1. A method of authenticating entry into a trusted environment of a computing device having selectively enabled hardware and having a processor configured to execute non-trusted software and trusted software, wherein said trusted software includes an authentication routine and a privileged routine, and wherein said privileged routine is configured to access said selectively enabled hardware and said non-trusted software is prevented from accessing said selectively enabled hardware, said method comprising: configuring said authentication routine to include an immediate-operand instruction; transferring said immediate-operand instruction from a trusted data section to said processor in response to an instruction fetch by said processor addressed to said trusted data section; and enabling said selectively enabled hardware in response to execution of said immediate-operand instruction; wherein said privileged routine is executed upon exit from said authentication routine.