Chapter 5 – UEFI Runtime

Adding manpower to a late software project makes it later.

—Brook’s Law

This chapter describes the fundamental services that are made available in an UEFI-compliant system. The services are defined by interface functions that may be used by code running in the UEFI environment. Such code may include protocols that manage device access or extend platform capabilities. In this chapter, the runtime services will be the focus of discussion. These runtime services are functions that are available both during UEFI operation and when the OS has been launched and running.

During boot, system resources are owned by the firmware and are controlled through a variety of system services that expose callable APIs. In UEFI there are ...

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