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>

1 files changed, 53 insertions, 0 deletions

diff --git a/arch/arm64/crypto/aes-ctr-fallback.h b/arch/arm64/crypto/aes-ctr-fallback.h
new file mode 100644
index 000000000000..c9285717b6b5
--- /dev/null
+++ b/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;
+}