"Incredible trick": a girl runs modern Linux on Windows 95

New “hack” for Windows 9x: WSL9x

An enthusiast named Hailey presented her latest project – Windows 9x Subsystem for Linux (WSL9x), which she called “one of the greatest hacks ever.”

What is it?
WSL9x allows running the Linux 6.19 kernel directly on Windows 9x systems. Users are given the same capabilities as in modern versions of WSL, but without a graphical interface.

The system consists of three key components:

1. The Linux kernel – modified to call Windows 9x APIs instead of standard POSIX calls.

2. A VxD driver – a virtual device that initializes WSL9x and handles user‑space events, translating them into Linux kernel calls.

3. The WSL client – a 16‑bit DOS application that passes command‑line input as a TTY device to the kernel.

How does the VxD work?
Because Win9x architecture does not support a full interrupt descriptor table, a normal Linux system call (`int 0x80`) cannot be caught directly.

Instead, WSL9x uses a General Protection Fault (GPF) handler. When GPF catches an `int 0x80` instruction, it:

1. Moves the instruction pointer as if the interrupt succeeded.

2. Passes the system call to the Linux kernel.

Thus the Linux kernel receives the necessary system requests despite Win9x limitations.

Security and stability considerations
- The Linux kernel in WSL9x runs with the same level‑0 processor privileges as the Windows kernel.
- This increases the risk of shared security threats: if one system fails, the other also stops functioning.

In short: WSL9x is an experimental layer that allows running a Linux kernel on old Windows 9x without graphics, using GPF and VxD tricks. Users gain access to powerful Linux features but must be aware of increased stability and security risks.