ntdll: Mark the Wow64 TLS slots as reserved.

dlls/ntdll/loader.c

@@ -4176,7 +4176,8 @@ void WINAPI LdrInitializeThunk( CONTEXT *context, ULONG_PTR unknown2, ULONG_PTR
         RtlInitializeBitMap( &tls_bitmap, peb->TlsBitmapBits, sizeof(peb->TlsBitmapBits) * 8 );
         RtlInitializeBitMap( &tls_expansion_bitmap, peb->TlsExpansionBitmapBits,
                              sizeof(peb->TlsExpansionBitmapBits) * 8 );
-        RtlSetBits( peb->TlsBitmap, 0, 1 ); /* TLS index 0 is reserved and should be initialized to NULL. */
+        /* TLS index 0 is always reserved, and wow64 reserves extra TLS entries */
+        RtlSetBits( peb->TlsBitmap, 0, NtCurrentTeb()->WowTebOffset ? WOW64_TLS_MAX_NUMBER : 1 );
 
         init_user_process_params();
         load_global_options();

include/winternl.h

@@ -1084,6 +1084,7 @@ typedef struct _TEB64
 #define WOW64_TLS_TEMPLIST         3
 #define WOW64_TLS_USERCALLBACKDATA 5
 #define WOW64_TLS_FILESYSREDIR     8
+#define WOW64_TLS_MAX_NUMBER       19
 
 
 /***********************************************************************