hooklib: add debugger trap defuser (thanks PockyWitch!)

hooklib/debug.c

@@ -0,0 +1,48 @@
+#include <windows.h>
+
+#include <assert.h>
+#include <stdbool.h>
+#include <stdlib.h>
+
+#include "hook/com-proxy.h"
+#include "hook/table.h"
+
+#include "hooklib/config.h"
+#include "hooklib/dll.h"
+#include "hooklib/debug.h"
+
+#include "util/dprintf.h"
+
+/* API hooks */
+
+static BOOL WINAPI hook_IsDebuggerPresent();
+
+static BOOL (WINAPI *next_IsDebuggerPresent)();
+
+/* Link pointers */
+
+static bool debug_hook_initted;
+
+static const struct hook_symbol debug_hooks[] = {
+    { .name = "IsDebuggerPresent",
+      .patch = hook_IsDebuggerPresent,
+      .link = (void **) &next_IsDebuggerPresent },
+};
+
+void debug_hook_init()
+{
+    if (debug_hook_initted) {
+        return;
+    }
+
+    debug_hook_initted = true;
+
+    hook_table_apply(NULL, "kernel32.dll", debug_hooks, _countof(debug_hooks));
+    dprintf("debug: hook enabled.\n");
+}
+
+BOOL WINAPI hook_IsDebuggerPresent()
+{
+    dprintf("debug: IsDebuggerPresent hooked.\n");
+    return false;
+}