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(f: 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 | |