问题
I want to call printf function from assembly language in linux.
i want to know the method for for 64 bit and 32 bit assembly language programs.
1) please tell me for two cases if i want to pass a 32 bit arguement and 64 bit arguement in printf with a string. how should i do it?
2) for x86 32 bit architecture if i want to do the same thing as in point 1.
please tell me the code. and let me know do i need to adjust the stack for both cases and do i just need to pass the arguements in registers?
Thanks alot
回答1:
There are 2 ways to print a string with assembly language in Linux.
1) Use syscall for x64, or int 0x80 for x86. It's not printf, it's kernel routines. You can find more here (x86) and here (x64).
2) Use printf from glibc. I assume you are familiar with the structure of NASM program, so here is a nice x86 example from acm.mipt.ru:
global main
;Declare used libc functions
extern exit
extern puts
extern scanf
extern printf
section .text
main:
;Arguments are passed in reversed order via stack (for x86)
;For x64 first six arguments are passed in straight order
; via RDI, RSI, RDX, RCX, R8, R9 and other are passed via stack
;The result comes back in EAX/RAX
push dword msg
call puts
;After passing arguments via stack, you have to clear it to
; prevent segfault with add esp, 4 * (number of arguments)
add esp, 4
push dword a
push dword b
push dword msg1
call scanf
add esp, 12
;For x64 this scanf call will look like:
; mov rdi, msg1
; mov rsi, b
; mov rdx, a
; call scanf
mov eax, dword [a]
add eax, dword [b]
push eax
push dword msg2
call printf
add esp, 8
push dword 0
call exit
add esp, 4
ret
section .data
msg : db "An example of interfacing with GLIBC.",0xA,0
msg1 : db "%d%d",0
msg2 : db "%d", 0xA, 0
section .bss
a resd 1
b resd 1
You can assembly it with nasm -f elf32 -o foo.o foo.asm and link with gcc -m32 -o foo foo.o for x86. For x64 just replace elf32 with elf64 and -m32 with -m64. Note than you need gcc-multilib to build x86 programs on x64 system using gcc.
来源：https://stackoverflow.com/questions/40458869/calling-printf-from-assembly-language-on-64bit-and-32bit-architecture-using-nasm