crypto/lzf.c

   1 /*
   2  * Cryptoapi LZF compression module.
   3  *
   4  * Copyright (c) 2004-2008 Nigel Cunningham <nigel at tuxonice net>
   5  *
   6  * based on the deflate.c file:
   7  *
   8  * Copyright (c) 2003 James Morris <jmorris@intercode.com.au>
   9  *
  10  * and upon the LZF compression module donated to the TuxOnIce project with
  11  * the following copyright:
  12  *
  13  * This program is free software; you can redistribute it and/or modify it
  14  * under the terms of the GNU General Public License as published by the Free
  15  * Software Foundation; either version 2 of the License, or (at your option)
  16  * any later version.
  17  * Copyright (c) 2000-2003 Marc Alexander Lehmann <pcg@goof.com>
  18  *
  19  * Redistribution and use in source and binary forms, with or without modifica-
  20  * tion, are permitted provided that the following conditions are met:
  21  *
  22  *   1.  Redistributions of source code must retain the above copyright notice,
  23  *       this list of conditions and the following disclaimer.
  24  *
  25  *   2.  Redistributions in binary form must reproduce the above copyright
  26  *       notice, this list of conditions and the following disclaimer in the
  27  *       documentation and/or other materials provided with the distribution.
  28  *
  29  *   3.  The name of the author may not be used to endorse or promote products
  30  *       derived from this software without specific prior written permission.
  31  *
  32  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
  33  * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MER-
  34  * CHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO
  35  * EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPE-
  36  * CIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  37  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
  38  * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
  39  * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTH-
  40  * ERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
  41  * OF THE POSSIBILITY OF SUCH DAMAGE.
  42  *
  43  * Alternatively, the contents of this file may be used under the terms of
  44  * the GNU General Public License version 2 (the "GPL"), in which case the
  45  * provisions of the GPL are applicable instead of the above. If you wish to
  46  * allow the use of your version of this file only under the terms of the
  47  * GPL and not to allow others to use your version of this file under the
  48  * BSD license, indicate your decision by deleting the provisions above and
  49  * replace them with the notice and other provisions required by the GPL. If
  50  * you do not delete the provisions above, a recipient may use your version
  51  * of this file under either the BSD or the GPL.
  52  */
  53
  54 #include <linux/kernel.h>
  55 #include <linux/module.h>
  56 #include <linux/init.h>
  57 #include <linux/module.h>
  58 #include <linux/crypto.h>
  59 #include <linux/err.h>
  60 #include <linux/vmalloc.h>
  61 #include <linux/string.h>
  62
  63 struct lzf_ctx {
  64         void *hbuf;
  65         unsigned int bufofs;
  66 };
  67
  68 /*
  69  * size of hashtable is (1 << hlog) * sizeof (char *)
  70  * decompression is independent of the hash table size
  71  * the difference between 15 and 14 is very small
  72  * for small blocks (and 14 is also faster).
  73  * For a low-memory configuration, use hlog == 13;
  74  * For best compression, use 15 or 16.
  75  */
  76 static const int hlog = 13;
  77
  78 /*
  79  * don't play with this unless you benchmark!
  80  * decompression is not dependent on the hash function
  81  * the hashing function might seem strange, just believe me
  82  * it works ;)
  83  */
  84 static inline u16 first(const u8 *p)
  85 {
  86         return ((p[0]) << 8) + p[1];
  87 }
  88
  89 static inline u16 next(u8 v, const u8 *p)
  90 {
  91         return ((v) << 8) + p[2];
  92 }
  93
  94 static inline u32 idx(unsigned int h)
  95 {
  96         return (((h ^ (h << 5)) >> (3*8 - hlog)) + h*3) & ((1 << hlog) - 1);
  97 }
  98
  99 /*
 100  * IDX works because it is very similar to a multiplicative hash, e.g.
 101  * (h * 57321 >> (3*8 - hlog))
 102  * the next one is also quite good, albeit slow ;)
 103  * (int)(cos(h & 0xffffff) * 1e6)
 104  */
 105
 106 static const int max_lit = (1 <<  5);
 107 static const int max_off = (1 << 13);
 108 static const int max_ref = ((1 <<  8) + (1 << 3));
 109
 110 /*
 111  * compressed format
 112  *
 113  * 000LLLLL <L+1>    ; literal
 114  * LLLOOOOO oooooooo ; backref L
 115  * 111OOOOO LLLLLLLL oooooooo ; backref L+7
 116  *
 117  */
 118
 119 static void lzf_compress_exit(struct crypto_tfm *tfm)
 120 {
 121         struct lzf_ctx *ctx = crypto_tfm_ctx(tfm);
 122
 123         if (!ctx->hbuf)
 124                 return;
 125
 126         vfree(ctx->hbuf);
 127         ctx->hbuf = NULL;
 128 }
 129
 130 static int lzf_compress_init(struct crypto_tfm *tfm)
 131 {
 132         struct lzf_ctx *ctx = crypto_tfm_ctx(tfm);
 133
 134         /* Get LZF ready to go */
 135         ctx->hbuf = vmalloc_32((1 << hlog) * sizeof(char *));
 136         if (ctx->hbuf)
 137                 return 0;
 138
 139         printk(KERN_WARNING "Failed to allocate %ld bytes for lzf workspace\n",
 140                         (long) ((1 << hlog) * sizeof(char *)));
 141         return -ENOMEM;
 142 }
 143
 144 static int lzf_compress(struct crypto_tfm *tfm, const u8 *in_data,
 145                 unsigned int in_len, u8 *out_data, unsigned int *out_len)
 146 {
 147         struct lzf_ctx *ctx = crypto_tfm_ctx(tfm);
 148         const u8 **htab = ctx->hbuf;
 149         const u8 **hslot;
 150         const u8 *ip = in_data;
 151         u8 *op = out_data;
 152         const u8 *in_end = ip + in_len;
 153         u8 *out_end = op + *out_len - 3;
 154         const u8 *ref;
 155
 156         unsigned int hval = first(ip);
 157         unsigned long off;
 158         int lit = 0;
 159
 160         memset(htab, 0, sizeof(htab));
 161
 162         for (;;) {
 163                 if (ip < in_end - 2) {
 164                         hval = next(hval, ip);
 165                         hslot = htab + idx(hval);
 166                         ref = *hslot;
 167                         *hslot = ip;
 168
 169                         off = ip - ref - 1;
 170                         if (off < max_off
 171                             && ip + 4 < in_end && ref > in_data
 172                             && *(u16 *) ref == *(u16 *) ip && ref[2] == ip[2]
 173                             ) {
 174                                 /* match found at *ref++ */
 175                                 unsigned int len = 2;
 176                                 unsigned int maxlen = in_end - ip - len;
 177                                 maxlen = maxlen > max_ref ? max_ref : maxlen;
 178
 179                                 do {
 180                                         len++;
 181                                 } while (len < maxlen && ref[len] == ip[len]);
 182
 183                                 if (op + lit + 1 + 3 >= out_end) {
 184                                         *out_len = PAGE_SIZE;
 185                                         return 0;
 186                                 }
 187
 188                                 if (lit) {
 189                                         *op++ = lit - 1;
 190                                         lit = -lit;
 191                                         do {
 192                                                 *op++ = ip[lit];
 193                                         } while (++lit);
 194                                 }
 195
 196                                 len -= 2;
 197                                 ip++;
 198
 199                                 if (len < 7) {
 200                                         *op++ = (off >> 8) + (len << 5);
 201                                 } else {
 202                                         *op++ = (off >> 8) + (7 << 5);
 203                                         *op++ = len - 7;
 204                                 }
 205
 206                                 *op++ = off;
 207
 208                                 ip += len;
 209                                 hval = first(ip);
 210                                 hval = next(hval, ip);
 211                                 htab[idx(hval)] = ip;
 212                                 ip++;
 213                                 continue;
 214                         }
 215                 } else if (ip == in_end)
 216                         break;
 217
 218                 /* one more literal byte we must copy */
 219                 lit++;
 220                 ip++;
 221
 222                 if (lit == max_lit) {
 223                         if (op + 1 + max_lit >= out_end) {
 224                                 *out_len = PAGE_SIZE;
 225                                 return 0;
 226                         }
 227
 228                         *op++ = max_lit - 1;
 229                         memcpy(op, ip - max_lit, max_lit);
 230                         op += max_lit;
 231                         lit = 0;
 232                 }
 233         }
 234
 235         if (lit) {
 236                 if (op + lit + 1 >= out_end) {
 237                         *out_len = PAGE_SIZE;
 238                         return 0;
 239                 }
 240
 241                 *op++ = lit - 1;
 242                 lit = -lit;
 243                 do {
 244                         *op++ = ip[lit];
 245                 } while (++lit);
 246         }
 247
 248         *out_len = op - out_data;
 249         return 0;
 250 }
 251
 252 static int lzf_decompress(struct crypto_tfm *tfm, const u8 *src,
 253                 unsigned int slen, u8 *dst, unsigned int *dlen)
 254 {
 255         u8 const *ip = src;
 256         u8 *op = dst;
 257         u8 const *const in_end = ip + slen;
 258         u8 *const out_end = op + *dlen;
 259
 260         *dlen = PAGE_SIZE;
 261         do {
 262                 unsigned int ctrl = *ip++;
 263
 264                 if (ctrl < (1 << 5)) {
 265                         /* literal run */
 266                         ctrl++;
 267
 268                         if (op + ctrl > out_end)
 269                                 return 0;
 270                         memcpy(op, ip, ctrl);
 271                         op += ctrl;
 272                         ip += ctrl;
 273                 } else {        /* back reference */
 274
 275                         unsigned int len = ctrl >> 5;
 276
 277                         u8 *ref = op - ((ctrl & 0x1f) << 8) - 1;
 278
 279                         if (len == 7)
 280                                 len += *ip++;
 281
 282                         ref -= *ip++;
 283                         len += 2;
 284
 285                         if (op + len > out_end || ref < (u8 *) dst)
 286                                 return 0;
 287
 288                         do {
 289                                 *op++ = *ref++;
 290                         } while (--len);
 291                 }
 292         } while (op < out_end && ip < in_end);
 293
 294         *dlen = op - (u8 *) dst;
 295         return 0;
 296 }
 297
 298 static struct crypto_alg alg = {
 299         .cra_name = "lzf",
 300         .cra_flags = CRYPTO_ALG_TYPE_COMPRESS,
 301         .cra_ctxsize = sizeof(struct lzf_ctx),
 302         .cra_module = THIS_MODULE,
 303         .cra_list = LIST_HEAD_INIT(alg.cra_list),
 304         .cra_init = lzf_compress_init,
 305         .cra_exit = lzf_compress_exit,
 306         .cra_u = { .compress = {
 307         .coa_compress = lzf_compress,
 308         .coa_decompress = lzf_decompress } }
 309 };
 310
 311 static int __init init(void)
 312 {
 313         return crypto_register_alg(&alg);
 314 }
 315
 316 static void __exit fini(void)
 317 {
 318         crypto_unregister_alg(&alg);
 319 }
 320
 321 module_init(init);
 322 module_exit(fini);
 323
 324 MODULE_LICENSE("GPL");
 325 MODULE_DESCRIPTION("LZF Compression Algorithm");
 326 MODULE_AUTHOR("Marc Alexander Lehmann & Nigel Cunningham");