lib/xz/xz_dec_test.c

   1 // SPDX-License-Identifier: 0BSD
   2
   3 /*
   4  * XZ decoder tester
   5  *
   6  * Author: Lasse Collin <[email protected]>
   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 */
  23 static int device_major;
  24
  25 /*
  26  * We reuse the same decoder state, and thus can decode only one
  27  * file at a time.
  28  */
  29 static bool device_is_open;
  30
  31 /* XZ decoder state */
  32 static 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  */
  38 static 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  */
  44 static uint8_t buffer_in[1024];
  45 static 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  */
  51 static 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  */
  61 static uint32_t crc;
  62
  63 static 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
  82 static 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  */
 101 static 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. */
 175 static 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
 201 static 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
 208 module_init(xz_dec_test_init);
 209 module_exit(xz_dec_test_exit);
 210
 211 MODULE_DESCRIPTION("XZ decompressor tester");
 212 MODULE_VERSION("1.0");
 213 MODULE_AUTHOR("Lasse Collin <[email protected]>");
 214 MODULE_LICENSE("Dual BSD/GPL");