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
21 static 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(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
34 static 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
65 void 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 }
70 EXPORT_SYMBOL(hchacha_block_arch);
71
72 void chacha_init_arch(u32 *state, const u32 *key, const u8 *iv)
73 {
74 chacha_init_generic(state, key, iv);
75 }
76 EXPORT_SYMBOL(chacha_init_arch);
77
78 void 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 }
91 EXPORT_SYMBOL(chacha_crypt_arch);
92
93 static 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
112 static 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
118 static 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
124 module_cpu_feature_match(S390_CPU_FEATURE_VXRS, chacha_mod_init);
125 module_exit(chacha_mod_fini);
126
127 MODULE_DESCRIPTION("ChaCha20 stream cipher");
128 MODULE_LICENSE("GPL v2");
129
130 MODULE_ALIAS_CRYPTO("chacha20");
131
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