Cafe OS

From WiiUBrew
Revision as of 22:41, 25 September 2015 by Marionumber1 (talk | contribs) (Architecture: Link to main articles for Cafe OS kernel and loader)
Jump to: navigation, search

Cafe OS is the operating system running on the PowerPC in Wii U mode. It consists of the Cafe OS kernel, the executable loader, and system libraries. Unlike on the Wii, where games ran with full hardware access, Wii U applications run under the supervision of the kernel, isolating them from each other. All applications are modified ELFs, as are the libraries themselves, and applications dynamically link with them to gain access to OS services. Cafe OS also contains a few system processes, like the home menu and error handler.

Architecture

Kernel

Main article: Cafe_OS_Kernel

The kernel runs in supervisor mode on the PowerPC, and performs the basic tasks of a microkernel. It is responsible for process isolation, memory management, and interrupt dispatching, as well as communication with IOSU. Cafe OS applications run as user mode processes, with separate address spaces and W^X memory protection. The kernel provides basic syscalls for running processes.

Loader

Main article: Loader

The loader is responsible for loading RPL formatted libraries and executables into memory. It is a standard ELF executable named loader.elf. It includes a statically linked copy of zlib, probably for decompressing sections of RPL files.

Libraries

Cafe OS applications dynamically link with system libraries to get access to OS services. These OS services include memory management, graphics, audio, and controller input. All libraries are RPL files, a modification of the standard ELF format with compressed sections and more Windows-like dynamic linking. The main system libraries are listed below, with some having their own pages of documentation:

Virtual Memory Map

  • 0x01000000 - 0x01800000 Loader and system libraries
  • 0x0??????? - 0x10000000 App executable and libraries (start varies, but end is always 0x10000000)
  • 0x10000000 - 0x50000000 Application/library data area (may be smaller)
  • 0xa0000000 - 0xe0000000 Overlay of application memory (used by loader?)
  • 0xe0000000 - 0xe4000000 Some sort of hardware communication area
  • 0xefe00000 - 0xefe80000 Loader data area (only mapped when running loader)
  • 0xf4000000 - 0xf6000000 MEM1
  • 0xf6000000 - 0xf6800000 Unknown
  • 0xf8000000 - 0xfb000000 Read-only shared data (system fonts mostly)
  • 0xfc000000 - 0xfc0c0000 Processor Interface
  • 0xfc200000 - 0xfc280000 GX2 TCL registers
  • 0xfc280000 - 0xfc2a0000 DSP registers
  • 0xfc2a0000 - 0xfc2c0000 GX2 FIFO space? (Radeon PKT3 sent here)
  • 0xfc320000 - 0xfd000000 Espresso OTP (and other stuff?)
  • 0xfd000000 - 0xfd?????? Latte registers
  • 0xfd040250 - 0xfd046c00 I2C registers
  • 0xfd046e00 - 0xfd060520 AI registers?
  • 0xff200000 - 0xff280000 Kernel heap
  • 0xffe00000 - 0xfff20000 Kernel ancast image
  • 0xffffffe0(?) - 0xfffffffc(?) Per-thread data (e.g. pointer to thread descriptor and thread queue)