crypto: s390 - add crypto library interface for ChaCha20

Implement a crypto library interface for the s390-native ChaCha20 cipher
algorithm. This allows us to stop to select CRYPTO_CHACHA20 and instead
select CRYPTO_ARCH_HAVE_LIB_CHACHA. This allows BIG_KEYS=y not to build
a whole ChaCha20 crypto infrastructure as a built-in, but build a smaller
CRYPTO_LIB_CHACHA instead.

Make CRYPTO_CHACHA_S390 config entry to look like similar ones on other
architectures. Remove CRYPTO_ALGAPI select as anyway it is selected by
CRYPTO_SKCIPHER.

Add a new test module and a test script for ChaCha20 cipher and its
interfaces. Here are test results on an idle z15 machine:

Data | Generic crypto TFM |  s390 crypto TFM |    s390 lib
size |      enc      dec  |     enc     dec  |     enc     dec
-----+--------------------+------------------+----------------
512b |   1545ns   1295ns  |   604ns   446ns  |   430ns  407ns
4k   |   9536ns   9463ns  |  2329ns  2174ns  |  2170ns  2154ns
64k  |  149.6us  149.3us  |  34.4us  34.5us  |  33.9us  33.1us
6M   |  23.61ms  23.11ms  |  4223us  4160us  |  3951us  4008us
60M  |  143.9ms  143.9ms  |  33.5ms  33.2ms  |  32.2ms  32.1ms

Signed-off-by: Vladis Dronov <[email protected]>
Reviewed-by: Harald Freudenberger <[email protected]>
Signed-off-by: Herbert Xu <[email protected]>

arch/s390/crypto/chacha-glue.c

@@ -62,6 +62,34 @@ static int chacha20_s390(struct skcipher_request *req)
 	return rc;
 }
 
+void hchacha_block_arch(const u32 *state, u32 *stream, int nrounds)
+{
+	/* TODO: implement hchacha_block_arch() in assembly */
+	hchacha_block_generic(state, stream, nrounds);
+}
+EXPORT_SYMBOL(hchacha_block_arch);
+
+void chacha_init_arch(u32 *state, const u32 *key, const u8 *iv)
+{
+	chacha_init_generic(state, key, iv);
+}
+EXPORT_SYMBOL(chacha_init_arch);
+
+void chacha_crypt_arch(u32 *state, u8 *dst, const u8 *src,
+		       unsigned int bytes, int nrounds)
+{
+	/* s390 chacha20 implementation has 20 rounds hard-coded,
+	 * it cannot handle a block of data or less, but otherwise
+	 * it can handle data of arbitrary size
+	 */
+	if (bytes <= CHACHA_BLOCK_SIZE || nrounds != 20)
+		chacha_crypt_generic(state, dst, src, bytes, nrounds);
+	else
+		chacha20_crypt_s390(state, dst, src, bytes,
+				    &state[4], &state[12]);
+}
+EXPORT_SYMBOL(chacha_crypt_arch);
+
 static struct skcipher_alg chacha_algs[] = {
 	{
 		.base.cra_name		= "chacha20",
@@ -83,12 +111,14 @@ static struct skcipher_alg chacha_algs[] = {
 
 static int __init chacha_mod_init(void)
 {
-	return crypto_register_skciphers(chacha_algs, ARRAY_SIZE(chacha_algs));
+	return IS_REACHABLE(CONFIG_CRYPTO_SKCIPHER) ?
+		crypto_register_skciphers(chacha_algs, ARRAY_SIZE(chacha_algs)) : 0;
 }
 
 static void __exit chacha_mod_fini(void)
 {
-	crypto_unregister_skciphers(chacha_algs, ARRAY_SIZE(chacha_algs));
+	if (IS_REACHABLE(CONFIG_CRYPTO_SKCIPHER))
+		crypto_unregister_skciphers(chacha_algs, ARRAY_SIZE(chacha_algs));
 }
 
 module_cpu_feature_match(VXRS, chacha_mod_init);

drivers/crypto/Kconfig

@@ -216,9 +216,9 @@ config CRYPTO_AES_S390
 config CRYPTO_CHACHA_S390
 	tristate "ChaCha20 stream cipher"
 	depends on S390
-	select CRYPTO_ALGAPI
 	select CRYPTO_SKCIPHER
-	select CRYPTO_CHACHA20
+	select CRYPTO_LIB_CHACHA_GENERIC
+	select CRYPTO_ARCH_HAVE_LIB_CHACHA
 	help
 	  This is the s390 SIMD implementation of the ChaCha20 stream
 	  cipher (RFC 7539).

tools/testing/crypto/chacha20-s390/Makefile

@@ -0,0 +1,12 @@
+# SPDX-License-Identifier: GPL-2.0
+#
+# Copyright (C) 2022 Red Hat, Inc.
+# Author: Vladis Dronov <[email protected]>
+
+obj-m += test_cipher.o
+test_cipher-y := test-cipher.o
+
+all:
+	make -C /lib/modules/$(shell uname -r)/build/ M=$(PWD) modules
+clean:
+	make -C /lib/modules/$(shell uname -r)/build/ M=$(PWD) clean

tools/testing/crypto/chacha20-s390/run-tests.sh

@@ -0,0 +1,34 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+#
+# Copyright (C) 2022 Red Hat, Inc.
+# Author: Vladis Dronov <[email protected]>
+#
+# This script runs (via instmod) test-cipher.ko module which invokes
+# generic and s390-native ChaCha20 encryprion algorithms with different
+# size of data. Check 'dmesg' for results.
+#
+# The insmod error is expected:
+# insmod: ERROR: could not insert module test_cipher.ko: Operation not permitted
+
+lsmod | grep chacha | cut -f1 -d' ' | xargs rmmod
+modprobe chacha_generic
+modprobe chacha_s390
+
+# run encryption for different data size, including whole block(s) +/- 1
+insmod test_cipher.ko size=63
+insmod test_cipher.ko size=64
+insmod test_cipher.ko size=65
+insmod test_cipher.ko size=127
+insmod test_cipher.ko size=128
+insmod test_cipher.ko size=129
+insmod test_cipher.ko size=511
+insmod test_cipher.ko size=512
+insmod test_cipher.ko size=513
+insmod test_cipher.ko size=4096
+insmod test_cipher.ko size=65611
+insmod test_cipher.ko size=6291456
+insmod test_cipher.ko size=62914560
+
+# print test logs
+dmesg | tail -170