Re: [PATCH 3/4] crypto: arm64/chacha20 - refactor to allow varying number of rounds

From: Ard Biesheuvel
Date: Fri Nov 30 2018 - 08:03:43 EST

On Thu, 29 Nov 2018 at 07:35, Eric Biggers <ebiggers@xxxxxxxxxx> wrote:
>
> From: Eric Biggers <ebiggers@xxxxxxxxxx>
>
> In preparation for adding XChaCha12 support, rename/refactor the ARM64
> NEON implementation of ChaCha20 to support different numbers of rounds.
>
> Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx>

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

> ---
> arch/arm64/crypto/Makefile | 4 +-
> ...hacha20-neon-core.S => chacha-neon-core.S} | 45 ++++++++-------
> ...hacha20-neon-glue.c => chacha-neon-glue.c} | 57 ++++++++++---------
> 3 files changed, 57 insertions(+), 49 deletions(-)
> rename arch/arm64/crypto/{chacha20-neon-core.S => chacha-neon-core.S} (94%)
> rename arch/arm64/crypto/{chacha20-neon-glue.c => chacha-neon-glue.c} (71%)
>
> diff --git a/arch/arm64/crypto/Makefile b/arch/arm64/crypto/Makefile
> index 125dbb10a93ed..a4ffd9fe32650 100644
> --- a/arch/arm64/crypto/Makefile
> +++ b/arch/arm64/crypto/Makefile
> @@ -50,8 +50,8 @@ sha256-arm64-y := sha256-glue.o sha256-core.o
> obj-$(CONFIG_CRYPTO_SHA512_ARM64) += sha512-arm64.o
> sha512-arm64-y := sha512-glue.o sha512-core.o
>
> -obj-$(CONFIG_CRYPTO_CHACHA20_NEON) += chacha20-neon.o
> -chacha20-neon-y := chacha20-neon-core.o chacha20-neon-glue.o
> +obj-$(CONFIG_CRYPTO_CHACHA20_NEON) += chacha-neon.o
> +chacha-neon-y := chacha-neon-core.o chacha-neon-glue.o
>
> obj-$(CONFIG_CRYPTO_NHPOLY1305_NEON) += nhpoly1305-neon.o
> nhpoly1305-neon-y := nh-neon-core.o nhpoly1305-neon-glue.o
> diff --git a/arch/arm64/crypto/chacha20-neon-core.S b/arch/arm64/crypto/chacha-neon-core.S
> similarity index 94%
> rename from arch/arm64/crypto/chacha20-neon-core.S
> rename to arch/arm64/crypto/chacha-neon-core.S
> index 378850505c0ae..75b4e06cee79f 100644
> --- a/arch/arm64/crypto/chacha20-neon-core.S
> +++ b/arch/arm64/crypto/chacha-neon-core.S
> @@ -1,5 +1,5 @@
> /*
> - * ChaCha20 256-bit cipher algorithm, RFC7539, arm64 NEON functions
> + * ChaCha/XChaCha NEON helper functions
> *
> * Copyright (C) 2016 Linaro, Ltd. <ard.biesheuvel@xxxxxxxxxx>
> *
> @@ -24,17 +24,18 @@
> .align 6
>
> /*
> - * 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 v0-v3. It performs matrix operations on four words in parallel,
> * but requires shuffling to rearrange the words after each round.
> *
> - * Clobbers: x3, x10, v4, v12
> + * The round count is given in w3.
> + *
> + * Clobbers: w3, x10, v4, v12
> */
> -chacha20_permute:
> +chacha_permute:
>
> - mov x3, #10
> adr x10, ROT8
> ld1 {v12.4s}, [x10]
>
> @@ -97,16 +98,17 @@ chacha20_permute:
> // x3 = shuffle32(x3, MASK(0, 3, 2, 1))
> ext v3.16b, v3.16b, v3.16b, #4
>
> - subs x3, x3, #1
> + subs w3, w3, #2
> b.ne .Ldoubleround
>
> ret
> -ENDPROC(chacha20_permute)
> +ENDPROC(chacha_permute)
>
> -ENTRY(chacha20_block_xor_neon)
> +ENTRY(chacha_block_xor_neon)
> // x0: Input state matrix, s
> // x1: 1 data block output, o
> // x2: 1 data block input, i
> + // w3: nrounds
>
> mov x9, lr
>
> @@ -114,7 +116,7 @@ ENTRY(chacha20_block_xor_neon)
> ld1 {v0.4s-v3.4s}, [x0]
> ld1 {v8.4s-v11.4s}, [x0]
>
> - bl chacha20_permute
> + bl chacha_permute
>
> ld1 {v4.16b-v7.16b}, [x2]
>
> @@ -137,39 +139,42 @@ ENTRY(chacha20_block_xor_neon)
> st1 {v0.16b-v3.16b}, [x1]
>
> ret x9
> -ENDPROC(chacha20_block_xor_neon)
> +ENDPROC(chacha_block_xor_neon)
>
> -ENTRY(hchacha20_block_neon)
> +ENTRY(hchacha_block_neon)
> // x0: Input state matrix, s
> // x1: output (8 32-bit words)
> + // w2: nrounds
> mov x9, lr
>
> ld1 {v0.4s-v3.4s}, [x0]
>
> - bl chacha20_permute
> + mov w3, w2
> + bl chacha_permute
>
> st1 {v0.16b}, [x1], #16
> st1 {v3.16b}, [x1]
>
> ret x9
> -ENDPROC(hchacha20_block_neon)
> +ENDPROC(hchacha_block_neon)
>
> .align 6
> -ENTRY(chacha20_4block_xor_neon)
> +ENTRY(chacha_4block_xor_neon)
> // x0: Input state matrix, s
> // x1: 4 data blocks output, o
> // x2: 4 data blocks input, i
> + // w3: 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. For final XORing step we transpose the
> // matrix by interleaving 32- and then 64-bit words, which allows us to
> // do XOR in NEON registers.
> //
> - adr x3, CTRINC // ... and ROT8
> - ld1 {v30.4s-v31.4s}, [x3]
> + adr x9, CTRINC // ... and ROT8
> + ld1 {v30.4s-v31.4s}, [x9]
>
> // x0..15[0-3] = s0..3[0..3]
> mov x4, x0
> @@ -181,8 +186,6 @@ ENTRY(chacha20_4block_xor_neon)
> // x12 += counter values 0-3
> add v12.4s, v12.4s, v30.4s
>
> - mov x3, #10
> -
> .Ldoubleround4:
> // x0 += x4, x12 = rotl32(x12 ^ x0, 16)
> // x1 += x5, x13 = rotl32(x13 ^ x1, 16)
> @@ -356,7 +359,7 @@ ENTRY(chacha20_4block_xor_neon)
> sri v7.4s, v18.4s, #25
> sri v4.4s, v19.4s, #25
>
> - subs x3, x3, #1
> + subs w3, w3, #2
> b.ne .Ldoubleround4
>
> ld4r {v16.4s-v19.4s}, [x0], #16
> @@ -470,7 +473,7 @@ ENTRY(chacha20_4block_xor_neon)
> st1 {v28.16b-v31.16b}, [x1]
>
> ret
> -ENDPROC(chacha20_4block_xor_neon)
> +ENDPROC(chacha_4block_xor_neon)
>
> CTRINC: .word 0, 1, 2, 3
> ROT8: .word 0x02010003, 0x06050407, 0x0a09080b, 0x0e0d0c0f
> diff --git a/arch/arm64/crypto/chacha20-neon-glue.c b/arch/arm64/crypto/chacha-neon-glue.c
> similarity index 71%
> rename from arch/arm64/crypto/chacha20-neon-glue.c
> rename to arch/arm64/crypto/chacha-neon-glue.c
> index a5b9cbc0c4de4..4d992029b9121 100644
> --- a/arch/arm64/crypto/chacha20-neon-glue.c
> +++ b/arch/arm64/crypto/chacha-neon-glue.c
> @@ -1,5 +1,6 @@
> /*
> - * ChaCha20 256-bit cipher algorithm, RFC7539, arm64 NEON functions
> + * ARM NEON accelerated ChaCha and XChaCha stream ciphers,
> + * including ChaCha20 (RFC7539)
> *
> * Copyright (C) 2016 - 2017 Linaro, Ltd. <ard.biesheuvel@xxxxxxxxxx>
> *
> @@ -28,18 +29,20 @@
> #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);
> +asmlinkage void chacha_block_xor_neon(u32 *state, u8 *dst, const u8 *src,
> + int nrounds);
> +asmlinkage void chacha_4block_xor_neon(u32 *state, u8 *dst, const u8 *src,
> + int nrounds);
> +asmlinkage void hchacha_block_neon(const u32 *state, u32 *out, int nrounds);
>
> -static void chacha20_doneon(u32 *state, u8 *dst, const u8 *src,
> - unsigned int bytes)
> +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) {
> kernel_neon_begin();
> - chacha20_4block_xor_neon(state, dst, src);
> + chacha_4block_xor_neon(state, dst, src, nrounds);
> kernel_neon_end();
> bytes -= CHACHA_BLOCK_SIZE * 4;
> src += CHACHA_BLOCK_SIZE * 4;
> @@ -52,7 +55,7 @@ static void chacha20_doneon(u32 *state, u8 *dst, const u8 *src,
>
> kernel_neon_begin();
> 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;
> @@ -60,14 +63,14 @@ 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);
> }
> kernel_neon_end();
> }
>
> -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];
> @@ -83,15 +86,15 @@ 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);
> @@ -99,10 +102,10 @@ static int chacha20_neon(struct skcipher_request *req)
> if (req->cryptlen <= CHACHA_BLOCK_SIZE || !may_use_simd())
> return crypto_chacha_crypt(req);
>
> - return chacha20_neon_stream_xor(req, ctx, req->iv);
> + return chacha_neon_stream_xor(req, ctx, req->iv);
> }
>
> -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);
> @@ -116,12 +119,13 @@ static int xchacha20_neon(struct skcipher_request *req)
> crypto_chacha_init(state, ctx, req->iv);
>
> kernel_neon_begin();
> - hchacha20_block_neon(state, subctx.key);
> + hchacha_block_neon(state, subctx.key, ctx->nrounds);
> kernel_neon_end();
> + subctx.nrounds = ctx->nrounds;
>
> memcpy(&real_iv[0], req->iv + 24, 8);
> memcpy(&real_iv[8], req->iv + 16, 8);
> - return chacha20_neon_stream_xor(req, &subctx, real_iv);
> + return chacha_neon_stream_xor(req, &subctx, real_iv);
> }
>
> static struct skcipher_alg algs[] = {
> @@ -139,8 +143,8 @@ 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 +159,12 @@ 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_ASIMD))
> return -ENODEV;
> @@ -168,14 +172,15 @@ 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@xxxxxxxxxx>");
> MODULE_LICENSE("GPL v2");
> MODULE_ALIAS_CRYPTO("chacha20");
> --
> 2.19.2
>