base-hw: do not inherit Kernel::Object

This prevents the use of Kernel::Object as base class for the specific kernel
objects and instead makes it a member of the kernel objects. Besides
simplifying inheritance hierarchies in base-hw, this prepares for the in-place
translation of the signaling module (and others) to Ada in the context of the
Spunky project.

Ref #3308

repos/base-hw/src/core/kernel/irq.h

@@ -119,10 +119,11 @@ class Kernel::Irq : Genode::Avl_node<Irq>
 };
 
 
-class Kernel::User_irq : public Kernel::Irq, public Kernel::Object
+class Kernel::User_irq : public Kernel::Irq
 {
 	private:
 
+		Kernel::Object  _kernel_object { *this };
 		Signal_context &_context;
 
 		/**
@@ -186,6 +187,8 @@ class Kernel::User_irq : public Kernel::Irq, public Kernel::Object
 		 */
 		static void syscall_destroy(Genode::Kernel_object<User_irq> &irq) {
 			call(call_id_delete_irq(), (Call_arg) &irq); }
+
+		Object &kernel_object() { return _kernel_object; }
 };
 
 #endif /* _CORE__KERNEL__IRQ_H_ */

repos/base-hw/src/core/kernel/object.cc

@@ -11,12 +11,99 @@ using namespace Kernel;
  ** Object **
  ************/
 
+Object::Object(Thread &obj)
+:
+	_type { THREAD },
+	_obj  { (void *)&obj }
+{ }
+
+Object::Object(Irq &obj)
+:
+	_type { IRQ },
+	_obj  { (void *)&obj }
+{ }
+
+Object::Object(Signal_receiver &obj)
+:
+	_type { SIGNAL_RECEIVER },
+	_obj  { (void *)&obj }
+{ }
+
+Object::Object(Signal_context &obj)
+:
+	_type { SIGNAL_CONTEXT },
+	_obj  { (void *)&obj }
+{ }
+
+Object::Object(Pd &obj)
+:
+	_type { PD },
+	_obj  { (void *)&obj }
+{ }
+
+Object::Object(Vm &obj)
+:
+	_type { VM },
+	_obj  { (void *)&obj }
+{ }
+
 Object::~Object()
 {
 	for (Object_identity * oi = first(); oi; oi = first())
 		oi->invalidate();
 }
 
+namespace Kernel {
+
+	template <> Pd *Object::obj<Pd>() const
+	{
+		if (_type != PD) {
+			return nullptr; }
+
+		return reinterpret_cast<Pd *>(_obj);
+	}
+
+	template <> Irq *Object::obj<Irq>() const
+	{
+		if (_type != IRQ) {
+			return nullptr; }
+
+		return reinterpret_cast<Irq *>(_obj);
+	}
+
+	template <> Signal_receiver *Object::obj<Signal_receiver>() const
+	{
+		if (_type != SIGNAL_RECEIVER) {
+			return nullptr; }
+
+		return reinterpret_cast<Signal_receiver *>(_obj);
+	}
+
+	template <> Signal_context *Object::obj<Signal_context>() const
+	{
+		if (_type != SIGNAL_CONTEXT) {
+			return nullptr; }
+
+		return reinterpret_cast<Signal_context *>(_obj);
+	}
+
+	template <> Thread *Object::obj<Thread>() const
+	{
+		if (_type != THREAD) {
+			return nullptr; }
+
+		return reinterpret_cast<Thread *>(_obj);
+	}
+
+	template <> Vm *Object::obj<Vm>() const
+	{
+		if (_type != VM) {
+			return nullptr; }
+
+		return reinterpret_cast<Vm *>(_obj);
+	}
+}
+
 
 /*********************
  ** Object_identity **

repos/base-hw/src/core/kernel/object.h

@@ -27,7 +27,16 @@
 
 namespace Kernel
 {
-	class Pd; /* forward declaration */
+	/*
+	 * Forward declarations
+	 */
+
+	class Pd;
+	class Irq;
+	class Thread;
+	class Signal_context;
+	class Signal_receiver;
+	class Vm;
 
 	/**
 	 * Base class of all Kernel objects
@@ -73,12 +82,39 @@ namespace Kernel
 }
 
 
-struct Kernel::Object : private Object_identity_list
+class Kernel::Object : private Object_identity_list
 {
-	using Object_identity_list::remove;
-	using Object_identity_list::insert;
+	private:
 
-	virtual ~Object();
+		enum Type { THREAD, PD, SIGNAL_RECEIVER, SIGNAL_CONTEXT, IRQ, VM };
+
+		/*
+		 * Noncopyable
+		 */
+		Object(Object const &)              = delete;
+		Object &operator = (Object const &) = delete;
+
+		Type  const _type;
+		void *const _obj;
+
+	public:
+
+		struct Cannot_cast_to_type : Genode::Exception { };
+
+		using Object_identity_list::remove;
+		using Object_identity_list::insert;
+
+		Object(Thread &obj);
+		Object(Irq &obj);
+		Object(Signal_receiver &obj);
+		Object(Signal_context &obj);
+		Object(Pd &obj);
+		Object(Vm &obj);
+
+		~Object();
+
+		template <typename T>
+		T *obj() const;
 };
 
 
@@ -102,7 +138,7 @@ class Kernel::Object_identity
 		~Object_identity();
 
 		template <typename KOBJECT>
-		KOBJECT * object() { return dynamic_cast<KOBJECT*>(_object); }
+		KOBJECT * object() { return _object->obj<KOBJECT>(); }
 
 		void invalidate();
 };
@@ -190,7 +226,7 @@ class Kernel::Core_object_identity : public Object_identity,
 	public:
 
 		Core_object_identity(T & object)
-		: Object_identity(object),
+		: Object_identity(object.kernel_object()),
 		  Object_identity_reference(this, core_pd()) { }
 
 		capid_t core_capid() { return capid(); }

repos/base-hw/src/core/kernel/pd.h

@@ -39,7 +39,7 @@ namespace Kernel
 }
 
 
-class Kernel::Pd : public Kernel::Object
+class Kernel::Pd
 {
 	public:
 
@@ -49,6 +49,7 @@ class Kernel::Pd : public Kernel::Object
 
 	private:
 
+		Kernel::Object                 _kernel_object { *this };
 		Hw::Page_table                &_table;
 		Genode::Platform_pd           &_platform_pd;
 		Capid_allocator                _capid_alloc { };
@@ -108,6 +109,7 @@ class Kernel::Pd : public Kernel::Object
 		 ** Accessors **
 		 ***************/
 
+		Object              &kernel_object()       { return _kernel_object; }
 		Genode::Platform_pd &platform_pd()         { return _platform_pd; }
 		Hw::Page_table      &translation_table()   { return _table;       }
 		Capid_allocator     &capid_alloc()         { return _capid_alloc; }
@@ -118,7 +120,7 @@ class Kernel::Pd : public Kernel::Object
 
 template<>
 inline Kernel::Core_object_identity<Kernel::Pd>::Core_object_identity(Kernel::Pd & pd)
-: Object_identity(pd),
+: Object_identity(pd.kernel_object()),
   Object_identity_reference(this, pd.core_pd() ? pd : core_pd()) { }
 
 #endif /* _CORE__KERNEL__PD_H_ */

repos/base-hw/src/core/kernel/signal_receiver.h

@@ -104,7 +104,7 @@ class Kernel::Signal_context_killer
 		void cancel_waiting();
 };
 
-class Kernel::Signal_context : public Kernel::Object
+class Kernel::Signal_context
 {
 	friend class Signal_receiver;
 	friend class Signal_context_killer;
@@ -119,14 +119,15 @@ class Kernel::Signal_context : public Kernel::Object
 
 		typedef Genode::Fifo_element<Signal_context> Fifo_element;
 
-		Fifo_element            _deliver_fe  { *this   };
-		Fifo_element            _contexts_fe { *this   };
+		Kernel::Object          _kernel_object { *this };
+		Fifo_element            _deliver_fe    { *this };
+		Fifo_element            _contexts_fe   { *this };
 		Signal_receiver &       _receiver;
 		addr_t const            _imprint;
-		Signal_context_killer * _killer      { nullptr };
-		unsigned                _submits     { 0       };
-		bool                    _ack         { true    };
-		bool                    _killed      { false   };
+		Signal_context_killer * _killer        { nullptr };
+		unsigned                _submits       { 0       };
+		bool                    _ack           { true    };
+		bool                    _killed        { false   };
 
 		/**
 		 * Tell receiver about the submits of the context if any
@@ -209,9 +210,11 @@ class Kernel::Signal_context : public Kernel::Object
 		 */
 		static void syscall_destroy(Genode::Kernel_object<Signal_context> &c) {
 			call(call_id_delete_signal_context(), (Call_arg)&c); }
+
+		Object &kernel_object() { return _kernel_object; }
 };
 
-class Kernel::Signal_receiver : public Kernel::Object
+class Kernel::Signal_receiver
 {
 	friend class Signal_context;
 	friend class Signal_handler;
@@ -222,9 +225,10 @@ class Kernel::Signal_receiver : public Kernel::Object
 
 		template <typename T> class Fifo : public Genode::Fifo<T> { };
 
-		Fifo<Signal_handler::Fifo_element> _handlers { };
-		Fifo<Signal_context::Fifo_element> _deliver  { };
-		Fifo<Signal_context::Fifo_element> _contexts { };
+		Kernel::Object                     _kernel_object { *this };
+		Fifo<Signal_handler::Fifo_element> _handlers      { };
+		Fifo<Signal_context::Fifo_element> _deliver       { };
+		Fifo<Signal_context::Fifo_element> _contexts      { };
 
 		/**
 		 * Recognize that context 'c' has submits to deliver
@@ -282,6 +286,8 @@ class Kernel::Signal_receiver : public Kernel::Object
 		 */
 		static void syscall_destroy(Genode::Kernel_object<Signal_receiver> &r) {
 			call(call_id_delete_signal_receiver(), (Call_arg)&r); }
+
+		Object &kernel_object() { return _kernel_object; }
 };
 
 #endif /* _CORE__KERNEL__SIGNAL_RECEIVER_H_ */

repos/base-hw/src/core/kernel/thread.cc

@@ -819,6 +819,7 @@ void Thread::_mmu_exception()
 Thread::Thread(unsigned const priority, unsigned const quota,
                char const * const label, bool core)
 :
+	Kernel::Object { *this },
 	Cpu_job(priority, quota), _ipc_node(*this), _state(AWAITS_START),
 	_signal_receiver(0), _label(label), _core(core), regs(core) { }
 

repos/base-hw/src/core/kernel/thread.h

@@ -56,9 +56,7 @@ struct Kernel::Thread_fault
 /**
  * Kernel back-end for userland execution-contexts
  */
-class Kernel::Thread
-:
-	public Kernel::Object, public Cpu_job, private Timeout
+class Kernel::Thread : private Kernel::Object, public Cpu_job, private Timeout
 {
 	private:
 
@@ -404,6 +402,7 @@ class Kernel::Thread
 		 ** Accessors **
 		 ***************/
 
+		Object &kernel_object() { return *this; }
 		char const * label() const { return _label; }
 		Thread_fault fault() const { return _fault; }
 		Genode::Native_utcb *utcb() { return _utcb; }

repos/base-hw/src/core/kernel/vm.h

@@ -33,8 +33,7 @@ namespace Kernel
 }
 
 
-class Kernel::Vm : public Cpu_job,
-                   public Kernel::Object
+class Kernel::Vm : public Cpu_job
 {
 	private:
 
@@ -48,6 +47,7 @@ class Kernel::Vm : public Cpu_job,
 
 		enum Scheduler_state { ACTIVE, INACTIVE };
 
+		Object                      _kernel_object { *this };
 		unsigned                    _id = 0;
 		State                     & _state;
 		Signal_context            & _context;
@@ -110,6 +110,7 @@ class Kernel::Vm : public Cpu_job,
 		static void syscall_destroy(Genode::Kernel_object<Vm> & vm) {
 			call(call_id_delete_vm(), (Call_arg) &vm); }
 
+		Object &kernel_object() { return _kernel_object; }
 
 		/****************
 		 ** Vm_session **