crypto: skcipher - Add top-level skcipher interface

This patch introduces the crypto skcipher interface which aims
to replace both blkcipher and ablkcipher.

It's very similar to the existing ablkcipher interface.  The
main difference is the removal of the givcrypt interface.  In
order to make the transition easier for blkcipher users, there
is a helper SKCIPHER_REQUEST_ON_STACK which can be used to place
a request on the stack for synchronous transforms.

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

4 files changed, 651 insertions, 1 deletions

diff --git a/crypto/Makefile b/crypto/Makefile
index f6229aef7595..e2c59819b236 100644
--- a/crypto/Makefile
+++ b/crypto/Makefile
@@ -17,6 +17,7 @@ obj-$(CONFIG_CRYPTO_AEAD2) += aead.o
 
 crypto_blkcipher-y := ablkcipher.o
 crypto_blkcipher-y += blkcipher.o
+crypto_blkcipher-y += skcipher.o
 obj-$(CONFIG_CRYPTO_BLKCIPHER2) += crypto_blkcipher.o
 obj-$(CONFIG_CRYPTO_BLKCIPHER2) += chainiv.o
 obj-$(CONFIG_CRYPTO_BLKCIPHER2) += eseqiv.o
diff --git a/crypto/skcipher.c b/crypto/skcipher.c
new file mode 100644
index 000000000000..dd5fc1bf6447
--- /dev/null
+++ b/crypto/skcipher.c
@@ -0,0 +1,245 @@
+/*
+ * Symmetric key cipher operations.
+ *
+ * Generic encrypt/decrypt wrapper for ciphers, handles operations across
+ * multiple page boundaries by using temporary blocks.  In user context,
+ * the kernel is given a chance to schedule us once per page.
+ *
+ * Copyright (c) 2015 Herbert Xu <herbert@gondor.apana.org.au>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the Free
+ * Software Foundation; either version 2 of the License, or (at your option)
+ * any later version.
+ *
+ */
+
+#include <crypto/internal/skcipher.h>
+#include <linux/bug.h>
+#include <linux/module.h>
+
+#include "internal.h"
+
+static unsigned int crypto_skcipher_extsize(struct crypto_alg *alg)
+{
+	if (alg->cra_type == &crypto_blkcipher_type)
+		return sizeof(struct crypto_blkcipher *);
+
+	BUG_ON(alg->cra_type != &crypto_ablkcipher_type &&
+	       alg->cra_type != &crypto_givcipher_type);
+
+	return sizeof(struct crypto_ablkcipher *);
+}
+
+static int skcipher_setkey_blkcipher(struct crypto_skcipher *tfm,
+				     const u8 *key, unsigned int keylen)
+{
+	struct crypto_blkcipher **ctx = crypto_skcipher_ctx(tfm);
+	struct crypto_blkcipher *blkcipher = *ctx;
+	int err;
+
+	crypto_blkcipher_clear_flags(blkcipher, ~0);
+	crypto_blkcipher_set_flags(blkcipher, crypto_skcipher_get_flags(tfm) &
+					      CRYPTO_TFM_REQ_MASK);
+	err = crypto_blkcipher_setkey(blkcipher, key, keylen);
+	crypto_skcipher_set_flags(tfm, crypto_blkcipher_get_flags(blkcipher) &
+				       CRYPTO_TFM_RES_MASK);
+
+	return err;
+}
+
+static int skcipher_crypt_blkcipher(struct skcipher_request *req,
+				    int (*crypt)(struct blkcipher_desc *,
+						 struct scatterlist *,
+						 struct scatterlist *,
+						 unsigned int))
+{
+	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
+	struct crypto_blkcipher **ctx = crypto_skcipher_ctx(tfm);
+	struct blkcipher_desc desc = {
+		.tfm = *ctx,
+		.info = req->iv,
+		.flags = req->base.flags,
+	};
+
+
+	return crypt(&desc, req->dst, req->src, req->cryptlen);
+}
+
+static int skcipher_encrypt_blkcipher(struct skcipher_request *req)
+{
+	struct crypto_skcipher *skcipher = crypto_skcipher_reqtfm(req);
+	struct crypto_tfm *tfm = crypto_skcipher_tfm(skcipher);
+	struct blkcipher_alg *alg = &tfm->__crt_alg->cra_blkcipher;
+
+	return skcipher_crypt_blkcipher(req, alg->encrypt);
+}
+
+static int skcipher_decrypt_blkcipher(struct skcipher_request *req)
+{
+	struct crypto_skcipher *skcipher = crypto_skcipher_reqtfm(req);
+	struct crypto_tfm *tfm = crypto_skcipher_tfm(skcipher);
+	struct blkcipher_alg *alg = &tfm->__crt_alg->cra_blkcipher;
+
+	return skcipher_crypt_blkcipher(req, alg->decrypt);
+}
+
+static void crypto_exit_skcipher_ops_blkcipher(struct crypto_tfm *tfm)
+{
+	struct crypto_blkcipher **ctx = crypto_tfm_ctx(tfm);
+
+	crypto_free_blkcipher(*ctx);
+}
+
+int crypto_init_skcipher_ops_blkcipher(struct crypto_tfm *tfm)
+{
+	struct crypto_alg *calg = tfm->__crt_alg;
+	struct crypto_skcipher *skcipher = __crypto_skcipher_cast(tfm);
+	struct crypto_blkcipher **ctx = crypto_tfm_ctx(tfm);
+	struct crypto_blkcipher *blkcipher;
+	struct crypto_tfm *btfm;
+
+	if (!crypto_mod_get(calg))
+		return -EAGAIN;
+
+	btfm = __crypto_alloc_tfm(calg, CRYPTO_ALG_TYPE_BLKCIPHER,
+					CRYPTO_ALG_TYPE_MASK);
+	if (IS_ERR(btfm)) {
+		crypto_mod_put(calg);
+		return PTR_ERR(btfm);
+	}
+
+	blkcipher = __crypto_blkcipher_cast(btfm);
+	*ctx = blkcipher;
+	tfm->exit = crypto_exit_skcipher_ops_blkcipher;
+
+	skcipher->setkey = skcipher_setkey_blkcipher;
+	skcipher->encrypt = skcipher_encrypt_blkcipher;
+	skcipher->decrypt = skcipher_decrypt_blkcipher;
+
+	skcipher->ivsize = crypto_blkcipher_ivsize(blkcipher);
+
+	return 0;
+}
+
+static int skcipher_setkey_ablkcipher(struct crypto_skcipher *tfm,
+				      const u8 *key, unsigned int keylen)
+{
+	struct crypto_ablkcipher **ctx = crypto_skcipher_ctx(tfm);
+	struct crypto_ablkcipher *ablkcipher = *ctx;
+	int err;
+
+	crypto_ablkcipher_clear_flags(ablkcipher, ~0);
+	crypto_ablkcipher_set_flags(ablkcipher,
+				    crypto_skcipher_get_flags(tfm) &
+				    CRYPTO_TFM_REQ_MASK);
+	err = crypto_ablkcipher_setkey(ablkcipher, key, keylen);
+	crypto_skcipher_set_flags(tfm,
+				  crypto_ablkcipher_get_flags(ablkcipher) &
+				  CRYPTO_TFM_RES_MASK);
+
+	return err;
+}
+
+static int skcipher_crypt_ablkcipher(struct skcipher_request *req,
+				     int (*crypt)(struct ablkcipher_request *))
+{
+	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
+	struct crypto_ablkcipher **ctx = crypto_skcipher_ctx(tfm);
+	struct ablkcipher_request *subreq = skcipher_request_ctx(req);
+
+	ablkcipher_request_set_tfm(subreq, *ctx);
+	ablkcipher_request_set_callback(subreq, skcipher_request_flags(req),
+					req->base.complete, req->base.data);
+	ablkcipher_request_set_crypt(subreq, req->src, req->dst, req->cryptlen,
+				     req->iv);
+
+	return crypt(subreq);
+}
+
+static int skcipher_encrypt_ablkcipher(struct skcipher_request *req)
+{
+	struct crypto_skcipher *skcipher = crypto_skcipher_reqtfm(req);
+	struct crypto_tfm *tfm = crypto_skcipher_tfm(skcipher);
+	struct ablkcipher_alg *alg = &tfm->__crt_alg->cra_ablkcipher;
+
+	return skcipher_crypt_ablkcipher(req, alg->encrypt);
+}
+
+static int skcipher_decrypt_ablkcipher(struct skcipher_request *req)
+{
+	struct crypto_skcipher *skcipher = crypto_skcipher_reqtfm(req);
+	struct crypto_tfm *tfm = crypto_skcipher_tfm(skcipher);
+	struct ablkcipher_alg *alg = &tfm->__crt_alg->cra_ablkcipher;
+
+	return skcipher_crypt_ablkcipher(req, alg->decrypt);
+}
+
+static void crypto_exit_skcipher_ops_ablkcipher(struct crypto_tfm *tfm)
+{
+	struct crypto_ablkcipher **ctx = crypto_tfm_ctx(tfm);
+
+	crypto_free_ablkcipher(*ctx);
+}
+
+int crypto_init_skcipher_ops_ablkcipher(struct crypto_tfm *tfm)
+{
+	struct crypto_alg *calg = tfm->__crt_alg;
+	struct crypto_skcipher *skcipher = __crypto_skcipher_cast(tfm);
+	struct crypto_ablkcipher **ctx = crypto_tfm_ctx(tfm);
+	struct crypto_ablkcipher *ablkcipher;
+	struct crypto_tfm *abtfm;
+
+	if (!crypto_mod_get(calg))
+		return -EAGAIN;
+
+	abtfm = __crypto_alloc_tfm(calg, 0, 0);
+	if (IS_ERR(abtfm)) {
+		crypto_mod_put(calg);
+		return PTR_ERR(abtfm);
+	}
+
+	ablkcipher = __crypto_ablkcipher_cast(abtfm);
+	*ctx = ablkcipher;
+	tfm->exit = crypto_exit_skcipher_ops_ablkcipher;
+
+	skcipher->setkey = skcipher_setkey_ablkcipher;
+	skcipher->encrypt = skcipher_encrypt_ablkcipher;
+	skcipher->decrypt = skcipher_decrypt_ablkcipher;
+
+	skcipher->ivsize = crypto_ablkcipher_ivsize(ablkcipher);
+	skcipher->reqsize = crypto_ablkcipher_reqsize(ablkcipher) +
+			    sizeof(struct ablkcipher_request);
+
+	return 0;
+}
+
+static int crypto_skcipher_init_tfm(struct crypto_tfm *tfm)
+{
+	if (tfm->__crt_alg->cra_type == &crypto_blkcipher_type)
+		return crypto_init_skcipher_ops_blkcipher(tfm);
+
+	BUG_ON(tfm->__crt_alg->cra_type != &crypto_ablkcipher_type &&
+	       tfm->__crt_alg->cra_type != &crypto_givcipher_type);
+
+	return crypto_init_skcipher_ops_ablkcipher(tfm);
+}
+
+static const struct crypto_type crypto_skcipher_type2 = {
+	.extsize = crypto_skcipher_extsize,
+	.init_tfm = crypto_skcipher_init_tfm,
+	.maskclear = ~CRYPTO_ALG_TYPE_MASK,
+	.maskset = CRYPTO_ALG_TYPE_BLKCIPHER_MASK,
+	.type = CRYPTO_ALG_TYPE_BLKCIPHER,
+	.tfmsize = offsetof(struct crypto_skcipher, base),
+};
+
+struct crypto_skcipher *crypto_alloc_skcipher(const char *alg_name,
+					      u32 type, u32 mask)
+{
+	return crypto_alloc_tfm(alg_name, &crypto_skcipher_type2, type, mask);
+}
+EXPORT_SYMBOL_GPL(crypto_alloc_skcipher);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Symmetric key cipher type");
diff --git a/include/crypto/internal/skcipher.h b/include/crypto/internal/skcipher.h
index b3a46c515d1b..2cf7a61ece59 100644
--- a/include/crypto/internal/skcipher.h
+++ b/include/crypto/internal/skcipher.h
@@ -107,5 +107,20 @@ static inline u32 ablkcipher_request_flags(struct ablkcipher_request *req)
 	return req->base.flags;
 }
 
+static inline void *crypto_skcipher_ctx(struct crypto_skcipher *tfm)
+{
+	return crypto_tfm_ctx(&tfm->base);
+}
+
+static inline void *skcipher_request_ctx(struct skcipher_request *req)
+{
+	return req->__ctx;
+}
+
+static inline u32 skcipher_request_flags(struct skcipher_request *req)
+{
+	return req->base.flags;
+}
+
 #endif	/* _CRYPTO_INTERNAL_SKCIPHER_H */
 
diff --git a/include/crypto/skcipher.h b/include/crypto/skcipher.h
index 07d245f073d1..d8dd41fb034f 100644
--- a/include/crypto/skcipher.h
+++ b/include/crypto/skcipher.h
@@ -1,7 +1,7 @@
 /*
  * Symmetric key ciphers.
  * 
- * Copyright (c) 2007 Herbert Xu <herbert@gondor.apana.org.au>
+ * Copyright (c) 2007-2015 Herbert Xu <herbert@gondor.apana.org.au>
  *
  * This program is free software; you can redistribute it and/or modify it
  * under the terms of the GNU General Public License as published by the Free
@@ -18,6 +18,28 @@
 #include <linux/slab.h>
 
 /**
+ *	struct skcipher_request - Symmetric key cipher request
+ *	@cryptlen: Number of bytes to encrypt or decrypt
+ *	@iv: Initialisation Vector
+ *	@src: Source SG list
+ *	@dst: Destination SG list
+ *	@base: Underlying async request request
+ *	@__ctx: Start of private context data
+ */
+struct skcipher_request {
+	unsigned int cryptlen;
+
+	u8 *iv;
+
+	struct scatterlist *src;
+	struct scatterlist *dst;
+
+	struct crypto_async_request base;
+
+	void *__ctx[] CRYPTO_MINALIGN_ATTR;
+};
+
+/**
  *	struct skcipher_givcrypt_request - Crypto request with IV generation
  *	@seq: Sequence number for IV generation
  *	@giv: Space for generated IV
@@ -30,6 +52,23 @@ struct skcipher_givcrypt_request {
 	struct ablkcipher_request creq;
 };
 
+struct crypto_skcipher {
+	int (*setkey)(struct crypto_skcipher *tfm, const u8 *key,
+	              unsigned int keylen);
+	int (*encrypt)(struct skcipher_request *req);
+	int (*decrypt)(struct skcipher_request *req);
+
+	unsigned int ivsize;
+	unsigned int reqsize;
+
+	struct crypto_tfm base;
+};
+
+#define SKCIPHER_REQUEST_ON_STACK(name, tfm) \
+	char __##name##_desc[sizeof(struct skcipher_request) + \
+		crypto_skcipher_reqsize(tfm)] CRYPTO_MINALIGN_ATTR; \
+	struct skcipher_request *name = (void *)__##name##_desc
+
 static inline struct crypto_ablkcipher *skcipher_givcrypt_reqtfm(
 	struct skcipher_givcrypt_request *req)
 {
@@ -106,5 +145,355 @@ static inline void skcipher_givcrypt_set_giv(
 	req->seq = seq;
 }
 
+/**
+ * DOC: Symmetric Key Cipher API
+ *
+ * Symmetric key cipher API is used with the ciphers of type
+ * CRYPTO_ALG_TYPE_SKCIPHER (listed as type "skcipher" in /proc/crypto).
+ *
+ * Asynchronous cipher operations imply that the function invocation for a
+ * cipher request returns immediately before the completion of the operation.
+ * The cipher request is scheduled as a separate kernel thread and therefore
+ * load-balanced on the different CPUs via the process scheduler. To allow
+ * the kernel crypto API to inform the caller about the completion of a cipher
+ * request, the caller must provide a callback function. That function is
+ * invoked with the cipher handle when the request completes.
+ *
+ * To support the asynchronous operation, additional information than just the
+ * cipher handle must be supplied to the kernel crypto API. That additional
+ * information is given by filling in the skcipher_request data structure.
+ *
+ * For the symmetric key cipher API, the state is maintained with the tfm
+ * cipher handle. A single tfm can be used across multiple calls and in
+ * parallel. For asynchronous block cipher calls, context data supplied and
+ * only used by the caller can be referenced the request data structure in
+ * addition to the IV used for the cipher request. The maintenance of such
+ * state information would be important for a crypto driver implementer to
+ * have, because when calling the callback function upon completion of the
+ * cipher operation, that callback function may need some information about
+ * which operation just finished if it invoked multiple in parallel. This
+ * state information is unused by the kernel crypto API.
+ */
+
+static inline struct crypto_skcipher *__crypto_skcipher_cast(
+	struct crypto_tfm *tfm)
+{
+	return container_of(tfm, struct crypto_skcipher, base);
+}
+
+/**
+ * crypto_alloc_skcipher() - allocate symmetric key cipher handle
+ * @alg_name: is the cra_name / name or cra_driver_name / driver name of the
+ *	      skcipher cipher
+ * @type: specifies the type of the cipher
+ * @mask: specifies the mask for the cipher
+ *
+ * Allocate a cipher handle for an skcipher. The returned struct
+ * crypto_skcipher is the cipher handle that is required for any subsequent
+ * API invocation for that skcipher.
+ *
+ * Return: allocated cipher handle in case of success; IS_ERR() is true in case
+ *	   of an error, PTR_ERR() returns the error code.
+ */
+struct crypto_skcipher *crypto_alloc_skcipher(const char *alg_name,
+					      u32 type, u32 mask);
+
+static inline struct crypto_tfm *crypto_skcipher_tfm(
+	struct crypto_skcipher *tfm)
+{
+	return &tfm->base;
+}
+
+/**
+ * crypto_free_skcipher() - zeroize and free cipher handle
+ * @tfm: cipher handle to be freed
+ */
+static inline void crypto_free_skcipher(struct crypto_skcipher *tfm)
+{
+	crypto_destroy_tfm(tfm, crypto_skcipher_tfm(tfm));
+}
+
+/**
+ * crypto_has_skcipher() - Search for the availability of an skcipher.
+ * @alg_name: is the cra_name / name or cra_driver_name / driver name of the
+ *	      skcipher
+ * @type: specifies the type of the cipher
+ * @mask: specifies the mask for the cipher
+ *
+ * Return: true when the skcipher is known to the kernel crypto API; false
+ *	   otherwise
+ */
+static inline int crypto_has_skcipher(const char *alg_name, u32 type,
+					u32 mask)
+{
+	return crypto_has_alg(alg_name, crypto_skcipher_type(type),
+			      crypto_skcipher_mask(mask));
+}
+
+/**
+ * crypto_skcipher_ivsize() - obtain IV size
+ * @tfm: cipher handle
+ *
+ * The size of the IV for the skcipher referenced by the cipher handle is
+ * returned. This IV size may be zero if the cipher does not need an IV.
+ *
+ * Return: IV size in bytes
+ */
+static inline unsigned int crypto_skcipher_ivsize(struct crypto_skcipher *tfm)
+{
+	return tfm->ivsize;
+}
+
+/**
+ * crypto_skcipher_blocksize() - obtain block size of cipher
+ * @tfm: cipher handle
+ *
+ * The block size for the skcipher referenced with the cipher handle is
+ * returned. The caller may use that information to allocate appropriate
+ * memory for the data returned by the encryption or decryption operation
+ *
+ * Return: block size of cipher
+ */
+static inline unsigned int crypto_skcipher_blocksize(
+	struct crypto_skcipher *tfm)
+{
+	return crypto_tfm_alg_blocksize(crypto_skcipher_tfm(tfm));
+}
+
+static inline unsigned int crypto_skcipher_alignmask(
+	struct crypto_skcipher *tfm)
+{
+	return crypto_tfm_alg_alignmask(crypto_skcipher_tfm(tfm));
+}
+
+static inline u32 crypto_skcipher_get_flags(struct crypto_skcipher *tfm)
+{
+	return crypto_tfm_get_flags(crypto_skcipher_tfm(tfm));
+}
+
+static inline void crypto_skcipher_set_flags(struct crypto_skcipher *tfm,
+					       u32 flags)
+{
+	crypto_tfm_set_flags(crypto_skcipher_tfm(tfm), flags);
+}
+
+static inline void crypto_skcipher_clear_flags(struct crypto_skcipher *tfm,
+						 u32 flags)
+{
+	crypto_tfm_clear_flags(crypto_skcipher_tfm(tfm), flags);
+}
+
+/**
+ * crypto_skcipher_setkey() - set key for cipher
+ * @tfm: cipher handle
+ * @key: buffer holding the key
+ * @keylen: length of the key in bytes
+ *
+ * The caller provided key is set for the skcipher referenced by the cipher
+ * handle.
+ *
+ * Note, the key length determines the cipher type. Many block ciphers implement
+ * different cipher modes depending on the key size, such as AES-128 vs AES-192
+ * vs. AES-256. When providing a 16 byte key for an AES cipher handle, AES-128
+ * is performed.
+ *
+ * Return: 0 if the setting of the key was successful; < 0 if an error occurred
+ */
+static inline int crypto_skcipher_setkey(struct crypto_skcipher *tfm,
+					 const u8 *key, unsigned int keylen)
+{
+	return tfm->setkey(tfm, key, keylen);
+}
+
+/**
+ * crypto_skcipher_reqtfm() - obtain cipher handle from request
+ * @req: skcipher_request out of which the cipher handle is to be obtained
+ *
+ * Return the crypto_skcipher handle when furnishing an skcipher_request
+ * data structure.
+ *
+ * Return: crypto_skcipher handle
+ */
+static inline struct crypto_skcipher *crypto_skcipher_reqtfm(
+	struct skcipher_request *req)
+{
+	return __crypto_skcipher_cast(req->base.tfm);
+}
+
+/**
+ * crypto_skcipher_encrypt() - encrypt plaintext
+ * @req: reference to the skcipher_request handle that holds all information
+ *	 needed to perform the cipher operation
+ *
+ * Encrypt plaintext data using the skcipher_request handle. That data
+ * structure and how it is filled with data is discussed with the
+ * skcipher_request_* functions.
+ *
+ * Return: 0 if the cipher operation was successful; < 0 if an error occurred
+ */
+static inline int crypto_skcipher_encrypt(struct skcipher_request *req)
+{
+	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
+
+	return tfm->encrypt(req);
+}
+
+/**
+ * crypto_skcipher_decrypt() - decrypt ciphertext
+ * @req: reference to the skcipher_request handle that holds all information
+ *	 needed to perform the cipher operation
+ *
+ * Decrypt ciphertext data using the skcipher_request handle. That data
+ * structure and how it is filled with data is discussed with the
+ * skcipher_request_* functions.
+ *
+ * Return: 0 if the cipher operation was successful; < 0 if an error occurred
+ */
+static inline int crypto_skcipher_decrypt(struct skcipher_request *req)
+{
+	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
+
+	return tfm->decrypt(req);
+}
+
+/**
+ * DOC: Symmetric Key Cipher Request Handle
+ *
+ * The skcipher_request data structure contains all pointers to data
+ * required for the symmetric key cipher operation. This includes the cipher
+ * handle (which can be used by multiple skcipher_request instances), pointer
+ * to plaintext and ciphertext, asynchronous callback function, etc. It acts
+ * as a handle to the skcipher_request_* API calls in a similar way as
+ * skcipher handle to the crypto_skcipher_* API calls.
+ */
+
+/**
+ * crypto_skcipher_reqsize() - obtain size of the request data structure
+ * @tfm: cipher handle
+ *
+ * Return: number of bytes
+ */
+static inline unsigned int crypto_skcipher_reqsize(struct crypto_skcipher *tfm)
+{
+	return tfm->reqsize;
+}
+
+/**
+ * skcipher_request_set_tfm() - update cipher handle reference in request
+ * @req: request handle to be modified
+ * @tfm: cipher handle that shall be added to the request handle
+ *
+ * Allow the caller to replace the existing skcipher handle in the request
+ * data structure with a different one.
+ */
+static inline void skcipher_request_set_tfm(struct skcipher_request *req,
+					    struct crypto_skcipher *tfm)
+{
+	req->base.tfm = crypto_skcipher_tfm(tfm);
+}
+
+static inline struct skcipher_request *skcipher_request_cast(
+	struct crypto_async_request *req)
+{
+	return container_of(req, struct skcipher_request, base);
+}
+
+/**
+ * skcipher_request_alloc() - allocate request data structure
+ * @tfm: cipher handle to be registered with the request
+ * @gfp: memory allocation flag that is handed to kmalloc by the API call.
+ *
+ * Allocate the request data structure that must be used with the skcipher
+ * encrypt and decrypt API calls. During the allocation, the provided skcipher
+ * handle is registered in the request data structure.
+ *
+ * Return: allocated request handle in case of success; IS_ERR() is true in case
+ *	   of an error, PTR_ERR() returns the error code.
+ */
+static inline struct skcipher_request *skcipher_request_alloc(
+	struct crypto_skcipher *tfm, gfp_t gfp)
+{
+	struct skcipher_request *req;
+
+	req = kmalloc(sizeof(struct skcipher_request) +
+		      crypto_skcipher_reqsize(tfm), gfp);
+
+	if (likely(req))
+		skcipher_request_set_tfm(req, tfm);
+
+	return req;
+}
+
+/**
+ * skcipher_request_free() - zeroize and free request data structure
+ * @req: request data structure cipher handle to be freed
+ */
+static inline void skcipher_request_free(struct skcipher_request *req)
+{
+	kzfree(req);
+}
+
+/**
+ * skcipher_request_set_callback() - set asynchronous callback function
+ * @req: request handle
+ * @flags: specify zero or an ORing of the flags
+ *         CRYPTO_TFM_REQ_MAY_BACKLOG the request queue may back log and
+ *	   increase the wait queue beyond the initial maximum size;
+ *	   CRYPTO_TFM_REQ_MAY_SLEEP the request processing may sleep
+ * @compl: callback function pointer to be registered with the request handle
+ * @data: The data pointer refers to memory that is not used by the kernel
+ *	  crypto API, but provided to the callback function for it to use. Here,
+ *	  the caller can provide a reference to memory the callback function can
+ *	  operate on. As the callback function is invoked asynchronously to the
+ *	  related functionality, it may need to access data structures of the
+ *	  related functionality which can be referenced using this pointer. The
+ *	  callback function can access the memory via the "data" field in the
+ *	  crypto_async_request data structure provided to the callback function.
+ *
+ * This function allows setting the callback function that is triggered once the
+ * cipher operation completes.
+ *
+ * The callback function is registered with the skcipher_request handle and
+ * must comply with the following template
+ *
+ *	void callback_function(struct crypto_async_request *req, int error)
+ */
+static inline void skcipher_request_set_callback(struct skcipher_request *req,
+						 u32 flags,
+						 crypto_completion_t compl,
+						 void *data)
+{
+	req->base.complete = compl;
+	req->base.data = data;
+	req->base.flags = flags;
+}
+
+/**
+ * skcipher_request_set_crypt() - set data buffers
+ * @req: request handle
+ * @src: source scatter / gather list
+ * @dst: destination scatter / gather list
+ * @cryptlen: number of bytes to process from @src
+ * @iv: IV for the cipher operation which must comply with the IV size defined
+ *      by crypto_skcipher_ivsize
+ *
+ * This function allows setting of the source data and destination data
+ * scatter / gather lists.
+ *
+ * For encryption, the source is treated as the plaintext and the
+ * destination is the ciphertext. For a decryption operation, the use is
+ * reversed - the source is the ciphertext and the destination is the plaintext.
+ */
+static inline void skcipher_request_set_crypt(
+	struct skcipher_request *req,
+	struct scatterlist *src, struct scatterlist *dst,
+	unsigned int cryptlen, void *iv)
+{
+	req->src = src;
+	req->dst = dst;
+	req->cryptlen = cryptlen;
+	req->iv = iv;
+}
+
 #endif	/* _CRYPTO_SKCIPHER_H */