haribytecode/blackpeakos

Purpose and Boot Entry

MyOS is a freestanding 32-bit i386 educational kernel, packaged as a BIOS/GRUB bootable ISO. GRUB loads the kernel entry assembly, which establishes initial CPU state and transfers control to C kernel initialization.

• Boot entry: boot.S

• Kernel linker layouts: link.ld, linker.ld

• GRUB ISO configuration: iso_root/boot/grub/grub.cfg

Kernel Initialization and Console Boundary

The kernel initialization routine brings up descriptor tables, interrupt handling, devices, memory/task infrastructure, and initial execution. Early diagnostics are exposed through VGA text mode and serial UART; fatal failures terminate through the panic path.

• Main kernel control path: kernel.c

• VGA console: console.c, console.h

• Serial and fatal reporting: uart.c, panic.c

CPU Protection and Privilege State

Segmentation and task-state infrastructure define the protected-mode CPU environment. The GDT provides kernel descriptors, while the TSS supports task/privilege-transition state. Small assembly stubs perform CPU instructions that cannot be expressed directly in C.

• GDT setup and load: gdt.c, gdt_flush.s

• Task State Segment: tss.c, tss_flush.s

• Low-level context mechanisms: context.c, context_switch.s

Interrupt and IRQ Dispatch Pipeline

Hardware and CPU events enter assembly interrupt stubs, are normalized into C-level ISR/IRQ dispatch, then routed to device or scheduler handlers. The PIC is configured to remap and acknowledge legacy IRQs, separating CPU exception handling from external hardware interrupts.

• IDT and assembly gates: idt.c, idt_asm.s

• Exception/IRQ dispatch: isr.c, irq.c

• PIC control: pic.c, interrupt.h

Timer, Keyboard, and Device I/O

The PIT timer provides the periodic interrupt source used for preemption. Keyboard IRQ handling translates input for kernel consumption. Hardware register access is centralized around x86 port-I/O primitives, with VGA and UART as primary output devices.

• Timer/preemption source: timer.c, timer.h

• Keyboard driver: keyboard.c, keyboard.h

• Port I/O interface: io.h

Tasks, Threads, and Scheduling

The multitasking subsystem models executable work as tasks and threads, manages CPU context, and selects runnable execution on timer-driven preemption. The scheduler is the control boundary between an IRQ tick and a context switch; task/thread code owns lifecycle and execution-state structures.

• Scheduler policy and dispatch: scheduler.c, scheduler.h

• Task representation/lifecycle: task.c, task.h

• Thread and context state: thread.c, context.c

Memory Management and Image Delivery

The kernel includes basic physical heap/memory management. Paging sources exist, but the stated runtime model does not yet depend on virtual memory. The Makefile produces an ELF kernel and places it into the GRUB ISO tree for QEMU or compatible BIOS virtualization.

• Heap/physical allocation: heap.c, heap.h

• Paging foundation: paging.c, paging.h

• Build artifacts and delivery root: Makefile, iso_root/boot/kernel.elf