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@squashfs.org.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
34#include "squashfs_fs.h"
35#include "squashfs_fs_sb.h"
36#include "squashfs_fs_i.h"
37#include "squashfs.h"
38
39static const unsigned char squashfs_filetype_table[] = {
40	DT_UNKNOWN, DT_DIR, DT_REG, DT_LNK, DT_BLK, DT_CHR, DT_FIFO, DT_SOCK
41};
42
43/*
44 * Lookup offset (f_pos) in the directory index, returning the
45 * metadata block containing it.
46 *
47 * If we get an error reading the index then return the part of the index
48 * (if any) we have managed to read - the index isn't essential, just
49 * quicker.
50 */
51static int get_dir_index_using_offset(struct super_block *sb,
52	u64 *next_block, int *next_offset, u64 index_start, int index_offset,
53	int i_count, u64 f_pos)
54{
55	struct squashfs_sb_info *msblk = sb->s_fs_info;
56	int err, i, index, length = 0;
57	unsigned int size;
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		size = le32_to_cpu(dir_index.size) + 1;
86
87		/* size should never be larger than SQUASHFS_NAME_LEN */
88		if (size > SQUASHFS_NAME_LEN)
89			break;
90
91		err = squashfs_read_metadata(sb, NULL, &index_start,
92				&index_offset, size);
93		if (err < 0)
94			break;
95
96		length = index;
97		*next_block = le32_to_cpu(dir_index.start_block) +
98					msblk->directory_table;
99	}
100
101	*next_offset = (length + *next_offset) % SQUASHFS_METADATA_SIZE;
102
103	/*
104	 * Translate back from internal f_pos to external f_pos.
105	 */
106	return length + 3;
107}
108
109
110static int squashfs_readdir(struct file *file, struct dir_context *ctx)
111{
112	struct inode *inode = file_inode(file);
113	struct squashfs_sb_info *msblk = inode->i_sb->s_fs_info;
114	u64 block = squashfs_i(inode)->start + msblk->directory_table;
115	int offset = squashfs_i(inode)->offset, length, err;
116	unsigned int inode_number, dir_count, size, type;
117	struct squashfs_dir_header dirh;
118	struct squashfs_dir_entry *dire;
119
120	TRACE("Entered squashfs_readdir [%llx:%x]\n", block, offset);
121
122	dire = kmalloc(sizeof(*dire) + SQUASHFS_NAME_LEN + 1, GFP_KERNEL);
123	if (dire == NULL) {
124		ERROR("Failed to allocate squashfs_dir_entry\n");
125		goto finish;
126	}
127
128	/*
129	 * Return "." and  ".." entries as the first two filenames in the
130	 * directory.  To maximise compression these two entries are not
131	 * stored in the directory, and so we invent them here.
132	 *
133	 * It also means that the external f_pos is offset by 3 from the
134	 * on-disk directory f_pos.
135	 */
136	while (ctx->pos < 3) {
137		char *name;
138		int i_ino;
139
140		if (ctx->pos == 0) {
141			name = ".";
142			size = 1;
143			i_ino = inode->i_ino;
144		} else {
145			name = "..";
146			size = 2;
147			i_ino = squashfs_i(inode)->parent;
148		}
149
150		if (!dir_emit(ctx, name, size, i_ino,
151				squashfs_filetype_table[1]))
152			goto finish;
153
154		ctx->pos += size;
155	}
156
157	length = get_dir_index_using_offset(inode->i_sb, &block, &offset,
158				squashfs_i(inode)->dir_idx_start,
159				squashfs_i(inode)->dir_idx_offset,
160				squashfs_i(inode)->dir_idx_cnt,
161				ctx->pos);
162
163	while (length < i_size_read(inode)) {
164		/*
165		 * Read directory header
166		 */
167		err = squashfs_read_metadata(inode->i_sb, &dirh, &block,
168					&offset, sizeof(dirh));
169		if (err < 0)
170			goto failed_read;
171
172		length += sizeof(dirh);
173
174		dir_count = le32_to_cpu(dirh.count) + 1;
175
176		if (dir_count > SQUASHFS_DIR_COUNT)
177			goto failed_read;
178
179		while (dir_count--) {
180			/*
181			 * Read directory entry.
182			 */
183			err = squashfs_read_metadata(inode->i_sb, dire, &block,
184					&offset, sizeof(*dire));
185			if (err < 0)
186				goto failed_read;
187
188			size = le16_to_cpu(dire->size) + 1;
189
190			/* size should never be larger than SQUASHFS_NAME_LEN */
191			if (size > SQUASHFS_NAME_LEN)
192				goto failed_read;
193
194			err = squashfs_read_metadata(inode->i_sb, dire->name,
195					&block, &offset, size);
196			if (err < 0)
197				goto failed_read;
198
199			length += sizeof(*dire) + size;
200
201			if (ctx->pos >= length)
202				continue;
203
204			dire->name[size] = '\0';
205			inode_number = le32_to_cpu(dirh.inode_number) +
206				((short) le16_to_cpu(dire->inode_number));
207			type = le16_to_cpu(dire->type);
208
209			if (type > SQUASHFS_MAX_DIR_TYPE)
210				goto failed_read;
211
212			if (!dir_emit(ctx, dire->name, size,
213					inode_number,
214					squashfs_filetype_table[type]))
215				goto finish;
216
217			ctx->pos = length;
218		}
219	}
220
221finish:
222	kfree(dire);
223	return 0;
224
225failed_read:
226	ERROR("Unable to read directory block [%llx:%x]\n", block, offset);
227	kfree(dire);
228	return 0;
229}
230
231
232const struct file_operations squashfs_dir_ops = {
233	.read = generic_read_dir,
234	.iterate = squashfs_readdir,
235	.llseek = default_llseek,
236};
237