1 /* 2 * Aug 8, 2011 Bob Pearson with help from Joakim Tjernlund and George Spelvin 3 * cleaned up code to current version of sparse and added the slicing-by-8 4 * algorithm to the closely similar existing slicing-by-4 algorithm. 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 27 /* see: Documentation/crc32.txt for a description of algorithms */ 28 29 #include <linux/crc32.h> 30 #include <linux/crc32poly.h> 31 #include <linux/module.h> 32 #include <linux/types.h> 33 #include <linux/sched.h> 34 #include "crc32defs.h" 35 36 #if CRC_LE_BITS > 8 37 # define tole(x) ((__force u32) cpu_to_le32(x)) 38 #else 39 # define tole(x) (x) 40 #endif 41 42 #if CRC_BE_BITS > 8 43 # define tobe(x) ((__force u32) cpu_to_be32(x)) 44 #else 45 # define tobe(x) (x) 46 #endif 47 48 #include "crc32table.h" 49 50 MODULE_AUTHOR("Matt Domsch <Matt_Domsch@dell.com>"); 51 MODULE_DESCRIPTION("Various CRC32 calculations"); 52 MODULE_LICENSE("GPL"); 53 54 #if CRC_LE_BITS > 8 || CRC_BE_BITS > 8 55 56 /* implements slicing-by-4 or slicing-by-8 algorithm */ 57 static inline u32 __pure 58 crc32_body(u32 crc, unsigned char const *buf, size_t len, const u32 (*tab)[256]) 59 { 60 # ifdef __LITTLE_ENDIAN 61 # define DO_CRC(x) crc = t0[(crc ^ (x)) & 255] ^ (crc >> 8) 62 # define DO_CRC4 (t3[(q) & 255] ^ t2[(q >> 8) & 255] ^ \ 63 t1[(q >> 16) & 255] ^ t0[(q >> 24) & 255]) 64 # define DO_CRC8 (t7[(q) & 255] ^ t6[(q >> 8) & 255] ^ \ 65 t5[(q >> 16) & 255] ^ t4[(q >> 24) & 255]) 66 # else 67 # define DO_CRC(x) crc = t0[((crc >> 24) ^ (x)) & 255] ^ (crc << 8) 68 # define DO_CRC4 (t0[(q) & 255] ^ t1[(q >> 8) & 255] ^ \ 69 t2[(q >> 16) & 255] ^ t3[(q >> 24) & 255]) 70 # define DO_CRC8 (t4[(q) & 255] ^ t5[(q >> 8) & 255] ^ \ 71 t6[(q >> 16) & 255] ^ t7[(q >> 24) & 255]) 72 # endif 73 const u32 *b; 74 size_t rem_len; 75 # ifdef CONFIG_X86 76 size_t i; 77 # endif 78 const u32 *t0=tab[0], *t1=tab[1], *t2=tab[2], *t3=tab[3]; 79 # if CRC_LE_BITS != 32 80 const u32 *t4 = tab[4], *t5 = tab[5], *t6 = tab[6], *t7 = tab[7]; 81 # endif 82 u32 q; 83 84 /* Align it */ 85 if (unlikely((long)buf & 3 && len)) { 86 do { 87 DO_CRC(*buf++); 88 } while ((--len) && ((long)buf)&3); 89 } 90 91 # if CRC_LE_BITS == 32 92 rem_len = len & 3; 93 len = len >> 2; 94 # else 95 rem_len = len & 7; 96 len = len >> 3; 97 # endif 98 99 b = (const u32 *)buf; 100 # ifdef CONFIG_X86 101 --b; 102 for (i = 0; i < len; i++) { 103 # else 104 for (--b; len; --len) { 105 # endif 106 q = crc ^ *++b; /* use pre increment for speed */ 107 # if CRC_LE_BITS == 32 108 crc = DO_CRC4; 109 # else 110 crc = DO_CRC8; 111 q = *++b; 112 crc ^= DO_CRC4; 113 # endif 114 } 115 len = rem_len; 116 /* And the last few bytes */ 117 if (len) { 118 u8 *p = (u8 *)(b + 1) - 1; 119 # ifdef CONFIG_X86 120 for (i = 0; i < len; i++) 121 DO_CRC(*++p); /* use pre increment for speed */ 122 # else 123 do { 124 DO_CRC(*++p); /* use pre increment for speed */ 125 } while (--len); 126 # endif 127 } 128 return crc; 129 #undef DO_CRC 130 #undef DO_CRC4 131 #undef DO_CRC8 132 } 133 #endif 134 135 136 /** 137 * crc32_le_generic() - Calculate bitwise little-endian Ethernet AUTODIN II 138 * CRC32/CRC32C 139 * @crc: seed value for computation. ~0 for Ethernet, sometimes 0 for other 140 * uses, or the previous crc32/crc32c value if computing incrementally. 141 * @p: pointer to buffer over which CRC32/CRC32C is run 142 * @len: length of buffer @p 143 * @tab: little-endian Ethernet table 144 * @polynomial: CRC32/CRC32c LE polynomial 145 */ 146 static inline u32 __pure crc32_le_generic(u32 crc, unsigned char const *p, 147 size_t len, const u32 (*tab)[256], 148 u32 polynomial) 149 { 150 #if CRC_LE_BITS == 1 151 int i; 152 while (len--) { 153 crc ^= *p++; 154 for (i = 0; i < 8; i++) 155 crc = (crc >> 1) ^ ((crc & 1) ? polynomial : 0); 156 } 157 # elif CRC_LE_BITS == 2 158 while (len--) { 159 crc ^= *p++; 160 crc = (crc >> 2) ^ tab[0][crc & 3]; 161 crc = (crc >> 2) ^ tab[0][crc & 3]; 162 crc = (crc >> 2) ^ tab[0][crc & 3]; 163 crc = (crc >> 2) ^ tab[0][crc & 3]; 164 } 165 # elif CRC_LE_BITS == 4 166 while (len--) { 167 crc ^= *p++; 168 crc = (crc >> 4) ^ tab[0][crc & 15]; 169 crc = (crc >> 4) ^ tab[0][crc & 15]; 170 } 171 # elif CRC_LE_BITS == 8 172 /* aka Sarwate algorithm */ 173 while (len--) { 174 crc ^= *p++; 175 crc = (crc >> 8) ^ tab[0][crc & 255]; 176 } 177 # else 178 crc = (__force u32) __cpu_to_le32(crc); 179 crc = crc32_body(crc, p, len, tab); 180 crc = __le32_to_cpu((__force __le32)crc); 181 #endif 182 return crc; 183 } 184 185 #if CRC_LE_BITS == 1 186 u32 __pure __weak crc32_le(u32 crc, unsigned char const *p, size_t len) 187 { 188 return crc32_le_generic(crc, p, len, NULL, CRC32_POLY_LE); 189 } 190 u32 __pure __weak __crc32c_le(u32 crc, unsigned char const *p, size_t len) 191 { 192 return crc32_le_generic(crc, p, len, NULL, CRC32C_POLY_LE); 193 } 194 #else 195 u32 __pure __weak crc32_le(u32 crc, unsigned char const *p, size_t len) 196 { 197 return crc32_le_generic(crc, p, len, 198 (const u32 (*)[256])crc32table_le, CRC32_POLY_LE); 199 } 200 u32 __pure __weak __crc32c_le(u32 crc, unsigned char const *p, size_t len) 201 { 202 return crc32_le_generic(crc, p, len, 203 (const u32 (*)[256])crc32ctable_le, CRC32C_POLY_LE); 204 } 205 #endif 206 EXPORT_SYMBOL(crc32_le); 207 EXPORT_SYMBOL(__crc32c_le); 208 209 u32 __pure crc32_le_base(u32, unsigned char const *, size_t) __alias(crc32_le); 210 u32 __pure __crc32c_le_base(u32, unsigned char const *, size_t) __alias(__crc32c_le); 211 212 /* 213 * This multiplies the polynomials x and y modulo the given modulus. 214 * This follows the "little-endian" CRC convention that the lsbit 215 * represents the highest power of x, and the msbit represents x^0. 216 */ 217 static u32 __attribute_const__ gf2_multiply(u32 x, u32 y, u32 modulus) 218 { 219 u32 product = x & 1 ? y : 0; 220 int i; 221 222 for (i = 0; i < 31; i++) { 223 product = (product >> 1) ^ (product & 1 ? modulus : 0); 224 x >>= 1; 225 product ^= x & 1 ? y : 0; 226 } 227 228 return product; 229 } 230 231 /** 232 * crc32_generic_shift - Append @len 0 bytes to crc, in logarithmic time 233 * @crc: The original little-endian CRC (i.e. lsbit is x^31 coefficient) 234 * @len: The number of bytes. @crc is multiplied by x^(8*@len) 235 * @polynomial: The modulus used to reduce the result to 32 bits. 236 * 237 * It's possible to parallelize CRC computations by computing a CRC 238 * over separate ranges of a buffer, then summing them. 239 * This shifts the given CRC by 8*len bits (i.e. produces the same effect 240 * as appending len bytes of zero to the data), in time proportional 241 * to log(len). 242 */ 243 static u32 __attribute_const__ crc32_generic_shift(u32 crc, size_t len, 244 u32 polynomial) 245 { 246 u32 power = polynomial; /* CRC of x^32 */ 247 int i; 248 249 /* Shift up to 32 bits in the simple linear way */ 250 for (i = 0; i < 8 * (int)(len & 3); i++) 251 crc = (crc >> 1) ^ (crc & 1 ? polynomial : 0); 252 253 len >>= 2; 254 if (!len) 255 return crc; 256 257 for (;;) { 258 /* "power" is x^(2^i), modulo the polynomial */ 259 if (len & 1) 260 crc = gf2_multiply(crc, power, polynomial); 261 262 len >>= 1; 263 if (!len) 264 break; 265 266 /* Square power, advancing to x^(2^(i+1)) */ 267 power = gf2_multiply(power, power, polynomial); 268 } 269 270 return crc; 271 } 272 273 u32 __attribute_const__ crc32_le_shift(u32 crc, size_t len) 274 { 275 return crc32_generic_shift(crc, len, CRC32_POLY_LE); 276 } 277 278 u32 __attribute_const__ __crc32c_le_shift(u32 crc, size_t len) 279 { 280 return crc32_generic_shift(crc, len, CRC32C_POLY_LE); 281 } 282 EXPORT_SYMBOL(crc32_le_shift); 283 EXPORT_SYMBOL(__crc32c_le_shift); 284 285 /** 286 * crc32_be_generic() - Calculate bitwise big-endian Ethernet AUTODIN II CRC32 287 * @crc: seed value for computation. ~0 for Ethernet, sometimes 0 for 288 * other uses, or the previous crc32 value if computing incrementally. 289 * @p: pointer to buffer over which CRC32 is run 290 * @len: length of buffer @p 291 * @tab: big-endian Ethernet table 292 * @polynomial: CRC32 BE polynomial 293 */ 294 static inline u32 __pure crc32_be_generic(u32 crc, unsigned char const *p, 295 size_t len, const u32 (*tab)[256], 296 u32 polynomial) 297 { 298 #if CRC_BE_BITS == 1 299 int i; 300 while (len--) { 301 crc ^= *p++ << 24; 302 for (i = 0; i < 8; i++) 303 crc = 304 (crc << 1) ^ ((crc & 0x80000000) ? polynomial : 305 0); 306 } 307 # elif CRC_BE_BITS == 2 308 while (len--) { 309 crc ^= *p++ << 24; 310 crc = (crc << 2) ^ tab[0][crc >> 30]; 311 crc = (crc << 2) ^ tab[0][crc >> 30]; 312 crc = (crc << 2) ^ tab[0][crc >> 30]; 313 crc = (crc << 2) ^ tab[0][crc >> 30]; 314 } 315 # elif CRC_BE_BITS == 4 316 while (len--) { 317 crc ^= *p++ << 24; 318 crc = (crc << 4) ^ tab[0][crc >> 28]; 319 crc = (crc << 4) ^ tab[0][crc >> 28]; 320 } 321 # elif CRC_BE_BITS == 8 322 while (len--) { 323 crc ^= *p++ << 24; 324 crc = (crc << 8) ^ tab[0][crc >> 24]; 325 } 326 # else 327 crc = (__force u32) __cpu_to_be32(crc); 328 crc = crc32_body(crc, p, len, tab); 329 crc = __be32_to_cpu((__force __be32)crc); 330 # endif 331 return crc; 332 } 333 334 #if CRC_LE_BITS == 1 335 u32 __pure crc32_be(u32 crc, unsigned char const *p, size_t len) 336 { 337 return crc32_be_generic(crc, p, len, NULL, CRC32_POLY_BE); 338 } 339 #else 340 u32 __pure crc32_be(u32 crc, unsigned char const *p, size_t len) 341 { 342 return crc32_be_generic(crc, p, len, 343 (const u32 (*)[256])crc32table_be, CRC32_POLY_BE); 344 } 345 #endif 346 EXPORT_SYMBOL(crc32_be); 347