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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@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 * 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/string.h>
33#include <linux/buffer_head.h>
34
35#include "squashfs_fs.h"
36#include "squashfs_fs_sb.h"
37#include "squashfs.h"
38#include "decompressor.h"
39
40/*
41 * Read the metadata block length, this is stored in the first two
42 * bytes of the metadata block.
43 */
44static struct buffer_head *get_block_length(struct super_block *sb,
45 u64 *cur_index, int *offset, int *length)
46{
47 struct squashfs_sb_info *msblk = sb->s_fs_info;
48 struct buffer_head *bh;
49
50 bh = sb_bread(sb, *cur_index);
51 if (bh == NULL)
52 return NULL;
53
54 if (msblk->devblksize - *offset == 1) {
55 *length = (unsigned char) bh->b_data[*offset];
56 put_bh(bh);
57 bh = sb_bread(sb, ++(*cur_index));
58 if (bh == NULL)
59 return NULL;
60 *length |= (unsigned char) bh->b_data[0] << 8;
61 *offset = 1;
62 } else {
63 *length = (unsigned char) bh->b_data[*offset] |
64 (unsigned char) bh->b_data[*offset + 1] << 8;
65 *offset += 2;
66
67 if (*offset == msblk->devblksize) {
68 put_bh(bh);
69 bh = sb_bread(sb, ++(*cur_index));
70 if (bh == NULL)
71 return NULL;
72 *offset = 0;
73 }
74 }
75
76 return bh;
77}
78
79
80/*
81 * Read and decompress a metadata block or datablock. Length is non-zero
82 * if a datablock is being read (the size is stored elsewhere in the
83 * filesystem), otherwise the length is obtained from the first two bytes of
84 * the metadata block. A bit in the length field indicates if the block
85 * is stored uncompressed in the filesystem (usually because compression
86 * generated a larger block - this does occasionally happen with zlib).
87 */
88int squashfs_read_data(struct super_block *sb, void **buffer, u64 index,
89 int length, u64 *next_index, int srclength, int pages)
90{
91 struct squashfs_sb_info *msblk = sb->s_fs_info;
92 struct buffer_head **bh;
93 int offset = index & ((1 << msblk->devblksize_log2) - 1);
94 u64 cur_index = index >> msblk->devblksize_log2;
95 int bytes, compressed, b = 0, k = 0, page = 0, avail;
96
97 bh = kcalloc(((srclength + msblk->devblksize - 1)
98 >> msblk->devblksize_log2) + 1, sizeof(*bh), GFP_KERNEL);
99 if (bh == NULL)
100 return -ENOMEM;
101
102 if (length) {
103 /*
104 * Datablock.
105 */
106 bytes = -offset;
107 compressed = SQUASHFS_COMPRESSED_BLOCK(length);
108 length = SQUASHFS_COMPRESSED_SIZE_BLOCK(length);
109 if (next_index)
110 *next_index = index + length;
111
112 TRACE("Block @ 0x%llx, %scompressed size %d, src size %d\n",
113 index, compressed ? "" : "un", length, srclength);
114
115 if (length < 0 || length > srclength ||
116 (index + length) > msblk->bytes_used)
117 goto read_failure;
118
119 for (b = 0; bytes < length; b++, cur_index++) {
120 bh[b] = sb_getblk(sb, cur_index);
121 if (bh[b] == NULL)
122 goto block_release;
123 bytes += msblk->devblksize;
124 }
125 ll_rw_block(READ, b, bh);
126 } else {
127 /*
128 * Metadata block.
129 */
130 if ((index + 2) > msblk->bytes_used)
131 goto read_failure;
132
133 bh[0] = get_block_length(sb, &cur_index, &offset, &length);
134 if (bh[0] == NULL)
135 goto read_failure;
136 b = 1;
137
138 bytes = msblk->devblksize - offset;
139 compressed = SQUASHFS_COMPRESSED(length);
140 length = SQUASHFS_COMPRESSED_SIZE(length);
141 if (next_index)
142 *next_index = index + length + 2;
143
144 TRACE("Block @ 0x%llx, %scompressed size %d\n", index,
145 compressed ? "" : "un", length);
146
147 if (length < 0 || length > srclength ||
148 (index + length) > msblk->bytes_used)
149 goto block_release;
150
151 for (; bytes < length; b++) {
152 bh[b] = sb_getblk(sb, ++cur_index);
153 if (bh[b] == NULL)
154 goto block_release;
155 bytes += msblk->devblksize;
156 }
157 ll_rw_block(READ, b - 1, bh + 1);
158 }
159
160 if (compressed) {
161 length = squashfs_decompress(msblk, buffer, bh, b, offset,
162 length, srclength, pages);
163 if (length < 0)
164 goto read_failure;
165 } else {
166 /*
167 * Block is uncompressed.
168 */
169 int i, in, pg_offset = 0;
170
171 for (i = 0; i < b; i++) {
172 wait_on_buffer(bh[i]);
173 if (!buffer_uptodate(bh[i]))
174 goto block_release;
175 }
176
177 for (bytes = length; k < b; k++) {
178 in = min(bytes, msblk->devblksize - offset);
179 bytes -= in;
180 while (in) {
181 if (pg_offset == PAGE_CACHE_SIZE) {
182 page++;
183 pg_offset = 0;
184 }
185 avail = min_t(int, in, PAGE_CACHE_SIZE -
186 pg_offset);
187 memcpy(buffer[page] + pg_offset,
188 bh[k]->b_data + offset, avail);
189 in -= avail;
190 pg_offset += avail;
191 offset += avail;
192 }
193 offset = 0;
194 put_bh(bh[k]);
195 }
196 }
197
198 kfree(bh);
199 return length;
200
201block_release:
202 for (; k < b; k++)
203 put_bh(bh[k]);
204
205read_failure:
206 ERROR("squashfs_read_data failed to read block 0x%llx\n",
207 (unsigned long long) index);
208 kfree(bh);
209 return -EIO;
210}
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 * block.c
9 */
10
11/*
12 * This file implements the low-level routines to read and decompress
13 * datablocks and metadata blocks.
14 */
15
16#include <linux/blkdev.h>
17#include <linux/fs.h>
18#include <linux/vfs.h>
19#include <linux/slab.h>
20#include <linux/string.h>
21#include <linux/buffer_head.h>
22#include <linux/bio.h>
23
24#include "squashfs_fs.h"
25#include "squashfs_fs_sb.h"
26#include "squashfs.h"
27#include "decompressor.h"
28#include "page_actor.h"
29
30/*
31 * Returns the amount of bytes copied to the page actor.
32 */
33static int copy_bio_to_actor(struct bio *bio,
34 struct squashfs_page_actor *actor,
35 int offset, int req_length)
36{
37 void *actor_addr = squashfs_first_page(actor);
38 struct bvec_iter_all iter_all = {};
39 struct bio_vec *bvec = bvec_init_iter_all(&iter_all);
40 int copied_bytes = 0;
41 int actor_offset = 0;
42
43 if (WARN_ON_ONCE(!bio_next_segment(bio, &iter_all)))
44 return 0;
45
46 while (copied_bytes < req_length) {
47 int bytes_to_copy = min_t(int, bvec->bv_len - offset,
48 PAGE_SIZE - actor_offset);
49
50 bytes_to_copy = min_t(int, bytes_to_copy,
51 req_length - copied_bytes);
52 memcpy(actor_addr + actor_offset,
53 page_address(bvec->bv_page) + bvec->bv_offset + offset,
54 bytes_to_copy);
55
56 actor_offset += bytes_to_copy;
57 copied_bytes += bytes_to_copy;
58 offset += bytes_to_copy;
59
60 if (actor_offset >= PAGE_SIZE) {
61 actor_addr = squashfs_next_page(actor);
62 if (!actor_addr)
63 break;
64 actor_offset = 0;
65 }
66 if (offset >= bvec->bv_len) {
67 if (!bio_next_segment(bio, &iter_all))
68 break;
69 offset = 0;
70 }
71 }
72 squashfs_finish_page(actor);
73 return copied_bytes;
74}
75
76static int squashfs_bio_read(struct super_block *sb, u64 index, int length,
77 struct bio **biop, int *block_offset)
78{
79 struct squashfs_sb_info *msblk = sb->s_fs_info;
80 const u64 read_start = round_down(index, msblk->devblksize);
81 const sector_t block = read_start >> msblk->devblksize_log2;
82 const u64 read_end = round_up(index + length, msblk->devblksize);
83 const sector_t block_end = read_end >> msblk->devblksize_log2;
84 int offset = read_start - round_down(index, PAGE_SIZE);
85 int total_len = (block_end - block) << msblk->devblksize_log2;
86 const int page_count = DIV_ROUND_UP(total_len + offset, PAGE_SIZE);
87 int error, i;
88 struct bio *bio;
89
90 if (page_count <= BIO_MAX_PAGES)
91 bio = bio_alloc(GFP_NOIO, page_count);
92 else
93 bio = bio_kmalloc(GFP_NOIO, page_count);
94
95 if (!bio)
96 return -ENOMEM;
97
98 bio_set_dev(bio, sb->s_bdev);
99 bio->bi_opf = READ;
100 bio->bi_iter.bi_sector = block * (msblk->devblksize >> SECTOR_SHIFT);
101
102 for (i = 0; i < page_count; ++i) {
103 unsigned int len =
104 min_t(unsigned int, PAGE_SIZE - offset, total_len);
105 struct page *page = alloc_page(GFP_NOIO);
106
107 if (!page) {
108 error = -ENOMEM;
109 goto out_free_bio;
110 }
111 if (!bio_add_page(bio, page, len, offset)) {
112 error = -EIO;
113 goto out_free_bio;
114 }
115 offset = 0;
116 total_len -= len;
117 }
118
119 error = submit_bio_wait(bio);
120 if (error)
121 goto out_free_bio;
122
123 *biop = bio;
124 *block_offset = index & ((1 << msblk->devblksize_log2) - 1);
125 return 0;
126
127out_free_bio:
128 bio_free_pages(bio);
129 bio_put(bio);
130 return error;
131}
132
133/*
134 * Read and decompress a metadata block or datablock. Length is non-zero
135 * if a datablock is being read (the size is stored elsewhere in the
136 * filesystem), otherwise the length is obtained from the first two bytes of
137 * the metadata block. A bit in the length field indicates if the block
138 * is stored uncompressed in the filesystem (usually because compression
139 * generated a larger block - this does occasionally happen with compression
140 * algorithms).
141 */
142int squashfs_read_data(struct super_block *sb, u64 index, int length,
143 u64 *next_index, struct squashfs_page_actor *output)
144{
145 struct squashfs_sb_info *msblk = sb->s_fs_info;
146 struct bio *bio = NULL;
147 int compressed;
148 int res;
149 int offset;
150
151 if (length) {
152 /*
153 * Datablock.
154 */
155 compressed = SQUASHFS_COMPRESSED_BLOCK(length);
156 length = SQUASHFS_COMPRESSED_SIZE_BLOCK(length);
157 TRACE("Block @ 0x%llx, %scompressed size %d, src size %d\n",
158 index, compressed ? "" : "un", length, output->length);
159 } else {
160 /*
161 * Metadata block.
162 */
163 const u8 *data;
164 struct bvec_iter_all iter_all = {};
165 struct bio_vec *bvec = bvec_init_iter_all(&iter_all);
166
167 if (index + 2 > msblk->bytes_used) {
168 res = -EIO;
169 goto out;
170 }
171 res = squashfs_bio_read(sb, index, 2, &bio, &offset);
172 if (res)
173 goto out;
174
175 if (WARN_ON_ONCE(!bio_next_segment(bio, &iter_all))) {
176 res = -EIO;
177 goto out_free_bio;
178 }
179 /* Extract the length of the metadata block */
180 data = page_address(bvec->bv_page) + bvec->bv_offset;
181 length = data[offset];
182 if (offset < bvec->bv_len - 1) {
183 length |= data[offset + 1] << 8;
184 } else {
185 if (WARN_ON_ONCE(!bio_next_segment(bio, &iter_all))) {
186 res = -EIO;
187 goto out_free_bio;
188 }
189 data = page_address(bvec->bv_page) + bvec->bv_offset;
190 length |= data[0] << 8;
191 }
192 bio_free_pages(bio);
193 bio_put(bio);
194
195 compressed = SQUASHFS_COMPRESSED(length);
196 length = SQUASHFS_COMPRESSED_SIZE(length);
197 index += 2;
198
199 TRACE("Block @ 0x%llx, %scompressed size %d\n", index,
200 compressed ? "" : "un", length);
201 }
202 if (next_index)
203 *next_index = index + length;
204
205 res = squashfs_bio_read(sb, index, length, &bio, &offset);
206 if (res)
207 goto out;
208
209 if (compressed) {
210 if (!msblk->stream) {
211 res = -EIO;
212 goto out_free_bio;
213 }
214 res = squashfs_decompress(msblk, bio, offset, length, output);
215 } else {
216 res = copy_bio_to_actor(bio, output, offset, length);
217 }
218
219out_free_bio:
220 bio_free_pages(bio);
221 bio_put(bio);
222out:
223 if (res < 0)
224 ERROR("Failed to read block 0x%llx: %d\n", index, res);
225
226 return res;
227}