chacha.h

 1/* SPDX-License-Identifier: GPL-2.0 */
 2/*
 3 * ChaCha stream cipher (s390 optimized)
 4 *
 5 * Copyright IBM Corp. 2021
 6 */
 7
 8#include <linux/cpufeature.h>
 9#include <linux/export.h>
10#include <linux/kernel.h>
11#include <linux/sizes.h>
12#include <asm/fpu.h>
13#include "chacha-s390.h"
14
15#define hchacha_block_arch hchacha_block_generic /* not implemented yet */
16
17static void chacha_crypt_arch(struct chacha_state *state, u8 *dst,
18			      const u8 *src, unsigned int bytes, int nrounds)
19{
20	/* s390 chacha20 implementation has 20 rounds hard-coded,
21	 * it cannot handle a block of data or less, but otherwise
22	 * it can handle data of arbitrary size
23	 */
24	if (bytes <= CHACHA_BLOCK_SIZE || nrounds != 20 || !cpu_has_vx()) {
25		chacha_crypt_generic(state, dst, src, bytes, nrounds);
26	} else {
27		DECLARE_KERNEL_FPU_ONSTACK32(vxstate);
28
29		kernel_fpu_begin(&vxstate, KERNEL_VXR);
30		chacha20_vx(dst, src, bytes, &state->x[4], &state->x[12]);
31		kernel_fpu_end(&vxstate, KERNEL_VXR);
32
33		state->x[12] += round_up(bytes, CHACHA_BLOCK_SIZE) /
34				CHACHA_BLOCK_SIZE;
35	}
36}