old-trainOS/README.md

trainOS

Description

An operating system built around the language "trainscript" which is used to execute all user code in a virtual machine.

Current status:

The vm can execute some code and is able to call native code. Also it leaks memory. A lot of memory.

Todo List

• Fixing Memory Leaks
• Adding support for Modules
• Adding support for Pointer Types
• Adding support for String Type
• Changing malloc magic number to hash value for complete validation.

Guidlines

• Calls to die or die_extra should follow the following scheme: ContextName.ErrorName

Kernel Architecture

The kernel is a simple kernel that does not utilize paging. It has simple interrupt management where an interrupt handler can be registerd for each interrupt.

Bootstrapping

1. Setup 16 kB stack space
2. Clear screen and print boot message
3. Initialize physical memory management (page allocator)
4. Initialize interrupts
5. Enable hardware interrupts
6. Initialize timer
7. Initialize C++ support
8. Register status bar timer callback
9. Start virtual machine (and run OS)
10. Disable hardware interrupts
11. Print stop message

Memory Allocation

The kernel features a simple malloc structure that allocates memor between 0x400000 and 0x800000 (4 MB heap space).

The allocator can be configured to "secure" its allocation list with a magic number by defining USE_MAGIC_SECURED_MALLOC in config.h.

It also features a surveillance mode that logs all allocations / frees. It can be enabled by defining USE_VERBOSE_MALLOC and USE_VERBOSE_FREE in config.h.

Interrupt Mapping

Number	Interrupt
0x00 - 0x1F	System Interrupts
0x20 - 0x27	IRQ0 - IRQ7
0x28 - 0x2F	IRQ8 - IRQ15

OS Architecture

To be done.