Hook Windows API (MessageBox) using Odin Lang

hook.odin

package hook

import "core:fmt"
import "core:intrinsics"
import "core:mem"
import "core:os"
import "core:runtime"
import "core:strings"
import win32 "core:sys/windows"

message_box_hook :: proc "stdcall" (
    hwnd: rawptr, text: cstring, caption: cstring, type: u32
) -> i32 {
	aeho := intrinsics.constant_utf16_cstring("HOOKED")

    context = runtime.default_context()
    defer fmt.println("running after message box")
    fmt.println("running at hook")

    return win32.MessageBoxW(nil, aeho, win32.utf8_to_wstring(string(caption)), type)
}

call_hook :: proc (hook_at: uintptr, new_func: uintptr) {
	// jmp_inst := [12]u8{0x48, 0xB9, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x51, 0xC3}
	jmp_inst := [?]u8{0x49, 0xBA, 0xAA, 0xAA, 0xAA, 0xAA, 0xAA, 0xAA, 0xAA, 0xAA, 0x41, 0xFF, 0xE2};
    mem.copy(&jmp_inst[2], transmute(rawptr)new_func, size_of(new_func))

    old_protection: u32
    win32.VirtualProtectEx(
        win32.GetCurrentProcess(), transmute(rawptr)hook_at, size_of(jmp_inst),
        win32.PAGE_READWRITE, &old_protection)

	bytes_written: uint
	win32.WriteProcessMemory(
	       win32.GetCurrentProcess(), transmute(rawptr)hook_at, transmute(rawptr)&jmp_inst,
	       size_of(jmp_inst), &bytes_written)

    win32.VirtualProtectEx(
        win32.GetCurrentProcess(), transmute(rawptr)hook_at, size_of(jmp_inst),
        old_protection, &old_protection)
}

main :: proc() {
	aeho := cstring("AEHO")
	win32.MessageBoxA(nil, aeho, aeho, win32.MB_OK)

	library := win32.LoadLibraryW(win32.utf8_to_wstring("user32.dll"))
	message_box_address := win32.GetProcAddress(library, "MessageBoxA")

	message_box_hook_address := message_box_hook
    call_hook(uintptr(message_box_address), uintptr(&message_box_hook_address))

	win32.MessageBoxA(nil, aeho, aeho, win32.MB_OK)
}