blob: cdcddcb7361d58431ad4b071fd2455df4962f065 [file] [log] [blame]
// Copyright 2021 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 ignore
// +build ignore
package main
import (
"bytes"
"crypto/elliptic"
"encoding/binary"
"fmt"
"go/format"
"log"
"os"
)
func main() {
buf := new(bytes.Buffer)
fmt.Fprint(buf, `
// Copyright 2021 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.
// Generated by gen_p256_table.go. DO NOT EDIT.
//go:build amd64 || arm64
// +build amd64 arm64
package elliptic
`[1:])
// Generate precomputed p256 tables.
var pre [43][32 * 8]uint64
basePoint := []uint64{
0x79e730d418a9143c, 0x75ba95fc5fedb601, 0x79fb732b77622510, 0x18905f76a53755c6,
0xddf25357ce95560a, 0x8b4ab8e4ba19e45c, 0xd2e88688dd21f325, 0x8571ff1825885d85,
0x0000000000000001, 0xffffffff00000000, 0xffffffffffffffff, 0x00000000fffffffe,
}
t1 := make([]uint64, 12)
t2 := make([]uint64, 12)
copy(t2, basePoint)
zInv := make([]uint64, 4)
zInvSq := make([]uint64, 4)
for j := 0; j < 32; j++ {
copy(t1, t2)
for i := 0; i < 43; i++ {
// The window size is 6 so we need to double 6 times.
if i != 0 {
for k := 0; k < 6; k++ {
elliptic.P256PointDoubleAsm(t1, t1)
}
}
// Convert the point to affine form. (Its values are
// still in Montgomery form however.)
elliptic.P256Inverse(zInv, t1[8:12])
elliptic.P256Sqr(zInvSq, zInv, 1)
elliptic.P256Mul(zInv, zInv, zInvSq)
elliptic.P256Mul(t1[:4], t1[:4], zInvSq)
elliptic.P256Mul(t1[4:8], t1[4:8], zInv)
copy(t1[8:12], basePoint[8:12])
// Update the table entry
copy(pre[i][j*8:], t1[:8])
}
if j == 0 {
elliptic.P256PointDoubleAsm(t2, basePoint)
} else {
elliptic.P256PointAddAsm(t2, t2, basePoint)
}
}
fmt.Fprint(buf, "const p256Precomputed = \"\" +\n\n")
// Dump the precomputed tables, flattened, little-endian.
// These tables are used directly by assembly on little-endian platforms.
// Putting the data in a const string lets it be stored readonly.
for i := range &pre {
for j, v := range &pre[i] {
fmt.Fprintf(buf, "\"")
var u8 [8]byte
binary.LittleEndian.PutUint64(u8[:], v)
for _, b := range &u8 {
fmt.Fprintf(buf, "\\x%02x", b)
}
fmt.Fprintf(buf, "\"")
if i < len(pre)-1 || j < len(pre[i])-1 {
fmt.Fprint(buf, "+")
}
if j%8 == 7 {
fmt.Fprint(buf, "\n")
}
}
fmt.Fprint(buf, "\n")
}
src := buf.Bytes()
fmtsrc, fmterr := format.Source(src)
// If formatting failed, keep the original source for debugging.
if fmterr == nil {
src = fmtsrc
}
err := os.WriteFile("p256_asm_table.go", src, 0644)
if err != nil {
log.Fatal(err)
}
if fmterr != nil {
log.Fatal(fmterr)
}
}