call execve from nodejs!

libc.js

const { syscall, getAddress } = require("libsys");
const os = require("os");

if (os.endianess() != "LE")
	throw "only little endian supported";

let dontGC = [];
function ref(buffer) {
	dontGC.push(buffer); 
	return getAddress(buffer);
}

const pointerSize = 8;

const SYS_execve = 59;
const SYS_dup2 = 33;

// Buffer.from(string) doesn't append a null byte
function stringToBuffer(string) {
	let buffer = Buffer.alloc(Buffer.byteLength(string)+1, 0);
	buffer.write(string);
	return buffer;
}

function stringArrayToBuffer(strings) {
	let buffer = Buffer.alloc((strings.length+1)*pointerSize, 0);
	let offset = 0;
	for (let string of strings) {
		let stringBuffer = stringToBuffer(string);
		let pos = ref(stringBuffer);
		buffer.writeInt32LE(pos[0], offset);
		buffer.writeInt32LE(pos[1], offset+4);
		offset += 8;
	}
	return buffer;
}

function dup2(oldfd, newfd) {
	return syscall(SYS_dup2, oldfd, newfd);
}

function execve(cmd, argv, envp) {
	let cmdBuf = stringToBuffer(cmd);
	let argvBuf = stringArrayToBuffer(argv);
	let envpBuf = stringArrayToBuffer(envp);
	return syscall(SYS_execve, cmdBuf, argvBuf, envpBuf);
}

let cmd = "/bin/ls";
let argv = ["/bin/ls", "-la"];
let envp = [
	"HOME=/",
	"PATH=/bin",
];

dup2(process.stdin._handle.fd, 0);
dup2(process.stdout._handle.fd, 1);
dup2(process.stderr._handle.fd, 2);
execve(cmd, argv, envp);