How To Properly call 64 Bit Windows API In Assembl

问题:

Using NASM and Mingw-w64 I've been trying to run the following program which is supposed to print a message to the screen using the Windows API. It runs, but nothing shows on the console and it results in an invalid access to memory location (error code 0x3e6h). Why is that, and how can I get the program to run properly?

global main
extern ExitProcess
extern GetStdHandle
extern WriteFile

section .text
main:
    mov     rcx,                  0fffffff5h
    call    GetStdHandle

    mov     rcx,                  rax
    mov     rdx,                  NtlpBuffer
    mov     r8,                   NtnNBytesToWrite
    mov     r9,                   NtlpNBytesWritten
    mov     dword [rsp - 04h],    00h
    call    WriteFile
ExitProgram:
    mov     rcx,                  00h
    call    ExitProcess

section .data
NtlpBuffer:        db    'Hello, World!', 00h
NtnNBytesToWrite:  dd    0eh

section .bss
NtlpNBytesWritten: resd  01h

Compiled by

nasm -f win64 test.asm
gcc -s -o test.exe test.obj

回答1:

[rsp-04h] is addressing below the stack pointer, that's a bad idea. Whatever you write there will be overwritten by the call anyway. Looks like you need to brush up on your knowledge of the calling convention. Shadow space for the 4 arguments in registers have to be allocated and further arguments must be placed on top of them.

Also, the number of bytes to write should be the actual number, not a pointer.

global main
extern GetStdHandle
extern WriteFile

section .text
main:
    mov     rcx, 0fffffff5h
    call    GetStdHandle

    mov     rcx, rax
    mov     rdx, NtlpBuffer
    mov     r8, [NtnNBytesToWrite]
    mov     r9, NtlpNBytesWritten
    sub     rsp, 40
    mov     dword [rsp + 32], 00h
    call    WriteFile
    add     rsp, 40
ExitProgram:
    xor     eax, eax
    ret

section .data
NtlpBuffer:        db    'Hello, World!', 00h
NtnNBytesToWrite:  dq    0eh

section .bss
NtlpNBytesWritten: resd  01h