Re: [RFC PATCH v2 06/12] crypto: arm/chacha20 - refactor to allow varying number of rounds

[Ard Biesheuvel <ard.biesheuvel@linaro.org>]

On 16 October 2018 at 01:54, Eric Biggers <ebiggers@kernel.org> wrote:
> From: Eric Biggers <ebiggers@google.com>
>
> In preparation for adding XChaCha12 support, rename/refactor the NEON
> implementation of ChaCha20 to support different numbers of rounds.
>
> Signed-off-by: Eric Biggers <ebiggers@google.com>

Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>

> ---
>  arch/arm/crypto/Makefile                      |  4 +-
>  ...hacha20-neon-core.S => chacha-neon-core.S} | 36 ++++++------
>  ...hacha20-neon-glue.c => chacha-neon-glue.c} | 56 ++++++++++---------
>  3 files changed, 52 insertions(+), 44 deletions(-)
>  rename arch/arm/crypto/{chacha20-neon-core.S => chacha-neon-core.S} (96%)
>  rename arch/arm/crypto/{chacha20-neon-glue.c => chacha-neon-glue.c} (73%)
>
> diff --git a/arch/arm/crypto/Makefile b/arch/arm/crypto/Makefile
> index bd5bceef0605f..005482ff95047 100644
> --- a/arch/arm/crypto/Makefile
> +++ b/arch/arm/crypto/Makefile
> @@ -9,7 +9,7 @@ obj-$(CONFIG_CRYPTO_SHA1_ARM) += sha1-arm.o
>  obj-$(CONFIG_CRYPTO_SHA1_ARM_NEON) += sha1-arm-neon.o
>  obj-$(CONFIG_CRYPTO_SHA256_ARM) += sha256-arm.o
>  obj-$(CONFIG_CRYPTO_SHA512_ARM) += sha512-arm.o
> -obj-$(CONFIG_CRYPTO_CHACHA20_NEON) += chacha20-neon.o
> +obj-$(CONFIG_CRYPTO_CHACHA20_NEON) += chacha-neon.o
>

I take it you are preserving the Kconfig symbol name to prevent
breaking existing configs?

If so, we might consider doing something like

config CRYPTO_CHACHA20_NEON
    tristate

config CRYPTO_CHACHA_NEON
    default CRYPTO_CHACHA20_NEON
    ... the existing kconfig symbol description ...

and drop the former at some point in the future?

>  ce-obj-$(CONFIG_CRYPTO_AES_ARM_CE) += aes-arm-ce.o
>  ce-obj-$(CONFIG_CRYPTO_SHA1_ARM_CE) += sha1-arm-ce.o
> @@ -52,7 +52,7 @@ 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
> -chacha20-neon-y := chacha20-neon-core.o chacha20-neon-glue.o
> +chacha-neon-y := chacha-neon-core.o chacha-neon-glue.o
>
>  ifdef REGENERATE_ARM_CRYPTO
>  quiet_cmd_perl = PERL    $@
> diff --git a/arch/arm/crypto/chacha20-neon-core.S b/arch/arm/crypto/chacha-neon-core.S
> similarity index 96%
> rename from arch/arm/crypto/chacha20-neon-core.S
> rename to arch/arm/crypto/chacha-neon-core.S
> index db59f1fbc728b..4b12064449f78 100644
> --- a/arch/arm/crypto/chacha20-neon-core.S
> +++ b/arch/arm/crypto/chacha-neon-core.S
> @@ -1,5 +1,5 @@
>  /*
> - * ChaCha20 256-bit cipher algorithm, RFC7539, ARM NEON functions
> + * ChaCha/XChaCha NEON helper functions
>   *
>   * Copyright (C) 2016 Linaro, Ltd. <ard.biesheuvel@linaro.org>
>   *
> @@ -53,18 +53,19 @@
>         .align          5
>
>  /*
> - * _chacha20_permute - permute one block
> + * _chacha_permute - permute one block
>   *
>   * Permute one 64-byte block where the state matrix is stored in the four NEON
>   * registers q0-q3.  It performs matrix operation on four words in parallel, but
>   * requires shuffling to rearrange the words after each round.
>   *
> + * The round count is given in r3.
> + *
>   * Clobbers: r3, q4-q5
>   */
> -.macro _chacha20_permute
> +.macro _chacha_permute
>
>         adr             ip, .Lrol8_table
> -       mov             r3, #10
>         vld1.8          {d10}, [ip, :64]
>
>  .Ldoubleround_\@:
> @@ -128,14 +129,15 @@
>         // x3 = shuffle32(x3, MASK(0, 3, 2, 1))
>         vext.8          q3, q3, q3, #4
>
> -       subs            r3, r3, #1
> +       subs            r3, r3, #2
>         bne             .Ldoubleround_\@
>  .endm
>
> -ENTRY(chacha20_block_xor_neon)
> +ENTRY(chacha_block_xor_neon)
>         // r0: Input state matrix, s
>         // r1: 1 data block output, o
>         // r2: 1 data block input, i
> +       // r3: nrounds
>
>         // x0..3 = s0..3
>         add             ip, r0, #0x20
> @@ -147,7 +149,7 @@ ENTRY(chacha20_block_xor_neon)
>         vmov            q10, q2
>         vmov            q11, q3
>
> -       _chacha20_permute
> +       _chacha_permute
>
>         add             ip, r2, #0x20
>         vld1.8          {q4-q5}, [r2]
> @@ -174,29 +176,31 @@ ENTRY(chacha20_block_xor_neon)
>         vst1.8          {q2-q3}, [ip]
>
>         bx              lr
> -ENDPROC(chacha20_block_xor_neon)
> +ENDPROC(chacha_block_xor_neon)
>
> -ENTRY(hchacha20_block_neon)
> +ENTRY(hchacha_block_neon)
>         // r0: Input state matrix, s
>         // r1: output (8 32-bit words)
> +       // r2: nrounds
>
>         vld1.32         {q0-q1}, [r0]!
>         vld1.32         {q2-q3}, [r0]
>
> -       _chacha20_permute
> +       mov             r3, r2
> +       _chacha_permute
>
>         vst1.32         {q0}, [r1]!
>         vst1.32         {q3}, [r1]
>
>         bx              lr
> -ENDPROC(hchacha20_block_neon)
> +ENDPROC(hchacha_block_neon)
>
>         .align          4
>  .Lctrinc:      .word   0, 1, 2, 3
>  .Lrol8_table:  .byte   3, 0, 1, 2, 7, 4, 5, 6
>
>         .align          5
> -ENTRY(chacha20_4block_xor_neon)
> +ENTRY(chacha_4block_xor_neon)
>         push            {r4-r5}
>         mov             r4, sp                  // preserve the stack pointer
>         sub             ip, sp, #0x20           // allocate a 32 byte buffer
> @@ -206,9 +210,10 @@ ENTRY(chacha20_4block_xor_neon)
>         // r0: Input state matrix, s
>         // r1: 4 data blocks output, o
>         // r2: 4 data blocks input, i
> +       // r3: nrounds
>
>         //
> -       // This function encrypts four consecutive ChaCha20 blocks by loading
> +       // This function encrypts four consecutive ChaCha blocks by loading
>         // the state matrix in NEON registers four times. The algorithm performs
>         // each operation on the corresponding word of each state matrix, hence
>         // requires no word shuffling. The words are re-interleaved before the
> @@ -241,7 +246,6 @@ ENTRY(chacha20_4block_xor_neon)
>         vdup.32         q0, d0[0]
>
>         adr             ip, .Lrol8_table
> -       mov             r3, #10
>         b               1f
>
>  .Ldoubleround4:
> @@ -439,7 +443,7 @@ ENTRY(chacha20_4block_xor_neon)
>         vsri.u32        q5, q8, #25
>         vsri.u32        q6, q9, #25
>
> -       subs            r3, r3, #1
> +       subs            r3, r3, #2
>         bne             .Ldoubleround4
>
>         // x0..7[0-3] are in q0-q7, x10..15[0-3] are in q10-q15.
> @@ -549,4 +553,4 @@ ENTRY(chacha20_4block_xor_neon)
>
>         pop             {r4-r5}
>         bx              lr
> -ENDPROC(chacha20_4block_xor_neon)
> +ENDPROC(chacha_4block_xor_neon)
> diff --git a/arch/arm/crypto/chacha20-neon-glue.c b/arch/arm/crypto/chacha-neon-glue.c
> similarity index 73%
> rename from arch/arm/crypto/chacha20-neon-glue.c
> rename to arch/arm/crypto/chacha-neon-glue.c
> index becc7990b1d39..b236af4889c61 100644
> --- a/arch/arm/crypto/chacha20-neon-glue.c
> +++ b/arch/arm/crypto/chacha-neon-glue.c
> @@ -28,24 +28,26 @@
>  #include <asm/neon.h>
>  #include <asm/simd.h>
>
> -asmlinkage void chacha20_block_xor_neon(u32 *state, u8 *dst, const u8 *src);
> -asmlinkage void chacha20_4block_xor_neon(u32 *state, u8 *dst, const u8 *src);
> -asmlinkage void hchacha20_block_neon(const u32 *state, u32 *out);
> -
> -static void chacha20_doneon(u32 *state, u8 *dst, const u8 *src,
> -                           unsigned int bytes)
> +asmlinkage void chacha_block_xor_neon(const u32 *state, u8 *dst, const u8 *src,
> +                                     int nrounds);
> +asmlinkage void chacha_4block_xor_neon(const u32 *state, u8 *dst, const u8 *src,
> +                                      int nrounds);
> +asmlinkage void hchacha_block_neon(const u32 *state, u32 *out, int nrounds);
> +
> +static void chacha_doneon(u32 *state, u8 *dst, const u8 *src,
> +                         unsigned int bytes, int nrounds)
>  {
>         u8 buf[CHACHA_BLOCK_SIZE];
>
>         while (bytes >= CHACHA_BLOCK_SIZE * 4) {
> -               chacha20_4block_xor_neon(state, dst, src);
> +               chacha_4block_xor_neon(state, dst, src, nrounds);
>                 bytes -= CHACHA_BLOCK_SIZE * 4;
>                 src += CHACHA_BLOCK_SIZE * 4;
>                 dst += CHACHA_BLOCK_SIZE * 4;
>                 state[12] += 4;
>         }
>         while (bytes >= CHACHA_BLOCK_SIZE) {
> -               chacha20_block_xor_neon(state, dst, src);
> +               chacha_block_xor_neon(state, dst, src, nrounds);
>                 bytes -= CHACHA_BLOCK_SIZE;
>                 src += CHACHA_BLOCK_SIZE;
>                 dst += CHACHA_BLOCK_SIZE;
> @@ -53,13 +55,13 @@ static void chacha20_doneon(u32 *state, u8 *dst, const u8 *src,
>         }
>         if (bytes) {
>                 memcpy(buf, src, bytes);
> -               chacha20_block_xor_neon(state, buf, buf);
> +               chacha_block_xor_neon(state, buf, buf, nrounds);
>                 memcpy(dst, buf, bytes);
>         }
>  }
>
> -static int chacha20_neon_stream_xor(struct skcipher_request *req,
> -                                   struct chacha_ctx *ctx, u8 *iv)
> +static int chacha_neon_stream_xor(struct skcipher_request *req,
> +                                 struct chacha_ctx *ctx, u8 *iv)
>  {
>         struct skcipher_walk walk;
>         u32 state[16];
> @@ -75,15 +77,15 @@ static int chacha20_neon_stream_xor(struct skcipher_request *req,
>                 if (nbytes < walk.total)
>                         nbytes = round_down(nbytes, walk.stride);
>
> -               chacha20_doneon(state, walk.dst.virt.addr, walk.src.virt.addr,
> -                               nbytes);
> +               chacha_doneon(state, walk.dst.virt.addr, walk.src.virt.addr,
> +                             nbytes, ctx->nrounds);
>                 err = skcipher_walk_done(&walk, walk.nbytes - nbytes);
>         }
>
>         return err;
>  }
>
> -static int chacha20_neon(struct skcipher_request *req)
> +static int chacha_neon(struct skcipher_request *req)
>  {
>         struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
>         struct chacha_ctx *ctx = crypto_skcipher_ctx(tfm);
> @@ -93,12 +95,12 @@ static int chacha20_neon(struct skcipher_request *req)
>                 return crypto_chacha_crypt(req);
>
>         kernel_neon_begin();
> -       err = chacha20_neon_stream_xor(req, ctx, req->iv);
> +       err = chacha_neon_stream_xor(req, ctx, req->iv);
>         kernel_neon_end();
>         return err;
>  }
>
> -static int xchacha20_neon(struct skcipher_request *req)
> +static int xchacha_neon(struct skcipher_request *req)
>  {
>         struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
>         struct chacha_ctx *ctx = crypto_skcipher_ctx(tfm);
> @@ -114,10 +116,11 @@ static int xchacha20_neon(struct skcipher_request *req)
>
>         kernel_neon_begin();
>
> -       hchacha20_block_neon(state, subctx.key);
> +       hchacha_block_neon(state, subctx.key, ctx->nrounds);
> +       subctx.nrounds = ctx->nrounds;
>         memcpy(&real_iv[0], req->iv + 24, 8);
>         memcpy(&real_iv[8], req->iv + 16, 8);
> -       err = chacha20_neon_stream_xor(req, &subctx, real_iv);
> +       err = chacha_neon_stream_xor(req, &subctx, real_iv);
>
>         kernel_neon_end();
>
> @@ -139,8 +142,8 @@ static struct skcipher_alg algs[] = {
>                 .chunksize              = CHACHA_BLOCK_SIZE,
>                 .walksize               = 4 * CHACHA_BLOCK_SIZE,
>                 .setkey                 = crypto_chacha20_setkey,
> -               .encrypt                = chacha20_neon,
> -               .decrypt                = chacha20_neon,
> +               .encrypt                = chacha_neon,
> +               .decrypt                = chacha_neon,
>         }, {
>                 .base.cra_name          = "xchacha20",
>                 .base.cra_driver_name   = "xchacha20-neon",
> @@ -155,12 +158,12 @@ static struct skcipher_alg algs[] = {
>                 .chunksize              = CHACHA_BLOCK_SIZE,
>                 .walksize               = 4 * CHACHA_BLOCK_SIZE,
>                 .setkey                 = crypto_chacha20_setkey,
> -               .encrypt                = xchacha20_neon,
> -               .decrypt                = xchacha20_neon,
> +               .encrypt                = xchacha_neon,
> +               .decrypt                = xchacha_neon,
>         }
>  };
>
> -static int __init chacha20_simd_mod_init(void)
> +static int __init chacha_simd_mod_init(void)
>  {
>         if (!(elf_hwcap & HWCAP_NEON))
>                 return -ENODEV;
> @@ -168,14 +171,15 @@ static int __init chacha20_simd_mod_init(void)
>         return crypto_register_skciphers(algs, ARRAY_SIZE(algs));
>  }
>
> -static void __exit chacha20_simd_mod_fini(void)
> +static void __exit chacha_simd_mod_fini(void)
>  {
>         crypto_unregister_skciphers(algs, ARRAY_SIZE(algs));
>  }
>
> -module_init(chacha20_simd_mod_init);
> -module_exit(chacha20_simd_mod_fini);
> +module_init(chacha_simd_mod_init);
> +module_exit(chacha_simd_mod_fini);
>
> +MODULE_DESCRIPTION("ChaCha and XChaCha stream ciphers (NEON accelerated)");
>  MODULE_AUTHOR("Ard Biesheuvel <ard.biesheuvel@linaro.org>");
>  MODULE_LICENSE("GPL v2");
>  MODULE_ALIAS_CRYPTO("chacha20");
> --
> 2.19.1.331.ge82ca0e54c-goog
>