@Override
	public long readSyscallNumber(PcodeExecutorState<T> state, Reason reason) {
		return machine.getArithmetic().toLong(state.getVar(regRAX, reason), Purpose.OTHER);
	}
Construct the system call library for Linux-amd64

@param machine the machine emulating the hardware
@param fs the file system to export to the user-space program
@param program a program containing syscall definitions and conventions, likely the target
           program
@param user the "current user" to simulate
Ghidra/Features/SystemEmulation/src/main/java/ghidra/pcode/emu/linux/EmuLinuxAmd64SyscallUseropLibrary.java