ELF LINKING PROBLEM
Posted: Fri Sep 20, 2002 11:24 am
I have a probably stupid problem about linking a simple kernel written in C and asm...
First of all, my boot loader put the kernel at 0000:0600h, then switch into protected mode and jump to the kernel location.
Here is my very simple asm kernel code:
[BITS 32]
[GLOBAL _start]
[EXTERN main]
; NOTE: We are already in protected mode setting up by the boot loader.
; Here is the start of the kernel code...
_start:
; Turn off floppy motor
mov dx, 0x03F2
mov al, 0x0C
out dx, al
; Call the C main procedure
jmp main
And here is the C program:
void clear_screen();
// C-kernel start
int main()
{
clear_screen();
for(;;);
}
void clear_screen()
{
char *video_mem = (char *) 0xB8000;
unsigned int i=0;
while(i < 80*25*2)
{
video_mem=0x02; // Smile
i++;
video_mem=0x0E; // Yellow
i++;
}
}
It should fill the screen with yellow smiles, but it doesn't work... Here is my compiling script:
nasm -f elf -o kernel.o kernel.s
gcc -c main.c -o kernel_c.o
ld -Ttext 0x600 -o kernel.bin kernel.o kernel_c.o
P.S. I compile all under LINUX with gcc 2.96, ld 2.11.92.0.12 and nasm 0.98...
It seems to me very strange, because I don't see errors... and it doesn't work also if I compile the asm file in a.out format...
First of all, my boot loader put the kernel at 0000:0600h, then switch into protected mode and jump to the kernel location.
Here is my very simple asm kernel code:
[BITS 32]
[GLOBAL _start]
[EXTERN main]
; NOTE: We are already in protected mode setting up by the boot loader.
; Here is the start of the kernel code...
_start:
; Turn off floppy motor
mov dx, 0x03F2
mov al, 0x0C
out dx, al
; Call the C main procedure
jmp main
And here is the C program:
void clear_screen();
// C-kernel start
int main()
{
clear_screen();
for(;;);
}
void clear_screen()
{
char *video_mem = (char *) 0xB8000;
unsigned int i=0;
while(i < 80*25*2)
{
video_mem=0x02; // Smile
i++;
video_mem=0x0E; // Yellow
i++;
}
}
It should fill the screen with yellow smiles, but it doesn't work... Here is my compiling script:
nasm -f elf -o kernel.o kernel.s
gcc -c main.c -o kernel_c.o
ld -Ttext 0x600 -o kernel.bin kernel.o kernel_c.o
P.S. I compile all under LINUX with gcc 2.96, ld 2.11.92.0.12 and nasm 0.98...
It seems to me very strange, because I don't see errors... and it doesn't work also if I compile the asm file in a.out format...