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/staging/crc32.rst 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 crc32_body(u32 crc,unsigned char const * buf,size_t len,const u32 (* tab)[256])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, crc32table_le, CRC32_POLY_LE); 198 } 199 u32 __pure __weak __crc32c_le(u32 crc, unsigned char const *p, size_t len) 200 { 201 return crc32_le_generic(crc, p, len, crc32ctable_le, CRC32C_POLY_LE); 202 } 203 #endif 204 EXPORT_SYMBOL(crc32_le); 205 EXPORT_SYMBOL(__crc32c_le); 206 207 u32 __pure crc32_le_base(u32, unsigned char const *, size_t) __alias(crc32_le); 208 u32 __pure __crc32c_le_base(u32, unsigned char const *, size_t) __alias(__crc32c_le); 209 u32 __pure crc32_be_base(u32, unsigned char const *, size_t) __alias(crc32_be); 210 211 /* 212 * This multiplies the polynomials x and y modulo the given modulus. 213 * This follows the "little-endian" CRC convention that the lsbit 214 * represents the highest power of x, and the msbit represents x^0. 215 */ 216 static u32 __attribute_const__ gf2_multiply(u32 x, u32 y, u32 modulus) 217 { 218 u32 product = x & 1 ? y : 0; 219 int i; 220 221 for (i = 0; i < 31; i++) { 222 product = (product >> 1) ^ (product & 1 ? modulus : 0); 223 x >>= 1; 224 product ^= x & 1 ? y : 0; 225 } 226 227 return product; 228 } 229 230 /** 231 * crc32_generic_shift - Append @len 0 bytes to crc, in logarithmic time 232 * @crc: The original little-endian CRC (i.e. lsbit is x^31 coefficient) 233 * @len: The number of bytes. @crc is multiplied by x^(8*@len) 234 * @polynomial: The modulus used to reduce the result to 32 bits. 235 * 236 * It's possible to parallelize CRC computations by computing a CRC 237 * over separate ranges of a buffer, then summing them. 238 * This shifts the given CRC by 8*len bits (i.e. produces the same effect 239 * as appending len bytes of zero to the data), in time proportional 240 * to log(len). 241 */ 242 static u32 __attribute_const__ crc32_generic_shift(u32 crc, size_t len, 243 u32 polynomial) 244 { 245 u32 power = polynomial; /* CRC of x^32 */ 246 int i; 247 248 /* Shift up to 32 bits in the simple linear way */ 249 for (i = 0; i < 8 * (int)(len & 3); i++) 250 crc = (crc >> 1) ^ (crc & 1 ? polynomial : 0); 251 252 len >>= 2; 253 if (!len) 254 return crc; 255 256 for (;;) { 257 /* "power" is x^(2^i), modulo the polynomial */ 258 if (len & 1) 259 crc = gf2_multiply(crc, power, polynomial); 260 261 len >>= 1; 262 if (!len) 263 break; 264 265 /* Square power, advancing to x^(2^(i+1)) */ 266 power = gf2_multiply(power, power, polynomial); 267 } 268 269 return crc; 270 } 271 272 u32 __attribute_const__ crc32_le_shift(u32 crc, size_t len) 273 { 274 return crc32_generic_shift(crc, len, CRC32_POLY_LE); 275 } 276 277 u32 __attribute_const__ __crc32c_le_shift(u32 crc, size_t len) 278 { 279 return crc32_generic_shift(crc, len, CRC32C_POLY_LE); 280 } 281 EXPORT_SYMBOL(crc32_le_shift); 282 EXPORT_SYMBOL(__crc32c_le_shift); 283 284 /** 285 * crc32_be_generic() - Calculate bitwise big-endian Ethernet AUTODIN II CRC32 286 * @crc: seed value for computation. ~0 for Ethernet, sometimes 0 for 287 * other uses, or the previous crc32 value if computing incrementally. 288 * @p: pointer to buffer over which CRC32 is run 289 * @len: length of buffer @p 290 * @tab: big-endian Ethernet table 291 * @polynomial: CRC32 BE polynomial 292 */ 293 static inline u32 __pure crc32_be_generic(u32 crc, unsigned char const *p, 294 size_t len, const u32 (*tab)[256], 295 u32 polynomial) 296 { 297 #if CRC_BE_BITS == 1 298 int i; 299 while (len--) { 300 crc ^= *p++ << 24; 301 for (i = 0; i < 8; i++) 302 crc = 303 (crc << 1) ^ ((crc & 0x80000000) ? polynomial : 304 0); 305 } 306 # elif CRC_BE_BITS == 2 307 while (len--) { 308 crc ^= *p++ << 24; 309 crc = (crc << 2) ^ tab[0][crc >> 30]; 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 } 314 # elif CRC_BE_BITS == 4 315 while (len--) { 316 crc ^= *p++ << 24; 317 crc = (crc << 4) ^ tab[0][crc >> 28]; 318 crc = (crc << 4) ^ tab[0][crc >> 28]; 319 } 320 # elif CRC_BE_BITS == 8 321 while (len--) { 322 crc ^= *p++ << 24; 323 crc = (crc << 8) ^ tab[0][crc >> 24]; 324 } 325 # else 326 crc = (__force u32) __cpu_to_be32(crc); 327 crc = crc32_body(crc, p, len, tab); 328 crc = __be32_to_cpu((__force __be32)crc); 329 # endif 330 return crc; 331 } 332 333 #if CRC_BE_BITS == 1 334 u32 __pure __weak crc32_be(u32 crc, unsigned char const *p, size_t len) 335 { 336 return crc32_be_generic(crc, p, len, NULL, CRC32_POLY_BE); 337 } 338 #else 339 u32 __pure __weak crc32_be(u32 crc, unsigned char const *p, size_t len) 340 { 341 return crc32_be_generic(crc, p, len, crc32table_be, CRC32_POLY_BE); 342 } 343 #endif 344 EXPORT_SYMBOL(crc32_be); 345