Make local capability interface explicit. Fix #139.

Introduce a factory-, and dereference method for local capabilities. These are
capabilities that reference objects of services, which are known to be used
protection-domain internally only. To support the new Capability class methods
a protected constructor and accessor to the local object's pointer is needed
in the platform's capability base-classes. For further discussion details please
refer issue #139.

base-codezero/include/base/native_types.h

@@ -112,6 +112,11 @@ namespace Genode {
 			Native_thread_id _tid;  /* global thread ID */
 			int _local_name;        /* global unique object ID */
 
+		protected:
+
+			Native_capability(void* ptr) : _local_name((int)ptr) {
+				_tid.tid = Codezero::NILTHREAD; }
+
 		public:
 
 			/**
@@ -131,6 +136,7 @@ namespace Genode {
 			bool valid() const { return _tid.tid != Codezero::NILTHREAD; }
 
 			int local_name() const { return _local_name; }
+			void* local() const { return (void*)_local_name;  }
 			int dst() const { return _tid.tid; }
 
 			Native_thread_id tid() const { return _tid; }

base-fiasco/include/base/native_types.h

@@ -74,6 +74,11 @@ namespace Genode {
 			Fiasco::l4_threadid_t _tid;
 			long                  _local_name;
 
+		protected:
+
+			Native_capability(void *ptr)
+			: _tid(Fiasco::invalid_l4_threadid_t()), _local_name((long)ptr) { }
+
 		public:
 
 			/**
@@ -85,6 +90,8 @@ namespace Genode {
 			long local_name() const { return _local_name; }
 			Fiasco::l4_threadid_t dst() const { return _tid; }
 
+			void* local() const { return (void*)_local_name;  }
+
 			bool valid() const { return l4_is_invalid_id(_tid) == 0; }
 
 

base-foc/include/base/native_types.h

@@ -60,6 +60,10 @@ namespace Genode {
 			Native_thread _cap_sel;
 			int           _unique_id;
 
+		protected:
+
+			Native_capability(void* ptr) : _unique_id((int)ptr) { }
+
 		public:
 
 			/**
@@ -73,9 +77,10 @@ namespace Genode {
 			Native_capability(Native_thread cap_sel, int unique_id)
 			: _cap_sel(cap_sel), _unique_id(unique_id) { }
 
-			int              local_name() const { return _unique_id; }
-			Native_thread    dst()        const { return _cap_sel;   }
-			Native_thread_id tid()        const { return _cap_sel;   }
+			int              local_name() const { return _unique_id;         }
+			void*            local()      const { return (void*)_unique_id;  }
+			Native_thread    dst()        const { return _cap_sel;           }
+			Native_thread_id tid()        const { return _cap_sel;           }
 
 			bool valid() const { return _cap_sel.valid() && _unique_id != 0; }
 

base-host/include/base/native_types.h

@@ -27,6 +27,10 @@ namespace Genode {
 
 			long _local_name;
 
+		protected:
+
+			Native_capability(void* ptr) : _local_name((long)ptr) { }
+
 		public:
 
 			Native_capability() : _local_name(0) { }
@@ -35,6 +39,7 @@ namespace Genode {
 
 			bool             valid()      const { return _local_name != 0; }
 			int              local_name() const { return _local_name; }
+			void*            local()      const { return (void*)_local_name; }
 			int              dst()        const { return 0; }
 			Native_thread_id tid()        const { return 0; }
 	};

base-linux/include/base/native_types.h

@@ -108,6 +108,10 @@ namespace Genode {
 			long _tid;         /* target thread */
 			long _local_name;
 
+		protected:
+
+			Native_capability(void* ptr) : _local_name((long)ptr) { }
+
 		public:
 
 			/**
@@ -117,6 +121,8 @@ namespace Genode {
 
 			long local_name() const { return _local_name; }
 
+			void* local() const { return (void*)_local_name; }
+
 			bool valid() const { return _tid != 0; }
 
 

base-mb/include/base/native_types.h

@@ -36,6 +36,10 @@ namespace Genode {
 			Native_thread_id  _tid;
 			long              _local_name;
 
+		protected:
+
+			Native_capability(void* ptr) : _local_name((long)ptr) {}
+
 		public:
 
 			Native_capability() : _tid(0), _local_name(0) { }
@@ -47,6 +51,8 @@ namespace Genode {
 
 			int local_name() const { return _local_name; }
 
+			void* local() const { return (void*)_local_name; }
+
 			int dst() const { return (int)_tid; }
 
 			Native_thread_id tid() const { return _tid; }

base-nova/include/base/native_types.h

@@ -58,6 +58,10 @@ namespace Genode {
 			int _pt_sel;
 			int _unique_id;
 
+		protected:
+
+			Native_capability(void* ptr) : _unique_id((int)ptr) {}
+
 		public:
 
 			/**
@@ -74,12 +78,13 @@ namespace Genode {
 			Native_capability(int pt_sel, int unique_id)
 			: _pt_sel(pt_sel), _unique_id(unique_id) { }
 
-			bool valid()      const { return _pt_sel != 0 && _unique_id != 0; }
-			int  local_name() const { return _unique_id; }
-			int  dst()        const { return _pt_sel; }
+			bool  valid()      const { return _pt_sel != 0 && _unique_id != 0; }
+			int   local_name() const { return _unique_id; }
+			void* local()      const { return (void*)_unique_id; }
+			int   dst()        const { return _pt_sel; }
 
-			int  unique_id()  const { return _unique_id; }
-			int  pt_sel()     const { return _pt_sel; }
+			int   unique_id()  const { return _unique_id; }
+			int   pt_sel()     const { return _pt_sel; }
 	};
 
 	typedef int Native_connection_state;

base-okl4/include/base/native_types.h

@@ -88,6 +88,10 @@ namespace Genode {
 			Okl4::L4_ThreadId_t _tid;
 			long                _local_name;
 
+		protected:
+
+			Native_capability(void* ptr) : _local_name((long)ptr) {}
+
 		public:
 
 			/**
@@ -99,6 +103,8 @@ namespace Genode {
 			long local_name() const { return _local_name; }
 			Okl4::L4_ThreadId_t dst() const { return _tid; }
 
+			void* local() const { return (void*)_local_name; }
+
 			bool valid() const { return !Okl4::L4_IsNilThread(_tid); }
 
 

base-pistachio/include/base/native_types.h

@@ -69,6 +69,10 @@ namespace Genode {
 			Pistachio::L4_ThreadId_t _tid;
 			long                     _local_name;
 
+		protected:
+
+			Native_capability(void* ptr) : _local_name((long)ptr) {}
+
 		public:
 
 			/**
@@ -83,6 +87,8 @@ namespace Genode {
 			long local_name() const { return _local_name; }
 			Pistachio::L4_ThreadId_t dst() const { return _tid; }
 
+			void* local() const { return (void*)_local_name; }
+
 			bool valid() const { return !Pistachio::L4_IsNilThread(_tid); }
 
 

base/include/base/capability.h

@@ -126,6 +126,14 @@ namespace Genode {
 				return cap;
 			}
 
+			/**
+			 * Private constructor, should be used by the local-capability
+			 * factory method only.
+			 *
+			 * \param ptr pointer to the local object this capability represents.
+			 */
+			Capability(void *ptr) : Untyped_capability(ptr) {}
+
 		public:
 
 			typedef RPC_INTERFACE Rpc_interface;
@@ -148,6 +156,28 @@ namespace Genode {
 			 */
 			Capability() { }
 
+			/**
+			 * Factory method to construct a local-capability.
+			 *
+			 * Local-capabilities can be used protection-domain internally
+			 * only. They simply incorporate a pointer to some process-local
+			 * object.
+			 *
+			 * \param ptr pointer to the corresponding local object.
+			 * \return a capability that represents the local object.
+			 */
+			static Capability<RPC_INTERFACE> local_cap(RPC_INTERFACE* ptr) {
+				return Capability<RPC_INTERFACE>((void*)ptr); }
+
+			/**
+			 * Dereference a local-capability.
+			 *
+			 * \param c the local-capability.
+			 * \return pointer to the corresponding local object.
+			 */
+			static RPC_INTERFACE* deref(Capability<RPC_INTERFACE> c) {
+				return reinterpret_cast<RPC_INTERFACE*>(c.local()); }
+
 			/*
 			 * Suppress warning about uninitialized 'ret' variable in 'call'
 			 * functions on compilers that support the #praga. If this is

base/src/core/context_area.cc

@@ -51,7 +51,8 @@ class Context_area_rm_session : public Rm_session
 		                  size_t size, off_t offset,
 		                  bool use_local_addr, Local_addr local_addr)
 		{
-			Dataspace_component *ds = context_ds[ds_cap.local_name()];
+			Dataspace_component *ds =
+				dynamic_cast<Dataspace_component*>(Dataspace_capability::deref(ds_cap));
 			if (!ds) {
 				PERR("dataspace for core context does not exist");
 				return (addr_t)0;
@@ -111,14 +112,8 @@ class Context_area_ram_session : public Ram_session
 			context_ds[i] = new (platform()->core_mem_alloc())
 				Dataspace_component(size, 0, (addr_t)phys_base, false, true);
 
-			/*
-			 * We do not manage the dataspace via an entrypoint because it will
-			 * only be used by the 'context_area_rm_session'. Therefore, we
-			 * construct a "capability" by hand using the context ID as local
-			 * name.
-			 */
-			Native_capability cap;
-			return reinterpret_cap_cast<Ram_dataspace>(Native_capability(cap.dst(), i));
+			Dataspace_capability cap = Dataspace_capability::local_cap(context_ds[i]);
+			return static_cap_cast<Ram_dataspace>(cap);
 		}
 
 		void free(Ram_dataspace_capability ds) { PDBG("not yet implemented"); }