[linux-block.git] / lib / crc32.c

/*
 * 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/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,
			(const u32 (*)[256])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,
			(const u32 (*)[256])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);

/*
 * 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_LE_BITS == 1
u32 __pure 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 crc32_be(u32 crc, unsigned char const *p, size_t len)
{
	return crc32_be_generic(crc, p, len,
			(const u32 (*)[256])crc32table_be, CRC32_POLY_BE);
}
#endif
EXPORT_SYMBOL(crc32_be);
Commit	Line	Data
	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);