This question already has answers here:
Infinite loop after cin c++
(1 answer)
Timeout error C++
(2 answers)
Closed 4 years ago.
My assignment is to ask the user for input and the output would return their name.
Here is my code :
section .data
user: db 'Hello.What is your name ? '
user_L: equ $-user ;length of the UserNameMsg segment
hello: db ' Hello'
hello_L: equ $-hello
section .bss
user_v: resb 23
section .text
global _start
_start:
mov eax, 4
mov ebx, 1
mov ecx, user
mov edx, user_L
int 0x80
mov eax, 3
mov ebx, 0
mov ecx, user
mov edx, 23
int 0x80
mov eax, 4
mov ebx, 1
mov ecx, hello
mov edx, hello_L
int 0x80
mov eax,4
mov ebx, 1
mov ecx, user_v
mov edx, 23
int 0x80
mov eax, 1
mov ebx, 0
int 0x80
When i ran my code in JDoodle's online assembler I get the error saying:
Timeout - Some common reasons for Timeout Your Program may have a endless loop
I'm not sure what to do to fix this error.
Related
This question already has answers here:
X86 NASM Assembly converting lower to upper and upper to lowercase characters
(5 answers)
X86 Assembly Converting lower-case to uppercase
(1 answer)
Closed 3 years ago.
I want to change the string to all caps, although I am having trouble getting the length of the input. What i have tried so far is moving the address of the message into a registrar then indexing through the string and also increment a counter variable. Then comparing the char in the address to a '.' (signifying the end of the message) and if its found not to be equal it will recall this block of statements. At least this is what I want my code to do. Not sure if this is even the right logic. I know there are alot of errors and its messy but I'm learning so please just focus on my main question. thank you! EDIT: the input i use is 'this is a TEST.'
;nasm 2.11.08
SYS_Write equ 4
SYS_Read equ 3
STDIN equ 0
STDOUT equ 1
section .bss
message resb 15
counter resb 2
section .data
msg1: db 'Enter input (with a period) that I will turn into all capitals!',0xa ;msg for input
len1 equ $- msg1
section .text
global _start
_start:
mov eax, SYS_Write ; The system call for write (sys_write)
mov ebx, STDOUT ; File descriptor 1 - standard output
mov ecx, msg1 ; msg to print
mov edx, len1 ; len of message
int 0x80 ; Call the kernel
mov eax, SYS_Read ;system call to read input
mov ebx, STDIN ;file descriptor
mov ecx, message ;variable for input
mov edx, 15 ;size of message
int 0x80 ;kernel call
mov [counter], byte '0'
getLen:
mov eax, message
add eax, [counter]
inc byte [counter]
cmp eax, '.'
jne getLen
mov eax, SYS_Write ; this is to print the counter to make sure it got the right len
mov ebx, STDOUT
mov ecx, counter
mov edx, 2
int 0x80
jmp end
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
mov eax, [message]
;add eax, counter
cmp eax, 90
jg toUpper
toUpper:
sub eax, 32
mov [message], eax
mov eax, SYS_Write ; The system call for write (sys_write)
mov ebx, STDOUT ; File descriptor 1 - standard output
mov ecx, message ; Put the offset of hello in ecx
mov edx, 10 ; helloLen is a constant, so we don't need to say
int 0x80 ; Call the kernel
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
end:
mov eax,1 ; The system call for exit (sys_exit)
mov ebx,0 ; Exit with return code of 0 (no error)
int 0x80 ;
I am new have very small problem with assembly NASM in linux. I made simple program for practice that when you put in the text, it adds simple decoration in form of stars. The expected output is:
*********EXAMPLE*********
instead:
*********EXAMPLE
*********
here is the complete code of the program (long) i have use edb to check the code and check EDX register if it match the len take by the null byte check to print correct number of characters.
section .data
prompt db "Please enter a word (MAX: 10 Characters) : ", 0xa, 0xd
plen equ $ - prompt
stars times 9 db "*"
section .bss
text resb 10
section .text
global _start
_start:
mov eax, 4
mov ebx, 1
mov ecx, prompt
mov edx, plen
int 0x80
mov eax, 3
mov ebx, 0
mov ecx, text
mov edx, 11
int 0x80
xor ecx, ecx
mov esi, text
mov ecx, 0
loop1:
inc ecx
cmp byte [esi + ecx], 0x00
jne loop1
push ecx
jmp printexit
printexit:
mov eax, 4
mov ebx, 1
mov ecx, stars
mov edx, 9
int 0x80
mov eax, 4
mov ebx, 1
mov ecx, text
pop edx
int 0x80
mov eax, 4
mov ebx, 1
mov ecx, stars
mov edx, 9
int 0x80
mov eax, 1
int 0x80
I am currently learning the ASM, I have a question about the following code (which compiles)
This code come from this tutorial.
The question is: Why do I have the same behaviour when the fd is egual to 0, 1 or 2 (corresponding to stdin, stdout and stderr), at the indicated line, and when the fd is egual to 3 or more, it does nothing (it skips the scanf).
section .data ;Data segment
userMsg db 'Please enter a number: ' ;Ask the user to enter a number
lenUserMsg equ $-userMsg ;The length of the message
dispMsg db 'You have entered: '
lenDispMsg equ $-dispMsg
section .bss ;Uninitialized data
num resb 5
section .text ;Code Segment
global _start
_start: ;User prompt
mov eax, 4
mov ebx, 1
mov ecx, userMsg
mov edx, lenUserMsg
int 80h
;Read and store the user input
mov eax, 3
mov ebx, 2 ; /!\ QUESTION IS ABOUT THIS LINE /!\
mov ecx, num
mov edx, 5 ;5 bytes (numeric, 1 for sign) of that information
int 80h
;Output the message 'The entered number is: '
mov eax, 4
mov ebx, 1
mov ecx, dispMsg
mov edx, lenDispMsg
int 80h
;Output the number entered
mov eax, 4
mov ebx, 1
mov ecx, num
mov edx, 5
int 80h
; Exit code
mov eax, 1
mov ebx, 0
int 80h
We can compile and execute this code with the following command:
$> nasm -f elf64 test.S
$> ld test.o
$> ./a.out
Thank you,
I wrote this code, it reads the data from user but did not display the output. It is written in Assembly language. I am new to Assembly language. Can somebody please help me in solving this. I shall be very thankful. Thanks in advance. Here is the code:
section .data ;Data segment
userMsg db 'Please enter a number: ' ;Ask the user to enter a number
lenUserMsg equ $-userMsg ;The length of the message
dispMsg db 'You have entered: '
lenDispMsg equ $-dispMsg
section .bss ;Uninitialized data
num resb 5
section .text ;Code Segment
global _start
_start:
;User prompt
mov eax, 4
mov ebx, 1
mov ecx, userMsg
mov edx, lenUserMsg
int 80h
;Read and store the user input
mov eax, 3
mov ebx, 2
mov ecx, num
mov edx, 5 ;5 bytes (numeric, 1 for sign) of that information
int 80h
;Output the message 'The entered number is: '
mov eax, 4
mov ebx, 1
mov ecx, dispMsg
mov edx, lenDispMsg
int 80h
;Output the number entered
mov eax, 4
mov ebx, 1
mov ecx, num
mov edx, 5
int 80h
; Exit code
mov eax, 1
mov ebx, 0
int 80h
In typical environments, file descripter 0 stands for standard input, 1 for standard output, and 2 for standard error output.
Reading from standard error output makes no sense for me.
Try changing the program for reading
;Read and store the user input
mov eax, 3
mov ebx, 2
mov ecx, num
mov edx, 5 ;5 bytes (numeric, 1 for sign) of that information
int 80h
to
;Read and store the user input
mov eax, 3
mov ebx, 0
mov ecx, num
mov edx, 5 ;5 bytes (numeric, 1 for sign) of that information
int 80h
in order to have the system read some data from standard input.
section .data
out1: db 'Enter the number:'
out1l: equ $-out1
out2: db 'The number you entered was:'
out2l: equ $-out2
section .bss
input: resb 4
section .text
global _start
_start:
;for displaying the message
mov eax,4
mov ebx,1
mov ecx,out1
mov edx,out1l
int 80h
;for taking the input from the user
mov eax,3
mov ebx,0
mov ecx,input
mov edx,4
int 80h
;for displaying the message
mov eax,4
mov ebx,1
mov ecx,out2
mov edx,out2l
int 80h
;for displaying the input
mov eax,4
mov ebx,1
mov ecx,input
mov edx,4
int 80h
mov eax,1
mov ebx,100
int 80h
Going from high to low lever language I got to assembly. Now at the very beginning, I wrote a simple age program (I'm not clear how to get system time yet so I just used another input). I get Segmentation Fault (core dumped) after I enter the final input. Here is my code:
section .text
global _start
_start:
mov edx, lenask
mov ecx, ask
mov ebx, 1
mov eax, 4
int 0x80
mov edx, 5
mov ecx, input
mov ebx, 2
mov eax, 3
int 0x80
mov edx, lenask2
mov ecx, ask2
mov ebx, 1
mov eax, 4
int 0x80
mov edx, 5
mov ecx, input2
mov ebx, 2
mov eax, 3
int 0x80
mov eax, input2
mov ebx, input
sub eax, ebx
push eax
mov edx, lenanswer
mov ecx, answer
mov ebx, 1
mov eax, 4
int 0x80
pop eax
mov edx, 7
mov ecx, eax
mov ebx, 1
mov eax, 4
int 0x80
section .data
ask db "What is your age?"
lenask equ $-ask
ask2 db "What is today's year?"
lenask2 equ $-ask2
answer db "The age you were born was: "
lenanswer equ $-answer
section .bss
input resb 5
input2 resb 5
An example of what happens:
What is your age?45
What is today's year?2015
The age you were born was: Segmentation fault
It should have done:
What is your age?45
What is today's year?2015
The age you were born was: 1970
The problem is that int 0x80 with eax set to 4 calls the kernel's sys_write function (i.e. a write system call) which expects a pointer to a string. By providing a integer to the function call the kernel will think that the integer is a pointer to a memory location. Because 1970 is not a valid pointer it will raise a -EFAULT. To bypass this you need to code a ToString function to convert the number to a string and then pass the pointer to the converted string.
The Segmentation Fault itself is caused by not having a sys_exit call. The reason for this is that the program will continue past the end of your code (usally into a bunch of 00 00)