arc: enable Android tracing in verified-boot mode

chromeos/dbus/arc_trace_agent.cc

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "chromeos/dbus/arc_trace_agent.h"
+
+#include <string>
+#include <utility>

[Yusuke Sato, 2017/01/04 23:55:47]

unused?

[Earl Ou, 2017/01/16 14:05:41]

Done.

+
+#include "base/callback_helpers.h"
+#include "base/logging.h"
+#include "base/memory/ptr_util.h"
+#include "base/memory/ref_counted.h"

[Yusuke Sato, 2017/01/04 23:55:47]

remove (see my comment on the header side)

[Earl Ou, 2017/01/16 14:05:42]

It's only used in this cc file now.

+#include "base/threading/thread_task_runner_handle.h"
+#include "chromeos/dbus/dbus_thread_manager.h"
+#include "chromeos/dbus/pipe_reader.h"
+#include "dbus/bus.h"
+#include "dbus/message.h"
+#include "dbus/object_path.h"
+#include "dbus/object_proxy.h"
+#include "third_party/cros_system_api/dbus/service_constants.h"
+
+namespace chromeos {
+
+namespace {
+
+constexpr char kArcTracingAgentName[] = "arc";
+constexpr char kArcTraceLabel[] = "ArcTraceEvents";
+
+void OnStart(const ArcTraceAgent::StartAgentTracingCallback& callback,
+             dbus::Response* response) {
+  if (!response)
+    LOG(ERROR) << "Failed to request start";
+  // Use PostTask as the convention of TraceAgent. The caller expects callback
+  // to be called after StartAgentTracing() returns.
+  base::ThreadTaskRunnerHandle::Get()->PostTask(
+      FROM_HERE,
+      base::Bind(callback, kArcTracingAgentName, response != nullptr));
+}
+
+// A wrapper for controlling system tracing on Chrome OS.
+class ArcTraceAgentImpl : public ArcTraceAgent {
+ public:
+  ArcTraceAgentImpl() : debugdaemon_proxy_(nullptr), weak_ptr_factory_(this) {}
+
+  ~ArcTraceAgentImpl() override = default;
+
+  // base::trace_event::TracingAgent overrides:
+  std::string GetTracingAgentName() override { return kArcTracingAgentName; }
+
+  std::string GetTraceEventLabel() override { return kArcTraceLabel; }
+
+  void StartAgentTracing(const base::trace_event::TraceConfig& trace_config,
+                         const StartAgentTracingCallback& callback) override {
+    // delegate_ may be nullptr if ARC is not enabled on the system. In such

[Yusuke Sato, 2017/01/04 23:55:47]

Apparently delegate_ is not initialized in the ctor? Please do.

[Earl Ou, 2017/01/16 14:05:42]

Done.

+    // case, simply do nothing.
+    if (!delegate_) {
+      // Use PostTask as the convention of TraceAgent. The caller expects
+      // callback to be called after this function returns.
+      base::ThreadTaskRunnerHandle::Get()->PostTask(
+          FROM_HERE, base::Bind(callback, GetTracingAgentName(), false));
+      return;
+    }
+
+    delegate_->StartTracing(trace_config);
+
+    dbus::MethodCall method_call(debugd::kDebugdInterface, "ArcTraceStart");
+    debugdaemon_proxy_->CallMethod(&method_call,
+                                   dbus::ObjectProxy::TIMEOUT_USE_DEFAULT,
+                                   base::Bind(&OnStart, callback));
+  }
+
+  void StopAgentTracing(const StopAgentTracingCallback& callback) override {
+    DCHECK(stop_agent_tracing_task_runner_);
+
+    if (!stop_callback_.is_null()) {
+      LOG(ERROR) << "Previous StopAgentTracing() invocation is still pending.";
+      return;
+    }
+
+    if (!delegate_) {
+      std::string no_data;
+      callback.Run(GetTracingAgentName(), GetTraceEventLabel(),
+                   base::RefCountedString::TakeString(&no_data));
+      return;
+    }
+
+    stop_callback_ = callback;

[Yusuke Sato, 2017/01/04 23:55:47]

Can't we pass the |callback| directly to OnIOComplete at L94? (Is the check at
L76 important here?)

[Earl Ou, 2017/01/16 14:05:41]

Done.

+
+    delegate_->StopTracing();
+
+    pipe_reader_ = base::MakeUnique<PipeReaderForString>(
+        stop_agent_tracing_task_runner_,
+        base::Bind(&ArcTraceAgentImpl::OnIOComplete,
+                   weak_ptr_factory_.GetWeakPtr()));
+
+    // PIPE reader will run on the given thread
+    // stop_agent_tracing_task_runner_, which should be an I/O thread given by
+    // the caller.
+    base::ScopedFD pipe_write_end = pipe_reader_->StartIO();
+    DCHECK(pipe_write_end.is_valid());
+    // Issue the dbus request to stop system tracing
+    dbus::MethodCall method_call(debugd::kDebugdInterface, "ArcTraceStop");
+    dbus::MessageWriter writer(&method_call);
+    writer.AppendFileDescriptor(pipe_write_end.get());
+
+    debugdaemon_proxy_->CallMethod(
+        &method_call, dbus::ObjectProxy::TIMEOUT_USE_DEFAULT,
+        base::Bind(&ArcTraceAgentImpl::OnStopAgentTracing,
+                   weak_ptr_factory_.GetWeakPtr()));
+  }
+
+  // ArcTraceAgent overrides:
+  void SetDelegate(Delegate* delegate) override { delegate_ = delegate; }
+
+  void SetStopAgentTracingTaskRunner(
+      scoped_refptr<base::TaskRunner> task_runner) override {
+    stop_agent_tracing_task_runner_ = task_runner;
+  }
+
+ protected:
+  // DBusClient overrides:
+  void Init(dbus::Bus* bus) override {
+    debugdaemon_proxy_ =
+        bus->GetObjectProxy(debugd::kDebugdServiceName,
+                            dbus::ObjectPath(debugd::kDebugdServicePath));
+  }
+
+ private:
+  // Called when pipe I/O completes; pass data on and delete the instance.
+  void OnIOComplete() {
+    std::string pipe_data;
+    pipe_reader_->GetData(&pipe_data);
+    pipe_reader_.reset();
+    base::ResetAndReturn(&stop_callback_)
+        .Run(kArcTracingAgentName, kArcTraceLabel,
+             base::RefCountedString::TakeString(&pipe_data));
+  }
+
+  void OnStopAgentTracing(dbus::Response* response) {
+    if (!response) {
+      LOG(ERROR) << "Failed to request arc stop";
+      // If debugd crashes or completes I/O before this message is processed
+      // then pipe_reader_ can be nullptr, see OnIOComplete().
+      if (pipe_reader_.get())
+        pipe_reader_->OnDataReady(-1);  // terminate data stream
+    }
+    // NB: requester is signaled when I/O completes
+  }
+
+  Delegate* delegate_;                    // Owned by ArcServiceLauncher.
+  dbus::ObjectProxy* debugdaemon_proxy_;  // Owned by dbus::Bus.
+  std::unique_ptr<PipeReaderForString> pipe_reader_;
+  scoped_refptr<base::TaskRunner> stop_agent_tracing_task_runner_;
+  StopAgentTracingCallback stop_callback_;
+  base::WeakPtrFactory<ArcTraceAgentImpl> weak_ptr_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(ArcTraceAgentImpl);
+};
+
+}  // namespace
+
+// static
+ArcTraceAgent* ArcTraceAgent::Create() {
+  return new ArcTraceAgentImpl();
+}
+
+ArcTraceAgent::ArcTraceAgent() = default;
+
+ArcTraceAgent::~ArcTraceAgent() = default;
+
+}  // namespace chromeos