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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  * block.c
22  */
23 
24 /*
25  * This file implements the low-level routines to read and decompress
26  * datablocks and metadata blocks.
27  */
28 
29 #include <linux/fs.h>
30 #include <linux/vfs.h>
31 #include <linux/slab.h>
32 #include <linux/mutex.h>
33 #include <linux/string.h>
34 #include <linux/buffer_head.h>
35 #include <linux/zlib.h>
36 
37 #include "squashfs_fs.h"
38 #include "squashfs_fs_sb.h"
39 #include "squashfs_fs_i.h"
40 #include "squashfs.h"
41 
42 /*
43  * Read the metadata block length, this is stored in the first two
44  * bytes of the metadata block.
45  */
get_block_length(struct super_block * sb,u64 * cur_index,int * offset,int * length)46 static struct buffer_head *get_block_length(struct super_block *sb,
47 			u64 *cur_index, int *offset, int *length)
48 {
49 	struct squashfs_sb_info *msblk = sb->s_fs_info;
50 	struct buffer_head *bh;
51 
52 	bh = sb_bread(sb, *cur_index);
53 	if (bh == NULL)
54 		return NULL;
55 
56 	if (msblk->devblksize - *offset == 1) {
57 		*length = (unsigned char) bh->b_data[*offset];
58 		put_bh(bh);
59 		bh = sb_bread(sb, ++(*cur_index));
60 		if (bh == NULL)
61 			return NULL;
62 		*length |= (unsigned char) bh->b_data[0] << 8;
63 		*offset = 1;
64 	} else {
65 		*length = (unsigned char) bh->b_data[*offset] |
66 			(unsigned char) bh->b_data[*offset + 1] << 8;
67 		*offset += 2;
68 	}
69 
70 	return bh;
71 }
72 
73 
74 /*
75  * Read and decompress a metadata block or datablock.  Length is non-zero
76  * if a datablock is being read (the size is stored elsewhere in the
77  * filesystem), otherwise the length is obtained from the first two bytes of
78  * the metadata block.  A bit in the length field indicates if the block
79  * is stored uncompressed in the filesystem (usually because compression
80  * generated a larger block - this does occasionally happen with zlib).
81  */
squashfs_read_data(struct super_block * sb,void ** buffer,u64 index,int length,u64 * next_index,int srclength)82 int squashfs_read_data(struct super_block *sb, void **buffer, u64 index,
83 			int length, u64 *next_index, int srclength)
84 {
85 	struct squashfs_sb_info *msblk = sb->s_fs_info;
86 	struct buffer_head **bh;
87 	int offset = index & ((1 << msblk->devblksize_log2) - 1);
88 	u64 cur_index = index >> msblk->devblksize_log2;
89 	int bytes, compressed, b = 0, k = 0, page = 0, avail;
90 
91 
92 	bh = kcalloc((msblk->block_size >> msblk->devblksize_log2) + 1,
93 				sizeof(*bh), GFP_KERNEL);
94 	if (bh == NULL)
95 		return -ENOMEM;
96 
97 	if (length) {
98 		/*
99 		 * Datablock.
100 		 */
101 		bytes = -offset;
102 		compressed = SQUASHFS_COMPRESSED_BLOCK(length);
103 		length = SQUASHFS_COMPRESSED_SIZE_BLOCK(length);
104 		if (next_index)
105 			*next_index = index + length;
106 
107 		TRACE("Block @ 0x%llx, %scompressed size %d, src size %d\n",
108 			index, compressed ? "" : "un", length, srclength);
109 
110 		if (length < 0 || length > srclength ||
111 				(index + length) > msblk->bytes_used)
112 			goto read_failure;
113 
114 		for (b = 0; bytes < length; b++, cur_index++) {
115 			bh[b] = sb_getblk(sb, cur_index);
116 			if (bh[b] == NULL)
117 				goto block_release;
118 			bytes += msblk->devblksize;
119 		}
120 		ll_rw_block(READ, b, bh);
121 	} else {
122 		/*
123 		 * Metadata block.
124 		 */
125 		if ((index + 2) > msblk->bytes_used)
126 			goto read_failure;
127 
128 		bh[0] = get_block_length(sb, &cur_index, &offset, &length);
129 		if (bh[0] == NULL)
130 			goto read_failure;
131 		b = 1;
132 
133 		bytes = msblk->devblksize - offset;
134 		compressed = SQUASHFS_COMPRESSED(length);
135 		length = SQUASHFS_COMPRESSED_SIZE(length);
136 		if (next_index)
137 			*next_index = index + length + 2;
138 
139 		TRACE("Block @ 0x%llx, %scompressed size %d\n", index,
140 				compressed ? "" : "un", length);
141 
142 		if (length < 0 || length > srclength ||
143 					(index + length) > msblk->bytes_used)
144 			goto block_release;
145 
146 		for (; bytes < length; b++) {
147 			bh[b] = sb_getblk(sb, ++cur_index);
148 			if (bh[b] == NULL)
149 				goto block_release;
150 			bytes += msblk->devblksize;
151 		}
152 		ll_rw_block(READ, b - 1, bh + 1);
153 	}
154 
155 	if (compressed) {
156 		int zlib_err = 0, zlib_init = 0;
157 
158 		/*
159 		 * Uncompress block.
160 		 */
161 
162 		mutex_lock(&msblk->read_data_mutex);
163 
164 		msblk->stream.avail_out = 0;
165 		msblk->stream.avail_in = 0;
166 
167 		bytes = length;
168 		do {
169 			if (msblk->stream.avail_in == 0 && k < b) {
170 				avail = min(bytes, msblk->devblksize - offset);
171 				bytes -= avail;
172 				wait_on_buffer(bh[k]);
173 				if (!buffer_uptodate(bh[k]))
174 					goto release_mutex;
175 
176 				if (avail == 0) {
177 					offset = 0;
178 					put_bh(bh[k++]);
179 					continue;
180 				}
181 
182 				msblk->stream.next_in = bh[k]->b_data + offset;
183 				msblk->stream.avail_in = avail;
184 				offset = 0;
185 			}
186 
187 			if (msblk->stream.avail_out == 0) {
188 				msblk->stream.next_out = buffer[page++];
189 				msblk->stream.avail_out = PAGE_CACHE_SIZE;
190 			}
191 
192 			if (!zlib_init) {
193 				zlib_err = zlib_inflateInit(&msblk->stream);
194 				if (zlib_err != Z_OK) {
195 					ERROR("zlib_inflateInit returned"
196 						" unexpected result 0x%x,"
197 						" srclength %d\n", zlib_err,
198 						srclength);
199 					goto release_mutex;
200 				}
201 				zlib_init = 1;
202 			}
203 
204 			zlib_err = zlib_inflate(&msblk->stream, Z_NO_FLUSH);
205 
206 			if (msblk->stream.avail_in == 0 && k < b)
207 				put_bh(bh[k++]);
208 		} while (zlib_err == Z_OK);
209 
210 		if (zlib_err != Z_STREAM_END) {
211 			ERROR("zlib_inflate returned unexpected result"
212 				" 0x%x, srclength %d, avail_in %d,"
213 				" avail_out %d\n", zlib_err, srclength,
214 				msblk->stream.avail_in,
215 				msblk->stream.avail_out);
216 			goto release_mutex;
217 		}
218 
219 		zlib_err = zlib_inflateEnd(&msblk->stream);
220 		if (zlib_err != Z_OK) {
221 			ERROR("zlib_inflateEnd returned unexpected result 0x%x,"
222 				" srclength %d\n", zlib_err, srclength);
223 			goto release_mutex;
224 		}
225 		length = msblk->stream.total_out;
226 		mutex_unlock(&msblk->read_data_mutex);
227 	} else {
228 		/*
229 		 * Block is uncompressed.
230 		 */
231 		int i, in, pg_offset = 0;
232 
233 		for (i = 0; i < b; i++) {
234 			wait_on_buffer(bh[i]);
235 			if (!buffer_uptodate(bh[i]))
236 				goto block_release;
237 		}
238 
239 		for (bytes = length; k < b; k++) {
240 			in = min(bytes, msblk->devblksize - offset);
241 			bytes -= in;
242 			while (in) {
243 				if (pg_offset == PAGE_CACHE_SIZE) {
244 					page++;
245 					pg_offset = 0;
246 				}
247 				avail = min_t(int, in, PAGE_CACHE_SIZE -
248 						pg_offset);
249 				memcpy(buffer[page] + pg_offset,
250 						bh[k]->b_data + offset, avail);
251 				in -= avail;
252 				pg_offset += avail;
253 				offset += avail;
254 			}
255 			offset = 0;
256 			put_bh(bh[k]);
257 		}
258 	}
259 
260 	kfree(bh);
261 	return length;
262 
263 release_mutex:
264 	mutex_unlock(&msblk->read_data_mutex);
265 
266 block_release:
267 	for (; k < b; k++)
268 		put_bh(bh[k]);
269 
270 read_failure:
271 	ERROR("sb_bread failed reading block 0x%llx\n", cur_index);
272 	kfree(bh);
273 	return -EIO;
274 }
275