[bits 16] [org 0x7c00] mov ax, 0x2401 int 0x15 mov ax, 0x3 int 0x10 mov [disk], dl mov ah, 0x2 mov al, 6 mov ch, 0 mov dh, 0 mov cl, 2 mov dl, [disk] mov bx, 0x7e00 int 0x13 cli lgdt [gdt_desc] mov eax, cr0 or eax, 1 mov cr0, eax jmp 0x8:protected_mode gdt: dq 0 dw 0xffff, 0 db 0, 0x9a, 0xcf, 0 dw 0xffff, 0 db 0, 0x92, 0xcf, 0 gdt_desc: dw gdt_desc - gdt - 1 dd gdt [bits 32] protected_mode: mov ax, 0x10 mov ds, ax mov es, ax mov fs, ax mov gs, ax mov ss, ax mov esp, 0x7c00 jmp 0x7e00 disk: db 0 times 510-($-$$) db 0 dw 0xaa55 #define VIDEO_MEMORY 0xb8000 #define WHITE_ON_BLACK 0x0f void clear_screen() { char* video_memory = (char*) VIDEO_MEMORY; for (int i = 0; i < 80 * 25 * 2; i += 2) { video_memory[i] = ' '; video_memory[i+1] = WHITE_ON_BLACK; } } void print_string(const char* str) { char* video_memory = (char*) VIDEO_MEMORY; while (*str) { *video_memory++ = *str++; *video_memory++ = WHITE_ON_BLACK; } } void kernel_main() { clear_screen(); print_string("Welcome to PhoenixOS!"); } ENTRY(protected_mode) SECTIONS { . = 0x7e00; .text : { *(.text) } .data : { *(.data) } .bss : { *(.bss) } } CC = gcc LD = ld ASM = nasm QEMU = qemu-system-x86_64 all: os.iso os.iso: kernel.bin boot.bin cat boot.bin kernel.bin > os.iso boot.bin: boot/boot.asm $(ASM) -f bin boot/boot.asm -o boot.bin kernel.bin: kernel/kernel.o $(LD) -T linker.ld -o kernel.bin kernel/kernel.o --oformat binary kernel/kernel.o: kernel/kernel.c $(CC) -c kernel/kernel.c -o kernel/kernel.o -ffreestanding -nostdlib run: os.iso $(QEMU) -drive format=raw,file=os.iso clean: rm -f *.bin *.o *.iso kernel/*.o