Input from keyboard in assembly language using system call

Question

I am trying to create my own gets and puts function using system calls in NASM assembly language. So far the puts function works in this code just fine but I can not get the terminal to wait for input from the keyboard in the gets function.

global start

SECTION .text

SECTION .data
    prompt1: db "We will make you a box.  How tall would you like it to be?", 0
    length1: equ $-prompt1
    prompt2: db "How wide would you like it to be?" , 0
    length2: equ $-prompt2
    input: dd 0




start:
    mov edi, prompt1
    mov esi, length1
    call puts

    mov edi, input
    mov esi, 4
    call gets

    mov eax, 0
    ret


puts:
    mov dword [esp], 1
    mov dword [esp+8], esi
    mov dword [esp+4], edi
    mov eax, 0x4
    sub esp, 4
    int 0x80
    add esp, 16
    ret

gets:
    mov dword [esp], 0
    mov dword [esp+4], esi
    mov dword [esp+8], edi
    mov eax, 3
    sub esp, 4
    int 0x80
    add esp, 16
    ret

This is the output: We will make you a box. How tall would you like it to be?

But it doesn't prompt for input... Help please!

First You must search: http://stackoverflow.com/questions/7787891/linux-x86-asm-getting-user-input — icbytes, Nov 13 '13 at 08:14
After a `call`, `[esp]` holds your return address... or did, before you clobbered it. If you're going to use the stack like that, `sub esp, 12` first. — Frank Kotler, Nov 13 '13 at 09:23
@FrankKotler you actually don't have to sub from the stack first. — Edge, Nov 14 '13 at 06:36

score 0 · Answer 1 · answered Nov 14 '13 at 06:37

0

The issue was that I need to use the .bss section for uninitialized data.

answered Nov 14 '13 at 06:37

Edge

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Input from keyboard in assembly language using system call

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