1 | // SPDX-License-Identifier: GPL-2.0-or-later |
2 | /* |
3 | * Squashfs - a compressed read only filesystem for Linux |
4 | * |
5 | * Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008 |
6 | * Phillip Lougher <phillip@squashfs.org.uk> |
7 | * |
8 | * symlink.c |
9 | */ |
10 | |
11 | /* |
12 | * This file implements code to handle symbolic links. |
13 | * |
14 | * The data contents of symbolic links are stored inside the symbolic |
15 | * link inode within the inode table. This allows the normally small symbolic |
16 | * link to be compressed as part of the inode table, achieving much greater |
17 | * compression than if the symbolic link was compressed individually. |
18 | */ |
19 | |
20 | #include <linux/fs.h> |
21 | #include <linux/vfs.h> |
22 | #include <linux/kernel.h> |
23 | #include <linux/string.h> |
24 | #include <linux/pagemap.h> |
25 | #include <linux/xattr.h> |
26 | |
27 | #include "squashfs_fs.h" |
28 | #include "squashfs_fs_sb.h" |
29 | #include "squashfs_fs_i.h" |
30 | #include "squashfs.h" |
31 | #include "xattr.h" |
32 | |
33 | static int squashfs_symlink_read_folio(struct file *file, struct folio *folio) |
34 | { |
35 | struct page *page = &folio->page; |
36 | struct inode *inode = page->mapping->host; |
37 | struct super_block *sb = inode->i_sb; |
38 | struct squashfs_sb_info *msblk = sb->s_fs_info; |
39 | int index = page->index << PAGE_SHIFT; |
40 | u64 block = squashfs_i(inode)->start; |
41 | int offset = squashfs_i(inode)->offset; |
42 | int length = min_t(int, i_size_read(inode) - index, PAGE_SIZE); |
43 | int bytes, copied; |
44 | void *pageaddr; |
45 | struct squashfs_cache_entry *entry; |
46 | |
47 | TRACE("Entered squashfs_symlink_readpage, page index %ld, start block " |
48 | "%llx, offset %x\n" , page->index, block, offset); |
49 | |
50 | /* |
51 | * Skip index bytes into symlink metadata. |
52 | */ |
53 | if (index) { |
54 | bytes = squashfs_read_metadata(sb, NULL, &block, &offset, |
55 | index); |
56 | if (bytes < 0) { |
57 | ERROR("Unable to read symlink [%llx:%x]\n" , |
58 | squashfs_i(inode)->start, |
59 | squashfs_i(inode)->offset); |
60 | goto error_out; |
61 | } |
62 | } |
63 | |
64 | /* |
65 | * Read length bytes from symlink metadata. Squashfs_read_metadata |
66 | * is not used here because it can sleep and we want to use |
67 | * kmap_atomic to map the page. Instead call the underlying |
68 | * squashfs_cache_get routine. As length bytes may overlap metadata |
69 | * blocks, we may need to call squashfs_cache_get multiple times. |
70 | */ |
71 | for (bytes = 0; bytes < length; offset = 0, bytes += copied) { |
72 | entry = squashfs_cache_get(sb, msblk->block_cache, block, 0); |
73 | if (entry->error) { |
74 | ERROR("Unable to read symlink [%llx:%x]\n" , |
75 | squashfs_i(inode)->start, |
76 | squashfs_i(inode)->offset); |
77 | squashfs_cache_put(entry); |
78 | goto error_out; |
79 | } |
80 | |
81 | pageaddr = kmap_atomic(page); |
82 | copied = squashfs_copy_data(pageaddr + bytes, entry, offset, |
83 | length - bytes); |
84 | if (copied == length - bytes) |
85 | memset(pageaddr + length, 0, PAGE_SIZE - length); |
86 | else |
87 | block = entry->next_index; |
88 | kunmap_atomic(pageaddr); |
89 | squashfs_cache_put(entry); |
90 | } |
91 | |
92 | flush_dcache_page(page); |
93 | SetPageUptodate(page); |
94 | unlock_page(page); |
95 | return 0; |
96 | |
97 | error_out: |
98 | SetPageError(page); |
99 | unlock_page(page); |
100 | return 0; |
101 | } |
102 | |
103 | |
104 | const struct address_space_operations squashfs_symlink_aops = { |
105 | .read_folio = squashfs_symlink_read_folio |
106 | }; |
107 | |
108 | const struct inode_operations squashfs_symlink_inode_ops = { |
109 | .get_link = page_get_link, |
110 | .listxattr = squashfs_listxattr |
111 | }; |
112 | |
113 | |