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MichaelPetch wrote:I'd clean it up and do it this way:

Code: Select all

#!/bin/bash

nasm -f bin boot.asm -o boot.bin
gcc -m32 -c -ffreestanding main.c -o main.o
gcc -m32 -c -ffreestanding video.c -o video.o

# Link files to kernel.elf using GCC rather than LD
gcc -m32 -Tlink.ld -fno-PIE -nostartfiles main.o video.o -o kernel.elf

objcopy -R .note -R .comment -S -O binary kernel.elf kernel.bin

# Make disk image size of 1.44MiB floppy
dd if=/dev/zero of=disk.img bs=1024 count=1440

dd if=boot.bin of=disk.img conv=notrunc
dd if=kernel.bin of=disk.img seek=1 conv=notrunc

This should compile each individual file, link them to an executable called kernel.elf and that executable is converted into a binary file call kernel.bin. I also simplify creating a disk image (I chose a nominal floppy disk size of 1.44MiB). Bootloader in first sector and kernel starting in second sector.

[BITS 16]
[ORG 0x7c00]	;First instruction adress

global loader

mov ax, 1003h
mov bx, 0
int 0x10

mov ax, 0x0003  ; 80x25 16color mode
int 0x10		; video interrupt

xor ax, ax ; <---------------------------------------------------------------- ax = 0
mov ss, ax ; <--------------------------------------------------------------- ss = ax = 0
mov sp, 0x7c00 ; <--------------------------------------------------------- stack pointer = 0x7c00

reset_drive:
  mov ah, 0
  int 0x13
  or ah, ah
  jnz reset_drive

  ; load from disk
	xor ax, ax
	mov es, ax
	mov ch, ah
	mov dh, ah
	mov bx, 0x7e00
	mov cl, 0x02
	mov ah, 0x02
	mov al, 0x0A ; 10 (it works with numbers above 5 now)
	int 0x13
	or ah, ah
	jnz reset_drive

more code below but it's irrelevant since this is the only part I changed

MichaelPetch wrote:As I stated in a previous comment the real mode stack code you are asking about looks fine. Can you show us C code with a string that doesn't print properly? Also remember that writing to video memory directly a string of 2000 characters will stop at 2000 and there is no automatic screen scrolling like you'd get with the BIOS. You'd have to code that yourself.