Re: [PATCH v7] efi: Do not import certificates from UEFI Secure Boot for T2 Macs

On Fri, 2022-05-13 at 18:31 +0000, Aditya Garg wrote:

quoted

Are there directions for installing Linux on a Mac with Apple firmware
code?  

Well, directions of installing Linux on an Intel based Mac, which
includes the T2 Macs is the same as on a normal PC.

Though, in case of T2 Macs, we for now need to use customised ISOs,
since some drivers and patches to support T2 Macs are yet to be
upstreamed.

An example of installing Ubuntu can be read here on 
https://wiki.t2linux.org/distributions/ubuntu/installation/

Talking about the official ISOs, for many distros, since
CONFIG_LOAD_UEFI_KEYS is not enabled in their kernel config, we can
install Linux using them, but they still lack many drivers required,
since they are yet to be upstreamed. So the installation doesn’t work
efficiently and we have to manually install custom kernels having
those patches.

In some distros like Ubuntu, they have CONFIG_LOAD_UEFI_KEYS enabled
in their kernel config. In this case the crash as mentioned in the
patch description occurs and EFI Runtime Services get disabled. Since
installing GRUB requires access to NVRAM, the installation fails with
official ISOs in this case. Thus, a custom ISO, with this patch
incorporated in being used for now for users interested in Ubuntu on
T2 Macs.

quoted

Are you dual booting Linux and Mac, or just Linux?

I don’t think it actually matters, though in most of the cases, we
dual boot macOS and Linux, but I do have seen cases who wipe out
their macOS completely. But this doesn't affect the Secure Boot
policy of these machines.

quoted

 While in
secure boot mode, without being able to read the keys to verify the
kernel image signature, the signature verification should fail.

If I enable secure boot in the BIOS settings (macOS Recovery),
Apple’s firmware won't allow even the boot loader like GRUB, rEFInd
to boot. It shall only allow Windows and macOS to Boot. You could see
https://support.apple.com/en-in/HT208198 for more details.

quoted

Has anyone else tested this patch?

I work as a maintainer for Ubuntu for T2 Linux community and I have
this patch incorporated in the kernels used for Ubuntu ISOs
customised for T2 Macs, and thus have many users who have used the
ISO and have a successful installation. Thus, there are many users
who have tested this patch and are actually using it right now.
We also need the have the NVRAM writes enabled so as to unlock the
iGPU in Macs with both Intel and AMD GPU, and with this patch, we
have been successfully able to unlock it,

I hope I could answer your questions

Yes, thank you.   Based on the link above and 
https://wiki.t2linux.org/guides/kernel/, I was able boot a kernel
with/without this patch.

The patch is now queued in the next-integrity-testing branch.

thanks,

Mimi