1 /*
2 * XZ decoder tester
3 *
4 * Author: Lasse Collin <lasse.collin@tukaani.org>
5 *
6 * This file has been put into the public domain.
7 * You can do whatever you want with this file.
8 */
9
10 #include <linux/kernel.h>
11 #include <linux/module.h>
12 #include <linux/fs.h>
13 #include <linux/uaccess.h>
14 #include <linux/crc32.h>
15 #include <linux/xz.h>
16
17 /* Maximum supported dictionary size */
18 #define DICT_MAX (1 << 20)
19
20 /* Device name to pass to register_chrdev(). */
21 #define DEVICE_NAME "xz_dec_test"
22
23 /* Dynamically allocated device major number */
24 static int device_major;
25
26 /*
27 * We reuse the same decoder state, and thus can decode only one
28 * file at a time.
29 */
30 static bool device_is_open;
31
32 /* XZ decoder state */
33 static struct xz_dec *state;
34
35 /*
36 * Return value of xz_dec_run(). We need to avoid calling xz_dec_run() after
37 * it has returned XZ_STREAM_END, so we make this static.
38 */
39 static enum xz_ret ret;
40
41 /*
42 * Input and output buffers. The input buffer is used as a temporary safe
43 * place for the data coming from the userspace.
44 */
45 static uint8_t buffer_in[1024];
46 static uint8_t buffer_out[1024];
47
48 /*
49 * Structure to pass the input and output buffers to the XZ decoder.
50 * A few of the fields are never modified so we initialize them here.
51 */
52 static struct xz_buf buffers = {
53 .in = buffer_in,
54 .out = buffer_out,
55 .out_size = sizeof(buffer_out)
56 };
57
58 /*
59 * CRC32 of uncompressed data. This is used to give the user a simple way
60 * to check that the decoder produces correct output.
61 */
62 static uint32_t crc;
63
xz_dec_test_open(struct inode * i,struct file * f)64 static int xz_dec_test_open(struct inode *i, struct file *f)
65 {
66 if (device_is_open)
67 return -EBUSY;
68
69 device_is_open = true;
70
71 xz_dec_reset(state);
72 ret = XZ_OK;
73 crc = 0xFFFFFFFF;
74
75 buffers.in_pos = 0;
76 buffers.in_size = 0;
77 buffers.out_pos = 0;
78
79 printk(KERN_INFO DEVICE_NAME ": opened\n");
80 return 0;
81 }
82
xz_dec_test_release(struct inode * i,struct file * f)83 static int xz_dec_test_release(struct inode *i, struct file *f)
84 {
85 device_is_open = false;
86
87 if (ret == XZ_OK)
88 printk(KERN_INFO DEVICE_NAME ": input was truncated\n");
89
90 printk(KERN_INFO DEVICE_NAME ": closed\n");
91 return 0;
92 }
93
94 /*
95 * Decode the data given to us from the userspace. CRC32 of the uncompressed
96 * data is calculated and is printed at the end of successful decoding. The
97 * uncompressed data isn't stored anywhere for further use.
98 *
99 * The .xz file must have exactly one Stream and no Stream Padding. The data
100 * after the first Stream is considered to be garbage.
101 */
xz_dec_test_write(struct file * file,const char __user * buf,size_t size,loff_t * pos)102 static ssize_t xz_dec_test_write(struct file *file, const char __user *buf,
103 size_t size, loff_t *pos)
104 {
105 size_t remaining;
106
107 if (ret != XZ_OK) {
108 if (size > 0)
109 printk(KERN_INFO DEVICE_NAME ": %zu bytes of "
110 "garbage at the end of the file\n",
111 size);
112
113 return -ENOSPC;
114 }
115
116 printk(KERN_INFO DEVICE_NAME ": decoding %zu bytes of input\n",
117 size);
118
119 remaining = size;
120 while ((remaining > 0 || buffers.out_pos == buffers.out_size)
121 && ret == XZ_OK) {
122 if (buffers.in_pos == buffers.in_size) {
123 buffers.in_pos = 0;
124 buffers.in_size = min(remaining, sizeof(buffer_in));
125 if (copy_from_user(buffer_in, buf, buffers.in_size))
126 return -EFAULT;
127
128 buf += buffers.in_size;
129 remaining -= buffers.in_size;
130 }
131
132 buffers.out_pos = 0;
133 ret = xz_dec_run(state, &buffers);
134 crc = crc32(crc, buffer_out, buffers.out_pos);
135 }
136
137 switch (ret) {
138 case XZ_OK:
139 printk(KERN_INFO DEVICE_NAME ": XZ_OK\n");
140 return size;
141
142 case XZ_STREAM_END:
143 printk(KERN_INFO DEVICE_NAME ": XZ_STREAM_END, "
144 "CRC32 = 0x%08X\n", ~crc);
145 return size - remaining - (buffers.in_size - buffers.in_pos);
146
147 case XZ_MEMLIMIT_ERROR:
148 printk(KERN_INFO DEVICE_NAME ": XZ_MEMLIMIT_ERROR\n");
149 break;
150
151 case XZ_FORMAT_ERROR:
152 printk(KERN_INFO DEVICE_NAME ": XZ_FORMAT_ERROR\n");
153 break;
154
155 case XZ_OPTIONS_ERROR:
156 printk(KERN_INFO DEVICE_NAME ": XZ_OPTIONS_ERROR\n");
157 break;
158
159 case XZ_DATA_ERROR:
160 printk(KERN_INFO DEVICE_NAME ": XZ_DATA_ERROR\n");
161 break;
162
163 case XZ_BUF_ERROR:
164 printk(KERN_INFO DEVICE_NAME ": XZ_BUF_ERROR\n");
165 break;
166
167 default:
168 printk(KERN_INFO DEVICE_NAME ": Bug detected!\n");
169 break;
170 }
171
172 return -EIO;
173 }
174
175 /* Allocate the XZ decoder state and register the character device. */
xz_dec_test_init(void)176 static int __init xz_dec_test_init(void)
177 {
178 static const struct file_operations fileops = {
179 .owner = THIS_MODULE,
180 .open = &xz_dec_test_open,
181 .release = &xz_dec_test_release,
182 .write = &xz_dec_test_write
183 };
184
185 state = xz_dec_init(XZ_PREALLOC, DICT_MAX);
186 if (state == NULL)
187 return -ENOMEM;
188
189 device_major = register_chrdev(0, DEVICE_NAME, &fileops);
190 if (device_major < 0) {
191 xz_dec_end(state);
192 return device_major;
193 }
194
195 printk(KERN_INFO DEVICE_NAME ": module loaded\n");
196 printk(KERN_INFO DEVICE_NAME ": Create a device node with "
197 "'mknod " DEVICE_NAME " c %d 0' and write .xz files "
198 "to it.\n", device_major);
199 return 0;
200 }
201
xz_dec_test_exit(void)202 static void __exit xz_dec_test_exit(void)
203 {
204 unregister_chrdev(device_major, DEVICE_NAME);
205 xz_dec_end(state);
206 printk(KERN_INFO DEVICE_NAME ": module unloaded\n");
207 }
208
209 module_init(xz_dec_test_init);
210 module_exit(xz_dec_test_exit);
211
212 MODULE_DESCRIPTION("XZ decompressor tester");
213 MODULE_VERSION("1.0");
214 MODULE_AUTHOR("Lasse Collin <lasse.collin@tukaani.org>");
215
216 /*
217 * This code is in the public domain, but in Linux it's simplest to just
218 * say it's GPL and consider the authors as the copyright holders.
219 */
220 MODULE_LICENSE("GPL");
221