linux/include/asm-powerpc/checksum.h

#ifndef _ASM_POWERPC_CHECKSUM_H
#define _ASM_POWERPC_CHECKSUM_H

/*
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or (at your option) any later version.
 */

/*
 * This is a version of ip_compute_csum() optimized for IP headers,
 * which always checksum on 4 octet boundaries.  ihl is the number
 * of 32-bit words and is always >= 5.
 */
extern unsigned short ip_fast_csum(unsigned char * iph, unsigned int ihl);

/*
 * computes the checksum of the TCP/UDP pseudo-header
 * returns a 16-bit checksum, already complemented
 */
extern unsigned short csum_tcpudp_magic(unsigned long saddr,
					unsigned long daddr,
					unsigned short len,
					unsigned short proto,
					unsigned int sum);

/*
 * computes the checksum of a memory block at buff, length len,
 * and adds in "sum" (32-bit)
 *
 * returns a 32-bit number suitable for feeding into itself
 * or csum_tcpudp_magic
 *
 * this function must be called with even lengths, except
 * for the last fragment, which may be odd
 *
 * it's best to have buff aligned on a 32-bit boundary
 */
extern unsigned int csum_partial(const unsigned char * buff, int len,
				 unsigned int sum);

/*
 * Computes the checksum of a memory block at src, length len,
 * and adds in "sum" (32-bit), while copying the block to dst.
 * If an access exception occurs on src or dst, it stores -EFAULT
 * to *src_err or *dst_err respectively (if that pointer is not
 * NULL), and, for an error on src, zeroes the rest of dst.
 *
 * Like csum_partial, this must be called with even lengths,
 * except for the last fragment.
 */
extern unsigned int csum_partial_copy_generic(const char *src, char *dst,
					      int len, unsigned int sum,
					      int *src_err, int *dst_err);
/*
 * the same as csum_partial, but copies from src to dst while it
 * checksums.
 */
unsigned int csum_partial_copy_nocheck(const char *src, 
				       char *dst, 
				       int len, 
				       unsigned int sum);

#define csum_partial_copy_from_user(src, dst, len, sum, errp)   \
        csum_partial_copy_generic((src), (dst), (len), (sum), (errp), NULL)

#define csum_partial_copy_nocheck(src, dst, len, sum)   \
        csum_partial_copy_generic((src), (dst), (len), (sum), NULL, NULL)


/*
 * turns a 32-bit partial checksum (e.g. from csum_partial) into a
 * 1's complement 16-bit checksum.
 */
static inline unsigned int csum_fold(unsigned int sum)
{
	unsigned int tmp;

	/* swap the two 16-bit halves of sum */
	__asm__("rlwinm %0,%1,16,0,31" : "=r" (tmp) : "r" (sum));
	/* if there is a carry from adding the two 16-bit halves,
	   it will carry from the lower half into the upper half,
	   giving us the correct sum in the upper half. */
	sum = ~(sum + tmp) >> 16;
	return sum;
}

/*
 * this routine is used for miscellaneous IP-like checksums, mainly
 * in icmp.c
 */
static inline unsigned short ip_compute_csum(unsigned char * buff, int len)
{
	return csum_fold(csum_partial(buff, len, 0));
}

#ifdef __powerpc64__
static inline u32 csum_tcpudp_nofold(u32 saddr,
                                     u32 daddr,
                                     unsigned short len,
                                     unsigned short proto,
                                     unsigned int sum)
{
	unsigned long s = sum;

	s += saddr;
	s += daddr;
	s += (proto << 16) + len;
	s += (s >> 32);
	return (u32) s;
}
#else
static inline unsigned long csum_tcpudp_nofold(unsigned long saddr,
						   unsigned long daddr,
						   unsigned short len,
						   unsigned short proto,
						   unsigned int sum)
{
    __asm__("\n\
	addc %0,%0,%1 \n\
	adde %0,%0,%2 \n\
	adde %0,%0,%3 \n\
	addze %0,%0 \n\
	"
	: "=r" (sum)
	: "r" (daddr), "r"(saddr), "r"((proto<<16)+len), "0"(sum));
    return sum;
}

#endif
#endif