1// SPDX-License-Identifier: GPL-2.0
  2/*
  3 * s390 ChaCha stream cipher.
  4 *
  5 * Copyright IBM Corp. 2021
  6 */
  7
  8#define KMSG_COMPONENT "chacha_s390"
  9#define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
 10
 11#include <crypto/internal/chacha.h>
 12#include <crypto/internal/skcipher.h>
 13#include <crypto/algapi.h>
 14#include <linux/cpufeature.h>
 15#include <linux/kernel.h>
 16#include <linux/module.h>
 17#include <linux/sizes.h>
 18#include <asm/fpu/api.h>
 19#include "chacha-s390.h"
 20
 21static void chacha20_crypt_s390(u32 *state, u8 *dst, const u8 *src,
 22				unsigned int nbytes, const u32 *key,
 23				u32 *counter)
 24{
 25	struct kernel_fpu vxstate;
 26
 27	kernel_fpu_begin(&vxstate, KERNEL_VXR);
 28	chacha20_vx(dst, src, nbytes, key, counter);
 29	kernel_fpu_end(&vxstate, KERNEL_VXR);
 30
 31	*counter += round_up(nbytes, CHACHA_BLOCK_SIZE) / CHACHA_BLOCK_SIZE;
 32}
 33
 34static int chacha20_s390(struct skcipher_request *req)
 35{
 36	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
 37	struct chacha_ctx *ctx = crypto_skcipher_ctx(tfm);
 38	u32 state[CHACHA_STATE_WORDS] __aligned(16);
 39	struct skcipher_walk walk;
 40	unsigned int nbytes;
 41	int rc;
 42
 43	rc = skcipher_walk_virt(&walk, req, false);
 44	chacha_init_generic(state, ctx->key, req->iv);
 45
 46	while (walk.nbytes > 0) {
 47		nbytes = walk.nbytes;
 48		if (nbytes < walk.total)
 49			nbytes = round_down(nbytes, walk.stride);
 50
 51		if (nbytes <= CHACHA_BLOCK_SIZE) {
 52			chacha_crypt_generic(state, walk.dst.virt.addr,
 53					     walk.src.virt.addr, nbytes,
 54					     ctx->nrounds);
 55		} else {
 56			chacha20_crypt_s390(state, walk.dst.virt.addr,
 57					    walk.src.virt.addr, nbytes,
 58					    &state[4], &state[12]);
 59		}
 60		rc = skcipher_walk_done(&walk, walk.nbytes - nbytes);
 61	}
 62	return rc;
 63}
 64
 65void hchacha_block_arch(const u32 *state, u32 *stream, int nrounds)
 66{
 67	/* TODO: implement hchacha_block_arch() in assembly */
 68	hchacha_block_generic(state, stream, nrounds);
 69}
 70EXPORT_SYMBOL(hchacha_block_arch);
 71
 72void chacha_init_arch(u32 *state, const u32 *key, const u8 *iv)
 73{
 74	chacha_init_generic(state, key, iv);
 75}
 76EXPORT_SYMBOL(chacha_init_arch);
 77
 78void chacha_crypt_arch(u32 *state, u8 *dst, const u8 *src,
 79		       unsigned int bytes, int nrounds)
 80{
 81	/* s390 chacha20 implementation has 20 rounds hard-coded,
 82	 * it cannot handle a block of data or less, but otherwise
 83	 * it can handle data of arbitrary size
 84	 */
 85	if (bytes <= CHACHA_BLOCK_SIZE || nrounds != 20 || !cpu_has_vx())
 86		chacha_crypt_generic(state, dst, src, bytes, nrounds);
 87	else
 88		chacha20_crypt_s390(state, dst, src, bytes,
 89				    &state[4], &state[12]);
 90}
 91EXPORT_SYMBOL(chacha_crypt_arch);
 92
 93static struct skcipher_alg chacha_algs[] = {
 94	{
 95		.base.cra_name		= "chacha20",
 96		.base.cra_driver_name	= "chacha20-s390",
 97		.base.cra_priority	= 900,
 98		.base.cra_blocksize	= 1,
 99		.base.cra_ctxsize	= sizeof(struct chacha_ctx),
100		.base.cra_module	= THIS_MODULE,
101
102		.min_keysize		= CHACHA_KEY_SIZE,
103		.max_keysize		= CHACHA_KEY_SIZE,
104		.ivsize			= CHACHA_IV_SIZE,
105		.chunksize		= CHACHA_BLOCK_SIZE,
106		.setkey			= chacha20_setkey,
107		.encrypt		= chacha20_s390,
108		.decrypt		= chacha20_s390,
109	}
110};
111
112static int __init chacha_mod_init(void)
113{
114	return IS_REACHABLE(CONFIG_CRYPTO_SKCIPHER) ?
115		crypto_register_skciphers(chacha_algs, ARRAY_SIZE(chacha_algs)) : 0;
116}
117
118static void __exit chacha_mod_fini(void)
119{
120	if (IS_REACHABLE(CONFIG_CRYPTO_SKCIPHER))
121		crypto_unregister_skciphers(chacha_algs, ARRAY_SIZE(chacha_algs));
122}
123
124module_cpu_feature_match(S390_CPU_FEATURE_VXRS, chacha_mod_init);
125module_exit(chacha_mod_fini);
126
127MODULE_DESCRIPTION("ChaCha20 stream cipher");
128MODULE_LICENSE("GPL v2");
129
130MODULE_ALIAS_CRYPTO("chacha20");