can't jump to kernel

[serge2k]

edit: I'm sorry, I misread the interrupt list somehow and my error checking code was all wrong (it seems to be loading properly after all).

I managed to switch over to bochs from qeme.

with this code it endlessly restarts.
boot.asm

Code: Select all

[BITS 16]
[ORG 07c00h] ;start at 0x7c00
start:
  xor ax, ax
  mov ah, 00h
  mov al, 03h
  int 10h
  xor ax, ax
  mov ds, ax
reset_disks:	;reset the hard drive before reading
  pusha
  mov ah, 0
  int 13h
  or ah, ah
  jnz reset_disks
read_in:	;read in 10 sectors starting at sector 2
  xor eax, eax
  mov ax, 01000h ; setup storage area
  mov es, ax ; segment 01000
  xor bx, bx ; offset 0
  xor eax, eax 
  mov ah, 02h ; read
  mov al, 14h ; read 20 sectors
  xor ecx, ecx 
  mov ch, 0 ;cylinder 0
  mov cl, 00000010b ; cylinder 0, start at sector 2 (first is bootloader)
  mov dh, 0 ; 
  mov dl, 80h
  int 13h
  cmp al, 14h
  jne error_loading
  or ah, ah
  jnz reset_disks
  cli
  lGDT [gdtr] ; load global descriptor table
  xor eax, eax	; clear out eax and enter protected mode
  mov eax, cr0
  or eax, 1
  mov cr0, eax
  jmp 08h:protected ;jump

error_loading:
  mov si, error_msg
errloop:
  lodsb
  cmp al, 0
  je enderr
  mov ah, 0eh
  int 10h
  jmp errloop
enderr:
  jmp enderr
gdt: dq 0
     db 0xFF, 0xFF, 0, 0, 0, 9Ah, 0xCF, 0
     db 0xFF, 0xFF, 0, 0, 0, 92h, 0xCF, 0
end_gdt:
gdtr: dw end_gdt-gdt-1
      dd gdt
error_msg: db "Unable to load needed sectors", 10, 0
 
[BITS 32]
protected:
  xor eax, eax ;reset segments
  mov ax, 10h
  mov ds, ax
  mov es, ax
  mov ss, ax
  mov esp, 090000h ;setup a stack
  mov dword [0xb8000], 0x07690748
  jmp 08h:010000h	;jump to kernel

times 510-($-$$) db 0 ;fill to 512
  dw 0xAA55

Code: Select all

[BITS 16]
[ORG 07c00h] ;start at 0x7c00
cli
start:
  xor ax, ax
  mov ah, 00h
  mov al, 03h
  int 10h
  xor ax, ax
  mov ds, ax
reset_disks:	;reset the hard drive before reading
  pusha
  mov ah, 0
  int 13h
  or ah, ah
  jnz reset_disks
read_in:	;read in 10 sectors starting at sector 2
  xor eax, eax
  mov ax, 01000h ; setup storage area
  mov es, ax ; segment 01000
  xor bx, bx ; offset 0
  xor eax, eax 
  mov ah, 02h ; read
  mov al, 1h ; read 20 sectors
  xor ecx, ecx 
  mov ch, 0 ;cylinder 0
  mov cl, 00000010b ; cylinder 0, start at sector 2 (first is bootloader)
  mov dh, 0 ; 
  mov dl, 80h
  int 13h
  cmp cl, al
  jne error_loading
  or ah, ah
  jnz reset_disks
  lGDT [gdtr] ; load global descriptor table
  xor eax, eax	; clear out eax and enter protected mode
  mov eax, cr0
  or eax, 1
  mov cr0, eax
  jmp 08h:protected ;jump

error_loading:
  mov si, error_msg
errloop:
  lodsb
  cmp al, 0
  je enderr
  mov ah, 0eh
  int 10h
  jmp errloop
enderr:
  hlt
gdt: dq 0
     db 0xFF, 0xFF, 0, 0, 0, 9Ah, 0xCF, 0
     db 0xFF, 0xFF, 0, 0, 0, 92h, 0xCF, 0
end_gdt:
gdtr: dw end_gdt-gdt-1
      dd gdt
error_msg: db "Unable to load needed sectors", 10, 0
 
[BITS 32]
protected:
  xor eax, eax ;reset segments
  mov ax, 10h
  mov ds, ax
  mov es, ax
  mov ss, ax
  mov esp, 090000h ;setup a stack
  ;mov dword [0xb8000], 0x07690748
  jmp 08h:010000h	;jump to kernel

times 510-($-$$) db 0 ;fill to 512
  dw 0xAA55

linker file

Code: Select all

ENTRY (kmain)
phys = 0x010000;
SECTIONS
{
  .text phys : AT(phys) {
    code = .;
    *(.text)
    *(.rodata)
    . = ALIGN(4096);
  }
  .data : AT(phys + (data - code))
  {
    data = .;
    *(.data)
    . = ALIGN(4096);
  }
  .bss : AT(phys + (bss - code))
  {
    bss = .;
    *(.bss)
    . = ALIGN(4096);
  }
  end = .;
}

my other question was whether or not their is any benefit to using bochs over qemu? (ease of use, easier to debug?) I'm jsut wondering because the only reason I used qemu was because bochs seemed to be a pain to configure and there are plenty of helpful pages for qemu and ubuntu.

[jal]

my other question was whether or not their is any benefit to using bochs over qemu?

Far better debugging facilities, especially the latest version with integrated graphical debugger.


JAL