crypto: null - Add new default null skcipher

Current the default null skcipher is actually a crypto_blkcipher.
This patch creates a synchronous crypto_skcipher version of the
null cipher which unfortunately has to settle for the name skcipher2.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

crypto/crypto_null.c

@@ -28,6 +28,8 @@
 static DEFINE_MUTEX(crypto_default_null_skcipher_lock);
 static struct crypto_blkcipher *crypto_default_null_skcipher;
 static int crypto_default_null_skcipher_refcnt;
+static struct crypto_skcipher *crypto_default_null_skcipher2;
+static int crypto_default_null_skcipher2_refcnt;
 
 static int null_compress(struct crypto_tfm *tfm, const u8 *src,
 			 unsigned int slen, u8 *dst, unsigned int *dlen)
@@ -188,6 +190,42 @@ void crypto_put_default_null_skcipher(void)
 }
 EXPORT_SYMBOL_GPL(crypto_put_default_null_skcipher);
 
+struct crypto_skcipher *crypto_get_default_null_skcipher2(void)
+{
+	struct crypto_skcipher *tfm;
+
+	mutex_lock(&crypto_default_null_skcipher_lock);
+	tfm = crypto_default_null_skcipher2;
+
+	if (!tfm) {
+		tfm = crypto_alloc_skcipher("ecb(cipher_null)",
+					    0, CRYPTO_ALG_ASYNC);
+		if (IS_ERR(tfm))
+			goto unlock;
+
+		crypto_default_null_skcipher2 = tfm;
+	}
+
+	crypto_default_null_skcipher2_refcnt++;
+
+unlock:
+	mutex_unlock(&crypto_default_null_skcipher_lock);
+
+	return tfm;
+}
+EXPORT_SYMBOL_GPL(crypto_get_default_null_skcipher2);
+
+void crypto_put_default_null_skcipher2(void)
+{
+	mutex_lock(&crypto_default_null_skcipher_lock);
+	if (!--crypto_default_null_skcipher2_refcnt) {
+		crypto_free_skcipher(crypto_default_null_skcipher2);
+		crypto_default_null_skcipher2 = NULL;
+	}
+	mutex_unlock(&crypto_default_null_skcipher_lock);
+}
+EXPORT_SYMBOL_GPL(crypto_put_default_null_skcipher2);
+
 static int __init crypto_null_mod_init(void)
 {
 	int ret = 0;

include/crypto/null.h

@@ -10,5 +10,7 @@
 
 struct crypto_blkcipher *crypto_get_default_null_skcipher(void);
 void crypto_put_default_null_skcipher(void);
+struct crypto_skcipher *crypto_get_default_null_skcipher2(void);
+void crypto_put_default_null_skcipher2(void);
 
 #endif