0026     unsigned long isize, offset, maxpages, lpages;
0027     int ret;
0028
0029     if (!mtd)
0030         return (unsigned long) -ENOSYS;
0031
0032     /* the mapping mustn't extend beyond the EOF */
0033     lpages = (len + PAGE_SIZE - 1) >> PAGE_SHIFT;
0034     isize = i_size_read(inode);
0035     offset = pgoff << PAGE_SHIFT;
0036
0037     maxpages = (isize + PAGE_SIZE - 1) >> PAGE_SHIFT;
0038     if ((pgoff >= maxpages) || (maxpages - pgoff < lpages))
0039         return (unsigned long) -EINVAL;
0040
0041     if (addr != 0)
0042         return (unsigned long) -EINVAL;
0043
0044     if (len > mtd->size || pgoff >= (mtd->size >> PAGE_SHIFT))
0045         return (unsigned long) -EINVAL;
0046
0047     offset += ROMFS_I(inode)->i_dataoffset;
0048     if (offset >= mtd->size)
0049         return (unsigned long) -EINVAL;
0050     /* the mapping mustn't extend beyond the EOF */
0051     if ((offset + len) > mtd->size)
0052         len = mtd->size - offset;
0053
0054     ret = mtd_get_unmapped_area(mtd, len, offset, flags);
0055     if (ret == -EOPNOTSUPP)
0056         ret = -ENOSYS;
0057     return (unsigned long) ret;
0058 }
0059
0060 /*
0061  * permit a R/O mapping to be made directly through onto an MTD device if
0062  * possible
0063  */
0064 static int romfs_mmap(struct file *file, struct vm_area_struct *vma)
0065 {
0066     return vma->vm_flags & (VM_SHARED | VM_MAYSHARE) ? 0 : -ENOSYS;
0067 }
0068
0069 static unsigned romfs_mmap_capabilities(struct file *file)
0070 {
0071     struct mtd_info *mtd = file_inode(file)->i_sb->s_mtd;
0072
0073     if (!mtd)
0074         return NOMMU_MAP_COPY;
0075     return mtd_mmap_capabilities(mtd);
0076 }
0077
0078 const struct file_operations romfs_ro_fops = {
0079     .llseek         = generic_file_llseek,
0080     .read_iter      = generic_file_read_iter,
0081     .splice_read        = generic_file_splice_read,
0082     .mmap           = romfs_mmap,
0083     .get_unmapped_area  = romfs_get_unmapped_area,
0084     .mmap_capabilities  = romfs_mmap_capabilities,
0085 };