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
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