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1 /*
2  * Squashfs - a compressed read only filesystem for Linux
3  *
4  * Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008
5  * Phillip Lougher <phillip@lougher.demon.co.uk>
6  *
7  * This program is free software; you can redistribute it and/or
8  * modify it under the terms of the GNU General Public License
9  * as published by the Free Software Foundation; either version 2,
10  * or (at your option) any later version.
11  *
12  * This program is distributed in the hope that it will be useful,
13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
15  * GNU General Public License for more details.
16  *
17  * You should have received a copy of the GNU General Public License
18  * along with this program; if not, write to the Free Software
19  * Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
20  *
21  * dir.c
22  */
23 
24 /*
25  * This file implements code to read directories from disk.
26  *
27  * See namei.c for a description of directory organisation on disk.
28  */
29 
30 #include <linux/fs.h>
31 #include <linux/vfs.h>
32 #include <linux/slab.h>
33 #include <linux/zlib.h>
34 
35 #include "squashfs_fs.h"
36 #include "squashfs_fs_sb.h"
37 #include "squashfs_fs_i.h"
38 #include "squashfs.h"
39 
40 static const unsigned char squashfs_filetype_table[] = {
41 	DT_UNKNOWN, DT_DIR, DT_REG, DT_LNK, DT_BLK, DT_CHR, DT_FIFO, DT_SOCK
42 };
43 
44 /*
45  * Lookup offset (f_pos) in the directory index, returning the
46  * metadata block containing it.
47  *
48  * If we get an error reading the index then return the part of the index
49  * (if any) we have managed to read - the index isn't essential, just
50  * quicker.
51  */
get_dir_index_using_offset(struct super_block * sb,u64 * next_block,int * next_offset,u64 index_start,int index_offset,int i_count,u64 f_pos)52 static int get_dir_index_using_offset(struct super_block *sb,
53 	u64 *next_block, int *next_offset, u64 index_start, int index_offset,
54 	int i_count, u64 f_pos)
55 {
56 	struct squashfs_sb_info *msblk = sb->s_fs_info;
57 	int err, i, index, length = 0;
58 	struct squashfs_dir_index dir_index;
59 
60 	TRACE("Entered get_dir_index_using_offset, i_count %d, f_pos %lld\n",
61 					i_count, f_pos);
62 
63 	/*
64 	 * Translate from external f_pos to the internal f_pos.  This
65 	 * is offset by 3 because we invent "." and ".." entries which are
66 	 * not actually stored in the directory.
67 	 */
68 	if (f_pos < 3)
69 		return f_pos;
70 	f_pos -= 3;
71 
72 	for (i = 0; i < i_count; i++) {
73 		err = squashfs_read_metadata(sb, &dir_index, &index_start,
74 				&index_offset, sizeof(dir_index));
75 		if (err < 0)
76 			break;
77 
78 		index = le32_to_cpu(dir_index.index);
79 		if (index > f_pos)
80 			/*
81 			 * Found the index we're looking for.
82 			 */
83 			break;
84 
85 		err = squashfs_read_metadata(sb, NULL, &index_start,
86 				&index_offset, le32_to_cpu(dir_index.size) + 1);
87 		if (err < 0)
88 			break;
89 
90 		length = index;
91 		*next_block = le32_to_cpu(dir_index.start_block) +
92 					msblk->directory_table;
93 	}
94 
95 	*next_offset = (length + *next_offset) % SQUASHFS_METADATA_SIZE;
96 
97 	/*
98 	 * Translate back from internal f_pos to external f_pos.
99 	 */
100 	return length + 3;
101 }
102 
103 
squashfs_readdir(struct file * file,void * dirent,filldir_t filldir)104 static int squashfs_readdir(struct file *file, void *dirent, filldir_t filldir)
105 {
106 	struct inode *inode = file->f_dentry->d_inode;
107 	struct squashfs_sb_info *msblk = inode->i_sb->s_fs_info;
108 	u64 block = squashfs_i(inode)->start + msblk->directory_table;
109 	int offset = squashfs_i(inode)->offset, length = 0, dir_count, size,
110 				type, err;
111 	unsigned int inode_number;
112 	struct squashfs_dir_header dirh;
113 	struct squashfs_dir_entry *dire;
114 
115 	TRACE("Entered squashfs_readdir [%llx:%x]\n", block, offset);
116 
117 	dire = kmalloc(sizeof(*dire) + SQUASHFS_NAME_LEN + 1, GFP_KERNEL);
118 	if (dire == NULL) {
119 		ERROR("Failed to allocate squashfs_dir_entry\n");
120 		goto finish;
121 	}
122 
123 	/*
124 	 * Return "." and  ".." entries as the first two filenames in the
125 	 * directory.  To maximise compression these two entries are not
126 	 * stored in the directory, and so we invent them here.
127 	 *
128 	 * It also means that the external f_pos is offset by 3 from the
129 	 * on-disk directory f_pos.
130 	 */
131 	while (file->f_pos < 3) {
132 		char *name;
133 		int i_ino;
134 
135 		if (file->f_pos == 0) {
136 			name = ".";
137 			size = 1;
138 			i_ino = inode->i_ino;
139 		} else {
140 			name = "..";
141 			size = 2;
142 			i_ino = squashfs_i(inode)->parent;
143 		}
144 
145 		TRACE("Calling filldir(%p, %s, %d, %lld, %d, %d)\n",
146 				dirent, name, size, file->f_pos, i_ino,
147 				squashfs_filetype_table[1]);
148 
149 		if (filldir(dirent, name, size, file->f_pos, i_ino,
150 				squashfs_filetype_table[1]) < 0) {
151 				TRACE("Filldir returned less than 0\n");
152 			goto finish;
153 		}
154 
155 		file->f_pos += size;
156 	}
157 
158 	length = get_dir_index_using_offset(inode->i_sb, &block, &offset,
159 				squashfs_i(inode)->dir_idx_start,
160 				squashfs_i(inode)->dir_idx_offset,
161 				squashfs_i(inode)->dir_idx_cnt,
162 				file->f_pos);
163 
164 	while (length < i_size_read(inode)) {
165 		/*
166 		 * Read directory header
167 		 */
168 		err = squashfs_read_metadata(inode->i_sb, &dirh, &block,
169 					&offset, sizeof(dirh));
170 		if (err < 0)
171 			goto failed_read;
172 
173 		length += sizeof(dirh);
174 
175 		dir_count = le32_to_cpu(dirh.count) + 1;
176 		while (dir_count--) {
177 			/*
178 			 * Read directory entry.
179 			 */
180 			err = squashfs_read_metadata(inode->i_sb, dire, &block,
181 					&offset, sizeof(*dire));
182 			if (err < 0)
183 				goto failed_read;
184 
185 			size = le16_to_cpu(dire->size) + 1;
186 
187 			err = squashfs_read_metadata(inode->i_sb, dire->name,
188 					&block, &offset, size);
189 			if (err < 0)
190 				goto failed_read;
191 
192 			length += sizeof(*dire) + size;
193 
194 			if (file->f_pos >= length)
195 				continue;
196 
197 			dire->name[size] = '\0';
198 			inode_number = le32_to_cpu(dirh.inode_number) +
199 				((short) le16_to_cpu(dire->inode_number));
200 			type = le16_to_cpu(dire->type);
201 
202 			TRACE("Calling filldir(%p, %s, %d, %lld, %x:%x, %d, %d)"
203 					"\n", dirent, dire->name, size,
204 					file->f_pos,
205 					le32_to_cpu(dirh.start_block),
206 					le16_to_cpu(dire->offset),
207 					inode_number,
208 					squashfs_filetype_table[type]);
209 
210 			if (filldir(dirent, dire->name, size, file->f_pos,
211 					inode_number,
212 					squashfs_filetype_table[type]) < 0) {
213 				TRACE("Filldir returned less than 0\n");
214 				goto finish;
215 			}
216 
217 			file->f_pos = length;
218 		}
219 	}
220 
221 finish:
222 	kfree(dire);
223 	return 0;
224 
225 failed_read:
226 	ERROR("Unable to read directory block [%llx:%x]\n", block, offset);
227 	kfree(dire);
228 	return 0;
229 }
230 
231 
232 const struct file_operations squashfs_dir_ops = {
233 	.read = generic_read_dir,
234 	.readdir = squashfs_readdir
235 };
236