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 /* * Aug 8, 2011 Bob Pearson with help from Joakim Tjernlund and George Spelvin * cleaned up code to current version of sparse and added the slicing-by-8 * algorithm to the closely similar existing slicing-by-4 algorithm. * * 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 "crc32defs.h" #if CRC_LE_BITS > 8 # define tole(x) ((__force u32) cpu_to_le32(x)) #else # define tole(x) (x) #endif #if CRC_BE_BITS > 8 # define tobe(x) ((__force u32) cpu_to_be32(x)) #else # define tobe(x) (x) #endif #include "crc32table.h" MODULE_AUTHOR("Matt Domsch "); MODULE_DESCRIPTION("Various CRC32 calculations"); MODULE_LICENSE("GPL"); #if CRC_LE_BITS > 8 || CRC_BE_BITS > 8 /* implements slicing-by-4 or slicing-by-8 algorithm */ static inline u32 __pure 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 (t3[(q) & 255] ^ t2[(q >> 8) & 255] ^ \ t1[(q >> 16) & 255] ^ t0[(q >> 24) & 255]) # define DO_CRC8 (t7[(q) & 255] ^ t6[(q >> 8) & 255] ^ \ t5[(q >> 16) & 255] ^ t4[(q >> 24) & 255]) # else # define DO_CRC(x) crc = t0[((crc >> 24) ^ (x)) & 255] ^ (crc << 8) # define DO_CRC4 (t0[(q) & 255] ^ t1[(q >> 8) & 255] ^ \ t2[(q >> 16) & 255] ^ t3[(q >> 24) & 255]) # define DO_CRC8 (t4[(q) & 255] ^ t5[(q >> 8) & 255] ^ \ t6[(q >> 16) & 255] ^ t7[(q >> 24) & 255]) # endif const u32 *b; size_t rem_len; # ifdef CONFIG_X86 size_t i; # endif const u32 *t0=tab[0], *t1=tab[1], *t2=tab[2], *t3=tab[3]; # if CRC_LE_BITS != 32 const u32 *t4 = tab[4], *t5 = tab[5], *t6 = tab[6], *t7 = tab[7]; # endif u32 q; /* Align it */ if (unlikely((long)buf & 3 && len)) { do { DO_CRC(*buf++); } while ((--len) && ((long)buf)&3); } # if CRC_LE_BITS == 32 rem_len = len & 3; len = len >> 2; # else rem_len = len & 7; len = len >> 3; # endif b = (const u32 *)buf; # ifdef CONFIG_X86 --b; for (i = 0; i < len; i++) { # else for (--b; len; --len) { # endif q = crc ^ *++b; /* use pre increment for speed */ # if CRC_LE_BITS == 32 crc = DO_CRC4; # else crc = DO_CRC8; q = *++b; crc ^= DO_CRC4; # endif } len = rem_len; /* And the last few bytes */ if (len) { u8 *p = (u8 *)(b + 1) - 1; # ifdef CONFIG_X86 for (i = 0; i < len; i++) DO_CRC(*++p); /* use pre increment for speed */ # else do { DO_CRC(*++p); /* use pre increment for speed */ } while (--len); # endif } return crc; #undef DO_CRC #undef DO_CRC4 #undef DO_CRC8 } #endif /** * crc32_le_generic() - Calculate bitwise little-endian Ethernet AUTODIN II * CRC32/CRC32C * @crc: seed value for computation. ~0 for Ethernet, sometimes 0 for other * uses, or the previous crc32/crc32c value if computing incrementally. * @p: pointer to buffer over which CRC32/CRC32C is run * @len: length of buffer @p * @tab: little-endian Ethernet table * @polynomial: CRC32/CRC32c LE polynomial */ static inline u32 __pure crc32_le_generic(u32 crc, unsigned char const *p, size_t len, const u32 (*tab)[256], u32 polynomial) { #if CRC_LE_BITS == 1 int i; while (len--) { crc ^= *p++; for (i = 0; i < 8; i++) crc = (crc >> 1) ^ ((crc & 1) ? polynomial : 0); } # elif CRC_LE_BITS == 2 while (len--) { crc ^= *p++; crc = (crc >> 2) ^ tab[0][crc & 3]; crc = (crc >> 2) ^ tab[0][crc & 3]; crc = (crc >> 2) ^ tab[0][crc & 3]; crc = (crc >> 2) ^ tab[0][crc & 3]; } # elif CRC_LE_BITS == 4 while (len--) { crc ^= *p++; crc = (crc >> 4) ^ tab[0][crc & 15]; crc = (crc >> 4) ^ tab[0][crc & 15]; } # elif CRC_LE_BITS == 8 /* aka Sarwate algorithm */ while (len--) { crc ^= *p++; crc = (crc >> 8) ^ tab[0][crc & 255]; } # else crc = (__force u32) __cpu_to_le32(crc); crc = crc32_body(crc, p, len, tab); crc = __le32_to_cpu((__force __le32)crc); #endif return crc; } #if CRC_LE_BITS == 1 u32 __pure crc32_le(u32 crc, unsigned char const *p, size_t len) { return crc32_le_generic(crc, p, len, NULL, CRC32_POLY_LE); } u32 __pure __crc32c_le(u32 crc, unsigned char const *p, size_t len) { return crc32_le_generic(crc, p, len, NULL, CRC32C_POLY_LE); } #else u32 __pure crc32_le(u32 crc, unsigned char const *p, size_t len) { return crc32_le_generic(crc, p, len, (const u32 (*)[256])crc32table_le, CRC32_POLY_LE); } u32 __pure __crc32c_le(u32 crc, unsigned char const *p, size_t len) { return crc32_le_generic(crc, p, len, (const u32 (*)[256])crc32ctable_le, CRC32C_POLY_LE); } #endif EXPORT_SYMBOL(crc32_le); EXPORT_SYMBOL(__crc32c_le); /* * This multiplies the polynomials x and y modulo the given modulus. * This follows the "little-endian" CRC convention that the lsbit * represents the highest power of x, and the msbit represents x^0. */ static u32 __attribute_const__ gf2_multiply(u32 x, u32 y, u32 modulus) { u32 product = x & 1 ? y : 0; int i; for (i = 0; i < 31; i++) { product = (product >> 1) ^ (product & 1 ? modulus : 0); x >>= 1; product ^= x & 1 ? y : 0; } return product; } /** * crc32_generic_shift - Append @len 0 bytes to crc, in logarithmic time * @crc: The original little-endian CRC (i.e. lsbit is x^31 coefficient) * @len: The number of bytes. @crc is multiplied by x^(8*@len) * @polynomial: The modulus used to reduce the result to 32 bits. * * It's possible to parallelize CRC computations by computing a CRC * over separate ranges of a buffer, then summing them. * This shifts the given CRC by 8*len bits (i.e. produces the same effect * as appending len bytes of zero to the data), in time proportional * to log(len). */ static u32 __attribute_const__ crc32_generic_shift(u32 crc, size_t len, u32 polynomial) { u32 power = polynomial; /* CRC of x^32 */ int i; /* Shift up to 32 bits in the simple linear way */ for (i = 0; i < 8 * (int)(len & 3); i++) crc = (crc >> 1) ^ (crc & 1 ? polynomial : 0); len >>= 2; if (!len) return crc; for (;;) { /* "power" is x^(2^i), modulo the polynomial */ if (len & 1) crc = gf2_multiply(crc, power, polynomial); len >>= 1; if (!len) break; /* Square power, advancing to x^(2^(i+1)) */ power = gf2_multiply(power, power, polynomial); } return crc; } u32 __attribute_const__ crc32_le_shift(u32 crc, size_t len) { return crc32_generic_shift(crc, len, CRC32_POLY_LE); } u32 __attribute_const__ __crc32c_le_shift(u32 crc, size_t len) { return crc32_generic_shift(crc, len, CRC32C_POLY_LE); } EXPORT_SYMBOL(crc32_le_shift); EXPORT_SYMBOL(__crc32c_le_shift); /** * crc32_be_generic() - 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 CRC32 is run * @len: length of buffer @p * @tab: big-endian Ethernet table * @polynomial: CRC32 BE polynomial */ static inline u32 __pure crc32_be_generic(u32 crc, unsigned char const *p, size_t len, const u32 (*tab)[256], u32 polynomial) { #if CRC_BE_BITS == 1 int i; while (len--) { crc ^= *p++ << 24; for (i = 0; i < 8; i++) crc = (crc << 1) ^ ((crc & 0x80000000) ? polynomial : 0); } # elif CRC_BE_BITS == 2 while (len--) { crc ^= *p++ << 24; crc = (crc << 2) ^ tab[0][crc >> 30]; crc = (crc << 2) ^ tab[0][crc >> 30]; crc = (crc << 2) ^ tab[0][crc >> 30]; crc = (crc << 2) ^ tab[0][crc >> 30]; } # elif CRC_BE_BITS == 4 while (len--) { crc ^= *p++ << 24; crc = (crc << 4) ^ tab[0][crc >> 28]; crc = (crc << 4) ^ tab[0][crc >> 28]; } # elif CRC_BE_BITS == 8 while (len--) { crc ^= *p++ << 24; crc = (crc << 8) ^ tab[0][crc >> 24]; } # else crc = (__force u32) __cpu_to_be32(crc); crc = crc32_body(crc, p, len, tab); crc = __be32_to_cpu((__force __be32)crc); # endif return crc; } #if CRC_LE_BITS == 1 u32 __pure crc32_be(u32 crc, unsigned char const *p, size_t len) { return crc32_be_generic(crc, p, len, NULL, CRC32_POLY_BE); } #else u32 __pure crc32_be(u32 crc, unsigned char const *p, size_t len) { return crc32_be_generic(crc, p, len, (const u32 (*)[256])crc32table_be, CRC32_POLY_BE); } #endif EXPORT_SYMBOL(crc32_be);