Architecture template

Summary

The arch package
Architecture informations
Registers
Instructions
BIOS

The “arch” package

LibPyOSDev provides a package named arch. It provides module templates to help you add support for your architecture.

infos: informations about the architecture
registers: representation of the architecture CPU registers
instructions: architecture CPU instruction set
bios: representation of the architecture BIOS (if supported) and wrappers to its functions

Architecture informations

The arch.infos module contains the ArchitectureInfos class, used to represent architectures. It is defined as described below:

ArchitectureInfos(
    name: str,
    bits: int,
    max_mem: int,
    registers: TInstr,
    instructions: TRegs,
    bios: BIOS
)

The name parameter is the name of the architecture.
The bits parameter is the size of a word on the architecture (e.g. 16, 32, 64, …).
The max_men parameter is the maximum amount of RAM that can be handled by the architecture.
The registers parameter represents to the architecture registers.
The instructions parameter represents the architecture instructions.
The bios parameter represents the architecture BIOS (None if it is not supported)

The __repr__() method returns the following text:

<Architecture NAME (BITS-bit) max memory: MAX_MEM>

Registers

The arch.registers module contains a generic class named RegistersArch to regroup the architecture CPU registers.

Instructions

The arch.instructions module contains two classes: GenericInstruction and ArchInstructions. The first one represents a specific instruction. The second one regroups the instances of GenericInstruction.

GenericInstruction(
    mnemonic: str,
    operand_count: int
)

The mnemonic parameter represents the name of the instruction (e.g. mov).
The operand_count parameter represents the number of operands that is required (e.g. 2).

When an instance of this class is called, it generates the corresponding Assembly code using the emit() function, called automatically by __call__().

ArchInstructions has the link_program() method, to tell the instructions in which program they must emit their code.

BIOS

The arch.bios module contains the BIOS class, which represents the BIOS of the architecture. This class uses a dictionnary named interrupt_table

interrupt number: interrupt wrapper

and a function named interrupt():

interrupt(
    intno: int,
    *args
)

The intno parameter is the number of the interrupt (not the real number but the number defined in the BIOS class). The args parameter is the values needed by the interrupt. They must be given in order and are moved to registers.