describe strategies to fit LinuxBoot into boot chains #198
Description
coreboot and oreboot
Tools
Use the existing build system.
These projects already support providing a LinuxBoot image as a payload.
Strategy
With coreboot, it is a Kconfig option. Already in use (by who?).
With oreboot, pass an argument to the build system.
Open issues
Building the kernel etc through coreboot's build system may be intimidating and harder to grasp than building the payload independently and including it as a binary. More documentation needed for full automation.
In the case of oreboot, the LinuxBoot image must be built by the user.
We could eventually provide prebuilt ones per platform.
U-Boot
Tools
The U-Boot build system is already there.
Strategy
Rework the U-Boot build setup so that any FIT image can be provided as a payload in place of U-Boot Proper, similar to coreboot.
Allow passing an env var, just like when inserting a TF-A image.
Open issues
Keep the framework from building U-Boot proper when it's not needed.
UEFI PI
Basically retrofitting onto TianoCore and its derivatives.
This one is the trickiest, since it starts from binaries, not sources.
Tools
Strategy
Remove as many UEFI modules as necessary to gain enough space for the LinuxBoot image. Start with educated guessing and a "good enough" result.
With Fiedka, save the list of removals for sharing in a repo.
Create a simple CLI for replay, so that it can be automated.
With utk as a CLI, save the commands in a Makefile (as in linuxboot/mainboards/aeeon/up) or save the list of removals in a text file (needs better tooling; Heads had developed Perl scripts and awk snippets, see e.g. linuxboot/boards/monolake and linuxboot/Makefile).
Maybe align with Fiedka, save the removals in a JSON file and add a replay command/visitor or similar to Fiano/utk.
Possibly rework partitioning in order to gain more space; for Intel platforms, see utk's tightenme visitor or intel_fw/me_cleaner to remove unnecessary parts of the (CS)ME (e.g., consumers need no AMT).
Add a README.md with general instructions and further necessary operations. Explain the hardware setup and caveats.
Open issues
Tooling for AMD platforms still needs improvement; see Romulan and (planned) amd_fw.
How about UEFI PI on aarch64? Which vendors implement it?
For automated removal (dxecleaner) of as much as possible, a hardware tool such as 3mdeb RTE is necessary in order to reflash, reset, and monitor the result. It may take a lot of hours.