// SPDX-License-Identifier: GPL-2.0
/*
 * arch/x86_64/lib/csum-partial.c
 *
 * This file contains network checksum routines that are better done
 * in an architecture-specific manner due to speed.
 */

#include <linux/compiler.h>
#include <linux/export.h>
#include <asm/checksum.h>
#include <asm/word-at-a-time.h>

static inline __wsum csum_finalize_sum(u64 temp64)
{
        return (__force __wsum)((temp64 + ror64(temp64, 32)) >> 32);
}

static inline unsigned long update_csum_40b(unsigned long sum, const unsigned long m[5])
{
        asm("addq %1,%0\n\t"
             "adcq %2,%0\n\t"
             "adcq %3,%0\n\t"
             "adcq %4,%0\n\t"
             "adcq %5,%0\n\t"
             "adcq $0,%0"
                :"+r" (sum)
                :"m" (m[0]), "m" (m[1]), "m" (m[2]),
                 "m" (m[3]), "m" (m[4]));
        return sum;
}

/*
 * Do a checksum on an arbitrary memory area.
 * Returns a 32bit checksum.
 *
 * This isn't as time critical as it used to be because many NICs
 * do hardware checksumming these days.
 *
 * Still, with CHECKSUM_COMPLETE this is called to compute
 * checksums on IPv6 headers (40 bytes) and other small parts.
 * it's best to have buff aligned on a 64-bit boundary
 */
__wsum csum_partial(const void *buff, int len, __wsum sum)
{
        u64 temp64 = (__force u64)sum;

        /* Do two 40-byte chunks in parallel to get better ILP */
        if (likely(len >= 80)) {
                u64 temp64_2 = 0;
                do {
                        temp64 = update_csum_40b(temp64, buff);
                        temp64_2 = update_csum_40b(temp64_2, buff + 40);
                        buff += 80;
                        len -= 80;
                } while (len >= 80);

                asm("addq %1,%0\n\t"
                    "adcq $0,%0"
                    :"+r" (temp64): "r" (temp64_2));
        }

        /*
         * len == 40 is the hot case due to IPv6 headers, so return
         * early for that exact case without checking the tail bytes.
         */
        if (len >= 40) {
                temp64 = update_csum_40b(temp64, buff);
                len -= 40;
                if (!len)
                        return csum_finalize_sum(temp64);
                buff += 40;
        }

        if (len & 32) {
                asm("addq 0*8(%[src]),%[res]\n\t"
                    "adcq 1*8(%[src]),%[res]\n\t"
                    "adcq 2*8(%[src]),%[res]\n\t"
                    "adcq 3*8(%[src]),%[res]\n\t"
                    "adcq $0,%[res]"
                    : [res] "+r"(temp64)
                    : [src] "r"(buff), "m"(*(const char(*)[32])buff));
                buff += 32;
        }
        if (len & 16) {
                asm("addq 0*8(%[src]),%[res]\n\t"
                    "adcq 1*8(%[src]),%[res]\n\t"
                    "adcq $0,%[res]"
                    : [res] "+r"(temp64)
                    : [src] "r"(buff), "m"(*(const char(*)[16])buff));
                buff += 16;
        }
        if (len & 8) {
                asm("addq 0*8(%[src]),%[res]\n\t"
                    "adcq $0,%[res]"
                    : [res] "+r"(temp64)
                    : [src] "r"(buff), "m"(*(const char(*)[8])buff));
                buff += 8;
        }
        if (len & 7) {
                unsigned int shift = (-len << 3) & 63;
                unsigned long trail;

                trail = (load_unaligned_zeropad(buff) << shift) >> shift;

                asm("addq %[trail],%[res]\n\t"
                    "adcq $0,%[res]"
                    : [res] "+r"(temp64)
                    : [trail] "r"(trail));
        }
        return csum_finalize_sum(temp64);
}
EXPORT_SYMBOL(csum_partial);

/*
 * this routine is used for miscellaneous IP-like checksums, mainly
 * in icmp.c
 */
__sum16 ip_compute_csum(const void *buff, int len)
{
        return csum_fold(csum_partial(buff, len, 0));
}
EXPORT_SYMBOL(ip_compute_csum);