I want my Assembly Code to takes user input and outputs it along with other text but the output isn&-CodePudding

My code works but the output isn't just right because when I enter the name, the output becomes this; "What is your member name? Welcome to the club, Bob!!!!!!!!!!!!!!!!!!, enjoy the party." with the "!!!!!!" at the end of the name. What am I doing wrong?

Here is my assembly code:

section .data
prompt:       db      "What is your member name? "
prompt_len:   equ     $-prompt
greet1:        db      "Welcome to the club, "
greet1_len:    equ     $-greet1
greet2:        db      ", enjoy the party."
greet2_len:    equ     $-greet2

inputbuffer_len:   equ    256
inputbuffer:       times inputbuffer_len  db '!'

STDIN:        equ     0
STDOUT:       equ     1
SYS_READ:     equ     0
SYS_WRITE:    equ     1
SYS_EXIT:     equ     60

section .text

global _start
 _start:
    mov     rdx,    prompt_len      ;output prompt          
    mov     rax,    SYS_WRITE
    mov     rdi,    STDOUT
    mov     rsi,    prompt    
    syscall
    
    mov     rax,    SYS_READ ;user input here
    mov     rdi,    STDIN
    mov     rsi,    inputbuffer
    mov     rdx,    inputbuffer_len
    syscall
    
    mov     rdx,    greet1_len        ; output "Welcome to the club, "        
    mov     rax,    SYS_WRITE
    mov     rdi,    STDOUT
    mov     rsi,    greet1    
    syscall
    mov     rdx,    rax            ;output user's inputted name
    mov     rax,    SYS_WRITE
    mov     rdi,    STDOUT
    mov     rsi,    inputbuffer    
    syscall
    
    mov     rdx,    greet2_len         ; output ", enjoy the party."         
    mov     rax,    SYS_WRITE
    mov     rdi,    STDOUT
    mov     rsi,    greet2    
    syscall

    mov     rax,    SYS_EXIT
    mov     rdi,    0
    syscall

CodePudding user response：

The length of Bob!!!!!!!!!!!!!!!!!! is the length of Welcome to the club, . This is no coincidence. Following the write(2) system call rax contains the number of successfully written Bytes. (This might be less than the desired number of Bytes as the manual page describes.)

Like David C. Rankin commented you will need to mind the return value of read(2). On success, read(2) returns the number of Bytes read in rax. However, you are overwriting this value for and with the intervening write(2) system call. Store and recall somewhere the number of successfully read Bytes (e. g. push/pop) and you’re good.

PS: You could save one write(2) system call by rearranging the buffer to follow after greet_1. Then you could write(2) rax greet1_len Bytes at once. But one problem at a time.