crypto: api - Rebirth of crypto_alloc_tfm

This patch reintroduces a completely revamped crypto_alloc_tfm.
The biggest change is that we now take two crypto_type objects
when allocating a tfm, a frontend and a backend.  In fact this
simply formalises what we've been doing behind the API's back.

For example, as it stands crypto_alloc_ahash may use an
actual ahash algorithm or a crypto_hash algorithm.  Putting
this in the API allows us to do this much more cleanly.

The existing types will be converted across gradually.

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

2 files changed, 110 insertions, 0 deletions

diff --git a/crypto/api.c b/crypto/api.c
index cbaaf34..9975a7b 100644
--- a/crypto/api.c
+++ b/crypto/api.c
@@ -403,6 +403,9 @@ EXPORT_SYMBOL_GPL(__crypto_alloc_tfm);
  *	@type: Type of algorithm
  *	@mask: Mask for type comparison
  *
+ *	This function should not be used by new algorithm types.
+ *	Plesae use crypto_alloc_tfm instead.
+ *
  *	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
@@ -449,6 +452,111 @@ err:
 	return ERR_PTR(err);
 }
 EXPORT_SYMBOL_GPL(crypto_alloc_base);
+
+struct crypto_tfm *crypto_create_tfm(struct crypto_alg *alg,
+				     const struct crypto_type *frontend)
+{
+	char *mem;
+	struct crypto_tfm *tfm = NULL;
+	unsigned int tfmsize;
+	unsigned int total;
+	int err = -ENOMEM;
+
+	tfmsize = frontend->tfmsize;
+	total = tfmsize + sizeof(*tfm) + frontend->extsize(alg, frontend);
+
+	mem = kzalloc(total, GFP_KERNEL);
+	if (mem == NULL)
+		goto out_err;
+
+	tfm = (struct crypto_tfm *)(mem + tfmsize);
+	tfm->__crt_alg = alg;
+
+	err = frontend->init_tfm(tfm, frontend);
+	if (err)
+		goto out_free_tfm;
+
+	if (!tfm->exit && alg->cra_init && (err = alg->cra_init(tfm)))
+		goto cra_init_failed;
+
+	goto out;
+
+cra_init_failed:
+	crypto_exit_ops(tfm);
+out_free_tfm:
+	if (err == -EAGAIN)
+		crypto_shoot_alg(alg);
+	kfree(mem);
+out_err:
+	tfm = ERR_PTR(err);
+out:
+	return tfm;
+}
+EXPORT_SYMBOL_GPL(crypto_create_tfm);
+
+/*
+ *	crypto_alloc_tfm - Locate algorithm and allocate transform
+ *	@alg_name: Name of algorithm
+ *	@frontend: Frontend algorithm type
+ *	@type: Type of algorithm
+ *	@mask: Mask for type comparison
+ *
+ *	crypto_alloc_tfm() 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_tfm(const char *alg_name,
+				    const struct crypto_type *frontend,
+				    u32 type, u32 mask)
+{
+	struct crypto_alg *(*lookup)(const char *name, u32 type, u32 mask);
+	struct crypto_tfm *tfm;
+	int err;
+
+	type &= frontend->maskclear;
+	mask &= frontend->maskclear;
+	type |= frontend->type;
+	mask |= frontend->maskset;
+
+	lookup = frontend->lookup ?: crypto_alg_mod_lookup;
+
+	for (;;) {
+		struct crypto_alg *alg;
+
+		alg = lookup(alg_name, type, mask);
+		if (IS_ERR(alg)) {
+			err = PTR_ERR(alg);
+			goto err;
+		}
+
+		tfm = crypto_create_tfm(alg, frontend);
+		if (!IS_ERR(tfm))
+			return tfm;
+
+		crypto_mod_put(alg);
+		err = PTR_ERR(tfm);
+
+err:
+		if (err != -EAGAIN)
+			break;
+		if (signal_pending(current)) {
+			err = -EINTR;
+			break;
+		}
+	}
+
+	return ERR_PTR(err);
+}
+EXPORT_SYMBOL_GPL(crypto_alloc_tfm);
  
 /*
  *	crypto_free_tfm - Free crypto transform
diff --git a/crypto/internal.h b/crypto/internal.h
index 8ef72d7..3c19a27 100644
--- a/crypto/internal.h
+++ b/crypto/internal.h
@@ -109,6 +109,8 @@ void crypto_alg_tested(const char *name, int err);
 void crypto_shoot_alg(struct crypto_alg *alg);
 struct crypto_tfm *__crypto_alloc_tfm(struct crypto_alg *alg, u32 type,
 				      u32 mask);
+struct crypto_tfm *crypto_create_tfm(struct crypto_alg *alg,
+				     const struct crypto_type *frontend);
 
 int crypto_register_instance(struct crypto_template *tmpl,
 			     struct crypto_instance *inst);