Programming for EFI

by Roderick W. Smith, rodsmith@rodsbooks.com

Originally written: 5/3/2013

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Introduction

Tech-savvy individuals know the Extensible Firmware Interface (EFI) and its newer variant, the Unified EFI (UEFI) as a replacement for the older Basic Input/Output System (BIOS) on PCs and other computers. What you may not be aware of is that EFI is a complex software environment, comparable in size and features to a simple OS such as DOS. As such, EFI can host a variety of programs—but those programs can't spring into existence fully-formed, like Athena from Zeus' head. Rather, they must be written by individuals.

This set of Web pages exists for the benefit of those individuals who want to write EFI programs. I assume you're already familiar with C programming. I also use a Linux system as my reference development platform, although in theory the programs and procedures described here can be used under OS X or Windows, too. These pages just scratch the surface of EFI programming; they will get you started, but you'll need to learn considerably more to write a significant program. If you'd like me to continue this series, please make a donation (and feel free to write me suggesting topics)!

Topics covered are:

• Why Write for EFI?
• Preparing a Development Environment
• Creating a "Hello, World" Program
• Using EFI Services

• Informational Web pages
  • Phoenix Technologies maintains a wiki on EFI topics, including information on many EFI system calls useful to programmers.
  • Matthew J. Garrett, the developer of the shim boot loader to manage Secure Boot, maintains a blog in which he often writes about EFI issues, and occasionally about EFI programming.
• Additional programs
  • The GNU-EFI Sourceforge page
  • The TianoCore Sourceforge page
• Communications
  • A few mailing lists exist for the TianoCore EDK II development kit. Although I emphasize the competing GNU-EFI development kit in these pages, the TianoCore mailing lists can be a useful resource.
  • You can e-mail me with queries.

copyright © 2013 by Roderick W. Smith

If you have problems with or comments about this Web page, please e-mail me at rodsmith@rodsbooks.com. Thanks.

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