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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 | /* * 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 <Matt_Domsch@dell.com> * 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 <Matt_Domsch@dell.com> * 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 <linux/crc32.h> #include <linux/module.h> #include <linux/types.h> #include <linux/sched.h> #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 <Matt_Domsch@dell.com>"); 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, CRCPOLY_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, CRCPOLY_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, CRCPOLY_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, CRCPOLY_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, CRCPOLY_BE); } #endif EXPORT_SYMBOL(crc32_be); |