1. A method, comprising: instantiating, in a pre-boot environment of a computing device without a hardware trusted platform module, a software-based trusted platform module in protected memory of the computing device; passing a command, issued by a caller instantiated within non-protected memory of the computing device, to the software-based trusted platform module to perform an operation; and using the software-based trusted platform module to interface with a security extension of a processor of the computing device to perform the operation in secure execution isolation.