32 bit ALP To find length of entered string

Q: Write an ALP to find the length of a string entered by the user.

Assembler: NASM
Debugger: GDB
OS: Ubuntu 14.04 LTS

Code

;Author:-Abhishek Vilas Munagekar

section .data

str: db "Enter text for which u wish to find the length!"
section .bss
len: resb 02
string: resb 100
count: resb 01
global _start
section .text
_start:
mov eax, 04 ;Write syscall to print msg
mov ebx, 01
mov ecx, str
mov edx, 47
int 80H

mov eax, 03 ;Read syscall to accept string
mov ebx, 01
mov ecx, string
mov edx, 32
int 80H

sub al, 01 ;Remove the extra character stored 
mov esi, len
mov byte[count],02
l: rol al, 04H ;Moving MSD to LSD
mov bl, al
and bl, 0FH ;Masking the higher bits
cmp bl, 09 ;Compare with nine
JBE m  ;If below or equal jump to label m
add bl, 07H ;else add correction factor
m: add bl, 30H
mov [esi], bl ;store ASCII value in esi
inc esi
Dec byte[count]
JNZ l
mov esi, len
 

mov eax, 04 ;Write syscall for printing the length
mov ebx, 01
mov ecx, esi
mov edx, 02
int 80H

mov eax, 01 ;Exit System Call
mov ebx, 00
int 80H