64-bit GNU assembler Hello World for Windows

hello.s

# Build:
#
# as -o hello.obj
# ld -o hello.exe hello.obj -L C:\\tools\\mingw64\\x86_64-w64-mingw32\\lib -lkernel32
#
# Requires MinGW

.extern GetStdHandle
.extern WriteFile
.extern ExitProcess

.section .rodata

msg: .ascii "Hello World!\r\n"

.equ msg_len, .-msg
.equ stdout_query, -11

.section .data

stdout: .long 0

bytes_written: .long 0

.section .text

.global start

start:
    mov $stdout_query, %rcx
    call GetStdHandle
    mov %rax, (stdout)

    mov  (stdout), %rcx
    mov  $msg, %rdx
    mov  $msg_len, %r8
    mov  $bytes_written, %r9
    push $0
    call WriteFile

    xor %rcx, %rcx
    call ExitProcess