Trying to install UEFI on a Pi 4 and install Gentoo

jgaz · n00b Joined: 14 Feb 2021 Posts: 42

I'm trying to install Gentoo on an 8GB model Raspberry Pi 4 with UEFI. There is a project that will allow Pi users to deploy working UEFI firmware to the Pi, here: https://github.com/pftf/RPi4. It seems to work for others, notably those attempting to install ESXi to the Raspberry Pi 4. I'm trying to get that working under Gentoo for three reasons:

1. It's a nice feature to have.
2. If I can the process can work reliably, I can document it in the Gentoo wiki.
3. The RPi3 / RPi4 UEFI firmware can be added as an ebuild improving Gentoo's Raspberry Pi 3/4 support.

I started by installing Raspberry Pi OS to an SD card and running an apt-get update and apt-get upgrade as a quick way to be 100% sure I had the latest version of rpi-eeprom. With that out of the way, I proceeded to partition my micro SD card. I created a 1GB partition for simplicity sake. This is where the Pi's native on-disk firmware is going to live as well as the third-party UEFI components. On various attempts, I've used either MBR (msdos) style partition tables or modern GPT partition tables. Theoretically, this should not matter as newer versions of the rpi-eeprom firmware support both. The 1GB partition was formatted as vfat, which as -F forced to FAT32. The esp and boot flags were set.

As I understand it, the RPi4 code UEFI only needs two things: the RPi4 code itself and a copy of sys-boot/raspberrypi-firmware in order to bring the system itself up prior to loading an OS kernel. The binary /efi/boot/bootaa64.efi, if present, will hand off execution to the OS kernel and continue the boot process. I haven't gotten that far. I'm just trying to prove out that the firmware is present and working before proceeding through the Gentoo install process which -- on a Pi -- will take many hours just to compile the kernel.

So, at this point, with the contents of the sys-boot/raspberrypi-firmware (pulled from upstream) dropped into the 1GB FAT32 partition and then RPi4 dropped into the same partition — in that order — I unmount the file system, pull the micro SD card, place it in the Pi, and cross my fingers. So far, no luck.

I get an error screen with a QR code and errors to the effect of "can't find the boot partition" or "start.elf [and friends] missing" etc. This really has me scratching my head because it's just a FAT32 partition and, as I understand it, all of the files required to bring the system up are present. Again, I have tried it with an MBR partition table and a GPT partition table —neither seem to work.

Has anyone else here deployed UEFI firmware to the Raspberry Pi 3/4 successfully? I am I stopping to check my work too early in the installation process? Have I missed a step? Is there something subtle I'm missing? I'm really confused at this point, because I thought I had a decent understanding of how the Pi boots and brings up the system. Any help would be greatly appreciated. If I can get this to work I will document it for others.

NB: I did see the note in RPi4's README about requiring kernel 5.12 or greater for some features. When I get that far, I'll go with kernel 5.15.32 even if I have to unmask it.

fedeliallalinea · Posted: Tue Jan 24, 2023 5:22 am Post subject:

Moved from Installing Gentoo to Gentoo on ARM.
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NeddySeagoon · Posted: Tue Jan 24, 2023 10:29 am Post subject:

jgaz,

My understanding is that the Pi4 EFI firmware is loaded by the normal startup process in place of the kernel.
The GPU needs the Pi 4 version of the firmware ... that's all the start and fixup files with 4 in their names.

When it reads /boot/config.txt, it will need at least a kernel line that points to the EFI file to be loaded, unless its called kernel8.img, which is the default 64 bit kernel name.

The default kernel takes about an hour to build on a Pi4 with adequate cooling.

I've not done EFI on PI 4 yet. Its well down my TODO list as its an extra step in the boot process which does not appear to add anything.

The PI boot process is that the ARM CPU is held reset, while the GPU runs bootcode.bin and he required start/fixup files.
On the Pi4, bootcode.bin is replaced with the onboard SPI ROM.
Once everything to start the ARM CPU is in RAM, the CPU is released from reset.
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NeddySeagoon

Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.

pingtoo · Posted: Tue Jan 24, 2023 3:43 pm Post subject:

NeddySeagoon,

This config use armstub=RPI_EFI.fd to start EFI bootloader.

jgaz,

I am interesting in this topic, I don't use EFI for myself, however I am playing u-boot on my RPI 1b, so I know a little bit of boot sequence.

I think to debug this, we need to first know what is content of SD card, We also want to see SD card partition table information. So if you can share,

jgaz · n00b Joined: 14 Feb 2021 Posts: 42

NeddySeagoon · Posted: Tue Jan 24, 2023 5:20 pm Post subject:

jgaz,

You have

jgaz · n00b Joined: 14 Feb 2021 Posts: 42

jgaz · n00b Joined: 14 Feb 2021 Posts: 42

I can confirm I was able to boot the Pi into UEFI mode now that I grabbed the archive with the pre-built binary. From this point, I'm not sure if I need a boot loader to bring up the Linux kernel or not.

pingtoo · Posted: Tue Jan 24, 2023 7:45 pm Post subject:

The RPi4_UEFI_Firmware_v1.34.zip only provide you EFI bootloader, no kernel or anything else.

You will need to go into shell to see what was default setup and either put stuff to match the default setup or modify default to match your boot partition.

You can try to press <F1> to launch UEFI shell.

You can try "help" as command to see what this firmware offer.

NeddySeagoon · Posted: Tue Jan 24, 2023 7:50 pm Post subject:

jgaz,

jgaz · n00b Joined: 14 Feb 2021 Posts: 42

pingtoo · Posted: Tue Jan 24, 2023 8:10 pm Post subject:

NeddySeagoon · Posted: Tue Jan 24, 2023 8:14 pm Post subject:

jgaz,

I would cross compile a Pi kernel, as an EFI stub kernel, with an embedded kernel command line ad put that at efi/boot/bootaa64.efi.
It would boot that directly that the EFI firmware had done its thing. That's my get out of jail free card.

Once it was up, install grub and play with efibootmgr in the normal amd64 handbook way.

Without a chroot, how do you use the grub autoblackmagic to write grub.cfg?
Well, you can use QEMU to run an arm64 chroot on any random host but that's a lot of work.
_________________
Regards,

NeddySeagoon

Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.