crypto: x86/chacha - add XChaCha12 support

Now that the x86_64 SIMD implementations of ChaCha20 and XChaCha20 have
been refactored to support varying the number of rounds, add support for
XChaCha12.  This is identical to XChaCha20 except for the number of
rounds, which is 12 instead of 20.  This can be used by Adiantum.
Reviewed-by: Martin Willi <martin@strongswan.org>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

arch/x86/crypto/chacha_glue.c

@@ -232,6 +232,21 @@ static struct skcipher_alg algs[] = {
 		.setkey			= crypto_chacha20_setkey,
 		.encrypt		= xchacha_simd,
 		.decrypt		= xchacha_simd,
+	}, {
+		.base.cra_name		= "xchacha12",
+		.base.cra_driver_name	= "xchacha12-simd",
+		.base.cra_priority	= 300,
+		.base.cra_blocksize	= 1,
+		.base.cra_ctxsize	= sizeof(struct chacha_ctx),
+		.base.cra_module	= THIS_MODULE,
+
+		.min_keysize		= CHACHA_KEY_SIZE,
+		.max_keysize		= CHACHA_KEY_SIZE,
+		.ivsize			= XCHACHA_IV_SIZE,
+		.chunksize		= CHACHA_BLOCK_SIZE,
+		.setkey			= crypto_chacha12_setkey,
+		.encrypt		= xchacha_simd,
+		.decrypt		= xchacha_simd,
 	},
 };
 
@@ -268,3 +283,5 @@ MODULE_ALIAS_CRYPTO("chacha20");
 MODULE_ALIAS_CRYPTO("chacha20-simd");
 MODULE_ALIAS_CRYPTO("xchacha20");
 MODULE_ALIAS_CRYPTO("xchacha20-simd");
+MODULE_ALIAS_CRYPTO("xchacha12");
+MODULE_ALIAS_CRYPTO("xchacha12-simd");

crypto/Kconfig

@@ -1473,8 +1473,8 @@ config CRYPTO_CHACHA20_X86_64
 	select CRYPTO_BLKCIPHER
 	select CRYPTO_CHACHA20
 	help
-	  SSSE3, AVX2, and AVX-512VL optimized implementations of the ChaCha20
-	  and XChaCha20 stream ciphers.
+	  SSSE3, AVX2, and AVX-512VL optimized implementations of the ChaCha20,
+	  XChaCha20, and XChaCha12 stream ciphers.
 
 config CRYPTO_SEED
 	tristate "SEED cipher algorithm"