Introduction to Linux Assembly Programming with Messages
This assembly program demonstrates a simple example of using Linux syscalls to display messages on the console. It prints three different messages using the SYS_WRITE
syscall and then exits using the SYS_EXIT
syscall. The provided code is designed to be assembled and executed on a Linux environment.
source code
SYS_EXIT equ 1
SYS_WRITE equ 4
STDIN equ 0
STDOUT equ 1
section .text
global _start ; Must be declared for linker (gcc)
_start: ; Tell linker entry point
; Display "Hello, programmers!" message
mov eax, SYS_WRITE
mov ebx, STDOUT
mov ecx, msg1
mov edx, len1
int 0x80
; Display "Welcome to the world of," message
mov eax, SYS_WRITE
mov ebx, STDOUT
mov ecx, msg2
mov edx, len2
int 0x80
; Display "Linux assembly programming!" message
mov eax, SYS_WRITE
mov ebx, STDOUT
mov ecx, msg3
mov edx, len3
int 0x80
; Exit the program
mov eax, SYS_EXIT ; System call number (sys_exit)
int 0x80 ; Call kernel
section .data
msg1 db 'Hello, programmers!', 0xA, 0xD ; First message
len1 equ $ - msg1
msg2 db 'Welcome to the world of,', 0xA, 0xD ; Second message
len2 equ $ - msg2
msg3 db 'Linux assembly programming! ' ; Third message
len3 equ $ - msg3
Code Explanation
The assembly code performs the following steps:
Displaying Messages (
_start
section):Uses the
SYS_WRITE
syscall to display the "Hello, programmers!" message.Uses the same syscall to display the "Welcome to the world of," message.
Uses the syscall once again to display the "Linux assembly programming!" message.
Exiting the Program:
Uses the
SYS_EXIT
syscall to terminate the program.
Example
Suppose you assemble and execute the provided assembly code on a Linux environment. The program will display the following messages in sequence:
"Hello, programmers!"
"Welcome to the world of,"
"Linux assembly programming!"
Example Output:
Hello, programmers!
Welcome to the world of,
Linux assembly programming!
In this example, the program successfully displays the messages using the SYS_WRITE
syscall and then gracefully exits using the SYS_EXIT
syscall.
Usage
Ensure you are running this code on a Linux environment or emulator that supports the syscalls used in the code.
Assemble the code using an appropriate assembler (e.g., NASM) and linker (e.g., LD).
Run the assembled binary to execute the program.
Observe the output, which will display the provided messages in the order specified in the code.
Note: Assembly language can interact with system components. Make sure you understand the code before running it, especially when it involves system calls.
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