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
squashfs_symlink_readpage(struct file * file,struct page * page)33 static int squashfs_symlink_readpage(struct file *file, struct page *page)
34 {
35 struct inode *inode = page->mapping->host;
36 struct super_block *sb = inode->i_sb;
37 struct squashfs_sb_info *msblk = sb->s_fs_info;
38 int index = page->index << PAGE_SHIFT;
39 u64 block = squashfs_i(inode)->start;
40 int offset = squashfs_i(inode)->offset;
41 int length = min_t(int, i_size_read(inode) - index, PAGE_SIZE);
42 int bytes, copied;
43 void *pageaddr;
44 struct squashfs_cache_entry *entry;
45
46 TRACE("Entered squashfs_symlink_readpage, page index %ld, start block "
47 "%llx, offset %x\n", page->index, block, offset);
48
49 /*
50 * Skip index bytes into symlink metadata.
51 */
52 if (index) {
53 bytes = squashfs_read_metadata(sb, NULL, &block, &offset,
54 index);
55 if (bytes < 0) {
56 ERROR("Unable to read symlink [%llx:%x]\n",
57 squashfs_i(inode)->start,
58 squashfs_i(inode)->offset);
59 goto error_out;
60 }
61 }
62
63 /*
64 * Read length bytes from symlink metadata. Squashfs_read_metadata
65 * is not used here because it can sleep and we want to use
66 * kmap_atomic to map the page. Instead call the underlying
67 * squashfs_cache_get routine. As length bytes may overlap metadata
68 * blocks, we may need to call squashfs_cache_get multiple times.
69 */
70 for (bytes = 0; bytes < length; offset = 0, bytes += copied) {
71 entry = squashfs_cache_get(sb, msblk->block_cache, block, 0);
72 if (entry->error) {
73 ERROR("Unable to read symlink [%llx:%x]\n",
74 squashfs_i(inode)->start,
75 squashfs_i(inode)->offset);
76 squashfs_cache_put(entry);
77 goto error_out;
78 }
79
80 pageaddr = kmap_atomic(page);
81 copied = squashfs_copy_data(pageaddr + bytes, entry, offset,
82 length - bytes);
83 if (copied == length - bytes)
84 memset(pageaddr + length, 0, PAGE_SIZE - length);
85 else
86 block = entry->next_index;
87 kunmap_atomic(pageaddr);
88 squashfs_cache_put(entry);
89 }
90
91 flush_dcache_page(page);
92 SetPageUptodate(page);
93 unlock_page(page);
94 return 0;
95
96 error_out:
97 SetPageError(page);
98 unlock_page(page);
99 return 0;
100 }
101
102
103 const struct address_space_operations squashfs_symlink_aops = {
104 .readpage = squashfs_symlink_readpage
105 };
106
107 const struct inode_operations squashfs_symlink_inode_ops = {
108 .get_link = page_get_link,
109 .listxattr = squashfs_listxattr
110 };
111
112