Subject: [PATCH v4 4/7] crypto: arm64/gcm-aes-ce - remove non-SIMD fallback path

From: Ard Biesheuvel <[email-masked]>
Date: Wed, 19 May 2021 13:22:36 +0200

Now that kernel mode SIMD is guaranteed to be available when executing
in task or softirq context, we no longer need scalar fallbacks to use
when the NEON is unavailable. So get rid of them.

Signed-off-by: Ard Biesheuvel <[email-masked]>
---
 arch/arm64/crypto/ghash-ce-glue.c | 209 +++++---------------
 1 file changed, 51 insertions(+), 158 deletions(-)

diff --git a/arch/arm64/crypto/ghash-ce-glue.c b/arch/arm64/crypto/ghash-ce-glue.c
index 720cd3a58da3..15794fe21a0b 100644
--- a/arch/arm64/crypto/ghash-ce-glue.c
+++ b/arch/arm64/crypto/ghash-ce-glue.c
@@ -362,84 +362,36 @@ static int gcm_encrypt(struct aead_request *req)
 
 	err = skcipher_walk_aead_encrypt(&walk, req, false);
 
-	if (likely(crypto_simd_usable())) {
-		do {
-			const u8 *src = walk.src.virt.addr;
-			u8 *dst = walk.dst.virt.addr;
-			int nbytes = walk.nbytes;
-
-			tag = (u8 *)&lengths;
-
-			if (unlikely(nbytes > 0 && nbytes < AES_BLOCK_SIZE)) {
-				src = dst = memcpy(buf + sizeof(buf) - nbytes,
-						   src, nbytes);
-			} else if (nbytes < walk.total) {
-				nbytes &= ~(AES_BLOCK_SIZE - 1);
-				tag = NULL;
-			}
-
-			kernel_neon_begin();
-			pmull_gcm_encrypt(nbytes, dst, src, ctx->ghash_key.h,
-					  dg, iv, ctx->aes_key.key_enc, nrounds,
-					  tag);
-			kernel_neon_end();
-
-			if (unlikely(!nbytes))
-				break;
-
-			if (unlikely(nbytes > 0 && nbytes < AES_BLOCK_SIZE))
-				memcpy(walk.dst.virt.addr,
-				       buf + sizeof(buf) - nbytes, nbytes);
-
-			err = skcipher_walk_done(&walk, walk.nbytes - nbytes);
-		} while (walk.nbytes);
-	} else {
-		while (walk.nbytes >= AES_BLOCK_SIZE) {
-			int blocks = walk.nbytes / AES_BLOCK_SIZE;
-			const u8 *src = walk.src.virt.addr;
-			u8 *dst = walk.dst.virt.addr;
-			int remaining = blocks;
-
-			do {
-				aes_encrypt(&ctx->aes_key, buf, iv);
-				crypto_xor_cpy(dst, src, buf, AES_BLOCK_SIZE);
-				crypto_inc(iv, AES_BLOCK_SIZE);
-
-				dst += AES_BLOCK_SIZE;
-				src += AES_BLOCK_SIZE;
-			} while (--remaining > 0);
-
-			ghash_do_update(blocks, dg, walk.dst.virt.addr,
-					&ctx->ghash_key, NULL);
-
-			err = skcipher_walk_done(&walk,
-						 walk.nbytes % AES_BLOCK_SIZE);
-		}
-
-		/* handle the tail */
-		if (walk.nbytes) {
-			aes_encrypt(&ctx->aes_key, buf, iv);
+	do {
+		const u8 *src = walk.src.virt.addr;
+		u8 *dst = walk.dst.virt.addr;
+		int nbytes = walk.nbytes;
 
-			crypto_xor_cpy(walk.dst.virt.addr, walk.src.virt.addr,
-				       buf, walk.nbytes);
+		tag = (u8 *)&lengths;
 
-			memcpy(buf, walk.dst.virt.addr, walk.nbytes);
-			memset(buf + walk.nbytes, 0, sizeof(buf) - walk.nbytes);
+		if (unlikely(nbytes > 0 && nbytes < AES_BLOCK_SIZE)) {
+			src = dst = memcpy(buf + sizeof(buf) - nbytes,
+					   src, nbytes);
+		} else if (nbytes < walk.total) {
+			nbytes &= ~(AES_BLOCK_SIZE - 1);
+			tag = NULL;
 		}
 
-		tag = (u8 *)&lengths;
-		ghash_do_update(1, dg, tag, &ctx->ghash_key,
-				walk.nbytes ? buf : NULL);
+		kernel_neon_begin();
+		pmull_gcm_encrypt(nbytes, dst, src, ctx->ghash_key.h,
+				  dg, iv, ctx->aes_key.key_enc, nrounds,
+				  tag);
+		kernel_neon_end();
 
-		if (walk.nbytes)
-			err = skcipher_walk_done(&walk, 0);
+		if (unlikely(!nbytes))
+			break;
 
-		put_unaligned_be64(dg[1], tag);
-		put_unaligned_be64(dg[0], tag + 8);
-		put_unaligned_be32(1, iv + GCM_IV_SIZE);
-		aes_encrypt(&ctx->aes_key, iv, iv);
-		crypto_xor(tag, iv, AES_BLOCK_SIZE);
-	}
+		if (unlikely(nbytes > 0 && nbytes < AES_BLOCK_SIZE))
+			memcpy(walk.dst.virt.addr,
+			       buf + sizeof(buf) - nbytes, nbytes);
+
+		err = skcipher_walk_done(&walk, walk.nbytes - nbytes);
+	} while (walk.nbytes);
 
 	if (err)
 		return err;
@@ -464,6 +416,7 @@ static int gcm_decrypt(struct aead_request *req)
 	u64 dg[2] = {};
 	be128 lengths;
 	u8 *tag;
+	int ret;
 	int err;
 
 	lengths.a = cpu_to_be64(req->assoclen * 8);
@@ -481,101 +434,41 @@ static int gcm_decrypt(struct aead_request *req)
 
 	err = skcipher_walk_aead_decrypt(&walk, req, false);
 
-	if (likely(crypto_simd_usable())) {
-		int ret;
-
-		do {
-			const u8 *src = walk.src.virt.addr;
-			u8 *dst = walk.dst.virt.addr;
-			int nbytes = walk.nbytes;
-
-			tag = (u8 *)&lengths;
-
-			if (unlikely(nbytes > 0 && nbytes < AES_BLOCK_SIZE)) {
-				src = dst = memcpy(buf + sizeof(buf) - nbytes,
-						   src, nbytes);
-			} else if (nbytes < walk.total) {
-				nbytes &= ~(AES_BLOCK_SIZE - 1);
-				tag = NULL;
-			}
-
-			kernel_neon_begin();
-			ret = pmull_gcm_decrypt(nbytes, dst, src,
-						ctx->ghash_key.h,
-						dg, iv, ctx->aes_key.key_enc,
-						nrounds, tag, otag, authsize);
-			kernel_neon_end();
-
-			if (unlikely(!nbytes))
-				break;
-
-			if (unlikely(nbytes > 0 && nbytes < AES_BLOCK_SIZE))
-				memcpy(walk.dst.virt.addr,
-				       buf + sizeof(buf) - nbytes, nbytes);
-
-			err = skcipher_walk_done(&walk, walk.nbytes - nbytes);
-		} while (walk.nbytes);
-
-		if (err)
-			return err;
-		if (ret)
-			return -EBADMSG;
-	} else {
-		while (walk.nbytes >= AES_BLOCK_SIZE) {
-			int blocks = walk.nbytes / AES_BLOCK_SIZE;
-			const u8 *src = walk.src.virt.addr;
-			u8 *dst = walk.dst.virt.addr;
-
-			ghash_do_update(blocks, dg, walk.src.virt.addr,
-					&ctx->ghash_key, NULL);
-
-			do {
-				aes_encrypt(&ctx->aes_key, buf, iv);
-				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);
+	do {
+		const u8 *src = walk.src.virt.addr;
+		u8 *dst = walk.dst.virt.addr;
+		int nbytes = walk.nbytes;
 
-			err = skcipher_walk_done(&walk,
-						 walk.nbytes % AES_BLOCK_SIZE);
-		}
+		tag = (u8 *)&lengths;
 
-		/* handle the tail */
-		if (walk.nbytes) {
-			memcpy(buf, walk.src.virt.addr, walk.nbytes);
-			memset(buf + walk.nbytes, 0, sizeof(buf) - walk.nbytes);
+		if (unlikely(nbytes > 0 && nbytes < AES_BLOCK_SIZE)) {
+			src = dst = memcpy(buf + sizeof(buf) - nbytes,
+					   src, nbytes);
+		} else if (nbytes < walk.total) {
+			nbytes &= ~(AES_BLOCK_SIZE - 1);
+			tag = NULL;
 		}
 
-		tag = (u8 *)&lengths;
-		ghash_do_update(1, dg, tag, &ctx->ghash_key,
-				walk.nbytes ? buf : NULL);
-
-		if (walk.nbytes) {
-			aes_encrypt(&ctx->aes_key, buf, iv);
+		kernel_neon_begin();
+		ret = pmull_gcm_decrypt(nbytes, dst, src, ctx->ghash_key.h,
+					dg, iv, ctx->aes_key.key_enc,
+					nrounds, tag, otag, authsize);
+		kernel_neon_end();
 
-			crypto_xor_cpy(walk.dst.virt.addr, walk.src.virt.addr,
-				       buf, walk.nbytes);
+		if (unlikely(!nbytes))
+			break;
 
-			err = skcipher_walk_done(&walk, 0);
-		}
+		if (unlikely(nbytes > 0 && nbytes < AES_BLOCK_SIZE))
+			memcpy(walk.dst.virt.addr,
+			       buf + sizeof(buf) - nbytes, nbytes);
 
-		if (err)
-			return err;
+		err = skcipher_walk_done(&walk, walk.nbytes - nbytes);
+	} while (walk.nbytes);
 
-		put_unaligned_be64(dg[1], tag);
-		put_unaligned_be64(dg[0], tag + 8);
-		put_unaligned_be32(1, iv + GCM_IV_SIZE);
-		aes_encrypt(&ctx->aes_key, iv, iv);
-		crypto_xor(tag, iv, AES_BLOCK_SIZE);
+	if (err)
+		return err;
 
-		if (crypto_memneq(tag, otag, authsize)) {
-			memzero_explicit(tag, AES_BLOCK_SIZE);
-			return -EBADMSG;
-		}
-	}
-	return 0;
+	return ret ? -EBADMSG : 0;
 }
 
 static struct aead_alg gcm_aes_alg = {
-- 
2.20.1

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