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
33static int squashfs_symlink_read_folio(struct file *file, struct folio *folio)
34{
35	struct inode *inode = folio->mapping->host;
36	struct super_block *sb = inode->i_sb;
37	struct squashfs_sb_info *msblk = sb->s_fs_info;
38	int index = folio_pos(folio);
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, error;
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", folio->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			error = bytes;
60			goto 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_local to map the folio.  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			error = entry->error;
79			goto out;
80		}
81
82		pageaddr = kmap_local_folio(folio, 0);
83		copied = squashfs_copy_data(pageaddr + bytes, entry, offset,
84								length - bytes);
85		if (copied == length - bytes)
86			memset(pageaddr + length, 0, PAGE_SIZE - length);
87		else
88			block = entry->next_index;
89		kunmap_local(pageaddr);
90		squashfs_cache_put(entry);
91	}
92
93	flush_dcache_folio(folio);
94	error = 0;
95out:
96	folio_end_read(folio, error == 0);
97	return error;
98}
99
100
101const struct address_space_operations squashfs_symlink_aops = {
102	.read_folio = squashfs_symlink_read_folio
103};
104
105const struct inode_operations squashfs_symlink_inode_ops = {
106	.get_link = page_get_link,
107	.listxattr = squashfs_listxattr
108};
109
110