Re: [PATCH 2/4] crypto: arm64/chacha20 - add XChaCha20 support

From: Ard Biesheuvel
Date: Fri Nov 30 2018 - 08:02:21 EST

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In reply to: Eric Biggers: "[PATCH 2/4] crypto: arm64/chacha20 - add XChaCha20 support"
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On Thu, 29 Nov 2018 at 07:35, Eric Biggers <ebiggers@xxxxxxxxxx> wrote:
>
> From: Eric Biggers <ebiggers@xxxxxxxxxx>
>
> Add an XChaCha20 implementation that is hooked up to the ARM64 NEON
> implementation of ChaCha20. This can be used by Adiantum.
>
> A NEON implementation of single-block HChaCha20 is also added so that
> XChaCha20 can use it rather than the generic implementation. This
> required refactoring the ChaCha permutation into its own function.
>
> Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx>
> ---
> arch/arm64/crypto/Kconfig | 2 +-
> arch/arm64/crypto/chacha20-neon-core.S | 62 ++++++++++-----
> arch/arm64/crypto/chacha20-neon-glue.c | 101 +++++++++++++++++++------
> 3 files changed, 121 insertions(+), 44 deletions(-)
>
> diff --git a/arch/arm64/crypto/Kconfig b/arch/arm64/crypto/Kconfig
> index 3f5aeb786192b..d54ddb8468ef5 100644
> --- a/arch/arm64/crypto/Kconfig
> +++ b/arch/arm64/crypto/Kconfig
> @@ -101,7 +101,7 @@ config CRYPTO_AES_ARM64_NEON_BLK
> select CRYPTO_SIMD
>
> config CRYPTO_CHACHA20_NEON
> - tristate "NEON accelerated ChaCha20 symmetric cipher"
> + tristate "ChaCha20 and XChaCha20 stream ciphers using NEON instructions"
> depends on KERNEL_MODE_NEON
> select CRYPTO_BLKCIPHER
> select CRYPTO_CHACHA20
> diff --git a/arch/arm64/crypto/chacha20-neon-core.S b/arch/arm64/crypto/chacha20-neon-core.S
> index 13c85e272c2a1..378850505c0ae 100644
> --- a/arch/arm64/crypto/chacha20-neon-core.S
> +++ b/arch/arm64/crypto/chacha20-neon-core.S
> @@ -23,25 +23,20 @@
> .text
> .align 6
>
> -ENTRY(chacha20_block_xor_neon)
> - // x0: Input state matrix, s
> - // x1: 1 data block output, o
> - // x2: 1 data block input, i
> -
> - //
> - // This function encrypts one ChaCha20 block by loading the state matrix
> - // in four NEON registers. It performs matrix operation on four words in
> - // parallel, but requires shuffling to rearrange the words after each
> - // round.
> - //
> -
> - // x0..3 = s0..3
> - adr x3, ROT8
> - ld1 {v0.4s-v3.4s}, [x0]
> - ld1 {v8.4s-v11.4s}, [x0]
> - ld1 {v12.4s}, [x3]
> +/*
> + * chacha20_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
> + */
> +chacha20_permute:
>
> mov x3, #10
> + adr x10, ROT8
> + ld1 {v12.4s}, [x10]
>
> .Ldoubleround:
> // x0 += x1, x3 = rotl32(x3 ^ x0, 16)
> @@ -105,6 +100,22 @@ ENTRY(chacha20_block_xor_neon)
> subs x3, x3, #1
> b.ne .Ldoubleround
>
> + ret
> +ENDPROC(chacha20_permute)
> +
> +ENTRY(chacha20_block_xor_neon)
> + // x0: Input state matrix, s
> + // x1: 1 data block output, o
> + // x2: 1 data block input, i
> +
> + mov x9, lr

please use x30 not lr. The latter is not supported by all assemblers

Also, I'd prefer it if we could create a full stack frame here, i.e.,

stp x29, x30, [sp, #-16]!
mov x29, sp

(same for the other caller)

Otherwise, this will look like a tail call to the unwinder,
potentially creating problems with features that need reliable
backtraces, such as livepatch.

> +
> + // x0..3 = s0..3
> + ld1 {v0.4s-v3.4s}, [x0]
> + ld1 {v8.4s-v11.4s}, [x0]
> +
> + bl chacha20_permute
> +
> ld1 {v4.16b-v7.16b}, [x2]
>
> // o0 = i0 ^ (x0 + s0)
> @@ -125,9 +136,24 @@ ENTRY(chacha20_block_xor_neon)
>
> st1 {v0.16b-v3.16b}, [x1]
>
> - ret
> + ret x9
> ENDPROC(chacha20_block_xor_neon)
>
> +ENTRY(hchacha20_block_neon)
> + // x0: Input state matrix, s
> + // x1: output (8 32-bit words)
> + mov x9, lr
> +
> + ld1 {v0.4s-v3.4s}, [x0]
> +
> + bl chacha20_permute
> +
> + st1 {v0.16b}, [x1], #16
> + st1 {v3.16b}, [x1]
> +
> + ret x9
> +ENDPROC(hchacha20_block_neon)
> +
> .align 6
> ENTRY(chacha20_4block_xor_neon)
> // x0: Input state matrix, s
> diff --git a/arch/arm64/crypto/chacha20-neon-glue.c b/arch/arm64/crypto/chacha20-neon-glue.c
> index 96e0cfb8c3f5b..a5b9cbc0c4de4 100644
> --- a/arch/arm64/crypto/chacha20-neon-glue.c
> +++ b/arch/arm64/crypto/chacha20-neon-glue.c
> @@ -30,6 +30,7 @@
>
> 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)
> @@ -65,20 +66,16 @@ static void chacha20_doneon(u32 *state, u8 *dst, const u8 *src,
> kernel_neon_end();
> }
>
> -static int chacha20_neon(struct skcipher_request *req)
> +static int chacha20_neon_stream_xor(struct skcipher_request *req,
> + struct chacha_ctx *ctx, u8 *iv)
> {
> - struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
> - struct chacha_ctx *ctx = crypto_skcipher_ctx(tfm);
> struct skcipher_walk walk;
> u32 state[16];
> int err;
>
> - if (!may_use_simd() || req->cryptlen <= CHACHA_BLOCK_SIZE)
> - return crypto_chacha_crypt(req);
> -
> err = skcipher_walk_virt(&walk, req, false);
>
> - crypto_chacha_init(state, ctx, walk.iv);
> + crypto_chacha_init(state, ctx, iv);
>
> while (walk.nbytes > 0) {
> unsigned int nbytes = walk.nbytes;
> @@ -94,22 +91,73 @@ static int chacha20_neon(struct skcipher_request *req)
> return err;
> }
>
> -static struct skcipher_alg alg = {
> - .base.cra_name = "chacha20",
> - .base.cra_driver_name = "chacha20-neon",
> - .base.cra_priority = 300,
> - .base.cra_blocksize = 1,
> - .base.cra_ctxsize = sizeof(struct chacha_ctx),
> - .base.cra_module = THIS_MODULE,
> -
> - .min_keysize = CHACHA_KEY_SIZE,
> - .max_keysize = CHACHA_KEY_SIZE,
> - .ivsize = CHACHA_IV_SIZE,
> - .chunksize = CHACHA_BLOCK_SIZE,
> - .walksize = 4 * CHACHA_BLOCK_SIZE,
> - .setkey = crypto_chacha20_setkey,
> - .encrypt = chacha20_neon,
> - .decrypt = chacha20_neon,
> +static int chacha20_neon(struct skcipher_request *req)
> +{
> + struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
> + struct chacha_ctx *ctx = crypto_skcipher_ctx(tfm);
> +
> + if (req->cryptlen <= CHACHA_BLOCK_SIZE || !may_use_simd())
> + return crypto_chacha_crypt(req);
> +
> + return chacha20_neon_stream_xor(req, ctx, req->iv);
> +}
> +
> +static int xchacha20_neon(struct skcipher_request *req)
> +{
> + struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
> + struct chacha_ctx *ctx = crypto_skcipher_ctx(tfm);
> + struct chacha_ctx subctx;
> + u32 state[16];
> + u8 real_iv[16];
> +
> + if (req->cryptlen <= CHACHA_BLOCK_SIZE || !may_use_simd())
> + return crypto_xchacha_crypt(req);
> +
> + crypto_chacha_init(state, ctx, req->iv);
> +
> + kernel_neon_begin();
> + hchacha20_block_neon(state, subctx.key);
> + kernel_neon_end();
> +
> + 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);
> +}
> +
> +static struct skcipher_alg algs[] = {
> + {
> + .base.cra_name = "chacha20",
> + .base.cra_driver_name = "chacha20-neon",
> + .base.cra_priority = 300,
> + .base.cra_blocksize = 1,
> + .base.cra_ctxsize = sizeof(struct chacha_ctx),
> + .base.cra_module = THIS_MODULE,
> +
> + .min_keysize = CHACHA_KEY_SIZE,
> + .max_keysize = CHACHA_KEY_SIZE,
> + .ivsize = CHACHA_IV_SIZE,
> + .chunksize = CHACHA_BLOCK_SIZE,
> + .walksize = 4 * CHACHA_BLOCK_SIZE,
> + .setkey = crypto_chacha20_setkey,
> + .encrypt = chacha20_neon,
> + .decrypt = chacha20_neon,
> + }, {
> + .base.cra_name = "xchacha20",
> + .base.cra_driver_name = "xchacha20-neon",
> + .base.cra_priority = 300,
> + .base.cra_blocksize = 1,
> + .base.cra_ctxsize = sizeof(struct chacha_ctx),
> + .base.cra_module = THIS_MODULE,
> +
> + .min_keysize = CHACHA_KEY_SIZE,
> + .max_keysize = CHACHA_KEY_SIZE,
> + .ivsize = XCHACHA_IV_SIZE,
> + .chunksize = CHACHA_BLOCK_SIZE,
> + .walksize = 4 * CHACHA_BLOCK_SIZE,
> + .setkey = crypto_chacha20_setkey,
> + .encrypt = xchacha20_neon,
> + .decrypt = xchacha20_neon,
> + }
> };
>
> static int __init chacha20_simd_mod_init(void)
> @@ -117,12 +165,12 @@ static int __init chacha20_simd_mod_init(void)
> if (!(elf_hwcap & HWCAP_ASIMD))
> return -ENODEV;
>
> - return crypto_register_skcipher(&alg);
> + return crypto_register_skciphers(algs, ARRAY_SIZE(algs));
> }
>
> static void __exit chacha20_simd_mod_fini(void)
> {
> - crypto_unregister_skcipher(&alg);
> + crypto_unregister_skciphers(algs, ARRAY_SIZE(algs));
> }
>
> module_init(chacha20_simd_mod_init);
> @@ -131,3 +179,6 @@ module_exit(chacha20_simd_mod_fini);
> MODULE_AUTHOR("Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>");
> MODULE_LICENSE("GPL v2");
> MODULE_ALIAS_CRYPTO("chacha20");
> +MODULE_ALIAS_CRYPTO("chacha20-neon");
> +MODULE_ALIAS_CRYPTO("xchacha20");
> +MODULE_ALIAS_CRYPTO("xchacha20-neon");
> --
> 2.19.2
>

Next message: Ard Biesheuvel: "Re: [PATCH 3/4] crypto: arm64/chacha20 - refactor to allow varying number of rounds"
Previous message: Maxime Coquelin: "Re: [PATCH net-next v3 01/13] virtio: add packed ring types and macros"
In reply to: Eric Biggers: "[PATCH 2/4] crypto: arm64/chacha20 - add XChaCha20 support"
Next in thread: Eric Biggers: "[PATCH 3/4] crypto: arm64/chacha20 - refactor to allow varying number of rounds"
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