Beyond BIOS

Developing with the Unified Extensible Firmware Interface, Third Edition

Vincent Zimmer, Michael Rothman, Suresh Marisetty

• Publisher: De|G Press
• Year: 2017
• eBook ISBN: 9781501505836
• Edition: 1
• Topic: Computer Science
• Subtopic: Operating Systems
• Index: Computer Science

This book provides an overview of modern boot firmware, including the Unified Extensible Firmware Interface (UEFI) and its associated EFI Developer Kit II (EDKII) firmware. The authors have each made significant contributions to developments in these areas. The reader will learn to use the latest developments in UEFI on modern hardware, including open source firmware and open hardware designs. The book begins with an exploration of interfaces exposed to higher-level software and operating systems, and commences to the left of the boot timeline, describing the flow of typical systems, beginning with the machine restart event.

Software engineers working with UEFI will benefit greatly from this book, while specific sections of the book address topics relevant for a general audience: system architects, pre-operating-system application developers, operating system vendors (loader, kernel), independent hardware vendors (such as for plug-in adapters), and developers of end-user applications. As a secondary audience, project technical leaders or managers may be interested in this book to get a feel for what their engineers are doing.

The reader will find:

• An overview of UEFI and underlying Platform Initialization (PI) specifications
• How to create UEFI applications and drivers
• Workflow to design the firmware solution for a modern platform
• Advanced usages of UEFI firmware for security and manageability

Chapter 1 – Introduction

The suddenness of the leap from hardware to software cannot but produce a period of anarchy and collapse, especially in the developed countries.

—Marshall McLuhan

This chapter provides an overview of the evolution of the Extensible Firmware Interface (EFI) to the Unified Extensible Firmware Interface (UEFI) and from the Intel Framework specifications to the UEFI Platform Initialization (PI) specifications. Note the omission of the word “Framework” from the title of the present volume. Some of the changes that have occurred since the first edition of this book include the migration of much of the Intel Framework specification content into the five volumes of the UEFI Platform Initialization (PI) specifications, which are presently at revision 1.5 and can be found at the Web site www.uefi.org. In addition to the PI evolution from Framework, additional capabilities have evolved in both the PI building-block specifications and in the UEFI specification. The UEFI specification itself has evolved to revision 2.6 in the time since the first edition of this text, as well.

When we discuss UEFI, we need to emphasize that UEFI is a pure interface specification that does not dictate how the platform firmware is built; the “how” is relegated to PI. The consumers of UEFI include but are not limited to operating system loaders, installers, adapter ROMs from boot devices, pre-OS diagnostics, utilities, and OS runtimes (for the small set of UEFI runtime services). In general, though, UEFI is about booting, or passing control to a successive layer of control, namely an operating system loader, as shown in Figure 1.1. UEFI offers many interesting capabilities and can exist as a limited runtime for some application set, in lieu of loading a full, shrinkwrapped multi-address space operating system like Microsoft Windows†, Apple OS X†, HP-UX†, or Linux, but that is not the primary design goal.

Figure 1.1: Where EFI and UEFI Fit into the Platform Boot Flow

PI, on the other hand, should be largely opaque to the pre-OS boot devices, operating systems, and their loaders since it covers many software aspects of platform construction that are irrelevant to those consumers. PI instead describes the phases of control from the platform reset and into the success phase of operation, including an environment compatible with UEFI, as shown in Figure 1.2. In fact, the PI DXE component is the preferred UEFI core implementation.

Figure 1.2: Where PI and Framework Fit into the Platform Boot Flow

Within the evolution of Framework to PI, some things were omitted from inclusion in the PI specifications. As a result of these omissions, some subjects that were discussed in the first edition of Beyond BIOS, such as the compatibility support module (CSM), have been removed from the second edition in order to provide space to describe the newer PI and UEFI capabilities. This omission is both from a scope perspective, namely that the PI specification didn’t want to codify or include the CSM, but also from a long-term perspective. Specifically, the CSM specification abstracted booting on a PC/AT system. This requires an x86 processor, PC/AT hardware complex (for example, 8254, 8259, RTC). The CSM also inherited other conventional BIOS boot limitations, such as the 2.2-TB disk limit of Master Boot Record (MBR) partition tables. For a world of PI and UEFI, you get all of the x86 capabilities (IA-32 and x64, respectively), ARM†, Itanium®, and future CPU bindings. Also, via the polled driver model design, UEFI APIs, and the PI DXE architectural protocols, the platform and component hardware details are abstracted from all consumer software. Other minor omissions also include data hub support. The latter has been replaced by purpose-built infrastructure to fill the role of data hub in Framework-based implementations, such as SMBIOS table creation and agents to log report status code actions.

What has happened in PI beyond Framework, though, includes the addition of a multiprocessor protocol, Itanium E-SAL and MCA support, the above-listed reportstatus code listener and SMBIOS protocol, an ACPI editing protocol, and an SIO protocol. With Framework collateral that moved to PI, a significant update was made to the System Management Mode (SMM) protocol and infrastructure to abstract out various CPU and chipset implementations from the more generic components. On the DXE front, small cleanup was added in consideration of UEFI 2.3 incompatibility. Some ...

Table of contents

• Cover
• Title Page
• Copyright
• Acknowledgements
• Preface
• Contents
• Chapter 1 – Introduction
• Chapter 2 – Basic UEFI Architecture
• Chapter 3 – UEFI Driver Model
• Chapter 4 – Protocols You Should Know
• Chapter 5 – UEFI Runtime
• Chapter 6 – UEFI Console Services
• Chapter 7 – Different Types of Platforms
• Chapter 8 – DXE Basics: Core, Dispatching, and Drivers
• Chapter 9 – Some Common UEFI and PI Functions
• Chapter 10 – Platform Security and Trust
• Chapter 11 – Boot Device Selection
• Chapter 12 – Boot Flows
• Chapter 13 – Pre-EFI Initialization (PEI)
• Chapter 14 – Putting It All Together–Firmware Emulation
• Chapter 15 – Reducing Platform Boot Times
• Chapter 16 – Embedded Boot Solution
• Chapter 17 – Manageability
• Appendix A – Data Types
• Appendix B – Status Codes
• Index