/* SPDX-License-Identifier: GPL-2.0 */
#ifndef __UM_CHECKSUM_H
#define __UM_CHECKSUM_H

#include <linux/string.h>
#include <linux/in6.h>
#include <linux/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
 */
extern __wsum csum_partial(const void *buff, int len, __wsum sum);

/* Do not call this directly. Declared for export type visibility. */
extern __visible __wsum csum_partial_copy_generic(const void *src, void *dst, int len);

/**
 * 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 __sum16 csum_fold(__wsum sum)
{
        __asm__(
                "  addl %1,%0\n"
                "  adcl $0xffff,%0"
                : "=r" (sum)
                : "r" ((__force u32)sum << 16),
                  "0" ((__force u32)sum & 0xffff0000)
        );
        return (__force __sum16)(~(__force u32)sum >> 16);
}

/**
 * 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 __wsum
csum_tcpudp_nofold(__be32 saddr, __be32 daddr, __u32 len,
                  __u8 proto, __wsum 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" ((len + proto) << 8), "0" (sum));
        return sum;
}

/*
 * 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));
}

/**
 * ip_fast_csum - Compute the IPv4 header checksum efficiently.
 * iph: ipv4 header
 * ihl: length of header / 4
 */
static inline __sum16 ip_fast_csum(const void *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 (__force __sum16)sum;
}

#ifdef CONFIG_X86_32
# include "checksum_32.h"
#else
# include "checksum_64.h"
#endif

#endif