Segmentation fault in my Assembly implementation

Question

I am new to assembly language programing, and here I am trying to call C standard library function puts from my assembly code, but I am continuously getting segmentaion fault. Please help; Operating system : LINUX 16.04 Assembler : nasm Machine : intel x86 - 64bit

;comiple and build:
;                   nasm -f elf64 -F stabs helloc.asm
;                   gcc -o helloC helloC.o
[SECTION .data]
   msg: db "Hello C",0
[SECTION .bss]

[SECTION .text] 
 extern puts

 global main 
 main:
  push rsp

  push dword msg
  call puts
  add rsp,4

  pop rsp
  ret

Answer 1

to explain Comments More, start with x86 calling convention and your code.

x86 Calling Convention

In x86, arguments are located in stack. So basically your function call is x86 way. for example, If you build your code for x86,

[SECTION .data]
   msg: db "Hello C",0
[SECTION .bss]

[SECTION .text] 
 extern puts

 global main 
 main:
  push ebp
  mov ebp, esp
  and esp, 0xfffffff0
  sub esp, 0x10

  mov DWORD PTR [esp], msg
  call puts


  mov esp, ebp
  pop ebp
  ret

It may works fine.

x86-64 Calling Convention

Main difference is two things.

• using 8 bytes to represent address, of course
• use 6 registeres (rdi, rsi, rdx, rcx, r8, r9) for represent first 6 arguments (rest is located in stack)

so first, you should change push dword msg to mov rdi, msg, and don't clean stack after call (because you didn't push anything to stack)

after change:

[SECTION .data]
   msg: db "Hello C",0
[SECTION .bss]

[SECTION .text] 
 extern puts

 global main 
 main:
  push rbp
  mov rbp, rsp
  and rsp, 0xfffffffffffffff0

  mov rdi, msg
  call puts


  mov rsp, rbp
  pop rbp
  ret

EDIT: from System V ABI, for call instruction stack be should 16-byte aligned. so push rbp has effect to alignment, but it is not correct purpose to use. to change that, make stack save logic for both x86 and x86-64.