Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
tjh.dev
kernel
os
linux
1// SPDX-License-Identifier: 0BSD
2
3/*
4 * XZ decoder tester
5 *
6 * Author: Lasse Collin <lasse.collin@tukaani.org>
7 */
8
9#include <linux/kernel.h>
10#include <linux/module.h>
11#include <linux/fs.h>
12#include <linux/uaccess.h>
13#include <linux/crc32.h>
14#include <linux/xz.h>
15
16/* Maximum supported dictionary size */
17#define DICT_MAX (1 << 20)
18
19/* Device name to pass to register_chrdev(). */
20#define DEVICE_NAME "xz_dec_test"
21
22/* Dynamically allocated device major number */
23static int device_major;
24
25/*
26 * We reuse the same decoder state, and thus can decode only one
27 * file at a time.
28 */
29static bool device_is_open;
30
31/* XZ decoder state */
32static struct xz_dec *state;
33
34/*
35 * Return value of xz_dec_run(). We need to avoid calling xz_dec_run() after
36 * it has returned XZ_STREAM_END, so we make this static.
37 */
38static enum xz_ret ret;
39
40/*
41 * Input and output buffers. The input buffer is used as a temporary safe
42 * place for the data coming from the userspace.
43 */
44static uint8_t buffer_in[1024];
45static uint8_t buffer_out[1024];
46
47/*
48 * Structure to pass the input and output buffers to the XZ decoder.
49 * A few of the fields are never modified so we initialize them here.
50 */
51static struct xz_buf buffers = {
52 .in = buffer_in,
53 .out = buffer_out,
54 .out_size = sizeof(buffer_out)
55};
56
57/*
58 * CRC32 of uncompressed data. This is used to give the user a simple way
59 * to check that the decoder produces correct output.
60 */
61static uint32_t crc;
62
63static int xz_dec_test_open(struct inode *i, struct file *f)
64{
65 if (device_is_open)
66 return -EBUSY;
67
68 device_is_open = true;
69
70 xz_dec_reset(state);
71 ret = XZ_OK;
72 crc = 0xFFFFFFFF;
73
74 buffers.in_pos = 0;
75 buffers.in_size = 0;
76 buffers.out_pos = 0;
77
78 printk(KERN_INFO DEVICE_NAME ": opened\n");
79 return 0;
80}
81
82static int xz_dec_test_release(struct inode *i, struct file *f)
83{
84 device_is_open = false;
85
86 if (ret == XZ_OK)
87 printk(KERN_INFO DEVICE_NAME ": input was truncated\n");
88
89 printk(KERN_INFO DEVICE_NAME ": closed\n");
90 return 0;
91}
92
93/*
94 * Decode the data given to us from the userspace. CRC32 of the uncompressed
95 * data is calculated and is printed at the end of successful decoding. The
96 * uncompressed data isn't stored anywhere for further use.
97 *
98 * The .xz file must have exactly one Stream and no Stream Padding. The data
99 * after the first Stream is considered to be garbage.
100 */
101static ssize_t xz_dec_test_write(struct file *file, const char __user *buf,
102 size_t size, loff_t *pos)
103{
104 size_t remaining;
105
106 if (ret != XZ_OK) {
107 if (size > 0)
108 printk(KERN_INFO DEVICE_NAME ": %zu bytes of "
109 "garbage at the end of the file\n",
110 size);
111
112 return -ENOSPC;
113 }
114
115 printk(KERN_INFO DEVICE_NAME ": decoding %zu bytes of input\n",
116 size);
117
118 remaining = size;
119 while ((remaining > 0 || buffers.out_pos == buffers.out_size)
120 && ret == XZ_OK) {
121 if (buffers.in_pos == buffers.in_size) {
122 buffers.in_pos = 0;
123 buffers.in_size = min(remaining, sizeof(buffer_in));
124 if (copy_from_user(buffer_in, buf, buffers.in_size))
125 return -EFAULT;
126
127 buf += buffers.in_size;
128 remaining -= buffers.in_size;
129 }
130
131 buffers.out_pos = 0;
132 ret = xz_dec_run(state, &buffers);
133 crc = crc32(crc, buffer_out, buffers.out_pos);
134 }
135
136 switch (ret) {
137 case XZ_OK:
138 printk(KERN_INFO DEVICE_NAME ": XZ_OK\n");
139 return size;
140
141 case XZ_STREAM_END:
142 printk(KERN_INFO DEVICE_NAME ": XZ_STREAM_END, "
143 "CRC32 = 0x%08X\n", ~crc);
144 return size - remaining - (buffers.in_size - buffers.in_pos);
145
146 case XZ_MEMLIMIT_ERROR:
147 printk(KERN_INFO DEVICE_NAME ": XZ_MEMLIMIT_ERROR\n");
148 break;
149
150 case XZ_FORMAT_ERROR:
151 printk(KERN_INFO DEVICE_NAME ": XZ_FORMAT_ERROR\n");
152 break;
153
154 case XZ_OPTIONS_ERROR:
155 printk(KERN_INFO DEVICE_NAME ": XZ_OPTIONS_ERROR\n");
156 break;
157
158 case XZ_DATA_ERROR:
159 printk(KERN_INFO DEVICE_NAME ": XZ_DATA_ERROR\n");
160 break;
161
162 case XZ_BUF_ERROR:
163 printk(KERN_INFO DEVICE_NAME ": XZ_BUF_ERROR\n");
164 break;
165
166 default:
167 printk(KERN_INFO DEVICE_NAME ": Bug detected!\n");
168 break;
169 }
170
171 return -EIO;
172}
173
174/* Allocate the XZ decoder state and register the character device. */
175static int __init xz_dec_test_init(void)
176{
177 static const struct file_operations fileops = {
178 .owner = THIS_MODULE,
179 .open = &xz_dec_test_open,
180 .release = &xz_dec_test_release,
181 .write = &xz_dec_test_write
182 };
183
184 state = xz_dec_init(XZ_PREALLOC, DICT_MAX);
185 if (state == NULL)
186 return -ENOMEM;
187
188 device_major = register_chrdev(0, DEVICE_NAME, &fileops);
189 if (device_major < 0) {
190 xz_dec_end(state);
191 return device_major;
192 }
193
194 printk(KERN_INFO DEVICE_NAME ": module loaded\n");
195 printk(KERN_INFO DEVICE_NAME ": Create a device node with "
196 "'mknod " DEVICE_NAME " c %d 0' and write .xz files "
197 "to it.\n", device_major);
198 return 0;
199}
200
201static void __exit xz_dec_test_exit(void)
202{
203 unregister_chrdev(device_major, DEVICE_NAME);
204 xz_dec_end(state);
205 printk(KERN_INFO DEVICE_NAME ": module unloaded\n");
206}
207
208module_init(xz_dec_test_init);
209module_exit(xz_dec_test_exit);
210
211MODULE_DESCRIPTION("XZ decompressor tester");
212MODULE_VERSION("1.0");
213MODULE_AUTHOR("Lasse Collin <lasse.collin@tukaani.org>");
214MODULE_LICENSE("Dual BSD/GPL");