Dancing with Giants: Wimpy Kernels for On-Demand Isolated I/O

To be trustworthy, security-sensitive applications must be formally verified and hence small and simple, i.e., wimpy. Thus, they cannot include a variety of basic services available only in large and untrustworthy commodity systems, i.e., in giants. Hence, wimps must securely compose with giants to survive on commodity systems, i.e., rely on giants' services but only after efficiently verifying their results. This paper presents a security architecture based on a wimpy kernel that provides on-demand isolated I/O channels for wimp applications, without bloating the underlying trusted computing base. The size and complexity of the wimpy kernel are minimized by safely outsourcing I/O subsystem functions to an untrusted commodity operating system and exporting driver and I/O subsystem code to wimp applications. Using the USB subsystem as a case study, this paper illustrates the dramatic reduction of wimpy-kernel size and complexity, e.g., over 99% of the USB code base is removed. Performance measurements indicate that the wimpy-kernel architecture exhibits the desired execution efficiency.