mac: Add NotifyServer::DefaultInterface, a default no-op implementation

Each routine in this implementation returns MIG_BAD_ID. These routines
may be overridden.

Most things that implement NotifyServer::Interface will only need to
implement one of the interface routines. Since another user of
NotifyServer will be added soon, it makes sense to provide a default
no-op implementation rather than forcing everyone to write the same
no-op boilerplate repeatedly.

R=rsesek@chromium.org

Review URL: https://codereview.chromium.org/1414413006 .

handler/mac/exception_handler_server.cc

@@ -27,13 +27,13 @@ namespace crashpad {
 namespace {
 
 class ExceptionHandlerServerRun : public UniversalMachExcServer::Interface,
-                                  public NotifyServer::Interface {
+                                  public NotifyServer::DefaultInterface {
  public:
   ExceptionHandlerServerRun(
       mach_port_t exception_port,
       UniversalMachExcServer::Interface* exception_interface)
       : UniversalMachExcServer::Interface(),
-        NotifyServer::Interface(),
+        NotifyServer::DefaultInterface(),
         mach_exc_server_(this),
         notify_server_(this),
         composite_mach_message_server_(),
@@ -144,22 +144,7 @@ class ExceptionHandlerServerRun : public UniversalMachExcServer::Interface,
                                                     destroy_complex_request);
   }
 
-  // NotifyServer::Interface:
-
-  kern_return_t DoMachNotifyPortDeleted(
-      notify_port_t notify,
-      mach_port_name_t name,
-      const mach_msg_trailer_t* trailer) override {
-    return UnimplementedNotifyRoutine(notify);
-  }
-
-  kern_return_t DoMachNotifyPortDestroyed(notify_port_t notify,
-                                          mach_port_t rights,
-                                          const mach_msg_trailer_t* trailer,
-                                          bool* destroy_request) override {
-    *destroy_request = true;
-    return UnimplementedNotifyRoutine(notify);
-  }
+  // NotifyServer::DefaultInterface:
 
   kern_return_t DoMachNotifyNoSenders(
       notify_port_t notify,
@@ -180,32 +165,7 @@ class ExceptionHandlerServerRun : public UniversalMachExcServer::Interface,
     return KERN_SUCCESS;
   }
 
-  kern_return_t DoMachNotifySendOnce(
-      notify_port_t notify,
-      const mach_msg_trailer_t* trailer) override {
-    return UnimplementedNotifyRoutine(notify);
-  }
-
-  kern_return_t DoMachNotifyDeadName(
-      notify_port_t notify,
-      mach_port_name_t name,
-      const mach_msg_trailer_t* trailer) override {
-    return UnimplementedNotifyRoutine(notify);
-  }
-
  private:
-  kern_return_t UnimplementedNotifyRoutine(notify_port_t notify) {
-    // Most of the routines in the notify subsystem are not expected to be
-    // called.
-    if (notify != notify_port_) {
-      LOG(WARNING) << "notify port mismatch";
-      return KERN_FAILURE;
-    }
-
-    NOTREACHED();
-    return MIG_BAD_ID;
-  }
-
   UniversalMachExcServer mach_exc_server_;
   NotifyServer notify_server_;
   CompositeMachMessageServer composite_mach_message_server_;

util/mach/notify_server.cc

@@ -105,6 +105,42 @@ kern_return_t MIGCheckRequestMachNotifyDeadName(
 
 namespace crashpad {
 
+kern_return_t NotifyServer::DefaultInterface::DoMachNotifyPortDeleted(
+    notify_port_t notify,
+    mach_port_name_t name,
+    const mach_msg_trailer_t* trailer) {
+  return MIG_BAD_ID;
+}
+
+kern_return_t NotifyServer::DefaultInterface::DoMachNotifyPortDestroyed(
+    notify_port_t notify,
+    mach_port_t rights,
+    const mach_msg_trailer_t* trailer,
+    bool* destroy_request) {
+  *destroy_request = true;
+  return MIG_BAD_ID;
+}
+
+kern_return_t NotifyServer::DefaultInterface::DoMachNotifyNoSenders(
+    notify_port_t notify,
+    mach_port_mscount_t mscount,
+    const mach_msg_trailer_t* trailer) {
+  return MIG_BAD_ID;
+}
+
+kern_return_t NotifyServer::DefaultInterface::DoMachNotifySendOnce(
+    notify_port_t notify,
+    const mach_msg_trailer_t* trailer) {
+  return MIG_BAD_ID;
+}
+
+kern_return_t NotifyServer::DefaultInterface::DoMachNotifyDeadName(
+    notify_port_t notify,
+    mach_port_name_t name,
+    const mach_msg_trailer_t* trailer) {
+  return MIG_BAD_ID;
+}
+
 NotifyServer::NotifyServer(NotifyServer::Interface* interface)
     : MachMessageServer::Interface(),
       interface_(interface) {

util/mach/notify_server.h

@@ -37,6 +37,9 @@ class NotifyServer : public MachMessageServer::Interface {
  public:
   //! \brief An interface that the different request messages that are a part of
   //!     the `notify` Mach subsystem can be dispatched to.
+  //!
+  //! Default implementations of all methods are available in the
+  //! DefaultInterface class.
   class Interface {
    public:
     //! \brief Handles port-deleted notifications sent by
@@ -166,6 +169,52 @@ class NotifyServer : public MachMessageServer::Interface {
     ~Interface() {}
   };
 
+  //! \brief A concrete implementation of Interface that provides a default
+  //!     behavior for all `notify` routines.
+  //!
+  //! The Mach `notify` subsystem contains a collection of unrelated routines,
+  //! and a single server would rarely need to implement all of them. To make it
+  //! easier to use NotifyServer, a server can inherit from DefaultInterface
+  //! instead of Interface. Unless overridden, each routine in DefaultInterface
+  //! returns `MIG_BAD_ID` to indicate to the caller that the `notify` message
+  //! was unexpected and not processed.
+  class DefaultInterface : public Interface {
+   public:
+    // Interface:
+
+    kern_return_t DoMachNotifyPortDeleted(
+        notify_port_t notify,
+        mach_port_name_t name,
+        const mach_msg_trailer_t* trailer) override;
+
+    kern_return_t DoMachNotifyPortDestroyed(
+        notify_port_t notify,
+        mach_port_t rights,
+        const mach_msg_trailer_t* trailer,
+        bool* destroy_request) override;
+
+    kern_return_t DoMachNotifyNoSenders(
+        notify_port_t notify,
+        mach_port_mscount_t mscount,
+        const mach_msg_trailer_t* trailer) override;
+
+    kern_return_t DoMachNotifySendOnce(
+        notify_port_t notify,
+        const mach_msg_trailer_t* trailer) override;
+
+    kern_return_t DoMachNotifyDeadName(
+        notify_port_t notify,
+        mach_port_name_t name,
+        const mach_msg_trailer_t* trailer) override;
+
+   protected:
+    DefaultInterface() : Interface() {}
+    ~DefaultInterface() {}
+
+   private:
+    DISALLOW_COPY_AND_ASSIGN(DefaultInterface);
+  };
+
   //! \brief Constructs an object of this class.
   //!
   //! \param[in] interface The interface to dispatch requests to. Weak.