/* * Oct 15, 2000 Matt Domsch * Nicer crc32 functions/docs submitted by linux@horizon.com. Thanks! * Code was from the public domain, copyright abandoned. Code was * subsequently included in the kernel, thus was re-licensed under the * GNU GPL v2. * * Oct 12, 2000 Matt Domsch * Same crc32 function was used in 5 other places in the kernel. * I made one version, and deleted the others. * There are various incantations of crc32(). Some use a seed of 0 or ~0. * Some xor at the end with ~0. The generic crc32() function takes * seed as an argument, and doesn't xor at the end. Then individual * users can do whatever they need. * drivers/net/smc9194.c uses seed ~0, doesn't xor with ~0. * fs/jffs2 uses seed 0, doesn't xor with ~0. * fs/partitions/efi.c uses seed ~0, xor's with ~0. * * This source code is licensed under the GNU General Public License, * Version 2. See the file COPYING for more details. */ /* see: Documentation/crc32.txt for a description of algorithms */ #include #include #include #include #include #include #include #include "crc32defs.h" #if CRC_LE_BITS == 8 # define tole(x) __constant_cpu_to_le32(x) #else # define tole(x) (x) #endif #if CRC_BE_BITS == 8 # define tobe(x) __constant_cpu_to_be32(x) #else # define tobe(x) (x) #endif #include "crc32table.h" MODULE_AUTHOR("Matt Domsch "); MODULE_DESCRIPTION("Ethernet CRC32 calculations"); MODULE_LICENSE("GPL"); #if CRC_LE_BITS == 8 || CRC_BE_BITS == 8 static inline u32 crc32_body(u32 crc, unsigned char const *buf, size_t len, const u32 (*tab)[256]) { # ifdef __LITTLE_ENDIAN # define DO_CRC(x) crc = t0[(crc ^ (x)) & 255] ^ (crc >> 8) # define DO_CRC4 crc = t3[(crc) & 255] ^ \ t2[(crc >> 8) & 255] ^ \ t1[(crc >> 16) & 255] ^ \ t0[(crc >> 24) & 255] # else # define DO_CRC(x) crc = t0[((crc >> 24) ^ (x)) & 255] ^ (crc << 8) # define DO_CRC4 crc = t0[(crc) & 255] ^ \ t1[(crc >> 8) & 255] ^ \ t2[(crc >> 16) & 255] ^ \ t3[(crc >> 24) & 255] # endif const u32 *b; size_t rem_len; const u32 *t0=tab[0], *t1=tab[1], *t2=tab[2], *t3=tab[3]; /* Align it */ if (unlikely((long)buf & 3 && len)) { do { DO_CRC(*buf++); } while ((--len) && ((long)buf)&3); } rem_len = len & 3; /* load data 32 bits wide, xor data 32 bits wide. */ len = len >> 2; b = (const u32 *)buf; for (--b; len; --len) { crc ^= *++b; /* use pre increment for speed */ DO_CRC4; } len = rem_len; /* And the last few bytes */ if (len) { u8 *p = (u8 *)(b + 1) - 1; do { DO_CRC(*++p); /* use pre increment for speed */ } while (--len); } return crc; #undef DO_CRC #undef DO_CRC4 } #endif /** * crc32_le() - Calculate bitwise little-endian Ethernet AUTODIN II CRC32 * @crc: seed value for computation. ~0 for Ethernet, sometimes 0 for * other uses, or the previous crc32 value if computing incrementally. * @p: pointer to buffer over which CRC is run * @len: length of buffer @p */ u32 __pure crc32_le(u32 crc, unsigned char const *p, size_t len); #if CRC_LE_BITS == 1 /* * In fact, the table-based code will work in this case, but it can be * simplified by inlining the table in ?: form. */ u32 __pure crc32_le(u32 crc, unsigned char const *p, size_t len) { int i; while (len--) { crc ^= *p++; for (i = 0; i < 8; i++) crc = (crc >> 1) ^ ((crc & 1) ? CRCPOLY_LE : 0); } return crc; } #else /* Table-based approach */ u32 __pure crc32_le(u32 crc, unsigned char const *p, size_t len) { # if CRC_LE_BITS == 8 const u32 (*tab)[] = crc32table_le; crc = __cpu_to_le32(crc); crc = crc32_body(crc, p, len, tab); return __le32_to_cpu(crc); # elif CRC_LE_BITS == 4 while (len--) { crc ^= *p++; crc = (crc >> 4) ^ crc32table_le[crc & 15]; crc = (crc >> 4) ^ crc32table_le[crc & 15]; } return crc; # elif CRC_LE_BITS == 2 while (len--) { crc ^= *p++; crc = (crc >> 2) ^ crc32table_le[crc & 3]; crc = (crc >> 2) ^ crc32table_le[crc & 3]; crc = (crc >> 2) ^ crc32table_le[crc & 3]; crc = (crc >> 2) ^ crc32table_le[crc & 3]; } return crc; # endif } #endif /** * crc32_be() - Calculate bitwise big-endian Ethernet AUTODIN II CRC32 * @crc: seed value for computation. ~0 for Ethernet, sometimes 0 for * other uses, or the previous crc32 value if computing incrementally. * @p: pointer to buffer over which CRC is run * @len: length of buffer @p */ u32 __pure crc32_be(u32 crc, unsigned char const *p, size_t len); #if CRC_BE_BITS == 1 /* * In fact, the table-based code will work in this case, but it can be * simplified by inlining the table in ?: form. */ u32 __pure crc32_be(u32 crc, unsigned char const *p, size_t len) { int i; while (len--) { crc ^= *p++ << 24; for (i = 0; i < 8; i++) crc = (crc << 1) ^ ((crc & 0x80000000) ? CRCPOLY_BE : 0); } return crc; } #else /* Table-based approach */ u32 __pure crc32_be(u32 crc, unsigned char const *p, size_t len) { # if CRC_BE_BITS == 8 const u32 (*tab)[] = crc32table_be; crc = __cpu_to_be32(crc); crc = crc32_body(crc, p, len, tab); return __be32_to_cpu(crc); # elif CRC_BE_BITS == 4 while (len--) { crc ^= *p++ << 24; crc = (crc << 4) ^ crc32table_be[crc >> 28]; crc = (crc << 4) ^ crc32table_be[crc >> 28]; } return crc; # elif CRC_BE_BITS == 2 while (len--) { crc ^= *p++ << 24; crc = (crc << 2) ^ crc32table_be[crc >> 30]; crc = (crc << 2) ^ crc32table_be[crc >> 30]; crc = (crc << 2) ^ crc32table_be[crc >> 30]; crc = (crc << 2) ^ crc32table_be[crc >> 30]; } return crc; # endif } #endif EXPORT_SYMBOL(crc32_le); EXPORT_SYMBOL(crc32_be); #ifdef UNITTEST #include #include #if 0 /*Not used at present */ static void buf_dump(char const *prefix, unsigned char const *buf, size_t len) { fputs(prefix, stdout); while (len--) printf(" %02x", *buf++); putchar('\n'); } #endif static void bytereverse(unsigned char *buf, size_t len) { while (len--) { unsigned char x = bitrev8(*buf); *buf++ = x; } } static void random_garbage(unsigned char *buf, size_t len) { while (len--) *buf++ = (unsigned char) random(); } #if 0 /* Not used at present */ static void store_le(u32 x, unsigned char *buf) { buf[0] = (unsigned char) x; buf[1] = (unsigned char) (x >> 8); buf[2] = (unsigned char) (x >> 16); buf[3] = (unsigned char) (x >> 24); } #endif static void store_be(u32 x, unsigned char *buf) { buf[0] = (unsigned char) (x >> 24); buf[1] = (unsigned char) (x >> 16); buf[2] = (unsigned char) (x >> 8); buf[3] = (unsigned char) x; } /* * This checks that CRC(buf + CRC(buf)) = 0, and that * CRC commutes with bit-reversal. This has the side effect * of bytewise bit-reversing the input buffer, and returns * the CRC of the reversed buffer. */ static u32 test_step(u32 init, unsigned char *buf, size_t len) { u32 crc1, crc2; size_t i; crc1 = crc32_be(init, buf, len); store_be(crc1, buf + len); crc2 = crc32_be(init, buf, len + 4); if (crc2) printf("\nCRC cancellation fail: 0x%08x should be 0\n", crc2); for (i = 0; i <= len + 4; i++) { crc2 = crc32_be(init, buf, i); crc2 = crc32_be(crc2, buf + i, len + 4 - i); if (crc2) printf("\nCRC split fail: 0x%08x\n", crc2); } /* Now swap it around for the other test */ bytereverse(buf, len + 4); init = bitrev32(init); crc2 = bitrev32(crc1); if (crc1 != bitrev32(crc2)) printf("\nBit reversal fail: 0x%08x -> 0x%08x -> 0x%08x\n", crc1, crc2, bitrev32(crc2)); crc1 = crc32_le(init, buf, len); if (crc1 != crc2) printf("\nCRC endianness fail: 0x%08x != 0x%08x\n", crc1, crc2); crc2 = crc32_le(init, buf, len + 4); if (crc2) printf("\nCRC cancellation fail: 0x%08x should be 0\n", crc2); for (i = 0; i <= len + 4; i++) { crc2 = crc32_le(init, buf, i); crc2 = crc32_le(crc2, buf + i, len + 4 - i); if (crc2) printf("\nCRC split fail: 0x%08x\n", crc2); } return crc1; } #define SIZE 64 #define INIT1 0 #define INIT2 0 int main(void) { unsigned char buf1[SIZE + 4]; unsigned char buf2[SIZE + 4]; unsigned char buf3[SIZE + 4]; int i, j; u32 crc1, crc2, crc3; for (i = 0; i <= SIZE; i++) { printf("\rTesting length %d...", i); fflush(stdout); random_garbage(buf1, i); random_garbage(buf2, i); for (j = 0; j < i; j++) buf3[j] = buf1[j] ^ buf2[j]; crc1 = test_step(INIT1, buf1, i); crc2 = test_step(INIT2, buf2, i); /* Now check that CRC(buf1 ^ buf2) = CRC(buf1) ^ CRC(buf2) */ crc3 = test_step(INIT1 ^ INIT2, buf3, i); if (crc3 != (crc1 ^ crc2)) printf("CRC XOR fail: 0x%08x != 0x%08x ^ 0x%08x\n", crc3, crc1, crc2); } printf("\nAll test complete. No failures expected.\n"); return 0; } #endif /* UNITTEST */