base: new 'Ram_allocator' interface

The 'Ram_allocator' interface contains the subset of the RAM session
interface that is needed to satisfy the needs of the 'Heap' and
'Sliced_heap'. Its small size makes it ideal for intercepting memory
allocations as done by the new 'Constrained_ram_allocator' wrapper
class, which is meant to replace the existing 'base/allocator_guard.h'
and 'os/ram_session_guard.h'.

Issue #2398

repos/base-linux/src/core/include/core_env.h

@@ -48,7 +48,7 @@ namespace Genode {
 	{
 		private:
 
-			Lock _lock;
+			Lock mutable _lock;
 
 		public:
 
@@ -82,6 +82,12 @@ namespace Genode {
 				RAM_SESSION_IMPL::free(ds);
 			}
 
+			size_t dataspace_size(Ram_dataspace_capability ds) const override
+			{
+				Lock::Guard lock_guard(_lock);
+				return RAM_SESSION_IMPL::dataspace_size(ds);
+			}
+
 			int ref_account(Ram_session_capability session)
 			{
 				Lock::Guard lock_guard(_lock);

repos/base-linux/src/core/include/dataspace_component.h

@@ -100,7 +100,7 @@ namespace Genode {
 			/**
 			 * Check if dataspace is owned by a specified object
 			 */
-			bool owner(Dataspace_owner * const o) const { return _owner == o; }
+			bool owner(Dataspace_owner const *o) const { return _owner == o; }
 
 			/**
 			 * Detach dataspace from all rm sessions.

repos/base-linux/src/core/stack_area.cc

@@ -78,23 +78,24 @@ class Stack_area_region_map : public Genode::Region_map
 };
 
 
-class Stack_area_ram_session : public Genode::Ram_session
+struct Stack_area_ram_session : Genode::Ram_session
 {
-	public:
 
-		Genode::Ram_dataspace_capability alloc(Genode::size_t size,
-		                                       Genode::Cache_attribute) {
-			return Genode::Ram_dataspace_capability(); }
+	Genode::Ram_dataspace_capability alloc(Genode::size_t size,
+	                                       Genode::Cache_attribute) override {
+		return Genode::Ram_dataspace_capability(); }
 
-		void free(Genode::Ram_dataspace_capability) { }
+	void free(Genode::Ram_dataspace_capability) override { }
 
-		int ref_account(Genode::Ram_session_capability) { return 0; }
+	Genode::size_t dataspace_size(Genode::Ram_dataspace_capability) const override { return 0; }
 
-		int transfer_quota(Genode::Ram_session_capability, Genode::size_t) { return 0; }
+	int ref_account(Genode::Ram_session_capability) override { return 0; }
 
-		Genode::size_t quota() { return 0; }
+	int transfer_quota(Genode::Ram_session_capability, Genode::size_t) override { return 0; }
 
-		Genode::size_t used() { return 0; }
+	Genode::size_t quota() override { return 0; }
+
+	Genode::size_t used() override { return 0; }
 };
 
 

repos/base-sel4/src/core/stack_area.cc

@@ -120,24 +120,24 @@ class Stack_area_region_map : public Region_map
 };
 
 
-class Stack_area_ram_session : public Ram_session
+struct Stack_area_ram_session : Ram_session
 {
-	public:
+	Ram_dataspace_capability alloc(size_t, Cache_attribute) override {
+		return reinterpret_cap_cast<Ram_dataspace>(Native_capability()); }
 
-		Ram_dataspace_capability alloc(size_t size, Cache_attribute cached) {
-			return reinterpret_cap_cast<Ram_dataspace>(Native_capability()); }
+	void free(Ram_dataspace_capability) override {
+		warning(__func__, " not implemented"); }
 
-		void free(Ram_dataspace_capability ds) {
-			warning(__func__, " not implemented"); }
+	size_t dataspace_size(Ram_dataspace_capability) const override { return 0; }
 
-		int ref_account(Ram_session_capability ram_session) { return 0; }
+	int ref_account(Ram_session_capability ram_session) override { return 0; }
 
-		int transfer_quota(Ram_session_capability ram_session, size_t amount) {
-			return 0; }
+	int transfer_quota(Ram_session_capability ram_session, size_t amount) override {
+		return 0; }
 
-		size_t quota() { return 0; }
+	size_t quota() override { return 0; }
 
-		size_t used() { return 0; }
+	size_t used() override { return 0; }
 };
 
 

repos/base/include/base/heap.h

@@ -16,7 +16,7 @@
 
 #include <util/list.h>
 #include <util/reconstructible.h>
-#include <ram_session/ram_session.h>
+#include <base/ram_allocator.h>
 #include <region_map/region_map.h>
 #include <base/allocator_avl.h>
 #include <base/lock.h>
@@ -32,7 +32,8 @@ namespace Genode {
  * Heap that uses dataspaces as backing store
  *
  * The heap class provides an allocator that uses a list of dataspaces of a RAM
- * session as backing store. One dataspace may be used for holding multiple blocks.
+ * allocator as backing store. One dataspace may be used for holding multiple
+ * blocks.
  */
 class Genode::Heap : public Allocator
 {
@@ -56,18 +57,18 @@ class Genode::Heap : public Allocator
 		 */
 		struct Dataspace_pool : public List<Dataspace>
 		{
-			Ram_session *ram_session; /* RAM session for backing store */
-			Region_map  *region_map;
+			Ram_allocator *ram_alloc; /* backing store */
+			Region_map    *region_map;
 
-			Dataspace_pool(Ram_session *ram, Region_map *rm)
-			: ram_session(ram), region_map(rm) { }
+			Dataspace_pool(Ram_allocator *ram, Region_map *rm)
+			: ram_alloc(ram), region_map(rm) { }
 
 			~Dataspace_pool();
 
 			void remove_and_free(Dataspace &);
 
-			void reassign_resources(Ram_session *ram, Region_map *rm) {
-				ram_session = ram, region_map = rm; }
+			void reassign_resources(Ram_allocator *ram, Region_map *rm) {
+				ram_alloc = ram, region_map = rm; }
 		};
 
 		Lock                           _lock;
@@ -108,13 +109,13 @@ class Genode::Heap : public Allocator
 
 		enum { UNLIMITED = ~0 };
 
-		Heap(Ram_session *ram_session,
-		     Region_map  *region_map,
-		     size_t       quota_limit = UNLIMITED,
-		     void        *static_addr = 0,
-		     size_t       static_size = 0);
+		Heap(Ram_allocator *ram_allocator,
+		     Region_map    *region_map,
+		     size_t         quota_limit = UNLIMITED,
+		     void          *static_addr = 0,
+		     size_t         static_size = 0);
 
-		Heap(Ram_session &ram, Region_map &rm) : Heap(&ram, &rm) { }
+		Heap(Ram_allocator &ram, Region_map &rm) : Heap(&ram, &rm) { }
 
 		~Heap();
 
@@ -127,9 +128,9 @@ class Genode::Heap : public Allocator
 		int quota_limit(size_t new_quota_limit);
 
 		/**
-		 * Re-assign RAM and RM sessions
+		 * Re-assign RAM allocator and region map
 		 */
-		void reassign_resources(Ram_session *ram, Region_map *rm) {
+		void reassign_resources(Ram_allocator *ram, Region_map *rm) {
 			_ds_pool.reassign_resources(ram, rm); }
 
 
@@ -164,7 +165,7 @@ class Genode::Sliced_heap : public Allocator
 			{ }
 		};
 
-		Ram_session    &_ram_session;  /* RAM session for backing store   */
+		Ram_allocator  &_ram_alloc;    /* RAM allocator for backing store */
 		Region_map     &_region_map;   /* region map of the address space */
 		size_t          _consumed;     /* number of allocated bytes       */
 		List<Block>     _blocks;       /* list of allocated blocks        */
@@ -183,13 +184,13 @@ class Genode::Sliced_heap : public Allocator
 		 * \deprecated  Use the other constructor that takes reference
 		 *              arguments
 		 */
-		Sliced_heap(Ram_session *ram_session, Region_map *region_map)
-		: Sliced_heap(*ram_session, *region_map) { }
+		Sliced_heap(Ram_allocator *ram_alloc, Region_map *region_map)
+		: Sliced_heap(*ram_alloc, *region_map) { }
 
 		/**
 		 * Constructor
 		 */
-		Sliced_heap(Ram_session &ram_session, Region_map &region_map);
+		Sliced_heap(Ram_allocator &ram_alloc, Region_map &region_map);
 
 		/**
 		 * Destructor

repos/base/include/base/ram_allocator.h

@@ -0,0 +1,124 @@
+/*
+ * \brief  Interface for allocating RAM dataspaces
+ * \author Norman Feske
+ * \date   2017-05-02
+ */
+
+/*
+ * Copyright (C) 2017 Genode Labs GmbH
+ *
+ * This file is part of the Genode OS framework, which is distributed
+ * under the terms of the GNU Affero General Public License version 3.
+ */
+
+#ifndef _INCLUDE__BASE__RAM_ALLOCATOR_H_
+#define _INCLUDE__BASE__RAM_ALLOCATOR_H_
+
+#include <base/capability.h>
+#include <base/quota_guard.h>
+#include <base/cache.h>
+#include <dataspace/dataspace.h>
+
+namespace Genode {
+
+	struct Ram_dataspace : Dataspace { };
+
+	typedef Capability<Ram_dataspace> Ram_dataspace_capability;
+
+	struct Ram_allocator;
+
+	class Constrained_ram_allocator;
+}
+
+
+struct Genode::Ram_allocator
+{
+	class Alloc_failed    : public Exception    { };
+	class Quota_exceeded  : public Alloc_failed { };
+	class Out_of_metadata : public Alloc_failed { };
+
+
+	/**
+	 * Allocate RAM dataspace
+	 *
+	 * \param  size    size of RAM dataspace
+	 * \param  cached  selects cacheability attributes of the memory,
+	 *                 uncached memory, i.e., for DMA buffers
+	 *
+	 * \throw Quota_exceeded
+	 * \throw Out_of_metadata
+	 *
+	 * \return capability to new RAM dataspace
+	 */
+	virtual Ram_dataspace_capability alloc(size_t size,
+	                                       Cache_attribute cached = CACHED) = 0;
+
+	/**
+	 * Free RAM dataspace
+	 *
+	 * \param ds  dataspace capability as returned by alloc
+	 */
+	virtual void free(Ram_dataspace_capability ds) = 0;
+
+	/**
+	 * Return size of dataspace in bytes
+	 */
+	virtual size_t dataspace_size(Ram_dataspace_capability ds) const = 0;
+};
+
+
+/**
+ * Quota-bounds-checking wrapper of the 'Ram_allocator' interface
+ */
+class Genode::Constrained_ram_allocator : public Ram_allocator
+{
+	private:
+
+		Ram_allocator   &_ram_alloc;
+		Ram_quota_guard &_ram_guard;
+		Cap_quota_guard &_cap_guard;
+
+	public:
+
+		Constrained_ram_allocator(Ram_allocator   &ram_alloc,
+		                          Ram_quota_guard &ram_guard,
+		                          Cap_quota_guard &cap_guard)
+		:
+			_ram_alloc(ram_alloc), _ram_guard(ram_guard), _cap_guard(cap_guard)
+		{ }
+
+		Ram_dataspace_capability alloc(size_t size, Cache_attribute cached) override
+		{
+			size_t page_aligned_size = align_addr(size, 12);
+
+			Ram_quota_guard::Reservation ram (_ram_guard, Ram_quota{page_aligned_size});
+			Cap_quota_guard::Reservation caps(_cap_guard, Cap_quota{1});
+
+			/*
+			 * \throw Out_of_caps, Out_of_ram
+			 */
+			Ram_dataspace_capability ds = _ram_alloc.alloc(page_aligned_size, cached);
+
+			ram. acknowledge();
+			caps.acknowledge();
+
+			return ds;
+		}
+
+		void free(Ram_dataspace_capability ds) override
+		{
+			size_t const size = _ram_alloc.dataspace_size(ds);
+
+			_ram_alloc.free(ds);
+
+			_ram_guard.replenish(Ram_quota{size});
+			_cap_guard.replenish(Cap_quota{1});
+		}
+
+		size_t dataspace_size(Ram_dataspace_capability ds) const override
+		{
+			return _ram_alloc.dataspace_size(ds);
+		}
+};
+
+#endif /* _INCLUDE__BASE__RAM_ALLOCATOR_H_ */

repos/base/include/ram_session/client.h

@@ -16,7 +16,7 @@
 
 #include <ram_session/capability.h>
 #include <ram_session/ram_session.h>
-#include <base/rpc_client.h>
+#include <dataspace/client.h>
 
 namespace Genode { struct Ram_session_client; }
 
@@ -27,11 +27,18 @@ struct Genode::Ram_session_client : Rpc_client<Ram_session>
 	: Rpc_client<Ram_session>(session) { }
 
 	Ram_dataspace_capability alloc(size_t size,
-	                               Cache_attribute cached = CACHED) override {
-		return call<Rpc_alloc>(size, cached); }
+	                               Cache_attribute cached = CACHED) override
+	{
+		return call<Rpc_alloc>(size, cached);
+	}
 
 	void free(Ram_dataspace_capability ds) override { call<Rpc_free>(ds); }
 
+	size_t dataspace_size(Ram_dataspace_capability ds) const override
+	{
+		return ds.valid() ? Dataspace_client(ds).size() : 0;
+	}
+
 	int ref_account(Ram_session_capability ram_session) override {
 		return call<Rpc_ref_account>(ram_session); }
 

repos/base/include/ram_session/ram_session.h

@@ -15,9 +15,7 @@
 #define _INCLUDE__RAM_SESSION__RAM_SESSION_H_
 
 #include <base/stdint.h>
-#include <base/capability.h>
-#include <base/exception.h>
-#include <base/cache.h>
+#include <base/ram_allocator.h>
 #include <dataspace/capability.h>
 #include <ram_session/capability.h>
 #include <session/session.h>
@@ -32,13 +30,10 @@ namespace Genode {
 }
 
 
-struct Genode::Ram_dataspace : Dataspace { };
-
-
 /**
  * RAM session interface
  */
-struct Genode::Ram_session : Session
+struct Genode::Ram_session : Session, Ram_allocator
 {
 	static const char *service_name() { return "RAM"; }
 
@@ -47,40 +42,11 @@ struct Genode::Ram_session : Session
 	typedef Ram_session_client Client;
 
 
-	/*********************
-	 ** Exception types **
-	 *********************/
-
-	class Alloc_failed    : public Exception    { };
-	class Quota_exceeded  : public Alloc_failed { };
-	class Out_of_metadata : public Alloc_failed { };
-
 	/**
 	 * Destructor
 	 */
 	virtual ~Ram_session() { }
 
-	/**
-	 * Allocate RAM dataspace
-	 *
-	 * \param  size    size of RAM dataspace
-	 * \param  cached  selects cacheability attributes of the memory,
-	 *                 uncached memory, i.e., for DMA buffers
-	 *
-	 * \throw  Quota_exceeded
-	 * \throw  Out_of_metadata
-	 * \return capability to new RAM dataspace
-	 */
-	virtual Ram_dataspace_capability alloc(size_t size,
-	                                       Cache_attribute cached = CACHED) = 0;
-
-	/**
-	 * Free RAM dataspace
-	 *
-	 * \param ds  dataspace capability as returned by alloc
-	 */
-	virtual void free(Ram_dataspace_capability ds) = 0;
-
 	/**
 	 * Define reference account for the RAM session
 	 *

repos/base/lib/symbols/ld

@@ -63,8 +63,8 @@ _ZN6Genode10Ipc_serverD1Ev T
 _ZN6Genode10Ipc_serverD2Ev T
 _ZN6Genode11Sliced_heap4freeEPvm T
 _ZN6Genode11Sliced_heap5allocEmPPv T
-_ZN6Genode11Sliced_heapC1ERNS_11Ram_sessionERNS_10Region_mapE T
-_ZN6Genode11Sliced_heapC2ERNS_11Ram_sessionERNS_10Region_mapE T
+_ZN6Genode11Sliced_heapC1ERNS_13Ram_allocatorERNS_10Region_mapE T
+_ZN6Genode11Sliced_heapC2ERNS_13Ram_allocatorERNS_10Region_mapE T
 _ZN6Genode11Sliced_heapD0Ev T
 _ZN6Genode11Sliced_heapD1Ev T
 _ZN6Genode11Sliced_heapD2Ev T
@@ -199,8 +199,8 @@ _ZN6Genode14env_deprecatedEv T
 _ZN6Genode4Heap11quota_limitEm T
 _ZN6Genode4Heap4freeEPvm T
 _ZN6Genode4Heap5allocEmPPv T
-_ZN6Genode4HeapC1EPNS_11Ram_sessionEPNS_10Region_mapEmPvm T
-_ZN6Genode4HeapC2EPNS_11Ram_sessionEPNS_10Region_mapEmPvm T
+_ZN6Genode4HeapC1EPNS_13Ram_allocatorEPNS_10Region_mapEmPvm T
+_ZN6Genode4HeapC2EPNS_13Ram_allocatorEPNS_10Region_mapEmPvm T
 _ZN6Genode4HeapD0Ev T
 _ZN6Genode4HeapD1Ev T
 _ZN6Genode4HeapD2Ev T

repos/base/src/core/include/core_env.h

@@ -51,7 +51,7 @@ namespace Genode {
 	{
 		private:
 
-			Lock _lock;
+			Lock mutable _lock;
 
 		public:
 
@@ -84,6 +84,12 @@ namespace Genode {
 				RAM_SESSION_IMPL::free(ds);
 			}
 
+			size_t dataspace_size(Ram_dataspace_capability ds) const override
+			{
+				Lock::Guard lock_guard(_lock);
+				return RAM_SESSION_IMPL::dataspace_size(ds);
+			}
+
 			int ref_account(Ram_session_capability session)
 			{
 				Lock::Guard lock_guard(_lock);

repos/base/src/core/include/dataspace_component.h

@@ -147,7 +147,7 @@ namespace Genode {
 			/**
 			 * Check if dataspace is owned by a specific owner
 			 */
-			bool owner(Dataspace_owner * const o) const { return _owner == o; }
+			bool owner(Dataspace_owner const *o) const { return _owner == o; }
 
 			List<Rm_region> *regions() { return &_regions; }
 

repos/base/src/core/include/ram_session_component.h

@@ -163,12 +163,22 @@ namespace Genode {
 			 */
 			addr_t phys_addr(Ram_dataspace_capability ds);
 
+
+			/*****************************
+			 ** Ram_allocator interface **
+			 *****************************/
+
+			Ram_dataspace_capability alloc(size_t, Cache_attribute) override;
+
+			void free(Ram_dataspace_capability) override;
+
+			size_t dataspace_size(Ram_dataspace_capability ds) const override;
+
+
 			/***************************
 			 ** RAM Session interface **
 			 ***************************/
 
-			Ram_dataspace_capability alloc(size_t, Cache_attribute);
-			void free(Ram_dataspace_capability);
 			int ref_account(Ram_session_capability);
 			int transfer_quota(Ram_session_capability, size_t);
 			size_t quota() { return _quota_limit; }

repos/base/src/core/ram_session_component.cc

@@ -236,6 +236,20 @@ void Ram_session_component::free(Ram_dataspace_capability ds_cap) {
 	_free_ds(ds_cap); }
 
 
+size_t Ram_session_component::dataspace_size(Ram_dataspace_capability ds_cap) const
+{
+	if (this->cap() == ds_cap)
+		return 0;
+
+	size_t result = 0;
+	_ds_ep->apply(ds_cap, [&] (Dataspace_component *c) {
+		if (c && c->owner(this))
+			result = c->size(); });
+
+	return result;
+}
+
+
 int Ram_session_component::ref_account(Ram_session_capability ram_session_cap)
 {
 	/* the reference account cannot be defined twice */

repos/base/src/core/stack_area.cc

@@ -125,18 +125,19 @@ class Stack_area_region_map : public Region_map
 };
 
 
-class Stack_area_ram_session : public Ram_session
+struct Stack_area_ram_session : Ram_session
 {
-	public:
+	Ram_dataspace_capability alloc(size_t, Cache_attribute) override {
+		return reinterpret_cap_cast<Ram_dataspace>(Native_capability()); }
 
-		Ram_dataspace_capability alloc(size_t, Cache_attribute) override {
-			return reinterpret_cap_cast<Ram_dataspace>(Native_capability()); }
+	void free(Ram_dataspace_capability) override { }
 
-		void   free           (Ram_dataspace_capability)       override { }
-		int    ref_account    (Ram_session_capability)         override { return 0; }
-		int    transfer_quota (Ram_session_capability, size_t) override { return 0; }
-		size_t quota          ()                               override { return 0; }
-		size_t used           ()                               override { return 0; }
+	size_t dataspace_size(Ram_dataspace_capability) const override { return 0; }
+
+	int    ref_account    (Ram_session_capability)         override { return 0; }
+	int    transfer_quota (Ram_session_capability, size_t) override { return 0; }
+	size_t quota          ()                               override { return 0; }
+	size_t used           ()                               override { return 0; }
 };
 
 

repos/base/src/lib/base/heap.cc

@@ -58,7 +58,7 @@ void Heap::Dataspace_pool::remove_and_free(Dataspace &ds)
 	ds.~Dataspace();
 
 	region_map->detach(ds_local_addr);
-	ram_session->free(ds_cap);
+	ram_alloc->free(ds_cap);
 }
 
 
@@ -87,13 +87,13 @@ Heap::Dataspace *Heap::_allocate_dataspace(size_t size, bool enforce_separate_me
 
 	/* make new ram dataspace available at our local address space */
 	try {
-		new_ds_cap = _ds_pool.ram_session->alloc(size);
+		new_ds_cap = _ds_pool.ram_alloc->alloc(size);
 		ds_addr = _ds_pool.region_map->attach(new_ds_cap);
 	} catch (Ram_session::Alloc_failed) {
 		return 0;
 	} catch (Region_map::Attach_failed) {
 		warning("could not attach dataspace");
-		_ds_pool.ram_session->free(new_ds_cap);
+		_ds_pool.ram_alloc->free(new_ds_cap);
 		return 0;
 	}
 
@@ -258,14 +258,14 @@ void Heap::free(void *addr, size_t)
 }
 
 
-Heap::Heap(Ram_session *ram_session,
-           Region_map  *region_map,
-           size_t       quota_limit,
-           void        *static_addr,
-           size_t       static_size)
+Heap::Heap(Ram_allocator *ram_alloc,
+           Region_map    *region_map,
+           size_t         quota_limit,
+           void          *static_addr,
+           size_t         static_size)
 :
 	_alloc(nullptr),
-	_ds_pool(ram_session, region_map),
+	_ds_pool(ram_alloc, region_map),
 	_quota_limit(quota_limit), _quota_used(0),
 	_chunk_size(MIN_CHUNK_SIZE)
 {

repos/base/src/lib/base/sliced_heap.cc

@@ -18,9 +18,9 @@
 using namespace Genode;
 
 
-Sliced_heap::Sliced_heap(Ram_session &ram_session, Region_map &region_map)
+Sliced_heap::Sliced_heap(Ram_allocator &ram_alloc, Region_map &region_map)
 :
-	_ram_session(ram_session), _region_map(region_map), _consumed(0)
+	_ram_alloc(ram_alloc), _region_map(region_map), _consumed(0)
 { }
 
 
@@ -47,13 +47,13 @@ bool Sliced_heap::alloc(size_t size, void **out_addr)
 	Block *block = nullptr;
 
 	try {
-		ds_cap = _ram_session.alloc(size);
+		ds_cap = _ram_alloc.alloc(size);
 		block  = _region_map.attach(ds_cap);
 	} catch (Region_map::Attach_failed) {
 		error("could not attach dataspace to local address space");
-		_ram_session.free(ds_cap);
+		_ram_alloc.free(ds_cap);
 		return false;
-	} catch (Ram_session::Alloc_failed) {
+	} catch (Ram_allocator::Alloc_failed) {
 		error("could not allocate dataspace with size ", size);
 		return false;
 	}
@@ -101,7 +101,7 @@ void Sliced_heap::free(void *addr, size_t size)
 	}
 
 	_region_map.detach(local_addr);
-	_ram_session.free(ds_cap);
+	_ram_alloc.free(ds_cap);
 }
 
 

repos/os/include/os/ram_session_guard.h

@@ -131,6 +131,11 @@ class Genode::Ram_session_guard : public Genode::Ram_session
 			_used -= size;
 		}
 
+		size_t dataspace_size(Ram_dataspace_capability ds) const override
+		{
+			return _session.dataspace_size(ds);
+		}
+
 		int ref_account(Ram_session_capability ram_session) override {
 			return _session.ref_account(ram_session); }
 

repos/os/src/server/loader/ram_session_client_guard.h

@@ -25,16 +25,16 @@ namespace Genode {
 	{
 		private:
 
-			size_t _amount;        /* total amount */
-			size_t _consumed;      /* already consumed bytes */
-			Lock   _consumed_lock;
+			size_t const _amount;        /* total amount */
+			size_t       _consumed;      /* already consumed bytes */
+			Lock mutable _consumed_lock;
 
 		public:
 
 			Ram_session_client_guard(Ram_session_capability session, size_t amount)
 			: Ram_session_client(session), _amount(amount), _consumed(0) { }
 
-			Ram_dataspace_capability alloc(size_t size, Cache_attribute cached)
+			Ram_dataspace_capability alloc(size_t size, Cache_attribute cached) override
 			{
 				Lock::Guard _consumed_lock_guard(_consumed_lock);
 
@@ -52,7 +52,7 @@ namespace Genode {
 				return cap;
 			}
 
-			void free(Ram_dataspace_capability ds)
+			void free(Ram_dataspace_capability ds) override
 			{
 				Lock::Guard _consumed_lock_guard(_consumed_lock);
 
@@ -61,7 +61,12 @@ namespace Genode {
 				Ram_session_client::free(ds);
 			}
 
-			int transfer_quota(Ram_session_capability ram_session, size_t amount)
+			size_t dataspace_size(Ram_dataspace_capability ds) const override
+			{
+				return Ram_session_client::dataspace_size(ds);
+			}
+
+			int transfer_quota(Ram_session_capability ram_session, size_t amount) override
 			{
 				Lock::Guard _consumed_lock_guard(_consumed_lock);
 
@@ -79,12 +84,12 @@ namespace Genode {
 				return result;
 			}
 
-			size_t quota()
+			size_t quota() override
 			{
 				return _amount;
 			}
 
-			size_t used()
+			size_t used() override
 			{
 				Lock::Guard _consumed_lock_guard(_consumed_lock);
 				return _consumed;

repos/ports/src/app/gdb_monitor/ram_session_component.cc

@@ -43,6 +43,12 @@ void Ram_session_component::free(Ram_dataspace_capability ds_cap)
 }
 
 
+size_t Ram_session_component::dataspace_size(Ram_dataspace_capability ds_cap) const
+{
+	return _parent_ram_session.dataspace_size(ds_cap);
+}
+
+
 int Ram_session_component::ref_account(Ram_session_capability ram_session_cap)
 {
 	return _parent_ram_session.ref_account(ram_session_cap);

repos/ports/src/app/gdb_monitor/ram_session_component.h

@@ -56,12 +56,13 @@ class Gdb_monitor::Ram_session_component : public Rpc_object<Ram_session>
 		 ** RAM Session interface **
 		 ***************************/
 
-		Ram_dataspace_capability alloc(size_t, Cache_attribute);
-		void free(Ram_dataspace_capability);
-		int ref_account(Ram_session_capability);
-		int transfer_quota(Ram_session_capability, size_t);
-		size_t quota();
-		size_t used();
+		Ram_dataspace_capability alloc(size_t, Cache_attribute) override;
+		void free(Ram_dataspace_capability) override;
+		size_t dataspace_size(Ram_dataspace_capability) const override;
+		int ref_account(Ram_session_capability) override;
+		int transfer_quota(Ram_session_capability, size_t) override;
+		size_t quota() override;
+		size_t used() override;
 };
 
 #endif /* _RAM_SESSION_COMPONENT_H_ */

repos/ports/src/noux/ram_session_component.h

@@ -106,7 +106,7 @@ class Noux::Ram_session_component : public Rpc_object<Ram_session>
 		 *
 		 * XXX not used yet
 		 */
-		size_t _used_quota;
+		size_t _used_ram_quota = 0;
 
 		Dataspace_registry &_registry;
 
@@ -118,8 +118,7 @@ class Noux::Ram_session_component : public Rpc_object<Ram_session>
 		Ram_session_component(Ram_session &ram, Allocator &alloc,
 		                      Rpc_entrypoint &ep, Dataspace_registry &registry)
 		:
-			_ram(ram), _alloc(alloc), _ep(ep), _used_quota(0),
-			_registry(registry)
+			_ram(ram), _alloc(alloc), _ep(ep), _registry(registry)
 		{
 			_ep.manage(this);
 		}
@@ -140,14 +139,14 @@ class Noux::Ram_session_component : public Rpc_object<Ram_session>
 		 ** Ram_session interface **
 		 ***************************/
 
-		Ram_dataspace_capability alloc(size_t size, Cache_attribute cached)
+		Ram_dataspace_capability alloc(size_t size, Cache_attribute cached) override
 		{
 			Ram_dataspace_capability ds_cap =
 				_ram.alloc(size, cached);
 
 			Ram_dataspace_info *ds_info = new (_alloc) Ram_dataspace_info(ds_cap);
 
-			_used_quota += ds_info->size();
+			_used_ram_quota += ds_info->size();
 
 			_registry.insert(ds_info);
 			_list.insert(ds_info);
@@ -155,7 +154,7 @@ class Noux::Ram_session_component : public Rpc_object<Ram_session>
 			return ds_cap;
 		}
 
-		void free(Ram_dataspace_capability ds_cap)
+		void free(Ram_dataspace_capability ds_cap) override
 		{
 			Ram_dataspace_info *ds_info;
 
@@ -172,7 +171,7 @@ class Noux::Ram_session_component : public Rpc_object<Ram_session>
 				ds_info->dissolve_users();
 
 				_list.remove(ds_info);
-				_used_quota -= ds_info->size();
+				_used_ram_quota -= ds_info->size();
 
 				_ram.free(ds_cap);
 			};
@@ -180,10 +179,19 @@ class Noux::Ram_session_component : public Rpc_object<Ram_session>
 			destroy(_alloc, ds_info);
 		}
 
+		size_t dataspace_size(Ram_dataspace_capability ds_cap) const override
+		{
+			size_t result = 0;
+			_registry.apply(ds_cap, [&] (Ram_dataspace_info *rdi) {
+				if (rdi)
+					result = rdi->size(); });
+			return result;
+		}
+
 		int ref_account(Ram_session_capability) { return 0; }
 		int transfer_quota(Ram_session_capability, size_t) { return 0; }
 		size_t quota() { return _ram.quota(); }
-		size_t used() { return _used_quota; }
+		size_t used() { return _used_ram_quota; }
 };
 
 #endif /* _NOUX__RAM_SESSION_COMPONENT_H_ */