Я пытаюсь создать свою собственную ОС и мне нужна помощь с моим кодом. Это моеbootloader.asm:

[ORG 0x7c00]

start:
    cli
    xor ax, ax
    mov ds, ax
    mov ss, ax
    mov es, ax
    mov [BOOT_DRIVE], dl
    mov bp, 0x8000
    mov sp, bp
    mov bx, 0x9000
    mov dh, 5
    mov dl, [BOOT_DRIVE]
    call load_kernel
    call enable_A20
    call graphics_mode
    lgdt [gdtr]
    mov eax, cr0
    or al, 1
    mov cr0, eax
    jmp CODE_SEG:init_pm

[bits 32]
init_pm:
    mov ax, DATA_SEG
    mov ds, ax
    mov ss, ax
    mov es, ax
    mov fs, ax
    mov gs, ax

    mov ebp, 0x90000
    mov esp, ebp

    jmp 0x9000

[BITS 16]
graphics_mode:
    mov ax, 0013h
    int 10h
    ret

load_kernel:
                        ; load DH sectors to ES:BX from drive DL
    push dx             ; Store DX on stack so later we can recall
                        ; how many sectors were request to be read ,
                        ; even if it is altered in the meantime
    mov ah , 0x02       ; BIOS read sector function
    mov al , dh         ; Read DH sectors
    mov ch , 0x00       ; Select cylinder 0
    mov dh , 0x00       ; Select head 0
    mov cl , 0x02       ; Start reading from second sector ( i.e.
                        ; after the boot sector )
    int 0x13            ; BIOS interrupt
    jc disk_error       ; Jump if error ( i.e. carry flag set )
    pop dx              ; Restore DX from the stack
    cmp dh , al         ; if AL ( sectors read ) != DH ( sectors expected )
    jne disk_error      ; display error message
    ret
disk_error :
    mov bx , ERROR_MSG
    call print_string
    hlt

[bits 32]
    ; prints a null - terminated string pointed to by EDX
print_string :
    pusha
    mov edx , VIDEO_MEMORY ; Set edx to the start of vid mem.
print_string_loop :
    mov al , [ ebx ] ; Store the char at EBX in AL
    mov ah , WHITE_ON_BLACK ; Store the attributes in AH
    cmp al , 0 ; if (al == 0) , at end of string , so
    je print_string_done ; jump to done
    mov [edx] , ax ; Store char and attributes at current
        ; character cell.
    add ebx , 1 ; Increment EBX to the next char in string.
    add edx , 2 ; Move to next character cell in vid mem.
    jmp print_string_loop ; loop around to print the next char.
print_string_done :
    popa
    ret ; Return from the function

[bits 16]
; Variables 
ERROR_MSG db "Error!" , 0
BOOT_DRIVE: db 0
VIDEO_MEMORY equ 0xb8000
WHITE_ON_BLACK equ 0x0f

%include "a20.inc"
%include "gdt.inc"

times 510-($-$) db 0
db 0x55
db 0xAA

Я собираю это с этим:

nasm -f bin -o boot.bin bootloader.asm

Этоkernel.c:

call_main(){main();}
void main(){}

Я собираю это с этим:

gcc -ffreestanding -o kernel.bin kernel.c

а потом:

cat boot.bin kernel.bin > os.bin

Я хочу знать, что я делаю неправильно, потому что, когда я проверяю сQEMU это не работает Может кто-нибудь дать несколько советов по улучшениюkernel.c так что мне не нужно использовать функцию call_main ()?

При тестировании я использую:

qemu-system-i386 -kernel os.bin

Мои другие файлы

a20.inc:

   enable_A20:
call check_a20
cmp ax, 1
je enabled
call a20_bios
call check_a20
cmp ax, 1
je enabled
call a20_keyboard
call check_a20
cmp ax, 1
je enabled
call a20_fast
call check_a20
cmp ax, 1
je enabled
mov bx, [ERROR]
call print_string
   enabled:
ret


  check_a20:
pushf
push ds
push es
push di
push si

cli

xor ax, ax ; ax = 0
mov es, ax

not ax ; ax = 0xFFFF
mov ds, ax

mov di, 0x0500
mov si, 0x0510

mov al, byte [es:di]
push ax

mov al, byte [ds:si]
push ax

mov byte [es:di], 0x00
mov byte [ds:si], 0xFF

cmp byte [es:di], 0xFF

pop ax
mov byte [ds:si], al

pop ax
mov byte [es:di], al

mov ax, 0
je check_a20__exit

mov ax, 1

 check_a20__exit:
pop si
pop di
pop es
pop ds
popf

ret

    a20_bios:
mov ax, 0x2401
int 0x15
ret

    a20_fast:
in al, 0x92
or al, 2
out 0x92, al
ret

    [bits 32]
    [section .text]

    a20_keyboard:
    cli

    call    a20wait
    mov     al,0xAD
    out     0x64,al

    call    a20wait
    mov     al,0xD0
    out     0x64,al

    call    a20wait2
    in      al,0x60
    push    eax

    call    a20wait
    mov     al,0xD1
    out     0x64,al

    call    a20wait
    pop     eax
    or      al,2
    out     0x60,al

    call    a20wait
    mov     al,0xAE
    out     0x64,al

    call    a20wait
    sti
    ret

    a20wait:
    in      al,0x64
    test    al,2
    jnz     a20wait
    ret


    a20wait2:
    in      al,0x64
    test    al,1
    jz      a20wait2
    ret

gdt.inc:

 gdt_start:
dd 0                ; null descriptor--just fill 8 bytes    dd 0 

 gdt_code:
dw 0FFFFh           ; limit low
dw 0                ; base low
db 0                ; base middle
db 10011010b            ; access
db 11001111b            ; granularity
db 0                ; base high

 gdt_data:
dw 0FFFFh           ; limit low (Same as code)
dw 0                ; base low
db 0                ; base middle
db 10010010b            ; access
db 11001111b            ; granularity
db 0                ; base high
  end_of_gdt:

  gdtr: 
dw end_of_gdt - gdt_start - 1   ; limit (Size of GDT)
dd gdt_start            ; base of GDT

   CODE_SEG equ gdt_code - gdt_start
   DATA_SEG equ gdt_data - gdt_start