/* * 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 __purecrc32_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 == 1u32 __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);}#elseu32 __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);}#endifEXPORT_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 == 1u32 __pure crc32_be(u32 crc, unsigned char const *p, size_t len){	return crc32_be_generic(crc, p, len, NULL, CRCPOLY_BE);}#elseu32 __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);}#endifEXPORT_SYMBOL(crc32_be);