Interrupt 10h not working

Question

I am getting segmentation fault in the program below.
This is for set the cursor on the top-left of the screen. But why i am getting segmentation fault on this program?

Answer 1

BIOS interrupts are 16-bit code. Your OS has put the CPU in 32-bit protected mode. The hardware will allow a switch back to 16-bit real mode (there are hoops to jump through) but the OS won't allow it. Wouldn't be very "protected" if it did. It is "protected" from US, my friend!

I think what you probably want to look into is "vt100" terminal emulation. By rights, a "robust" program would consult the "termcaps" file to make sure vt100 emulation is available before attempting to use it. My experience is that it's "usually" available on a "desktop Linux" box, so I just ASSume it's there. Worst that can happen (I think) is garbage on the screen if we ASSume wrong.

This example doesn't do exactly what you want. It saves the current cursor position (lord knows where), moves the cursor to a new position, prints a message, and goes back to the original cursor position. You'll need to look up the "home cursor" command ("ESC [h"? lookitup). Just write it to stdout, same as "hello world". You can get colors and stuff, too.

; nasm -f elf32 mygem.asm
; ld -o mygem mygem.o -melf_i386

global _start

section .data
savecursor db 1Bh, '[s'
.len equ $ - savecursor

unsavecursor db 1Bh, '[u'
.len equ $ - unsavecursor

getcursor db 1Bh, '[6n'
.len equ $ - getcursor

setcursor db 1Bh, '[10;20H'
.len equ $ - setcursor

msg db "Hello, new cursor position!"
.len equ $ - msg

section .text
_start:

mov ecx, savecursor
mov edx, savecursor.len
call write_stdout


mov ecx, setcursor
mov edx, setcursor.len
call write_stdout

mov ecx, msg
mov edx, msg.len
call write_stdout

mov ecx, unsavecursor
mov edx, unsavecursor.len
call write_stdout

exit:
mov eax, 1
xor ebx, ebx
int 80h

;------------------------
write_stdout:    
push eax
push ebx
mov eax, 4
mov ebx, 1
int 80h
pop ebx
pop eax
ret
;---------------------