arm64: Implement optimised checksum routine

}

#define ip_fast_csum ip_fast_csum

extern unsigned int do_csum(const unsigned char *buff, int len);

#define do_csum do_csum

#include <asm-generic/checksum.h>

#endif	/* __ASM_CHECKSUM_H */

# SPDX-License-Identifier: GPL-2.0

lib-y		:= clear_user.o delay.o copy_from_user.o		\

		   copy_to_user.o copy_in_user.o copy_page.o		\

		   clear_page.o memchr.o memcpy.o memmove.o memset.o	\

		   memcmp.o strcmp.o strncmp.o strlen.o strnlen.o	\

		   strchr.o strrchr.o tishift.o

		   clear_page.o csum.o memchr.o memcpy.o memmove.o	\

		   memset.o memcmp.o strcmp.o strncmp.o strlen.o	\

		   strnlen.o strchr.o strrchr.o tishift.o

ifeq ($(CONFIG_KERNEL_MODE_NEON), y)

obj-$(CONFIG_XOR_BLOCKS)	+= xor-neon.o

// SPDX-License-Identifier: GPL-2.0-only

// Copyright (C) 2019-2020 Arm Ltd.

#include <linux/compiler.h>

#include <linux/kasan-checks.h>

#include <linux/kernel.h>

#include <net/checksum.h>

/* Looks dumb, but generates nice-ish code */

static u64 accumulate(u64 sum, u64 data)

{

	__uint128_t tmp = (__uint128_t)sum + data;

	return tmp + (tmp >> 64);

}

unsigned int do_csum(const unsigned char *buff, int len)

{

	unsigned int offset, shift, sum;

	const u64 *ptr;

	u64 data, sum64 = 0;

	offset = (unsigned long)buff & 7;

	/*

	 * This is to all intents and purposes safe, since rounding down cannot

	 * result in a different page or cache line being accessed, and @buff

	 * should absolutely not be pointing to anything read-sensitive. We do,

	 * however, have to be careful not to piss off KASAN, which means using

	 * unchecked reads to accommodate the head and tail, for which we'll

	 * compensate with an explicit check up-front.

	 */

	kasan_check_read(buff, len);

	ptr = (u64 *)(buff - offset);

	len = len + offset - 8;

	/*

	 * Head: zero out any excess leading bytes. Shifting back by the same

	 * amount should be at least as fast as any other way of handling the

	 * odd/even alignment, and means we can ignore it until the very end.

	 */

	shift = offset * 8;

	data = READ_ONCE_NOCHECK(*ptr++);

#ifdef __LITTLE_ENDIAN

	data = (data >> shift) << shift;

#else

	data = (data << shift) >> shift;

#endif

	/*

	 * Body: straightforward aligned loads from here on (the paired loads

	 * underlying the quadword type still only need dword alignment). The

	 * main loop strictly excludes the tail, so the second loop will always

	 * run at least once.

	 */

	while (unlikely(len > 64)) {

		__uint128_t tmp1, tmp2, tmp3, tmp4;

		tmp1 = READ_ONCE_NOCHECK(*(__uint128_t *)ptr);

		tmp2 = READ_ONCE_NOCHECK(*(__uint128_t *)(ptr + 2));

		tmp3 = READ_ONCE_NOCHECK(*(__uint128_t *)(ptr + 4));

		tmp4 = READ_ONCE_NOCHECK(*(__uint128_t *)(ptr + 6));

		len -= 64;

		ptr += 8;

		/* This is the "don't dump the carry flag into a GPR" idiom */

		tmp1 += (tmp1 >> 64) | (tmp1 << 64);

		tmp2 += (tmp2 >> 64) | (tmp2 << 64);

		tmp3 += (tmp3 >> 64) | (tmp3 << 64);

		tmp4 += (tmp4 >> 64) | (tmp4 << 64);

		tmp1 = ((tmp1 >> 64) << 64) | (tmp2 >> 64);

		tmp1 += (tmp1 >> 64) | (tmp1 << 64);

		tmp3 = ((tmp3 >> 64) << 64) | (tmp4 >> 64);

		tmp3 += (tmp3 >> 64) | (tmp3 << 64);

		tmp1 = ((tmp1 >> 64) << 64) | (tmp3 >> 64);

		tmp1 += (tmp1 >> 64) | (tmp1 << 64);

		tmp1 = ((tmp1 >> 64) << 64) | sum64;

		tmp1 += (tmp1 >> 64) | (tmp1 << 64);

		sum64 = tmp1 >> 64;

	}

	while (len > 8) {

		__uint128_t tmp;

		sum64 = accumulate(sum64, data);

		tmp = READ_ONCE_NOCHECK(*(__uint128_t *)ptr);

		len -= 16;

		ptr += 2;

#ifdef __LITTLE_ENDIAN

		data = tmp >> 64;

		sum64 = accumulate(sum64, tmp);

#else

		data = tmp;

		sum64 = accumulate(sum64, tmp >> 64);

#endif

	}

	if (len > 0) {

		sum64 = accumulate(sum64, data);

		data = READ_ONCE_NOCHECK(*ptr);

		len -= 8;

	}

	/*

	 * Tail: zero any over-read bytes similarly to the head, again

	 * preserving odd/even alignment.

	 */

	shift = len * -8;

#ifdef __LITTLE_ENDIAN

	data = (data << shift) >> shift;

#else

	data = (data >> shift) << shift;

#endif

	sum64 = accumulate(sum64, data);

	/* Finally, folding */

	sum64 += (sum64 >> 32) | (sum64 << 32);

	sum = sum64 >> 32;

	sum += (sum >> 16) | (sum << 16);

	if (offset & 1)

		return (u16)swab32(sum);

	return sum >> 16;

}