Nasm simple bootloader. Call and ret do not work properly

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I have this code:

;bootloader
[bits 16]
[org 0x7c00]

jmp main

print_char:
    mov ah,0x0e
    mov bh,0x00
    mov al,65
    int 0x10
ret

main:
    call print_char

times 510-($-$$) db 0
dw 0xAA55

So, it should jump to main and call print_char to print a letter A on the screen, but it doesn't work! I'am using a qemu+gdb for testing. I set sevreal breakpoints in gdb one at the begining, anouther one at call print_char and last one on ret. I found that print_char is not called in this code. What is wrong with my code?

My debug session:

(gdb) target remote localhost:1234
Remote debugging using localhost:1234
0x0000fff0 in ?? ()
(gdb) br *0x7c00
Breakpoint 1 at 0x7c00
(gdb) br *0x7c00+0x3
Breakpoint 2 at 0x7c03
(gdb) br *0x7c00+0xb
Breakpoint 3 at 0x7c0b
(gdb) br *0x7c00+0xc
Breakpoint 4 at 0x7c0c
(gdb) stepi
0x0000e05b in ?? ()
(gdb) c
Continuing.

Breakpoint 1, 0x00007c00 in ?? ()
(gdb) stepi

Breakpoint 4, 0x00007c0c in ?? ()
(gdb) stepi
0x00007c0e in ?? ()
(gdb) stepi
0x00007c10 in ?? ()
(gdb) stepi
0x00007c12 in ?? ()
(gdb) stepi
0x00007c15 in ?? ()
(gdb)

lst file:

 1                                  ;bootloader
 2                                  [bits 16]
 3                                  [org 0x7c00]
 4                                  
 5                                  
 6 00000000 E90900                  jmp main
 7                                  
 8                                  print_char:
 9 00000003 B40E                        mov ah,0x0e
10 00000005 B700                        mov bh,0x00
11 00000007 B041                        mov al,65
12 00000009 CD10                        int 0x10
13 0000000B C3                      ret
14                                  
15                                  main:
16 0000000C E8F4FF                      call print_char
17                                      
18                                  
19 0000000F 00<rept>                times 510-($-$$) db 0
20         

21 000001FE 55AA                    dw 0xAA55

asked 54 secs ago

Ivan Posti

1

Nasm simple bootloader. Call and ret do not work properly