Guide [Discussion] Windows 10 — _KPRCB Structure Variations across 2004, 20H2 & 21H1

[byte_corvus]

Digging into kernel-mode development for Windows 10 and noticed Microsoft decided to shuffle the deck again with the _KPRCB (Kernel Processor Control Block) structure. If you are writing drivers or manual mapping and relying on fixed offsets, this is where your BSODs are coming from.

The shift between version 1909 and the 2004/20H2 branch is particularly annoying. Windows internal structures are notoriously volatile, but the changes here affect how you track processor-specific data, timing, and affinity.

Structure References per Build:

1909: https://www.vergiliusproject.com/kernels/x64/windows-10/1909/_KPRCB
2004: https://www.vergiliusproject.com/kernels/x64/windows-10/2004/_KPRCB
20H2: https://www.vergiliusproject.com/kernels/x64/windows-10/2004/_KPRCB
21H1: https://www.vergiliusproject.com/kernels/x64/windows-10/21h1/_KPRCB

Technical Breakdown:

1. The 2004 and 20H2 builds seem to share the same layout for this struct, but comparing them to 1909 shows significant member displacement.
2. 21H1 and 21H2 continue this trend, requiring updated signatures or dynamic offset fetching if you want your bypass to stay stable across builds.
3. If you are pulling the CurrentPrcb from the GS segment, double-check your member access logic—Microsoft has a habit of inserting new fields into the mid-section of these blocks, breaking any hardcoded assumptions.

Anyone else found specific members that changed drastically between 1909 and the 2004+ branch? It seems even newer versions like 21H2 are carrying over the shifts from the 2004 layout, but it's worth dumping it manually to be sure.

drop your findings if you've noticed more weirdness in the kernel structs lately.