Windows Executable JIT Memory in Golang

winjit.go

package main

// Executable memory / JIT in Golang for Windows
// Linux see:
// 		https://medium.com/kokster/writing-a-jit-compiler-in-golang-964b61295f

import (
	"log"
	"reflect"
	"syscall"
	"unsafe"
)

type intFunc func() (int, int)

func main() {
	bs := []byte{
		// mov rax, 5
		0x48, 0xC7, 0xC0, 0x05, 0x00, 0x00, 0x00,
		// mov [rsp+8], rax
		0x48, 0x89, 0x44, 0x24, 0x08,
		// mov rax, 65535
		0x48, 0xC7, 0xC0, 0xFF, 0xFF, 0x00, 0x00,
		// mov [rsp+16], rax 
		0x48, 0x89, 0x44, 0x24, 0x10,
		// ret
		0xC3}
	size := len(bs)

	h, err := syscall.CreateFileMapping(
		syscall.InvalidHandle,
		nil,
		syscall.PAGE_EXECUTE_READWRITE,
		0,
		uint32(size),
		nil,
	)
	if err != nil {
		log.Fatal("create ", err)
	}

	addr, err := syscall.MapViewOfFile(
		h,
		syscall.FILE_MAP_READ|syscall.FILE_MAP_WRITE|syscall.FILE_MAP_EXECUTE,
		0,
		0,
		uintptr(size),
	)
	if err != nil {
		log.Fatal("map ", err)
	}

	var sh reflect.SliceHeader
	sh.Data = addr
	sh.Len = size
	sh.Cap = size
	bsx := *(*[]byte)(unsafe.Pointer(&sh))

	copy(bsx, bs)

	log.Println(bsx)

	unsafeFunc := (uintptr)(unsafe.Pointer(&bsx))
	retN := *(*intFunc)(unsafe.Pointer(&unsafeFunc))
	val5, valFFFF := retN()
	log.Println("from go", val5, valFFFF)

	err = syscall.CloseHandle(h)
	if err != nil {
		log.Fatal("close ", err)
	}
}