kernel - Boot entry point

Source: kernel/kernel/kernel.c

This is the top-level kernel module. It is called directly by the architecture-specific boot stub (boot.S) immediately after the CPU is placed in protected mode and a valid stack has been set up.

Functions

kernel_main 

void kernel_main(uint32_t magic, multiboot2_info_t *mbi);

The C entry point of the kernel. Called from boot.S with the Multiboot 2 magic value in magic and a pointer to the Multiboot 2 information structure in mbi.

Initialisation order:

  1. terminal_initialize() - clear the VGA text buffer and set up the cursor.
  2. init_serial(COM1) - configure the UART at 38 400 baud.
  3. init_descriptor_tables() - load the GDT and IDT, register ISR stubs.
  4. init_debug_handlers() - install INT 1 / INT 3 fallback handlers.
  5. pmm_init(magic, mbi) - build the physical frame bitmap from the Multiboot 2 memory map.
  6. paging_init() - identity-map the first 8 MiB and enable CR0.PG.
  7. heap_init() - map the heap region and set up the free-list allocator.
  8. vesa_init(mbi) - locate the Multiboot 2 framebuffer tag and populate vesa_fb_t.
  9. vesa_tty_init() - map the framebuffer and start the bitmap-font renderer.
  10. init_timer(50) - program the PIT for 50 Hz and enable interrupts.
  11. kernel_post_boot() - run the post-boot heartbeat loop.

kernel_post_boot 

void kernel_post_boot(void);

Post-boot heartbeat. Sleeps for 50 ticks (≈ 1 second at 50 Hz) ten times, printing the current tick count to both the VGA terminal and the serial port on each iteration.

This serves two purposes:

  • Confirms that the PIT interrupt (IRQ 0) is firing correctly after full initialisation.
  • Provides named breakpoint targets (kernel_post_boot) for the GDB boot test suite.

The function is intentionally non-static so that GDB can resolve its symbol by name.