Merge tag 'block-5.11-2021-01-16' of git://git.kernel.dk/linux-block

[linux/fpc-iii.git] / lib / crypto / curve25519-hacl64.c

// SPDX-License-Identifier: GPL-2.0 OR MIT
/*
 * Copyright (C) 2016-2017 INRIA and Microsoft Corporation.
 * Copyright (C) 2018-2019 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
 *
 * This is a machine-generated formally verified implementation of Curve25519
 * ECDH from: <https://github.com/mitls/hacl-star>. Though originally machine
 * generated, it has been tweaked to be suitable for use in the kernel. It is
 * optimized for 64-bit machines that can efficiently work with 128-bit
 * integer types.
 */

#include <asm/unaligned.h>
#include <crypto/curve25519.h>
#include <linux/string.h>

typedef __uint128_t u128;

static __always_inline u64 u64_eq_mask(u64 a, u64 b)
{
        u64 x = a ^ b;
        u64 minus_x = ~x + (u64)1U;
        u64 x_or_minus_x = x | minus_x;
        u64 xnx = x_or_minus_x >> (u32)63U;
        u64 c = xnx - (u64)1U;
        return c;
}

static __always_inline u64 u64_gte_mask(u64 a, u64 b)
{
        u64 x = a;
        u64 y = b;
        u64 x_xor_y = x ^ y;
        u64 x_sub_y = x - y;
        u64 x_sub_y_xor_y = x_sub_y ^ y;
        u64 q = x_xor_y | x_sub_y_xor_y;
        u64 x_xor_q = x ^ q;
        u64 x_xor_q_ = x_xor_q >> (u32)63U;
        u64 c = x_xor_q_ - (u64)1U;
        return c;
}

static __always_inline void modulo_carry_top(u64 *b)
{
        u64 b4 = b[4];
        u64 b0 = b[0];
        u64 b4_ = b4 & 0x7ffffffffffffLLU;
        u64 b0_ = b0 + 19 * (b4 >> 51);
        b[4] = b4_;
        b[0] = b0_;
}

static __always_inline void fproduct_copy_from_wide_(u64 *output, u128 *input)
{
        {
                u128 xi = input[0];
                output[0] = ((u64)(xi));
        }
        {
                u128 xi = input[1];
                output[1] = ((u64)(xi));
        }
        {
                u128 xi = input[2];
                output[2] = ((u64)(xi));
        }
        {
                u128 xi = input[3];
                output[3] = ((u64)(xi));
        }
        {
                u128 xi = input[4];
                output[4] = ((u64)(xi));
        }
}

static __always_inline void
fproduct_sum_scalar_multiplication_(u128 *output, u64 *input, u64 s)
{
        output[0] += (u128)input[0] * s;
        output[1] += (u128)input[1] * s;
        output[2] += (u128)input[2] * s;
        output[3] += (u128)input[3] * s;
        output[4] += (u128)input[4] * s;
}

static __always_inline void fproduct_carry_wide_(u128 *tmp)
{
        {
                u32 ctr = 0;
                u128 tctr = tmp[ctr];
                u128 tctrp1 = tmp[ctr + 1];
                u64 r0 = ((u64)(tctr)) & 0x7ffffffffffffLLU;
                u128 c = ((tctr) >> (51));
                tmp[ctr] = ((u128)(r0));
                tmp[ctr + 1] = ((tctrp1) + (c));
        }
        {
                u32 ctr = 1;
                u128 tctr = tmp[ctr];
                u128 tctrp1 = tmp[ctr + 1];
                u64 r0 = ((u64)(tctr)) & 0x7ffffffffffffLLU;
                u128 c = ((tctr) >> (51));
                tmp[ctr] = ((u128)(r0));
                tmp[ctr + 1] = ((tctrp1) + (c));
        }

        {
                u32 ctr = 2;
                u128 tctr = tmp[ctr];
                u128 tctrp1 = tmp[ctr + 1];
                u64 r0 = ((u64)(tctr)) & 0x7ffffffffffffLLU;
                u128 c = ((tctr) >> (51));
                tmp[ctr] = ((u128)(r0));
                tmp[ctr + 1] = ((tctrp1) + (c));
        }
        {
                u32 ctr = 3;
                u128 tctr = tmp[ctr];
                u128 tctrp1 = tmp[ctr + 1];
                u64 r0 = ((u64)(tctr)) & 0x7ffffffffffffLLU;
                u128 c = ((tctr) >> (51));
                tmp[ctr] = ((u128)(r0));
                tmp[ctr + 1] = ((tctrp1) + (c));
        }
}

static __always_inline void fmul_shift_reduce(u64 *output)
{
        u64 tmp = output[4];
        u64 b0;
        {
                u32 ctr = 5 - 0 - 1;
                u64 z = output[ctr - 1];
                output[ctr] = z;
        }
        {
                u32 ctr = 5 - 1 - 1;
                u64 z = output[ctr - 1];
                output[ctr] = z;
        }
        {
                u32 ctr = 5 - 2 - 1;
                u64 z = output[ctr - 1];
                output[ctr] = z;
        }
        {
                u32 ctr = 5 - 3 - 1;
                u64 z = output[ctr - 1];
                output[ctr] = z;
        }
        output[0] = tmp;
        b0 = output[0];
        output[0] = 19 * b0;
}

static __always_inline void fmul_mul_shift_reduce_(u128 *output, u64 *input,
                                                   u64 *input21)
{
        u32 i;
        u64 input2i;
        {
                u64 input2i = input21[0];
                fproduct_sum_scalar_multiplication_(output, input, input2i);
                fmul_shift_reduce(input);
        }
        {
                u64 input2i = input21[1];
                fproduct_sum_scalar_multiplication_(output, input, input2i);
                fmul_shift_reduce(input);
        }
        {
                u64 input2i = input21[2];
                fproduct_sum_scalar_multiplication_(output, input, input2i);
                fmul_shift_reduce(input);
        }
        {
                u64 input2i = input21[3];
                fproduct_sum_scalar_multiplication_(output, input, input2i);
                fmul_shift_reduce(input);
        }
        i = 4;
        input2i = input21[i];
        fproduct_sum_scalar_multiplication_(output, input, input2i);
}

static __always_inline void fmul_fmul(u64 *output, u64 *input, u64 *input21)
{
        u64 tmp[5] = { input[0], input[1], input[2], input[3], input[4] };
        {
                u128 b4;
                u128 b0;
                u128 b4_;
                u128 b0_;
                u64 i0;
                u64 i1;
                u64 i0_;
                u64 i1_;
                u128 t[5] = { 0 };
                fmul_mul_shift_reduce_(t, tmp, input21);
                fproduct_carry_wide_(t);
                b4 = t[4];
                b0 = t[0];
                b4_ = ((b4) & (((u128)(0x7ffffffffffffLLU))));
                b0_ = ((b0) + (((u128)(19) * (((u64)(((b4) >> (51))))))));
                t[4] = b4_;
                t[0] = b0_;
                fproduct_copy_from_wide_(output, t);
                i0 = output[0];
                i1 = output[1];
                i0_ = i0 & 0x7ffffffffffffLLU;
                i1_ = i1 + (i0 >> 51);
                output[0] = i0_;
                output[1] = i1_;
        }
}

static __always_inline void fsquare_fsquare__(u128 *tmp, u64 *output)
{
        u64 r0 = output[0];
        u64 r1 = output[1];
        u64 r2 = output[2];
        u64 r3 = output[3];
        u64 r4 = output[4];
        u64 d0 = r0 * 2;
        u64 d1 = r1 * 2;
        u64 d2 = r2 * 2 * 19;
        u64 d419 = r4 * 19;
        u64 d4 = d419 * 2;
        u128 s0 = ((((((u128)(r0) * (r0))) + (((u128)(d4) * (r1))))) +
                   (((u128)(d2) * (r3))));
        u128 s1 = ((((((u128)(d0) * (r1))) + (((u128)(d4) * (r2))))) +
                   (((u128)(r3 * 19) * (r3))));
        u128 s2 = ((((((u128)(d0) * (r2))) + (((u128)(r1) * (r1))))) +
                   (((u128)(d4) * (r3))));
        u128 s3 = ((((((u128)(d0) * (r3))) + (((u128)(d1) * (r2))))) +
                   (((u128)(r4) * (d419))));
        u128 s4 = ((((((u128)(d0) * (r4))) + (((u128)(d1) * (r3))))) +
                   (((u128)(r2) * (r2))));
        tmp[0] = s0;
        tmp[1] = s1;
        tmp[2] = s2;
        tmp[3] = s3;
        tmp[4] = s4;
}

static __always_inline void fsquare_fsquare_(u128 *tmp, u64 *output)
{
        u128 b4;
        u128 b0;
        u128 b4_;
        u128 b0_;
        u64 i0;
        u64 i1;
        u64 i0_;
        u64 i1_;
        fsquare_fsquare__(tmp, output);
        fproduct_carry_wide_(tmp);
        b4 = tmp[4];
        b0 = tmp[0];
        b4_ = ((b4) & (((u128)(0x7ffffffffffffLLU))));
        b0_ = ((b0) + (((u128)(19) * (((u64)(((b4) >> (51))))))));
        tmp[4] = b4_;
        tmp[0] = b0_;
        fproduct_copy_from_wide_(output, tmp);
        i0 = output[0];
        i1 = output[1];
        i0_ = i0 & 0x7ffffffffffffLLU;
        i1_ = i1 + (i0 >> 51);
        output[0] = i0_;
        output[1] = i1_;
}

static __always_inline void fsquare_fsquare_times_(u64 *output, u128 *tmp,
                                                   u32 count1)
{
        u32 i;
        fsquare_fsquare_(tmp, output);
        for (i = 1; i < count1; ++i)
                fsquare_fsquare_(tmp, output);
}

static __always_inline void fsquare_fsquare_times(u64 *output, u64 *input,
                                                  u32 count1)
{
        u128 t[5];
        memcpy(output, input, 5 * sizeof(*input));
        fsquare_fsquare_times_(output, t, count1);
}

static __always_inline void fsquare_fsquare_times_inplace(u64 *output,
                                                          u32 count1)
{
        u128 t[5];
        fsquare_fsquare_times_(output, t, count1);
}

static __always_inline void crecip_crecip(u64 *out, u64 *z)
{
        u64 buf[20] = { 0 };
        u64 *a0 = buf;
        u64 *t00 = buf + 5;
        u64 *b0 = buf + 10;
        u64 *t01;
        u64 *b1;
        u64 *c0;
        u64 *a;
        u64 *t0;
        u64 *b;
        u64 *c;
        fsquare_fsquare_times(a0, z, 1);
        fsquare_fsquare_times(t00, a0, 2);
        fmul_fmul(b0, t00, z);
        fmul_fmul(a0, b0, a0);
        fsquare_fsquare_times(t00, a0, 1);
        fmul_fmul(b0, t00, b0);
        fsquare_fsquare_times(t00, b0, 5);
        t01 = buf + 5;
        b1 = buf + 10;
        c0 = buf + 15;
        fmul_fmul(b1, t01, b1);
        fsquare_fsquare_times(t01, b1, 10);
        fmul_fmul(c0, t01, b1);
        fsquare_fsquare_times(t01, c0, 20);
        fmul_fmul(t01, t01, c0);
        fsquare_fsquare_times_inplace(t01, 10);
        fmul_fmul(b1, t01, b1);
        fsquare_fsquare_times(t01, b1, 50);
        a = buf;
        t0 = buf + 5;
        b = buf + 10;
        c = buf + 15;
        fmul_fmul(c, t0, b);
        fsquare_fsquare_times(t0, c, 100);
        fmul_fmul(t0, t0, c);
        fsquare_fsquare_times_inplace(t0, 50);
        fmul_fmul(t0, t0, b);
        fsquare_fsquare_times_inplace(t0, 5);
        fmul_fmul(out, t0, a);
}

static __always_inline void fsum(u64 *a, u64 *b)
{
        a[0] += b[0];
        a[1] += b[1];
        a[2] += b[2];
        a[3] += b[3];
        a[4] += b[4];
}

static __always_inline void fdifference(u64 *a, u64 *b)
{
        u64 tmp[5] = { 0 };
        u64 b0;
        u64 b1;
        u64 b2;
        u64 b3;
        u64 b4;
        memcpy(tmp, b, 5 * sizeof(*b));
        b0 = tmp[0];
        b1 = tmp[1];
        b2 = tmp[2];
        b3 = tmp[3];
        b4 = tmp[4];
        tmp[0] = b0 + 0x3fffffffffff68LLU;
        tmp[1] = b1 + 0x3ffffffffffff8LLU;
        tmp[2] = b2 + 0x3ffffffffffff8LLU;
        tmp[3] = b3 + 0x3ffffffffffff8LLU;
        tmp[4] = b4 + 0x3ffffffffffff8LLU;
        {
                u64 xi = a[0];
                u64 yi = tmp[0];
                a[0] = yi - xi;
        }
        {
                u64 xi = a[1];
                u64 yi = tmp[1];
                a[1] = yi - xi;
        }
        {
                u64 xi = a[2];
                u64 yi = tmp[2];
                a[2] = yi - xi;
        }
        {
                u64 xi = a[3];
                u64 yi = tmp[3];
                a[3] = yi - xi;
        }
        {
                u64 xi = a[4];
                u64 yi = tmp[4];
                a[4] = yi - xi;
        }
}

static __always_inline void fscalar(u64 *output, u64 *b, u64 s)
{
        u128 tmp[5];
        u128 b4;
        u128 b0;
        u128 b4_;
        u128 b0_;
        {
                u64 xi = b[0];
                tmp[0] = ((u128)(xi) * (s));
        }
        {
                u64 xi = b[1];
                tmp[1] = ((u128)(xi) * (s));
        }
        {
                u64 xi = b[2];
                tmp[2] = ((u128)(xi) * (s));
        }
        {
                u64 xi = b[3];
                tmp[3] = ((u128)(xi) * (s));
        }
        {
                u64 xi = b[4];
                tmp[4] = ((u128)(xi) * (s));
        }
        fproduct_carry_wide_(tmp);
        b4 = tmp[4];
        b0 = tmp[0];
        b4_ = ((b4) & (((u128)(0x7ffffffffffffLLU))));
        b0_ = ((b0) + (((u128)(19) * (((u64)(((b4) >> (51))))))));
        tmp[4] = b4_;
        tmp[0] = b0_;
        fproduct_copy_from_wide_(output, tmp);
}

static __always_inline void fmul(u64 *output, u64 *a, u64 *b)
{
        fmul_fmul(output, a, b);
}

static __always_inline void crecip(u64 *output, u64 *input)
{
        crecip_crecip(output, input);
}

static __always_inline void point_swap_conditional_step(u64 *a, u64 *b,
                                                        u64 swap1, u32 ctr)
{
        u32 i = ctr - 1;
        u64 ai = a[i];
        u64 bi = b[i];
        u64 x = swap1 & (ai ^ bi);
        u64 ai1 = ai ^ x;
        u64 bi1 = bi ^ x;
        a[i] = ai1;
        b[i] = bi1;
}

static __always_inline void point_swap_conditional5(u64 *a, u64 *b, u64 swap1)
{
        point_swap_conditional_step(a, b, swap1, 5);
        point_swap_conditional_step(a, b, swap1, 4);
        point_swap_conditional_step(a, b, swap1, 3);
        point_swap_conditional_step(a, b, swap1, 2);
        point_swap_conditional_step(a, b, swap1, 1);
}

static __always_inline void point_swap_conditional(u64 *a, u64 *b, u64 iswap)
{
        u64 swap1 = 0 - iswap;
        point_swap_conditional5(a, b, swap1);
        point_swap_conditional5(a + 5, b + 5, swap1);
}

static __always_inline void point_copy(u64 *output, u64 *input)
{
        memcpy(output, input, 5 * sizeof(*input));
        memcpy(output + 5, input + 5, 5 * sizeof(*input));
}

static __always_inline void addanddouble_fmonty(u64 *pp, u64 *ppq, u64 *p,
                                                u64 *pq, u64 *qmqp)
{
        u64 *qx = qmqp;
        u64 *x2 = pp;
        u64 *z2 = pp + 5;
        u64 *x3 = ppq;
        u64 *z3 = ppq + 5;
        u64 *x = p;
        u64 *z = p + 5;
        u64 *xprime = pq;
        u64 *zprime = pq + 5;
        u64 buf[40] = { 0 };
        u64 *origx = buf;
        u64 *origxprime0 = buf + 5;
        u64 *xxprime0;
        u64 *zzprime0;
        u64 *origxprime;
        xxprime0 = buf + 25;
        zzprime0 = buf + 30;
        memcpy(origx, x, 5 * sizeof(*x));
        fsum(x, z);
        fdifference(z, origx);
        memcpy(origxprime0, xprime, 5 * sizeof(*xprime));
        fsum(xprime, zprime);
        fdifference(zprime, origxprime0);
        fmul(xxprime0, xprime, z);
        fmul(zzprime0, x, zprime);
        origxprime = buf + 5;
        {
                u64 *xx0;
                u64 *zz0;
                u64 *xxprime;
                u64 *zzprime;
                u64 *zzzprime;
                xx0 = buf + 15;
                zz0 = buf + 20;
                xxprime = buf + 25;
                zzprime = buf + 30;
                zzzprime = buf + 35;
                memcpy(origxprime, xxprime, 5 * sizeof(*xxprime));
                fsum(xxprime, zzprime);
                fdifference(zzprime, origxprime);
                fsquare_fsquare_times(x3, xxprime, 1);
                fsquare_fsquare_times(zzzprime, zzprime, 1);
                fmul(z3, zzzprime, qx);
                fsquare_fsquare_times(xx0, x, 1);
                fsquare_fsquare_times(zz0, z, 1);
                {
                        u64 *zzz;
                        u64 *xx;
                        u64 *zz;
                        u64 scalar;
                        zzz = buf + 10;
                        xx = buf + 15;
                        zz = buf + 20;
                        fmul(x2, xx, zz);
                        fdifference(zz, xx);
                        scalar = 121665;
                        fscalar(zzz, zz, scalar);
                        fsum(zzz, xx);
                        fmul(z2, zzz, zz);
                }
        }
}

static __always_inline void
ladder_smallloop_cmult_small_loop_step(u64 *nq, u64 *nqpq, u64 *nq2, u64 *nqpq2,
                                       u64 *q, u8 byt)
{
        u64 bit0 = (u64)(byt >> 7);
        u64 bit;
        point_swap_conditional(nq, nqpq, bit0);
        addanddouble_fmonty(nq2, nqpq2, nq, nqpq, q);
        bit = (u64)(byt >> 7);
        point_swap_conditional(nq2, nqpq2, bit);
}

static __always_inline void
ladder_smallloop_cmult_small_loop_double_step(u64 *nq, u64 *nqpq, u64 *nq2,
                                              u64 *nqpq2, u64 *q, u8 byt)
{
        u8 byt1;
        ladder_smallloop_cmult_small_loop_step(nq, nqpq, nq2, nqpq2, q, byt);
        byt1 = byt << 1;
        ladder_smallloop_cmult_small_loop_step(nq2, nqpq2, nq, nqpq, q, byt1);
}

static __always_inline void
ladder_smallloop_cmult_small_loop(u64 *nq, u64 *nqpq, u64 *nq2, u64 *nqpq2,
                                  u64 *q, u8 byt, u32 i)
{
        while (i--) {
                ladder_smallloop_cmult_small_loop_double_step(nq, nqpq, nq2,
                                                              nqpq2, q, byt);
                byt <<= 2;
        }
}

static __always_inline void ladder_bigloop_cmult_big_loop(u8 *n1, u64 *nq,
                                                          u64 *nqpq, u64 *nq2,
                                                          u64 *nqpq2, u64 *q,
                                                          u32 i)
{
        while (i--) {
                u8 byte = n1[i];
                ladder_smallloop_cmult_small_loop(nq, nqpq, nq2, nqpq2, q,
                                                  byte, 4);
        }
}

static void ladder_cmult(u64 *result, u8 *n1, u64 *q)
{
        u64 point_buf[40] = { 0 };
        u64 *nq = point_buf;
        u64 *nqpq = point_buf + 10;
        u64 *nq2 = point_buf + 20;
        u64 *nqpq2 = point_buf + 30;
        point_copy(nqpq, q);
        nq[0] = 1;
        ladder_bigloop_cmult_big_loop(n1, nq, nqpq, nq2, nqpq2, q, 32);
        point_copy(result, nq);
}

static __always_inline void format_fexpand(u64 *output, const u8 *input)
{
        const u8 *x00 = input + 6;
        const u8 *x01 = input + 12;
        const u8 *x02 = input + 19;
        const u8 *x0 = input + 24;
        u64 i0, i1, i2, i3, i4, output0, output1, output2, output3, output4;
        i0 = get_unaligned_le64(input);
        i1 = get_unaligned_le64(x00);
        i2 = get_unaligned_le64(x01);
        i3 = get_unaligned_le64(x02);
        i4 = get_unaligned_le64(x0);
        output0 = i0 & 0x7ffffffffffffLLU;
        output1 = i1 >> 3 & 0x7ffffffffffffLLU;
        output2 = i2 >> 6 & 0x7ffffffffffffLLU;
        output3 = i3 >> 1 & 0x7ffffffffffffLLU;
        output4 = i4 >> 12 & 0x7ffffffffffffLLU;
        output[0] = output0;
        output[1] = output1;
        output[2] = output2;
        output[3] = output3;
        output[4] = output4;
}

static __always_inline void format_fcontract_first_carry_pass(u64 *input)
{
        u64 t0 = input[0];
        u64 t1 = input[1];
        u64 t2 = input[2];
        u64 t3 = input[3];
        u64 t4 = input[4];
        u64 t1_ = t1 + (t0 >> 51);
        u64 t0_ = t0 & 0x7ffffffffffffLLU;
        u64 t2_ = t2 + (t1_ >> 51);
        u64 t1__ = t1_ & 0x7ffffffffffffLLU;
        u64 t3_ = t3 + (t2_ >> 51);
        u64 t2__ = t2_ & 0x7ffffffffffffLLU;
        u64 t4_ = t4 + (t3_ >> 51);
        u64 t3__ = t3_ & 0x7ffffffffffffLLU;
        input[0] = t0_;
        input[1] = t1__;
        input[2] = t2__;
        input[3] = t3__;
        input[4] = t4_;
}

static __always_inline void format_fcontract_first_carry_full(u64 *input)
{
        format_fcontract_first_carry_pass(input);
        modulo_carry_top(input);
}

static __always_inline void format_fcontract_second_carry_pass(u64 *input)
{
        u64 t0 = input[0];
        u64 t1 = input[1];
        u64 t2 = input[2];
        u64 t3 = input[3];
        u64 t4 = input[4];
        u64 t1_ = t1 + (t0 >> 51);
        u64 t0_ = t0 & 0x7ffffffffffffLLU;
        u64 t2_ = t2 + (t1_ >> 51);
        u64 t1__ = t1_ & 0x7ffffffffffffLLU;
        u64 t3_ = t3 + (t2_ >> 51);
        u64 t2__ = t2_ & 0x7ffffffffffffLLU;
        u64 t4_ = t4 + (t3_ >> 51);
        u64 t3__ = t3_ & 0x7ffffffffffffLLU;
        input[0] = t0_;
        input[1] = t1__;
        input[2] = t2__;
        input[3] = t3__;
        input[4] = t4_;
}

static __always_inline void format_fcontract_second_carry_full(u64 *input)
{
        u64 i0;
        u64 i1;
        u64 i0_;
        u64 i1_;
        format_fcontract_second_carry_pass(input);
        modulo_carry_top(input);
        i0 = input[0];
        i1 = input[1];
        i0_ = i0 & 0x7ffffffffffffLLU;
        i1_ = i1 + (i0 >> 51);
        input[0] = i0_;
        input[1] = i1_;
}

static __always_inline void format_fcontract_trim(u64 *input)
{
        u64 a0 = input[0];
        u64 a1 = input[1];
        u64 a2 = input[2];
        u64 a3 = input[3];
        u64 a4 = input[4];
        u64 mask0 = u64_gte_mask(a0, 0x7ffffffffffedLLU);
        u64 mask1 = u64_eq_mask(a1, 0x7ffffffffffffLLU);
        u64 mask2 = u64_eq_mask(a2, 0x7ffffffffffffLLU);
        u64 mask3 = u64_eq_mask(a3, 0x7ffffffffffffLLU);
        u64 mask4 = u64_eq_mask(a4, 0x7ffffffffffffLLU);
        u64 mask = (((mask0 & mask1) & mask2) & mask3) & mask4;
        u64 a0_ = a0 - (0x7ffffffffffedLLU & mask);
        u64 a1_ = a1 - (0x7ffffffffffffLLU & mask);
        u64 a2_ = a2 - (0x7ffffffffffffLLU & mask);
        u64 a3_ = a3 - (0x7ffffffffffffLLU & mask);
        u64 a4_ = a4 - (0x7ffffffffffffLLU & mask);
        input[0] = a0_;
        input[1] = a1_;
        input[2] = a2_;
        input[3] = a3_;
        input[4] = a4_;
}

static __always_inline void format_fcontract_store(u8 *output, u64 *input)
{
        u64 t0 = input[0];
        u64 t1 = input[1];
        u64 t2 = input[2];
        u64 t3 = input[3];
        u64 t4 = input[4];
        u64 o0 = t1 << 51 | t0;
        u64 o1 = t2 << 38 | t1 >> 13;
        u64 o2 = t3 << 25 | t2 >> 26;
        u64 o3 = t4 << 12 | t3 >> 39;
        u8 *b0 = output;
        u8 *b1 = output + 8;
        u8 *b2 = output + 16;
        u8 *b3 = output + 24;
        put_unaligned_le64(o0, b0);
        put_unaligned_le64(o1, b1);
        put_unaligned_le64(o2, b2);
        put_unaligned_le64(o3, b3);
}

static __always_inline void format_fcontract(u8 *output, u64 *input)
{
        format_fcontract_first_carry_full(input);
        format_fcontract_second_carry_full(input);
        format_fcontract_trim(input);
        format_fcontract_store(output, input);
}

static __always_inline void format_scalar_of_point(u8 *scalar, u64 *point)
{
        u64 *x = point;
        u64 *z = point + 5;
        u64 buf[10] __aligned(32) = { 0 };
        u64 *zmone = buf;
        u64 *sc = buf + 5;
        crecip(zmone, z);
        fmul(sc, x, zmone);
        format_fcontract(scalar, sc);
}

void curve25519_generic(u8 mypublic[CURVE25519_KEY_SIZE],
                        const u8 secret[CURVE25519_KEY_SIZE],
                        const u8 basepoint[CURVE25519_KEY_SIZE])
{
        u64 buf0[10] __aligned(32) = { 0 };
        u64 *x0 = buf0;
        u64 *z = buf0 + 5;
        u64 *q;
        format_fexpand(x0, basepoint);
        z[0] = 1;
        q = buf0;
        {
                u8 e[32] __aligned(32) = { 0 };
                u8 *scalar;
                memcpy(e, secret, 32);
                curve25519_clamp_secret(e);
                scalar = e;
                {
                        u64 buf[15] = { 0 };
                        u64 *nq = buf;
                        u64 *x = nq;
                        x[0] = 1;
                        ladder_cmult(nq, scalar, q);
                        format_scalar_of_point(mypublic, nq);
                        memzero_explicit(buf, sizeof(buf));
                }
                memzero_explicit(e, sizeof(e));
        }
        memzero_explicit(buf0, sizeof(buf0));
}