gen_header_file.py is a utility script for generating a C header file for a Windows kernel type (struct, union, or enum), using the fantastic Vergilius Project ressource, which documents Windows kernel structs, unions, and enums in great detail.
The script runs interactively and fetches all available types for the provided kernel version, from which you choose one to generate a header file for. The code for this type is downloaded together with all dependencies recursively until all external types are resolved and a single standalone header file for the provided type is written.
Generating a header file for the Process Environment Block
The script was made to easily generate header files for structures often found during reverse engineering of Windows binaries (e.g. the TEB and PEB structs). The generated header files can be loaded directly into decompilers such as Ghidra and IDA and be used during analysis.
In Ghidra, choose File -> Parse C Source..., click the Clear profile icon in the top, add the generated .h-file as a source, choose Program Architecture (typically search Visual Studio and find 32- or 64-bit version of x86), and finally click Parse to Program. Optionally, save the profile for later use.
In IDA, choose View -> Open subviews -> Local types, then choose Edit -> Insert... and copy paste in the header source. You might have to click OK a few times.
The script can also aid kernel developers and kernel researchers, since many types documented by the Vergilius Project are not officially documented by Microsoft and not part of the Windows Driver Kit (WDK).