Re: [RFC PATCH v2 10/12] crypto: arm/nhpoly1305 - add NEON-accelerated NHPoly1305

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

On 20 October 2018 at 13:51, Eric Biggers <ebiggers@kernel.org> wrote:
> On Sat, Oct 20, 2018 at 12:12:56PM +0800, Ard Biesheuvel wrote:
>> On 16 October 2018 at 01:54, Eric Biggers <ebiggers@kernel.org> wrote:
>> > From: Eric Biggers <ebiggers@google.com>
>> >
>> > Add an ARM NEON implementation of NHPoly1305, an ε-almost-∆-universal
>> > hash function used in the Adiantum encryption mode.  For now, only the
>> > NH portion is actually NEON-accelerated; the Poly1305 part is less
>> > performance-critical so is just implemented in C.
>> >
>> > Signed-off-by: Eric Biggers <ebiggers@google.com>
>> > ---
>> >  arch/arm/crypto/Kconfig                |   5 ++
>> >  arch/arm/crypto/Makefile               |   2 +
>> >  arch/arm/crypto/nh-neon-core.S         | 116 +++++++++++++++++++++++++
>> >  arch/arm/crypto/nhpoly1305-neon-glue.c |  78 +++++++++++++++++
>> >  4 files changed, 201 insertions(+)
>> >  create mode 100644 arch/arm/crypto/nh-neon-core.S
>> >  create mode 100644 arch/arm/crypto/nhpoly1305-neon-glue.c
>> >
>> > diff --git a/arch/arm/crypto/Kconfig b/arch/arm/crypto/Kconfig
>> > index cc932d9bba561..458562a34aabe 100644
>> > --- a/arch/arm/crypto/Kconfig
>> > +++ b/arch/arm/crypto/Kconfig
>> > @@ -122,4 +122,9 @@ config CRYPTO_CHACHA20_NEON
>> >         select CRYPTO_BLKCIPHER
>> >         select CRYPTO_CHACHA20
>> >
>> > +config CRYPTO_NHPOLY1305_NEON
>> > +       tristate "NEON accelerated NHPoly1305 hash function (for Adiantum)"
>> > +       depends on KERNEL_MODE_NEON
>> > +       select CRYPTO_NHPOLY1305
>> > +
>> >  endif
>> > diff --git a/arch/arm/crypto/Makefile b/arch/arm/crypto/Makefile
>> > index 005482ff95047..b65d6bfab8e6b 100644
>> > --- a/arch/arm/crypto/Makefile
>> > +++ b/arch/arm/crypto/Makefile
>> > @@ -10,6 +10,7 @@ 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) += chacha-neon.o
>> > +obj-$(CONFIG_CRYPTO_NHPOLY1305_NEON) += nhpoly1305-neon.o
>> >
>> >  ce-obj-$(CONFIG_CRYPTO_AES_ARM_CE) += aes-arm-ce.o
>> >  ce-obj-$(CONFIG_CRYPTO_SHA1_ARM_CE) += sha1-arm-ce.o
>> > @@ -53,6 +54,7 @@ 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
>> > +nhpoly1305-neon-y := nh-neon-core.o nhpoly1305-neon-glue.o
>> >
>> >  ifdef REGENERATE_ARM_CRYPTO
>> >  quiet_cmd_perl = PERL    $@
>> > diff --git a/arch/arm/crypto/nh-neon-core.S b/arch/arm/crypto/nh-neon-core.S
>> > new file mode 100644
>> > index 0000000000000..434d80ab531c2
>> > --- /dev/null
>> > +++ b/arch/arm/crypto/nh-neon-core.S
>> > @@ -0,0 +1,116 @@
>> > +/* SPDX-License-Identifier: GPL-2.0 */
>> > +/*
>> > + * NH - ε-almost-universal hash function, NEON accelerated version
>> > + *
>> > + * Copyright 2018 Google LLC
>> > + *
>> > + * Author: Eric Biggers <ebiggers@google.com>
>> > + */
>> > +
>> > +#include <linux/linkage.h>
>> > +
>> > +       .text
>> > +       .fpu            neon
>> > +
>> > +       KEY             .req    r0
>> > +       MESSAGE         .req    r1
>> > +       MESSAGE_LEN     .req    r2
>> > +       HASH            .req    r3
>> > +
>> > +       PASS0_SUMS      .req    q0
>> > +       PASS0_SUM_A     .req    d0
>> > +       PASS0_SUM_B     .req    d1
>> > +       PASS1_SUMS      .req    q1
>> > +       PASS1_SUM_A     .req    d2
>> > +       PASS1_SUM_B     .req    d3
>> > +       PASS2_SUMS      .req    q2
>> > +       PASS2_SUM_A     .req    d4
>> > +       PASS2_SUM_B     .req    d5
>> > +       PASS3_SUMS      .req    q3
>> > +       PASS3_SUM_A     .req    d6
>> > +       PASS3_SUM_B     .req    d7
>> > +       K0              .req    q4
>> > +       K1              .req    q5
>> > +       K2              .req    q6
>> > +       K3              .req    q7
>> > +       T0              .req    q8
>> > +       T0_L            .req    d16
>> > +       T0_H            .req    d17
>> > +       T1              .req    q9
>> > +       T1_L            .req    d18
>> > +       T1_H            .req    d19
>> > +       T2              .req    q10
>> > +       T2_L            .req    d20
>> > +       T2_H            .req    d21
>> > +       T3              .req    q11
>> > +       T3_L            .req    d22
>> > +       T3_H            .req    d23
>> > +
>> > +.macro _nh_stride      k0, k1, k2, k3
>> > +
>> > +       // Load next message stride
>> > +       vld1.8          {T3}, [MESSAGE]!
>> > +
>> > +       // Load next key stride
>> > +       vld1.32         {\k3}, [KEY]!
>> > +
>> > +       // Add message words to key words
>> > +       vadd.u32        T0, T3, \k0
>> > +       vadd.u32        T1, T3, \k1
>> > +       vadd.u32        T2, T3, \k2
>> > +       vadd.u32        T3, T3, \k3
>> > +
>> > +       // Multiply 32x32 => 64 and accumulate
>> > +       vmlal.u32       PASS0_SUMS, T0_L, T0_H
>> > +       vmlal.u32       PASS1_SUMS, T1_L, T1_H
>> > +       vmlal.u32       PASS2_SUMS, T2_L, T2_H
>> > +       vmlal.u32       PASS3_SUMS, T3_L, T3_H
>> > +.endm
>> > +
>>
>> Since we seem to have some spare NEON registers: would it help to have
>> a double round version of this macro?
>>
>
> It helps a little bit, but not much.  The loads are the only part that can be
> optimized further.  I think I'd rather have the shorter + simpler version,
> unless the loads can be optimized significantly more on other processors.
>
> Also, originally I had it loading the key and message for the next stride while
> doing the current one, but that didn't seem worthwhile either.
>

Fair enough.

>> > +/*
>> > + * void nh_neon(const u32 *key, const u8 *message, size_t message_len,
>> > + *             u8 hash[NH_HASH_BYTES])
>> > + *
>> > + * It's guaranteed that message_len % 16 == 0.
>> > + */
>> > +ENTRY(nh_neon)
>> > +
>> > +       vld1.32         {K0,K1}, [KEY]!
>> > +         vmov.u64      PASS0_SUMS, #0
>> > +         vmov.u64      PASS1_SUMS, #0
>> > +       vld1.32         {K2}, [KEY]!
>> > +         vmov.u64      PASS2_SUMS, #0
>> > +         vmov.u64      PASS3_SUMS, #0
>> > +
>> > +       subs            MESSAGE_LEN, MESSAGE_LEN, #64
>> > +       blt             .Lloop4_done
>> > +.Lloop4:
>> > +       _nh_stride      K0, K1, K2, K3
>> > +       _nh_stride      K1, K2, K3, K0
>> > +       _nh_stride      K2, K3, K0, K1
>> > +       _nh_stride      K3, K0, K1, K2
>> > +       subs            MESSAGE_LEN, MESSAGE_LEN, #64
>> > +       bge             .Lloop4
>> > +
>> > +.Lloop4_done:
>> > +       ands            MESSAGE_LEN, MESSAGE_LEN, #63
>> > +       beq             .Ldone
>> > +       _nh_stride      K0, K1, K2, K3
>> > +
>> > +       subs            MESSAGE_LEN, MESSAGE_LEN, #16
>> > +       beq             .Ldone
>> > +       _nh_stride      K1, K2, K3, K0
>> > +
>> > +       subs            MESSAGE_LEN, MESSAGE_LEN, #16
>> > +       beq             .Ldone
>> > +       _nh_stride      K2, K3, K0, K1
>> > +
>> > +.Ldone:
>> > +       // Sum the accumulators for each pass, then store the sums to 'hash'
>> > +       vadd.u64        T0_L, PASS0_SUM_A, PASS0_SUM_B
>> > +       vadd.u64        T0_H, PASS1_SUM_A, PASS1_SUM_B
>> > +       vadd.u64        T1_L, PASS2_SUM_A, PASS2_SUM_B
>> > +       vadd.u64        T1_H, PASS3_SUM_A, PASS3_SUM_B
>> > +       vst1.8          {T0-T1}, [HASH]
>> > +       bx              lr
>> > +ENDPROC(nh_neon)
>> > diff --git a/arch/arm/crypto/nhpoly1305-neon-glue.c b/arch/arm/crypto/nhpoly1305-neon-glue.c
>> > new file mode 100644
>> > index 0000000000000..df48a00f4c50f
>> > --- /dev/null
>> > +++ b/arch/arm/crypto/nhpoly1305-neon-glue.c
>> > @@ -0,0 +1,78 @@
>> > +// SPDX-License-Identifier: GPL-2.0
>> > +/*
>> > + * NHPoly1305 - ε-almost-∆-universal hash function for Adiantum
>> > + * (NEON accelerated version)
>> > + *
>> > + * Copyright 2018 Google LLC
>> > + */
>> > +
>> > +#include <asm/neon.h>
>> > +#include <asm/simd.h>
>> > +#include <crypto/internal/hash.h>
>> > +#include <crypto/nhpoly1305.h>
>> > +#include <linux/module.h>
>> > +
>> > +asmlinkage void nh_neon(const u32 *key, const u8 *message, size_t message_len,
>> > +                       u8 hash[NH_HASH_BYTES]);
>> > +
>> > +static void _nh_neon(const u32 *key, const u8 *message, size_t message_len,
>> > +                    __le64 hash[NH_NUM_PASSES])
>> > +{
>> > +       nh_neon(key, message, message_len, (u8 *)hash);
>> > +}
>> > +
>>
>> Why do we need this function?
>>
>
> For now it's not needed so I should probably just remove it, but it seems likely
> that indirect calls to assembly functions in the kernel will be going away in
> order to add support for CFI (control flow integrity).  The android-4.9 and
> android-4.14 kernels support CFI on arm64, so you might notice that some of the
> arm64 crypto code had to be patched for this reason.
>

I didn't actually look at those kernel trees so I hadn't noticed yet.
In any case, I'd suggest that we just keep this wrapper then, but
please add a comment describing why it's there.