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// Copyright 2018 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
//go:build gc && !purego
// +build gc,!purego
#include "go_asm.h"
#include "textflag.h"
// This is an implementation of the ChaCha20 encryption algorithm as
// specified in RFC 7539. It uses vector instructions to compute
// 4 keystream blocks in parallel (256 bytes) which are then XORed
// with the bytes in the input slice.
GLOBL ·constants<>(SB), RODATA|NOPTR, $32
// BSWAP: swap bytes in each 4-byte element
DATA ·constants<>+0x00(SB)/4, $0x03020100
DATA ·constants<>+0x04(SB)/4, $0x07060504
DATA ·constants<>+0x08(SB)/4, $0x0b0a0908
DATA ·constants<>+0x0c(SB)/4, $0x0f0e0d0c
// J0: [j0, j1, j2, j3]
DATA ·constants<>+0x10(SB)/4, $0x61707865
DATA ·constants<>+0x14(SB)/4, $0x3320646e
DATA ·constants<>+0x18(SB)/4, $0x79622d32
DATA ·constants<>+0x1c(SB)/4, $0x6b206574
#define BSWAP V5
#define J0 V6
#define KEY0 V7
#define KEY1 V8
#define NONCE V9
#define CTR V10
#define M0 V11
#define M1 V12
#define M2 V13
#define M3 V14
#define INC V15
#define X0 V16
#define X1 V17
#define X2 V18
#define X3 V19
#define X4 V20
#define X5 V21
#define X6 V22
#define X7 V23
#define X8 V24
#define X9 V25
#define X10 V26
#define X11 V27
#define X12 V28
#define X13 V29
#define X14 V30
#define X15 V31
#define NUM_ROUNDS 20
#define ROUND4(a0, a1, a2, a3, b0, b1, b2, b3, c0, c1, c2, c3, d0, d1, d2, d3) \
VAF a1, a0, a0 \
VAF b1, b0, b0 \
VAF c1, c0, c0 \
VAF d1, d0, d0 \
VX a0, a2, a2 \
VX b0, b2, b2 \
VX c0, c2, c2 \
VX d0, d2, d2 \
VERLLF $16, a2, a2 \
VERLLF $16, b2, b2 \
VERLLF $16, c2, c2 \
VERLLF $16, d2, d2 \
VAF a2, a3, a3 \
VAF b2, b3, b3 \
VAF c2, c3, c3 \
VAF d2, d3, d3 \
VX a3, a1, a1 \
VX b3, b1, b1 \
VX c3, c1, c1 \
VX d3, d1, d1 \
VERLLF $12, a1, a1 \
VERLLF $12, b1, b1 \
VERLLF $12, c1, c1 \
VERLLF $12, d1, d1 \
VAF a1, a0, a0 \
VAF b1, b0, b0 \
VAF c1, c0, c0 \
VAF d1, d0, d0 \
VX a0, a2, a2 \
VX b0, b2, b2 \
VX c0, c2, c2 \
VX d0, d2, d2 \
VERLLF $8, a2, a2 \
VERLLF $8, b2, b2 \
VERLLF $8, c2, c2 \
VERLLF $8, d2, d2 \
VAF a2, a3, a3 \
VAF b2, b3, b3 \
VAF c2, c3, c3 \
VAF d2, d3, d3 \
VX a3, a1, a1 \
VX b3, b1, b1 \
VX c3, c1, c1 \
VX d3, d1, d1 \
VERLLF $7, a1, a1 \
VERLLF $7, b1, b1 \
VERLLF $7, c1, c1 \
VERLLF $7, d1, d1
#define PERMUTE(mask, v0, v1, v2, v3) \
VPERM v0, v0, mask, v0 \
VPERM v1, v1, mask, v1 \
VPERM v2, v2, mask, v2 \
VPERM v3, v3, mask, v3
#define ADDV(x, v0, v1, v2, v3) \
VAF x, v0, v0 \
VAF x, v1, v1 \
VAF x, v2, v2 \
VAF x, v3, v3
#define XORV(off, dst, src, v0, v1, v2, v3) \
VLM off(src), M0, M3 \
PERMUTE(BSWAP, v0, v1, v2, v3) \
VX v0, M0, M0 \
VX v1, M1, M1 \
VX v2, M2, M2 \
VX v3, M3, M3 \
VSTM M0, M3, off(dst)
#define SHUFFLE(a, b, c, d, t, u, v, w) \
VMRHF a, c, t \ // t = {a[0], c[0], a[1], c[1]}
VMRHF b, d, u \ // u = {b[0], d[0], b[1], d[1]}
VMRLF a, c, v \ // v = {a[2], c[2], a[3], c[3]}
VMRLF b, d, w \ // w = {b[2], d[2], b[3], d[3]}
VMRHF t, u, a \ // a = {a[0], b[0], c[0], d[0]}
VMRLF t, u, b \ // b = {a[1], b[1], c[1], d[1]}
VMRHF v, w, c \ // c = {a[2], b[2], c[2], d[2]}
VMRLF v, w, d // d = {a[3], b[3], c[3], d[3]}
// func xorKeyStreamVX(dst, src []byte, key *[8]uint32, nonce *[3]uint32, counter *uint32)
TEXT ·xorKeyStreamVX(SB), NOSPLIT, $0
MOVD $·constants<>(SB), R1
MOVD dst+0(FP), R2 // R2=&dst[0]
LMG src+24(FP), R3, R4 // R3=&src[0] R4=len(src)
MOVD key+48(FP), R5 // R5=key
MOVD nonce+56(FP), R6 // R6=nonce
MOVD counter+64(FP), R7 // R7=counter
// load BSWAP and J0
VLM (R1), BSWAP, J0
// setup
MOVD $95, R0
VLM (R5), KEY0, KEY1
VLL R0, (R6), NONCE
VZERO M0
VLEIB $7, $32, M0
VSRLB M0, NONCE, NONCE
// initialize counter values
VLREPF (R7), CTR
VZERO INC
VLEIF $1, $1, INC
VLEIF $2, $2, INC
VLEIF $3, $3, INC
VAF INC, CTR, CTR
VREPIF $4, INC
chacha:
VREPF $0, J0, X0
VREPF $1, J0, X1
VREPF $2, J0, X2
VREPF $3, J0, X3
VREPF $0, KEY0, X4
VREPF $1, KEY0, X5
VREPF $2, KEY0, X6
VREPF $3, KEY0, X7
VREPF $0, KEY1, X8
VREPF $1, KEY1, X9
VREPF $2, KEY1, X10
VREPF $3, KEY1, X11
VLR CTR, X12
VREPF $1, NONCE, X13
VREPF $2, NONCE, X14
VREPF $3, NONCE, X15
MOVD $(NUM_ROUNDS/2), R1
loop:
ROUND4(X0, X4, X12, X8, X1, X5, X13, X9, X2, X6, X14, X10, X3, X7, X15, X11)
ROUND4(X0, X5, X15, X10, X1, X6, X12, X11, X2, X7, X13, X8, X3, X4, X14, X9)
ADD $-1, R1
BNE loop
// decrement length
ADD $-256, R4
// rearrange vectors
SHUFFLE(X0, X1, X2, X3, M0, M1, M2, M3)
ADDV(J0, X0, X1, X2, X3)
SHUFFLE(X4, X5, X6, X7, M0, M1, M2, M3)
ADDV(KEY0, X4, X5, X6, X7)
SHUFFLE(X8, X9, X10, X11, M0, M1, M2, M3)
ADDV(KEY1, X8, X9, X10, X11)
VAF CTR, X12, X12
SHUFFLE(X12, X13, X14, X15, M0, M1, M2, M3)
ADDV(NONCE, X12, X13, X14, X15)
// increment counters
VAF INC, CTR, CTR
// xor keystream with plaintext
XORV(0*64, R2, R3, X0, X4, X8, X12)
XORV(1*64, R2, R3, X1, X5, X9, X13)
XORV(2*64, R2, R3, X2, X6, X10, X14)
XORV(3*64, R2, R3, X3, X7, X11, X15)
// increment pointers
MOVD $256(R2), R2
MOVD $256(R3), R3
CMPBNE R4, $0, chacha
VSTEF $0, CTR, (R7)
RET
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