Re: [RFC PATCH v3 08/15] crypto: arm/chacha20 - refactor to allow varying number of rounds

From: Ard Biesheuvel
Date: Tue Nov 06 2018 - 07:46:29 EST

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On 6 November 2018 at 00:25, Eric Biggers <ebiggers@xxxxxxxxxx> wrote:
> From: Eric Biggers <ebiggers@xxxxxxxxxx>
>
> 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@xxxxxxxxxx>

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

> ---
> arch/arm/crypto/Makefile | 4 +-
> ...hacha20-neon-core.S => chacha-neon-core.S} | 44 ++++++++-------
> ...hacha20-neon-glue.c => chacha-neon-glue.c} | 56 ++++++++++---------
> 3 files changed, 56 insertions(+), 48 deletions(-)
> rename arch/arm/crypto/{chacha20-neon-core.S => chacha-neon-core.S} (94%)
> rename arch/arm/crypto/{chacha20-neon-glue.c => chacha-neon-glue.c} (72%)
>
> diff --git a/arch/arm/crypto/Makefile b/arch/arm/crypto/Makefile
> index bd5bceef0605..005482ff9504 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
>
> 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 94%
> rename from arch/arm/crypto/chacha20-neon-core.S
> rename to arch/arm/crypto/chacha-neon-core.S
> index 2335e5055d2b..eb22926d4912 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@xxxxxxxxxx>
> *
> @@ -27,9 +27,9 @@
> * (d) vtbl.8 + vtbl.8 (multiple of 8 bits rotations only,
> * needs index vector)
> *
> - * ChaCha20 has 16, 12, 8, and 7-bit rotations. For the 12 and 7-bit
> - * rotations, the only choices are (a) and (b). We use (a) since it takes
> - * two-thirds the cycles of (b) on both Cortex-A7 and Cortex-A53.
> + * ChaCha has 16, 12, 8, and 7-bit rotations. For the 12 and 7-bit rotations,
> + * the only choices are (a) and (b). We use (a) since it takes two-thirds the
> + * cycles of (b) on both Cortex-A7 and Cortex-A53.
> *
> * For the 16-bit rotation, we use vrev32.16 since it's consistently fastest
> * and doesn't need a temporary register.
> @@ -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 operations on four words in parallel,
> * but requires shuffling to rearrange the words after each round.
> *
> + * The round count is given in r3.
> + *
> * Clobbers: r3, ip, q4-q5
> */
> -chacha20_permute:
> +chacha_permute:
>
> adr ip, .Lrol8_table
> - mov r3, #10
> vld1.8 {d10}, [ip, :64]
>
> .Ldoubleround:
> @@ -128,16 +129,17 @@ chacha20_permute:
> // x3 = shuffle32(x3, MASK(0, 3, 2, 1))
> vext.8 q3, q3, q3, #4
>
> - subs r3, r3, #1
> + subs r3, r3, #2
> bne .Ldoubleround
>
> bx lr
> -ENDPROC(chacha20_permute)
> +ENDPROC(chacha_permute)
>
> -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
> push {lr}
>
> // x0..3 = s0..3
> @@ -150,7 +152,7 @@ ENTRY(chacha20_block_xor_neon)
> vmov q10, q2
> vmov q11, q3
>
> - bl chacha20_permute
> + bl chacha_permute
>
> add ip, r2, #0x20
> vld1.8 {q4-q5}, [r2]
> @@ -177,30 +179,32 @@ ENTRY(chacha20_block_xor_neon)
> vst1.8 {q2-q3}, [ip]
>
> pop {pc}
> -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
> push {lr}
>
> vld1.32 {q0-q1}, [r0]!
> vld1.32 {q2-q3}, [r0]
>
> - bl chacha20_permute
> + mov r3, r2
> + bl chacha_permute
>
> vst1.32 {q0}, [r1]!
> vst1.32 {q3}, [r1]
>
> pop {pc}
> -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
> @@ -210,9 +214,10 @@ 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
> @@ -245,7 +250,6 @@ ENTRY(chacha20_4block_xor_neon)
> vdup.32 q0, d0[0]
>
> adr ip, .Lrol8_table
> - mov r3, #10
> b 1f
>
> .Ldoubleround4:
> @@ -443,7 +447,7 @@ 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.
> @@ -553,4 +557,4 @@ 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 72%
> rename from arch/arm/crypto/chacha20-neon-glue.c
> rename to arch/arm/crypto/chacha-neon-glue.c
> index f2d3b0f70a8d..385557d38634 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];
> @@ -76,8 +78,8 @@ static int chacha20_neon_stream_xor(struct skcipher_request *req,
> nbytes = round_down(nbytes, walk.stride);
>
> kernel_neon_begin();
> - 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);
> kernel_neon_end();
> err = skcipher_walk_done(&walk, walk.nbytes - nbytes);
> }
> @@ -85,7 +87,7 @@ static int chacha20_neon_stream_xor(struct skcipher_request *req,
> 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);
> @@ -93,10 +95,10 @@ 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);
> @@ -110,12 +112,13 @@ 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[] = {
> @@ -133,8 +136,8 @@ 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",
> @@ -149,12 +152,12 @@ 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;
> @@ -162,14 +165,15 @@ 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");
> --
> 2.19.1.930.g4563a0d9d0-goog
>

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