This package demonstrates an AArch64 UEFI implementation for hacked Lumia 950 XL. Currently it is able to boot Windows 10 ARM64 (with a minor patch). Booting Linux is also possible if seven cores are disabled in ACPI tables (due to the TZ implementation).

If you are familar with EDK2, you don't need to use my build script.

• Checkout a copy of EDK2, then checkout this repository under EDK2's worktree.
• Commit 0e2a5749d89c96e3e17ea458365d2e5296c807e2 absoultely works for you.
• Install Linaro AArch64 GCC toolchains, my build script uses gcc-linaro-7.2.1-2017.11. Then untar them. I place everything under /opt directory, so I have directories like /opt/gcc-linaro-7.2.1-2017.11-x86_64_aarch64-elf/bin. If you placed it somewhere else, modify build scripts.
• Copy rundbbuild.sh in Tools directory to your EDK2 worktree root directory.
• Export variable GCC5_AARCH64_PREFIX to your GCC directory with prefix (e.g. /opt/gcc-linaro-7.2.1-2017.11-x86_64_aarch64-elf/bin/aarch64-elf-)
• Enable -mfix-cortex-a53-835769 -mfix-cortex-a53-843419 flags in GCC will make you day better.
• Start build: . rundbbuild.sh --950xl --development

Per UEFI specification, ARM32 UEFI cannot boot ARM64 binaries directly. To run this UEFI build on Lumia 950 XL, the following procedure is required:

• Check out Boot Shim. This Boot Manager Application implements a simple ELF loader for the kickstarter (LK).
• Check out LK. You need msm8994-test-2 branch. Build MSM8994 target, then you will get a emmc_appsboot.mbn file.
• Re-partition your Lumia 950XL, shrink Data partition, create a new partition with GPT name boot, and another uefi_vars (reserved for further use). 4MB for both partition is okay. Tools like cgdisk is recommended.
• Place emmc_appsboot.mbn in the WP EFIESP root directory, copy Boot Shim EFI appliction to the EFIESP partition, create a new BCD entry for it.
• Boot to this BCD entry, you should enter Android Fastboot mode.
• Connect to your computer, flash the build: fastboot flash boot UEFI.elf
• Continue to UEFI: fastboot continue

To re-flash UEFI, press volume down until Fastboot device shows up (like flashing Android phones).

Go to your EDK2 worktree, find MdePkg/Include/AArch64/ProcessorBind.h:

- #define RUNTIME_PAGE_ALLOCATION_GRANULARITY (0x10000)
+ #define RUNTIME_PAGE_ALLOCATION_GRANULARITY (0x1000)

This issue will be addressed with improved memory allocation in the future.

Qualcomm Snapdragon MSM8992/MSM8994 implements a subset of PSCI interface for multi-processor startup. However, required commands like PSCI_SYSTEM_OFF and PSCI_SYSTEM_RESET are not implemented. Hence we use PMIC to shutdown platform (there's a bug in RT that will be fixed) instead of PSCI. Additionally, 8992/8994 uses HVC call for PSCI commands instead of SMC call. It seems that Linux encounters some troubles during MP startup.

The ACPI tables are copied from stock Windows Phone FFU, hence these device IDs are likely not be recognized by Linux. A proper device tree is still required to boot Linux. If you are interested, you are welcome to contribute.

• EFIDroid Project

All code except drivers in GPLDriver directory are licensed under BSD 2-Clause. GPL Drivers are licensed under GPLv2 license.