crypto: arm64/gcm - implement native driver using v8 Crypto Extensions

Currently, the AES-GCM implementation for arm64 systems that support the
ARMv8 Crypto Extensions is based on the generic GCM module, which combines
the AES-CTR implementation using AES instructions with the PMULL based
GHASH driver. This is suboptimal, given the fact that the input data needs
to be loaded twice, once for the encryption and again for the MAC
calculation.

On Cortex-A57 (r1p2) and other recent cores that implement micro-op fusing
for the AES instructions, AES executes at less than 1 cycle per byte, which
means that any cycles wasted on loading the data twice hurt even more.

So implement a new GCM driver that combines the AES and PMULL instructions
at the block level. This improves performance on Cortex-A57 by ~37% (from
3.5 cpb to 2.6 cpb)
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

arch/arm64/crypto/Kconfig

@@ -29,10 +29,12 @@ config CRYPTO_SHA2_ARM64_CE
 	select CRYPTO_SHA256_ARM64
 
 config CRYPTO_GHASH_ARM64_CE
-	tristate "GHASH (for GCM chaining mode) using ARMv8 Crypto Extensions"
+	tristate "GHASH/AES-GCM using ARMv8 Crypto Extensions"
 	depends on KERNEL_MODE_NEON
 	select CRYPTO_HASH
 	select CRYPTO_GF128MUL
+	select CRYPTO_AES
+	select CRYPTO_AES_ARM64
 
 config CRYPTO_CRCT10DIF_ARM64_CE
 	tristate "CRCT10DIF digest algorithm using PMULL instructions"

arch/arm64/crypto/ghash-ce-core.S

@@ -77,3 +77,178 @@ CPU_LE(	rev64		T1.16b, T1.16b	)
 	st1		{XL.2d}, [x1]
 	ret
 ENDPROC(pmull_ghash_update)
+
+	KS		.req	v8
+	CTR		.req	v9
+	INP		.req	v10
+
+	.macro		load_round_keys, rounds, rk
+	cmp		\rounds, #12
+	blo		2222f		/* 128 bits */
+	beq		1111f		/* 192 bits */
+	ld1		{v17.4s-v18.4s}, [\rk], #32
+1111:	ld1		{v19.4s-v20.4s}, [\rk], #32
+2222:	ld1		{v21.4s-v24.4s}, [\rk], #64
+	ld1		{v25.4s-v28.4s}, [\rk], #64
+	ld1		{v29.4s-v31.4s}, [\rk]
+	.endm
+
+	.macro		enc_round, state, key
+	aese		\state\().16b, \key\().16b
+	aesmc		\state\().16b, \state\().16b
+	.endm
+
+	.macro		enc_block, state, rounds
+	cmp		\rounds, #12
+	b.lo		2222f		/* 128 bits */
+	b.eq		1111f		/* 192 bits */
+	enc_round	\state, v17
+	enc_round	\state, v18
+1111:	enc_round	\state, v19
+	enc_round	\state, v20
+2222:	.irp		key, v21, v22, v23, v24, v25, v26, v27, v28, v29
+	enc_round	\state, \key
+	.endr
+	aese		\state\().16b, v30.16b
+	eor		\state\().16b, \state\().16b, v31.16b
+	.endm
+
+	.macro		pmull_gcm_do_crypt, enc
+	ld1		{SHASH.2d}, [x4]
+	ld1		{XL.2d}, [x1]
+	ldr		x8, [x5, #8]			// load lower counter
+
+	movi		MASK.16b, #0xe1
+	ext		SHASH2.16b, SHASH.16b, SHASH.16b, #8
+CPU_LE(	rev		x8, x8		)
+	shl		MASK.2d, MASK.2d, #57
+	eor		SHASH2.16b, SHASH2.16b, SHASH.16b
+
+	.if		\enc == 1
+	ld1		{KS.16b}, [x7]
+	.endif
+
+0:	ld1		{CTR.8b}, [x5]			// load upper counter
+	ld1		{INP.16b}, [x3], #16
+	rev		x9, x8
+	add		x8, x8, #1
+	sub		w0, w0, #1
+	ins		CTR.d[1], x9			// set lower counter
+
+	.if		\enc == 1
+	eor		INP.16b, INP.16b, KS.16b	// encrypt input
+	st1		{INP.16b}, [x2], #16
+	.endif
+
+	rev64		T1.16b, INP.16b
+
+	cmp		w6, #12
+	b.ge		2f				// AES-192/256?
+
+1:	enc_round	CTR, v21
+
+	ext		T2.16b, XL.16b, XL.16b, #8
+	ext		IN1.16b, T1.16b, T1.16b, #8
+
+	enc_round	CTR, v22
+
+	eor		T1.16b, T1.16b, T2.16b
+	eor		XL.16b, XL.16b, IN1.16b
+
+	enc_round	CTR, v23
+
+	pmull2		XH.1q, SHASH.2d, XL.2d		// a1 * b1
+	eor		T1.16b, T1.16b, XL.16b
+
+	enc_round	CTR, v24
+
+	pmull		XL.1q, SHASH.1d, XL.1d		// a0 * b0
+	pmull		XM.1q, SHASH2.1d, T1.1d		// (a1 + a0)(b1 + b0)
+
+	enc_round	CTR, v25
+
+	ext		T1.16b, XL.16b, XH.16b, #8
+	eor		T2.16b, XL.16b, XH.16b
+	eor		XM.16b, XM.16b, T1.16b
+
+	enc_round	CTR, v26
+
+	eor		XM.16b, XM.16b, T2.16b
+	pmull		T2.1q, XL.1d, MASK.1d
+
+	enc_round	CTR, v27
+
+	mov		XH.d[0], XM.d[1]
+	mov		XM.d[1], XL.d[0]
+
+	enc_round	CTR, v28
+
+	eor		XL.16b, XM.16b, T2.16b
+
+	enc_round	CTR, v29
+
+	ext		T2.16b, XL.16b, XL.16b, #8
+
+	aese		CTR.16b, v30.16b
+
+	pmull		XL.1q, XL.1d, MASK.1d
+	eor		T2.16b, T2.16b, XH.16b
+
+	eor		KS.16b, CTR.16b, v31.16b
+
+	eor		XL.16b, XL.16b, T2.16b
+
+	.if		\enc == 0
+	eor		INP.16b, INP.16b, KS.16b
+	st1		{INP.16b}, [x2], #16
+	.endif
+
+	cbnz		w0, 0b
+
+CPU_LE(	rev		x8, x8		)
+	st1		{XL.2d}, [x1]
+	str		x8, [x5, #8]			// store lower counter
+
+	.if		\enc == 1
+	st1		{KS.16b}, [x7]
+	.endif
+
+	ret
+
+2:	b.eq		3f				// AES-192?
+	enc_round	CTR, v17
+	enc_round	CTR, v18
+3:	enc_round	CTR, v19
+	enc_round	CTR, v20
+	b		1b
+	.endm
+
+	/*
+	 * void pmull_gcm_encrypt(int blocks, u64 dg[], u8 dst[], const u8 src[],
+	 *			  struct ghash_key const *k, u8 ctr[],
+	 *			  int rounds, u8 ks[])
+	 */
+ENTRY(pmull_gcm_encrypt)
+	pmull_gcm_do_crypt	1
+ENDPROC(pmull_gcm_encrypt)
+
+	/*
+	 * void pmull_gcm_decrypt(int blocks, u64 dg[], u8 dst[], const u8 src[],
+	 *			  struct ghash_key const *k, u8 ctr[],
+	 *			  int rounds)
+	 */
+ENTRY(pmull_gcm_decrypt)
+	pmull_gcm_do_crypt	0
+ENDPROC(pmull_gcm_decrypt)
+
+	/*
+	 * void pmull_gcm_encrypt_block(u8 dst[], u8 src[], u8 rk[], int rounds)
+	 */
+ENTRY(pmull_gcm_encrypt_block)
+	cbz		x2, 0f
+	load_round_keys	w3, x2
+0:	ld1		{v0.16b}, [x1]
+	enc_block	v0, w3
+	st1		{v0.16b}, [x0]
+	ret
+ENDPROC(pmull_gcm_encrypt_block)

arch/arm64/crypto/ghash-ce-glue.c

@@ -11,18 +11,25 @@
 #include <asm/neon.h>
 #include <asm/simd.h>
 #include <asm/unaligned.h>
+#include <crypto/aes.h>
+#include <crypto/algapi.h>
+#include <crypto/b128ops.h>
 #include <crypto/gf128mul.h>
+#include <crypto/internal/aead.h>
 #include <crypto/internal/hash.h>
+#include <crypto/internal/skcipher.h>
+#include <crypto/scatterwalk.h>
 #include <linux/cpufeature.h>
 #include <linux/crypto.h>
 #include <linux/module.h>
 
-MODULE_DESCRIPTION("GHASH secure hash using ARMv8 Crypto Extensions");
+MODULE_DESCRIPTION("GHASH and AES-GCM using ARMv8 Crypto Extensions");
 MODULE_AUTHOR("Ard Biesheuvel <ard.biesheuvel@linaro.org>");
 MODULE_LICENSE("GPL v2");
 
 #define GHASH_BLOCK_SIZE	16
 #define GHASH_DIGEST_SIZE	16
+#define GCM_IV_SIZE		12
 
 struct ghash_key {
 	u64 a;
@@ -36,9 +43,27 @@ struct ghash_desc_ctx {
 	u32 count;
 };
 
+struct gcm_aes_ctx {
+	struct crypto_aes_ctx	aes_key;
+	struct ghash_key	ghash_key;
+};
+
 asmlinkage void pmull_ghash_update(int blocks, u64 dg[], const char *src,
 				   struct ghash_key const *k, const char *head);
 
+asmlinkage void pmull_gcm_encrypt(int blocks, u64 dg[], u8 dst[],
+				  const u8 src[], struct ghash_key const *k,
+				  u8 ctr[], int rounds, u8 ks[]);
+
+asmlinkage void pmull_gcm_decrypt(int blocks, u64 dg[], u8 dst[],
+				  const u8 src[], struct ghash_key const *k,
+				  u8 ctr[], int rounds);
+
+asmlinkage void pmull_gcm_encrypt_block(u8 dst[], u8 const src[],
+					u32 const rk[], int rounds);
+
+asmlinkage void __aes_arm64_encrypt(u32 *rk, u8 *out, const u8 *in, int rounds);
+
 static int ghash_init(struct shash_desc *desc)
 {
 	struct ghash_desc_ctx *ctx = shash_desc_ctx(desc);
@@ -130,17 +155,11 @@ static int ghash_final(struct shash_desc *desc, u8 *dst)
 	return 0;
 }
 
-static int ghash_setkey(struct crypto_shash *tfm,
+static int __ghash_setkey(struct ghash_key *key,
 			  const u8 *inkey, unsigned int keylen)
 {
-	struct ghash_key *key = crypto_shash_ctx(tfm);
 	u64 a, b;
 
-	if (keylen != GHASH_BLOCK_SIZE) {
-		crypto_shash_set_flags(tfm, CRYPTO_TFM_RES_BAD_KEY_LEN);
-		return -EINVAL;
-	}
-
 	/* needed for the fallback */
 	memcpy(&key->k, inkey, GHASH_BLOCK_SIZE);
 
@@ -157,32 +176,401 @@ static int ghash_setkey(struct crypto_shash *tfm,
 	return 0;
 }
 
+static int ghash_setkey(struct crypto_shash *tfm,
+			const u8 *inkey, unsigned int keylen)
+{
+	struct ghash_key *key = crypto_shash_ctx(tfm);
+
+	if (keylen != GHASH_BLOCK_SIZE) {
+		crypto_shash_set_flags(tfm, CRYPTO_TFM_RES_BAD_KEY_LEN);
+		return -EINVAL;
+	}
+
+	return __ghash_setkey(key, inkey, keylen);
+}
+
 static struct shash_alg ghash_alg = {
+	.base.cra_name		= "ghash",
+	.base.cra_driver_name	= "ghash-ce",
+	.base.cra_priority	= 200,
+	.base.cra_flags		= CRYPTO_ALG_TYPE_SHASH,
+	.base.cra_blocksize	= GHASH_BLOCK_SIZE,
+	.base.cra_ctxsize	= sizeof(struct ghash_key),
+	.base.cra_module	= THIS_MODULE,
+
 	.digestsize		= GHASH_DIGEST_SIZE,
 	.init			= ghash_init,
 	.update			= ghash_update,
 	.final			= ghash_final,
 	.setkey			= ghash_setkey,
 	.descsize		= sizeof(struct ghash_desc_ctx),
-	.base		= {
-		.cra_name		= "ghash",
-		.cra_driver_name	= "ghash-ce",
-		.cra_priority		= 200,
-		.cra_flags		= CRYPTO_ALG_TYPE_SHASH,
-		.cra_blocksize		= GHASH_BLOCK_SIZE,
-		.cra_ctxsize		= sizeof(struct ghash_key),
-		.cra_module		= THIS_MODULE,
-	},
+};
+
+static int num_rounds(struct crypto_aes_ctx *ctx)
+{
+	/*
+	 * # of rounds specified by AES:
+	 * 128 bit key		10 rounds
+	 * 192 bit key		12 rounds
+	 * 256 bit key		14 rounds
+	 * => n byte key	=> 6 + (n/4) rounds
+	 */
+	return 6 + ctx->key_length / 4;
+}
+
+static int gcm_setkey(struct crypto_aead *tfm, const u8 *inkey,
+		      unsigned int keylen)
+{
+	struct gcm_aes_ctx *ctx = crypto_aead_ctx(tfm);
+	u8 key[GHASH_BLOCK_SIZE];
+	int ret;
+
+	ret = crypto_aes_expand_key(&ctx->aes_key, inkey, keylen);
+	if (ret) {
+		tfm->base.crt_flags |= CRYPTO_TFM_RES_BAD_KEY_LEN;
+		return -EINVAL;
+	}
+
+	__aes_arm64_encrypt(ctx->aes_key.key_enc, key, (u8[AES_BLOCK_SIZE]){},
+			    num_rounds(&ctx->aes_key));
+
+	return __ghash_setkey(&ctx->ghash_key, key, sizeof(key));
+}
+
+static int gcm_setauthsize(struct crypto_aead *tfm, unsigned int authsize)
+{
+	switch (authsize) {
+	case 4:
+	case 8:
+	case 12 ... 16:
+		break;
+	default:
+		return -EINVAL;
+	}
+	return 0;
+}
+
+static void gcm_update_mac(u64 dg[], const u8 *src, int count, u8 buf[],
+			   int *buf_count, struct gcm_aes_ctx *ctx)
+{
+	if (*buf_count > 0) {
+		int buf_added = min(count, GHASH_BLOCK_SIZE - *buf_count);
+
+		memcpy(&buf[*buf_count], src, buf_added);
+
+		*buf_count += buf_added;
+		src += buf_added;
+		count -= buf_added;
+	}
+
+	if (count >= GHASH_BLOCK_SIZE || *buf_count == GHASH_BLOCK_SIZE) {
+		int blocks = count / GHASH_BLOCK_SIZE;
+
+		ghash_do_update(blocks, dg, src, &ctx->ghash_key,
+				*buf_count ? buf : NULL);
+
+		src += blocks * GHASH_BLOCK_SIZE;
+		count %= GHASH_BLOCK_SIZE;
+		*buf_count = 0;
+	}
+
+	if (count > 0) {
+		memcpy(buf, src, count);
+		*buf_count = count;
+	}
+}
+
+static void gcm_calculate_auth_mac(struct aead_request *req, u64 dg[])
+{
+	struct crypto_aead *aead = crypto_aead_reqtfm(req);
+	struct gcm_aes_ctx *ctx = crypto_aead_ctx(aead);
+	u8 buf[GHASH_BLOCK_SIZE];
+	struct scatter_walk walk;
+	u32 len = req->assoclen;
+	int buf_count = 0;
+
+	scatterwalk_start(&walk, req->src);
+
+	do {
+		u32 n = scatterwalk_clamp(&walk, len);
+		u8 *p;
+
+		if (!n) {
+			scatterwalk_start(&walk, sg_next(walk.sg));
+			n = scatterwalk_clamp(&walk, len);
+		}
+		p = scatterwalk_map(&walk);
+
+		gcm_update_mac(dg, p, n, buf, &buf_count, ctx);
+		len -= n;
+
+		scatterwalk_unmap(p);
+		scatterwalk_advance(&walk, n);
+		scatterwalk_done(&walk, 0, len);
+	} while (len);
+
+	if (buf_count) {
+		memset(&buf[buf_count], 0, GHASH_BLOCK_SIZE - buf_count);
+		ghash_do_update(1, dg, buf, &ctx->ghash_key, NULL);
+	}
+}
+
+static void gcm_final(struct aead_request *req, struct gcm_aes_ctx *ctx,
+		      u64 dg[], u8 tag[], int cryptlen)
+{
+	u8 mac[AES_BLOCK_SIZE];
+	u128 lengths;
+
+	lengths.a = cpu_to_be64(req->assoclen * 8);
+	lengths.b = cpu_to_be64(cryptlen * 8);
+
+	ghash_do_update(1, dg, (void *)&lengths, &ctx->ghash_key, NULL);
+
+	put_unaligned_be64(dg[1], mac);
+	put_unaligned_be64(dg[0], mac + 8);
+
+	crypto_xor(tag, mac, AES_BLOCK_SIZE);
+}
+
+static int gcm_encrypt(struct aead_request *req)
+{
+	struct crypto_aead *aead = crypto_aead_reqtfm(req);
+	struct gcm_aes_ctx *ctx = crypto_aead_ctx(aead);
+	struct skcipher_walk walk;
+	u8 iv[AES_BLOCK_SIZE];
+	u8 ks[AES_BLOCK_SIZE];
+	u8 tag[AES_BLOCK_SIZE];
+	u64 dg[2] = {};
+	int err;
+
+	if (req->assoclen)
+		gcm_calculate_auth_mac(req, dg);
+
+	memcpy(iv, req->iv, GCM_IV_SIZE);
+	put_unaligned_be32(1, iv + GCM_IV_SIZE);
+
+	if (likely(may_use_simd())) {
+		kernel_neon_begin();
+
+		pmull_gcm_encrypt_block(tag, iv, ctx->aes_key.key_enc,
+					num_rounds(&ctx->aes_key));
+		put_unaligned_be32(2, iv + GCM_IV_SIZE);
+		pmull_gcm_encrypt_block(ks, iv, NULL,
+					num_rounds(&ctx->aes_key));
+		put_unaligned_be32(3, iv + GCM_IV_SIZE);
+
+		err = skcipher_walk_aead_encrypt(&walk, req, true);
+
+		while (walk.nbytes >= AES_BLOCK_SIZE) {
+			int blocks = walk.nbytes / AES_BLOCK_SIZE;
+
+			pmull_gcm_encrypt(blocks, dg, walk.dst.virt.addr,
+					  walk.src.virt.addr, &ctx->ghash_key,
+					  iv, num_rounds(&ctx->aes_key), ks);
+
+			err = skcipher_walk_done(&walk,
+						 walk.nbytes % AES_BLOCK_SIZE);
+		}
+		kernel_neon_end();
+	} else {
+		__aes_arm64_encrypt(ctx->aes_key.key_enc, tag, iv,
+				    num_rounds(&ctx->aes_key));
+		put_unaligned_be32(2, iv + GCM_IV_SIZE);
+
+		err = skcipher_walk_aead_encrypt(&walk, req, true);
+
+		while (walk.nbytes >= AES_BLOCK_SIZE) {
+			int blocks = walk.nbytes / AES_BLOCK_SIZE;
+			u8 *dst = walk.dst.virt.addr;
+			u8 *src = walk.src.virt.addr;
+
+			do {
+				__aes_arm64_encrypt(ctx->aes_key.key_enc,
+						    ks, iv,
+						    num_rounds(&ctx->aes_key));
+				crypto_xor_cpy(dst, src, ks, AES_BLOCK_SIZE);
+				crypto_inc(iv, AES_BLOCK_SIZE);
+
+				dst += AES_BLOCK_SIZE;
+				src += AES_BLOCK_SIZE;
+			} while (--blocks > 0);
+
+			ghash_do_update(walk.nbytes / AES_BLOCK_SIZE, dg,
+					walk.dst.virt.addr, &ctx->ghash_key,
+					NULL);
+
+			err = skcipher_walk_done(&walk,
+						 walk.nbytes % AES_BLOCK_SIZE);
+		}
+		if (walk.nbytes)
+			__aes_arm64_encrypt(ctx->aes_key.key_enc, ks, iv,
+					    num_rounds(&ctx->aes_key));
+	}
+
+	/* handle the tail */
+	if (walk.nbytes) {
+		u8 buf[GHASH_BLOCK_SIZE];
+
+		crypto_xor_cpy(walk.dst.virt.addr, walk.src.virt.addr, ks,
+			       walk.nbytes);
+
+		memcpy(buf, walk.dst.virt.addr, walk.nbytes);
+		memset(buf + walk.nbytes, 0, GHASH_BLOCK_SIZE - walk.nbytes);
+		ghash_do_update(1, dg, buf, &ctx->ghash_key, NULL);
+
+		err = skcipher_walk_done(&walk, 0);
+	}
+
+	if (err)
+		return err;
+
+	gcm_final(req, ctx, dg, tag, req->cryptlen);
+
+	/* copy authtag to end of dst */
+	scatterwalk_map_and_copy(tag, req->dst, req->assoclen + req->cryptlen,
+				 crypto_aead_authsize(aead), 1);
+
+	return 0;
+}
+
+static int gcm_decrypt(struct aead_request *req)
+{
+	struct crypto_aead *aead = crypto_aead_reqtfm(req);
+	struct gcm_aes_ctx *ctx = crypto_aead_ctx(aead);
+	unsigned int authsize = crypto_aead_authsize(aead);
+	struct skcipher_walk walk;
+	u8 iv[AES_BLOCK_SIZE];
+	u8 tag[AES_BLOCK_SIZE];
+	u8 buf[GHASH_BLOCK_SIZE];
+	u64 dg[2] = {};
+	int err;
+
+	if (req->assoclen)
+		gcm_calculate_auth_mac(req, dg);
+
+	memcpy(iv, req->iv, GCM_IV_SIZE);
+	put_unaligned_be32(1, iv + GCM_IV_SIZE);
+
+	if (likely(may_use_simd())) {
+		kernel_neon_begin();
+
+		pmull_gcm_encrypt_block(tag, iv, ctx->aes_key.key_enc,
+					num_rounds(&ctx->aes_key));
+		put_unaligned_be32(2, iv + GCM_IV_SIZE);
+
+		err = skcipher_walk_aead_decrypt(&walk, req, true);
+
+		while (walk.nbytes >= AES_BLOCK_SIZE) {
+			int blocks = walk.nbytes / AES_BLOCK_SIZE;
+
+			pmull_gcm_decrypt(blocks, dg, walk.dst.virt.addr,
+					  walk.src.virt.addr, &ctx->ghash_key,
+					  iv, num_rounds(&ctx->aes_key));
+
+			err = skcipher_walk_done(&walk,
+						 walk.nbytes % AES_BLOCK_SIZE);
+		}
+		if (walk.nbytes)
+			pmull_gcm_encrypt_block(iv, iv, NULL,
+						num_rounds(&ctx->aes_key));
+
+		kernel_neon_end();
+	} else {
+		__aes_arm64_encrypt(ctx->aes_key.key_enc, tag, iv,
+				    num_rounds(&ctx->aes_key));
+		put_unaligned_be32(2, iv + GCM_IV_SIZE);
+
+		err = skcipher_walk_aead_decrypt(&walk, req, true);
+
+		while (walk.nbytes >= AES_BLOCK_SIZE) {
+			int blocks = walk.nbytes / AES_BLOCK_SIZE;
+			u8 *dst = walk.dst.virt.addr;
+			u8 *src = walk.src.virt.addr;
+
+			ghash_do_update(blocks, dg, walk.src.virt.addr,
+					&ctx->ghash_key, NULL);
+
+			do {
+				__aes_arm64_encrypt(ctx->aes_key.key_enc,
+						    buf, iv,
+						    num_rounds(&ctx->aes_key));
+				crypto_xor_cpy(dst, src, buf, AES_BLOCK_SIZE);
+				crypto_inc(iv, AES_BLOCK_SIZE);
+
+				dst += AES_BLOCK_SIZE;
+				src += AES_BLOCK_SIZE;
+			} while (--blocks > 0);
+
+			err = skcipher_walk_done(&walk,
+						 walk.nbytes % AES_BLOCK_SIZE);
+		}
+		if (walk.nbytes)
+			__aes_arm64_encrypt(ctx->aes_key.key_enc, iv, iv,
+					    num_rounds(&ctx->aes_key));
+	}
+
+	/* handle the tail */
+	if (walk.nbytes) {
+		memcpy(buf, walk.src.virt.addr, walk.nbytes);
+		memset(buf + walk.nbytes, 0, GHASH_BLOCK_SIZE - walk.nbytes);
+		ghash_do_update(1, dg, buf, &ctx->ghash_key, NULL);
+
+		crypto_xor_cpy(walk.dst.virt.addr, walk.src.virt.addr, iv,
+			       walk.nbytes);
+
+		err = skcipher_walk_done(&walk, 0);
+	}
+
+	if (err)
+		return err;
+
+	gcm_final(req, ctx, dg, tag, req->cryptlen - authsize);
+
+	/* compare calculated auth tag with the stored one */
+	scatterwalk_map_and_copy(buf, req->src,
+				 req->assoclen + req->cryptlen - authsize,
+				 authsize, 0);
+
+	if (crypto_memneq(tag, buf, authsize))
+		return -EBADMSG;
+	return 0;
+}
+
+static struct aead_alg gcm_aes_alg = {
+	.ivsize			= GCM_IV_SIZE,
+	.chunksize		= AES_BLOCK_SIZE,
+	.maxauthsize		= AES_BLOCK_SIZE,
+	.setkey			= gcm_setkey,
+	.setauthsize		= gcm_setauthsize,
+	.encrypt		= gcm_encrypt,
+	.decrypt		= gcm_decrypt,
+
+	.base.cra_name		= "gcm(aes)",
+	.base.cra_driver_name	= "gcm-aes-ce",
+	.base.cra_priority	= 300,
+	.base.cra_blocksize	= 1,
+	.base.cra_ctxsize	= sizeof(struct gcm_aes_ctx),
+	.base.cra_module	= THIS_MODULE,
 };
 
 static int __init ghash_ce_mod_init(void)
 {
-	return crypto_register_shash(&ghash_alg);
+	int ret;
+
+	ret = crypto_register_aead(&gcm_aes_alg);
+	if (ret)
+		return ret;
+
+	ret = crypto_register_shash(&ghash_alg);
+	if (ret)
+		crypto_unregister_aead(&gcm_aes_alg);
+	return ret;
 }
 
 static void __exit ghash_ce_mod_exit(void)
 {
 	crypto_unregister_shash(&ghash_alg);
+	crypto_unregister_aead(&gcm_aes_alg);
 }
 
 module_cpu_feature_match(PMULL, ghash_ce_mod_init);