lib/crc32.c

   1 /*
   2  * July 20, 2011 Bob Pearson <rpearson at systemfabricworks.com>
   3  * added slice by 8 algorithm to the existing conventional and
   4  * slice by 4 algorithms.
   5  *
   6  * Oct 15, 2000 Matt Domsch <Matt_Domsch@dell.com>
   7  * Nicer crc32 functions/docs submitted by linux@horizon.com.  Thanks!
   8  * Code was from the public domain, copyright abandoned.  Code was
   9  * subsequently included in the kernel, thus was re-licensed under the
  10  * GNU GPL v2.
  11  *
  12  * Oct 12, 2000 Matt Domsch <Matt_Domsch@dell.com>
  13  * Same crc32 function was used in 5 other places in the kernel.
  14  * I made one version, and deleted the others.
  15  * There are various incantations of crc32().  Some use a seed of 0 or ~0.
  16  * Some xor at the end with ~0.  The generic crc32() function takes
  17  * seed as an argument, and doesn't xor at the end.  Then individual
  18  * users can do whatever they need.
  19  *   drivers/net/smc9194.c uses seed ~0, doesn't xor with ~0.
  20  *   fs/jffs2 uses seed 0, doesn't xor with ~0.
  21  *   fs/partitions/efi.c uses seed ~0, xor's with ~0.
  22  *
  23  * This source code is licensed under the GNU General Public License,
  24  * Version 2.  See the file COPYING for more details.
  25  */
  26 #include <linux/crc32.h>
  27 #include <linux/kernel.h>
  28 #include <linux/module.h>
  29 #include <linux/compiler.h>
  30 #include <linux/types.h>
  31 #include <linux/init.h>
  32 #include <linux/atomic.h>
  33 #include "crc32defs.h"
  34
  35 #if CRC_LE_BITS > 8
  36 # define tole(x) (__force u32) __constant_cpu_to_le32(x)
  37 #else
  38 # define tole(x) (x)
  39 #endif
  40
  41 #if CRC_BE_BITS > 8
  42 # define tobe(x) (__force u32) __constant_cpu_to_be32(x)
  43 #else
  44 # define tobe(x) (x)
  45 #endif
  46 #include "crc32table.h"
  47
  48 MODULE_AUTHOR("Matt Domsch <Matt_Domsch@dell.com>");
  49 MODULE_DESCRIPTION("Ethernet CRC32 calculations");
  50 MODULE_LICENSE("GPL");
  51
  52 #if CRC_LE_BITS > 8
  53 static inline u32 crc32_le_body(u32 crc, u8 const *buf, size_t len)
  54 {
  55         const u8 *p8;
  56         const u32 *p32;
  57         int init_bytes, end_bytes;
  58         size_t words;
  59         int i;
  60         u32 q;
  61         u8 i0, i1, i2, i3;
  62
  63         crc = (__force u32) __cpu_to_le32(crc);
  64
  65 #if CRC_LE_BITS == 64
  66         p8 = buf;
  67         p32 = (u32 *)(((uintptr_t)p8 + 7) & ~7);
  68
  69         init_bytes = (uintptr_t)p32 - (uintptr_t)p8;
  70         if (init_bytes > len)
  71                 init_bytes = len;
  72         words = (len - init_bytes) >> 3;
  73         end_bytes = (len - init_bytes) & 7;
  74 #else
  75         p8 = buf;
  76         p32 = (u32 *)(((uintptr_t)p8 + 3) & ~3);
  77
  78         init_bytes = (uintptr_t)p32 - (uintptr_t)p8;
  79         if (init_bytes > len)
  80                 init_bytes = len;
  81         words = (len - init_bytes) >> 2;
  82         end_bytes = (len - init_bytes) & 3;
  83 #endif
  84
  85         for (i = 0; i < init_bytes; i++) {
  86 #ifdef __LITTLE_ENDIAN
  87                 i0 = *p8++ ^ crc;
  88                 crc = t0_le[i0] ^ (crc >> 8);
  89 #else
  90                 i0 = *p8++ ^ (crc >> 24);
  91                 crc = t0_le[i0] ^ (crc << 8);
  92 #endif
  93         }
  94
  95         for (i = 0; i < words; i++) {
  96 #ifdef __LITTLE_ENDIAN
  97 #  if CRC_LE_BITS == 64
  98                 /* slice by 8 algorithm */
  99                 q = *p32++ ^ crc;
 100                 i3 = q;
 101                 i2 = q >> 8;
 102                 i1 = q >> 16;
 103                 i0 = q >> 24;
 104                 crc = t7_le[i3] ^ t6_le[i2] ^ t5_le[i1] ^ t4_le[i0];
 105
 106                 q = *p32++;
 107                 i3 = q;
 108                 i2 = q >> 8;
 109                 i1 = q >> 16;
 110                 i0 = q >> 24;
 111                 crc ^= t3_le[i3] ^ t2_le[i2] ^ t1_le[i1] ^ t0_le[i0];
 112 #  else
 113                 /* slice by 4 algorithm */
 114                 q = *p32++ ^ crc;
 115                 i3 = q;
 116                 i2 = q >> 8;
 117                 i1 = q >> 16;
 118                 i0 = q >> 24;
 119                 crc = t3_le[i3] ^ t2_le[i2] ^ t1_le[i1] ^ t0_le[i0];
 120 #  endif
 121 #else
 122 #  if CRC_LE_BITS == 64
 123                 q = *p32++ ^ crc;
 124                 i3 = q >> 24;
 125                 i2 = q >> 16;
 126                 i1 = q >> 8;
 127                 i0 = q;
 128                 crc = t7_le[i3] ^ t6_le[i2] ^ t5_le[i1] ^ t4_le[i0];
 129
 130                 q = *p32++;
 131                 i3 = q >> 24;
 132                 i2 = q >> 16;
 133                 i1 = q >> 8;
 134                 i0 = q;
 135                 crc ^= t3_le[i3] ^ t2_le[i2] ^ t1_le[i1] ^ t0_le[i0];
 136 #  else
 137                 q = *p32++ ^ crc;
 138                 i3 = q >> 24;
 139                 i2 = q >> 16;
 140                 i1 = q >> 8;
 141                 i0 = q;
 142                 crc = t3_le[i3] ^ t2_le[i2] ^ t1_le[i1] ^ t0_le[i0];
 143 #  endif
 144 #endif
 145         }
 146
 147         p8 = (u8 *)p32;
 148
 149         for (i = 0; i < end_bytes; i++) {
 150 #ifdef __LITTLE_ENDIAN
 151                 i0 = *p8++ ^ crc;
 152                 crc = t0_le[i0] ^ (crc >> 8);
 153 #else
 154                 i0 = *p8++ ^ (crc >> 24);
 155                 crc = t0_le[i0] ^ (crc << 8);
 156 #endif
 157         }
 158
 159         return __le32_to_cpu((__force __le32)crc);
 160 }
 161 #endif
 162
 163 #if CRC_BE_BITS > 8
 164 static inline u32 crc32_be_body(u32 crc, u8 const *buf, size_t len)
 165 {
 166         const u8 *p8;
 167         const u32 *p32;
 168         int init_bytes, end_bytes;
 169         size_t words;
 170         int i;
 171         u32 q;
 172         u8 i0, i1, i2, i3;
 173
 174         crc = (__force u32) __cpu_to_be32(crc);
 175
 176 #if CRC_LE_BITS == 64
 177         p8 = buf;
 178         p32 = (u32 *)(((uintptr_t)p8 + 7) & ~7);
 179
 180         init_bytes = (uintptr_t)p32 - (uintptr_t)p8;
 181         if (init_bytes > len)
 182                 init_bytes = len;
 183         words = (len - init_bytes) >> 3;
 184         end_bytes = (len - init_bytes) & 7;
 185 #else
 186         p8 = buf;
 187         p32 = (u32 *)(((uintptr_t)p8 + 3) & ~3);
 188
 189         init_bytes = (uintptr_t)p32 - (uintptr_t)p8;
 190         if (init_bytes > len)
 191                 init_bytes = len;
 192         words = (len - init_bytes) >> 2;
 193         end_bytes = (len - init_bytes) & 3;
 194 #endif
 195
 196         for (i = 0; i < init_bytes; i++) {
 197 #ifdef __LITTLE_ENDIAN
 198                 i0 = *p8++ ^ crc;
 199                 crc = t0_be[i0] ^ (crc >> 8);
 200 #else
 201                 i0 = *p8++ ^ (crc >> 24);
 202                 crc = t0_be[i0] ^ (crc << 8);
 203 #endif
 204         }
 205
 206         for (i = 0; i < words; i++) {
 207 #ifdef __LITTLE_ENDIAN
 208 #  if CRC_LE_BITS == 64
 209                 /* slice by 8 algorithm */
 210                 q = *p32++ ^ crc;
 211                 i3 = q;
 212                 i2 = q >> 8;
 213                 i1 = q >> 16;
 214                 i0 = q >> 24;
 215                 crc = t7_be[i3] ^ t6_be[i2] ^ t5_be[i1] ^ t4_be[i0];
 216
 217                 q = *p32++;
 218                 i3 = q;
 219                 i2 = q >> 8;
 220                 i1 = q >> 16;
 221                 i0 = q >> 24;
 222                 crc ^= t3_be[i3] ^ t2_be[i2] ^ t1_be[i1] ^ t0_be[i0];
 223 #  else
 224                 /* slice by 4 algorithm */
 225                 q = *p32++ ^ crc;
 226                 i3 = q;
 227                 i2 = q >> 8;
 228                 i1 = q >> 16;
 229                 i0 = q >> 24;
 230                 crc = t3_be[i3] ^ t2_be[i2] ^ t1_be[i1] ^ t0_be[i0];
 231 #  endif
 232 #else
 233 #  if CRC_LE_BITS == 64
 234                 q = *p32++ ^ crc;
 235                 i3 = q >> 24;
 236                 i2 = q >> 16;
 237                 i1 = q >> 8;
 238                 i0 = q;
 239                 crc = t7_be[i3] ^ t6_be[i2] ^ t5_be[i1] ^ t4_be[i0];
 240
 241                 q = *p32++;
 242                 i3 = q >> 24;
 243                 i2 = q >> 16;
 244                 i1 = q >> 8;
 245                 i0 = q;
 246                 crc ^= t3_be[i3] ^ t2_be[i2] ^ t1_be[i1] ^ t0_be[i0];
 247 #  else
 248                 q = *p32++ ^ crc;
 249                 i3 = q >> 24;
 250                 i2 = q >> 16;
 251                 i1 = q >> 8;
 252                 i0 = q;
 253                 crc = t3_be[i3] ^ t2_be[i2] ^ t1_be[i1] ^ t0_be[i0];
 254 #  endif
 255 #endif
 256         }
 257
 258         p8 = (u8 *)p32;
 259
 260         for (i = 0; i < end_bytes; i++) {
 261 #ifdef __LITTLE_ENDIAN
 262                 i0 = *p8++ ^ crc;
 263                 crc = t0_be[i0] ^ (crc >> 8);
 264 #else
 265                 i0 = *p8++ ^ (crc >> 24);
 266                 crc = t0_be[i0] ^ (crc << 8);
 267 #endif
 268         }
 269
 270         return __be32_to_cpu((__force __be32)crc);
 271 }
 272 #endif
 273
 274 /**
 275  * crc32_le() - Calculate bitwise little-endian Ethernet AUTODIN II CRC32
 276  * @crc: seed value for computation.  ~0 for Ethernet, sometimes 0 for
 277  *      other uses, or the previous crc32 value if computing incrementally.
 278  * @p: pointer to buffer over which CRC is run
 279  * @len: length of buffer @p
 280  */
 281 u32 __pure crc32_le(u32 crc, unsigned char const *p, size_t len)
 282 {
 283 #if CRC_LE_BITS == 1
 284         int i;
 285         while (len--) {
 286                 crc ^= *p++;
 287                 for (i = 0; i < 8; i++)
 288                         crc = (crc >> 1) ^ ((crc & 1) ? CRCPOLY_LE : 0);
 289         }
 290 # elif CRC_LE_BITS == 2
 291         while (len--) {
 292                 crc ^= *p++;
 293                 crc = (crc >> 2) ^ t0_le[crc & 0x03];
 294                 crc = (crc >> 2) ^ t0_le[crc & 0x03];
 295                 crc = (crc >> 2) ^ t0_le[crc & 0x03];
 296                 crc = (crc >> 2) ^ t0_le[crc & 0x03];
 297         }
 298 # elif CRC_LE_BITS == 4
 299         while (len--) {
 300                 crc ^= *p++;
 301                 crc = (crc >> 4) ^ t0_le[crc & 0x0f];
 302                 crc = (crc >> 4) ^ t0_le[crc & 0x0f];
 303         }
 304 # elif CRC_LE_BITS == 8
 305         while (len--) {
 306                 crc ^= *p++;
 307                 crc = (crc >> 8) ^ t0_le[crc & 0xff];
 308         }
 309 # else
 310         crc = crc32_le_body(crc, p, len);
 311 # endif
 312         return crc;
 313 }
 314 EXPORT_SYMBOL(crc32_le);
 315
 316 /**
 317  * crc32_be() - Calculate bitwise big-endian Ethernet AUTODIN II CRC32
 318  * @crc: seed value for computation.  ~0 for Ethernet, sometimes 0 for
 319  *      other uses, or the previous crc32 value if computing incrementally.
 320  * @p: pointer to buffer over which CRC is run
 321  * @len: length of buffer @p
 322  */
 323 u32 __pure crc32_be(u32 crc, unsigned char const *p, size_t len)
 324 {
 325 #if CRC_BE_BITS == 1
 326         int i;
 327         while (len--) {
 328                 crc ^= *p++ << 24;
 329                 for (i = 0; i < 8; i++)
 330                         crc = (crc << 1) ^
 331                               ((crc & 0x80000000) ? CRCPOLY_BE : 0);
 332         }
 333 # elif CRC_BE_BITS == 2
 334         while (len--) {
 335                 crc ^= *p++ << 24;
 336                 crc = (crc << 2) ^ t0_be[crc >> 30];
 337                 crc = (crc << 2) ^ t0_be[crc >> 30];
 338                 crc = (crc << 2) ^ t0_be[crc >> 30];
 339                 crc = (crc << 2) ^ t0_be[crc >> 30];
 340         }
 341 # elif CRC_BE_BITS == 4
 342         while (len--) {
 343                 crc ^= *p++ << 24;
 344                 crc = (crc << 4) ^ t0_be[crc >> 28];
 345                 crc = (crc << 4) ^ t0_be[crc >> 28];
 346         }
 347 # elif CRC_BE_BITS == 8
 348         while (len--) {
 349                 crc ^= *p++ << 24;
 350                 crc = (crc << 8) ^ t0_be[crc >> 24];
 351         }
 352 # else
 353         crc = crc32_be_body(crc, p, len);
 354 # endif
 355         return crc;
 356 }
 357 EXPORT_SYMBOL(crc32_be);
 358
 359 /*
 360  * A brief CRC tutorial.
 361  *
 362  * A CRC is a long-division remainder.  You add the CRC to the message,
 363  * and the whole thing (message+CRC) is a multiple of the given
 364  * CRC polynomial.  To check the CRC, you can either check that the
 365  * CRC matches the recomputed value, *or* you can check that the
 366  * remainder computed on the message+CRC is 0.  This latter approach
 367  * is used by a lot of hardware implementations, and is why so many
 368  * protocols put the end-of-frame flag after the CRC.
 369  *
 370  * It's actually the same long division you learned in school, except that
 371  * - We're working in binary, so the digits are only 0 and 1, and
 372  * - When dividing polynomials, there are no carries.  Rather than add and
 373  *   subtract, we just xor.  Thus, we tend to get a bit sloppy about
 374  *   the difference between adding and subtracting.
 375  *
 376  * A 32-bit CRC polynomial is actually 33 bits long.  But since it's
 377  * 33 bits long, bit 32 is always going to be set, so usually the CRC
 378  * is written in hex with the most significant bit omitted.  (If you're
 379  * familiar with the IEEE 754 floating-point format, it's the same idea.)
 380  *
 381  * Note that a CRC is computed over a string of *bits*, so you have
 382  * to decide on the endianness of the bits within each byte.  To get
 383  * the best error-detecting properties, this should correspond to the
 384  * order they're actually sent.  For example, standard RS-232 serial is
 385  * little-endian; the most significant bit (sometimes used for parity)
 386  * is sent last.  And when appending a CRC word to a message, you should
 387  * do it in the right order, matching the endianness.
 388  *
 389  * Just like with ordinary division, the remainder is always smaller than
 390  * the divisor (the CRC polynomial) you're dividing by.  Each step of the
 391  * division, you take one more digit (bit) of the dividend and append it
 392  * to the current remainder.  Then you figure out the appropriate multiple
 393  * of the divisor to subtract to being the remainder back into range.
 394  * In binary, it's easy - it has to be either 0 or 1, and to make the
 395  * XOR cancel, it's just a copy of bit 32 of the remainder.
 396  *
 397  * When computing a CRC, we don't care about the quotient, so we can
 398  * throw the quotient bit away, but subtract the appropriate multiple of
 399  * the polynomial from the remainder and we're back to where we started,
 400  * ready to process the next bit.
 401  *
 402  * A big-endian CRC written this way would be coded like:
 403  * for (i = 0; i < input_bits; i++) {
 404  *      multiple = remainder & 0x80000000 ? CRCPOLY : 0;
 405  *      remainder = (remainder << 1 | next_input_bit()) ^ multiple;
 406  * }
 407  * Notice how, to get at bit 32 of the shifted remainder, we look
 408  * at bit 31 of the remainder *before* shifting it.
 409  *
 410  * But also notice how the next_input_bit() bits we're shifting into
 411  * the remainder don't actually affect any decision-making until
 412  * 32 bits later.  Thus, the first 32 cycles of this are pretty boring.
 413  * Also, to add the CRC to a message, we need a 32-bit-long hole for it at
 414  * the end, so we have to add 32 extra cycles shifting in zeros at the
 415  * end of every message,
 416  *
 417  * So the standard trick is to rearrage merging in the next_input_bit()
 418  * until the moment it's needed.  Then the first 32 cycles can be precomputed,
 419  * and merging in the final 32 zero bits to make room for the CRC can be
 420  * skipped entirely.
 421  * This changes the code to:
 422  * for (i = 0; i < input_bits; i++) {
 423  *      remainder ^= next_input_bit() << 31;
 424  *      multiple = (remainder & 0x80000000) ? CRCPOLY : 0;
 425  *      remainder = (remainder << 1) ^ multiple;
 426  * }
 427  * With this optimization, the little-endian code is simpler:
 428  * for (i = 0; i < input_bits; i++) {
 429  *      remainder ^= next_input_bit();
 430  *      multiple = (remainder & 1) ? CRCPOLY : 0;
 431  *      remainder = (remainder >> 1) ^ multiple;
 432  * }
 433  *
 434  * Note that the other details of endianness have been hidden in CRCPOLY
 435  * (which must be bit-reversed) and next_input_bit().
 436  *
 437  * However, as long as next_input_bit is returning the bits in a sensible
 438  * order, we can actually do the merging 8 or more bits at a time rather
 439  * than one bit at a time:
 440  * for (i = 0; i < input_bytes; i++) {
 441  *      remainder ^= next_input_byte() << 24;
 442  *      for (j = 0; j < 8; j++) {
 443  *              multiple = (remainder & 0x80000000) ? CRCPOLY : 0;
 444  *              remainder = (remainder << 1) ^ multiple;
 445  *      }
 446  * }
 447  * Or in little-endian:
 448  * for (i = 0; i < input_bytes; i++) {
 449  *      remainder ^= next_input_byte();
 450  *      for (j = 0; j < 8; j++) {
 451  *              multiple = (remainder & 1) ? CRCPOLY : 0;
 452  *              remainder = (remainder << 1) ^ multiple;
 453  *      }
 454  * }
 455  * If the input is a multiple of 32 bits, you can even XOR in a 32-bit
 456  * word at a time and increase the inner loop count to 32.
 457  *
 458  * You can also mix and match the two loop styles, for example doing the
 459  * bulk of a message byte-at-a-time and adding bit-at-a-time processing
 460  * for any fractional bytes at the end.
 461  *
 462  * The only remaining optimization is to the byte-at-a-time table method.
 463  * Here, rather than just shifting one bit of the remainder to decide
 464  * in the correct multiple to subtract, we can shift a byte at a time.
 465  * This produces a 40-bit (rather than a 33-bit) intermediate remainder,
 466  * but again the multiple of the polynomial to subtract depends only on
 467  * the high bits, the high 8 bits in this case.
 468  *
 469  * The multiple we need in that case is the low 32 bits of a 40-bit
 470  * value whose high 8 bits are given, and which is a multiple of the
 471  * generator polynomial.  This is simply the CRC-32 of the given
 472  * one-byte message.
 473  *
 474  * Two more details: normally, appending zero bits to a message which
 475  * is already a multiple of a polynomial produces a larger multiple of that
 476  * polynomial.  To enable a CRC to detect this condition, it's common to
 477  * invert the CRC before appending it.  This makes the remainder of the
 478  * message+crc come out not as zero, but some fixed non-zero value.
 479  *
 480  * The same problem applies to zero bits prepended to the message, and
 481  * a similar solution is used.  Instead of starting with a remainder of
 482  * 0, an initial remainder of all ones is used.  As long as you start
 483  * the same way on decoding, it doesn't make a difference.
 484  */
 485
 486 #ifdef UNITTEST
 487
 488 #include <stdlib.h>
 489 #include <stdio.h>
 490
 491 #if 0                           /*Not used at present */
 492 static void
 493 buf_dump(char const *prefix, unsigned char const *buf, size_t len)
 494 {
 495         fputs(prefix, stdout);
 496         while (len--)
 497                 printf(" %02x", *buf++);
 498         putchar('\n');
 499
 500 }
 501 #endif
 502
 503 static void bytereverse(unsigned char *buf, size_t len)
 504 {
 505         while (len--) {
 506                 unsigned char x = bitrev8(*buf);
 507                 *buf++ = x;
 508         }
 509 }
 510
 511 static void random_garbage(unsigned char *buf, size_t len)
 512 {
 513         while (len--)
 514                 *buf++ = (unsigned char) random();
 515 }
 516
 517 #if 0                           /* Not used at present */
 518 static void store_le(u32 x, unsigned char *buf)
 519 {
 520         buf[0] = (unsigned char) x;
 521         buf[1] = (unsigned char) (x >> 8);
 522         buf[2] = (unsigned char) (x >> 16);
 523         buf[3] = (unsigned char) (x >> 24);
 524 }
 525 #endif
 526
 527 static void store_be(u32 x, unsigned char *buf)
 528 {
 529         buf[0] = (unsigned char) (x >> 24);
 530         buf[1] = (unsigned char) (x >> 16);
 531         buf[2] = (unsigned char) (x >> 8);
 532         buf[3] = (unsigned char) x;
 533 }
 534
 535 /*
 536  * This checks that CRC(buf + CRC(buf)) = 0, and that
 537  * CRC commutes with bit-reversal.  This has the side effect
 538  * of bytewise bit-reversing the input buffer, and returns
 539  * the CRC of the reversed buffer.
 540  */
 541 static u32 test_step(u32 init, unsigned char *buf, size_t len)
 542 {
 543         u32 crc1, crc2;
 544         size_t i;
 545
 546         crc1 = crc32_be(init, buf, len);
 547         store_be(crc1, buf + len);
 548         crc2 = crc32_be(init, buf, len + 4);
 549         if (crc2)
 550                 printf("\nCRC cancellation fail: 0x%08x should be 0\n",
 551                        crc2);
 552
 553         for (i = 0; i <= len + 4; i++) {
 554                 crc2 = crc32_be(init, buf, i);
 555                 crc2 = crc32_be(crc2, buf + i, len + 4 - i);
 556                 if (crc2)
 557                         printf("\nCRC split fail: 0x%08x\n", crc2);
 558         }
 559
 560         /* Now swap it around for the other test */
 561
 562         bytereverse(buf, len + 4);
 563         init = bitrev32(init);
 564         crc2 = bitrev32(crc1);
 565         if (crc1 != bitrev32(crc2))
 566                 printf("\nBit reversal fail: 0x%08x -> 0x%08x -> 0x%08x\n",
 567                        crc1, crc2, bitrev32(crc2));
 568         crc1 = crc32_le(init, buf, len);
 569         if (crc1 != crc2)
 570                 printf("\nCRC endianness fail: 0x%08x != 0x%08x\n", crc1,
 571                        crc2);
 572         crc2 = crc32_le(init, buf, len + 4);
 573         if (crc2)
 574                 printf("\nCRC cancellation fail: 0x%08x should be 0\n",
 575                        crc2);
 576
 577         for (i = 0; i <= len + 4; i++) {
 578                 crc2 = crc32_le(init, buf, i);
 579                 crc2 = crc32_le(crc2, buf + i, len + 4 - i);
 580                 if (crc2)
 581                         printf("\nCRC split fail: 0x%08x\n", crc2);
 582         }
 583
 584         return crc1;
 585 }
 586
 587 #define SIZE 64
 588 #define INIT1 0
 589 #define INIT2 0
 590
 591 int main(void)
 592 {
 593         unsigned char buf1[SIZE + 4];
 594         unsigned char buf2[SIZE + 4];
 595         unsigned char buf3[SIZE + 4];
 596         int i, j;
 597         u32 crc1, crc2, crc3;
 598
 599         for (i = 0; i <= SIZE; i++) {
 600                 printf("\rTesting length %d...", i);
 601                 fflush(stdout);
 602                 random_garbage(buf1, i);
 603                 random_garbage(buf2, i);
 604                 for (j = 0; j < i; j++)
 605                         buf3[j] = buf1[j] ^ buf2[j];
 606
 607                 crc1 = test_step(INIT1, buf1, i);
 608                 crc2 = test_step(INIT2, buf2, i);
 609                 /* Now check that CRC(buf1 ^ buf2) = CRC(buf1) ^ CRC(buf2) */
 610                 crc3 = test_step(INIT1 ^ INIT2, buf3, i);
 611                 if (crc3 != (crc1 ^ crc2))
 612                         printf("CRC XOR fail: 0x%08x != 0x%08x ^ 0x%08x\n",
 613                                crc3, crc1, crc2);
 614         }
 615         printf("\nAll test complete.  No failures expected.\n");
 616         return 0;
 617 }
 618
 619 #endif                          /* UNITTEST */