xref: /openbmc/linux/fs/romfs/mmap-nommu.c (revision 2a598d0b)
1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /* NOMMU mmap support for RomFS on MTD devices
3  *
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 made
14  * - only supported for NOMMU at the moment (MMU can't doesn't copy private
15  *   mappings)
16  * - attempts to map through to the underlying MTD device
17  */
18 static 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 if
62  * possible
63  */
64 static 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 
69 static 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 
78 const 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