Enhancing EFI Boot and Developer Experience

written by Simon Glass | 7 October 2025

We’ve just rolled out a series of updates aimed at improving the U-Boot EFI application, with a special focus on streamlining the testing and debugging process, particularly for ARM platforms. This batch of 24 patches introduces several quality-of-life improvements, from better debugging tools to more robust boot procedures. Let’s dive into the key changes.

Streamlining the Boot Process with ‘Fake Go’ 🚀

One of the standout features in this release is the introduction of a ‘fake go’ option for the boot process. Previously available only for tracing, this feature is now a standalone debugging tool enabled by CONFIG_BOOTM_FAKE_GO.

When you initiate a boot with the ‘fake go’ flag (e.g., bootflow boot -f or bootm fake), U-Boot performs all the necessary steps to prepare for booting an OS—loading the kernel, setting up the device tree, and preparing memory—but stops just short of jumping to the OS. This allows you to inspect the system’s state at the final moment before handoff, which is invaluable for debugging complex boot issues without needing a full OS boot cycle.

Pager Improvements for Better Interaction 📄

The console pager is a useful tool, but it can be cumbersome when you’re working without a serial console or need to quickly bypass lengthy output. We’ve introduced two new ways to control the pager on the fly:

  • Quit and Suppress (q): Pressing q at the pager prompt will now immediately stop all further output for the current command. This is perfect for when you’ve seen what you need and want to return to the prompt without sitting through pages of text.
  • Bypass Session (Q): Pressing Q will put the pager into bypass mode for the rest of your U-Boot session, allowing all subsequent commands to print their full output without interruption.

These small changes make console interaction much more fluid and give you greater control over command output.

Key Fixes and Enhancements 🛠️

Alongside these major features, this series includes a number of other smaller updates:

  • Safer Image Relocation on ARM: We’ve improved how kernel images are relocated on ARM. Instead of moving the image to a static offset, which could risk overwriting other critical data like the device tree, U-Boot now uses the LMB (Logical Memory Block) library to safely allocate a new, unused region of memory.
  • Improved Debugging Output: We’ve added more detailed debug messages throughout the boot process, especially in FIT image handling and device tree selection, making it easier to trace the boot flow and diagnose issues.
  • Cleaner ATAGs Messaging: The often-confusing “FDT and ATAGS support not compiled in” error has been clarified. U-Boot will now correctly report when a device tree is missing, preventing developers from going down the wrong path when debugging.
  • CI and Build Fixes: A few patches have been included to fix a bug in our automated release script that was causing CI failures, ensuring our development and release processes remain smooth.

These updates continue the development of the EFI app, while benefiting others boards as well.