1 files changed, 60 insertions, 0 deletions
diff --git a/toolkit/xre/dllservices/mozglue/CacheNtDllThunk.cpp b/toolkit/xre/dllservices/mozglue/CacheNtDllThunk.cpp
new file mode 100644
index 0000000000..f3eef13504
--- /dev/null
+++ b/toolkit/xre/dllservices/mozglue/CacheNtDllThunk.cpp
@@ -0,0 +1,60 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "CacheNtDllThunk.h"
+
+#include "mozilla/Maybe.h"
+#include "mozilla/Span.h"
+#include "mozilla/StaticPtr.h"
+
+namespace mozilla {
+
+static StaticAutoPtr<Buffer<IMAGE_THUNK_DATA>> sCachedNtDllThunk;
+
+// This static method initializes sCachedNtDllThunk.  Because it's called in
+// XREMain::XRE_main, which happens long before WindowsProcessLauncher's ctor
+// accesses sCachedNtDllThunk, there is no race on sCachedNtDllThunk, thus
+// no mutex is needed.
+static void CacheNtDllThunk() {
+  if (sCachedNtDllThunk) {
+    return;
+  }
+
+  do {
+    nt::PEHeaders ourExeImage(::GetModuleHandleW(nullptr));
+    if (!ourExeImage) {
+      break;
+    }
+
+    nt::PEHeaders ntdllImage(::GetModuleHandleW(L"ntdll.dll"));
+    if (!ntdllImage) {
+      break;
+    }
+
+    Maybe<Range<const uint8_t>> ntdllBoundaries = ntdllImage.GetBounds();
+    if (!ntdllBoundaries) {
+      break;
+    }
+
+    Maybe<Span<IMAGE_THUNK_DATA>> maybeNtDllThunks =
+        ourExeImage.GetIATThunksForModule("ntdll.dll", ntdllBoundaries.ptr());
+    if (maybeNtDllThunks.isNothing()) {
+      break;
+    }
+
+    sCachedNtDllThunk = new Buffer<IMAGE_THUNK_DATA>(maybeNtDllThunks.value());
+    return;
+  } while (false);
+
+  // Failed to cache IAT.  Initializing the variable with nullptr.
+  sCachedNtDllThunk = new Buffer<IMAGE_THUNK_DATA>();
+}
+
+static Buffer<IMAGE_THUNK_DATA>* GetCachedNtDllThunk() {
+  return sCachedNtDllThunk;
+}
+
+}  // namespace mozilla