TOSEMU An emulated environment to TOS applications. Copyright (C) 2014 Johan Thelin e8johan@gmail.com

Introduction

TOSEMU aims to provide an emulated environment for executing TOS applications. Instead of emulating a complete TOS-compatible machine, operating system calls are intercepted and emulated on the host platform. The end result will be TOS applications running as an integrated part of the host system.

TOSEMU can be seen as a mix of 68kemu, which allows 68k applications to be executed in a TOS environment on another CPU platform, and wine, which lets Windows applications execute using a system API translation laer on the CPU platform they where meant for. TOSEMU executes 68k applications on non-68k CPUs, and provides an OS wrapper layer, translating TOS calls to system calls native to the host operating system.

Building

TOSEMU is self contained for now, so a simple make should do it. The resulting binary can be found in the bin directory.

The make clean target produces a clean source tree.

Usage

TOSEMU takes a single command line argument, the location of a TOS application. It is also possible to use TOSEMU with the binfmt support in the Linux kernel. I use the following line to enable this:

echo ':tos:M::\x60\x1a:\xff\xff:/path/to/binary/tosemu:' | sudo tee /proc/sys/fs/binfmt_misc/register

This will allow you to execute TOS binaries as if they where native.

Road Map

The first stage will be to get a very basic TOS application to execute using TOSEMU. Having achieved this, more and more complex apps will be supported by extending the available system calls.

When basic applications are useable, a server/client architecture enabling intra-app communication as well as desktop accessory applications will be implemented.

Tests

The tests subdirectory contains test applications used during the development of tosemu. The tests are compiled with the m68k-atari-mint cross-tools built by Vincent Rivière. Please visit the following web site for more information:

http://vincent.riviere.free.fr/soft/m68k-atari-mint/

To build the tests, simply run make tests, this will result in a set of binaries named test-* in the tests sub-directory.

Hacking

Tracing

The config.h file contains defines for enabling extremely verbose trace messages. This is a great tool when debugging a subsystem, e.g. bios or aes.

There is no dependecy to config.h, so a clean build is needed for changes to take effect.

Endianess

As the m68k is a big endian architecture, while the current development architecture, x86, is little endian, conversion is sometimes needed. However, in most cases, it is not.

When interacting with the CPU through the m68k_read_*, m68k_write_*, pop_*, peek_*, push_*, all values are expected to be in host endianess, i.e. no conversion is necessary. When interacting directly with the TOS memory, i.e. manipulating a memory area such as te->appmem, endianess is a factor. Here, the functions endianize_16 and endianize_32 help with the conversion. By always using these methods, it will be possible to run tosemu on host systems that are either big or little endian.

Variable Scope

In order to provide abstraction and separation of namespaces, different subsystems are separated into different code modules. Header files ending with _p.h are local to such a namespace, i.e. gemdos_p.h is local to GEMDOS. Depending on the complexity of the subsystems, further subdivision is possible, i.e. GEMDOS is split into multiple modules while BIOS is not.

Licensing

TOSEMU is available under a GPLv2 license. Please refer to the source code and the COPYING file for further details.

Additional Licenses

TOSEMU depends on other components available under other licenses than GPLv2. These are listed below:

The contents of the Musashi subdirectory and m68kconf.h, derived from https://github.com/kstenerud/Musashi, is subject to the following license:

MUSASHI Version 3.4

A portable Motorola M680x0 processor emulation engine. Copyright 1998-2001 Karl Stenerud. All rights reserved.

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.