[CRYPTO] api: Added crypto_alloc_base

Up until now all crypto transforms have been of the same type, struct
crypto_tfm, regardless of whether they are ciphers, digests, or other
types.  As a result of that, we check the types at run-time before
each crypto operation.

This is rather cumbersome.  We could instead use different C types for
each crypto type to ensure that the correct types are used at compile
time.  That is, we would have crypto_cipher/crypto_digest instead of
just crypto_tfm.  The appropriate type would then be required for the
actual operations such as crypto_digest_digest.

Now that we have the type/mask fields when looking up algorithms, it
is easy to request for an algorithm of the precise type that the user
wants.  However, crypto_alloc_tfm currently does not expose these new
attributes.

This patch introduces the function crypto_alloc_base which will carry
these new parameters.  It will be renamed to crypto_alloc_tfm once
all existing users have been converted.

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

1 files changed, 60 insertions, 0 deletions

diff --git a/crypto/api.c b/crypto/api.c
index 1e4692a13474..bc4b7901acdf 100644
--- a/crypto/api.c
+++ b/crypto/api.c
@@ -372,6 +372,66 @@ struct crypto_tfm *crypto_alloc_tfm(const char *name, u32 flags)
         return tfm;
 }
 
+/*
+ *      crypto_alloc_base - Locate algorithm and allocate transform
+ *      @alg_name: Name of algorithm
+ *      @type: Type of algorithm
+ *      @mask: Mask for type comparison
+ *
+ *      crypto_alloc_base() will first attempt to locate an already loaded
+ *      algorithm.  If that fails and the kernel supports dynamically loadable
+ *      modules, it will then attempt to load a module of the same name or
+ *      alias.  If that fails it will send a query to any loaded crypto manager
+ *      to construct an algorithm on the fly.  A refcount is grabbed on the
+ *      algorithm which is then associated with the new transform.
+ *
+ *      The returned transform is of a non-determinate type.  Most people
+ *      should use one of the more specific allocation functions such as
+ *      crypto_alloc_blkcipher.
+ *
+ *      In case of error the return value is an error pointer.
+ */
+struct crypto_tfm *crypto_alloc_base(const char *alg_name, u32 type, u32 mask)
+{
+        struct crypto_tfm *tfm;
+        int err;
+
+        for (;;) {
+                struct crypto_alg *alg;
+
+                alg = crypto_alg_mod_lookup(alg_name, type, mask);
+                err = PTR_ERR(alg);
+                tfm = ERR_PTR(err);
+                if (IS_ERR(alg))
+                        goto err;
+
+                tfm = __crypto_alloc_tfm(alg, 0);
+                if (!IS_ERR(tfm))
+                        break;
+
+                crypto_mod_put(alg);
+                err = PTR_ERR(tfm);
+
+err:
+                if (err != -EAGAIN)
+                        break;
+                if (signal_pending(current)) {
+                        err = -EINTR;
+                        break;
+                }
+        };
+
+        return tfm;
+}
+EXPORT_SYMBOL_GPL(crypto_alloc_base);
+ 
+/*
+ *      crypto_free_tfm - Free crypto transform
+ *      @tfm: Transform to free
+ *
+ *      crypto_free_tfm() frees up the transform and any associated resources,
+ *      then drops the refcount on the associated algorithm.
+ */
 void crypto_free_tfm(struct crypto_tfm *tfm)
 {
         struct crypto_alg *alg;