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1/*2 * Aug 8, 2011 Bob Pearson with help from Joakim Tjernlund and George Spelvin3 * cleaned up code to current version of sparse and added the slicing-by-84 * 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 was9 * subsequently included in the kernel, thus was re-licensed under the10 * 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 takes17 * seed as an argument, and doesn't xor at the end. Then individual18 * 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 > 837# define tole(x) ((__force u32) cpu_to_le32(x))38#else39# define tole(x) (x)40#endif41 42#if CRC_BE_BITS > 843# define tobe(x) ((__force u32) cpu_to_be32(x))44#else45# define tobe(x) (x)46#endif47 48#include "crc32table.h"49 50MODULE_AUTHOR("Matt Domsch <Matt_Domsch@dell.com>");51MODULE_DESCRIPTION("Various CRC32 calculations");52MODULE_LICENSE("GPL");53 54#if CRC_LE_BITS > 8 || CRC_BE_BITS > 855 56/* implements slicing-by-4 or slicing-by-8 algorithm */57static inline u32 __pure58crc32_body(u32 crc, unsigned char const *buf, size_t len, const u32 (*tab)[256])59{60# ifdef __LITTLE_ENDIAN61# 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# else67# 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# endif73 const u32 *b;74 size_t rem_len;75# ifdef CONFIG_X8676 size_t i;77# endif78 const u32 *t0=tab[0], *t1=tab[1], *t2=tab[2], *t3=tab[3];79# if CRC_LE_BITS != 3280 const u32 *t4 = tab[4], *t5 = tab[5], *t6 = tab[6], *t7 = tab[7];81# endif82 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 == 3292 rem_len = len & 3;93 len = len >> 2;94# else95 rem_len = len & 7;96 len = len >> 3;97# endif98 99 b = (const u32 *)buf;100# ifdef CONFIG_X86101 --b;102 for (i = 0; i < len; i++) {103# else104 for (--b; len; --len) {105# endif106 q = crc ^ *++b; /* use pre increment for speed */107# if CRC_LE_BITS == 32108 crc = DO_CRC4;109# else110 crc = DO_CRC8;111 q = *++b;112 crc ^= DO_CRC4;113# endif114 }115 len = rem_len;116 /* And the last few bytes */117 if (len) {118 u8 *p = (u8 *)(b + 1) - 1;119# ifdef CONFIG_X86120 for (i = 0; i < len; i++)121 DO_CRC(*++p); /* use pre increment for speed */122# else123 do {124 DO_CRC(*++p); /* use pre increment for speed */125 } while (--len);126# endif127 }128 return crc;129#undef DO_CRC130#undef DO_CRC4131#undef DO_CRC8132}133#endif134 135 136/**137 * crc32_le_generic() - Calculate bitwise little-endian Ethernet AUTODIN II138 * CRC32/CRC32C139 * @crc: seed value for computation. ~0 for Ethernet, sometimes 0 for other140 * uses, or the previous crc32/crc32c value if computing incrementally.141 * @p: pointer to buffer over which CRC32/CRC32C is run142 * @len: length of buffer @p143 * @tab: little-endian Ethernet table144 * @polynomial: CRC32/CRC32c LE polynomial145 */146static 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 == 1151 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 == 2158 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 == 4166 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 == 8172 /* aka Sarwate algorithm */173 while (len--) {174 crc ^= *p++;175 crc = (crc >> 8) ^ tab[0][crc & 255];176 }177# else178 crc = (__force u32) __cpu_to_le32(crc);179 crc = crc32_body(crc, p, len, tab);180 crc = __le32_to_cpu((__force __le32)crc);181#endif182 return crc;183}184 185#if CRC_LE_BITS == 1186u32 __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}190u32 __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#else195u32 __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}199u32 __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#endif204EXPORT_SYMBOL(crc32_le);205EXPORT_SYMBOL(__crc32c_le);206 207u32 __pure crc32_le_base(u32, unsigned char const *, size_t) __alias(crc32_le);208u32 __pure __crc32c_le_base(u32, unsigned char const *, size_t) __alias(__crc32c_le);209u32 __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 lsbit214 * represents the highest power of x, and the msbit represents x^0.215 */216static 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 time232 * @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 CRC237 * over separate ranges of a buffer, then summing them.238 * This shifts the given CRC by 8*len bits (i.e. produces the same effect239 * as appending len bytes of zero to the data), in time proportional240 * to log(len).241 */242static 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 272u32 __attribute_const__ crc32_le_shift(u32 crc, size_t len)273{274 return crc32_generic_shift(crc, len, CRC32_POLY_LE);275}276 277u32 __attribute_const__ __crc32c_le_shift(u32 crc, size_t len)278{279 return crc32_generic_shift(crc, len, CRC32C_POLY_LE);280}281EXPORT_SYMBOL(crc32_le_shift);282EXPORT_SYMBOL(__crc32c_le_shift);283 284/**285 * crc32_be_generic() - Calculate bitwise big-endian Ethernet AUTODIN II CRC32286 * @crc: seed value for computation. ~0 for Ethernet, sometimes 0 for287 * other uses, or the previous crc32 value if computing incrementally.288 * @p: pointer to buffer over which CRC32 is run289 * @len: length of buffer @p290 * @tab: big-endian Ethernet table291 * @polynomial: CRC32 BE polynomial292 */293static 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 == 1298 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 == 2307 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 == 4315 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 == 8321 while (len--) {322 crc ^= *p++ << 24;323 crc = (crc << 8) ^ tab[0][crc >> 24];324 }325# else326 crc = (__force u32) __cpu_to_be32(crc);327 crc = crc32_body(crc, p, len, tab);328 crc = __be32_to_cpu((__force __be32)crc);329# endif330 return crc;331}332 333#if CRC_BE_BITS == 1334u32 __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#else339u32 __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#endif344EXPORT_SYMBOL(crc32_be);345