linux/arch/x86/crypto/curve25519-x86_64.c

// SPDX-License-Identifier: GPL-2.0 OR MIT
/*
 * Copyright (C) 2020 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
 * Copyright (c) 2016-2020 INRIA, CMU and Microsoft Corporation
 */

#include <crypto/curve25519.h>
#include <crypto/internal/kpp.h>

#include <linux/types.h>
#include <linux/jump_label.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/scatterlist.h>

#include <asm/cpufeature.h>
#include <asm/processor.h>

static __always_inline 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;
	return xnx - (u64)1U;
}

static __always_inline 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;
	return x_xor_q_ - (u64)1U;
}

/* Computes the addition of four-element f1 with value in f2
 * and returns the carry (if any) */
static inline u64 add_scalar(u64 *out, const u64 *f1, u64 f2)
{
	u64 carry_r;

	asm volatile(
		/* Clear registers to propagate the carry bit */
		"  xor %%r8d, %%r8d;"
		"  xor %%r9d, %%r9d;"
		"  xor %%r10d, %%r10d;"
		"  xor %%r11d, %%r11d;"
		"  xor %k1, %k1;"

		/* Begin addition chain */
		"  addq 0(%3), %0;"
		"  movq %0, 0(%2);"
		"  adcxq 8(%3), %%r8;"
		"  movq %%r8, 8(%2);"
		"  adcxq 16(%3), %%r9;"
		"  movq %%r9, 16(%2);"
		"  adcxq 24(%3), %%r10;"
		"  movq %%r10, 24(%2);"

		/* Return the carry bit in a register */
		"  adcx %%r11, %1;"
		: "+&r"(f2), "=&r"(carry_r)
		: "r"(out), "r"(f1)
		: "%r8", "%r9", "%r10", "%r11", "memory", "cc");

	return carry_r;
}

/* Computes the field addition of two field elements */
static inline void fadd(u64 *out, const u64 *f1, const u64 *f2)
{
	asm volatile(
		/* Compute the raw addition of f1 + f2 */
		"  movq 0(%0), %%r8;"
		"  addq 0(%2), %%r8;"
		"  movq 8(%0), %%r9;"
		"  adcxq 8(%2), %%r9;"
		"  movq 16(%0), %%r10;"
		"  adcxq 16(%2), %%r10;"
		"  movq 24(%0), %%r11;"
		"  adcxq 24(%2), %%r11;"

		/* Wrap the result back into the field */

		/* Step 1: Compute carry*38 */
		"  mov $0, %%rax;"
		"  mov $38, %0;"
		"  cmovc %0, %%rax;"

		/* Step 2: Add carry*38 to the original sum */
		"  xor %%ecx, %%ecx;"
		"  add %%rax, %%r8;"
		"  adcx %%rcx, %%r9;"
		"  movq %%r9, 8(%1);"
		"  adcx %%rcx, %%r10;"
		"  movq %%r10, 16(%1);"
		"  adcx %%rcx, %%r11;"
		"  movq %%r11, 24(%1);"

		/* Step 3: Fold the carry bit back in; guaranteed not to carry at this point */
		"  mov $0, %%rax;"
		"  cmovc %0, %%rax;"
		"  add %%rax, %%r8;"
		"  movq %%r8, 0(%1);"
		: "+&r"(f2)
		: "r"(out), "r"(f1)
		: "%rax", "%rcx", "%r8", "%r9", "%r10", "%r11", "memory", "cc");
}

/* Computes the field subtraction of two field elements */
static inline void fsub(u64 *out, const u64 *f1, const u64 *f2)
{
	asm volatile(
		/* Compute the raw subtraction of f1-f2 */
		"  movq 0(%1), %%r8;"
		"  subq 0(%2), %%r8;"
		"  movq 8(%1), %%r9;"
		"  sbbq 8(%2), %%r9;"
		"  movq 16(%1), %%r10;"
		"  sbbq 16(%2), %%r10;"
		"  movq 24(%1), %%r11;"
		"  sbbq 24(%2), %%r11;"

		/* Wrap the result back into the field */

		/* Step 1: Compute carry*38 */
		"  mov $0, %%rax;"
		"  mov $38, %%rcx;"
		"  cmovc %%rcx, %%rax;"

		/* Step 2: Subtract carry*38 from the original difference */
		"  sub %%rax, %%r8;"
		"  sbb $0, %%r9;"
		"  sbb $0, %%r10;"
		"  sbb $0, %%r11;"

		/* Step 3: Fold the carry bit back in; guaranteed not to carry at this point */
		"  mov $0, %%rax;"
		"  cmovc %%rcx, %%rax;"
		"  sub %%rax, %%r8;"

		/* Store the result */
		"  movq %%r8, 0(%0);"
		"  movq %%r9, 8(%0);"
		"  movq %%r10, 16(%0);"
		"  movq %%r11, 24(%0);"
		:
		: "r"(out), "r"(f1), "r"(f2)
		: "%rax", "%rcx", "%r8", "%r9", "%r10", "%r11", "memory", "cc");
}

/* Computes a field multiplication: out <- f1 * f2
 * Uses the 8-element buffer tmp for intermediate results */
static inline void fmul(u64 *out, const u64 *f1, const u64 *f2, u64 *tmp)
{
	asm volatile(

		/* Compute the raw multiplication: tmp <- src1 * src2 */

		/* Compute src1[0] * src2 */
		"  movq 0(%0), %%rdx;"
		"  mulxq 0(%1), %%r8, %%r9;"
		"  xor %%r10d, %%r10d;"
		"  movq %%r8, 0(%2);"
		"  mulxq 8(%1), %%r10, %%r11;"
		"  adox %%r9, %%r10;"
		"  movq %%r10, 8(%2);"
		"  mulxq 16(%1), %%rbx, %%r13;"
		"  adox %%r11, %%rbx;"
		"  mulxq 24(%1), %%r14, %%rdx;"
		"  adox %%r13, %%r14;"
		"  mov $0, %%rax;"
		"  adox %%rdx, %%rax;"

		/* Compute src1[1] * src2 */
		"  movq 8(%0), %%rdx;"
		"  mulxq 0(%1), %%r8, %%r9;"
		"  xor %%r10d, %%r10d;"
		"  adcxq 8(%2), %%r8;"
		"  movq %%r8, 8(%2);"
		"  mulxq 8(%1), %%r10, %%r11;"
		"  adox %%r9, %%r10;"
		"  adcx %%rbx, %%r10;"
		"  movq %%r10, 16(%2);"
		"  mulxq 16(%1), %%rbx, %%r13;"
		"  adox %%r11, %%rbx;"
		"  adcx %%r14, %%rbx;"
		"  mov $0, %%r8;"
		"  mulxq 24(%1), %%r14, %%rdx;"
		"  adox %%r13, %%r14;"
		"  adcx %%rax, %%r14;"
		"  mov $0, %%rax;"
		"  adox %%rdx, %%rax;"
		"  adcx %%r8, %%rax;"

		/* Compute src1[2] * src2 */
		"  movq 16(%0), %%rdx;"
		"  mulxq 0(%1), %%r8, %%r9;"
		"  xor %%r10d, %%r10d;"
		"  adcxq 16(%2), %%r8;"
		"  movq %%r8, 16(%2);"
		"  mulxq 8(%1), %%r10, %%r11;"
		"  adox %%r9, %%r10;"
		"  adcx %%rbx, %%r10;"
		"  movq %%r10, 24(%2);"
		"  mulxq 16(%1), %%rbx, %%r13;"
		"  adox %%r11, %%rbx;"
		"  adcx %%r14, %%rbx;"
		"  mov $0, %%r8;"
		"  mulxq 24(%1), %%r14, %%rdx;"
		"  adox %%r13, %%r14;"
		"  adcx %%rax, %%r14;"
		"  mov $0, %%rax;"
		"  adox %%rdx, %%rax;"
		"  adcx %%r8, %%rax;"

		/* Compute src1[3] * src2 */
		"  movq 24(%0), %%rdx;"
		"  mulxq 0(%1), %%r8, %%r9;"
		"  xor %%r10d, %%r10d;"
		"  adcxq 24(%2), %%r8;"
		"  movq %%r8, 24(%2);"
		"  mulxq 8(%1), %%r10, %%r11;"
		"  adox %%r9, %%r10;"
		"  adcx %%rbx, %%r10;"
		"  movq %%r10, 32(%2);"
		"  mulxq 16(%1), %%rbx, %%r13;"
		"  adox %%r11, %%rbx;"
		"  adcx %%r14, %%rbx;"
		"  movq %%rbx, 40(%2);"
		"  mov $0, %%r8;"
		"  mulxq 24(%1), %%r14, %%rdx;"
		"  adox %%r13, %%r14;"
		"  adcx %%rax, %%r14;"
		"  movq %%r14, 48(%2);"
		"  mov $0, %%rax;"
		"  adox %%rdx, %%rax;"
		"  adcx %%r8, %%rax;"
		"  movq %%rax, 56(%2);"

		/* Line up pointers */
		"  mov %2, %0;"
		"  mov %3, %2;"

		/* Wrap the result back into the field */

		/* Step 1: Compute dst + carry == tmp_hi * 38 + tmp_lo */
		"  mov $38, %%rdx;"
		"  mulxq 32(%0), %%r8, %%r13;"
		"  xor %k1, %k1;"
		"  adoxq 0(%0), %%r8;"
		"  mulxq 40(%0), %%r9, %%rbx;"
		"  adcx %%r13, %%r9;"
		"  adoxq 8(%0), %%r9;"
		"  mulxq 48(%0), %%r10, %%r13;"
		"  adcx %%rbx, %%r10;"
		"  adoxq 16(%0), %%r10;"
		"  mulxq 56(%0), %%r11, %%rax;"
		"  adcx %%r13, %%r11;"
		"  adoxq 24(%0), %%r11;"
		"  adcx %1, %%rax;"
		"  adox %1, %%rax;"
		"  imul %%rdx, %%rax;"

		/* Step 2: Fold the carry back into dst */
		"  add %%rax, %%r8;"
		"  adcx %1, %%r9;"
		"  movq %%r9, 8(%2);"
		"  adcx %1, %%r10;"
		"  movq %%r10, 16(%2);"
		"  adcx %1, %%r11;"
		"  movq %%r11, 24(%2);"

		/* Step 3: Fold the carry bit back in; guaranteed not to carry at this point */
		"  mov $0, %%rax;"
		"  cmovc %%rdx, %%rax;"
		"  add %%rax, %%r8;"
		"  movq %%r8, 0(%2);"
		: "+&r"(f1), "+&r"(f2), "+&r"(tmp)
		: "r"(out)
		: "%rax", "%rbx", "%rdx", "%r8", "%r9", "%r10", "%r11", "%r13",
		  "%r14", "memory", "cc");
}

/* Computes two field multiplications:
 *   out[0] <- f1[0] * f2[0]
 *   out[1] <- f1[1] * f2[1]
 * Uses the 16-element buffer tmp for intermediate results: */
static inline void fmul2(u64 *out, const u64 *f1, const u64 *f2, u64 *tmp)
{
	asm volatile(

		/* Compute the raw multiplication tmp[0] <- f1[0] * f2[0] */

		/* Compute src1[0] * src2 */
		"  movq 0(%0), %%rdx;"
		"  mulxq 0(%1), %%r8, %%r9;"
		"  xor %%r10d, %%r10d;"
		"  movq %%r8, 0(%2);"
		"  mulxq 8(%1), %%r10, %%r11;"
		"  adox %%r9, %%r10;"
		"  movq %%r10, 8(%2);"
		"  mulxq 16(%1), %%rbx, %%r13;"
		"  adox %%r11, %%rbx;"
		"  mulxq 24(%1), %%r14, %%rdx;"
		"  adox %%r13, %%r14;"
		"  mov $0, %%rax;"
		"  adox %%rdx, %%rax;"

		/* Compute src1[1] * src2 */
		"  movq 8(%0), %%rdx;"
		"  mulxq 0(%1), %%r8, %%r9;"
		"  xor %%r10d, %%r10d;"
		"  adcxq 8(%2), %%r8;"
		"  movq %%r8, 8(%2);"
		"  mulxq 8(%1), %%r10, %%r11;"
		"  adox %%r9, %%r10;"
		"  adcx %%rbx, %%r10;"
		"  movq %%r10, 16(%2);"
		"  mulxq 16(%1), %%rbx, %%r13;"
		"  adox %%r11, %%rbx;"
		"  adcx %%r14, %%rbx;"
		"  mov $0, %%r8;"
		"  mulxq 24(%1), %%r14, %%rdx;"
		"  adox %%r13, %%r14;"
		"  adcx %%rax, %%r14;"
		"  mov $0, %%rax;"
		"  adox %%rdx, %%rax;"
		"  adcx %%r8, %%rax;"

		/* Compute src1[2] * src2 */
		"  movq 16(%0), %%rdx;"
		"  mulxq 0(%1), %%r8, %%r9;"
		"  xor %%r10d, %%r10d;"
		"  adcxq 16(%2), %%r8;"
		"  movq %%r8, 16(%2);"
		"  mulxq 8(%1), %%r10, %%r11;"
		"  adox %%r9, %%r10;"
		"  adcx %%rbx, %%r10;"
		"  movq %%r10, 24(%2);"
		"  mulxq 16(%1), %%rbx, %%r13;"
		"  adox %%r11, %%rbx;"
		"  adcx %%r14, %%rbx;"
		"  mov $0, %%r8;"
		"  mulxq 24(%1), %%r14, %%rdx;"
		"  adox %%r13, %%r14;"
		"  adcx %%rax, %%r14;"
		"  mov $0, %%rax;"
		"  adox %%rdx, %%rax;"
		"  adcx %%r8, %%rax;"

		/* Compute src1[3] * src2 */
		"  movq 24(%0), %%rdx;"
		"  mulxq 0(%1), %%r8, %%r9;"
		"  xor %%r10d, %%r10d;"
		"  adcxq 24(%2), %%r8;"
		"  movq %%r8, 24(%2);"
		"  mulxq 8(%1), %%r10, %%r11;"
		"  adox %%r9, %%r10;"
		"  adcx %%rbx, %%r10;"
		"  movq %%r10, 32(%2);"
		"  mulxq 16(%1), %%rbx, %%r13;"
		"  adox %%r11, %%rbx;"
		"  adcx %%r14, %%rbx;"
		"  movq %%rbx, 40(%2);"
		"  mov $0, %%r8;"
		"  mulxq 24(%1), %%r14, %%rdx;"
		"  adox %%r13, %%r14;"
		"  adcx %%rax, %%r14;"
		"  movq %%r14, 48(%2);"
		"  mov $0, %%rax;"
		"  adox %%rdx, %%rax;"
		"  adcx %%r8, %%rax;"
		"  movq %%rax, 56(%2);"

		/* Compute the raw multiplication tmp[1] <- f1[1] * f2[1] */

		/* Compute src1[0] * src2 */
		"  movq 32(%0), %%rdx;"
		"  mulxq 32(%1), %%r8, %%r9;"
		"  xor %%r10d, %%r10d;"
		"  movq %%r8, 64(%2);"
		"  mulxq 40(%1), %%r10, %%r11;"
		"  adox %%r9, %%r10;"
		"  movq %%r10, 72(%2);"
		"  mulxq 48(%1), %%rbx, %%r13;"
		"  adox %%r11, %%rbx;"
		"  mulxq 56(%1), %%r14, %%rdx;"
		"  adox %%r13, %%r14;"
		"  mov $0, %%rax;"
		"  adox %%rdx, %%rax;"

		/* Compute src1[1] * src2 */
		"  movq 40(%0), %%rdx;"
		"  mulxq 32(%1), %%r8, %%r9;"
		"  xor %%r10d, %%r10d;"
		"  adcxq 72(%2), %%r8;"
		"  movq %%r8, 72(%2);"
		"  mulxq 40(%1), %%r10, %%r11;"
		"  adox %%r9, %%r10;"
		"  adcx %%rbx, %%r10;"
		"  movq %%r10, 80(%2);"
		"  mulxq 48(%1), %%rbx, %%r13;"
		"  adox %%r11, %%rbx;"
		"  adcx %%r14, %%rbx;"
		"  mov $0, %%r8;"
		"  mulxq 56(%1), %%r14, %%rdx;"
		"  adox %%r13, %%r14;"
		"  adcx %%rax, %%r14;"
		"  mov $0, %%rax;"
		"  adox %%rdx, %%rax;"
		"  adcx %%r8, %%rax;"

		/* Compute src1[2] * src2 */
		"  movq 48(%0), %%rdx;"
		"  mulxq 32(%1), %%r8, %%r9;"
		"  xor %%r10d, %%r10d;"
		"  adcxq 80(%2), %%r8;"
		"  movq %%r8, 80(%2);"
		"  mulxq 40(%1), %%r10, %%r11;"
		"  adox %%r9, %%r10;"
		"  adcx %%rbx, %%r10;"
		"  movq %%r10, 88(%2);"
		"  mulxq 48(%1), %%rbx, %%r13;"
		"  adox %%r11, %%rbx;"
		"  adcx %%r14, %%rbx;"
		"  mov $0, %%r8;"
		"  mulxq 56(%1), %%r14, %%rdx;"
		"  adox %%r13, %%r14;"
		"  adcx %%rax, %%r14;"
		"  mov $0, %%rax;"
		"  adox %%rdx, %%rax;"
		"  adcx %%r8, %%rax;"

		/* Compute src1[3] * src2 */
		"  movq 56(%0), %%rdx;"
		"  mulxq 32(%1), %%r8, %%r9;"
		"  xor %%r10d, %%r10d;"
		"  adcxq 88(%2), %%r8;"
		"  movq %%r8, 88(%2);"
		"  mulxq 40(%1), %%r10, %%r11;"
		"  adox %%r9, %%r10;"
		"  adcx %%rbx, %%r10;"
		"  movq %%r10, 96(%2);"
		"  mulxq 48(%1), %%rbx, %%r13;"
		"  adox %%r11, %%rbx;"
		"  adcx %%r14, %%rbx;"
		"  movq %%rbx, 104(%2);"
		"  mov $0, %%r8;"
		"  mulxq 56(%1), %%r14, %%rdx;"
		"  adox %%r13, %%r14;"
		"  adcx %%rax, %%r14;"
		"  movq %%r14, 112(%2);"
		"  mov $0, %%rax;"
		"  adox %%rdx, %%rax;"
		"  adcx %%r8, %%rax;"
		"  movq %%rax, 120(%2);"

		/* Line up pointers */
		"  mov %2, %0;"
		"  mov %3, %2;"

		/* Wrap the results back into the field */

		/* Step 1: Compute dst + carry == tmp_hi * 38 + tmp_lo */
		"  mov $38, %%rdx;"
		"  mulxq 32(%0), %%r8, %%r13;"
		"  xor %k1, %k1;"
		"  adoxq 0(%0), %%r8;"
		"  mulxq 40(%0), %%r9, %%rbx;"
		"  adcx %%r13, %%r9;"
		"  adoxq 8(%0), %%r9;"
		"  mulxq 48(%0), %%r10, %%r13;"
		"  adcx %%rbx, %%r10;"
		"  adoxq 16(%0), %%r10;"
		"  mulxq 56(%0), %%r11, %%rax;"
		"  adcx %%r13, %%r11;"
		"  adoxq 24(%0), %%r11;"
		"  adcx %1, %%rax;"
		"  adox %1, %%rax;"
		"  imul %%rdx, %%rax;"

		/* Step 2: Fold the carry back into dst */
		"  add %%rax, %%r8;"
		"  adcx %1, %%r9;"
		"  movq %%r9, 8(%2);"
		"  adcx %1, %%r10;"
		"  movq %%r10, 16(%2);"
		"  adcx %1, %%r11;"
		"  movq %%r11, 24(%2);"

		/* Step 3: Fold the carry bit back in; guaranteed not to carry at this point */
		"  mov $0, %%rax;"
		"  cmovc %%rdx, %%rax;"
		"  add %%rax, %%r8;"
		"  movq %%r8, 0(%2);"

		/* Step 1: Compute dst + carry == tmp_hi * 38 + tmp_lo */
		"  mov $38, %%rdx;"
		"  mulxq 96(%0), %%r8, %%r13;"
		"  xor %k1, %k1;"
		"  adoxq 64(%0), %%r8;"
		"  mulxq 104(%0), %%r9, %%rbx;"
		"  adcx %%r13, %%r9;"
		"  adoxq 72(%0), %%r9;"
		"  mulxq 112(%0), %%r10, %%r13;"
		"  adcx %%rbx, %%r10;"
		"  adoxq 80(%0), %%r10;"
		"  mulxq 120(%0), %%r11, %%rax;"
		"  adcx %%r13, %%r11;"
		"  adoxq 88(%0), %%r11;"
		"  adcx %1, %%rax;"
		"  adox %1, %%rax;"
		"  imul %%rdx, %%rax;"

		/* Step 2: Fold the carry back into dst */
		"  add %%rax, %%r8;"
		"  adcx %1, %%r9;"
		"  movq %%r9, 40(%2);"
		"  adcx %1, %%r10;"
		"  movq %%r10, 48(%2);"
		"  adcx %1, %%r11;"
		"  movq %%r11, 56(%2);"

		/* Step 3: Fold the carry bit back in; guaranteed not to carry at this point */
		"  mov $0, %%rax;"
		"  cmovc %%rdx, %%rax;"
		"  add %%rax, %%r8;"
		"  movq %%r8, 32(%2);"
		: "+&r"(f1), "+&r"(f2), "+&r"(tmp)
		: "r"(out)
		: "%rax", "%rbx", "%rdx", "%r8", "%r9", "%r10", "%r11", "%r13",
		  "%r14", "memory", "cc");
}

/* Computes the field multiplication of four-element f1 with value in f2
 * Requires f2 to be smaller than 2^17 */
static inline void fmul_scalar(u64 *out, const u64 *f1, u64 f2)
{
	register u64 f2_r asm("rdx") = f2;

	asm volatile(
		/* Compute the raw multiplication of f1*f2 */
		"  mulxq 0(%2), %%r8, %%rcx;" /* f1[0]*f2 */
		"  mulxq 8(%2), %%r9, %%rbx;" /* f1[1]*f2 */
		"  add %%rcx, %%r9;"
		"  mov $0, %%rcx;"
		"  mulxq 16(%2), %%r10, %%r13;" /* f1[2]*f2 */
		"  adcx %%rbx, %%r10;"
		"  mulxq 24(%2), %%r11, %%rax;" /* f1[3]*f2 */
		"  adcx %%r13, %%r11;"
		"  adcx %%rcx, %%rax;"

		/* Wrap the result back into the field */

		/* Step 1: Compute carry*38 */
		"  mov $38, %%rdx;"
		"  imul %%rdx, %%rax;"

		/* Step 2: Fold the carry back into dst */
		"  add %%rax, %%r8;"
		"  adcx %%rcx, %%r9;"
		"  movq %%r9, 8(%1);"
		"  adcx %%rcx, %%r10;"
		"  movq %%r10, 16(%1);"
		"  adcx %%rcx, %%r11;"
		"  movq %%r11, 24(%1);"

		/* Step 3: Fold the carry bit back in; guaranteed not to carry at this point */
		"  mov $0, %%rax;"
		"  cmovc %%rdx, %%rax;"
		"  add %%rax, %%r8;"
		"  movq %%r8, 0(%1);"
		: "+&r"(f2_r)
		: "r"(out), "r"(f1)
		: "%rax", "%rbx", "%rcx", "%r8", "%r9", "%r10", "%r11", "%r13",
		  "memory", "cc");
}

/* Computes p1 <- bit ? p2 : p1 in constant time */
static inline void cswap2(u64 bit, const u64 *p1, const u64 *p2)
{
	asm volatile(
		/* Transfer bit into CF flag */
		"  add $18446744073709551615, %0;"

		/* cswap p1[0], p2[0] */
		"  movq 0(%1), %%r8;"
		"  movq 0(%2), %%r9;"
		"  mov %%r8, %%r10;"
		"  cmovc %%r9, %%r8;"
		"  cmovc %%r10, %%r9;"
		"  movq %%r8, 0(%1);"
		"  movq %%r9, 0(%2);"

		/* cswap p1[1], p2[1] */
		"  movq 8(%1), %%r8;"
		"  movq 8(%2), %%r9;"
		"  mov %%r8, %%r10;"
		"  cmovc %%r9, %%r8;"
		"  cmovc %%r10, %%r9;"
		"  movq %%r8, 8(%1);"
		"  movq %%r9, 8(%2);"

		/* cswap p1[2], p2[2] */
		"  movq 16(%1), %%r8;"
		"  movq 16(%2), %%r9;"
		"  mov %%r8, %%r10;"
		"  cmovc %%r9, %%r8;"
		"  cmovc %%r10, %%r9;"
		"  movq %%r8, 16(%1);"
		"  movq %%r9, 16(%2);"

		/* cswap p1[3], p2[3] */
		"  movq 24(%1), %%r8;"
		"  movq 24(%2), %%r9;"
		"  mov %%r8, %%r10;"
		"  cmovc %%r9, %%r8;"
		"  cmovc %%r10, %%r9;"
		"  movq %%r8, 24(%1);"
		"  movq %%r9, 24(%2);"

		/* cswap p1[4], p2[4] */
		"  movq 32(%1), %%r8;"
		"  movq 32(%2), %%r9;"
		"  mov %%r8, %%r10;"
		"  cmovc %%r9, %%r8;"
		"  cmovc %%r10, %%r9;"
		"  movq %%r8, 32(%1);"
		"  movq %%r9, 32(%2);"

		/* cswap p1[5], p2[5] */
		"  movq 40(%1), %%r8;"
		"  movq 40(%2), %%r9;"
		"  mov %%r8, %%r10;"
		"  cmovc %%r9, %%r8;"
		"  cmovc %%r10, %%r9;"
		"  movq %%r8, 40(%1);"
		"  movq %%r9, 40(%2);"

		/* cswap p1[6], p2[6] */
		"  movq 48(%1), %%r8;"
		"  movq 48(%2), %%r9;"
		"  mov %%r8, %%r10;"
		"  cmovc %%r9, %%r8;"
		"  cmovc %%r10, %%r9;"
		"  movq %%r8, 48(%1);"
		"  movq %%r9, 48(%2);"

		/* cswap p1[7], p2[7] */
		"  movq 56(%1), %%r8;"
		"  movq 56(%2), %%r9;"
		"  mov %%r8, %%r10;"
		"  cmovc %%r9, %%r8;"
		"  cmovc %%r10, %%r9;"
		"  movq %%r8, 56(%1);"
		"  movq %%r9, 56(%2);"
		: "+&r"(bit)
		: "r"(p1), "r"(p2)
		: "%r8", "%r9", "%r10", "memory", "cc");
}

/* Computes the square of a field element: out <- f * f
 * Uses the 8-element buffer tmp for intermediate results */
static inline void fsqr(u64 *out, const u64 *f, u64 *tmp)
{
	asm volatile(
		/* Compute the raw multiplication: tmp <- f * f */

		/* Step 1: Compute all partial products */
		"  movq 0(%0), %%rdx;" /* f[0] */
		"  mulxq 8(%0), %%r8, %%r14;"
		"  xor %%r15d, %%r15d;" /* f[1]*f[0] */
		"  mulxq 16(%0), %%r9, %%r10;"
		"  adcx %%r14, %%r9;" /* f[2]*f[0] */
		"  mulxq 24(%0), %%rax, %%rcx;"
		"  adcx %%rax, %%r10;" /* f[3]*f[0] */
		"  movq 24(%0), %%rdx;" /* f[3] */
		"  mulxq 8(%0), %%r11, %%rbx;"
		"  adcx %%rcx, %%r11;" /* f[1]*f[3] */
		"  mulxq 16(%0), %%rax, %%r13;"
		"  adcx %%rax, %%rbx;" /* f[2]*f[3] */
		"  movq 8(%0), %%rdx;"
		"  adcx %%r15, %%r13;" /* f1 */
		"  mulxq 16(%0), %%rax, %%rcx;"
		"  mov $0, %%r14;" /* f[2]*f[1] */

		/* Step 2: Compute two parallel carry chains */
		"  xor %%r15d, %%r15d;"
		"  adox %%rax, %%r10;"
		"  adcx %%r8, %%r8;"
		"  adox %%rcx, %%r11;"
		"  adcx %%r9, %%r9;"
		"  adox %%r15, %%rbx;"
		"  adcx %%r10, %%r10;"
		"  adox %%r15, %%r13;"
		"  adcx %%r11, %%r11;"
		"  adox %%r15, %%r14;"
		"  adcx %%rbx, %%rbx;"
		"  adcx %%r13, %%r13;"
		"  adcx %%r14, %%r14;"

		/* Step 3: Compute intermediate squares */
		"  movq 0(%0), %%rdx;"
		"  mulx %%rdx, %%rax, %%rcx;" /* f[0]^2 */
		"  movq %%rax, 0(%1);"
		"  add %%rcx, %%r8;"
		"  movq %%r8, 8(%1);"
		"  movq 8(%0), %%rdx;"
		"  mulx %%rdx, %%rax, %%rcx;" /* f[1]^2 */
		"  adcx %%rax, %%r9;"
		"  movq %%r9, 16(%1);"
		"  adcx %%rcx, %%r10;"
		"  movq %%r10, 24(%1);"
		"  movq 16(%0), %%rdx;"
		"  mulx %%rdx, %%rax, %%rcx;" /* f[2]^2 */
		"  adcx %%rax, %%r11;"
		"  movq %%r11, 32(%1);"
		"  adcx %%rcx, %%rbx;"
		"  movq %%rbx, 40(%1);"
		"  movq 24(%0), %%rdx;"
		"  mulx %%rdx, %%rax, %%rcx;" /* f[3]^2 */
		"  adcx %%rax, %%r13;"
		"  movq %%r13, 48(%1);"
		"  adcx %%rcx, %%r14;"
		"  movq %%r14, 56(%1);"

		/* Line up pointers */
		"  mov %1, %0;"
		"  mov %2, %1;"

		/* Wrap the result back into the field */

		/* Step 1: Compute dst + carry == tmp_hi * 38 + tmp_lo */
		"  mov $38, %%rdx;"
		"  mulxq 32(%0), %%r8, %%r13;"
		"  xor %%ecx, %%ecx;"
		"  adoxq 0(%0), %%r8;"
		"  mulxq 40(%0), %%r9, %%rbx;"
		"  adcx %%r13, %%r9;"
		"  adoxq 8(%0), %%r9;"
		"  mulxq 48(%0), %%r10, %%r13;"
		"  adcx %%rbx, %%r10;"
		"  adoxq 16(%0), %%r10;"
		"  mulxq 56(%0), %%r11, %%rax;"
		"  adcx %%r13, %%r11;"
		"  adoxq 24(%0), %%r11;"
		"  adcx %%rcx, %%rax;"
		"  adox %%rcx, %%rax;"
		"  imul %%rdx, %%rax;"

		/* Step 2: Fold the carry back into dst */
		"  add %%rax, %%r8;"
		"  adcx %%rcx, %%r9;"
		"  movq %%r9, 8(%1);"
		"  adcx %%rcx, %%r10;"
		"  movq %%r10, 16(%1);"
		"  adcx %%rcx, %%r11;"
		"  movq %%r11, 24(%1);"

		/* Step 3: Fold the carry bit back in; guaranteed not to carry at this point */
		"  mov $0, %%rax;"
		"  cmovc %%rdx, %%rax;"
		"  add %%rax, %%r8;"
		"  movq %%r8, 0(%1);"
		: "+&r"(f), "+&r"(tmp)
		: "r"(out)
		: "%rax", "%rbx", "%rcx", "%rdx", "%r8", "%r9", "%r10", "%r11",
		  "%r13", "%r14", "%r15", "memory", "cc");
}

/* Computes two field squarings:
 *   out[0] <- f[0] * f[0]
 *   out[1] <- f[1] * f[1]
 * Uses the 16-element buffer tmp for intermediate results */
static inline void fsqr2(u64 *out, const u64 *f, u64 *tmp)
{
	asm volatile(
		/* Step 1: Compute all partial products */
		"  movq 0(%0), %%rdx;" /* f[0] */
		"  mulxq 8(%0), %%r8, %%r14;"
		"  xor %%r15d, %%r15d;" /* f[1]*f[0] */
		"  mulxq 16(%0), %%r9, %%r10;"
		"  adcx %%r14, %%r9;" /* f[2]*f[0] */
		"  mulxq 24(%0), %%rax, %%rcx;"
		"  adcx %%rax, %%r10;" /* f[3]*f[0] */
		"  movq 24(%0), %%rdx;" /* f[3] */
		"  mulxq 8(%0), %%r11, %%rbx;"
		"  adcx %%rcx, %%r11;" /* f[1]*f[3] */
		"  mulxq 16(%0), %%rax, %%r13;"
		"  adcx %%rax, %%rbx;" /* f[2]*f[3] */
		"  movq 8(%0), %%rdx;"
		"  adcx %%r15, %%r13;" /* f1 */
		"  mulxq 16(%0), %%rax, %%rcx;"
		"  mov $0, %%r14;" /* f[2]*f[1] */

		/* Step 2: Compute two parallel carry chains */
		"  xor %%r15d, %%r15d;"
		"  adox %%rax, %%r10;"
		"  adcx %%r8, %%r8;"
		"  adox %%rcx, %%r11;"
		"  adcx %%r9, %%r9;"
		"  adox %%r15, %%rbx;"
		"  adcx %%r10, %%r10;"
		"  adox %%r15, %%r13;"
		"  adcx %%r11, %%r11;"
		"  adox %%r15, %%r14;"
		"  adcx %%rbx, %%rbx;"
		"  adcx %%r13, %%r13;"
		"  adcx %%r14, %%r14;"

		/* Step 3: Compute intermediate squares */
		"  movq 0(%0), %%rdx;"
		"  mulx %%rdx, %%rax, %%rcx;" /* f[0]^2 */
		"  movq %%rax, 0(%1);"
		"  add %%rcx, %%r8;"
		"  movq %%r8, 8(%1);"
		"  movq 8(%0), %%rdx;"
		"  mulx %%rdx, %%rax, %%rcx;" /* f[1]^2 */
		"  adcx %%rax, %%r9;"
		"  movq %%r9, 16(%1);"
		"  adcx %%rcx, %%r10;"
		"  movq %%r10, 24(%1);"
		"  movq 16(%0), %%rdx;"
		"  mulx %%rdx, %%rax, %%rcx;" /* f[2]^2 */
		"  adcx %%rax, %%r11;"
		"  movq %%r11, 32(%1);"
		"  adcx %%rcx, %%rbx;"
		"  movq %%rbx, 40(%1);"
		"  movq 24(%0), %%rdx;"
		"  mulx %%rdx, %%rax, %%rcx;" /* f[3]^2 */
		"  adcx %%rax, %%r13;"
		"  movq %%r13, 48(%1);"
		"  adcx %%rcx, %%r14;"
		"  movq %%r14, 56(%1);"

		/* Step 1: Compute all partial products */
		"  movq 32(%0), %%rdx;" /* f[0] */
		"  mulxq 40(%0), %%r8, %%r14;"
		"  xor %%r15d, %%r15d;" /* f[1]*f[0] */
		"  mulxq 48(%0), %%r9, %%r10;"
		"  adcx %%r14, %%r9;" /* f[2]*f[0] */
		"  mulxq 56(%0), %%rax, %%rcx;"
		"  adcx %%rax, %%r10;" /* f[3]*f[0] */
		"  movq 56(%0), %%rdx;" /* f[3] */
		"  mulxq 40(%0), %%r11, %%rbx;"
		"  adcx %%rcx, %%r11;" /* f[1]*f[3] */
		"  mulxq 48(%0), %%rax, %%r13;"
		"  adcx %%rax, %%rbx;" /* f[2]*f[3] */
		"  movq 40(%0), %%rdx;"
		"  adcx %%r15, %%r13;" /* f1 */
		"  mulxq 48(%0), %%rax, %%rcx;"
		"  mov $0, %%r14;" /* f[2]*f[1] */

		/* Step 2: Compute two parallel carry chains */
		"  xor %%r15d, %%r15d;"
		"  adox %%rax, %%r10;"
		"  adcx %%r8, %%r8;"
		"  adox %%rcx, %%r11;"
		"  adcx %%r9, %%r9;"
		"  adox %%r15, %%rbx;"
		"  adcx %%r10, %%r10;"
		"  adox %%r15, %%r13;"
		"  adcx %%r11, %%r11;"
		"  adox %%r15, %%r14;"
		"  adcx %%rbx, %%rbx;"
		"  adcx %%r13, %%r13;"
		"  adcx %%r14, %%r14;"

		/* Step 3: Compute intermediate squares */
		"  movq 32(%0), %%rdx;"
		"  mulx %%rdx, %%rax, %%rcx;" /* f[0]^2 */
		"  movq %%rax, 64(%1);"
		"  add %%rcx, %%r8;"
		"  movq %%r8, 72(%1);"
		"  movq 40(%0), %%rdx;"
		"  mulx %%rdx, %%rax, %%rcx;" /* f[1]^2 */
		"  adcx %%rax, %%r9;"
		"  movq %%r9, 80(%1);"
		"  adcx %%rcx, %%r10;"
		"  movq %%r10, 88(%1);"
		"  movq 48(%0), %%rdx;"
		"  mulx %%rdx, %%rax, %%rcx;" /* f[2]^2 */
		"  adcx %%rax, %%r11;"
		"  movq %%r11, 96(%1);"
		"  adcx %%rcx, %%rbx;"
		"  movq %%rbx, 104(%1);"
		"  movq 56(%0), %%rdx;"
		"  mulx %%rdx, %%rax, %%rcx;" /* f[3]^2 */
		"  adcx %%rax, %%r13;"
		"  movq %%r13, 112(%1);"
		"  adcx %%rcx, %%r14;"
		"  movq %%r14, 120(%1);"

		/* Line up pointers */
		"  mov %1, %0;"
		"  mov %2, %1;"

		/* Step 1: Compute dst + carry == tmp_hi * 38 + tmp_lo */
		"  mov $38, %%rdx;"
		"  mulxq 32(%0), %%r8, %%r13;"
		"  xor %%ecx, %%ecx;"
		"  adoxq 0(%0), %%r8;"
		"  mulxq 40(%0), %%r9, %%rbx;"
		"  adcx %%r13, %%r9;"
		"  adoxq 8(%0), %%r9;"
		"  mulxq 48(%0), %%r10, %%r13;"
		"  adcx %%rbx, %%r10;"
		"  adoxq 16(%0), %%r10;"
		"  mulxq 56(%0), %%r11, %%rax;"
		"  adcx %%r13, %%r11;"
		"  adoxq 24(%0), %%r11;"
		"  adcx %%rcx, %%rax;"
		"  adox %%rcx, %%rax;"
		"  imul %%rdx, %%rax;"

		/* Step 2: Fold the carry back into dst */
		"  add %%rax, %%r8;"
		"  adcx %%rcx, %%r9;"
		"  movq %%r9, 8(%1);"
		"  adcx %%rcx, %%r10;"
		"  movq %%r10, 16(%1);"
		"  adcx %%rcx, %%r11;"
		"  movq %%r11, 24(%1);"

		/* Step 3: Fold the carry bit back in; guaranteed not to carry at this point */
		"  mov $0, %%rax;"
		"  cmovc %%rdx, %%rax;"
		"  add %%rax, %%r8;"
		"  movq %%r8, 0(%1);"

		/* Step 1: Compute dst + carry == tmp_hi * 38 + tmp_lo */
		"  mov $38, %%rdx;"
		"  mulxq 96(%0), %%r8, %%r13;"
		"  xor %%ecx, %%ecx;"
		"  adoxq 64(%0), %%r8;"
		"  mulxq 104(%0), %%r9, %%rbx;"
		"  adcx %%r13, %%r9;"
		"  adoxq 72(%0), %%r9;"
		"  mulxq 112(%0), %%r10, %%r13;"
		"  adcx %%rbx, %%r10;"
		"  adoxq 80(%0), %%r10;"
		"  mulxq 120(%0), %%r11, %%rax;"
		"  adcx %%r13, %%r11;"
		"  adoxq 88(%0), %%r11;"
		"  adcx %%rcx, %%rax;"
		"  adox %%rcx, %%rax;"
		"  imul %%rdx, %%rax;"

		/* Step 2: Fold the carry back into dst */
		"  add %%rax, %%r8;"
		"  adcx %%rcx, %%r9;"
		"  movq %%r9, 40(%1);"
		"  adcx %%rcx, %%r10;"
		"  movq %%r10, 48(%1);"
		"  adcx %%rcx, %%r11;"
		"  movq %%r11, 56(%1);"

		/* Step 3: Fold the carry bit back in; guaranteed not to carry at this point */
		"  mov $0, %%rax;"
		"  cmovc %%rdx, %%rax;"
		"  add %%rax, %%r8;"
		"  movq %%r8, 32(%1);"
		: "+&r"(f), "+&r"(tmp)
		: "r"(out)
		: "%rax", "%rbx", "%rcx", "%rdx", "%r8", "%r9", "%r10", "%r11",
		  "%r13", "%r14", "%r15", "memory", "cc");
}

static void point_add_and_double(u64 *q, u64 *p01_tmp1, u64 *tmp2)
{
	u64 *nq = p01_tmp1;
	u64 *nq_p1 = p01_tmp1 + (u32)8U;
	u64 *tmp1 = p01_tmp1 + (u32)16U;
	u64 *x1 = q;
	u64 *x2 = nq;
	u64 *z2 = nq + (u32)4U;
	u64 *z3 = nq_p1 + (u32)4U;
	u64 *a = tmp1;
	u64 *b = tmp1 + (u32)4U;
	u64 *ab = tmp1;
	u64 *dc = tmp1 + (u32)8U;
	u64 *x3;
	u64 *z31;
	u64 *d0;
	u64 *c0;
	u64 *a1;
	u64 *b1;
	u64 *d;
	u64 *c;
	u64 *ab1;
	u64 *dc1;
	fadd(a, x2, z2);
	fsub(b, x2, z2);
	x3 = nq_p1;
	z31 = nq_p1 + (u32)4U;
	d0 = dc;
	c0 = dc + (u32)4U;
	fadd(c0, x3, z31);
	fsub(d0, x3, z31);
	fmul2(dc, dc, ab, tmp2);
	fadd(x3, d0, c0);
	fsub(z31, d0, c0);
	a1 = tmp1;
	b1 = tmp1 + (u32)4U;
	d = tmp1 + (u32)8U;
	c = tmp1 + (u32)12U;
	ab1 = tmp1;
	dc1 = tmp1 + (u32)8U;
	fsqr2(dc1, ab1, tmp2);
	fsqr2(nq_p1, nq_p1, tmp2);
	a1[0U] = c[0U];
	a1[1U] = c[1U];
	a1[2U] = c[2U];
	a1[3U] = c[3U];
	fsub(c, d, c);
	fmul_scalar(b1, c, (u64)121665U);
	fadd(b1, b1, d);
	fmul2(nq, dc1, ab1, tmp2);
	fmul(z3, z3, x1, tmp2);
}

static void point_double(u64 *nq, u64 *tmp1, u64 *tmp2)
{
	u64 *x2 = nq;
	u64 *z2 = nq + (u32)4U;
	u64 *a = tmp1;
	u64 *b = tmp1 + (u32)4U;
	u64 *d = tmp1 + (u32)8U;
	u64 *c = tmp1 + (u32)12U;
	u64 *ab = tmp1;
	u64 *dc = tmp1 + (u32)8U;
	fadd(a, x2, z2);
	fsub(b, x2, z2);
	fsqr2(dc, ab, tmp2);
	a[0U] = c[0U];
	a[1U] = c[1U];
	a[2U] = c[2U];
	a[3U] = c[3U];
	fsub(c, d, c);
	fmul_scalar(b, c, (u64)121665U);
	fadd(b, b, d);
	fmul2(nq, dc, ab, tmp2);
}

static void montgomery_ladder(u64 *out, const u8 *key, u64 *init1)
{
	u64 tmp2[16U] = { 0U };
	u64 p01_tmp1_swap[33U] = { 0U };
	u64 *p0 = p01_tmp1_swap;
	u64 *p01 = p01_tmp1_swap;
	u64 *p03 = p01;
	u64 *p11 = p01 + (u32)8U;
	u64 *x0;
	u64 *z0;
	u64 *p01_tmp1;
	u64 *p01_tmp11;
	u64 *nq10;
	u64 *nq_p11;
	u64 *swap1;
	u64 sw0;
	u64 *nq1;
	u64 *tmp1;
	memcpy(p11, init1, (u32)8U * sizeof(init1[0U]));
	x0 = p03;
	z0 = p03 + (u32)4U;
	x0[0U] = (u64)1U;
	x0[1U] = (u64)0U;
	x0[2U] = (u64)0U;
	x0[3U] = (u64)0U;
	z0[0U] = (u64)0U;
	z0[1U] = (u64)0U;
	z0[2U] = (u64)0U;
	z0[3U] = (u64)0U;
	p01_tmp1 = p01_tmp1_swap;
	p01_tmp11 = p01_tmp1_swap;
	nq10 = p01_tmp1_swap;
	nq_p11 = p01_tmp1_swap + (u32)8U;
	swap1 = p01_tmp1_swap + (u32)32U;
	cswap2((u64)1U, nq10, nq_p11);
	point_add_and_double(init1, p01_tmp11, tmp2);
	swap1[0U] = (u64)1U;
	{
		u32 i;
		for (i = (u32)0U; i < (u32)251U; i = i + (u32)1U) {
			u64 *p01_tmp12 = p01_tmp1_swap;
			u64 *swap2 = p01_tmp1_swap + (u32)32U;
			u64 *nq2 = p01_tmp12;
			u64 *nq_p12 = p01_tmp12 + (u32)8U;
			u64 bit = (u64)(key[((u32)253U - i) / (u32)8U] >> ((u32)253U - i) % (u32)8U & (u8)1U);
			u64 sw = swap2[0U] ^ bit;
			cswap2(sw, nq2, nq_p12);
			point_add_and_double(init1, p01_tmp12, tmp2);
			swap2[0U] = bit;
		}
	}
	sw0 = swap1[0U];
	cswap2(sw0, nq10, nq_p11);
	nq1 = p01_tmp1;
	tmp1 = p01_tmp1 + (u32)16U;
	point_double(nq1, tmp1, tmp2);
	point_double(nq1, tmp1, tmp2);
	point_double(nq1, tmp1, tmp2);
	memcpy(out, p0, (u32)8U * sizeof(p0[0U]));

	memzero_explicit(tmp2, sizeof(tmp2));
	memzero_explicit(p01_tmp1_swap, sizeof(p01_tmp1_swap));
}

static void fsquare_times(u64 *o, const u64 *inp, u64 *tmp, u32 n1)
{
	u32 i;
	fsqr(o, inp, tmp);
	for (i = (u32)0U; i < n1 - (u32)1U; i = i + (u32)1U)
		fsqr(o, o, tmp);
}

static void finv(u64 *o, const u64 *i, u64 *tmp)
{
	u64 t1[16U] = { 0U };
	u64 *a0 = t1;
	u64 *b = t1 + (u32)4U;
	u64 *c = t1 + (u32)8U;
	u64 *t00 = t1 + (u32)12U;
	u64 *tmp1 = tmp;
	u64 *a;
	u64 *t0;
	fsquare_times(a0, i, tmp1, (u32)1U);
	fsquare_times(t00, a0, tmp1, (u32)2U);
	fmul(b, t00, i, tmp);
	fmul(a0, b, a0, tmp);
	fsquare_times(t00, a0, tmp1, (u32)1U);
	fmul(b, t00, b, tmp);
	fsquare_times(t00, b, tmp1, (u32)5U);
	fmul(b, t00, b, tmp);
	fsquare_times(t00, b, tmp1, (u32)10U);
	fmul(c, t00, b, tmp);
	fsquare_times(t00, c, tmp1, (u32)20U);
	fmul(t00, t00, c, tmp);
	fsquare_times(t00, t00, tmp1, (u32)10U);
	fmul(b, t00, b, tmp);
	fsquare_times(t00, b, tmp1, (u32)50U);
	fmul(c, t00, b, tmp);
	fsquare_times(t00, c, tmp1, (u32)100U);
	fmul(t00, t00, c, tmp);
	fsquare_times(t00, t00, tmp1, (u32)50U);
	fmul(t00, t00, b, tmp);
	fsquare_times(t00, t00, tmp1, (u32)5U);
	a = t1;
	t0 = t1 + (u32)12U;
	fmul(o, t0, a, tmp);
}

static void store_felem(u64 *b, u64 *f)
{
	u64 f30 = f[3U];
	u64 top_bit0 = f30 >> (u32)63U;
	u64 f31;
	u64 top_bit;
	u64 f0;
	u64 f1;
	u64 f2;
	u64 f3;
	u64 m0;
	u64 m1;
	u64 m2;
	u64 m3;
	u64 mask;
	u64 f0_;
	u64 f1_;
	u64 f2_;
	u64 f3_;
	u64 o0;
	u64 o1;
	u64 o2;
	u64 o3;
	f[3U] = f30 & (u64)0x7fffffffffffffffU;
	add_scalar(f, f, (u64)19U * top_bit0);
	f31 = f[3U];
	top_bit = f31 >> (u32)63U;
	f[3U] = f31 & (u64)0x7fffffffffffffffU;
	add_scalar(f, f, (u64)19U * top_bit);
	f0 = f[0U];
	f1 = f[1U];
	f2 = f[2U];
	f3 = f[3U];
	m0 = gte_mask(f0, (u64)0xffffffffffffffedU);
	m1 = eq_mask(f1, (u64)0xffffffffffffffffU);
	m2 = eq_mask(f2, (u64)0xffffffffffffffffU);
	m3 = eq_mask(f3, (u64)0x7fffffffffffffffU);
	mask = ((m0 & m1) & m2) & m3;
	f0_ = f0 - (mask & (u64)0xffffffffffffffedU);
	f1_ = f1 - (mask & (u64)0xffffffffffffffffU);
	f2_ = f2 - (mask & (u64)0xffffffffffffffffU);
	f3_ = f3 - (mask & (u64)0x7fffffffffffffffU);
	o0 = f0_;
	o1 = f1_;
	o2 = f2_;
	o3 = f3_;
	b[0U] = o0;
	b[1U] = o1;
	b[2U] = o2;
	b[3U] = o3;
}

static void encode_point(u8 *o, const u64 *i)
{
	const u64 *x = i;
	const u64 *z = i + (u32)4U;
	u64 tmp[4U] = { 0U };
	u64 tmp_w[16U] = { 0U };
	finv(tmp, z, tmp_w);
	fmul(tmp, tmp, x, tmp_w);
	store_felem((u64 *)o, tmp);
}

static void curve25519_ever64(u8 *out, const u8 *priv, const u8 *pub)
{
	u64 init1[8U] = { 0U };
	u64 tmp[4U] = { 0U };
	u64 tmp3;
	u64 *x;
	u64 *z;
	{
		u32 i;
		for (i = (u32)0U; i < (u32)4U; i = i + (u32)1U) {
			u64 *os = tmp;
			const u8 *bj = pub + i * (u32)8U;
			u64 u = *(u64 *)bj;
			u64 r = u;
			u64 x0 = r;
			os[i] = x0;
		}
	}
	tmp3 = tmp[3U];
	tmp[3U] = tmp3 & (u64)0x7fffffffffffffffU;
	x = init1;
	z = init1 + (u32)4U;
	z[0U] = (u64)1U;
	z[1U] = (u64)0U;
	z[2U] = (u64)0U;
	z[3U] = (u64)0U;
	x[0U] = tmp[0U];
	x[1U] = tmp[1U];
	x[2U] = tmp[2U];
	x[3U] = tmp[3U];
	montgomery_ladder(init1, priv, init1);
	encode_point(out, init1);
}

/* The below constants were generated using this sage script:
 *
 * #!/usr/bin/env sage
 * import sys
 * from sage.all import *
 * def limbs(n):
 * 	n = int(n)
 * 	l = ((n >> 0) % 2^64, (n >> 64) % 2^64, (n >> 128) % 2^64, (n >> 192) % 2^64)
 * 	return "0x%016xULL, 0x%016xULL, 0x%016xULL, 0x%016xULL" % l
 * ec = EllipticCurve(GF(2^255 - 19), [0, 486662, 0, 1, 0])
 * p_minus_s = (ec.lift_x(9) - ec.lift_x(1))[0]
 * print("static const u64 p_minus_s[] = { %s };\n" % limbs(p_minus_s))
 * print("static const u64 table_ladder[] = {")
 * p = ec.lift_x(9)
 * for i in range(252):
 * 	l = (p[0] + p[2]) / (p[0] - p[2])
 * 	print(("\t%s" + ("," if i != 251 else "")) % limbs(l))
 * 	p = p * 2
 * print("};")
 *
 */

static const u64 p_minus_s[] = { 0x816b1e0137d48290ULL, 0x440f6a51eb4d1207ULL, 0x52385f46dca2b71dULL, 0x215132111d8354cbULL };

static const u64 table_ladder[] = {
	0xfffffffffffffff3ULL, 0xffffffffffffffffULL, 0xffffffffffffffffULL, 0x5fffffffffffffffULL,
	0x6b8220f416aafe96ULL, 0x82ebeb2b4f566a34ULL, 0xd5a9a5b075a5950fULL, 0x5142b2cf4b2488f4ULL,
	0x6aaebc750069680cULL, 0x89cf7820a0f99c41ULL, 0x2a58d9183b56d0f4ULL, 0x4b5aca80e36011a4ULL,
	0x329132348c29745dULL, 0xf4a2e616e1642fd7ULL, 0x1e45bb03ff67bc34ULL, 0x306912d0f42a9b4aULL,
	0xff886507e6af7154ULL, 0x04f50e13dfeec82fULL, 0xaa512fe82abab5ceULL, 0x174e251a68d5f222ULL,
	0xcf96700d82028898ULL, 0x1743e3370a2c02c5ULL, 0x379eec98b4e86eaaULL, 0x0c59888a51e0482eULL,
	0xfbcbf1d699b5d189ULL, 0xacaef0d58e9fdc84ULL, 0xc1c20d06231f7614ULL, 0x2938218da274f972ULL,
	0xf6af49beff1d7f18ULL, 0xcc541c22387ac9c2ULL, 0x96fcc9ef4015c56bULL, 0x69c1627c690913a9ULL,
	0x7a86fd2f4733db0eULL, 0xfdb8c4f29e087de9ULL, 0x095e4b1a8ea2a229ULL, 0x1ad7a7c829b37a79ULL,
	0x342d89cad17ea0c0ULL, 0x67bedda6cced2051ULL, 0x19ca31bf2bb42f74ULL, 0x3df7b4c84980acbbULL,
	0xa8c6444dc80ad883ULL, 0xb91e440366e3ab85ULL, 0xc215cda00164f6d8ULL, 0x3d867c6ef247e668ULL,
	0xc7dd582bcc3e658cULL, 0xfd2c4748ee0e5528ULL, 0xa0fd9b95cc9f4f71ULL, 0x7529d871b0675ddfULL,
	0xb8f568b42d3cbd78ULL, 0x1233011b91f3da82ULL, 0x2dce6ccd4a7c3b62ULL, 0x75e7fc8e9e498603ULL,
	0x2f4f13f1fcd0b6ecULL, 0xf1a8ca1f29ff7a45ULL, 0xc249c1a72981e29bULL, 0x6ebe0dbb8c83b56aULL,
	0x7114fa8d170bb222ULL, 0x65a2dcd5bf93935fULL, 0xbdc41f68b59c979aULL, 0x2f0eef79a2ce9289ULL,
	0x42ecbf0c083c37ceULL, 0x2930bc09ec496322ULL, 0xf294b0c19cfeac0dULL, 0x3780aa4bedfabb80ULL,
	0x56c17d3e7cead929ULL, 0xe7cb4beb2e5722c5ULL, 0x0ce931732dbfe15aULL, 0x41b883c7621052f8ULL,
	0xdbf75ca0c3d25350ULL, 0x2936be086eb1e351ULL, 0xc936e03cb4a9b212ULL, 0x1d45bf82322225aaULL,
	0xe81ab1036a024cc5ULL, 0xe212201c304c9a72ULL, 0xc5d73fba6832b1fcULL, 0x20ffdb5a4d839581ULL,
	0xa283d367be5d0fadULL, 0x6c2b25ca8b164475ULL, 0x9d4935467caaf22eULL, 0x5166408eee85ff49ULL,
	0x3c67baa2fab4e361ULL, 0xb3e433c67ef35cefULL, 0x5259729241159b1cULL, 0x6a621892d5b0ab33ULL,
	0x20b74a387555cdcbULL, 0x532aa10e1208923fULL, 0xeaa17b7762281dd1ULL, 0x61ab3443f05c44bfULL,
	0x257a6c422324def8ULL, 0x131c6c1017e3cf7fULL, 0x23758739f630a257ULL, 0x295a407a01a78580ULL,
	0xf8c443246d5da8d9ULL, 0x19d775450c52fa5dULL, 0x2afcfc92731bf83dULL, 0x7d10c8e81b2b4700ULL,
	0xc8e0271f70baa20bULL, 0x993748867ca63957ULL, 0x5412efb3cb7ed4bbULL, 0x3196d36173e62975ULL,
	0xde5bcad141c7dffcULL, 0x47cc8cd2b395c848ULL, 0xa34cd942e11af3cbULL, 0x0256dbf2d04ecec2ULL,
	0x875ab7e94b0e667fULL, 0xcad4dd83c0850d10ULL, 0x47f12e8f4e72c79fULL, 0x5f1a87bb8c85b19bULL,
	0x7ae9d0b6437f51b8ULL, 0x12c7ce5518879065ULL, 0x2ade09fe5cf77aeeULL, 0x23a05a2f7d2c5627ULL,
	0x5908e128f17c169aULL, 0xf77498dd8ad0852dULL, 0x74b4c4ceab102f64ULL, 0x183abadd10139845ULL,
	0xb165ba8daa92aaacULL, 0xd5c5ef9599386705ULL, 0xbe2f8f0cf8fc40d1ULL, 0x2701e635ee204514ULL,
	0x629fa80020156514ULL, 0xf223868764a8c1ceULL, 0x5b894fff0b3f060eULL, 0x60d9944cf708a3faULL,
	0xaeea001a1c7a201fULL, 0xebf16a633ee2ce63ULL, 0x6f7709594c7a07e1ULL, 0x79b958150d0208cbULL,
	0x24b55e5301d410e7ULL, 0xe3a34edff3fdc84dULL, 0xd88768e4904032d8ULL, 0x131384427b3aaeecULL,
	0x8405e51286234f14ULL, 0x14dc4739adb4c529ULL, 0xb8a2b5b250634ffdULL, 0x2fe2a94ad8a7ff93ULL,
	0xec5c57efe843faddULL, 0x2843ce40f0bb9918ULL, 0xa4b561d6cf3d6305ULL, 0x743629bde8fb777eULL,
	0x343edd46bbaf738fULL, 0xed981828b101a651ULL, 0xa401760b882c797aULL, 0x1fc223e28dc88730ULL,
	0x48604e91fc0fba0eULL, 0xb637f78f052c6fa4ULL, 0x91ccac3d09e9239cULL, 0x23f7eed4437a687cULL,
	0x5173b1118d9bd800ULL, 0x29d641b63189d4a7ULL, 0xfdbf177988bbc586ULL, 0x2959894fcad81df5ULL,
	0xaebc8ef3b4bbc899ULL, 0x4148995ab26992b9ULL, 0x24e20b0134f92cfbULL, 0x40d158894a05dee8ULL,
	0x46b00b1185af76f6ULL, 0x26bac77873187a79ULL, 0x3dc0bf95ab8fff5fULL, 0x2a608bd8945524d7ULL,
	0x26449588bd446302ULL, 0x7c4bc21c0388439cULL, 0x8e98a4f383bd11b2ULL, 0x26218d7bc9d876b9ULL,
	0xe3081542997c178aULL, 0x3c2d29a86fb6606fULL, 0x5c217736fa279374ULL, 0x7dde05734afeb1faULL,
	0x3bf10e3906d42babULL, 0xe4f7803e1980649cULL, 0xe6053bf89595bf7aULL, 0x394faf38da245530ULL,
	0x7a8efb58896928f4ULL, 0xfbc778e9cc6a113cULL, 0x72670ce330af596fULL, 0x48f222a81d3d6cf7ULL,
	0xf01fce410d72caa7ULL, 0x5a20ecc7213b5595ULL, 0x7bc21165c1fa1483ULL, 0x07f89ae31da8a741ULL,
	0x05d2c2b4c6830ff9ULL, 0xd43e330fc6316293ULL, 0xa5a5590a96d3a904ULL, 0x705edb91a65333b6ULL,
	0x048ee15e0bb9a5f7ULL, 0x3240cfca9e0aaf5dULL, 0x8f4b71ceedc4a40bULL, 0x621c0da3de544a6dULL,
	0x92872836a08c4091ULL, 0xce8375b010c91445ULL, 0x8a72eb524f276394ULL, 0x2667fcfa7ec83635ULL,
	0x7f4c173345e8752aULL, 0x061b47feee7079a5ULL, 0x25dd9afa9f86ff34ULL, 0x3780cef5425dc89cULL,
	0x1a46035a513bb4e9ULL, 0x3e1ef379ac575adaULL, 0xc78c5f1c5fa24b50ULL, 0x321a967634fd9f22ULL,
	0x946707b8826e27faULL, 0x3dca84d64c506fd0ULL, 0xc189218075e91436ULL, 0x6d9284169b3b8484ULL,
	0x3a67e840383f2ddfULL, 0x33eec9a30c4f9b75ULL, 0x3ec7c86fa783ef47ULL, 0x26ec449fbac9fbc4ULL,
	0x5c0f38cba09b9e7dULL, 0x81168cc762a3478cULL, 0x3e23b0d306fc121cULL, 0x5a238aa0a5efdcddULL,
	0x1ba26121c4ea43ffULL, 0x36f8c77f7c8832b5ULL, 0x88fbea0b0adcf99aULL, 0x5ca9938ec25bebf9ULL,
	0xd5436a5e51fccda0ULL, 0x1dbc4797c2cd893bULL, 0x19346a65d3224a08ULL, 0x0f5034e49b9af466ULL,
	0xf23c3967a1e0b96eULL, 0xe58b08fa867a4d88ULL, 0xfb2fabc6a7341679ULL, 0x2a75381eb6026946ULL,
	0xc80a3be4c19420acULL, 0x66b1f6c681f2b6dcULL, 0x7cf7036761e93388ULL, 0x25abbbd8a660a4c4ULL,
	0x91ea12ba14fd5198ULL, 0x684950fc4a3cffa9ULL, 0xf826842130f5ad28ULL, 0x3ea988f75301a441ULL,
	0xc978109a695f8c6fULL, 0x1746eb4a0530c3f3ULL, 0x444d6d77b4459995ULL, 0x75952b8c054e5cc7ULL,
	0xa3703f7915f4d6aaULL, 0x66c346202f2647d8ULL, 0xd01469df811d644bULL, 0x77fea47d81a5d71fULL,
	0xc5e9529ef57ca381ULL, 0x6eeeb4b9ce2f881aULL, 0xb6e91a28e8009bd6ULL, 0x4b80be3e9afc3fecULL,
	0x7e3773c526aed2c5ULL, 0x1b4afcb453c9a49dULL, 0xa920bdd7baffb24dULL, 0x7c54699f122d400eULL,
	0xef46c8e14fa94bc8ULL, 0xe0b074ce2952ed5eULL, 0xbea450e1dbd885d5ULL, 0x61b68649320f712cULL,
	0x8a485f7309ccbdd1ULL, 0xbd06320d7d4d1a2dULL, 0x25232973322dbef4ULL, 0x445dc4758c17f770ULL,
	0xdb0434177cc8933cULL, 0xed6fe82175ea059fULL, 0x1efebefdc053db34ULL, 0x4adbe867c65daf99ULL,
	0x3acd71a2a90609dfULL, 0xe5e991856dd04050ULL, 0x1ec69b688157c23cULL, 0x697427f6885cfe4dULL,
	0xd7be7b9b65e1a851ULL, 0xa03d28d522c536ddULL, 0x28399d658fd2b645ULL, 0x49e5b7e17c2641e1ULL,
	0x6f8c3a98700457a4ULL, 0x5078f0a25ebb6778ULL, 0xd13c3ccbc382960fULL, 0x2e003258a7df84b1ULL,
	0x8ad1f39be6296a1cULL, 0xc1eeaa652a5fbfb2ULL, 0x33ee0673fd26f3cbULL, 0x59256173a69d2cccULL,
	0x41ea07aa4e18fc41ULL, 0xd9fc19527c87a51eULL, 0xbdaacb805831ca6fULL, 0x445b652dc916694fULL,
	0xce92a3a7f2172315ULL, 0x1edc282de11b9964ULL, 0xa1823aafe04c314aULL, 0x790a2d94437cf586ULL,
	0x71c447fb93f6e009ULL, 0x8922a56722845276ULL, 0xbf70903b204f5169ULL, 0x2f7a89891ba319feULL,
	0x02a08eb577e2140cULL, 0xed9a4ed4427bdcf4ULL, 0x5253ec44e4323cd1ULL, 0x3e88363c14e9355bULL,
	0xaa66c14277110b8cULL, 0x1ae0391610a23390ULL, 0x2030bd12c93fc2a2ULL, 0x3ee141579555c7abULL,
	0x9214de3a6d6e7d41ULL, 0x3ccdd88607f17efeULL, 0x674f1288f8e11217ULL, 0x5682250f329f93d0ULL,
	0x6cf00b136d2e396eULL, 0x6e4cf86f1014debfULL, 0x5930b1b5bfcc4e83ULL, 0x047069b48aba16b6ULL,
	0x0d4ce4ab69b20793ULL, 0xb24db91a97d0fb9eULL, 0xcdfa50f54e00d01dULL, 0x221b1085368bddb5ULL,
	0xe7e59468b1e3d8d2ULL, 0x53c56563bd122f93ULL, 0xeee8a903e0663f09ULL, 0x61efa662cbbe3d42ULL,
	0x2cf8ddddde6eab2aULL, 0x9bf80ad51435f231ULL, 0x5deadacec9f04973ULL, 0x29275b5d41d29b27ULL,
	0xcfde0f0895ebf14fULL, 0xb9aab96b054905a7ULL, 0xcae80dd9a1c420fdULL, 0x0a63bf2f1673bbc7ULL,
	0x092f6e11958fbc8cULL, 0x672a81e804822fadULL, 0xcac8351560d52517ULL, 0x6f3f7722c8f192f8ULL,
	0xf8ba90ccc2e894b7ULL, 0x2c7557a438ff9f0dULL, 0x894d1d855ae52359ULL, 0x68e122157b743d69ULL,
	0xd87e5570cfb919f3ULL, 0x3f2cdecd95798db9ULL, 0x2121154710c0a2ceULL, 0x3c66a115246dc5b2ULL,
	0xcbedc562294ecb72ULL, 0xba7143c36a280b16ULL, 0x9610c2efd4078b67ULL, 0x6144735d946a4b1eULL,
	0x536f111ed75b3350ULL, 0x0211db8c2041d81bULL, 0xf93cb1000e10413cULL, 0x149dfd3c039e8876ULL,
	0xd479dde46b63155bULL, 0xb66e15e93c837976ULL, 0xdafde43b1f13e038ULL, 0x5fafda1a2e4b0b35ULL,
	0x3600bbdf17197581ULL, 0x3972050bbe3cd2c2ULL, 0x5938906dbdd5be86ULL, 0x34fce5e43f9b860fULL,
	0x75a8a4cd42d14d02ULL, 0x828dabc53441df65ULL, 0x33dcabedd2e131d3ULL, 0x3ebad76fb814d25fULL,
	0xd4906f566f70e10fULL, 0x5d12f7aa51690f5aULL, 0x45adb16e76cefcf2ULL, 0x01f768aead232999ULL,
	0x2b6cc77b6248febdULL, 0x3cd30628ec3aaffdULL, 0xce1c0b80d4ef486aULL, 0x4c3bff2ea6f66c23ULL,
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	0xfe06afe0c98c6ce4ULL, 0xc235df96dddfd6e4ULL, 0x1428d01e33bf1ed3ULL, 0x785768ec9300bdafULL,
	0x9702e57a91deb63bULL, 0x61bdb8bfe5ce8b80ULL, 0x645b426f3d1d58acULL, 0x4804a82227a557bcULL,
	0x8e57048ab44d2601ULL, 0x68d6501a4b3a6935ULL, 0xc39c9ec3f9e1c293ULL, 0x4172f257d4de63e2ULL,
	0xd368b450330c6401ULL, 0x040d3017418f2391ULL, 0x2c34bb6090b7d90dULL, 0x16f649228fdfd51fULL,
	0xbea6818e2b928ef5ULL, 0xe28ccf91cdc11e72ULL, 0x594aaa68e77a36cdULL, 0x313034806c7ffd0fULL,
	0x8a9d27ac2249bd65ULL, 0x19a3b464018e9512ULL, 0xc26ccff352b37ec7ULL, 0x056f68341d797b21ULL,
	0x5e79d6757efd2327ULL, 0xfabdbcb6553afe15ULL, 0xd3e7222c6eaf5a60ULL, 0x7046c76d4dae743bULL,
	0x660be872b18d4a55ULL, 0x19992518574e1496ULL, 0xc103053a302bdcbbULL, 0x3ed8e9800b218e8eULL,
	0x7b0b9239fa75e03eULL, 0xefe9fb684633c083ULL, 0x98a35fbe391a7793ULL, 0x6065510fe2d0fe34ULL,
	0x55cb668548abad0cULL, 0xb4584548da87e527ULL, 0x2c43ecea0107c1ddULL, 0x526028809372de35ULL,
	0x3415c56af9213b1fULL, 0x5bee1a4d017e98dbULL, 0x13f6b105b5cf709bULL, 0x5ff20e3482b29ab6ULL,
	0x0aa29c75cc2e6c90ULL, 0xfc7d73ca3a70e206ULL, 0x899fc38fc4b5c515ULL, 0x250386b124ffc207ULL,
	0x54ea28d5ae3d2b56ULL, 0x9913149dd6de60ceULL, 0x16694fc58f06d6c1ULL, 0x46b23975eb018fc7ULL,
	0x470a6a0fb4b7b4e2ULL, 0x5d92475a8f7253deULL, 0xabeee5b52fbd3adbULL, 0x7fa20801a0806968ULL,
	0x76f3faf19f7714d2ULL, 0xb3e840c12f4660c3ULL, 0x0fb4cd8df212744eULL, 0x4b065a251d3a2dd2ULL,
	0x5cebde383d77cd4aULL, 0x6adf39df882c9cb1ULL, 0xa2dd242eb09af759ULL, 0x3147c0e50e5f6422ULL,
	0x164ca5101d1350dbULL, 0xf8d13479c33fc962ULL, 0xe640ce4d13e5da08ULL, 0x4bdee0c45061f8baULL,
	0xd7c46dc1a4edb1c9ULL, 0x5514d7b6437fd98aULL, 0x58942f6bb2a1c00bULL, 0x2dffb2ab1d70710eULL,
	0xccdfcf2fc18b6d68ULL, 0xa8ebcba8b7806167ULL, 0x980697f95e2937e3ULL, 0x02fbba1cd0126e8cULL
};

static void curve25519_ever64_base(u8 *out, const u8 *priv)
{
	u64 swap = 1;
	int i, j, k;
	u64 tmp[16 + 32 + 4];
	u64 *x1 = &tmp[0];
	u64 *z1 = &tmp[4];
	u64 *x2 = &tmp[8];
	u64 *z2 = &tmp[12];
	u64 *xz1 = &tmp[0];
	u64 *xz2 = &tmp[8];
	u64 *a = &tmp[0 + 16];
	u64 *b = &tmp[4 + 16];
	u64 *c = &tmp[8 + 16];
	u64 *ab = &tmp[0 + 16];
	u64 *abcd = &tmp[0 + 16];
	u64 *ef = &tmp[16 + 16];
	u64 *efgh = &tmp[16 + 16];
	u64 *key = &tmp[0 + 16 + 32];

	memcpy(key, priv, 32);
	((u8 *)key)[0] &= 248;
	((u8 *)key)[31] = (((u8 *)key)[31] & 127) | 64;

	x1[0] = 1, x1[1] = x1[2] = x1[3] = 0;
	z1[0] = 1, z1[1] = z1[2] = z1[3] = 0;
	z2[0] = 1, z2[1] = z2[2] = z2[3] = 0;
	memcpy(x2, p_minus_s, sizeof(p_minus_s));

	j = 3;
	for (i = 0; i < 4; ++i) {
		while (j < (const int[]){ 64, 64, 64, 63 }[i]) {
			u64 bit = (key[i] >> j) & 1;
			k = (64 * i + j - 3);
			swap = swap ^ bit;
			cswap2(swap, xz1, xz2);
			swap = bit;
			fsub(b, x1, z1);
			fadd(a, x1, z1);
			fmul(c, &table_ladder[4 * k], b, ef);
			fsub(b, a, c);
			fadd(a, a, c);
			fsqr2(ab, ab, efgh);
			fmul2(xz1, xz2, ab, efgh);
			++j;
		}
		j = 0;
	}

	point_double(xz1, abcd, efgh);
	point_double(xz1, abcd, efgh);
	point_double(xz1, abcd, efgh);
	encode_point(out, xz1);

	memzero_explicit(tmp, sizeof(tmp));
}

static __ro_after_init DEFINE_STATIC_KEY_FALSE(curve25519_use_bmi2_adx);

void curve25519_arch(u8 mypublic[CURVE25519_KEY_SIZE],
		     const u8 secret[CURVE25519_KEY_SIZE],
		     const u8 basepoint[CURVE25519_KEY_SIZE])
{
	if (static_branch_likely(&curve25519_use_bmi2_adx))
		curve25519_ever64(mypublic, secret, basepoint);
	else
		curve25519_generic(mypublic, secret, basepoint);
}
EXPORT_SYMBOL(curve25519_arch);

void curve25519_base_arch(u8 pub[CURVE25519_KEY_SIZE],
			  const u8 secret[CURVE25519_KEY_SIZE])
{
	if (static_branch_likely(&curve25519_use_bmi2_adx))
		curve25519_ever64_base(pub, secret);
	else
		curve25519_generic(pub, secret, curve25519_base_point);
}
EXPORT_SYMBOL(curve25519_base_arch);

static int curve25519_set_secret(struct crypto_kpp *tfm, const void *buf,
				 unsigned int len)
{
	u8 *secret = kpp_tfm_ctx(tfm);

	if (!len)
		curve25519_generate_secret(secret);
	else if (len == CURVE25519_KEY_SIZE &&
		 crypto_memneq(buf, curve25519_null_point, CURVE25519_KEY_SIZE))
		memcpy(secret, buf, CURVE25519_KEY_SIZE);
	else
		return -EINVAL;
	return 0;
}

static int curve25519_generate_public_key(struct kpp_request *req)
{
	struct crypto_kpp *tfm = crypto_kpp_reqtfm(req);
	const u8 *secret = kpp_tfm_ctx(tfm);
	u8 buf[CURVE25519_KEY_SIZE];
	int copied, nbytes;

	if (req->src)
		return -EINVAL;

	curve25519_base_arch(buf, secret);

	/* might want less than we've got */
	nbytes = min_t(size_t, CURVE25519_KEY_SIZE, req->dst_len);
	copied = sg_copy_from_buffer(req->dst, sg_nents_for_len(req->dst,
								nbytes),
				     buf, nbytes);
	if (copied != nbytes)
		return -EINVAL;
	return 0;
}

static int curve25519_compute_shared_secret(struct kpp_request *req)
{
	struct crypto_kpp *tfm = crypto_kpp_reqtfm(req);
	const u8 *secret = kpp_tfm_ctx(tfm);
	u8 public_key[CURVE25519_KEY_SIZE];
	u8 buf[CURVE25519_KEY_SIZE];
	int copied, nbytes;

	if (!req->src)
		return -EINVAL;

	copied = sg_copy_to_buffer(req->src,
				   sg_nents_for_len(req->src,
						    CURVE25519_KEY_SIZE),
				   public_key, CURVE25519_KEY_SIZE);
	if (copied != CURVE25519_KEY_SIZE)
		return -EINVAL;

	curve25519_arch(buf, secret, public_key);

	/* might want less than we've got */
	nbytes = min_t(size_t, CURVE25519_KEY_SIZE, req->dst_len);
	copied = sg_copy_from_buffer(req->dst, sg_nents_for_len(req->dst,
								nbytes),
				     buf, nbytes);
	if (copied != nbytes)
		return -EINVAL;
	return 0;
}

static unsigned int curve25519_max_size(struct crypto_kpp *tfm)
{
	return CURVE25519_KEY_SIZE;
}

static struct kpp_alg curve25519_alg = {
	.base.cra_name		= "curve25519",
	.base.cra_driver_name	= "curve25519-x86",
	.base.cra_priority	= 200,
	.base.cra_module	= THIS_MODULE,
	.base.cra_ctxsize	= CURVE25519_KEY_SIZE,

	.set_secret		= curve25519_set_secret,
	.generate_public_key	= curve25519_generate_public_key,
	.compute_shared_secret	= curve25519_compute_shared_secret,
	.max_size		= curve25519_max_size,
};


static int __init curve25519_mod_init(void)
{
	if (boot_cpu_has(X86_FEATURE_BMI2) && boot_cpu_has(X86_FEATURE_ADX))
		static_branch_enable(&curve25519_use_bmi2_adx);
	else
		return 0;
	return IS_REACHABLE(CONFIG_CRYPTO_KPP) ?
		crypto_register_kpp(&curve25519_alg) : 0;
}

static void __exit curve25519_mod_exit(void)
{
	if (IS_REACHABLE(CONFIG_CRYPTO_KPP) &&
	    static_branch_likely(&curve25519_use_bmi2_adx))
		crypto_unregister_kpp(&curve25519_alg);
}

module_init(curve25519_mod_init);
module_exit(curve25519_mod_exit);

MODULE_ALIAS_CRYPTO("curve25519");
MODULE_ALIAS_CRYPTO("curve25519-x86");
MODULE_LICENSE("GPL v2");
MODULE_AUTHOR("Jason A. Donenfeld <Jason@zx2c4.com>");