1 // SPDX-License-Identifier: GPL-2.0 OR MIT
2 /*
3  * Copyright (C) 2016-2017 INRIA and Microsoft Corporation.
4  * Copyright (C) 2018-2019 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
5  *
6  * This is a machine-generated formally verified implementation of Curve25519
7  * ECDH from: <https://github.com/mitls/hacl-star>. Though originally machine
8  * generated, it has been tweaked to be suitable for use in the kernel. It is
9  * optimized for 64-bit machines that can efficiently work with 128-bit
10  * integer types.
11  */
12 
13 #include <asm/unaligned.h>
14 #include <crypto/curve25519.h>
15 #include <linux/string.h>
16 
17 typedef __uint128_t u128;
18 
19 static __always_inline u64 u64_eq_mask(u64 a, u64 b)
20 {
21 	u64 x = a ^ b;
22 	u64 minus_x = ~x + (u64)1U;
23 	u64 x_or_minus_x = x | minus_x;
24 	u64 xnx = x_or_minus_x >> (u32)63U;
25 	u64 c = xnx - (u64)1U;
26 	return c;
27 }
28 
29 static __always_inline u64 u64_gte_mask(u64 a, u64 b)
30 {
31 	u64 x = a;
32 	u64 y = b;
33 	u64 x_xor_y = x ^ y;
34 	u64 x_sub_y = x - y;
35 	u64 x_sub_y_xor_y = x_sub_y ^ y;
36 	u64 q = x_xor_y | x_sub_y_xor_y;
37 	u64 x_xor_q = x ^ q;
38 	u64 x_xor_q_ = x_xor_q >> (u32)63U;
39 	u64 c = x_xor_q_ - (u64)1U;
40 	return c;
41 }
42 
43 static __always_inline void modulo_carry_top(u64 *b)
44 {
45 	u64 b4 = b[4];
46 	u64 b0 = b[0];
47 	u64 b4_ = b4 & 0x7ffffffffffffLLU;
48 	u64 b0_ = b0 + 19 * (b4 >> 51);
49 	b[4] = b4_;
50 	b[0] = b0_;
51 }
52 
53 static __always_inline void fproduct_copy_from_wide_(u64 *output, u128 *input)
54 {
55 	{
56 		u128 xi = input[0];
57 		output[0] = ((u64)(xi));
58 	}
59 	{
60 		u128 xi = input[1];
61 		output[1] = ((u64)(xi));
62 	}
63 	{
64 		u128 xi = input[2];
65 		output[2] = ((u64)(xi));
66 	}
67 	{
68 		u128 xi = input[3];
69 		output[3] = ((u64)(xi));
70 	}
71 	{
72 		u128 xi = input[4];
73 		output[4] = ((u64)(xi));
74 	}
75 }
76 
77 static __always_inline void
78 fproduct_sum_scalar_multiplication_(u128 *output, u64 *input, u64 s)
79 {
80 	output[0] += (u128)input[0] * s;
81 	output[1] += (u128)input[1] * s;
82 	output[2] += (u128)input[2] * s;
83 	output[3] += (u128)input[3] * s;
84 	output[4] += (u128)input[4] * s;
85 }
86 
87 static __always_inline void fproduct_carry_wide_(u128 *tmp)
88 {
89 	{
90 		u32 ctr = 0;
91 		u128 tctr = tmp[ctr];
92 		u128 tctrp1 = tmp[ctr + 1];
93 		u64 r0 = ((u64)(tctr)) & 0x7ffffffffffffLLU;
94 		u128 c = ((tctr) >> (51));
95 		tmp[ctr] = ((u128)(r0));
96 		tmp[ctr + 1] = ((tctrp1) + (c));
97 	}
98 	{
99 		u32 ctr = 1;
100 		u128 tctr = tmp[ctr];
101 		u128 tctrp1 = tmp[ctr + 1];
102 		u64 r0 = ((u64)(tctr)) & 0x7ffffffffffffLLU;
103 		u128 c = ((tctr) >> (51));
104 		tmp[ctr] = ((u128)(r0));
105 		tmp[ctr + 1] = ((tctrp1) + (c));
106 	}
107 
108 	{
109 		u32 ctr = 2;
110 		u128 tctr = tmp[ctr];
111 		u128 tctrp1 = tmp[ctr + 1];
112 		u64 r0 = ((u64)(tctr)) & 0x7ffffffffffffLLU;
113 		u128 c = ((tctr) >> (51));
114 		tmp[ctr] = ((u128)(r0));
115 		tmp[ctr + 1] = ((tctrp1) + (c));
116 	}
117 	{
118 		u32 ctr = 3;
119 		u128 tctr = tmp[ctr];
120 		u128 tctrp1 = tmp[ctr + 1];
121 		u64 r0 = ((u64)(tctr)) & 0x7ffffffffffffLLU;
122 		u128 c = ((tctr) >> (51));
123 		tmp[ctr] = ((u128)(r0));
124 		tmp[ctr + 1] = ((tctrp1) + (c));
125 	}
126 }
127 
128 static __always_inline void fmul_shift_reduce(u64 *output)
129 {
130 	u64 tmp = output[4];
131 	u64 b0;
132 	{
133 		u32 ctr = 5 - 0 - 1;
134 		u64 z = output[ctr - 1];
135 		output[ctr] = z;
136 	}
137 	{
138 		u32 ctr = 5 - 1 - 1;
139 		u64 z = output[ctr - 1];
140 		output[ctr] = z;
141 	}
142 	{
143 		u32 ctr = 5 - 2 - 1;
144 		u64 z = output[ctr - 1];
145 		output[ctr] = z;
146 	}
147 	{
148 		u32 ctr = 5 - 3 - 1;
149 		u64 z = output[ctr - 1];
150 		output[ctr] = z;
151 	}
152 	output[0] = tmp;
153 	b0 = output[0];
154 	output[0] = 19 * b0;
155 }
156 
157 static __always_inline void fmul_mul_shift_reduce_(u128 *output, u64 *input,
158 						   u64 *input21)
159 {
160 	u32 i;
161 	u64 input2i;
162 	{
163 		u64 input2i = input21[0];
164 		fproduct_sum_scalar_multiplication_(output, input, input2i);
165 		fmul_shift_reduce(input);
166 	}
167 	{
168 		u64 input2i = input21[1];
169 		fproduct_sum_scalar_multiplication_(output, input, input2i);
170 		fmul_shift_reduce(input);
171 	}
172 	{
173 		u64 input2i = input21[2];
174 		fproduct_sum_scalar_multiplication_(output, input, input2i);
175 		fmul_shift_reduce(input);
176 	}
177 	{
178 		u64 input2i = input21[3];
179 		fproduct_sum_scalar_multiplication_(output, input, input2i);
180 		fmul_shift_reduce(input);
181 	}
182 	i = 4;
183 	input2i = input21[i];
184 	fproduct_sum_scalar_multiplication_(output, input, input2i);
185 }
186 
187 static __always_inline void fmul_fmul(u64 *output, u64 *input, u64 *input21)
188 {
189 	u64 tmp[5] = { input[0], input[1], input[2], input[3], input[4] };
190 	{
191 		u128 b4;
192 		u128 b0;
193 		u128 b4_;
194 		u128 b0_;
195 		u64 i0;
196 		u64 i1;
197 		u64 i0_;
198 		u64 i1_;
199 		u128 t[5] = { 0 };
200 		fmul_mul_shift_reduce_(t, tmp, input21);
201 		fproduct_carry_wide_(t);
202 		b4 = t[4];
203 		b0 = t[0];
204 		b4_ = ((b4) & (((u128)(0x7ffffffffffffLLU))));
205 		b0_ = ((b0) + (((u128)(19) * (((u64)(((b4) >> (51))))))));
206 		t[4] = b4_;
207 		t[0] = b0_;
208 		fproduct_copy_from_wide_(output, t);
209 		i0 = output[0];
210 		i1 = output[1];
211 		i0_ = i0 & 0x7ffffffffffffLLU;
212 		i1_ = i1 + (i0 >> 51);
213 		output[0] = i0_;
214 		output[1] = i1_;
215 	}
216 }
217 
218 static __always_inline void fsquare_fsquare__(u128 *tmp, u64 *output)
219 {
220 	u64 r0 = output[0];
221 	u64 r1 = output[1];
222 	u64 r2 = output[2];
223 	u64 r3 = output[3];
224 	u64 r4 = output[4];
225 	u64 d0 = r0 * 2;
226 	u64 d1 = r1 * 2;
227 	u64 d2 = r2 * 2 * 19;
228 	u64 d419 = r4 * 19;
229 	u64 d4 = d419 * 2;
230 	u128 s0 = ((((((u128)(r0) * (r0))) + (((u128)(d4) * (r1))))) +
231 		   (((u128)(d2) * (r3))));
232 	u128 s1 = ((((((u128)(d0) * (r1))) + (((u128)(d4) * (r2))))) +
233 		   (((u128)(r3 * 19) * (r3))));
234 	u128 s2 = ((((((u128)(d0) * (r2))) + (((u128)(r1) * (r1))))) +
235 		   (((u128)(d4) * (r3))));
236 	u128 s3 = ((((((u128)(d0) * (r3))) + (((u128)(d1) * (r2))))) +
237 		   (((u128)(r4) * (d419))));
238 	u128 s4 = ((((((u128)(d0) * (r4))) + (((u128)(d1) * (r3))))) +
239 		   (((u128)(r2) * (r2))));
240 	tmp[0] = s0;
241 	tmp[1] = s1;
242 	tmp[2] = s2;
243 	tmp[3] = s3;
244 	tmp[4] = s4;
245 }
246 
247 static __always_inline void fsquare_fsquare_(u128 *tmp, u64 *output)
248 {
249 	u128 b4;
250 	u128 b0;
251 	u128 b4_;
252 	u128 b0_;
253 	u64 i0;
254 	u64 i1;
255 	u64 i0_;
256 	u64 i1_;
257 	fsquare_fsquare__(tmp, output);
258 	fproduct_carry_wide_(tmp);
259 	b4 = tmp[4];
260 	b0 = tmp[0];
261 	b4_ = ((b4) & (((u128)(0x7ffffffffffffLLU))));
262 	b0_ = ((b0) + (((u128)(19) * (((u64)(((b4) >> (51))))))));
263 	tmp[4] = b4_;
264 	tmp[0] = b0_;
265 	fproduct_copy_from_wide_(output, tmp);
266 	i0 = output[0];
267 	i1 = output[1];
268 	i0_ = i0 & 0x7ffffffffffffLLU;
269 	i1_ = i1 + (i0 >> 51);
270 	output[0] = i0_;
271 	output[1] = i1_;
272 }
273 
274 static __always_inline void fsquare_fsquare_times_(u64 *output, u128 *tmp,
275 						   u32 count1)
276 {
277 	u32 i;
278 	fsquare_fsquare_(tmp, output);
279 	for (i = 1; i < count1; ++i)
280 		fsquare_fsquare_(tmp, output);
281 }
282 
283 static __always_inline void fsquare_fsquare_times(u64 *output, u64 *input,
284 						  u32 count1)
285 {
286 	u128 t[5];
287 	memcpy(output, input, 5 * sizeof(*input));
288 	fsquare_fsquare_times_(output, t, count1);
289 }
290 
291 static __always_inline void fsquare_fsquare_times_inplace(u64 *output,
292 							  u32 count1)
293 {
294 	u128 t[5];
295 	fsquare_fsquare_times_(output, t, count1);
296 }
297 
298 static __always_inline void crecip_crecip(u64 *out, u64 *z)
299 {
300 	u64 buf[20] = { 0 };
301 	u64 *a0 = buf;
302 	u64 *t00 = buf + 5;
303 	u64 *b0 = buf + 10;
304 	u64 *t01;
305 	u64 *b1;
306 	u64 *c0;
307 	u64 *a;
308 	u64 *t0;
309 	u64 *b;
310 	u64 *c;
311 	fsquare_fsquare_times(a0, z, 1);
312 	fsquare_fsquare_times(t00, a0, 2);
313 	fmul_fmul(b0, t00, z);
314 	fmul_fmul(a0, b0, a0);
315 	fsquare_fsquare_times(t00, a0, 1);
316 	fmul_fmul(b0, t00, b0);
317 	fsquare_fsquare_times(t00, b0, 5);
318 	t01 = buf + 5;
319 	b1 = buf + 10;
320 	c0 = buf + 15;
321 	fmul_fmul(b1, t01, b1);
322 	fsquare_fsquare_times(t01, b1, 10);
323 	fmul_fmul(c0, t01, b1);
324 	fsquare_fsquare_times(t01, c0, 20);
325 	fmul_fmul(t01, t01, c0);
326 	fsquare_fsquare_times_inplace(t01, 10);
327 	fmul_fmul(b1, t01, b1);
328 	fsquare_fsquare_times(t01, b1, 50);
329 	a = buf;
330 	t0 = buf + 5;
331 	b = buf + 10;
332 	c = buf + 15;
333 	fmul_fmul(c, t0, b);
334 	fsquare_fsquare_times(t0, c, 100);
335 	fmul_fmul(t0, t0, c);
336 	fsquare_fsquare_times_inplace(t0, 50);
337 	fmul_fmul(t0, t0, b);
338 	fsquare_fsquare_times_inplace(t0, 5);
339 	fmul_fmul(out, t0, a);
340 }
341 
342 static __always_inline void fsum(u64 *a, u64 *b)
343 {
344 	a[0] += b[0];
345 	a[1] += b[1];
346 	a[2] += b[2];
347 	a[3] += b[3];
348 	a[4] += b[4];
349 }
350 
351 static __always_inline void fdifference(u64 *a, u64 *b)
352 {
353 	u64 tmp[5] = { 0 };
354 	u64 b0;
355 	u64 b1;
356 	u64 b2;
357 	u64 b3;
358 	u64 b4;
359 	memcpy(tmp, b, 5 * sizeof(*b));
360 	b0 = tmp[0];
361 	b1 = tmp[1];
362 	b2 = tmp[2];
363 	b3 = tmp[3];
364 	b4 = tmp[4];
365 	tmp[0] = b0 + 0x3fffffffffff68LLU;
366 	tmp[1] = b1 + 0x3ffffffffffff8LLU;
367 	tmp[2] = b2 + 0x3ffffffffffff8LLU;
368 	tmp[3] = b3 + 0x3ffffffffffff8LLU;
369 	tmp[4] = b4 + 0x3ffffffffffff8LLU;
370 	{
371 		u64 xi = a[0];
372 		u64 yi = tmp[0];
373 		a[0] = yi - xi;
374 	}
375 	{
376 		u64 xi = a[1];
377 		u64 yi = tmp[1];
378 		a[1] = yi - xi;
379 	}
380 	{
381 		u64 xi = a[2];
382 		u64 yi = tmp[2];
383 		a[2] = yi - xi;
384 	}
385 	{
386 		u64 xi = a[3];
387 		u64 yi = tmp[3];
388 		a[3] = yi - xi;
389 	}
390 	{
391 		u64 xi = a[4];
392 		u64 yi = tmp[4];
393 		a[4] = yi - xi;
394 	}
395 }
396 
397 static __always_inline void fscalar(u64 *output, u64 *b, u64 s)
398 {
399 	u128 tmp[5];
400 	u128 b4;
401 	u128 b0;
402 	u128 b4_;
403 	u128 b0_;
404 	{
405 		u64 xi = b[0];
406 		tmp[0] = ((u128)(xi) * (s));
407 	}
408 	{
409 		u64 xi = b[1];
410 		tmp[1] = ((u128)(xi) * (s));
411 	}
412 	{
413 		u64 xi = b[2];
414 		tmp[2] = ((u128)(xi) * (s));
415 	}
416 	{
417 		u64 xi = b[3];
418 		tmp[3] = ((u128)(xi) * (s));
419 	}
420 	{
421 		u64 xi = b[4];
422 		tmp[4] = ((u128)(xi) * (s));
423 	}
424 	fproduct_carry_wide_(tmp);
425 	b4 = tmp[4];
426 	b0 = tmp[0];
427 	b4_ = ((b4) & (((u128)(0x7ffffffffffffLLU))));
428 	b0_ = ((b0) + (((u128)(19) * (((u64)(((b4) >> (51))))))));
429 	tmp[4] = b4_;
430 	tmp[0] = b0_;
431 	fproduct_copy_from_wide_(output, tmp);
432 }
433 
434 static __always_inline void fmul(u64 *output, u64 *a, u64 *b)
435 {
436 	fmul_fmul(output, a, b);
437 }
438 
439 static __always_inline void crecip(u64 *output, u64 *input)
440 {
441 	crecip_crecip(output, input);
442 }
443 
444 static __always_inline void point_swap_conditional_step(u64 *a, u64 *b,
445 							u64 swap1, u32 ctr)
446 {
447 	u32 i = ctr - 1;
448 	u64 ai = a[i];
449 	u64 bi = b[i];
450 	u64 x = swap1 & (ai ^ bi);
451 	u64 ai1 = ai ^ x;
452 	u64 bi1 = bi ^ x;
453 	a[i] = ai1;
454 	b[i] = bi1;
455 }
456 
457 static __always_inline void point_swap_conditional5(u64 *a, u64 *b, u64 swap1)
458 {
459 	point_swap_conditional_step(a, b, swap1, 5);
460 	point_swap_conditional_step(a, b, swap1, 4);
461 	point_swap_conditional_step(a, b, swap1, 3);
462 	point_swap_conditional_step(a, b, swap1, 2);
463 	point_swap_conditional_step(a, b, swap1, 1);
464 }
465 
466 static __always_inline void point_swap_conditional(u64 *a, u64 *b, u64 iswap)
467 {
468 	u64 swap1 = 0 - iswap;
469 	point_swap_conditional5(a, b, swap1);
470 	point_swap_conditional5(a + 5, b + 5, swap1);
471 }
472 
473 static __always_inline void point_copy(u64 *output, u64 *input)
474 {
475 	memcpy(output, input, 5 * sizeof(*input));
476 	memcpy(output + 5, input + 5, 5 * sizeof(*input));
477 }
478 
479 static __always_inline void addanddouble_fmonty(u64 *pp, u64 *ppq, u64 *p,
480 						u64 *pq, u64 *qmqp)
481 {
482 	u64 *qx = qmqp;
483 	u64 *x2 = pp;
484 	u64 *z2 = pp + 5;
485 	u64 *x3 = ppq;
486 	u64 *z3 = ppq + 5;
487 	u64 *x = p;
488 	u64 *z = p + 5;
489 	u64 *xprime = pq;
490 	u64 *zprime = pq + 5;
491 	u64 buf[40] = { 0 };
492 	u64 *origx = buf;
493 	u64 *origxprime0 = buf + 5;
494 	u64 *xxprime0;
495 	u64 *zzprime0;
496 	u64 *origxprime;
497 	xxprime0 = buf + 25;
498 	zzprime0 = buf + 30;
499 	memcpy(origx, x, 5 * sizeof(*x));
500 	fsum(x, z);
501 	fdifference(z, origx);
502 	memcpy(origxprime0, xprime, 5 * sizeof(*xprime));
503 	fsum(xprime, zprime);
504 	fdifference(zprime, origxprime0);
505 	fmul(xxprime0, xprime, z);
506 	fmul(zzprime0, x, zprime);
507 	origxprime = buf + 5;
508 	{
509 		u64 *xx0;
510 		u64 *zz0;
511 		u64 *xxprime;
512 		u64 *zzprime;
513 		u64 *zzzprime;
514 		xx0 = buf + 15;
515 		zz0 = buf + 20;
516 		xxprime = buf + 25;
517 		zzprime = buf + 30;
518 		zzzprime = buf + 35;
519 		memcpy(origxprime, xxprime, 5 * sizeof(*xxprime));
520 		fsum(xxprime, zzprime);
521 		fdifference(zzprime, origxprime);
522 		fsquare_fsquare_times(x3, xxprime, 1);
523 		fsquare_fsquare_times(zzzprime, zzprime, 1);
524 		fmul(z3, zzzprime, qx);
525 		fsquare_fsquare_times(xx0, x, 1);
526 		fsquare_fsquare_times(zz0, z, 1);
527 		{
528 			u64 *zzz;
529 			u64 *xx;
530 			u64 *zz;
531 			u64 scalar;
532 			zzz = buf + 10;
533 			xx = buf + 15;
534 			zz = buf + 20;
535 			fmul(x2, xx, zz);
536 			fdifference(zz, xx);
537 			scalar = 121665;
538 			fscalar(zzz, zz, scalar);
539 			fsum(zzz, xx);
540 			fmul(z2, zzz, zz);
541 		}
542 	}
543 }
544 
545 static __always_inline void
546 ladder_smallloop_cmult_small_loop_step(u64 *nq, u64 *nqpq, u64 *nq2, u64 *nqpq2,
547 				       u64 *q, u8 byt)
548 {
549 	u64 bit0 = (u64)(byt >> 7);
550 	u64 bit;
551 	point_swap_conditional(nq, nqpq, bit0);
552 	addanddouble_fmonty(nq2, nqpq2, nq, nqpq, q);
553 	bit = (u64)(byt >> 7);
554 	point_swap_conditional(nq2, nqpq2, bit);
555 }
556 
557 static __always_inline void
558 ladder_smallloop_cmult_small_loop_double_step(u64 *nq, u64 *nqpq, u64 *nq2,
559 					      u64 *nqpq2, u64 *q, u8 byt)
560 {
561 	u8 byt1;
562 	ladder_smallloop_cmult_small_loop_step(nq, nqpq, nq2, nqpq2, q, byt);
563 	byt1 = byt << 1;
564 	ladder_smallloop_cmult_small_loop_step(nq2, nqpq2, nq, nqpq, q, byt1);
565 }
566 
567 static __always_inline void
568 ladder_smallloop_cmult_small_loop(u64 *nq, u64 *nqpq, u64 *nq2, u64 *nqpq2,
569 				  u64 *q, u8 byt, u32 i)
570 {
571 	while (i--) {
572 		ladder_smallloop_cmult_small_loop_double_step(nq, nqpq, nq2,
573 							      nqpq2, q, byt);
574 		byt <<= 2;
575 	}
576 }
577 
578 static __always_inline void ladder_bigloop_cmult_big_loop(u8 *n1, u64 *nq,
579 							  u64 *nqpq, u64 *nq2,
580 							  u64 *nqpq2, u64 *q,
581 							  u32 i)
582 {
583 	while (i--) {
584 		u8 byte = n1[i];
585 		ladder_smallloop_cmult_small_loop(nq, nqpq, nq2, nqpq2, q,
586 						  byte, 4);
587 	}
588 }
589 
590 static void ladder_cmult(u64 *result, u8 *n1, u64 *q)
591 {
592 	u64 point_buf[40] = { 0 };
593 	u64 *nq = point_buf;
594 	u64 *nqpq = point_buf + 10;
595 	u64 *nq2 = point_buf + 20;
596 	u64 *nqpq2 = point_buf + 30;
597 	point_copy(nqpq, q);
598 	nq[0] = 1;
599 	ladder_bigloop_cmult_big_loop(n1, nq, nqpq, nq2, nqpq2, q, 32);
600 	point_copy(result, nq);
601 }
602 
603 static __always_inline void format_fexpand(u64 *output, const u8 *input)
604 {
605 	const u8 *x00 = input + 6;
606 	const u8 *x01 = input + 12;
607 	const u8 *x02 = input + 19;
608 	const u8 *x0 = input + 24;
609 	u64 i0, i1, i2, i3, i4, output0, output1, output2, output3, output4;
610 	i0 = get_unaligned_le64(input);
611 	i1 = get_unaligned_le64(x00);
612 	i2 = get_unaligned_le64(x01);
613 	i3 = get_unaligned_le64(x02);
614 	i4 = get_unaligned_le64(x0);
615 	output0 = i0 & 0x7ffffffffffffLLU;
616 	output1 = i1 >> 3 & 0x7ffffffffffffLLU;
617 	output2 = i2 >> 6 & 0x7ffffffffffffLLU;
618 	output3 = i3 >> 1 & 0x7ffffffffffffLLU;
619 	output4 = i4 >> 12 & 0x7ffffffffffffLLU;
620 	output[0] = output0;
621 	output[1] = output1;
622 	output[2] = output2;
623 	output[3] = output3;
624 	output[4] = output4;
625 }
626 
627 static __always_inline void format_fcontract_first_carry_pass(u64 *input)
628 {
629 	u64 t0 = input[0];
630 	u64 t1 = input[1];
631 	u64 t2 = input[2];
632 	u64 t3 = input[3];
633 	u64 t4 = input[4];
634 	u64 t1_ = t1 + (t0 >> 51);
635 	u64 t0_ = t0 & 0x7ffffffffffffLLU;
636 	u64 t2_ = t2 + (t1_ >> 51);
637 	u64 t1__ = t1_ & 0x7ffffffffffffLLU;
638 	u64 t3_ = t3 + (t2_ >> 51);
639 	u64 t2__ = t2_ & 0x7ffffffffffffLLU;
640 	u64 t4_ = t4 + (t3_ >> 51);
641 	u64 t3__ = t3_ & 0x7ffffffffffffLLU;
642 	input[0] = t0_;
643 	input[1] = t1__;
644 	input[2] = t2__;
645 	input[3] = t3__;
646 	input[4] = t4_;
647 }
648 
649 static __always_inline void format_fcontract_first_carry_full(u64 *input)
650 {
651 	format_fcontract_first_carry_pass(input);
652 	modulo_carry_top(input);
653 }
654 
655 static __always_inline void format_fcontract_second_carry_pass(u64 *input)
656 {
657 	u64 t0 = input[0];
658 	u64 t1 = input[1];
659 	u64 t2 = input[2];
660 	u64 t3 = input[3];
661 	u64 t4 = input[4];
662 	u64 t1_ = t1 + (t0 >> 51);
663 	u64 t0_ = t0 & 0x7ffffffffffffLLU;
664 	u64 t2_ = t2 + (t1_ >> 51);
665 	u64 t1__ = t1_ & 0x7ffffffffffffLLU;
666 	u64 t3_ = t3 + (t2_ >> 51);
667 	u64 t2__ = t2_ & 0x7ffffffffffffLLU;
668 	u64 t4_ = t4 + (t3_ >> 51);
669 	u64 t3__ = t3_ & 0x7ffffffffffffLLU;
670 	input[0] = t0_;
671 	input[1] = t1__;
672 	input[2] = t2__;
673 	input[3] = t3__;
674 	input[4] = t4_;
675 }
676 
677 static __always_inline void format_fcontract_second_carry_full(u64 *input)
678 {
679 	u64 i0;
680 	u64 i1;
681 	u64 i0_;
682 	u64 i1_;
683 	format_fcontract_second_carry_pass(input);
684 	modulo_carry_top(input);
685 	i0 = input[0];
686 	i1 = input[1];
687 	i0_ = i0 & 0x7ffffffffffffLLU;
688 	i1_ = i1 + (i0 >> 51);
689 	input[0] = i0_;
690 	input[1] = i1_;
691 }
692 
693 static __always_inline void format_fcontract_trim(u64 *input)
694 {
695 	u64 a0 = input[0];
696 	u64 a1 = input[1];
697 	u64 a2 = input[2];
698 	u64 a3 = input[3];
699 	u64 a4 = input[4];
700 	u64 mask0 = u64_gte_mask(a0, 0x7ffffffffffedLLU);
701 	u64 mask1 = u64_eq_mask(a1, 0x7ffffffffffffLLU);
702 	u64 mask2 = u64_eq_mask(a2, 0x7ffffffffffffLLU);
703 	u64 mask3 = u64_eq_mask(a3, 0x7ffffffffffffLLU);
704 	u64 mask4 = u64_eq_mask(a4, 0x7ffffffffffffLLU);
705 	u64 mask = (((mask0 & mask1) & mask2) & mask3) & mask4;
706 	u64 a0_ = a0 - (0x7ffffffffffedLLU & mask);
707 	u64 a1_ = a1 - (0x7ffffffffffffLLU & mask);
708 	u64 a2_ = a2 - (0x7ffffffffffffLLU & mask);
709 	u64 a3_ = a3 - (0x7ffffffffffffLLU & mask);
710 	u64 a4_ = a4 - (0x7ffffffffffffLLU & mask);
711 	input[0] = a0_;
712 	input[1] = a1_;
713 	input[2] = a2_;
714 	input[3] = a3_;
715 	input[4] = a4_;
716 }
717 
718 static __always_inline void format_fcontract_store(u8 *output, u64 *input)
719 {
720 	u64 t0 = input[0];
721 	u64 t1 = input[1];
722 	u64 t2 = input[2];
723 	u64 t3 = input[3];
724 	u64 t4 = input[4];
725 	u64 o0 = t1 << 51 | t0;
726 	u64 o1 = t2 << 38 | t1 >> 13;
727 	u64 o2 = t3 << 25 | t2 >> 26;
728 	u64 o3 = t4 << 12 | t3 >> 39;
729 	u8 *b0 = output;
730 	u8 *b1 = output + 8;
731 	u8 *b2 = output + 16;
732 	u8 *b3 = output + 24;
733 	put_unaligned_le64(o0, b0);
734 	put_unaligned_le64(o1, b1);
735 	put_unaligned_le64(o2, b2);
736 	put_unaligned_le64(o3, b3);
737 }
738 
739 static __always_inline void format_fcontract(u8 *output, u64 *input)
740 {
741 	format_fcontract_first_carry_full(input);
742 	format_fcontract_second_carry_full(input);
743 	format_fcontract_trim(input);
744 	format_fcontract_store(output, input);
745 }
746 
747 static __always_inline void format_scalar_of_point(u8 *scalar, u64 *point)
748 {
749 	u64 *x = point;
750 	u64 *z = point + 5;
751 	u64 buf[10] __aligned(32) = { 0 };
752 	u64 *zmone = buf;
753 	u64 *sc = buf + 5;
754 	crecip(zmone, z);
755 	fmul(sc, x, zmone);
756 	format_fcontract(scalar, sc);
757 }
758 
759 void curve25519_generic(u8 mypublic[CURVE25519_KEY_SIZE],
760 			const u8 secret[CURVE25519_KEY_SIZE],
761 			const u8 basepoint[CURVE25519_KEY_SIZE])
762 {
763 	u64 buf0[10] __aligned(32) = { 0 };
764 	u64 *x0 = buf0;
765 	u64 *z = buf0 + 5;
766 	u64 *q;
767 	format_fexpand(x0, basepoint);
768 	z[0] = 1;
769 	q = buf0;
770 	{
771 		u8 e[32] __aligned(32) = { 0 };
772 		u8 *scalar;
773 		memcpy(e, secret, 32);
774 		curve25519_clamp_secret(e);
775 		scalar = e;
776 		{
777 			u64 buf[15] = { 0 };
778 			u64 *nq = buf;
779 			u64 *x = nq;
780 			x[0] = 1;
781 			ladder_cmult(nq, scalar, q);
782 			format_scalar_of_point(mypublic, nq);
783 			memzero_explicit(buf, sizeof(buf));
784 		}
785 		memzero_explicit(e, sizeof(e));
786 	}
787 	memzero_explicit(buf0, sizeof(buf0));
788 }
789