Allow mojo_runner to connect to arbitrary executables.

mojo/runner/child/runner_connection.cc

+// Copyright 2015 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 "mojo/runner/child/runner_connection.h"
+
+#include "base/bind.h"
+#include "base/callback.h"
+#include "base/command_line.h"
+#include "base/memory/ref_counted.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/thread_task_runner_handle.h"
+#include "base/threading/thread.h"
+#include "base/threading/thread_checker.h"
+#include "mojo/message_pump/message_pump_mojo.h"
+#include "mojo/public/cpp/bindings/binding.h"
+#include "mojo/runner/child/child_controller.mojom.h"
+#include "third_party/mojo/src/mojo/edk/embedder/embedder.h"
+#include "third_party/mojo/src/mojo/edk/embedder/platform_channel_pair.h"
+#include "third_party/mojo/src/mojo/edk/embedder/scoped_platform_handle.h"
+
+namespace mojo {
+namespace runner {
+namespace {
+
+// Blocks a thread until another thread unblocks it, at which point it unblocks
+// and runs a closure provided by that thread.
+class Blocker {
+ public:
+  class Unblocker {
+   public:
+    explicit Unblocker(Blocker* blocker = nullptr) : blocker_(blocker) {}
+    ~Unblocker() {}
+
+    void Unblock(base::Closure run_after) {
+      DCHECK(blocker_);
+      DCHECK(blocker_->run_after_.is_null());
+      blocker_->run_after_ = run_after;
+      blocker_->event_.Signal();
+      blocker_ = nullptr;
+    }
+
+   private:
+    Blocker* blocker_;
+
+    // Copy and assign allowed.
+  };
+
+  Blocker() : event_(true, false) {}
+  ~Blocker() {}
+
+  void Block() {
+    DCHECK(run_after_.is_null());
+    event_.Wait();
+    if (!run_after_.is_null())
+      run_after_.Run();
+  }
+
+  Unblocker GetUnblocker() { return Unblocker(this); }
+
+ private:
+  base::WaitableEvent event_;
+  base::Closure run_after_;
+
+  DISALLOW_COPY_AND_ASSIGN(Blocker);
+};
+
+using GotApplicationRequestCallback =
+    base::Callback<void(InterfaceRequest<Application>)>;
+
+void OnGotApplicationRequest(InterfaceRequest<Application>* out_request,
+                             InterfaceRequest<Application> request) {
+  *out_request = request.Pass();
+}
+
+class ChildControllerImpl;
+
+class RunnerConnectionImpl : public RunnerConnection {
+ public:
+  RunnerConnectionImpl() : controller_thread_("controller_thread") {
+    StartControllerThread();
+  }
+  ~RunnerConnectionImpl() override {
+    controller_runner_->PostTask(
+        FROM_HERE, base::Bind(&RunnerConnectionImpl::ShutdownOnControllerThread,
+                              base::Unretained(this)));
+    controller_thread_.Stop();
+  }
+
+  // Returns true if a connection to the runner has been established and
+  // |request| has been modified, false if no connection was established.
+  bool WaitForApplicationRequest(InterfaceRequest<Application>* request);
+
+  ChildControllerImpl* controller() const { return controller_.get(); }
+
+  void set_controller(scoped_ptr<ChildControllerImpl> controller) {
+    controller_ = controller.Pass();
+  }
+
+ private:
+  void StartControllerThread() {
+    base::Thread::Options controller_thread_options;
+    controller_thread_options.message_loop_type =
+        base::MessageLoop::TYPE_CUSTOM;
+    controller_thread_options.message_pump_factory =
+        base::Bind(&common::MessagePumpMojo::Create);
+    CHECK(controller_thread_.StartWithOptions(controller_thread_options));
+    controller_runner_ = controller_thread_.task_runner().get();
+    CHECK(controller_runner_.get());
+  }
+
+  void ShutdownOnControllerThread() { controller_.reset(); }
+
+  base::Thread controller_thread_;
+  scoped_refptr<base::SingleThreadTaskRunner> controller_runner_;
+
+  // Accessed only on the controller thread.
+  scoped_ptr<ChildControllerImpl> controller_;
+
+  DISALLOW_COPY_AND_ASSIGN(RunnerConnectionImpl);
+};
+
+class ChildControllerImpl : public ChildController {
+ public:
+  ~ChildControllerImpl() override {
+    DCHECK(thread_checker_.CalledOnValidThread());
+
+    // TODO(vtl): Pass in the result from |MainMain()|.
+    on_app_complete_.Run(MOJO_RESULT_UNIMPLEMENTED);
+  }
+
+  // To be executed on the controller thread. Creates the |ChildController|,
+  // etc.
+  static void Create(RunnerConnectionImpl* connection,
+                     const GotApplicationRequestCallback& callback,
+                     embedder::ScopedPlatformHandle platform_channel,
+                     const Blocker::Unblocker& unblocker) {
+    DCHECK(connection);
+    DCHECK(platform_channel.is_valid());
+
+    DCHECK(!connection->controller());
+
+    scoped_ptr<ChildControllerImpl> impl(
+        new ChildControllerImpl(connection, callback, unblocker));
+
+    ScopedMessagePipeHandle host_message_pipe(embedder::CreateChannel(
+        platform_channel.Pass(),
+        base::Bind(&ChildControllerImpl::DidCreateChannel,
+                   base::Unretained(impl.get())),
+        base::ThreadTaskRunnerHandle::Get()));
+
+    impl->Bind(host_message_pipe.Pass());
+
+    connection->set_controller(impl.Pass());
+  }
+
+  void Bind(ScopedMessagePipeHandle handle) { binding_.Bind(handle.Pass()); }
+
+  void OnConnectionError() {
+    // A connection error means the connection to the shell is lost. This is not
+    // recoverable.
+    LOG(ERROR) << "Connection error to the shell.";
+    _exit(1);
+  }
+
+  // |ChildController| methods:
+  void StartApp(InterfaceRequest<Application> application_request,
+                const StartAppCallback& on_app_complete) override {
+    DCHECK(thread_checker_.CalledOnValidThread());
+
+    on_app_complete_ = on_app_complete;
+    unblocker_.Unblock(
+        base::Bind(&ChildControllerImpl::ReturnApplicationRequestOnMainThread,
+                   callback_, base::Passed(&application_request)));
+  }
+
+  void ExitNow(int32_t exit_code) override {
+    DVLOG(2) << "ChildControllerImpl::ExitNow(" << exit_code << ")";
+    _exit(exit_code);
+  }
+
+ private:
+  ChildControllerImpl(RunnerConnectionImpl* connection,
+                      const GotApplicationRequestCallback& callback,
+                      const Blocker::Unblocker& unblocker)
+      : connection_(connection),
+        callback_(callback),
+        unblocker_(unblocker),
+        channel_info_(nullptr),
+        binding_(this) {
+    binding_.set_connection_error_handler([this]() { OnConnectionError(); });
+  }
+
+  // Callback for |embedder::CreateChannel()|.
+  void DidCreateChannel(embedder::ChannelInfo* channel_info) {
+    DVLOG(2) << "ChildControllerImpl::DidCreateChannel()";
+    DCHECK(thread_checker_.CalledOnValidThread());
+    channel_info_ = channel_info;
+  }
+
+  static void ReturnApplicationRequestOnMainThread(
+      const GotApplicationRequestCallback& callback,
+      InterfaceRequest<Application> application_request) {
+    callback.Run(application_request.Pass());
+  }
+
+  base::ThreadChecker thread_checker_;
+  RunnerConnectionImpl* const connection_;
+  GotApplicationRequestCallback callback_;
+  Blocker::Unblocker unblocker_;
+  StartAppCallback on_app_complete_;
+
+  embedder::ChannelInfo* channel_info_;
+  Binding<ChildController> binding_;
+
+  DISALLOW_COPY_AND_ASSIGN(ChildControllerImpl);
+};
+
+bool RunnerConnectionImpl::WaitForApplicationRequest(
+    InterfaceRequest<Application>* request) {
+  embedder::ScopedPlatformHandle platform_channel =
+      embedder::PlatformChannelPair::PassClientHandleFromParentProcess(
+          *base::CommandLine::ForCurrentProcess());
+  if (!platform_channel.is_valid())
+    return false;
+
+  Blocker blocker;
+  controller_runner_->PostTask(
+      FROM_HERE,
+      base::Bind(
+          &ChildControllerImpl::Create, base::Unretained(this),
+          base::Bind(&OnGotApplicationRequest, base::Unretained(request)),
+          base::Passed(&platform_channel), blocker.GetUnblocker()));
+  blocker.Block();
+
+  return true;
+}
+
+}  // namespace
+
+RunnerConnection::~RunnerConnection() {}
+
+// static
+RunnerConnection* RunnerConnection::ConnectToRunner(
+    InterfaceRequest<Application>* request) {
+  RunnerConnectionImpl* connection = new RunnerConnectionImpl;
+  if (!connection->WaitForApplicationRequest(request)) {
+    delete connection;
+    return nullptr;
+  }
+  return connection;
+}
+
+RunnerConnection::RunnerConnection() {}
+
+}  // namespace runner
+}  // namespace mojo