Hi, I'm looking for any information I can find on the .efis that bootmgr loads. The recent policy leak for SecureBoot has allowed bootmgr to load custom images from bootmgr (sadly the signature enforcement is still in place for normal .efis ), and I am looking for a way to create a PE I can load from there to (hopefully) load grub. For now I'm aiming for a Hello World. Where I'm at: The PEs that bootmgr runs have a different subsystem (0x10 vs. 0x0A) and the entrypoint uses a different prototype. If I fix these two things up I can create an image that loads then instantly kicks me back to the bootmgr menu, but doing any EFI call results in a hang. I'm sure there's something massive I'm missing but I can't figure out what. I'm hoping for any and all information I can find on the applications. All I presently have to go off of is the half-implemented bootmgr from ReactOS and what cdb can tell me, and it's not going too well. Apologies if this isn't the appropriate subforum, it was the closest I could see.