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07972dde PL |
1 | /* |
2 | * Squashfs - a compressed read only filesystem for Linux | |
3 | * | |
4 | * Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008 | |
d7f2ff67 | 5 | * Phillip Lougher <phillip@squashfs.org.uk> |
07972dde PL |
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> | |
07972dde PL |
33 | |
34 | #include "squashfs_fs.h" | |
35 | #include "squashfs_fs_sb.h" | |
36 | #include "squashfs_fs_i.h" | |
37 | #include "squashfs.h" | |
38 | ||
39 | static 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 | */ | |
51 | static 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 | struct squashfs_dir_index dir_index; | |
58 | ||
59 | TRACE("Entered get_dir_index_using_offset, i_count %d, f_pos %lld\n", | |
60 | i_count, f_pos); | |
61 | ||
62 | /* | |
63 | * Translate from external f_pos to the internal f_pos. This | |
64 | * is offset by 3 because we invent "." and ".." entries which are | |
65 | * not actually stored in the directory. | |
66 | */ | |
2158d3fd | 67 | if (f_pos <= 3) |
07972dde PL |
68 | return f_pos; |
69 | f_pos -= 3; | |
70 | ||
71 | for (i = 0; i < i_count; i++) { | |
72 | err = squashfs_read_metadata(sb, &dir_index, &index_start, | |
73 | &index_offset, sizeof(dir_index)); | |
74 | if (err < 0) | |
75 | break; | |
76 | ||
77 | index = le32_to_cpu(dir_index.index); | |
78 | if (index > f_pos) | |
79 | /* | |
80 | * Found the index we're looking for. | |
81 | */ | |
82 | break; | |
83 | ||
84 | err = squashfs_read_metadata(sb, NULL, &index_start, | |
85 | &index_offset, le32_to_cpu(dir_index.size) + 1); | |
86 | if (err < 0) | |
87 | break; | |
88 | ||
89 | length = index; | |
90 | *next_block = le32_to_cpu(dir_index.start_block) + | |
91 | msblk->directory_table; | |
92 | } | |
93 | ||
94 | *next_offset = (length + *next_offset) % SQUASHFS_METADATA_SIZE; | |
95 | ||
96 | /* | |
97 | * Translate back from internal f_pos to external f_pos. | |
98 | */ | |
99 | return length + 3; | |
100 | } | |
101 | ||
102 | ||
5f6039ce | 103 | static int squashfs_readdir(struct file *file, struct dir_context *ctx) |
07972dde | 104 | { |
496ad9aa | 105 | struct inode *inode = file_inode(file); |
07972dde PL |
106 | struct squashfs_sb_info *msblk = inode->i_sb->s_fs_info; |
107 | u64 block = squashfs_i(inode)->start + msblk->directory_table; | |
68e7f412 PL |
108 | int offset = squashfs_i(inode)->offset, length, type, err; |
109 | unsigned int inode_number, dir_count, size; | |
07972dde PL |
110 | struct squashfs_dir_header dirh; |
111 | struct squashfs_dir_entry *dire; | |
112 | ||
113 | TRACE("Entered squashfs_readdir [%llx:%x]\n", block, offset); | |
114 | ||
115 | dire = kmalloc(sizeof(*dire) + SQUASHFS_NAME_LEN + 1, GFP_KERNEL); | |
116 | if (dire == NULL) { | |
117 | ERROR("Failed to allocate squashfs_dir_entry\n"); | |
118 | goto finish; | |
119 | } | |
120 | ||
121 | /* | |
122 | * Return "." and ".." entries as the first two filenames in the | |
123 | * directory. To maximise compression these two entries are not | |
124 | * stored in the directory, and so we invent them here. | |
125 | * | |
126 | * It also means that the external f_pos is offset by 3 from the | |
127 | * on-disk directory f_pos. | |
128 | */ | |
5f6039ce | 129 | while (ctx->pos < 3) { |
07972dde PL |
130 | char *name; |
131 | int i_ino; | |
132 | ||
5f6039ce | 133 | if (ctx->pos == 0) { |
07972dde PL |
134 | name = "."; |
135 | size = 1; | |
136 | i_ino = inode->i_ino; | |
137 | } else { | |
138 | name = ".."; | |
139 | size = 2; | |
140 | i_ino = squashfs_i(inode)->parent; | |
141 | } | |
142 | ||
5f6039ce AV |
143 | if (!dir_emit(ctx, name, size, i_ino, |
144 | squashfs_filetype_table[1])) | |
07972dde | 145 | goto finish; |
07972dde | 146 | |
5f6039ce | 147 | ctx->pos += size; |
07972dde PL |
148 | } |
149 | ||
150 | length = get_dir_index_using_offset(inode->i_sb, &block, &offset, | |
151 | squashfs_i(inode)->dir_idx_start, | |
152 | squashfs_i(inode)->dir_idx_offset, | |
153 | squashfs_i(inode)->dir_idx_cnt, | |
5f6039ce | 154 | ctx->pos); |
07972dde PL |
155 | |
156 | while (length < i_size_read(inode)) { | |
157 | /* | |
158 | * Read directory header | |
159 | */ | |
160 | err = squashfs_read_metadata(inode->i_sb, &dirh, &block, | |
161 | &offset, sizeof(dirh)); | |
162 | if (err < 0) | |
163 | goto failed_read; | |
164 | ||
165 | length += sizeof(dirh); | |
166 | ||
167 | dir_count = le32_to_cpu(dirh.count) + 1; | |
44cff8a9 | 168 | |
4826d83d | 169 | if (dir_count > SQUASHFS_DIR_COUNT) |
44cff8a9 PL |
170 | goto failed_read; |
171 | ||
07972dde PL |
172 | while (dir_count--) { |
173 | /* | |
174 | * Read directory entry. | |
175 | */ | |
176 | err = squashfs_read_metadata(inode->i_sb, dire, &block, | |
177 | &offset, sizeof(*dire)); | |
178 | if (err < 0) | |
179 | goto failed_read; | |
180 | ||
181 | size = le16_to_cpu(dire->size) + 1; | |
182 | ||
44cff8a9 PL |
183 | /* size should never be larger than SQUASHFS_NAME_LEN */ |
184 | if (size > SQUASHFS_NAME_LEN) | |
185 | goto failed_read; | |
186 | ||
07972dde PL |
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 | ||
5f6039ce | 194 | if (ctx->pos >= length) |
07972dde PL |
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 | ||
5f6039ce | 202 | if (!dir_emit(ctx, dire->name, size, |
07972dde | 203 | inode_number, |
5f6039ce | 204 | squashfs_filetype_table[type])) |
07972dde | 205 | goto finish; |
07972dde | 206 | |
5f6039ce | 207 | ctx->pos = length; |
07972dde PL |
208 | } |
209 | } | |
210 | ||
211 | finish: | |
212 | kfree(dire); | |
213 | return 0; | |
214 | ||
215 | failed_read: | |
216 | ERROR("Unable to read directory block [%llx:%x]\n", block, offset); | |
217 | kfree(dire); | |
218 | return 0; | |
219 | } | |
220 | ||
221 | ||
222 | const struct file_operations squashfs_dir_ops = { | |
223 | .read = generic_read_dir, | |
5f6039ce | 224 | .iterate = squashfs_readdir, |
6038f373 | 225 | .llseek = default_llseek, |
07972dde | 226 | }; |