s390/crypto: Add hardware acceleration for full AES-XTS mode

Add new cipher exploiting the full AES-XTS hardware acceleration
introduced with message-security assist extension 10.

The full AES-XTS cipher is registered as preferred cipher in addition
to the discrete AES-XTS variant.
Reviewed-by: Harald Freudenberger <freude@linux.ibm.com>
Signed-off-by: Holger Dengler <dengler@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

arch/s390/crypto/aes_s390.c

@@ -51,8 +51,13 @@ struct s390_aes_ctx {
 };
 
 struct s390_xts_ctx {
-	u8 key[32];
-	u8 pcc_key[32];
+	union {
+		u8 keys[64];
+		struct {
+			u8 key[32];
+			u8 pcc_key[32];
+		};
+	};
 	int key_len;
 	unsigned long fc;
 	struct crypto_skcipher *fallback;
@@ -526,6 +531,108 @@ static struct skcipher_alg xts_aes_alg = {
 	.decrypt		=	xts_aes_decrypt,
 };
 
+static int fullxts_aes_set_key(struct crypto_skcipher *tfm, const u8 *in_key,
+			       unsigned int key_len)
+{
+	struct s390_xts_ctx *xts_ctx = crypto_skcipher_ctx(tfm);
+	unsigned long fc;
+	int err;
+
+	err = xts_fallback_setkey(tfm, in_key, key_len);
+	if (err)
+		return err;
+
+	/* Pick the correct function code based on the key length */
+	fc = (key_len == 32) ? CPACF_KM_XTS_128_FULL :
+	     (key_len == 64) ? CPACF_KM_XTS_256_FULL : 0;
+
+	/* Check if the function code is available */
+	xts_ctx->fc = (fc && cpacf_test_func(&km_functions, fc)) ? fc : 0;
+	if (!xts_ctx->fc)
+		return 0;
+
+	/* Store double-key */
+	memcpy(xts_ctx->keys, in_key, key_len);
+	xts_ctx->key_len = key_len;
+	return 0;
+}
+
+static int fullxts_aes_crypt(struct skcipher_request *req,  unsigned long modifier)
+{
+	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
+	struct s390_xts_ctx *xts_ctx = crypto_skcipher_ctx(tfm);
+	unsigned int offset, nbytes, n;
+	struct skcipher_walk walk;
+	int ret;
+	struct {
+		__u8 key[64];
+		__u8 tweak[16];
+		__u8 nap[16];
+	} fxts_param = {
+		.nap = {0},
+	};
+
+	if (req->cryptlen < AES_BLOCK_SIZE)
+		return -EINVAL;
+
+	if (unlikely(!xts_ctx->fc || (req->cryptlen % AES_BLOCK_SIZE) != 0)) {
+		struct skcipher_request *subreq = skcipher_request_ctx(req);
+
+		*subreq = *req;
+		skcipher_request_set_tfm(subreq, xts_ctx->fallback);
+		return (modifier & CPACF_DECRYPT) ?
+			crypto_skcipher_decrypt(subreq) :
+			crypto_skcipher_encrypt(subreq);
+	}
+
+	ret = skcipher_walk_virt(&walk, req, false);
+	if (ret)
+		return ret;
+
+	offset = xts_ctx->key_len & 0x20;
+	memcpy(fxts_param.key + offset, xts_ctx->keys, xts_ctx->key_len);
+	memcpy(fxts_param.tweak, req->iv, AES_BLOCK_SIZE);
+	fxts_param.nap[0] = 0x01; /* initial alpha power (1, little-endian) */
+
+	while ((nbytes = walk.nbytes) != 0) {
+		/* only use complete blocks */
+		n = nbytes & ~(AES_BLOCK_SIZE - 1);
+		cpacf_km(xts_ctx->fc | modifier, fxts_param.key + offset,
+			 walk.dst.virt.addr, walk.src.virt.addr, n);
+		ret = skcipher_walk_done(&walk, nbytes - n);
+	}
+	memzero_explicit(&fxts_param, sizeof(fxts_param));
+	return ret;
+}
+
+static int fullxts_aes_encrypt(struct skcipher_request *req)
+{
+	return fullxts_aes_crypt(req, 0);
+}
+
+static int fullxts_aes_decrypt(struct skcipher_request *req)
+{
+	return fullxts_aes_crypt(req, CPACF_DECRYPT);
+}
+
+static struct skcipher_alg fullxts_aes_alg = {
+	.base.cra_name		=	"xts(aes)",
+	.base.cra_driver_name	=	"full-xts-aes-s390",
+	.base.cra_priority	=	403,	/* aes-xts-s390 + 1 */
+	.base.cra_flags		=	CRYPTO_ALG_NEED_FALLBACK,
+	.base.cra_blocksize	=	AES_BLOCK_SIZE,
+	.base.cra_ctxsize	=	sizeof(struct s390_xts_ctx),
+	.base.cra_module	=	THIS_MODULE,
+	.init			=	xts_fallback_init,
+	.exit			=	xts_fallback_exit,
+	.min_keysize		=	2 * AES_MIN_KEY_SIZE,
+	.max_keysize		=	2 * AES_MAX_KEY_SIZE,
+	.ivsize			=	AES_BLOCK_SIZE,
+	.setkey			=	fullxts_aes_set_key,
+	.encrypt		=	fullxts_aes_encrypt,
+	.decrypt		=	fullxts_aes_decrypt,
+};
+
 static int ctr_aes_set_key(struct crypto_skcipher *tfm, const u8 *in_key,
 			   unsigned int key_len)
 {
@@ -955,7 +1062,7 @@ static struct aead_alg gcm_aes_aead = {
 };
 
 static struct crypto_alg *aes_s390_alg;
-static struct skcipher_alg *aes_s390_skcipher_algs[4];
+static struct skcipher_alg *aes_s390_skcipher_algs[5];
 static int aes_s390_skciphers_num;
 static struct aead_alg *aes_s390_aead_alg;
 
@@ -1012,6 +1119,13 @@ static int __init aes_s390_init(void)
 			goto out_err;
 	}
 
+	if (cpacf_test_func(&km_functions, CPACF_KM_XTS_128_FULL) ||
+	    cpacf_test_func(&km_functions, CPACF_KM_XTS_256_FULL)) {
+		ret = aes_s390_register_skcipher(&fullxts_aes_alg);
+		if (ret)
+			goto out_err;
+	}
+
 	if (cpacf_test_func(&km_functions, CPACF_KM_XTS_128) ||
 	    cpacf_test_func(&km_functions, CPACF_KM_XTS_256)) {
 		ret = aes_s390_register_skcipher(&xts_aes_alg);

arch/s390/include/asm/cpacf.h

@@ -54,6 +54,8 @@
 #define CPACF_KM_XTS_256	0x34
 #define CPACF_KM_PXTS_128	0x3a
 #define CPACF_KM_PXTS_256	0x3c
+#define CPACF_KM_XTS_128_FULL	0x52
+#define CPACF_KM_XTS_256_FULL	0x54
 
 /*
  * Function codes for the KMC (CIPHER MESSAGE WITH CHAINING)