linux/include/asm-x86_64/checksum.h

#ifndef _X86_64_CHECKSUM_H
#define _X86_64_CHECKSUM_H

/* 
 * Checksums for x86-64 
 * Copyright 2002 by Andi Kleen, SuSE Labs 
 * with some code from asm-i386/checksum.h
 */ 

#include <linux/compiler.h>
#include <asm/uaccess.h>
#include <asm/byteorder.h>

/** 
 * csum_fold - Fold and invert a 32bit checksum.
 * sum: 32bit unfolded sum
 * 
 * Fold a 32bit running checksum to 16bit and invert it. This is usually
 * the last step before putting a checksum into a packet.
 * Make sure not to mix with 64bit checksums.
 */
static inline unsigned int csum_fold(unsigned int sum)
{
	__asm__(
		"  addl %1,%0\n"
		"  adcl $0xffff,%0"
		: "=r" (sum)
		: "r" (sum << 16), "0" (sum & 0xffff0000)
	);
	return (~sum) >> 16;
}

/*
 *	This is a version of ip_compute_csum() optimized for IP headers,
 *	which always checksum on 4 octet boundaries.
 *
 *	By Jorge Cwik <jorge@laser.satlink.net>, adapted for linux by
 *	Arnt Gulbrandsen.
 */

/**
 * ip_fast_csum - Compute the IPv4 header checksum efficiently.
 * iph: ipv4 header
 * ihl: length of header / 4
 */ 
static inline unsigned short ip_fast_csum(unsigned char *iph, unsigned int ihl) 
{
	unsigned int sum;

	asm(	"  movl (%1), %0\n"
		"  subl $4, %2\n"
		"  jbe 2f\n"
		"  addl 4(%1), %0\n"
		"  adcl 8(%1), %0\n"
		"  adcl 12(%1), %0\n"
		"1: adcl 16(%1), %0\n"
		"  lea 4(%1), %1\n"
		"  decl %2\n"
		"  jne	1b\n"
		"  adcl $0, %0\n"
		"  movl %0, %2\n"
		"  shrl $16, %0\n"
		"  addw %w2, %w0\n"
		"  adcl $0, %0\n"
		"  notl %0\n"
		"2:"
	/* Since the input registers which are loaded with iph and ipl
	   are modified, we must also specify them as outputs, or gcc
	   will assume they contain their original values. */
	: "=r" (sum), "=r" (iph), "=r" (ihl)
	: "1" (iph), "2" (ihl)
	: "memory");
	return(sum);
}

/** 
 * csum_tcpup_nofold - Compute an IPv4 pseudo header checksum.
 * @saddr: source address
 * @daddr: destination address
 * @len: length of packet
 * @proto: ip protocol of packet
 * @sum: initial sum to be added in (32bit unfolded) 
 * 
 * Returns the pseudo header checksum the input data. Result is 
 * 32bit unfolded.
 */
static inline unsigned long 
csum_tcpudp_nofold(unsigned saddr, unsigned daddr, unsigned short len,
		   unsigned short proto, unsigned int sum) 
{
	asm("  addl %1, %0\n"
	    "  adcl %2, %0\n"
	    "  adcl %3, %0\n"
	    "  adcl $0, %0\n"
		: "=r" (sum)
	    : "g" (daddr), "g" (saddr), "g" ((ntohs(len)<<16)+proto*256), "0" (sum));
    return sum;
}


/** 
 * csum_tcpup_magic - Compute an IPv4 pseudo header checksum.
 * @saddr: source address
 * @daddr: destination address
 * @len: length of packet
 * @proto: ip protocol of packet
 * @sum: initial sum to be added in (32bit unfolded) 
 * 
 * Returns the 16bit pseudo header checksum the input data already
 * complemented and ready to be filled in.
 */
static inline unsigned short int 
csum_tcpudp_magic(unsigned long saddr, unsigned long daddr,
		  unsigned short len, unsigned short proto, unsigned int sum) 
{
	return csum_fold(csum_tcpudp_nofold(saddr,daddr,len,proto,sum));
}

/** 
 * csum_partial - Compute an internet checksum.
 * @buff: buffer to be checksummed
 * @len: length of buffer.
 * @sum: initial sum to be added in (32bit unfolded)
 *
 * Returns the 32bit unfolded internet checksum of the buffer.
 * Before filling it in it needs to be csum_fold()'ed.
 * buff should be aligned to a 64bit boundary if possible.
 */ 
extern unsigned int csum_partial(const unsigned char *buff, unsigned len, unsigned int sum);

#define  _HAVE_ARCH_COPY_AND_CSUM_FROM_USER 1
#define HAVE_CSUM_COPY_USER 1


/* Do not call this directly. Use the wrappers below */
extern unsigned long csum_partial_copy_generic(const unsigned char *src, const unsigned char *dst,
					       unsigned len,
					       unsigned sum, 
					       int *src_err_ptr, int *dst_err_ptr);


extern unsigned int csum_partial_copy_from_user(const unsigned char __user *src, unsigned char *dst,
				       int len, unsigned int isum, int *errp);
extern unsigned int csum_partial_copy_to_user(const unsigned char *src, unsigned char __user *dst,
				      int len, unsigned int isum, int *errp);
extern unsigned int csum_partial_copy_nocheck(const unsigned char *src, unsigned char *dst, int len,
					      unsigned int sum);

/* Old names. To be removed. */
#define csum_and_copy_to_user csum_partial_copy_to_user
#define csum_and_copy_from_user csum_partial_copy_from_user

/** 
 * ip_compute_csum - Compute an 16bit IP checksum.
 * @buff: buffer address.
 * @len: length of buffer.
 *
 * Returns the 16bit folded/inverted checksum of the passed buffer.
 * Ready to fill in.
 */
extern unsigned short ip_compute_csum(unsigned char * buff, int len);

/**
 * csum_ipv6_magic - Compute checksum of an IPv6 pseudo header.
 * @saddr: source address
 * @daddr: destination address
 * @len: length of packet
 * @proto: protocol of packet
 * @sum: initial sum (32bit unfolded) to be added in
 *
 * Computes an IPv6 pseudo header checksum. This sum is added the checksum 
 * into UDP/TCP packets and contains some link layer information.
 * Returns the unfolded 32bit checksum.
 */

struct in6_addr;

#define _HAVE_ARCH_IPV6_CSUM 1
extern unsigned short 
csum_ipv6_magic(struct in6_addr *saddr, struct in6_addr *daddr,
		__u32 len, unsigned short proto, unsigned int sum);

static inline unsigned add32_with_carry(unsigned a, unsigned b)
{
	asm("addl %2,%0\n\t"
	    "adcl $0,%0" 
	    : "=r" (a) 
	    : "0" (a), "r" (b));
	return a;
}

#endif