crypto: shash - introduce crypto_grab_shash()

Currently, shash spawns are initialized by using shash_attr_alg() or
crypto_alg_mod_lookup() to look up the shash algorithm, then calling
crypto_init_shash_spawn().

This is different from how skcipher, aead, and akcipher spawns are
initialized (they use crypto_grab_*()), and for no good reason.  This
difference introduces unnecessary complexity.

The crypto_grab_*() functions used to have some problems, like not
holding a reference to the algorithm and requiring the caller to
initialize spawn->base.inst.  But those problems are fixed now.

So, let's introduce crypto_grab_shash() so that we can convert all
templates to the same way of initializing their spawns.
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

crypto/shash.c

@@ -469,6 +469,15 @@ static const struct crypto_type crypto_shash_type = {
 	.tfmsize = offsetof(struct crypto_shash, base),
 };
 
+int crypto_grab_shash(struct crypto_shash_spawn *spawn,
+		      struct crypto_instance *inst,
+		      const char *name, u32 type, u32 mask)
+{
+	spawn->base.frontend = &crypto_shash_type;
+	return crypto_grab_spawn(&spawn->base, inst, name, type, mask);
+}
+EXPORT_SYMBOL_GPL(crypto_grab_shash);
+
 struct crypto_shash *crypto_alloc_shash(const char *alg_name, u32 type,
 					u32 mask)
 {

include/crypto/internal/hash.h

@@ -128,11 +128,21 @@ int crypto_init_shash_spawn(struct crypto_shash_spawn *spawn,
 			    struct shash_alg *alg,
 			    struct crypto_instance *inst);
 
+int crypto_grab_shash(struct crypto_shash_spawn *spawn,
+		      struct crypto_instance *inst,
+		      const char *name, u32 type, u32 mask);
+
 static inline void crypto_drop_shash(struct crypto_shash_spawn *spawn)
 {
 	crypto_drop_spawn(&spawn->base);
 }
 
+static inline struct shash_alg *crypto_spawn_shash_alg(
+	struct crypto_shash_spawn *spawn)
+{
+	return __crypto_shash_alg(spawn->base.alg);
+}
+
 struct shash_alg *shash_attr_alg(struct rtattr *rta, u32 type, u32 mask);
 
 int shash_ahash_update(struct ahash_request *req, struct shash_desc *desc);