1 files changed, 176 insertions, 0 deletions
diff --git a/dom/media/doctor/DecoderDoctorLogger.cpp b/dom/media/doctor/DecoderDoctorLogger.cpp
new file mode 100644
index 0000000000..927650babc
--- /dev/null
+++ b/dom/media/doctor/DecoderDoctorLogger.cpp
@@ -0,0 +1,176 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim:set ts=2 sw=2 sts=2 et cindent: */
+/* 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 "DecoderDoctorLogger.h"
+
+#include "DDLogUtils.h"
+#include "DDMediaLogs.h"
+#include "mozilla/ClearOnShutdown.h"
+#include "mozilla/SchedulerGroup.h"
+#include "mozilla/Unused.h"
+
+namespace mozilla {
+
+/* static */ Atomic<DecoderDoctorLogger::LogState, ReleaseAcquire>
+    DecoderDoctorLogger::sLogState{DecoderDoctorLogger::scDisabled};
+
+/* static */ const char* DecoderDoctorLogger::sShutdownReason = nullptr;
+
+static DDMediaLogs* sMediaLogs;
+
+/* static */
+void DecoderDoctorLogger::Init() {
+  MOZ_ASSERT(static_cast<LogState>(sLogState) == scDisabled);
+  if (MOZ_LOG_TEST(sDecoderDoctorLoggerLog, LogLevel::Error) ||
+      MOZ_LOG_TEST(sDecoderDoctorLoggerEndLog, LogLevel::Error)) {
+    EnableLogging();
+  }
+}
+
+// First DDLogShutdowner sets sLogState to scShutdown, to prevent further
+// logging.
+struct DDLogShutdowner {
+  ~DDLogShutdowner() {
+    DDL_INFO("Shutting down");
+    // Prevent further logging, some may racily seep in, it's fine as the
+    // logging infrastructure would still be alive until DDLogDeleter runs.
+    DecoderDoctorLogger::ShutdownLogging();
+  }
+};
+static UniquePtr<DDLogShutdowner> sDDLogShutdowner;
+
+// Later DDLogDeleter will delete the message queue and media logs.
+struct DDLogDeleter {
+  ~DDLogDeleter() {
+    if (sMediaLogs) {
+      DDL_INFO("Final processing of collected logs");
+      delete sMediaLogs;
+      sMediaLogs = nullptr;
+    }
+  }
+};
+static UniquePtr<DDLogDeleter> sDDLogDeleter;
+
+/* static */
+void DecoderDoctorLogger::PanicInternal(const char* aReason, bool aDontBlock) {
+  for (;;) {
+    const LogState state = static_cast<LogState>(sLogState);
+    if (state == scEnabling && !aDontBlock) {
+      // Wait for the end of the enabling process (unless we're in it, in which
+      // case we don't want to block.)
+      continue;
+    }
+    if (state == scShutdown) {
+      // Already shutdown, nothing more to do.
+      break;
+    }
+    if (sLogState.compareExchange(state, scShutdown)) {
+      // We are the one performing the first shutdown -> Record reason.
+      sShutdownReason = aReason;
+      // Free as much memory as possible.
+      if (sMediaLogs) {
+        // Shutdown the medialogs processing thread, and free as much memory
+        // as possible.
+        sMediaLogs->Panic();
+      }
+      // sMediaLogs and sQueue will be deleted by DDLogDeleter.
+      // We don't want to delete them right now, because there could be a race
+      // where another thread started logging or retrieving logs before we
+      // changed the state to scShutdown, but has been delayed before actually
+      // trying to write or read log messages, thereby causing a UAF.
+    }
+    // If someone else changed the state, we'll just loop around, and either
+    // shutdown already happened elsewhere, or we'll try to shutdown again.
+  }
+}
+
+/* static */
+bool DecoderDoctorLogger::EnsureLogIsEnabled() {
+#ifdef RELEASE_OR_BETA
+  // Just refuse to enable DDLogger on release&beta because it makes it too easy
+  // to trigger an OOM. See bug 1571648.
+  return false;
+#else
+  for (;;) {
+    LogState state = static_cast<LogState>(sLogState);
+    switch (state) {
+      case scDisabled:
+        // Currently disabled, try to be the one to enable.
+        if (sLogState.compareExchange(scDisabled, scEnabling)) {
+          // We are the one to enable logging, state won't change (except for
+          // possible shutdown.)
+          // Create DDMediaLogs singleton, which will process the message queue.
+          DDMediaLogs::ConstructionResult mediaLogsConstruction =
+              DDMediaLogs::New();
+          if (NS_FAILED(mediaLogsConstruction.mRv)) {
+            PanicInternal("Failed to enable logging", /* aDontBlock */ true);
+            return false;
+          }
+          MOZ_ASSERT(mediaLogsConstruction.mMediaLogs);
+          sMediaLogs = mediaLogsConstruction.mMediaLogs;
+          // Setup shutdown-time clean-up.
+          MOZ_ALWAYS_SUCCEEDS(SchedulerGroup::Dispatch(
+              TaskCategory::Other,
+              NS_NewRunnableFunction("DDLogger shutdown setup", [] {
+                sDDLogShutdowner = MakeUnique<DDLogShutdowner>();
+                ClearOnShutdown(&sDDLogShutdowner,
+                                ShutdownPhase::XPCOMShutdown);
+                sDDLogDeleter = MakeUnique<DDLogDeleter>();
+                ClearOnShutdown(&sDDLogDeleter,
+                                ShutdownPhase::XPCOMShutdownThreads);
+              })));
+
+          // Nobody else should change the state when *we* are enabling logging.
+          MOZ_ASSERT(sLogState == scEnabling);
+          sLogState = scEnabled;
+          DDL_INFO("Logging enabled");
+          return true;
+        }
+        // Someone else changed the state before our compareExchange, just loop
+        // around to examine the new situation.
+        break;
+      case scEnabled:
+        return true;
+      case scEnabling:
+        // Someone else is currently enabling logging, actively wait by just
+        // looping, until the state changes.
+        break;
+      case scShutdown:
+        // Shutdown is non-recoverable, we cannot enable logging again.
+        return false;
+    }
+    // Not returned yet, loop around to examine the new situation.
+  }
+#endif
+}
+
+/* static */
+void DecoderDoctorLogger::EnableLogging() { Unused << EnsureLogIsEnabled(); }
+
+/* static */ RefPtr<DecoderDoctorLogger::LogMessagesPromise>
+DecoderDoctorLogger::RetrieveMessages(
+    const dom::HTMLMediaElement* aMediaElement) {
+  if (MOZ_UNLIKELY(!EnsureLogIsEnabled())) {
+    DDL_WARN("Request (for %p) but there are no logs", aMediaElement);
+    return DecoderDoctorLogger::LogMessagesPromise::CreateAndReject(
+        NS_ERROR_DOM_MEDIA_ABORT_ERR, __func__);
+  }
+  return sMediaLogs->RetrieveMessages(aMediaElement);
+}
+
+/* static */
+void DecoderDoctorLogger::Log(const char* aSubjectTypeName,
+                              const void* aSubjectPointer,
+                              DDLogCategory aCategory, const char* aLabel,
+                              DDLogValue&& aValue) {
+  if (IsDDLoggingEnabled()) {
+    MOZ_ASSERT(sMediaLogs);
+    sMediaLogs->Log(aSubjectTypeName, aSubjectPointer, aCategory, aLabel,
+                    std::move(aValue));
+  }
+}
+
+}  // namespace mozilla