OSDev.org

Code: Select all

MBOOT_PAGE_ALIGN    equ 1<<0    ; Load kernel and modules on a page boundary
MBOOT_MEM_INFO      equ 1<<1    ; Provide your kernel with memory info
MBOOT_HEADER_MAGIC  equ 0x1BADB002 ; Multiboot Magic value
MBOOT_HEADER_FLAGS  equ MBOOT_PAGE_ALIGN | MBOOT_MEM_INFO
MBOOT_CHECKSUM      equ -(MBOOT_HEADER_MAGIC + MBOOT_HEADER_FLAGS)

[BITS 32]
global start
start:
    mov esp, _sys_stack
    mov ebx, mboot
    push ebx
    jmp stublet

ALIGN 4  ; Ensure proper alignment for the Multiboot header

global mboot
extern code
extern bss
extern end

mboot:
    dd  MBOOT_HEADER_MAGIC      ; GRUB will search for this value on each
                                ; 4-byte boundary in your kernel file
    dd  MBOOT_HEADER_FLAGS      ; How GRUB should load your file / settings
    dd  MBOOT_CHECKSUM          ; To ensure that the above values are correct
    
    dd  mboot                   ; Location of this descriptor
    dd  code                    ; Start of kernel '.text' (code) section.
    dd  bss                     ; End of kernel '.data' section.
    dd  end                     ; End of kernel.
    dd  start                   ; Kernel entry point (initial EIP).

extern kernel_main
stublet:
    call kernel_main
    jmp $

Code: Select all

#ifndef _MULTIBOOT_H
#define _MULTIBOOT_H

#define MULTIBOOT_FLAG_MEM 0x001
#define MULTIBOOT_FLAG_DEVICE 0x002
#define MULTIBOOT_FLAG_CMDLINE 0x004
#define MULTIBOOT_FLAG_MODS 0x008
#define MULTIBOOT_FLAG_AOUT 0x010
#define MULTIBOOT_FLAG_ELF 0x020
#define MULTIBOOT_FLAG_MMAP 0x040
#define MULTIBOOT_FLAG_CONFIG 0x080
#define MULTIBOOT_FLAG_LOADER 0x100
#define MULTIBOOT_FLAG_APM 0x200
#define MULTIBOOT_FLAG_VBE 0x400

#include <stdint.h>

typedef struct multiboot_info_t {
	uint32_t flags;
	uint32_t mem_lower;
	uint32_t mem_upper;
	uint32_t boot_device;
	uint32_t cmdline;
	uint32_t mods_count;
	uint32_t mods_addr;
	uint32_t num;
	uint32_t size;
	uint32_t addr;
	uint32_t shndx;
	uint32_t mmap_length;
	uint32_t mmap_addr;
	uint32_t drives_length;
	uint32_t drives_addr;
	uint32_t config_table;
	uint32_t boot_loader_name;
	uint32_t apm_table;
	uint32_t vbe_control_info;
	uint32_t vbe_mode_info;
	uint32_t vbe_mode;
	uint32_t vbe_interface_seg;
	uint32_t vbe_interface_off;
	uint32_t vbe_interface_len;
} __attribute__((packed)) multiboot_info_t;

#endif

Code: Select all

#include "../include/kernel.h"

void kernel_main(multiboot_info_t *mbi)
{
	terminal_init();
	qemu_init_debug();
	gdt_init();
	idt_init();
	timer_init(50);
	keyboard_init();
	get_cpu_info();

	uint32_t mbi_flags = mbi->flags;
	uint32_t mbi_lower = mbi->mem_lower;
	uint32_t mbi_upper = mbi->mem_upper;

	printf("flags: 0x%x\n", mbi_flags);
	printf("lower memory: 0x%u kb\n",
	       mbi_lower); // Use %u for unsigned integers
	printf("upper memory: %u kb\n",
	       mbi_upper); // Use %u for unsigned integers

	printf("mmap_length: %u\n", mbi->mmap_length);
	printf("mmap_addr: %u\n", mbi->mmap_addr);

	// set_mode(320, 200, 8);
	// clear_screen_withcolor(0x04);
}

Code: Select all

start:
  mov esp, _sys_stack ; I do hope that symbol is the upper end of the stack!
  push ebx
  push eax
  call kernel_main
.spin:
  cli
  hlt
  jmp .spin