1 files changed, 92 insertions, 0 deletions
diff --git a/dom/ipc/MMPrinter.cpp b/dom/ipc/MMPrinter.cpp
new file mode 100644
index 0000000000..be2911341a
--- /dev/null
+++ b/dom/ipc/MMPrinter.cpp
@@ -0,0 +1,92 @@
+/* -*- 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 "MMPrinter.h"
+
+#include "jsapi.h"
+#include "nsJSUtils.h"
+#include "Logging.h"
+#include "mozilla/Bootstrap.h"
+#include "mozilla/dom/ipc/StructuredCloneData.h"
+#include "mozilla/dom/ScriptSettings.h"
+#include "mozilla/ErrorResult.h"
+#include "mozilla/RandomNum.h"
+#include "nsFrameMessageManager.h"
+#include "prenv.h"
+
+namespace mozilla::dom {
+
+LazyLogModule MMPrinter::sMMLog("MessageManager");
+
+// You can use
+// https://gist.github.com/tomrittervg/adb8688426a9a5340da96004e2c8af79 to parse
+// the output of the logs into logs more friendly to reading.
+
+/* static */
+void MMPrinter::PrintImpl(char const* aLocation, const nsAString& aMsg,
+                          ClonedMessageData const& aData) {
+  NS_ConvertUTF16toUTF8 charMsg(aMsg);
+
+  /*
+   * The topic will be skipped if the topic name appears anywhere as a substring
+   * of the filter.
+   *
+   * Example:
+   *   MOZ_LOG_MESSAGEMANAGER_SKIP="foobar|extension"
+   *     Will  match the topics 'foobar', 'foo', 'bar', and 'ten' (even though
+   * you may not have intended to match the latter three) and it will not match
+   * the topics 'extensionresult' or 'Foo'.
+   */
+  char* mmSkipLog = PR_GetEnv("MOZ_LOG_MESSAGEMANAGER_SKIP");
+
+  if (mmSkipLog && strstr(mmSkipLog, charMsg.get())) {
+    return;
+  }
+
+  uint64_t msg_id = RandomUint64OrDie();
+
+  MOZ_LOG(MMPrinter::sMMLog, LogLevel::Debug,
+          ("%" PRIu64 " %s Message: %s in process type: %s", msg_id, aLocation,
+           charMsg.get(), XRE_GetProcessTypeString()));
+
+  if (!MOZ_LOG_TEST(sMMLog, LogLevel::Verbose)) {
+    return;
+  }
+
+  ErrorResult rv;
+
+  AutoJSAPI jsapi;
+  // We're using this context to deserialize, stringify, and print a message
+  // manager message here. Since the messages are always sent from and to system
+  // scopes, we need to do this in a system scope, or attempting to deserialize
+  // certain privileged objects will fail.
+  MOZ_ALWAYS_TRUE(jsapi.Init(xpc::PrivilegedJunkScope()));
+  JSContext* cx = jsapi.cx();
+
+  ipc::StructuredCloneData data;
+  ipc::UnpackClonedMessageData(aData, data);
+
+  /* Read original StructuredCloneData. */
+  JS::Rooted<JS::Value> scdContent(cx);
+  data.Read(cx, &scdContent, rv);
+  if (rv.Failed()) {
+    // In testing, the only reason this would fail was if there was no data in
+    // the message; so it seems like this is safe-ish.
+    MOZ_LOG(MMPrinter::sMMLog, LogLevel::Verbose,
+            ("%" PRIu64 " (No Data)", msg_id));
+    rv.SuppressException();
+    return;
+  }
+
+  JS::Rooted<JSString*> unevalObj(cx, JS_ValueToSource(cx, scdContent));
+  nsAutoJSString srcString;
+  if (!srcString.init(cx, unevalObj)) return;
+
+  MOZ_LOG(MMPrinter::sMMLog, LogLevel::Verbose,
+          ("%" PRIu64 " %s", msg_id, NS_ConvertUTF16toUTF8(srcString).get()));
+}
+
+}  // namespace mozilla::dom