Re: [PATCH v4 08/35] crypto: arm/chacha - remove dependency on generic ChaCha driver

From: Eric Biggers <ebiggers@kernel.org>
To: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: linux-crypto@vger.kernel.org,
	Herbert Xu <herbert@gondor.apana.org.au>,
	David Miller <davem@davemloft.net>,
	"Jason A . Donenfeld" <Jason@zx2c4.com>,
	Samuel Neves <sneves@dei.uc.pt>, Arnd Bergmann <arnd@arndb.de>,
	Andy Lutomirski <luto@kernel.org>,
	Martin Willi <martin@strongswan.org>,
	Rene van Dorst <opensource@vdorst.com>,
	David Sterba <dsterba@suse.com>
Subject: Re: [PATCH v4 08/35] crypto: arm/chacha - remove dependency on generic ChaCha driver
Date: Tue, 22 Oct 2019 20:21:30 -0700	[thread overview]
Message-ID: <20191023032130.GF4278@sol.localdomain> (raw)
In-Reply-To: <20191017190932.1947-9-ard.biesheuvel@linaro.org>

On Thu, Oct 17, 2019 at 09:09:05PM +0200, Ard Biesheuvel wrote:
> Instead of falling back to the generic ChaCha skcipher driver for
> non-SIMD cases, use a fast scalar implementation for ARM authored
> by Eric Biggers. This removes the module dependency on chacha-generic
> altogether, which also simplifies things when we expose the ChaCha
> library interface from this module.
> 
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> ---
>  arch/arm/crypto/Kconfig              |   4 +-
>  arch/arm/crypto/Makefile             |   3 +-
>  arch/arm/crypto/chacha-glue.c        | 316 ++++++++++++++++++++
>  arch/arm/crypto/chacha-neon-glue.c   | 202 -------------
>  arch/arm/crypto/chacha-scalar-core.S |  65 ++--
>  5 files changed, 351 insertions(+), 239 deletions(-)
> 
> diff --git a/arch/arm/crypto/Kconfig b/arch/arm/crypto/Kconfig
> index b24df84a1d7a..a31b0b95548d 100644
> --- a/arch/arm/crypto/Kconfig
> +++ b/arch/arm/crypto/Kconfig
> @@ -126,10 +126,8 @@ config CRYPTO_CRC32_ARM_CE
>  	select CRYPTO_HASH
>  
>  config CRYPTO_CHACHA20_NEON
> -	tristate "NEON accelerated ChaCha stream cipher algorithms"
> -	depends on KERNEL_MODE_NEON
> +	tristate "NEON and scalar accelerated ChaCha stream cipher algorithms"
>  	select CRYPTO_BLKCIPHER
> -	select CRYPTO_CHACHA20
>  
>  config CRYPTO_NHPOLY1305_NEON
>  	tristate "NEON accelerated NHPoly1305 hash function (for Adiantum)"
> diff --git a/arch/arm/crypto/Makefile b/arch/arm/crypto/Makefile
> index 4180f3a13512..6b97dffcf90f 100644
> --- a/arch/arm/crypto/Makefile
> +++ b/arch/arm/crypto/Makefile
> @@ -53,7 +53,8 @@ aes-arm-ce-y	:= aes-ce-core.o aes-ce-glue.o
>  ghash-arm-ce-y	:= ghash-ce-core.o ghash-ce-glue.o
>  crct10dif-arm-ce-y	:= crct10dif-ce-core.o crct10dif-ce-glue.o
>  crc32-arm-ce-y:= crc32-ce-core.o crc32-ce-glue.o
> -chacha-neon-y := chacha-neon-core.o chacha-neon-glue.o
> +chacha-neon-y := chacha-scalar-core.o chacha-glue.o
> +chacha-neon-$(CONFIG_KERNEL_MODE_NEON) += chacha-neon-core.o
>  nhpoly1305-neon-y := nh-neon-core.o nhpoly1305-neon-glue.o
>  
>  ifdef REGENERATE_ARM_CRYPTO
> diff --git a/arch/arm/crypto/chacha-glue.c b/arch/arm/crypto/chacha-glue.c
> new file mode 100644
> index 000000000000..2c0f76bc08b2
> --- /dev/null
> +++ b/arch/arm/crypto/chacha-glue.c
> @@ -0,0 +1,316 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * ARM NEON accelerated ChaCha and XChaCha stream ciphers,
> + * including ChaCha20 (RFC7539)
> + *
> + * Copyright (C) 2016-2019 Linaro, Ltd. <ard.biesheuvel@linaro.org>
> + * Copyright (C) 2015 Martin Willi
> + */

Technically this file comment should be updated too:
"NEON" => "NEON and scalar"

> diff --git a/arch/arm/crypto/chacha-scalar-core.S b/arch/arm/crypto/chacha-scalar-core.S
> index 2140319b64a0..0970ae107590 100644
> --- a/arch/arm/crypto/chacha-scalar-core.S
> +++ b/arch/arm/crypto/chacha-scalar-core.S
> @@ -41,14 +41,6 @@
>  	X14	.req	r12
>  	X15	.req	r14
>  
> -.Lexpand_32byte_k:
> -	// "expand 32-byte k"
> -	.word	0x61707865, 0x3320646e, 0x79622d32, 0x6b206574
> -
> -#ifdef __thumb2__
> -#  define adrl adr
> -#endif
> -
>  .macro __rev		out, in,  t0, t1, t2
>  .if __LINUX_ARM_ARCH__ >= 6
>  	rev		\out, \in
> @@ -391,61 +383,65 @@
>  .endm	// _chacha
>  
>  /*
> - * void chacha20_arm(u8 *out, const u8 *in, size_t len, const u32 key[8],
> - *		     const u32 iv[4]);
> + * void chacha_doarm(u8 *dst, const u8 *src, unsigned int bytes,
> + *		     u32 *state, int nrounds);
>   */

The comment should say 'const u32 *state' instead of 'u32 *state', to match the
C prototype and to avoid confusion about whether the block counter is
incremented or not.

- Eric