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