Re: [PATCH net-next v6 07/23] zinc: ChaCha20 ARM and ARM64 implementations

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

On 25 September 2018 at 16:56, Jason A. Donenfeld <Jason@zx2c4.com> wrote:
> These wire Andy Polyakov's implementations up to the kernel for ARMv7,8
> NEON, and introduce Eric Biggers' ultra-fast scalar implementation for
> CPUs without NEON or for CPUs with slow NEON (Cortex-A5,7).
>
> This commit does the following:
>   - Adds the glue code for the assembly implementations.
>   - Renames the ARMv8 code into place, since it can at this point be
>     used wholesale.
>   - Merges Andy Polyakov's ARMv7 NEON code with Eric Biggers' <=ARMv7
>     scalar code.
>
> Commit note: Eric Biggers' scalar code is brand new, and quite possibly
> prematurely added to this commit, and so it may require a bit of revision.
>

Please put comments like this below the ---

> This commit delivers approximately the same or much better performance than
> the existing crypto API's code and has been measured to do as such on:
>
>   - ARM1176JZF-S [ARMv6]
>   - Cortex-A7    [ARMv7]
>   - Cortex-A8    [ARMv7]
>   - Cortex-A9    [ARMv7]
>   - Cortex-A17   [ARMv7]
>   - Cortex-A53   [ARMv8]
>   - Cortex-A55   [ARMv8]
>   - Cortex-A73   [ARMv8]
>   - Cortex-A75   [ARMv8]
>
> Interestingly, Andy Polyakov's scalar code is slower than Eric Biggers',
> but is also significantly shorter. This has the advantage that it does
> not evict other code from L1 cache -- particularly on ARM11 chips -- and
> so in certain circumstances it can actually be faster. However, it wasn't
> found that this had an affect on any code existing in the kernel today.
>
> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
> Co-authored-by: Eric Biggers <ebiggers@google.com>
> Cc: Samuel Neves <sneves@dei.uc.pt>
> Cc: Andy Lutomirski <luto@kernel.org>
> Cc: Greg KH <gregkh@linuxfoundation.org>
> Cc: Jean-Philippe Aumasson <jeanphilippe.aumasson@gmail.com>
> Cc: Russell King <linux@armlinux.org.uk>
> Cc: linux-arm-kernel@lists.infradead.org
> ---
>  lib/zinc/Makefile                             |   2 +
>  lib/zinc/chacha20/chacha20-arm-glue.h         |  88 +++
>  ...acha20-arm-cryptogams.S => chacha20-arm.S} | 502 ++++++++++++++++--
>  ...20-arm64-cryptogams.S => chacha20-arm64.S} |   0
>  lib/zinc/chacha20/chacha20.c                  |   2 +
>  5 files changed, 556 insertions(+), 38 deletions(-)
>  create mode 100644 lib/zinc/chacha20/chacha20-arm-glue.h
>  rename lib/zinc/chacha20/{chacha20-arm-cryptogams.S => chacha20-arm.S} (71%)
>  rename lib/zinc/chacha20/{chacha20-arm64-cryptogams.S => chacha20-arm64.S} (100%)
>
> diff --git a/lib/zinc/Makefile b/lib/zinc/Makefile
> index 223a0816c918..e47f64e12bbd 100644
> --- a/lib/zinc/Makefile
> +++ b/lib/zinc/Makefile
> @@ -4,4 +4,6 @@ ccflags-$(CONFIG_ZINC_DEBUG) += -DDEBUG
>
>  zinc_chacha20-y := chacha20/chacha20.o
>  zinc_chacha20-$(CONFIG_ZINC_ARCH_X86_64) += chacha20/chacha20-x86_64.o
> +zinc_chacha20-$(CONFIG_ZINC_ARCH_ARM) += chacha20/chacha20-arm.o
> +zinc_chacha20-$(CONFIG_ZINC_ARCH_ARM64) += chacha20/chacha20-arm64.o

Are these CONFIG_ symbols defined anywhere at this point?

In any case, I don't think these is a reason for these, at least not
on ARM/arm64. The 64-bitness is implied in both cases, and the
dependency on !CPU_32v3 you introduce (looking at the version of
Kconfig at the end of the series) seems spurious to me. Was that added
because of some kbuild robot report? (we don't support ARMv3 in the
kernel but ARCH_RPC is built in v3 mode because of historical reasons
while the actual core is a v4)

>  obj-$(CONFIG_ZINC_CHACHA20) += zinc_chacha20.o
> diff --git a/lib/zinc/chacha20/chacha20-arm-glue.h b/lib/zinc/chacha20/chacha20-arm-glue.h
> new file mode 100644
> index 000000000000..86cce851ed02
> --- /dev/null
> +++ b/lib/zinc/chacha20/chacha20-arm-glue.h
> @@ -0,0 +1,88 @@
> +/* SPDX-License-Identifier: GPL-2.0 OR MIT */
> +/*
> + * Copyright (C) 2015-2018 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
> + */
> +
> +#include <asm/hwcap.h>
> +#include <asm/neon.h>
> +#if defined(CONFIG_ARM)
> +#include <asm/system_info.h>
> +#include <asm/cputype.h>
> +#endif
> +
> +asmlinkage void chacha20_arm(u8 *out, const u8 *in, const size_t len,
> +                            const u32 key[8], const u32 counter[4]);
> +#if defined(CONFIG_ARM)
> +asmlinkage void hchacha20_arm(const u32 state[16], u32 out[8]);
> +#endif
> +#if defined(CONFIG_KERNEL_MODE_NEON)
> +asmlinkage void chacha20_neon(u8 *out, const u8 *in, const size_t len,
> +                             const u32 key[8], const u32 counter[4]);
> +#endif
> +

No need to make asmlinkage declarations conditional

> +static bool chacha20_use_neon __ro_after_init;
> +
> +static void __init chacha20_fpu_init(void)
> +{
> +#if defined(CONFIG_ARM64)
> +       chacha20_use_neon = elf_hwcap & HWCAP_ASIMD;
> +#elif defined(CONFIG_ARM)
> +       switch (read_cpuid_part()) {
> +       case ARM_CPU_PART_CORTEX_A7:
> +       case ARM_CPU_PART_CORTEX_A5:
> +               /* The Cortex-A7 and Cortex-A5 do not perform well with the NEON
> +                * implementation but do incredibly with the scalar one and use
> +                * less power.
> +                */
> +               break;
> +       default:
> +               chacha20_use_neon = elf_hwcap & HWCAP_NEON;
> +       }
> +#endif
> +}
> +
> +static inline bool chacha20_arch(struct chacha20_ctx *state, u8 *dst,
> +                                const u8 *src, size_t len,
> +                                simd_context_t *simd_context)
> +{
> +#if defined(CONFIG_KERNEL_MODE_NEON)

if (IS_ENABLED())

> +       if (chacha20_use_neon && len >= CHACHA20_BLOCK_SIZE * 3 &&
> +           simd_use(simd_context))
> +               chacha20_neon(dst, src, len, state->key, state->counter);
> +       else
> +#endif
> +               chacha20_arm(dst, src, len, state->key, state->counter);
> +
> +       state->counter[0] += (len + 63) / 64;
> +       return true;
> +}
> +
> +static inline bool hchacha20_arch(u32 derived_key[CHACHA20_KEY_WORDS],
> +                                 const u8 nonce[HCHACHA20_NONCE_SIZE],
> +                                 const u8 key[HCHACHA20_KEY_SIZE],
> +                                 simd_context_t *simd_context)
> +{
> +#if defined(CONFIG_ARM)
> +       u32 x[] = { CHACHA20_CONSTANT_EXPA,
> +                   CHACHA20_CONSTANT_ND_3,
> +                   CHACHA20_CONSTANT_2_BY,
> +                   CHACHA20_CONSTANT_TE_K,
> +                   get_unaligned_le32(key + 0),
> +                   get_unaligned_le32(key + 4),
> +                   get_unaligned_le32(key + 8),
> +                   get_unaligned_le32(key + 12),
> +                   get_unaligned_le32(key + 16),
> +                   get_unaligned_le32(key + 20),
> +                   get_unaligned_le32(key + 24),
> +                   get_unaligned_le32(key + 28),
> +                   get_unaligned_le32(nonce + 0),
> +                   get_unaligned_le32(nonce + 4),
> +                   get_unaligned_le32(nonce + 8),
> +                   get_unaligned_le32(nonce + 12)
> +       };
> +       hchacha20_arm(x, derived_key);

"""
if (!IS_ENABLED(CONFIG_ARM))
   return false;

hchacha20_arm(x, derived_key);
return true;
"""

and drop the #ifdefs


> +       return true;
> +#else
> +       return false;
> +#endif
> +}
> diff --git a/lib/zinc/chacha20/chacha20-arm-cryptogams.S b/lib/zinc/chacha20/chacha20-arm.S
> similarity index 71%
> rename from lib/zinc/chacha20/chacha20-arm-cryptogams.S
> rename to lib/zinc/chacha20/chacha20-arm.S
> index 770bab469171..5abedafcf129 100644
> --- a/lib/zinc/chacha20/chacha20-arm-cryptogams.S
> +++ b/lib/zinc/chacha20/chacha20-arm.S
> @@ -1,13 +1,475 @@
>  /* SPDX-License-Identifier: GPL-2.0 OR BSD-3-Clause */
>  /*
> + * Copyright (C) 2018 Google, Inc.
>   * Copyright (C) 2015-2018 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
>   * Copyright (C) 2006-2017 CRYPTOGAMS by <appro@openssl.org>. All Rights Reserved.
> - *
> - * This is based in part on Andy Polyakov's implementation from CRYPTOGAMS.
>   */
>
>  #include <linux/linkage.h>
>
> +/*
> + * The following scalar routine was written by Eric Biggers.
> + *
> + * Design notes:
> + *
> + * 16 registers would be needed to hold the state matrix, but only 14 are
> + * available because 'sp' and 'pc' cannot be used.  So we spill the elements
> + * (x8, x9) to the stack and swap them out with (x10, x11).  This adds one
> + * 'ldrd' and one 'strd' instruction per round.
> + *
> + * All rotates are performed using the implicit rotate operand accepted by the
> + * 'add' and 'eor' instructions.  This is faster than using explicit rotate
> + * instructions.  To make this work, we allow the values in the second and last
> + * rows of the ChaCha state matrix (rows 'b' and 'd') to temporarily have the
> + * wrong rotation amount.  The rotation amount is then fixed up just in time
> + * when the values are used.  'brot' is the number of bits the values in row 'b'
> + * need to be rotated right to arrive at the correct values, and 'drot'
> + * similarly for row 'd'.  (brot, drot) start out as (0, 0) but we make it such
> + * that they end up as (25, 24) after every round.
> + */
> +
> +       // ChaCha state registers
> +       X0      .req    r0
> +       X1      .req    r1
> +       X2      .req    r2
> +       X3      .req    r3
> +       X4      .req    r4
> +       X5      .req    r5
> +       X6      .req    r6
> +       X7      .req    r7
> +       X8_X10  .req    r8      // shared by x8 and x10
> +       X9_X11  .req    r9      // shared by x9 and x11
> +       X12     .req    r10
> +       X13     .req    r11
> +       X14     .req    r12
> +       X15     .req    r14
> +
> +.Lexpand_32byte_k:
> +       // "expand 32-byte k"
> +       .word   0x61707865, 0x3320646e, 0x79622d32, 0x6b206574
> +
> +#ifdef __thumb2__
> +#  define adrl adr
> +#endif
> +
> +.macro __rev           out, in,  t0, t1, t2
> +.if __LINUX_ARM_ARCH__ >= 6
> +       rev             \out, \in
> +.else
> +       lsl             \t0, \in, #24
> +       and             \t1, \in, #0xff00
> +       and             \t2, \in, #0xff0000
> +       orr             \out, \t0, \in, lsr #24
> +       orr             \out, \out, \t1, lsl #8
> +       orr             \out, \out, \t2, lsr #8
> +.endif
> +.endm
> +
> +.macro _le32_bswap     x,  t0, t1, t2
> +#ifdef __ARMEB__
> +       __rev           \x, \x,  \t0, \t1, \t2
> +#endif
> +.endm
> +
> +.macro _le32_bswap_4x  a, b, c, d,  t0, t1, t2
> +       _le32_bswap     \a,  \t0, \t1, \t2
> +       _le32_bswap     \b,  \t0, \t1, \t2
> +       _le32_bswap     \c,  \t0, \t1, \t2
> +       _le32_bswap     \d,  \t0, \t1, \t2
> +.endm
> +
> +.macro __ldrd          a, b, src, offset
> +#if __LINUX_ARM_ARCH__ >= 6
> +       ldrd            \a, \b, [\src, #\offset]
> +#else
> +       ldr             \a, [\src, #\offset]
> +       ldr             \b, [\src, #\offset + 4]
> +#endif
> +.endm
> +
> +.macro __strd          a, b, dst, offset
> +#if __LINUX_ARM_ARCH__ >= 6
> +       strd            \a, \b, [\dst, #\offset]
> +#else
> +       str             \a, [\dst, #\offset]
> +       str             \b, [\dst, #\offset + 4]
> +#endif
> +.endm
> +
> +.macro _halfround      a1, b1, c1, d1,  a2, b2, c2, d2
> +
> +       // a += b; d ^= a; d = rol(d, 16);
> +       add             \a1, \a1, \b1, ror #brot
> +       add             \a2, \a2, \b2, ror #brot
> +       eor             \d1, \a1, \d1, ror #drot
> +       eor             \d2, \a2, \d2, ror #drot
> +       // drot == 32 - 16 == 16
> +
> +       // c += d; b ^= c; b = rol(b, 12);
> +       add             \c1, \c1, \d1, ror #16
> +       add             \c2, \c2, \d2, ror #16
> +       eor             \b1, \c1, \b1, ror #brot
> +       eor             \b2, \c2, \b2, ror #brot
> +       // brot == 32 - 12 == 20
> +
> +       // a += b; d ^= a; d = rol(d, 8);
> +       add             \a1, \a1, \b1, ror #20
> +       add             \a2, \a2, \b2, ror #20
> +       eor             \d1, \a1, \d1, ror #16
> +       eor             \d2, \a2, \d2, ror #16
> +       // drot == 32 - 8 == 24
> +
> +       // c += d; b ^= c; b = rol(b, 7);
> +       add             \c1, \c1, \d1, ror #24
> +       add             \c2, \c2, \d2, ror #24
> +       eor             \b1, \c1, \b1, ror #20
> +       eor             \b2, \c2, \b2, ror #20
> +       // brot == 32 - 7 == 25
> +.endm
> +
> +.macro _doubleround
> +
> +       // column round
> +
> +       // quarterrounds: (x0, x4, x8, x12) and (x1, x5, x9, x13)
> +       _halfround      X0, X4, X8_X10, X12,  X1, X5, X9_X11, X13
> +
> +       // save (x8, x9); restore (x10, x11)
> +       __strd          X8_X10, X9_X11, sp, 0
> +       __ldrd          X8_X10, X9_X11, sp, 8
> +
> +       // quarterrounds: (x2, x6, x10, x14) and (x3, x7, x11, x15)
> +       _halfround      X2, X6, X8_X10, X14,  X3, X7, X9_X11, X15
> +
> +       .set brot, 25
> +       .set drot, 24
> +
> +       // diagonal round
> +
> +       // quarterrounds: (x0, x5, x10, x15) and (x1, x6, x11, x12)
> +       _halfround      X0, X5, X8_X10, X15,  X1, X6, X9_X11, X12
> +
> +       // save (x10, x11); restore (x8, x9)
> +       __strd          X8_X10, X9_X11, sp, 8
> +       __ldrd          X8_X10, X9_X11, sp, 0
> +
> +       // quarterrounds: (x2, x7, x8, x13) and (x3, x4, x9, x14)
> +       _halfround      X2, X7, X8_X10, X13,  X3, X4, X9_X11, X14
> +.endm
> +
> +.macro _chacha_permute nrounds
> +       .set brot, 0
> +       .set drot, 0
> +       .rept \nrounds / 2
> +        _doubleround
> +       .endr
> +.endm
> +
> +.macro _chacha         nrounds
> +
> +.Lnext_block\@:
> +       // Stack: unused0-unused1 x10-x11 x0-x15 OUT IN LEN
> +       // Registers contain x0-x9,x12-x15.
> +
> +       // Do the core ChaCha permutation to update x0-x15.
> +       _chacha_permute \nrounds
> +
> +       add             sp, #8
> +       // Stack: x10-x11 orig_x0-orig_x15 OUT IN LEN
> +       // Registers contain x0-x9,x12-x15.
> +       // x4-x7 are rotated by 'brot'; x12-x15 are rotated by 'drot'.
> +
> +       // Free up some registers (r8-r12,r14) by pushing (x8-x9,x12-x15).
> +       push            {X8_X10, X9_X11, X12, X13, X14, X15}
> +
> +       // Load (OUT, IN, LEN).
> +       ldr             r14, [sp, #96]
> +       ldr             r12, [sp, #100]
> +       ldr             r11, [sp, #104]
> +
> +       orr             r10, r14, r12
> +
> +       // Use slow path if fewer than 64 bytes remain.
> +       cmp             r11, #64
> +       blt             .Lxor_slowpath\@
> +
> +       // Use slow path if IN and/or OUT isn't 4-byte aligned.  Needed even on
> +       // ARMv6+, since ldmia and stmia (used below) still require alignment.
> +       tst             r10, #3
> +       bne             .Lxor_slowpath\@
> +
> +       // Fast path: XOR 64 bytes of aligned data.
> +
> +       // Stack: x8-x9 x12-x15 x10-x11 orig_x0-orig_x15 OUT IN LEN
> +       // Registers: r0-r7 are x0-x7; r8-r11 are free; r12 is IN; r14 is OUT.
> +       // x4-x7 are rotated by 'brot'; x12-x15 are rotated by 'drot'.
> +
> +       // x0-x3
> +       __ldrd          r8, r9, sp, 32
> +       __ldrd          r10, r11, sp, 40
> +       add             X0, X0, r8
> +       add             X1, X1, r9
> +       add             X2, X2, r10
> +       add             X3, X3, r11
> +       _le32_bswap_4x  X0, X1, X2, X3,  r8, r9, r10
> +       ldmia           r12!, {r8-r11}
> +       eor             X0, X0, r8
> +       eor             X1, X1, r9
> +       eor             X2, X2, r10
> +       eor             X3, X3, r11
> +       stmia           r14!, {X0-X3}
> +
> +       // x4-x7
> +       __ldrd          r8, r9, sp, 48
> +       __ldrd          r10, r11, sp, 56
> +       add             X4, r8, X4, ror #brot
> +       add             X5, r9, X5, ror #brot
> +       ldmia           r12!, {X0-X3}
> +       add             X6, r10, X6, ror #brot
> +       add             X7, r11, X7, ror #brot
> +       _le32_bswap_4x  X4, X5, X6, X7,  r8, r9, r10
> +       eor             X4, X4, X0
> +       eor             X5, X5, X1
> +       eor             X6, X6, X2
> +       eor             X7, X7, X3
> +       stmia           r14!, {X4-X7}
> +
> +       // x8-x15
> +       pop             {r0-r7}                 // (x8-x9,x12-x15,x10-x11)
> +       __ldrd          r8, r9, sp, 32
> +       __ldrd          r10, r11, sp, 40
> +       add             r0, r0, r8              // x8
> +       add             r1, r1, r9              // x9
> +       add             r6, r6, r10             // x10
> +       add             r7, r7, r11             // x11
> +       _le32_bswap_4x  r0, r1, r6, r7,  r8, r9, r10
> +       ldmia           r12!, {r8-r11}
> +       eor             r0, r0, r8              // x8
> +       eor             r1, r1, r9              // x9
> +       eor             r6, r6, r10             // x10
> +       eor             r7, r7, r11             // x11
> +       stmia           r14!, {r0,r1,r6,r7}
> +       ldmia           r12!, {r0,r1,r6,r7}
> +       __ldrd          r8, r9, sp, 48
> +       __ldrd          r10, r11, sp, 56
> +       add             r2, r8, r2, ror #drot   // x12
> +       add             r3, r9, r3, ror #drot   // x13
> +       add             r4, r10, r4, ror #drot  // x14
> +       add             r5, r11, r5, ror #drot  // x15
> +       _le32_bswap_4x  r2, r3, r4, r5,  r9, r10, r11
> +         ldr           r9, [sp, #72]           // load LEN
> +       eor             r2, r2, r0              // x12
> +       eor             r3, r3, r1              // x13
> +       eor             r4, r4, r6              // x14
> +       eor             r5, r5, r7              // x15
> +         subs          r9, #64                 // decrement and check LEN
> +       stmia           r14!, {r2-r5}
> +
> +       beq             .Ldone\@
> +
> +.Lprepare_for_next_block\@:
> +
> +       // Stack: x0-x15 OUT IN LEN
> +
> +       // Increment block counter (x12)
> +       add             r8, #1
> +
> +       // Store updated (OUT, IN, LEN)
> +       str             r14, [sp, #64]
> +       str             r12, [sp, #68]
> +       str             r9, [sp, #72]
> +
> +         mov           r14, sp
> +
> +       // Store updated block counter (x12)
> +       str             r8, [sp, #48]
> +
> +         sub           sp, #16
> +
> +       // Reload state and do next block
> +       ldmia           r14!, {r0-r11}          // load x0-x11
> +       __strd          r10, r11, sp, 8         // store x10-x11 before state
> +       ldmia           r14, {r10-r12,r14}      // load x12-x15
> +       b               .Lnext_block\@
> +
> +.Lxor_slowpath\@:
> +       // Slow path: < 64 bytes remaining, or unaligned input or output buffer.
> +       // We handle it by storing the 64 bytes of keystream to the stack, then
> +       // XOR-ing the needed portion with the data.
> +
> +       // Allocate keystream buffer
> +       sub             sp, #64
> +       mov             r14, sp
> +
> +       // Stack: ks0-ks15 x8-x9 x12-x15 x10-x11 orig_x0-orig_x15 OUT IN LEN
> +       // Registers: r0-r7 are x0-x7; r8-r11 are free; r12 is IN; r14 is &ks0.
> +       // x4-x7 are rotated by 'brot'; x12-x15 are rotated by 'drot'.
> +
> +       // Save keystream for x0-x3
> +       __ldrd          r8, r9, sp, 96
> +       __ldrd          r10, r11, sp, 104
> +       add             X0, X0, r8
> +       add             X1, X1, r9
> +       add             X2, X2, r10
> +       add             X3, X3, r11
> +       _le32_bswap_4x  X0, X1, X2, X3,  r8, r9, r10
> +       stmia           r14!, {X0-X3}
> +
> +       // Save keystream for x4-x7
> +       __ldrd          r8, r9, sp, 112
> +       __ldrd          r10, r11, sp, 120
> +       add             X4, r8, X4, ror #brot
> +       add             X5, r9, X5, ror #brot
> +       add             X6, r10, X6, ror #brot
> +       add             X7, r11, X7, ror #brot
> +       _le32_bswap_4x  X4, X5, X6, X7,  r8, r9, r10
> +         add           r8, sp, #64
> +       stmia           r14!, {X4-X7}
> +
> +       // Save keystream for x8-x15
> +       ldm             r8, {r0-r7}             // (x8-x9,x12-x15,x10-x11)
> +       __ldrd          r8, r9, sp, 128
> +       __ldrd          r10, r11, sp, 136
> +       add             r0, r0, r8              // x8
> +       add             r1, r1, r9              // x9
> +       add             r6, r6, r10             // x10
> +       add             r7, r7, r11             // x11
> +       _le32_bswap_4x  r0, r1, r6, r7,  r8, r9, r10
> +       stmia           r14!, {r0,r1,r6,r7}
> +       __ldrd          r8, r9, sp, 144
> +       __ldrd          r10, r11, sp, 152
> +       add             r2, r8, r2, ror #drot   // x12
> +       add             r3, r9, r3, ror #drot   // x13
> +       add             r4, r10, r4, ror #drot  // x14
> +       add             r5, r11, r5, ror #drot  // x15
> +       _le32_bswap_4x  r2, r3, r4, r5,  r9, r10, r11
> +       stmia           r14, {r2-r5}
> +
> +       // Stack: ks0-ks15 unused0-unused7 x0-x15 OUT IN LEN
> +       // Registers: r8 is block counter, r12 is IN.
> +
> +       ldr             r9, [sp, #168]          // LEN
> +       ldr             r14, [sp, #160]         // OUT
> +       cmp             r9, #64
> +         mov           r0, sp
> +       movle           r1, r9
> +       movgt           r1, #64
> +       // r1 is number of bytes to XOR, in range [1, 64]
> +
> +.if __LINUX_ARM_ARCH__ < 6
> +       orr             r2, r12, r14
> +       tst             r2, #3                  // IN or OUT misaligned?
> +       bne             .Lxor_next_byte\@
> +.endif
> +
> +       // XOR a word at a time
> +.rept 16
> +       subs            r1, #4
> +       blt             .Lxor_words_done\@
> +       ldr             r2, [r12], #4
> +       ldr             r3, [r0], #4
> +       eor             r2, r2, r3
> +       str             r2, [r14], #4
> +.endr
> +       b               .Lxor_slowpath_done\@
> +.Lxor_words_done\@:
> +       ands            r1, r1, #3
> +       beq             .Lxor_slowpath_done\@
> +
> +       // XOR a byte at a time
> +.Lxor_next_byte\@:
> +       ldrb            r2, [r12], #1
> +       ldrb            r3, [r0], #1
> +       eor             r2, r2, r3
> +       strb            r2, [r14], #1
> +       subs            r1, #1
> +       bne             .Lxor_next_byte\@
> +
> +.Lxor_slowpath_done\@:
> +       subs            r9, #64
> +       add             sp, #96
> +       bgt             .Lprepare_for_next_block\@
> +
> +.Ldone\@:
> +.endm  // _chacha
> +
> +/*
> + * void chacha20_arm(u8 *out, const u8 *in, size_t len, const u32 key[8],
> + *                  const u32 iv[4]);
> + */
> +ENTRY(chacha20_arm)
> +       cmp             r2, #0                  // len == 0?
> +       bxeq            lr
> +
> +       push            {r0-r2,r4-r11,lr}
> +
> +       // Push state x0-x15 onto stack.
> +       // Also store an extra copy of x10-x11 just before the state.
> +
> +       ldr             r4, [sp, #48]           // iv
> +       mov             r0, sp
> +       sub             sp, #80
> +
> +       // iv: x12-x15
> +       ldm             r4, {X12,X13,X14,X15}
> +       stmdb           r0!, {X12,X13,X14,X15}
> +
> +       // key: x4-x11
> +       __ldrd          X8_X10, X9_X11, r3, 24
> +       __strd          X8_X10, X9_X11, sp, 8
> +       stmdb           r0!, {X8_X10, X9_X11}
> +       ldm             r3, {X4-X9_X11}
> +       stmdb           r0!, {X4-X9_X11}
> +
> +       // constants: x0-x3
> +       adrl            X3, .Lexpand_32byte_k
> +       ldm             X3, {X0-X3}
> +       __strd          X0, X1, sp, 16
> +       __strd          X2, X3, sp, 24
> +
> +       _chacha         20
> +
> +       add             sp, #76
> +       pop             {r4-r11, pc}
> +ENDPROC(chacha20_arm)
> +
> +/*
> + * void hchacha20_arm(const u32 state[16], u32 out[8]);
> + */
> +ENTRY(hchacha20_arm)
> +       push            {r1,r4-r11,lr}
> +
> +       mov             r14, r0
> +       ldmia           r14!, {r0-r11}          // load x0-x11
> +       push            {r10-r11}               // store x10-x11 to stack
> +       ldm             r14, {r10-r12,r14}      // load x12-x15
> +       sub             sp, #8
> +
> +       _chacha_permute 20
> +
> +       // Skip over (unused0-unused1, x10-x11)
> +       add             sp, #16
> +
> +       // Fix up rotations of x12-x15
> +       ror             X12, X12, #drot
> +       ror             X13, X13, #drot
> +         pop           {r4}                    // load 'out'
> +       ror             X14, X14, #drot
> +       ror             X15, X15, #drot
> +
> +       // Store (x0-x3,x12-x15) to 'out'
> +       stm             r4, {X0,X1,X2,X3,X12,X13,X14,X15}
> +
> +       pop             {r4-r11,pc}
> +ENDPROC(hchacha20_arm)
> +
> +#ifdef CONFIG_KERNEL_MODE_NEON
> +/*
> + * This following NEON routine was ported from Andy Polyakov's implementation
> + * from CRYPTOGAMS. It begins with parts of the CRYPTOGAMS scalar routine,
> + * since certain NEON code paths actually branch to it.
> + */
> +
>  .text
>  #if defined(__thumb2__) || defined(__clang__)
>  .syntax        unified
> @@ -22,39 +484,6 @@
>  #define ldrhsb ldrbhs
>  #endif
>
> -.align 5
> -.Lsigma:
> -.long  0x61707865,0x3320646e,0x79622d32,0x6b206574     @ endian-neutral
> -.Lone:
> -.long  1,0,0,0
> -.word  -1
> -
> -.align 5
> -ENTRY(chacha20_arm)
> -       ldr     r12,[sp,#0]             @ pull pointer to counter and nonce
> -       stmdb   sp!,{r0-r2,r4-r11,lr}
> -       cmp     r2,#0                   @ len==0?
> -#ifdef __thumb2__
> -       itt     eq
> -#endif
> -       addeq   sp,sp,#4*3
> -       beq     .Lno_data_arm
> -       ldmia   r12,{r4-r7}             @ load counter and nonce
> -       sub     sp,sp,#4*(16)           @ off-load area
> -#if __LINUX_ARM_ARCH__ < 7 && !defined(__thumb2__)
> -       sub     r14,pc,#100             @ .Lsigma
> -#else
> -       adr     r14,.Lsigma             @ .Lsigma
> -#endif
> -       stmdb   sp!,{r4-r7}             @ copy counter and nonce
> -       ldmia   r3,{r4-r11}             @ load key
> -       ldmia   r14,{r0-r3}             @ load sigma
> -       stmdb   sp!,{r4-r11}            @ copy key
> -       stmdb   sp!,{r0-r3}             @ copy sigma
> -       str     r10,[sp,#4*(16+10)]     @ off-load "rx"
> -       str     r11,[sp,#4*(16+11)]     @ off-load "rx"
> -       b       .Loop_outer_enter
> -
>  .align 4
>  .Loop_outer:
>         ldmia   sp,{r0-r9}              @ load key material
> @@ -748,11 +1177,8 @@ ENTRY(chacha20_arm)
>
>  .Ldone:
>         add     sp,sp,#4*(32+3)
> -.Lno_data_arm:
>         ldmia   sp!,{r4-r11,pc}
> -ENDPROC(chacha20_arm)
>
> -#ifdef CONFIG_KERNEL_MODE_NEON
>  .align 5
>  .Lsigma2:
>  .long  0x61707865,0x3320646e,0x79622d32,0x6b206574     @ endian-neutral
> diff --git a/lib/zinc/chacha20/chacha20-arm64-cryptogams.S b/lib/zinc/chacha20/chacha20-arm64.S
> similarity index 100%
> rename from lib/zinc/chacha20/chacha20-arm64-cryptogams.S
> rename to lib/zinc/chacha20/chacha20-arm64.S
> diff --git a/lib/zinc/chacha20/chacha20.c b/lib/zinc/chacha20/chacha20.c
> index 4354b874a6a5..fc4f74fca653 100644
> --- a/lib/zinc/chacha20/chacha20.c
> +++ b/lib/zinc/chacha20/chacha20.c
> @@ -16,6 +16,8 @@
>
>  #if defined(CONFIG_ZINC_ARCH_X86_64)
>  #include "chacha20-x86_64-glue.h"
> +#elif defined(CONFIG_ZINC_ARCH_ARM) || defined(CONFIG_ZINC_ARCH_ARM64)

As above, just use CONFIG_ARM / CONFIG_ARM64 directly

> +#include "chacha20-arm-glue.h"
>  #else
>  void __init chacha20_fpu_init(void)
>  {
> --
> 2.19.0
>