api: ensure more code compiles by using dead code elimination

It'd be nicer to do this via

if (is_defined(HAVE_WHATEVER))

But MSVC won't work with the linux kernel macros for this. Ongoing
research.

Nevertheless, this makes most of the program always pass through the
compiler's type checker, only to have dead code removed later.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

api/adapter.c

@@ -340,7 +340,8 @@ EnableAllOurAdapters(_In_ HDEVINFO DevInfo, _In_ SP_DEVINFO_DATA_LIST *AdaptersT
 void
 AdapterInit(void)
 {
-#ifdef MAYBE_WOW64
+    if (!MAYBE_WOW64)
+        return;
     typedef BOOL(WINAPI * IsWow64Process2_t)(
         _In_ HANDLE hProcess, _Out_ USHORT * pProcessMachine, _Out_opt_ USHORT * pNativeMachine);
     HANDLE Kernel32;
@@ -354,7 +355,6 @@ AdapterInit(void)
         NativeMachine =
             IsWow64Process(GetCurrentProcess(), &IsWoW64) && IsWoW64 ? IMAGE_FILE_MACHINE_AMD64 : IMAGE_FILE_PROCESS;
     }
-#endif
 }
 
 static BOOL
@@ -801,13 +801,13 @@ RtlGetNtVersionNumbers(_Out_opt_ DWORD *MajorVersion, _Out_opt_ DWORD *MinorVers
 static BOOL
 HaveWHQL(void)
 {
-#if defined(HAVE_WHQL)
+    if (HAVE_WHQL)
-    DWORD MajorVersion;
+    {
-    RtlGetNtVersionNumbers(&MajorVersion, NULL, NULL);
+        DWORD MajorVersion;
-    return MajorVersion >= 10;
+        RtlGetNtVersionNumbers(&MajorVersion, NULL, NULL);
-#else
+        return MajorVersion >= 10;
+    }
     return FALSE;
-#endif
 }
 
 static WINTUN_STATUS
@@ -1682,15 +1682,10 @@ WintunCreateAdapter(
         RebootRequired = &DummyRebootRequired;
     *RebootRequired = FALSE;
     DWORD Result;
-#ifdef MAYBE_WOW64
+    if (MAYBE_WOW64 && NativeMachine != IMAGE_FILE_PROCESS)
-    if (NativeMachine != IMAGE_FILE_PROCESS)
-    {
         Result = CreateAdapterViaRundll32(Pool, Name, RequestedGUID, Adapter, RebootRequired);
-        RevertToSelf();
+    else
-        return Result;
+        Result = CreateAdapter(Pool, Name, RequestedGUID, Adapter, RebootRequired);
-    }
-#endif
-    Result = CreateAdapter(Pool, Name, RequestedGUID, Adapter, RebootRequired);
     RevertToSelf();
     return Result;
 }
@@ -1706,14 +1701,12 @@ WintunDeleteAdapter(_In_ const WINTUN_ADAPTER *Adapter, _In_ BOOL ForceCloseSess
         RebootRequired = &DummyRebootRequired;
     *RebootRequired = FALSE;
     DWORD Result;
-#ifdef MAYBE_WOW64
+    if (MAYBE_WOW64 && NativeMachine != IMAGE_FILE_PROCESS)
-    if (NativeMachine != IMAGE_FILE_PROCESS)
     {
         Result = DeleteAdapterViaRundll32(Adapter, ForceCloseSessions, RebootRequired);
         RevertToSelf();
         return Result;
     }
-#endif
 
     HDEVINFO DevInfo;
     SP_DEVINFO_DATA DevInfoData;
@@ -1796,14 +1789,12 @@ WintunDeleteDriver(void)
 
     DWORD Result = ERROR_SUCCESS;
 
-#ifdef MAYBE_WOW64
+    if (MAYBE_WOW64 && NativeMachine != IMAGE_FILE_PROCESS)
-    if (NativeMachine != IMAGE_FILE_PROCESS)
     {
         Result = DeleteDriverViaRundll32();
         RevertToSelf();
         return Result;
     }
-#endif
 
     /* DeleteAllOurAdapters(); */
     HANDLE DriverInstallationLock = NamespaceTakeDriverInstallationMutex();

api/entry.c

@@ -33,7 +33,7 @@ static FARPROC WINAPI DelayedLoadLibraryHook(unsigned dliNotify, PDelayLoadInfo
 }
 
 const PfnDliHook __pfnDliNotifyHook2 = DelayedLoadLibraryHook;
-
+#define NOT 1
 BOOL APIENTRY
 DllMain(_In_ HINSTANCE hinstDLL, _In_ DWORD fdwReason, _In_ LPVOID lpvReserved)
 {

api/entry.h

@@ -14,12 +14,24 @@
 #    define _L(x) __L(x)
 #endif
 
+/* TODO: Replace with is_defined. MSVC has issues with the linux kernel varadic macro trick for this. */
 #if defined(_M_IX86) || defined(_M_ARM)
-#define MAYBE_WOW64
+#    define MAYBE_WOW64 1
+#else
+#    define MAYBE_WOW64 0
 #endif
-#if defined(_M_AMD64) || defined(_M_ARM64) || defined(_DEBUG)
+#if defined(_M_AMD64) || defined(_M_ARM64)
-#define ACCEPT_WOW64
+#    define ACCEPT_WOW64 1
+#else
+#    define ACCEPT_WOW64 0
 #endif
+#ifdef HAVE_WHQL
+#    undef HAVE_WHQL
+#    define HAVE_WHQL 1
+#else
+#    define HAVE_WHQL 0
+#endif
+#pragma warning(disable : 4127) /* conditional expression is constant */
 
 extern HINSTANCE ResourceModule;
 extern HANDLE ModuleHeap;

api/rundll32.c

@@ -3,6 +3,10 @@
  * Copyright (C) 2018-2020 WireGuard LLC. All Rights Reserved.
  */
 
+#include "entry.h"
+
+#if ACCEPT_WOW64 == 1
+
 #include "adapter.h"
 #include "logger.h"
 #include "wintun.h"
@@ -14,8 +18,6 @@
 
 #define EXPORT comment(linker, "/EXPORT:" __FUNCTION__ "=" __FUNCDNAME__)
 
-#if defined(ACCEPT_WOW64) || defined(_DEBUG)
-
 static DWORD
 WriteFormatted(_In_ DWORD StdHandle, _In_z_ const WCHAR *Template, ...)
 {
@@ -147,5 +149,4 @@ VOID __stdcall DeleteDriver(HWND hwnd, HINSTANCE hinst, LPSTR lpszCmdLine, int n
     WriteFormatted(STD_OUTPUT_HANDLE, L"%1!X!", WintunDeleteDriver());
     Done();
 }
-
 #endif