Answer to Question #257361 in Assembler for joe

Question

write a function B() in assembly lang programming which takes the argument as 64 bit integer. It should interpret that as a 8-byte ASCII string and print individual

characters on screen. You need to call the write() system call from assembly language using the syscall instruction, passing appropriate arguments.

Modify the stack in the function B() in such a way that when B() executes

the ret instruction, it jumps to a third function C(). C() must also be

written in C.

Answer 1

; que.asm
; Assemble:    nasm -f elf64 -l que.lst  que.asm
; Link:        gcc -o que  que.o
; Run:        ./que

   SECTION .data
strc:    db 10,13,"func c()",10,13,0
str:    dd 0
    
   SECTION .text           ; Code section.
   global main    
main:                
     mov rax,0x3031323334353637    ;;64 bits integer
     mov rbx, c  
     push rbx
    call b
;***************************
  b:
;***************************
    mov [str], rax
    
; sys_write
    mov eax,4
    mov ebx,1
    mov ecx, str
    mov edx,8
    int 80h
    
    pop rax
    ret
;***************************
  c:
;***************************
; sys_write:  "func c()"
    mov eax,4
    mov ebx,1
    mov ecx, strc
    mov edx,13
    int 80h

; sys_exit    
    mov rax,1
    mov rbx,0
    int 80h