Linux: cleanup system-call bindings

This patch simplifies the system call bindings. The common syscall
bindings in 'src/platform/' have been reduced to the syscalls needed by
non-core programs. The additional syscalls that are needed solely by
core have been moved to 'src/core/include/core_linux_syscalls.h'.
Furthermore, the resource path is not used outside of core anymore.
Hence, we could get rid of the rpath library. The resource-path code has
been moved to 'src/core/include/resource_path.h'. The IPC-related parts
of 'src/platform' have been moved to the IPC library. So there is now a
clean separation between low-level syscall bindings (in 'src/platform')
and higher-level code.

The code for the socket-descriptor registry is now located in the
'src/base/ipc/socket_descriptor_registry.h' header. The interface is
separated from 'ipc.cc' because core needs to access the registry from
outside the ipc library.

base-linux/src/base/ipc/socket_descriptor_registry.h

@@ -0,0 +1,132 @@
+/*
+ * \brief  Linux-specific socket-descriptor registry
+ * \author Norman Feske
+ * \date   2012-07-26
+ *
+ * We use the names of Unix-domain sockets as keys to uniquely identify
+ * entrypoints. When receiving a socket descriptor as IPC payload, we first
+ * lookup the corresponding entrypoint ID. If we already possess a socket
+ * descriptor pointing to the same entrypoint, we close the received one and
+ * use the already known descriptor instead.
+ */
+
+/*
+ * Copyright (C) 2012 Genode Labs GmbH
+ *
+ * This file is part of the Genode OS framework, which is distributed
+ * under the terms of the GNU General Public License version 2.
+ */
+
+#ifndef _BASE__IPC__SOCKET_DESCRIPTOR_REGISTRY_H_
+#define _BASE__IPC__SOCKET_DESCRIPTOR_REGISTRY_H_
+
+#include <base/lock.h>
+
+
+namespace Genode
+{
+	template <unsigned MAX_FDS>
+	class Socket_descriptor_registry;
+
+	typedef Socket_descriptor_registry<100> Ep_socket_descriptor_registry;
+
+	/**
+	 * Return singleton instance of registry for tracking entrypoint sockets
+	 */
+	Ep_socket_descriptor_registry *ep_sd_registry();
+}
+
+
+template <unsigned MAX_FDS>
+class Genode::Socket_descriptor_registry
+{
+	public:
+
+		class Limit_reached { };
+		class Aliased_global_id { };
+
+	private:
+
+		struct Entry
+		{
+			int fd;
+			int global_id;
+
+			/**
+			 * Default constructor creates empty entry
+			 */
+			Entry() : fd(-1), global_id(-1) { }
+
+			Entry(int fd, int global_id) : fd(fd), global_id(global_id) { }
+
+			bool is_free() const { return fd == -1; }
+		};
+
+		Entry _entries[MAX_FDS];
+
+		Genode::Lock mutable _lock;
+
+		Entry &_find_free_entry()
+		{
+			for (unsigned i = 0; i < MAX_FDS; i++)
+				if (_entries[i].is_free())
+					return _entries[i];
+
+			throw Limit_reached();
+		}
+
+		bool _is_registered(int global_id) const
+		{
+			for (unsigned i = 0; i < MAX_FDS; i++)
+				if (_entries[i].global_id == global_id)
+					return true;
+
+			return false;
+		}
+
+	public:
+
+		/**
+		 * Register association of socket descriptor and its corresponding ID
+		 *
+		 * \throw Limit_reached
+		 * \throw Aliased_global_id  if global ID is already registered
+		 */
+		void associate(int sd, int global_id)
+		{
+			Genode::Lock::Guard guard(_lock);
+
+			/* ignore invalid capabilities */
+			if (sd == -1 || global_id == -1)
+				return;
+
+			/*
+			 * Check for potential aliasing
+			 *
+			 * We allow any global ID to be present in the registry only once.
+			 */
+			if (_is_registered(global_id))
+				throw Aliased_global_id();
+
+			Entry &entry = _find_free_entry();
+			entry = Entry(sd, global_id);
+		}
+
+		/**
+		 * Lookup file descriptor that belongs to specified global ID
+		 *
+		 * \return file descriptor or -1 if lookup failed
+		 */
+		int lookup_fd_by_global_id(int global_id) const
+		{
+			Genode::Lock::Guard guard(_lock);
+
+			for (unsigned i = 0; i < MAX_FDS; i++)
+				if (_entries[i].global_id == global_id)
+					return _entries[i].fd;
+
+			return -1;
+		}
+};
+
+#endif /* _BASE__IPC__SOCKET_DESCRIPTOR_REGISTRY_H_ */