Unable to find error in small boot loader program
Posted: Sat Sep 03, 2011 4:45 am
Hello Sir, I am using DELL laptop and with the help of QEMU, NASM and GCC i am trying to compile a simple code which is not executing properly. I am using UBUNTU 10.04.
here is the loader.asm assembly file.
$nasm -f elf loader.o loader.asm
my c program kernel.c
$gcc -o kernel.o -c kernel.c -Wall -Wextra -nostdlib -nostartfiles -nodefaultlibs
linker prorgram linker.ld
$ld -T linker.ld -o kernel.bin loader.o kernel.o
$qemu -kernel -kernel.bin
in the output part of QEMU , nothing is displayed. I tried to find error but i am not getting it, Its also not like that its not addressing video memory as in my output clr() is working and clearing the screen but print() is not working it should give output:- Error:Invalid Number.
I am not getting the error, Please help me out..
here is the loader.asm assembly file.
Code: Select all
global loader
extern dmain
MODULEALIGN equ 1<<0
MEMINFO equ 1<<1
FLAGS equ MODULEALIGN | MEMINFO
MAGIC equ 0x1BADB002
CHECKSUM equ -(MAGIC + FLAGS)
section .text
align 4
MultiBootHeader:
dd MAGIC
dd FLAGS
dd CHECKSUM
STACKSIZE equ 0x4000
loader:
mov esp, stack+STACKSIZE
push eax
push ebx
call dmain
cli
hang:
hlt
jmp hang
section .bss
align 4
stack :
resb STACKSIZE
my c program kernel.c
Code: Select all
void dmain(void* mbd ,unsigned int magic)
{
if(magic !=0x1BADB002)
{
clr();
print("Error:Invalid Number",0xAF);
}
else
{
clr();
print("Hello World",0xAF);
}
}
void print(char* msg,int color)
{
char* mem=(char*) 0xB8000;
while(*msg !=0)
{
*mem= *msg;
mem++;
msg++;
*mem=(char*) color;
mem++;
}
}
void clr(void)
{
char* mem=(char*) 0xB8000;
while(*mem !=0)
{
*mem = 0;
mem++;
}
}
linker prorgram linker.ld
Code: Select all
ENTRY(loader)
SECTIONS{
. =0x00100000 ;
.text :{
*(.text)
}
.rodata ALIGN (0x1000) :{
*(.data)
}
.bss : {
sbss = .;
*(COMMON)
*(.bss)
ebss = .;
}
}
$qemu -kernel -kernel.bin
in the output part of QEMU , nothing is displayed. I tried to find error but i am not getting it, Its also not like that its not addressing video memory as in my output clr() is working and clearing the screen but print() is not working it should give output:- Error:Invalid Number.
I am not getting the error, Please help me out..