Subject: [PATCH v4 7/7] crypto: arm64/aes-ccm - remove non-SIMD fallback path

From: Ard Biesheuvel <[email-masked]>
Date: Wed, 19 May 2021 13:22:39 +0200

AES/CCM on arm64 is implemented as a synchronous AEAD, and so it is
guaranteed by the API that it is only invoked in task or softirq
context. Since softirqs are now only handled when the SIMD is not
being used in the task context that was interrupted to service the
softirq, we no longer need a fallback path. Let's remove it.

Signed-off-by: Ard Biesheuvel <[email-masked]>
---
 arch/arm64/crypto/aes-ce-ccm-core.S |   1 +
 arch/arm64/crypto/aes-ce-ccm-glue.c | 183 ++++++--------------
 2 files changed, 53 insertions(+), 131 deletions(-)

diff --git a/arch/arm64/crypto/aes-ce-ccm-core.S b/arch/arm64/crypto/aes-ce-ccm-core.S
index 99a028e298ed..8adff299fcd3 100644
--- a/arch/arm64/crypto/aes-ce-ccm-core.S
+++ b/arch/arm64/crypto/aes-ce-ccm-core.S
@@ -124,6 +124,7 @@ SYM_FUNC_START(ce_aes_ccm_final)
 SYM_FUNC_END(ce_aes_ccm_final)
 
 	.macro	aes_ccm_do_crypt,enc
+	cbz	x2, 5f
 	ldr	x8, [x6, #8]			/* load lower ctr */
 	ld1	{v0.16b}, [x5]			/* load mac */
 CPU_LE(	rev	x8, x8			)	/* keep swabbed ctr in reg */
diff --git a/arch/arm64/crypto/aes-ce-ccm-glue.c b/arch/arm64/crypto/aes-ce-ccm-glue.c
index f6d19b0dc893..a36df98f6fae 100644
--- a/arch/arm64/crypto/aes-ce-ccm-glue.c
+++ b/arch/arm64/crypto/aes-ce-ccm-glue.c
@@ -99,36 +99,8 @@ static int ccm_init_mac(struct aead_request *req, u8 maciv[], u32 msglen)
 static void ccm_update_mac(struct crypto_aes_ctx *key, u8 mac[], u8 const in[],
 			   u32 abytes, u32 *macp)
 {
-	if (crypto_simd_usable()) {
-		kernel_neon_begin();
-		ce_aes_ccm_auth_data(mac, in, abytes, macp, key->key_enc,
-				     num_rounds(key));
-		kernel_neon_end();
-	} else {
-		if (*macp > 0 && *macp < AES_BLOCK_SIZE) {
-			int added = min(abytes, AES_BLOCK_SIZE - *macp);
-
-			crypto_xor(&mac[*macp], in, added);
-
-			*macp += added;
-			in += added;
-			abytes -= added;
-		}
-
-		while (abytes >= AES_BLOCK_SIZE) {
-			aes_encrypt(key, mac, mac);
-			crypto_xor(mac, in, AES_BLOCK_SIZE);
-
-			in += AES_BLOCK_SIZE;
-			abytes -= AES_BLOCK_SIZE;
-		}
-
-		if (abytes > 0) {
-			aes_encrypt(key, mac, mac);
-			crypto_xor(mac, in, abytes);
-			*macp = abytes;
-		}
-	}
+	ce_aes_ccm_auth_data(mac, in, abytes, macp, key->key_enc,
+			     num_rounds(key));
 }
 
 static void ccm_calculate_auth_mac(struct aead_request *req, u8 mac[])
@@ -171,54 +143,6 @@ static void ccm_calculate_auth_mac(struct aead_request *req, u8 mac[])
 	} while (len);
 }
 
-static int ccm_crypt_fallback(struct skcipher_walk *walk, u8 mac[], u8 iv0[],
-			      struct crypto_aes_ctx *ctx, bool enc)
-{
-	u8 buf[AES_BLOCK_SIZE];
-	int err = 0;
-
-	while (walk->nbytes) {
-		int blocks = walk->nbytes / AES_BLOCK_SIZE;
-		u32 tail = walk->nbytes % AES_BLOCK_SIZE;
-		u8 *dst = walk->dst.virt.addr;
-		u8 *src = walk->src.virt.addr;
-		u32 nbytes = walk->nbytes;
-
-		if (nbytes == walk->total && tail > 0) {
-			blocks++;
-			tail = 0;
-		}
-
-		do {
-			u32 bsize = AES_BLOCK_SIZE;
-
-			if (nbytes < AES_BLOCK_SIZE)
-				bsize = nbytes;
-
-			crypto_inc(walk->iv, AES_BLOCK_SIZE);
-			aes_encrypt(ctx, buf, walk->iv);
-			aes_encrypt(ctx, mac, mac);
-			if (enc)
-				crypto_xor(mac, src, bsize);
-			crypto_xor_cpy(dst, src, buf, bsize);
-			if (!enc)
-				crypto_xor(mac, dst, bsize);
-			dst += bsize;
-			src += bsize;
-			nbytes -= bsize;
-		} while (--blocks);
-
-		err = skcipher_walk_done(walk, tail);
-	}
-
-	if (!err) {
-		aes_encrypt(ctx, buf, iv0);
-		aes_encrypt(ctx, mac, mac);
-		crypto_xor(mac, buf, AES_BLOCK_SIZE);
-	}
-	return err;
-}
-
 static int ccm_encrypt(struct aead_request *req)
 {
 	struct crypto_aead *aead = crypto_aead_reqtfm(req);
@@ -233,41 +157,40 @@ static int ccm_encrypt(struct aead_request *req)
 	if (err)
 		return err;
 
-	if (req->assoclen)
-		ccm_calculate_auth_mac(req, mac);
-
 	/* preserve the original iv for the final round */
 	memcpy(buf, req->iv, AES_BLOCK_SIZE);
 
 	err = skcipher_walk_aead_encrypt(&walk, req, false);
+	if (unlikely(err))
+		return err;
 
-	if (crypto_simd_usable()) {
-		while (walk.nbytes) {
-			u32 tail = walk.nbytes % AES_BLOCK_SIZE;
+	kernel_neon_begin();
 
-			if (walk.nbytes == walk.total)
-				tail = 0;
+	if (req->assoclen)
+		ccm_calculate_auth_mac(req, mac);
 
-			kernel_neon_begin();
-			ce_aes_ccm_encrypt(walk.dst.virt.addr,
-					   walk.src.virt.addr,
-					   walk.nbytes - tail, ctx->key_enc,
-					   num_rounds(ctx), mac, walk.iv);
-			kernel_neon_end();
+	do {
+		u32 tail = walk.nbytes % AES_BLOCK_SIZE;
 
-			err = skcipher_walk_done(&walk, tail);
-		}
-		if (!err) {
+		if (walk.nbytes == walk.total)
+			tail = 0;
+
+		ce_aes_ccm_encrypt(walk.dst.virt.addr, walk.src.virt.addr,
+				   walk.nbytes - tail, ctx->key_enc,
+				   num_rounds(ctx), mac, walk.iv);
+
+		if (walk.nbytes == walk.total)
+			ce_aes_ccm_final(mac, buf, ctx->key_enc, num_rounds(ctx));
+
+		kernel_neon_end();
+
+		err = skcipher_walk_done(&walk, tail);
+		if (unlikely(err))
+			return err;
+
+		if (unlikely(walk.nbytes))
 			kernel_neon_begin();
-			ce_aes_ccm_final(mac, buf, ctx->key_enc,
-					 num_rounds(ctx));
-			kernel_neon_end();
-		}
-	} else {
-		err = ccm_crypt_fallback(&walk, mac, buf, ctx, true);
-	}
-	if (err)
-		return err;
+	} while (walk.nbytes);
 
 	/* copy authtag to end of dst */
 	scatterwalk_map_and_copy(mac, req->dst, req->assoclen + req->cryptlen,
@@ -291,42 +214,40 @@ static int ccm_decrypt(struct aead_request *req)
 	if (err)
 		return err;
 
-	if (req->assoclen)
-		ccm_calculate_auth_mac(req, mac);
-
 	/* preserve the original iv for the final round */
 	memcpy(buf, req->iv, AES_BLOCK_SIZE);
 
 	err = skcipher_walk_aead_decrypt(&walk, req, false);
+	if (unlikely(err))
+		return err;
 
-	if (crypto_simd_usable()) {
-		while (walk.nbytes) {
-			u32 tail = walk.nbytes % AES_BLOCK_SIZE;
+	kernel_neon_begin();
 
-			if (walk.nbytes == walk.total)
-				tail = 0;
+	if (req->assoclen)
+		ccm_calculate_auth_mac(req, mac);
 
-			kernel_neon_begin();
-			ce_aes_ccm_decrypt(walk.dst.virt.addr,
-					   walk.src.virt.addr,
-					   walk.nbytes - tail, ctx->key_enc,
-					   num_rounds(ctx), mac, walk.iv);
-			kernel_neon_end();
+	do {
+		u32 tail = walk.nbytes % AES_BLOCK_SIZE;
 
-			err = skcipher_walk_done(&walk, tail);
-		}
-		if (!err) {
-			kernel_neon_begin();
-			ce_aes_ccm_final(mac, buf, ctx->key_enc,
-					 num_rounds(ctx));
-			kernel_neon_end();
-		}
-	} else {
-		err = ccm_crypt_fallback(&walk, mac, buf, ctx, false);
-	}
+		if (walk.nbytes == walk.total)
+			tail = 0;
 
-	if (err)
-		return err;
+		ce_aes_ccm_decrypt(walk.dst.virt.addr, walk.src.virt.addr,
+				   walk.nbytes - tail, ctx->key_enc,
+				   num_rounds(ctx), mac, walk.iv);
+
+		if (walk.nbytes == walk.total)
+			ce_aes_ccm_final(mac, buf, ctx->key_enc, num_rounds(ctx));
+
+		kernel_neon_end();
+
+		err = skcipher_walk_done(&walk, tail);
+		if (unlikely(err))
+			return err;
+
+		if (unlikely(walk.nbytes))
+			kernel_neon_begin();
+	} while (walk.nbytes);
 
 	/* compare calculated auth tag with the stored one */
 	scatterwalk_map_and_copy(buf, req->src,
-- 
2.20.1

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