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Everything about Windows Phone devices

Firmware

Firmware

Qualcomm Bootloaders

Windows Phones has had two different major bootloader revisions across its life span. Various changes have been made to the entire bootchain and emergency download 9008 technologies. For easier understanding, we will have to differentiate both bootloaders in this article.

Terminology

Starting with the Qualcomm Snapdragon 800, Qualcomm Snapdragon 610, Qualcomm Snapdragon 400 (msm8x26) and the Qualcomm Snapdragon 210 respectively, Windows Phones used a new type of bootloader we will call in this section Bootloader Spec B.

For the rest of the supported Qualcomm Snapdragon Processors on Windows Phone, we will call these in this section Bootloader Spec A.

Differences

Bootloader Spec A

Devices with a Bootloader Spec A typically include 3 Secondary bootloaders, SBL1, SBL2 and SBL3 respectively. On Bootloader Spec A devices, SBL3 can contain code for Mass Storage mode. The UEFI non volatile storage partitions are composed of:

The format for these partitions differ with Bootloader Spec B.

These bootloaders do not implement the necessary UEFI interfaces for UEFI Mass Storage mode functionality to work (typically via Mobile Startup or Developer Menu) and thus can only use SBL3 mass storage implementations. They also do not implement the necessary UEFI interfaces for Secure WIM loading via FFU Loader.

Bootloader Spec B

Devices with a Bootloader Spec A typically include 1 Secondary bootloader: SBL1. No SBL3 is present, removing the ability to have a SBL3 with code for Mass Storage mode. The UEFI non volatile storage partitions are composed of:

The format for these partitions differ with Bootloader Spec B.

These bootloaders do implement the necessary UEFI interfaces for UEFI Mass Storage mode functionality to work (typically via Mobile Startup or Developer Menu) and can't use SBL3 mass storage implementations. They also do implement the necessary UEFI interfaces for Secure WIM loading via FFU Loader.

Exploits

Bootloader Spec A
Bootloader Spec B

Bootloader

Bootloader

Configuring a Lumia for Flight Signing

In this article we will discuss how to configure a Lumia for Flight Signing.

As of 2017, the old Windows Insider application has been shut down, and thus hacks are required to enable Flight Signing on devices.

Preparations

Bootloader Spec A

Primary method (Easiest)
Alternative method to not cause issues with delta packages (CBSU/SPKU)

If you do not want interferences with updates caused by a patched mobilestartup.efi file, you can proceed to the following:

Bootloader Spec B

OS

File formats

File formats

CBS/CBSU/CBSR

File formats

SPKG/SPKU/SPKR