linux-tpmdd self signed kernel failing to boot with secreboot on

[Jordan <jorhand@linux.microsoft.com>]

Hello,

I am attempting to boot the linux-tpmdd kernel and look at the TCG 2 
binary_bios_measurements.

Under the following circumstances my kernel will not boot:
* Secure boot enabled
* Booting with shim and grub2 from the Ubuntu 18 repos
* Kernel config is just taken from my ubuntu 18.04.2 install, and filled 
in with `yes '' | make oldconfig`
* Kernel signed with my own generated key. Signed using sbsign, key is 
enrolled in MOK.
* It seems to be going through the kernel's EFI stub (I see efi_printk 
message "EFI: UEFI Secure Boot is enabled")

I have tried these same steps with the same configuration with the 
mainline kernel and it boots fine.

I have traced kernel boot to the call to efi_exit_boot_services in 
arch/x86/boot/compressed/eboot at which point execution terminates. I 
see Matthew has made a couple changes in efi_main which calls exit_boot 
(and in turn calls efi_exit_boot_services).

I am wondering if anyone else has seen this issue or might understand 
better than me what is going on.

I would be happy to try to repro this issue with a more minimal config 
if someone could point me to what steps to follow. I've tried it out on 
a couple different machines with the same results.

Thanks,
Jordan