(N)ASM LoadLibrary,GetProcAddress & MessageBox![pusheax.com]

section .data

ldlibry dd  0
pro dd  0
dll db  "user32.dll",0
myFtion db  "MessageBoxA",0
MSG db  "ASM GetProcAddress",0

extern _LoadLibraryA@4
extern  _FreeLibrary@4
extern  _GetProcAddress@8
extern  _ExitProcess@4

global _start

section .text

_start:
    push    dll         ;push user32.dll
    call    _LoadLibraryA@4     ;Call the API.
    mov [ldlibry],eax       ;eax hold return address. So eax=LoadLibrary("user32.dll") and now ldlibry=LoadLibrary("user32.dll")

    ;now we need to call GetProcAddress

    push    myFtion         ;The API name we are going to call
    push    eax         ;LoadLibrary("user32.dll")
    call    _GetProcAddress@8   ;GetProcAddress(LoadLibrary("user32.dll"),"MessageBoxA"). Again eax holding the return address


    push    0x0         ;MB_OK
    push    MSG         ;TITLE="ASM GetProcAddress"
    push    MSG         ;Messgage="ASM GetProcAddress"
    push    0           ;Reserved=0
    call    eax         ;Call MessageBoxA through GetProcAddress.

    push    dword [ldlibry]     ; ldlibry holding the LoadLibrary("user32.dll"). Again load to Free up.
    call    _FreeLibrary@4      ;Call the Windows api FreeLibrary()

    ;We should exit the process otherwise it may cause "access violation"
    push    0           ;load 0 to stack
    call    _ExitProcess@4      ;Call ExitProcess


    ;Assembl:
    ;nasm -fwin32 ldlibrary.asm
    ;ld -o ldlibrary.exe ldlibrary.obj -lkernel32