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Getting error in Hellow World Kernel: Error 13: Invalid or unsupported executable for

I was trying to make a hello world kernel as follows:
kernel.asm

Code:

;States that the code is a 32 bit code

[BITS 32]

[global _start]



;Calls an external C function os_main.

[extern os_main]



_start:

        call os_main



;Turns off interrupts

cli



;Halts the CPU

hlt

I compiled this code as follows:
nasm -f aout kernel.asm -o kernel_a.o

It worked fine.
Then I wrote this file:
kernel.h

Code:

#ifndef _KERNEL_H_

#define _KERNEL_H_



#define TOTAL_ROWS                      25

#define TOTAL_COLUMNS                  80

#define CHAR_SIZE                      2

#define VIDEOMEM_ADD                    0xb8000

#define WHITE_TEXT_ON_BLACK_SCREEN      0x07



#endif

kernel.c

Code:

#include "kernel.h"



void cls();

int print( char *msg, unsigned int line );



os_main()

{

        cls();

        print("Hello World!!\n", 0);

}



void cls()

{

        char *videomemory = (char *)VIDEOMEM_ADD;

        unsigned int i = 0;

        

        while( i < (TOTAL_COLUMNS * TOTAL_ROWS * CHAR_SIZE) )

        {

                videomemory[i] = ' ';

                ++i;

                videomemory[i] = WHITE_TEXT_ON_BLACK_SCREEN;

                ++i;

        }

}



int print( char *msg, unsigned int line )

{

        char *videomemory = (char *)VIDEOMEM_ADD;

        unsigned int i = line * TOTAL_COLUMNS * CHAR_SIZE;



        while( *msg != 0 )

        {

                if( '\n' == *msg)

                {

                        ++line;

                        i = line * TOTAL_COLUMNS * CHAR_SIZE;

                        ++msg;

                }

                else

                {

                        videomemory[i] = *msg;

                        ++msg;

                        ++i;

                        videomemory[i] = WHITE_TEXT_ON_BLACK_SCREEN;

                        ++i;

                }

        }



        return 1;

}

I compiled this as follows:
gcc -c kernel.c

Then I linked the both the .o files:
ld kernel.o kernel_a.o -o kernel.bin

Then I copied this to /boot folder and created a new entry in GRUB as follows along with existing one:
title Fedora Core 1 (2.4.22-1.2115.nptl)
root (hd0,6)
kernel /vmlinuz-2.4.22-1.2115.nptl ro root=LABEL=/ hdc=ide-scsi rhgb
initrd /initrd-2.4.22-1.2115.nptl.img
title Windows XP Professional SP2
rootnoverify (hd0,0)
chainloader +1
title My Kernel
root (hd0,6)
kernel /vmlinuz.mykernel

and I booted the kernel with My Kernel. At that time it gave me the error as:
Error 13: Invalid or unsupported executable format

I am not able to get, why this error is coming. I also tried searching but could not get much info. Please assist.

I'm pretty sure when compiling a kernel you need special compilation options for gcc. This is because normal executables don't directly access the hardware; they are interpreted through the kernel. It has to be compiled as something that can run the machine itself. I don't know exactly how to do this, however. I've never written a kernel, but I know even modules can't be compiled like normal ELF programs.
ta0kira

Actually doing this was what prompted me to try and start learning assembly. Yes T is correct you need to compile the c program with special gcc stuff so that it does not link to standard library.

Below is from a online resource regarding this its actually a very good resource.

Code:

gcc -Wall -O -fstrength-reduce -fomit-frame-pointer -finline-functions -nostdinc -fno-builtin -I./include -c -o main.o main.c

Got from http://www.osdever.net/bkerndev/index.php

Hmmm, OK I will go through the website and will try. Thanks for the info.