linux/arch/s390/lib/csum-partial.c

// SPDX-License-Identifier: GPL-2.0

#include <linux/export.h>
#include <asm/checksum.h>
#include <asm/fpu.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 64-bit boundary.
 */
__wsum csum_partial(const void *buff, int len, __wsum sum)
{
	DECLARE_KERNEL_FPU_ONSTACK8(vxstate);

	if (!cpu_has_vx())
		return cksm(buff, len, sum);
	kernel_fpu_begin(&vxstate, KERNEL_VXR_V16V23);
	fpu_vlvgf(16, (__force u32)sum, 1);
	fpu_vzero(17);
	fpu_vzero(18);
	fpu_vzero(19);
	while (len >= 64) {
		fpu_vlm(20, 23, buff);
		fpu_vcksm(16, 20, 16);
		fpu_vcksm(17, 21, 17);
		fpu_vcksm(18, 22, 18);
		fpu_vcksm(19, 23, 19);
		buff += 64;
		len -= 64;
	}
	while (len >= 32) {
		fpu_vlm(20, 21, buff);
		fpu_vcksm(16, 20, 16);
		fpu_vcksm(17, 21, 17);
		buff += 32;
		len -= 32;
	}
	while (len >= 16) {
		fpu_vl(20, buff);
		fpu_vcksm(16, 20, 16);
		buff += 16;
		len -= 16;
	}
	if (len) {
		fpu_vll(20, len - 1, buff);
		fpu_vcksm(16, 20, 16);
	}
	fpu_vcksm(18, 19, 18);
	fpu_vcksm(16, 17, 16);
	fpu_vcksm(16, 18, 16);
	sum = (__force __wsum)fpu_vlgvf(16, 1);
	kernel_fpu_end(&vxstate, KERNEL_VXR_V16V23);
	return sum;
}
EXPORT_SYMBOL(csum_partial);