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 */
24static int device_major;
25
26/*
27 * We reuse the same decoder state, and thus can decode only one
28 * file at a time.
29 */
30static bool device_is_open;
31
32/* XZ decoder state */
33static 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 */
39static 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 */
45static uint8_t buffer_in[1024];
46static 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 */
52static 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 */
62static uint32_t crc;
63
64static 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
83static 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 */
102static 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. */
176static 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
202static 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
209module_init(xz_dec_test_init);
210module_exit(xz_dec_test_exit);
211
212MODULE_DESCRIPTION("XZ decompressor tester");
213MODULE_VERSION("1.0");
214MODULE_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 */
220MODULE_LICENSE("GPL");
221