@Override
	public void invoke(PcodeExecutor<T> executor, PcodeUseropLibrary<T> library) {
		try {
			opdef.execute(executor, library, outVar, inVars);
		}
		catch (PcodeExecutionException e) {
			throw e;
		}
		catch (Throwable e) {
			throw new EmuSystemException("Error during syscall", null, e);
		}
	}
Assert variable storage is a single varnode, and get that varnode

@param vs the storage
@return the single varnode
Ghidra/Features/SystemEmulation/src/main/java/ghidra/pcode/emu/sys/UseropEmuSyscallDefinition.java