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.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 DECLARE_KERNEL_FPU_ONSTACK32(vxstate);
26
27 kernel_fpu_begin(&vxstate, KERNEL_VXR);
28 chacha20_vx(out: dst, inp: src, len: 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: &walk, req, atomic: false);
44 chacha_init_generic(state, key: ctx->key, iv: 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, dst: walk.dst.virt.addr,
53 src: walk.src.virt.addr, bytes: nbytes,
54 nrounds: ctx->nrounds);
55 } else {
56 chacha20_crypt_s390(state, dst: walk.dst.virt.addr,
57 src: walk.src.virt.addr, nbytes,
58 key: &state[4], counter: &state[12]);
59 }
60 rc = skcipher_walk_done(walk: &walk, err: 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, out: 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, nbytes: bytes,
89 key: &state[4], counter: &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(algs: 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(algs: 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");
131

source code of linux/arch/s390/crypto/chacha-glue.c