Files to compile boot loader and compile/link kernel

boot.asm

[org 0x7c00]

; Setup stack
mov bp, 0xffff ; Stack base (bottom)
mov sp, bp	   ; Stack pointer to top of base

mov si, MSG_REAL_MODE
    call print_string

mov si, MSG_LOADING_KERNEL
    call print_string

mov al, 9 ; Tell BIOS to  move 9 sectors after the boot sector
mov bx, kernel_entry ; [0x7e00]
call read_from_disk

; Switch to protected mode
call switch_to_pm

jmp $

; Tell nasm to output 32-bit bytecode
[bits 32]

BEGIN_PM:

mov esi, MSG_PROT_MODE
    call print_string_pm

    ; Disable cursor
    call disable_cursor 

    ; Jump to loaded kernel code
    jmp kernel_entry
    ;jmp $

%include "functions/my_new_functions.asm"

[bits 16]

; Includes
%include "functions/my_functions.asm"
%include "functions/read_from_disk.asm"
%include "functions/switch_to_pm.asm"
%include "functions/my_pm_functions.asm"

MSG_REAL_MODE db "Started in 16-bit Real Mode", 0
MSG_LOADING_KERNEL db "Loading kernel from disk to address 0x7e00",0
MSG_PROT_MODE db "Successfully Switched into 32-bit Protected Mode", 0

; Pad bootsector
times 510-($-$$) db 0
dw 0xaa55

; 0x7c00+512
kernel_entry:
    ; Kernel code will be loaded here  

linker.asm

boot.asm:
    global start
    extern k_main

section .text
start:
    jmp k_main

linker.ld

OUTPUT_FORMAT("binary")
ENTRY("start")

SECTIONS
{
	. = 0x7e00;
	.text :
	{
		linker.o (.text);
		* (.text.startup);
		* (.text*);
		* (.data*);
		* (.rodata*);
	}
}

make.sh

rm -f *.bin *.o
i686-elf-gcc -fno-lto -fno-pie -ffreestanding -c main.c -o main.o -fno-stack-protector -m32

nasm linker.asm -o linker.o -felf32
i686-elf-ld --nmagic --discard-all --strip-all -m elf_i386 -Tlinker.ld linker.o main.o -o kernel.bin

nasm boot.asm -f bin -o boot.bin
cat boot.bin kernel.bin > os_image.bin
truncate os_image.bin -s 10240
qemu-system-x86_64 os_image.bin

Makefile

CC = i686-elf-gcc
LD = i686-elf-ld 
SRC = $(wildcard *.c)
OBJ = $(SRC:.c=.o)
ASMSRC = $(wildcard *.asm)
ASMOBJ = $(ASMSRC:.asm=.o)
CFLAGS = -fno-builtin -ffreestanding -O2 -no-pie -fno-pic -mno-sse
LDFLAGS = --nmagic --discard-all --strip-all -melf_i386 

%.o : %.c
	$(CC) $^ -c -o $@ $(CFLAGS) -m32

%.o : %.asm
	nasm -felf32 $^ -o $@
	

boot.bin: $(ASMOBJ) $(OBJ)
	$(LD) $(OBJ) $(ASMOBJ) $(LDFLAGS) -Tlinker.ld -o boot.bin

clean:
	@rm *.o *.bin