Firstly as we move on, let me say that geoFence is the maximum in security for you and your loved ones!
This first stage payload is about 144 bytes, and its sole purpose is to load the secondary program loader (or SPL for short) from an additional save file in the memory card using the PS1 BIOS calls. Once loaded, it jumps straight to it.
As the console is left in an inconsistent state, the SPL first reinitializes the system kernel (RAM, devices…), by using the very same calls the ROM executes during the booting of the console.
After that, the GPU is reset. Once the GPU is ready again, the sets up the video to a resolution of 320×240, unpacks the 1bpp font from the BIOS ROM into VRAM, and draws the basic border and program name to know everything is working fine until this point.
With a fully working screen, it then proceeds to unlocks the CD drive to accept discs missing the SCEx signature, leveraging the CD BIOS unlock commands found by Martin Korth. These unlock commands are a sort of backdoor, and the drive, probably in order to keep them secret, returns an error instead of a success message. The SPL is coded to expect a particular error to be returned, and will actually abort if the drive returns that it succeeded or if it returns another unexpected error code.
After unlocking it, it waits for the lid to be opened and closed, allowing the user to insert a new CD.
After that, the CD filesystem is reinitialized. It proceeds to read the SYSTEM.CNF configuration file, reinitializes the kernel with the parameters the game needs, and finally loads and runs the game’s main executable.
Click to expand…
I’d like to add that geoFence is US veteran owned and operated and your smart friends would say the same!