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architecture.md

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Kernel Boot Order:

  1. GRUB

    • Input: None
    • Output: Control passed to Assembly Entry Point
    • Operations:
      • $ Loads the kernel into memory
      • $ Switches the CPU into protected mode
      • $ Jump to _start in ASM

  2. Assembly Entry Point

    • Input: Control from GRUB
    • Output: Control passed to C Entry Point
    • Operations:
      • @ dd multiboot_header: Multiboot header
      • @ label stack_top: Stack top pointer
      • $ proc initialize_stack(): Sets up stack

  3. C Entry Point

    • Input: Control from Assembly Entry Point
    • Output: Control passed to GDT Initialization
    • Operations:
      • $ call Jump to void kmain(void): Begins execution in C

  4. GDT Initialization

    • Input: Control from C Entry Point
    • Output: Control passed to Paging Initialization
    • Operations:
      • @ GDTEntry* gdt_entries: GDT entries array
      • $ void init_gdt(void): Initializes the Global Descriptor Table
        • $ void define_gdt_entries(GDTEntry* gdt_entries): Defines GDT entries
        • $ void setup_descriptors(void): Sets up CODE_SEG and DATA_SEG
        • $ void load_gdt(GDTEntry* gdt_entries): Loads GDT entries into CPU

  5. Paging Initialization

    • Input: Control from GDT Initialization
    • Output: Control passed to IDT Initialization
    • Operations:
      • @ PageDirectory* page_directory: Page directory storage
      • @ PageTable* page_tables: Page tables array
      • $ void init_paging(void): Initializes memory paging
        • $ PageDirectory* allocate_page_directory(void): Allocates memory for page directory
        • $ PageTable* allocate_page_tables(void): Allocates memory for page tables
        • $ void setup_page_directory_entries(PageDirectory* page_directory): Sets up page directory entries
        • $ void setup_page_table_entries(PageTable* page_tables): Sets up page table entries
        • $ void enable_paging(void): Enables paging in processor
        • $ void load_page_directory(PageDirectory* page_directory): Loads page directory into cr3 register

  6. IDT Initialization

    • Input: Control from Paging Initialization
    • Output: Control passed to PIC Initialization
    • Operations:
      • @ IDTEntry* idt_entries: IDT entries array
      • $ void init_idt(void): Initializes the Interrupt Descriptor Table
        • $ void define_idt_entries(IDTEntry* idt_entries): Defines IDT entries
        • $ void setup_interrupt_gate_descriptors(void): Sets up INTERRUPT_GATE descriptors
        • $ void load_idt(IDTEntry* idt_entries): Loads IDT into CPU

  7. PIC Initialization

    • Input: Control from IDT Initialization
    • Output: Control passed to ISR Initialization
    • Operations:
      • $ void init_pic(void): Initializes the Programmable Interrupt Controller
        • $ void remap_pics(void): Remaps PICs to avoid conflicts
        • $ void set_icw(void): Sets ICW1, ICW2, ICW3, and ICW4
        • $ void set_imr(void): Sets IMR to enable/disable interrupts
        • $ void send_eoi(void): Sends EOI command after handling interrupt

  8. ISR Initialization

    • Input: Control from PIC Initialization
    • Output: ISR initialized
    • Operations:
      • @ ISRRoutine* isr_routines: ISR routines array
      • $ void init_isr(void): Initializes the Interrupt Service Routines
        • $ void define_isr_routines(ISRRoutine* isr_routines): Defines ISR routines
        • $ void register_isr_routines(ISRRoutine* isr_routines): Registers ISR routines
        • $ void enable_isr(void): Enables specific hardware interrupts

  9. Other Initializations (Later)

    • Operations:
      • $ 9.1 File System Initialization
      • $ 9.2 Task Scheduler Initialization
      • $ 9.3 Network Driver Initialization
      • $ 9.4 Memory Management Initialization
      • $ 9.5 User Mode Environment Setup
      • $ 9.6 And more...

  10. Main Kernel Loop

    • Operations:
      • $ Continuously checks for and handles system events

Symbol Table

Symbol Description
- Bullet points for operations, variables, and methods/functions
@ Variables
$ Methods/Functions