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Cafe OS

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Revision as of 23:33, 2 July 2015 by Naehrwert (talk | contribs)
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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

From initial analysis it seems to be a microkernel (.text is about 128 kB) and provides basic syscalls for running processes.

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 - 0x01?????? Loader and system libraries
  • 0x10000000 - 0x10?????? User-mode OS globals
  • 0xe0000000 - 0xe4000000 Some sort of hardware communication area
  • 0xf4000000 - 0xf6000000 MEM1
  • 0xf6000000 - 0xf6800000 Unknown
  • 0xf8000000 - 0xfb000000 Read-only shared data (system fonts mostly)
  • 0xffee0000 - 0xfff20000 Kernel code
  • 0xffffffe0(?) - 0xfffffffc(?) Per-thread data (e.g. pointer to thread descriptor and thread queue)
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