crypto: null - Add default null skcipher

This patch adds a default null skcipher for users such as gcm
to perform copies on SG lists.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

diff --git a/crypto/crypto_null.c b/crypto/crypto_null.c
index a203191..941c9a4 100644 (file)
--- a/crypto/crypto_null.c
+++ b/crypto/crypto_null.c
@@ -25,6 +25,10 @@
 #include <linux/mm.h>
 #include <linux/string.h>
 
+static DEFINE_MUTEX(crypto_default_null_skcipher_lock);
+static struct crypto_blkcipher *crypto_default_null_skcipher;
+static int crypto_default_null_skcipher_refcnt;
+
 static int null_compress(struct crypto_tfm *tfm, const u8 *src,
                         unsigned int slen, u8 *dst, unsigned int *dlen)
 {
@@ -149,6 +153,41 @@ MODULE_ALIAS_CRYPTO("compress_null");
 MODULE_ALIAS_CRYPTO("digest_null");
 MODULE_ALIAS_CRYPTO("cipher_null");
 
+struct crypto_blkcipher *crypto_get_default_null_skcipher(void)
+{
+       struct crypto_blkcipher *tfm;
+
+       mutex_lock(&crypto_default_null_skcipher_lock);
+       tfm = crypto_default_null_skcipher;
+
+       if (!tfm) {
+               tfm = crypto_alloc_blkcipher("ecb(cipher_null)", 0, 0);
+               if (IS_ERR(tfm))
+                       goto unlock;
+
+               crypto_default_null_skcipher = tfm;
+       }
+
+       crypto_default_null_skcipher_refcnt++;
+
+unlock:
+       mutex_unlock(&crypto_default_null_skcipher_lock);
+
+       return tfm;
+}
+EXPORT_SYMBOL_GPL(crypto_get_default_null_skcipher);
+
+void crypto_put_default_null_skcipher(void)
+{
+       mutex_lock(&crypto_default_null_skcipher_lock);
+       if (!--crypto_default_null_skcipher_refcnt) {
+               crypto_free_blkcipher(crypto_default_null_skcipher);
+               crypto_default_null_skcipher = NULL;
+       }
+       mutex_unlock(&crypto_default_null_skcipher_lock);
+}
+EXPORT_SYMBOL_GPL(crypto_put_default_null_skcipher);
+
 static int __init crypto_null_mod_init(void)
 {
        int ret = 0;

diff --git a/include/crypto/null.h b/include/crypto/null.h
index b7c864c..06dc30d 100644 (file)
--- a/include/crypto/null.h
+++ b/include/crypto/null.h
@@ -8,4 +8,7 @@
 #define NULL_DIGEST_SIZE       0
 #define NULL_IV_SIZE           0
 
+struct crypto_blkcipher *crypto_get_default_null_skcipher(void);
+void crypto_put_default_null_skcipher(void);
+
 #endif