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* Author: Lasse Collin <lasse.collin@tukaani.org>
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* This file has been put into the public domain.
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* You can do whatever you want with this file.
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/uaccess.h>
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#include <linux/crc32.h>
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/* Maximum supported dictionary size */
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#define DICT_MAX (1 << 20)
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/* Device name to pass to register_chrdev(). */
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#define DEVICE_NAME "xz_dec_test"
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/* Dynamically allocated device major number */
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static int device_major;
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* We reuse the same decoder state, and thus can decode only one
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static bool device_is_open;
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/* XZ decoder state */
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static struct xz_dec *state;
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* Return value of xz_dec_run(). We need to avoid calling xz_dec_run() after
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* it has returned XZ_STREAM_END, so we make this static.
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static enum xz_ret ret;
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* Input and output buffers. The input buffer is used as a temporary safe
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* place for the data coming from the userspace.
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static uint8_t buffer_in[1024];
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static uint8_t buffer_out[1024];
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* Structure to pass the input and output buffers to the XZ decoder.
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* A few of the fields are never modified so we initialize them here.
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static struct xz_buf buffers = {
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.out_size = sizeof(buffer_out)
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* CRC32 of uncompressed data. This is used to give the user a simple way
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* to check that the decoder produces correct output.
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static int xz_dec_test_open(struct inode *i, struct file *f)
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device_is_open = true;
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printk(KERN_INFO DEVICE_NAME ": opened\n");
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static int xz_dec_test_release(struct inode *i, struct file *f)
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device_is_open = false;
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printk(KERN_INFO DEVICE_NAME ": input was truncated\n");
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printk(KERN_INFO DEVICE_NAME ": closed\n");
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* Decode the data given to us from the userspace. CRC32 of the uncompressed
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* data is calculated and is printed at the end of successful decoding. The
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* uncompressed data isn't stored anywhere for further use.
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* The .xz file must have exactly one Stream and no Stream Padding. The data
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* after the first Stream is considered to be garbage.
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static ssize_t xz_dec_test_write(struct file *file, const char __user *buf,
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size_t size, loff_t *pos)
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printk(KERN_INFO DEVICE_NAME ": %zu bytes of "
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"garbage at the end of the file\n",
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printk(KERN_INFO DEVICE_NAME ": decoding %zu bytes of input\n",
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while ((remaining > 0 || buffers.out_pos == buffers.out_size)
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if (buffers.in_pos == buffers.in_size) {
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buffers.in_size = min(remaining, sizeof(buffer_in));
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if (copy_from_user(buffer_in, buf, buffers.in_size))
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buf += buffers.in_size;
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remaining -= buffers.in_size;
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ret = xz_dec_run(state, &buffers);
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crc = crc32(crc, buffer_out, buffers.out_pos);
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printk(KERN_INFO DEVICE_NAME ": XZ_OK\n");
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printk(KERN_INFO DEVICE_NAME ": XZ_STREAM_END, "
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"CRC32 = 0x%08X\n", ~crc);
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return size - remaining - (buffers.in_size - buffers.in_pos);
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case XZ_MEMLIMIT_ERROR:
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printk(KERN_INFO DEVICE_NAME ": XZ_MEMLIMIT_ERROR\n");
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case XZ_FORMAT_ERROR:
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printk(KERN_INFO DEVICE_NAME ": XZ_FORMAT_ERROR\n");
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case XZ_OPTIONS_ERROR:
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printk(KERN_INFO DEVICE_NAME ": XZ_OPTIONS_ERROR\n");
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printk(KERN_INFO DEVICE_NAME ": XZ_DATA_ERROR\n");
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printk(KERN_INFO DEVICE_NAME ": XZ_BUF_ERROR\n");
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printk(KERN_INFO DEVICE_NAME ": Bug detected!\n");
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/* Allocate the XZ decoder state and register the character device. */
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static int __init xz_dec_test_init(void)
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static const struct file_operations fileops = {
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.owner = THIS_MODULE,
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.open = &xz_dec_test_open,
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.release = &xz_dec_test_release,
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.write = &xz_dec_test_write
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state = xz_dec_init(XZ_PREALLOC, DICT_MAX);
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device_major = register_chrdev(0, DEVICE_NAME, &fileops);
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if (device_major < 0) {
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printk(KERN_INFO DEVICE_NAME ": module loaded\n");
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printk(KERN_INFO DEVICE_NAME ": Create a device node with "
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"'mknod " DEVICE_NAME " c %d 0' and write .xz files "
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"to it.\n", device_major);
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static void __exit xz_dec_test_exit(void)
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unregister_chrdev(device_major, DEVICE_NAME);
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printk(KERN_INFO DEVICE_NAME ": module unloaded\n");
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module_init(xz_dec_test_init);
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module_exit(xz_dec_test_exit);
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MODULE_DESCRIPTION("XZ decompressor tester");
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MODULE_VERSION("1.0");
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MODULE_AUTHOR("Lasse Collin <lasse.collin@tukaani.org>");
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* This code is in the public domain, but in Linux it's simplest to just
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* say it's GPL and consider the authors as the copyright holders.
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MODULE_LICENSE("GPL");