crypto: arm64/aes - add scalar implementation

This adds a scalar implementation of AES, based on the precomputed tables
that are exposed by the generic AES code. Since rotates are cheap on arm64,
this implementation only uses the 4 core tables (of 1 KB each), and avoids
the prerotated ones, reducing the D-cache footprint by 75%.

On Cortex-A57, this code manages 13.0 cycles per byte, which is ~34% faster
than the generic C code. (Note that this is still >13x slower than the code
that uses the optional ARMv8 Crypto Extensions, which manages <1 cycles per
byte.)
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

arch/arm64/crypto/Kconfig

@@ -41,6 +41,10 @@ config CRYPTO_CRC32_ARM64_CE
 	depends on KERNEL_MODE_NEON && CRC32
 	select CRYPTO_HASH
 
+config CRYPTO_AES_ARM64
+	tristate "AES core cipher using scalar instructions"
+	select CRYPTO_AES
+
 config CRYPTO_AES_ARM64_CE
 	tristate "AES core cipher using ARMv8 Crypto Extensions"
 	depends on ARM64 && KERNEL_MODE_NEON

arch/arm64/crypto/Makefile

@@ -44,6 +44,9 @@ sha512-arm64-y := sha512-glue.o sha512-core.o
 obj-$(CONFIG_CRYPTO_CHACHA20_NEON) += chacha20-neon.o
 chacha20-neon-y := chacha20-neon-core.o chacha20-neon-glue.o
 
+obj-$(CONFIG_CRYPTO_AES_ARM64) += aes-arm64.o
+aes-arm64-y := aes-cipher-core.o aes-cipher-glue.o
+
 AFLAGS_aes-ce.o		:= -DINTERLEAVE=4
 AFLAGS_aes-neon.o	:= -DINTERLEAVE=4
 

arch/arm64/crypto/aes-cipher-core.S

+/*
+ * Scalar AES core transform
+ *
+ * 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 <linux/linkage.h>
+#include <asm/assembler.h>
+
+	.text
+
+	rk		.req	x0
+	out		.req	x1
+	in		.req	x2
+	rounds		.req	x3
+	tt		.req	x4
+	lt		.req	x2
+
+	.macro		__hround, out0, out1, in0, in1, in2, in3, t0, t1, enc
+	ldp		\out0, \out1, [rk], #8
+
+	ubfx		w13, \in0, #0, #8
+	ubfx		w14, \in1, #8, #8
+	ldr		w13, [tt, w13, uxtw #2]
+	ldr		w14, [tt, w14, uxtw #2]
+
+	.if		\enc
+	ubfx		w17, \in1, #0, #8
+	ubfx		w18, \in2, #8, #8
+	.else
+	ubfx		w17, \in3, #0, #8
+	ubfx		w18, \in0, #8, #8
+	.endif
+	ldr		w17, [tt, w17, uxtw #2]
+	ldr		w18, [tt, w18, uxtw #2]
+
+	ubfx		w15, \in2, #16, #8
+	ubfx		w16, \in3, #24, #8
+	ldr		w15, [tt, w15, uxtw #2]
+	ldr		w16, [tt, w16, uxtw #2]
+
+	.if		\enc
+	ubfx		\t0, \in3, #16, #8
+	ubfx		\t1, \in0, #24, #8
+	.else
+	ubfx		\t0, \in1, #16, #8
+	ubfx		\t1, \in2, #24, #8
+	.endif
+	ldr		\t0, [tt, \t0, uxtw #2]
+	ldr		\t1, [tt, \t1, uxtw #2]
+
+	eor		\out0, \out0, w13
+	eor		\out1, \out1, w17
+	eor		\out0, \out0, w14, ror #24
+	eor		\out1, \out1, w18, ror #24
+	eor		\out0, \out0, w15, ror #16
+	eor		\out1, \out1, \t0, ror #16
+	eor		\out0, \out0, w16, ror #8
+	eor		\out1, \out1, \t1, ror #8
+	.endm
+
+	.macro		fround, out0, out1, out2, out3, in0, in1, in2, in3
+	__hround	\out0, \out1, \in0, \in1, \in2, \in3, \out2, \out3, 1
+	__hround	\out2, \out3, \in2, \in3, \in0, \in1, \in1, \in2, 1
+	.endm
+
+	.macro		iround, out0, out1, out2, out3, in0, in1, in2, in3
+	__hround	\out0, \out1, \in0, \in3, \in2, \in1, \out2, \out3, 0
+	__hround	\out2, \out3, \in2, \in1, \in0, \in3, \in1, \in0, 0
+	.endm
+
+	.macro		do_crypt, round, ttab, ltab
+	ldp		w5, w6, [in]
+	ldp		w7, w8, [in, #8]
+	ldp		w9, w10, [rk], #16
+	ldp		w11, w12, [rk, #-8]
+
+CPU_BE(	rev		w5, w5		)
+CPU_BE(	rev		w6, w6		)
+CPU_BE(	rev		w7, w7		)
+CPU_BE(	rev		w8, w8		)
+
+	eor		w5, w5, w9
+	eor		w6, w6, w10
+	eor		w7, w7, w11
+	eor		w8, w8, w12
+
+	ldr		tt, =\ttab
+	ldr		lt, =\ltab
+
+	tbnz		rounds, #1, 1f
+
+0:	\round		w9, w10, w11, w12, w5, w6, w7, w8
+	\round		w5, w6, w7, w8, w9, w10, w11, w12
+
+1:	subs		rounds, rounds, #4
+	\round		w9, w10, w11, w12, w5, w6, w7, w8
+	csel		tt, tt, lt, hi
+	\round		w5, w6, w7, w8, w9, w10, w11, w12
+	b.hi		0b
+
+CPU_BE(	rev		w5, w5		)
+CPU_BE(	rev		w6, w6		)
+CPU_BE(	rev		w7, w7		)
+CPU_BE(	rev		w8, w8		)
+
+	stp		w5, w6, [out]
+	stp		w7, w8, [out, #8]
+	ret
+
+	.align		4
+	.ltorg
+	.endm
+
+	.align		5
+ENTRY(__aes_arm64_encrypt)
+	do_crypt	fround, crypto_ft_tab, crypto_fl_tab
+ENDPROC(__aes_arm64_encrypt)
+
+	.align		5
+ENTRY(__aes_arm64_decrypt)
+	do_crypt	iround, crypto_it_tab, crypto_il_tab
+ENDPROC(__aes_arm64_decrypt)

arch/arm64/crypto/aes-cipher-glue.c

+/*
+ * Scalar AES core transform
+ *
+ * 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 <linux/crypto.h>
+#include <linux/module.h>
+
+asmlinkage void __aes_arm64_encrypt(u32 *rk, u8 *out, const u8 *in, int rounds);
+EXPORT_SYMBOL(__aes_arm64_encrypt);
+
+asmlinkage void __aes_arm64_decrypt(u32 *rk, u8 *out, const u8 *in, int rounds);
+EXPORT_SYMBOL(__aes_arm64_decrypt);
+
+static void aes_encrypt(struct crypto_tfm *tfm, u8 *out, const u8 *in)
+{
+	struct crypto_aes_ctx *ctx = crypto_tfm_ctx(tfm);
+	int rounds = 6 + ctx->key_length / 4;
+
+	__aes_arm64_encrypt(ctx->key_enc, out, in, rounds);
+}
+
+static void aes_decrypt(struct crypto_tfm *tfm, u8 *out, const u8 *in)
+{
+	struct crypto_aes_ctx *ctx = crypto_tfm_ctx(tfm);
+	int rounds = 6 + ctx->key_length / 4;
+
+	__aes_arm64_decrypt(ctx->key_dec, out, in, rounds);
+}
+
+static struct crypto_alg aes_alg = {
+	.cra_name			= "aes",
+	.cra_driver_name		= "aes-arm64",
+	.cra_priority			= 200,
+	.cra_flags			= CRYPTO_ALG_TYPE_CIPHER,
+	.cra_blocksize			= AES_BLOCK_SIZE,
+	.cra_ctxsize			= sizeof(struct crypto_aes_ctx),
+	.cra_module			= THIS_MODULE,
+
+	.cra_cipher.cia_min_keysize	= AES_MIN_KEY_SIZE,
+	.cra_cipher.cia_max_keysize	= AES_MAX_KEY_SIZE,
+	.cra_cipher.cia_setkey		= crypto_aes_set_key,
+	.cra_cipher.cia_encrypt		= aes_encrypt,
+	.cra_cipher.cia_decrypt		= aes_decrypt
+};
+
+static int __init aes_init(void)
+{
+	return crypto_register_alg(&aes_alg);
+}
+
+static void __exit aes_fini(void)
+{
+	crypto_unregister_alg(&aes_alg);
+}
+
+module_init(aes_init);
+module_exit(aes_fini);
+
+MODULE_DESCRIPTION("Scalar AES cipher for arm64");
+MODULE_AUTHOR("Ard Biesheuvel <ard.biesheuvel@linaro.org>");
+MODULE_LICENSE("GPL v2");
+MODULE_ALIAS_CRYPTO("aes");