/*
* S390 fast network checksum routines
*
* S390 version
* Copyright IBM Corp. 1999
* Author(s): Ulrich Hild (first version)
* Martin Schwidefsky (heavily optimized CKSM version)
* D.J. Barrow (third attempt)
*/

#ifndef _S390_CHECKSUM_H
#define _S390_CHECKSUM_H

#include <asm/uaccess.h>

/*
* 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
*/
static inline __wsum
csum_partial(const void *buff, int len, __wsum sum)
{
register unsigned long reg2 asm("2") = (unsigned long) buff;
register unsigned long reg3 asm("3") = (unsigned long) len;

asm volatile(
"0: cksm %0,%1\n" /* do checksum on longs */
" jo 0b\n"
: "+d" (sum), "+d" (reg2), "+d" (reg3) : : "cc", "memory");
return sum;
}

/*
* the same as csum_partial_copy, but copies from user space.
*
* here even more important to align src and dst on a 32-bit (or even
* better 64-bit) boundary
*
* Copy from userspace and compute checksum. If we catch an exception
* then zero the rest of the buffer.
*/
static inline __wsum
csum_partial_copy_from_user(const void __user *src, void *dst,
int len, __wsum sum,
int *err_ptr)
{
int missing;

missing = copy_from_user(dst, src, len);
if (missing) {
memset(dst + len - missing, 0, missing);
*err_ptr = -EFAULT;
}

return csum_partial(dst, len, sum);
}


static inline __wsum
csum_partial_copy_nocheck (const void *src, void *dst, int len, __wsum sum)
{
memcpy(dst,src,len);
return csum_partial(dst, len, sum);
}

/*
* Fold a partial checksum without adding pseudo headers
*/
static inline __sum16 csum_fold(__wsum sum)
{
u32 csum = (__force u32) sum;

csum += (csum >> 16) + (csum << 16);
csum >>= 16;
return (__force __sum16) ~csum;
}

/*
* This is a version of ip_compute_csum() optimized for IP headers,
* which always checksum on 4 octet boundaries.
*
*/
static inline __sum16 ip_fast_csum(const void *iph, unsigned int ihl)
{
return csum_fold(csum_partial(iph, ihl*4, 0));
}

/*
* computes the checksum of the TCP/UDP pseudo-header
* returns a 32-bit checksum
*/
static inline __wsum
csum_tcpudp_nofold(__be32 saddr, __be32 daddr,
unsigned short len, unsigned short proto,
__wsum sum)
{
__u32 csum = (__force __u32)sum;

csum += (__force __u32)saddr;
if (csum < (__force __u32)saddr)
csum++;

csum += (__force __u32)daddr;
if (csum < (__force __u32)daddr)
csum++;

csum += len + proto;
if (csum < len + proto)
csum++;

return (__force __wsum)csum;
}

/*
* computes the checksum of the TCP/UDP pseudo-header
* returns a 16-bit checksum, already complemented
*/

static inline __sum16
csum_tcpudp_magic(__be32 saddr, __be32 daddr,
unsigned short len, unsigned short proto,
__wsum sum)
{
return csum_fold(csum_tcpudp_nofold(saddr,daddr,len,proto,sum));
}

/*
* this routine is used for miscellaneous IP-like checksums, mainly
* in icmp.c
*/

static inline __sum16 ip_compute_csum(const void *buff, int len)
{
return csum_fold(csum_partial(buff, len, 0));
}

#endif /* _S390_CHECKSUM_H */