text: /* SPDX-License-Identifier: GPL-2.0 */
  /*
   *    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 <linux/uaccess.h>
  #include <linux/in6.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)
  {
  	union register_pair rp = {
  		.even = (unsigned long) buff,
  		.odd = (unsigned long) len,
  	};
  
  	asm volatile(
  		"0:	cksm	%[sum],%[rp]\n"
  		"	jo	0b\n"
  		: [sum] "+&d" (sum), [rp] "+&d" (rp.pair) : : "cc", "memory");
  	return 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 checksums on 4 octet boundaries.
   */
  static inline __sum16 ip_fast_csum(const void *iph, unsigned int ihl)
  {
  	__u64 csum = 0;
  	__u32 *ptr = (u32 *)iph;
  
  	csum += *ptr++;
  	csum += *ptr++;
  	csum += *ptr++;
  	csum += *ptr++;
  	ihl -= 4;
  	while (ihl--)
  		csum += *ptr++;
  	csum += (csum >> 32) | (csum << 32);
  	return csum_fold((__force __wsum)(csum >> 32));
  }
  
  /*
   * Computes the checksum of the TCP/UDP pseudo-header.
   * Returns a 32-bit checksum.
   */
  static inline __wsum csum_tcpudp_nofold(__be32 saddr, __be32 daddr, __u32 len,
  					__u8 proto, __wsum sum)
  {
  	__u64 csum = (__force __u64)sum;
  
  	csum += (__force __u32)saddr;
  	csum += (__force __u32)daddr;
  	csum += len;
  	csum += proto;
  	csum += (csum >> 32) | (csum << 32);
  	return (__force __wsum)(csum >> 32);
  }
  
  /*
   * 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, __u32 len,
  					__u8 proto, __wsum sum)
  {
  	return csum_fold(csum_tcpudp_nofold(saddr, daddr, len, proto, sum));
  }
  
  /*
   * Used for miscellaneous IP-like checksums, mainly icmp.
   */
  static inline __sum16 ip_compute_csum(const void *buff, int len)
  {
  	return csum_fold(csum_partial(buff, len, 0));
  }
  
  #define _HAVE_ARCH_IPV6_CSUM
  static inline __sum16 csum_ipv6_magic(const struct in6_addr *saddr,
  				      const struct in6_addr *daddr,
  				      __u32 len, __u8 proto, __wsum csum)
  {
  	__u64 sum = (__force __u64)csum;
  
  	sum += (__force __u32)saddr->s6_addr32[0];
  	sum += (__force __u32)saddr->s6_addr32[1];
  	sum += (__force __u32)saddr->s6_addr32[2];
  	sum += (__force __u32)saddr->s6_addr32[3];
  	sum += (__force __u32)daddr->s6_addr32[0];
  	sum += (__force __u32)daddr->s6_addr32[1];
  	sum += (__force __u32)daddr->s6_addr32[2];
  	sum += (__force __u32)daddr->s6_addr32[3];
  	sum += len;
  	sum += proto;
  	sum += (sum >> 32) | (sum << 32);
  	return csum_fold((__force __wsum)(sum >> 32));
  }
  
  #endif /* _S390_CHECKSUM_H */
  