diff options
Diffstat (limited to 'lib/crc32.c')
| -rw-r--r-- | lib/crc32.c | 344 |
1 files changed, 344 insertions, 0 deletions
diff --git a/lib/crc32.c b/lib/crc32.c new file mode 100644 index 000000000..5649847d0 --- /dev/null +++ b/lib/crc32.c @@ -0,0 +1,344 @@ +/* + * 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/staging/crc32.rst for a description of algorithms */ + +#include <linux/crc32.h> +#include <linux/crc32poly.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 __weak crc32_le(u32 crc, unsigned char const *p, size_t len) +{ + return crc32_le_generic(crc, p, len, NULL, CRC32_POLY_LE); +} +u32 __pure __weak __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 __weak crc32_le(u32 crc, unsigned char const *p, size_t len) +{ + return crc32_le_generic(crc, p, len, crc32table_le, CRC32_POLY_LE); +} +u32 __pure __weak __crc32c_le(u32 crc, unsigned char const *p, size_t len) +{ + return crc32_le_generic(crc, p, len, crc32ctable_le, CRC32C_POLY_LE); +} +#endif +EXPORT_SYMBOL(crc32_le); +EXPORT_SYMBOL(__crc32c_le); + +u32 __pure crc32_le_base(u32, unsigned char const *, size_t) __alias(crc32_le); +u32 __pure __crc32c_le_base(u32, unsigned char const *, size_t) __alias(__crc32c_le); +u32 __pure crc32_be_base(u32, unsigned char const *, size_t) __alias(crc32_be); + +/* + * 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_BE_BITS == 1 +u32 __pure __weak 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 __weak crc32_be(u32 crc, unsigned char const *p, size_t len) +{ + return crc32_be_generic(crc, p, len, crc32table_be, CRC32_POLY_BE); +} +#endif +EXPORT_SYMBOL(crc32_be); |