1/* NOMMU mmap support for RomFS on MTD devices
2 *
3 * Copyright © 2007 Red Hat, Inc. All Rights Reserved.
4 * Written by David Howells (dhowells@redhat.com)
5 *
6 * This program is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU General Public License
8 * as published by the Free Software Foundation; either version
9 * 2 of the License, or (at your option) any later version.
10 */
11
12#include <linux/mm.h>
13#include <linux/mtd/super.h>
14#include "internal.h"
15
16/*
17 * try to determine where a shared mapping can be made
18 * - only supported for NOMMU at the moment (MMU can't doesn't copy private
19 *   mappings)
20 * - attempts to map through to the underlying MTD device
21 */
22static unsigned long romfs_get_unmapped_area(struct file *file,
23					     unsigned long addr,
24					     unsigned long len,
25					     unsigned long pgoff,
26					     unsigned long flags)
27{
28	struct inode *inode = file->f_mapping->host;
29	struct mtd_info *mtd = inode->i_sb->s_mtd;
30	unsigned long isize, offset, maxpages, lpages;
31	int ret;
32
33	if (!mtd)
34		return (unsigned long) -ENOSYS;
35
36	/* the mapping mustn't extend beyond the EOF */
37	lpages = (len + PAGE_SIZE - 1) >> PAGE_SHIFT;
38	isize = i_size_read(inode);
39	offset = pgoff << PAGE_SHIFT;
40
41	maxpages = (isize + PAGE_SIZE - 1) >> PAGE_SHIFT;
42	if ((pgoff >= maxpages) || (maxpages - pgoff < lpages))
43		return (unsigned long) -EINVAL;
44
45	if (addr != 0)
46		return (unsigned long) -EINVAL;
47
48	if (len > mtd->size || pgoff >= (mtd->size >> PAGE_SHIFT))
49		return (unsigned long) -EINVAL;
50
51	offset += ROMFS_I(inode)->i_dataoffset;
52	if (offset >= mtd->size)
53		return (unsigned long) -EINVAL;
54	/* the mapping mustn't extend beyond the EOF */
55	if ((offset + len) > mtd->size)
56		len = mtd->size - offset;
57
58	ret = mtd_get_unmapped_area(mtd, len, offset, flags);
59	if (ret == -EOPNOTSUPP)
60		ret = -ENOSYS;
61	return (unsigned long) ret;
62}
63
64/*
65 * permit a R/O mapping to be made directly through onto an MTD device if
66 * possible
67 */
68static int romfs_mmap(struct file *file, struct vm_area_struct *vma)
69{
70	return vma->vm_flags & (VM_SHARED | VM_MAYSHARE) ? 0 : -ENOSYS;
71}
72
73static unsigned romfs_mmap_capabilities(struct file *file)
74{
75	struct mtd_info *mtd = file_inode(file)->i_sb->s_mtd;
76
77	if (!mtd)
78		return NOMMU_MAP_COPY;
79	return mtd_mmap_capabilities(mtd);
80}
81
82const struct file_operations romfs_ro_fops = {
83	.llseek			= generic_file_llseek,
84	.read_iter		= generic_file_read_iter,
85	.splice_read		= generic_file_splice_read,
86	.mmap			= romfs_mmap,
87	.get_unmapped_area	= romfs_get_unmapped_area,
88	.mmap_capabilities	= romfs_mmap_capabilities,
89};
90