New sandbox library extracted from init component

This patch extracts the child-management functionality from the init
component into a new library called "sandbox". The library API is
located at 'os/include/os/sandbox.h'.

The sandbox API allows for the interaction of the component with the
sandboxed children by providing locally implemented services. This
mechanism is illustrated by the new test at os/src/test/sandbox.

Issue #3601

repos/os/src/test/sandbox/main.cc

@@ -0,0 +1,147 @@
+/*
+ * \brief  Test for the sandbox API
+ * \author Norman Feske
+ * \date   2020-01-09
+ */
+
+/*
+ * Copyright (C) 2020 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.
+ */
+
+#include <base/component.h>
+#include <log_session/log_session.h>
+#include <base/session_object.h>
+#include <os/buffered_xml.h>
+#include <os/sandbox.h>
+
+namespace Test {
+
+	using namespace Genode;
+
+	struct Log_session_component;
+	struct Main;
+}
+
+
+struct Test::Log_session_component : Session_object<Log_session>
+{
+	template <typename... ARGS>
+	Log_session_component(ARGS &&... args) : Session_object(args...) { }
+
+	size_t write(String const &msg) override
+	{
+		/* omit line break and zero termination supplied by 'msg' */
+		if (msg.size() > 1)
+			log("local LOG service: ", Cstring(msg.string(), msg.size() - 2));
+
+		return 0;
+	}
+};
+
+
+struct Test::Main : Sandbox::Local_service_base::Wakeup
+{
+	Env &_env;
+
+	Heap _heap { _env.ram(), _env.rm() };
+
+	Sandbox _sandbox { _env };
+
+	typedef Sandbox::Local_service<Log_session_component> Log_service;
+
+	Log_service _log_service { _sandbox, *this };
+
+	void _generate_sandbox_config(Xml_generator &xml) const
+	{
+		xml.node("parent-provides", [&] () {
+
+			auto service_node = [&] (char const *name) {
+				xml.node("service", [&] () {
+					xml.attribute("name", name); }); };
+
+			service_node("ROM");
+			service_node("CPU");
+			service_node("PD");
+			service_node("LOG");
+		});
+
+		xml.node("start", [&] () {
+			xml.attribute("name", "dummy");
+			xml.attribute("caps", 100);
+			xml.node("resource", [&] () {
+				xml.attribute("name", "RAM");
+				xml.attribute("quantum", "2M");
+			});
+
+			xml.node("config", [&] () {
+				xml.node("log", [&] () {
+					xml.attribute("string", "started"); });
+				xml.node("create_log_connections", [&] () {
+					xml.attribute("ram_upgrade", "100K");
+					xml.attribute("count", "1"); });
+				xml.node("destroy_log_connections", [&] () { });
+				xml.node("log", [&] () {
+					xml.attribute("string", "done"); });
+				xml.node("exit", [&] () { });
+			});
+
+			xml.node("route", [&] () {
+
+				xml.node("service", [&] () {
+					xml.attribute("name", "LOG");
+					xml.node("local", [&] () { }); });
+
+				xml.node("any-service", [&] () {
+					xml.node("parent", [&] () { }); });
+			});
+		});
+	}
+
+	/**
+	 * Sandbox::Local_service_base::Wakeup interface
+	 */
+	void wakeup_local_service() override
+	{
+		_log_service.for_each_requested_session([&] (Log_service::Request &request) {
+
+			Log_session_component &session = *new (_heap)
+				Log_session_component(_env.ep(),
+				                      request.resources,
+				                      request.label,
+				                      request.diag);
+
+			request.deliver_session(session);
+		});
+
+		_log_service.for_each_upgraded_session([&] (Log_session_component &,
+		                                            Session::Resources const &amount) {
+			log("received RAM upgrade of ", amount.ram_quota);
+			return Log_service::Upgrade_response::CONFIRMED;
+		});
+
+		_log_service.for_each_session_to_close([&] (Log_session_component &session) {
+			destroy(_heap, &session);
+			return Log_service::Close_response::CLOSED;
+		});
+	}
+
+	Main(Env &env) : _env(env)
+	{
+		Buffered_xml const config { _heap, "config", [&] (Xml_generator &xml) {
+			_generate_sandbox_config(xml); } };
+
+		config.with_xml_node([&] (Xml_node const &config) {
+
+			log("generated config: ", config);
+
+			_sandbox.apply_config(config);
+		});
+	}
+};
+
+
+void Component::construct(Genode::Env &env) { static Test::Main main(env); }
+

repos/os/src/test/sandbox/target.mk

@@ -0,0 +1,3 @@
+TARGET = test-sandbox
+SRC_CC = main.cc
+LIBS  += base sandbox