crypto: arm64/aes-blk - add a non-SIMD fallback for synchronous CTR

To accommodate systems that may disallow use of the NEON in kernel mode
in some circumstances, introduce a C fallback for synchronous AES in CTR
mode, and use it if may_use_simd() returns false.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

Author: Ard Biesheuvel

arch/arm64/crypto/Kconfig

@@ -64,15 +64,17 @@ config CRYPTO_AES_ARM64_CE_CCM
 
 config CRYPTO_AES_ARM64_CE_BLK
 	tristate "AES in ECB/CBC/CTR/XTS modes using ARMv8 Crypto Extensions"
-	depends on ARM64 && KERNEL_MODE_NEON
+	depends on KERNEL_MODE_NEON
 	select CRYPTO_BLKCIPHER
 	select CRYPTO_AES_ARM64_CE
+	select CRYPTO_AES_ARM64
 	select CRYPTO_SIMD
 
 config CRYPTO_AES_ARM64_NEON_BLK
 	tristate "AES in ECB/CBC/CTR/XTS modes using NEON instructions"
-	depends on ARM64 && KERNEL_MODE_NEON
+	depends on KERNEL_MODE_NEON
 	select CRYPTO_BLKCIPHER
+	select CRYPTO_AES_ARM64
 	select CRYPTO_AES
 	select CRYPTO_SIMD
 

arch/arm64/crypto/aes-ctr-fallback.h

@@ -0,0 +1,53 @@
+/*
+ * Fallback for sync aes(ctr) in contexts where kernel mode NEON
+ * is not allowed
+ *
+ * Copyright (C) 2017 Linaro Ltd <ard.biesheuvel@linaro.org>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <crypto/aes.h>
+#include <crypto/internal/skcipher.h>
+
+asmlinkage void __aes_arm64_encrypt(u32 *rk, u8 *out, const u8 *in, int rounds);
+
+static inline int aes_ctr_encrypt_fallback(struct crypto_aes_ctx *ctx,
+					   struct skcipher_request *req)
+{
+	struct skcipher_walk walk;
+	u8 buf[AES_BLOCK_SIZE];
+	int err;
+
+	err = skcipher_walk_virt(&walk, req, true);
+
+	while (walk.nbytes > 0) {
+		u8 *dst = walk.dst.virt.addr;
+		u8 *src = walk.src.virt.addr;
+		int nbytes = walk.nbytes;
+		int tail = 0;
+
+		if (nbytes < walk.total) {
+			nbytes = round_down(nbytes, AES_BLOCK_SIZE);
+			tail = walk.nbytes % AES_BLOCK_SIZE;
+		}
+
+		do {
+			int bsize = min(nbytes, AES_BLOCK_SIZE);
+
+			__aes_arm64_encrypt(ctx->key_enc, buf, walk.iv,
+					    6 + ctx->key_length / 4);
+			crypto_xor_cpy(dst, src, buf, bsize);
+			crypto_inc(walk.iv, AES_BLOCK_SIZE);
+
+			dst += AES_BLOCK_SIZE;
+			src += AES_BLOCK_SIZE;
+			nbytes -= AES_BLOCK_SIZE;
+		} while (nbytes > 0);
+
+		err = skcipher_walk_done(&walk, tail);
+	}
+	return err;
+}

arch/arm64/crypto/aes-glue.c

@@ -10,6 +10,7 @@
 
 #include <asm/neon.h>
 #include <asm/hwcap.h>
+#include <asm/simd.h>
 #include <crypto/aes.h>
 #include <crypto/internal/hash.h>
 #include <crypto/internal/simd.h>
@@ -19,6 +20,7 @@
 #include <crypto/xts.h>
 
 #include "aes-ce-setkey.h"
+#include "aes-ctr-fallback.h"
 
 #ifdef USE_V8_CRYPTO_EXTENSIONS
 #define MODE			"ce"
@@ -249,6 +251,17 @@ static int ctr_encrypt(struct skcipher_request *req)
 	return err;
 }
 
+static int ctr_encrypt_sync(struct skcipher_request *req)
+{
+	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
+	struct crypto_aes_ctx *ctx = crypto_skcipher_ctx(tfm);
+
+	if (!may_use_simd())
+		return aes_ctr_encrypt_fallback(ctx, req);
+
+	return ctr_encrypt(req);
+}
+
 static int xts_encrypt(struct skcipher_request *req)
 {
 	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
@@ -355,8 +368,8 @@ static struct skcipher_alg aes_algs[] = { {
 	.ivsize		= AES_BLOCK_SIZE,
 	.chunksize	= AES_BLOCK_SIZE,
 	.setkey		= skcipher_aes_setkey,
-	.encrypt	= ctr_encrypt,
-	.decrypt	= ctr_encrypt,
+	.encrypt	= ctr_encrypt_sync,
+	.decrypt	= ctr_encrypt_sync,
 }, {
 	.base = {
 		.cra_name		= "__xts(aes)",
@@ -458,11 +471,35 @@ static int mac_init(struct shash_desc *desc)
 	return 0;
 }
 
+static void mac_do_update(struct crypto_aes_ctx *ctx, u8 const in[], int blocks,
+			  u8 dg[], int enc_before, int enc_after)
+{
+	int rounds = 6 + ctx->key_length / 4;
+
+	if (may_use_simd()) {
+		kernel_neon_begin();
+		aes_mac_update(in, ctx->key_enc, rounds, blocks, dg, enc_before,
+			       enc_after);
+		kernel_neon_end();
+	} else {
+		if (enc_before)
+			__aes_arm64_encrypt(ctx->key_enc, dg, dg, rounds);
+
+		while (blocks--) {
+			crypto_xor(dg, in, AES_BLOCK_SIZE);
+			in += AES_BLOCK_SIZE;
+
+			if (blocks || enc_after)
+				__aes_arm64_encrypt(ctx->key_enc, dg, dg,
+						    rounds);
+		}
+	}
+}
+
 static int mac_update(struct shash_desc *desc, const u8 *p, unsigned int len)
 {
 	struct mac_tfm_ctx *tctx = crypto_shash_ctx(desc->tfm);
 	struct mac_desc_ctx *ctx = shash_desc_ctx(desc);
-	int rounds = 6 + tctx->key.key_length / 4;
 
 	while (len > 0) {
 		unsigned int l;
@@ -474,10 +511,8 @@ static int mac_update(struct shash_desc *desc, const u8 *p, unsigned int len)
 
 			len %= AES_BLOCK_SIZE;
 
-			kernel_neon_begin();
-			aes_mac_update(p, tctx->key.key_enc, rounds, blocks,
-				       ctx->dg, (ctx->len != 0), (len != 0));
-			kernel_neon_end();
+			mac_do_update(&tctx->key, p, blocks, ctx->dg,
+				      (ctx->len != 0), (len != 0));
 
 			p += blocks * AES_BLOCK_SIZE;
 
@@ -505,11 +540,8 @@ static int cbcmac_final(struct shash_desc *desc, u8 *out)
 {
 	struct mac_tfm_ctx *tctx = crypto_shash_ctx(desc->tfm);
 	struct mac_desc_ctx *ctx = shash_desc_ctx(desc);
-	int rounds = 6 + tctx->key.key_length / 4;
 
-	kernel_neon_begin();
-	aes_mac_update(NULL, tctx->key.key_enc, rounds, 0, ctx->dg, 1, 0);
-	kernel_neon_end();
+	mac_do_update(&tctx->key, NULL, 0, ctx->dg, 1, 0);
 
 	memcpy(out, ctx->dg, AES_BLOCK_SIZE);
 
@@ -520,17 +552,14 @@ static int cmac_final(struct shash_desc *desc, u8 *out)
 {
 	struct mac_tfm_ctx *tctx = crypto_shash_ctx(desc->tfm);
 	struct mac_desc_ctx *ctx = shash_desc_ctx(desc);
-	int rounds = 6 + tctx->key.key_length / 4;
 	u8 *consts = tctx->consts;
 
 	if (ctx->len != AES_BLOCK_SIZE) {
 		ctx->dg[ctx->len] ^= 0x80;
 		consts += AES_BLOCK_SIZE;
 	}
 
-	kernel_neon_begin();
-	aes_mac_update(consts, tctx->key.key_enc, rounds, 1, ctx->dg, 0, 1);
-	kernel_neon_end();
+	mac_do_update(&tctx->key, consts, 1, ctx->dg, 0, 1);
 
 	memcpy(out, ctx->dg, AES_BLOCK_SIZE);