OSDever Kernel Error with NASM

[ChosenOreo]

I followed the kernel tutorial at http://www.osdever.net/bkerndev/Docs/basickernel.htm, and I recieved the two errors:

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start.asm:20: error: symbol 'MULTIBOOT_HEADER_MAGIC' undefined
start.asm:24: error: symbol 'MULTIBOOT_HEADER_MAGIC' undefined

My Assembly code is as follows:

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; This is the kernel's entry point. We could either call main here,
; or we can use this to setup the stack or other nice stuff, like
; perhaps setting up the GDT and segments. Please note that interrupts
; are disabled at this point: More on interrupts later!
[BITS 32]
global start
start:
    mov esp, sys_stack     ; This points the stack to our new stack area
    jmp stublet

; This part MUST be 4byte aligned, so we solve that issue using 'ALIGN 4'
ALIGN 4
mboot:
    ; Multiboot macros to make a few lines later more readable
    MULTIBOOT_PAGE_ALIGN	equ 1<<0
    MULTIBOOT_MEMORY_INFO	equ 1<<1
    MULTIBOOT_AOUT_KLUDGE	equ 1<<16
    MULTIBOOT_HEADER_MAGIC	equ 0x1BADB002
    MULTIBOOT_HEADER_FLAGS	equ MULTIBOOT_PAGE_ALIGN | MULTIBOOT_MEMORY_INFO | MULTIBOOT_AOUT_KLUDGE
    MULTIBOOT_CHECKSUM	equ -(MULTIBOOT_HEADER_MAGIC + MULTIBOOT_HEADER_FLAGS)
    EXTERN code, bss, end

    ; This is the GRUB Multiboot header. A boot signature
    dd MULTIBOOT_HEADER_MAGIC
    dd MULTIBOOT_HEADER_FLAGS
    dd MULTIBOOT_CHECKSUM
    
    ; AOUT kludge - must be physical addresses. Make a note of these:
    ; The linker script fills in the data for these ones!
    dd mboot
    dd code
    dd bss
    dd end
    dd start

; This is an endless loop here. Make a note of this: Later on, we
; will insert an 'extern _main', followed by 'call _main', right
; before the 'jmp $'.
stublet:
    jmp $


; Shortly we will add code for loading the GDT right here!


; In just a few pages in this tutorial, we will add our Interrupt
; Service Routines (ISRs) right here!



; Here is the definition of our BSS section. Right now, we'll use
; it just to store the stack. Remember that a stack actually grows
; downwards, so we declare the size of the data before declaring
; the identifier '_sys_stack'
SECTION .bss
    resb 8192               ; This reserves 8KBytes of memory here
sys_stack:

Any Help?

-ChosenOreo

[bluemoon]

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nasm -felf -o a.o a.nasm

I copy&paste exactly your code and see no error. I'm using nasm on mac, NASM version 2.09.02 compiled on Sep 17 2010
What's your nasm version?

[ChosenOreo]

I'm using NASM on Xubuntu 11.04 Natty Narwhal

My version is 2.09.04 - Compiled Nov 26 2010

I compiled it with:

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nasm -f aout -o start.o start.asm

[Brendan]

Hi,

I can't see a problem, and because bluemoon didn't have a problem either it makes me wonder if the problem can't be seen.

For example, sometimes when you copy & paste from a web page you get strange white-space characters (like the "non-breaking space" character, and the '\r' linefeed character) and (especially if your text editor supports Unicode) you end up with the strange white-space characters in your source code; and some tools don't like them.


Cheers,

Brendan

[ChosenOreo]

I typed it letter by letter... I wonder if I missed something. I'll try copying the code over, and I'll see if it works!

[Chandra]

I typed it letter by letter...

which makes me guess that you mistyped the macro MULTIBOOT_HEADER_MAGIC. All you have to do now is to copy and paste the whole code and see if that works

[ChosenOreo]

Nope, same error...
What is going on...

[neon]

bah, just replace MULTIBOOT_HEADER_MAGIC on lines 20 and 24 with 0x1BADB002....And dont copy and paste anymore. Alternatively use a %define.

[Brendan]

Hi,

Nope, same error...
What is going on...

I cut & pasted it and assembled it "as is" with no errors; using NASM 2.09.04 under Gentoo, and "nasm -f aout -o start.o start.asm".

Maybe your makefile is assembling an old/different version or something.


Cheers,

Brendan