crypto: arm64/aes-ce-gcm - implement 2-way aggregation

Implement a faster version of the GHASH transform which amortizes
the reduction modulo the characteristic polynomial across two
input blocks at a time.

On a Cortex-A53, the gcm(aes) performance increases 24%, from
3.0 cycles per byte to 2.4 cpb for large input sizes.
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

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

@@ -290,6 +290,10 @@ ENDPROC(pmull_ghash_update_p8)
 	KS1		.req	v9
 	INP0		.req	v10
 	INP1		.req	v11
+	HH		.req	v12
+	XL2		.req	v13
+	XM2		.req	v14
+	XH2		.req	v15
 
 	.macro		load_round_keys, rounds, rk
 	cmp		\rounds, #12
@@ -323,6 +327,7 @@ ENDPROC(pmull_ghash_update_p8)
 	.endm
 
 	.macro		pmull_gcm_do_crypt, enc
+	ld1		{HH.2d}, [x4], #16
 	ld1		{SHASH.2d}, [x4]
 	ld1		{XL.2d}, [x1]
 	ldr		x8, [x5, #8]			// load lower counter
@@ -330,10 +335,11 @@ ENDPROC(pmull_ghash_update_p8)
 	load_round_keys	w7, x6
 
 	movi		MASK.16b, #0xe1
-	ext		SHASH2.16b, SHASH.16b, SHASH.16b, #8
+	trn1		SHASH2.2d, SHASH.2d, HH.2d
+	trn2		T1.2d, SHASH.2d, HH.2d
 CPU_LE(	rev		x8, x8		)
 	shl		MASK.2d, MASK.2d, #57
-	eor		SHASH2.16b, SHASH2.16b, SHASH.16b
+	eor		SHASH2.16b, SHASH2.16b, T1.16b
 
 	.if		\enc == 1
 	ldr		x10, [sp]
@@ -358,116 +364,82 @@ CPU_LE(	rev		x8, x8		)
 	ins		KS0.d[1], x9			// set lower counter
 	ins		KS1.d[1], x11
 
-	rev64		T1.16b, INP0.16b
+	rev64		T1.16b, INP1.16b
 
 	cmp		w7, #12
 	b.ge		2f				// AES-192/256?
 
 1:	enc_round	KS0, v21
-
-	ext		T2.16b, XL.16b, XL.16b, #8
 	ext		IN1.16b, T1.16b, T1.16b, #8
 
 	enc_round	KS1, v21
-
-	eor		T1.16b, T1.16b, T2.16b
-	eor		XL.16b, XL.16b, IN1.16b
+	pmull2		XH2.1q, SHASH.2d, IN1.2d	// a1 * b1
 
 	enc_round	KS0, v22
-
-	pmull2		XH.1q, SHASH.2d, XL.2d		// a1 * b1
-	eor		T1.16b, T1.16b, XL.16b
+	eor		T1.16b, T1.16b, IN1.16b
 
 	enc_round	KS1, v22
-
-	pmull		XL.1q, SHASH.1d, XL.1d		// a0 * b0
-	pmull		XM.1q, SHASH2.1d, T1.1d		// (a1 + a0)(b1 + b0)
+	pmull		XL2.1q, SHASH.1d, IN1.1d	// a0 * b0
 
 	enc_round	KS0, v23
-
-	ext		T1.16b, XL.16b, XH.16b, #8
-	eor		T2.16b, XL.16b, XH.16b
-	eor		XM.16b, XM.16b, T1.16b
+	pmull		XM2.1q, SHASH2.1d, T1.1d	// (a1 + a0)(b1 + b0)
 
 	enc_round	KS1, v23
-
-	eor		XM.16b, XM.16b, T2.16b
-	pmull		T2.1q, XL.1d, MASK.1d
+	rev64		T1.16b, INP0.16b
+	ext		T2.16b, XL.16b, XL.16b, #8
 
 	enc_round	KS0, v24
-
-	mov		XH.d[0], XM.d[1]
-	mov		XM.d[1], XL.d[0]
+	ext		IN1.16b, T1.16b, T1.16b, #8
+	eor		T1.16b, T1.16b, T2.16b
 
 	enc_round	KS1, v24
-
-	eor		XL.16b, XM.16b, T2.16b
+	eor		XL.16b, XL.16b, IN1.16b
 
 	enc_round	KS0, v25
-
-	ext		T2.16b, XL.16b, XL.16b, #8
+	eor		T1.16b, T1.16b, XL.16b
 
 	enc_round	KS1, v25
-
-	pmull		XL.1q, XL.1d, MASK.1d
-	eor		T2.16b, T2.16b, XH.16b
+	pmull2		XH.1q, HH.2d, XL.2d		// a1 * b1
 
 	enc_round	KS0, v26
-
-	eor		XL.16b, XL.16b, T2.16b
-	rev64		T1.16b, INP1.16b
+	pmull		XL.1q, HH.1d, XL.1d		// a0 * b0
 
 	enc_round	KS1, v26
-
-	ext		T2.16b, XL.16b, XL.16b, #8
-	ext		IN1.16b, T1.16b, T1.16b, #8
+	pmull2		XM.1q, SHASH2.2d, T1.2d		// (a1 + a0)(b1 + b0)
 
 	enc_round	KS0, v27
-
-	eor		T1.16b, T1.16b, T2.16b
-	eor		XL.16b, XL.16b, IN1.16b
+	eor		XL.16b, XL.16b, XL2.16b
+	eor		XH.16b, XH.16b, XH2.16b
 
 	enc_round	KS1, v27
-
-	pmull2		XH.1q, SHASH.2d, XL.2d		// a1 * b1
-	eor		T1.16b, T1.16b, XL.16b
+	eor		XM.16b, XM.16b, XM2.16b
+	ext		T1.16b, XL.16b, XH.16b, #8
 
 	enc_round	KS0, v28
-
-	pmull		XL.1q, SHASH.1d, XL.1d		// a0 * b0
-	pmull		XM.1q, SHASH2.1d, T1.1d		// (a1 + a0)(b1 + b0)
-
-	enc_round	KS1, v28
-
-	ext		T1.16b, XL.16b, XH.16b, #8
 	eor		T2.16b, XL.16b, XH.16b
 	eor		XM.16b, XM.16b, T1.16b
 
-	enc_round	KS0, v29
-
+	enc_round	KS1, v28
 	eor		XM.16b, XM.16b, T2.16b
+
+	enc_round	KS0, v29
 	pmull		T2.1q, XL.1d, MASK.1d
 
 	enc_round	KS1, v29
-
 	mov		XH.d[0], XM.d[1]
 	mov		XM.d[1], XL.d[0]
 
 	aese		KS0.16b, v30.16b
-
 	eor		XL.16b, XM.16b, T2.16b
 
 	aese		KS1.16b, v30.16b
-
 	ext		T2.16b, XL.16b, XL.16b, #8
 
 	eor		KS0.16b, KS0.16b, v31.16b
-
 	pmull		XL.1q, XL.1d, MASK.1d
 	eor		T2.16b, T2.16b, XH.16b
 
 	eor		KS1.16b, KS1.16b, v31.16b
-
 	eor		XL.16b, XL.16b, T2.16b
 
 	.if		\enc == 0

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

@@ -46,6 +46,7 @@ struct ghash_desc_ctx {
 
 struct gcm_aes_ctx {
 	struct crypto_aes_ctx	aes_key;
+	u64			h2[2];
 	struct ghash_key	ghash_key;
 };
 
@@ -62,12 +63,11 @@ static void (*pmull_ghash_update)(int blocks, u64 dg[], const char *src,
 				  const char *head);
 
 asmlinkage void pmull_gcm_encrypt(int blocks, u64 dg[], u8 dst[],
-				  const u8 src[], struct ghash_key const *k,
-				  u8 ctr[], u32 const rk[], int rounds,
-				  u8 ks[]);
+				  const u8 src[], u64 const *k, u8 ctr[],
+				  u32 const rk[], int rounds, u8 ks[]);
 
 asmlinkage void pmull_gcm_decrypt(int blocks, u64 dg[], u8 dst[],
-				  const u8 src[], struct ghash_key const *k,
+				  const u8 src[], u64 const *k,
 				  u8 ctr[], u32 const rk[], int rounds);
 
 asmlinkage void pmull_gcm_encrypt_block(u8 dst[], u8 const src[],
@@ -232,7 +232,8 @@ 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];
+	be128 h1, h2;
+	u8 *key = (u8 *)&h1;
 	int ret;
 
 	ret = crypto_aes_expand_key(&ctx->aes_key, inkey, keylen);
@@ -244,7 +245,19 @@ static int gcm_setkey(struct crypto_aead *tfm, const u8 *inkey,
 	__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));
+	__ghash_setkey(&ctx->ghash_key, key, sizeof(be128));
+
+	/* calculate H^2 (used for 2-way aggregation) */
+	h2 = h1;
+	gf128mul_lle(&h2, &h1);
+
+	ctx->h2[0] = (be64_to_cpu(h2.b) << 1) | (be64_to_cpu(h2.a) >> 63);
+	ctx->h2[1] = (be64_to_cpu(h2.a) << 1) | (be64_to_cpu(h2.b) >> 63);
+
+	if (be64_to_cpu(h2.a) >> 63)
+		ctx->h2[1] ^= 0xc200000000000000UL;
+
+	return 0;
 }
 
 static int gcm_setauthsize(struct crypto_aead *tfm, unsigned int authsize)
@@ -378,9 +391,8 @@ static int gcm_encrypt(struct aead_request *req)
 
 			kernel_neon_begin();
 			pmull_gcm_encrypt(blocks, dg, walk.dst.virt.addr,
-					  walk.src.virt.addr, &ctx->ghash_key,
-					  iv, ctx->aes_key.key_enc, nrounds,
-					  ks);
+					  walk.src.virt.addr, ctx->h2, iv,
+					  ctx->aes_key.key_enc, nrounds, ks);
 			kernel_neon_end();
 
 			err = skcipher_walk_done(&walk,
@@ -486,8 +498,8 @@ static int gcm_decrypt(struct aead_request *req)
 
 			kernel_neon_begin();
 			pmull_gcm_decrypt(blocks, dg, walk.dst.virt.addr,
-					  walk.src.virt.addr, &ctx->ghash_key,
-					  iv, ctx->aes_key.key_enc, nrounds);
+					  walk.src.virt.addr, ctx->h2, iv,
+					  ctx->aes_key.key_enc, nrounds);
 			kernel_neon_end();
 
 			err = skcipher_walk_done(&walk,