base: buffer session args in 'Connection'

This patch is a preparation of the forthcoming async parent interface.
Note that this patch increases the size of connection objects.
Furthermore it adds a diagnostic message whenever a connection fails.

Issue #2166

repos/base/include/base/connection.h

@@ -33,40 +33,51 @@ class Genode::Connection : public Noncopyable
 	private:
 
 		/*
-		 * Because the argument string is used with the parent interface,
-		 * the message-buffer size of the parent-interface provides a
-		 * realistic upper bound for dimensioning the format- string
-		 * buffer.
+		 * Buffer for storing the session arguments passed to the
+		 * 'session' method that is called before the 'Connection' is
+		 * constructed.
 		 */
 		enum { FORMAT_STRING_SIZE = Parent::Session_args::MAX_SIZE };
 
-		Capability<SESSION_TYPE> _cap;
+		char _session_args[FORMAT_STRING_SIZE];
+		char _affinity_arg[sizeof(Affinity)];
 
 		Parent &_parent;
 
 		On_destruction _on_destruction;
 
-		Capability<SESSION_TYPE> _session(Parent &parent,
-		                                  Affinity const &affinity,
-		                                  const char *format_args, va_list list)
+		void _session(Parent &parent,
+		              Affinity const &affinity,
+		              const char *format_args, va_list list)
 		{
-			char buf[FORMAT_STRING_SIZE];
-
-			String_console sc(buf, FORMAT_STRING_SIZE);
+			String_console sc(_session_args, FORMAT_STRING_SIZE);
 			sc.vprintf(format_args, list);
-
 			va_end(list);
 
-			/* call parent interface with the resulting argument buffer */
-			return parent.session<SESSION_TYPE>(buf, affinity);
+			memcpy(_affinity_arg, &affinity, sizeof(Affinity));
 		}
 
+		Capability<SESSION_TYPE> _request_cap()
+		{
+			Affinity affinity;
+			memcpy(&affinity, _affinity_arg, sizeof(Affinity));
+
+			try {
+				return env()->parent()->session<SESSION_TYPE>(_session_args, affinity); }
+			catch (...) {
+				error(SESSION_TYPE::service_name(), "-session creation failed "
+				      "(", Cstring(_session_args), ")");
+				throw;
+			}
+		}
+
+		Capability<SESSION_TYPE> _cap = _request_cap();
+
 	public:
 
 		/**
 		 * Constructor
 		 *
-		 * \param cap  session capability
 		 * \param od   session policy applied when destructing the connection
 		 *
 		 * The 'op' argument defines whether the session should automatically
@@ -76,8 +87,8 @@ class Genode::Connection : public Noncopyable
 		 * session capability of the connection to another party but never
 		 * invokes any of the session's RPC functions.
 		 */
-		Connection(Env &env, Capability<SESSION_TYPE> cap, On_destruction od = CLOSE)
-		: _cap(cap), _parent(env.parent()), _on_destruction(od) { }
+		Connection(Env &env, Capability<SESSION_TYPE>, On_destruction od = CLOSE)
+		: _parent(env.parent()), _on_destruction(od) { }
 
 		/**
 		 * Constructor
@@ -86,8 +97,8 @@ class Genode::Connection : public Noncopyable
 		 * \deprecated  Use the constructor with 'Env &' as first
 		 *              argument instead
 		 */
-		Connection(Capability<SESSION_TYPE> cap, On_destruction od = CLOSE)
-		: _cap(cap), _parent(*env()->parent()), _on_destruction(od) { }
+		Connection(Capability<SESSION_TYPE>, On_destruction od = CLOSE)
+		: _parent(*env()->parent()), _on_destruction(od) { }
 
 		/**
 		 * Destructor
@@ -116,7 +127,8 @@ class Genode::Connection : public Noncopyable
 			va_list list;
 			va_start(list, format_args);
 
-			return _session(parent, Affinity(), format_args, list);
+			_session(parent, Affinity(), format_args, list);
+			return Capability<SESSION_TYPE>();
 		}
 
 		/**
@@ -129,7 +141,8 @@ class Genode::Connection : public Noncopyable
 			va_list list;
 			va_start(list, format_args);
 
-			return _session(parent, affinity, format_args, list);
+			_session(parent, affinity, format_args, list);
+			return Capability<SESSION_TYPE>();
 		}
 
 		/**
@@ -143,7 +156,8 @@ class Genode::Connection : public Noncopyable
 			va_list list;
 			va_start(list, format_args);
 
-			return _session(*env()->parent(), Affinity(), format_args, list);
+			_session(*env()->parent(), Affinity(), format_args, list);
+			return Capability<SESSION_TYPE>();
 		}
 
 		/**
@@ -158,7 +172,8 @@ class Genode::Connection : public Noncopyable
 			va_list list;
 			va_start(list, format_args);
 
-			return _session(affinity, format_args, list);
+			_session(affinity, format_args, list);
+			return Capability<SESSION_TYPE>();
 		}
 };
 

repos/base/include/rom_session/connection.h

@@ -32,11 +32,7 @@ class Genode::Rom_connection : public Connection<Rom_session>,
 
 		Rom_session_capability _session(Parent &parent, char const *label)
 		{
-			try { return session("ram_quota=4K, label=\"%s\"", label); }
-			catch (...) {
-				error("Could not open ROM session for \"", label, "\"");
-				throw Rom_connection_failed();
-			}
+			return session("ram_quota=4K, label=\"%s\"", label);
 		}
 
 	public:
@@ -49,10 +45,14 @@ class Genode::Rom_connection : public Connection<Rom_session>,
 		 * \throw Rom_connection_failed
 		 */
 		Rom_connection(Env &env, const char *label)
-		:
+		try :
 			Connection<Rom_session>(env, _session(env.parent(), label)),
 			Rom_session_client(cap())
 		{ }
+		catch (...) {
+			error("Could not open ROM session for \"", label, "\"");
+			throw Rom_connection_failed();
+		}
 
 		/**
 		 * Constructor
@@ -62,10 +62,14 @@ class Genode::Rom_connection : public Connection<Rom_session>,
 		 *              argument instead
 		 */
 		Rom_connection(const char *label)
-		:
+		try :
 			Connection<Rom_session>(_session(*env()->parent(), label)),
 			Rom_session_client(cap())
 		{ }
+		catch (...) {
+			error("Could not open ROM session for \"", label, "\"");
+			throw Rom_connection_failed();
+		}
 };
 
 #endif /* _INCLUDE__ROM_SESSION__CONNECTION_H_ */

repos/libports/run/ldso.run

@@ -80,6 +80,7 @@ compare_output_to {
 [init -> test-ldso] Catch exceptions in program
 [init -> test-ldso] ---------------------------
 [init -> test-ldso] exception in remote procedure call:
+[init -> test-ldso] Error: ROM-session creation failed (ram_quota=4K, label="unknown_file")
 [init -> test-ldso] Error: Could not open ROM session for "unknown_file"
 [init -> test-ldso] caught
 [init -> test-ldso] exception in program: caught

repos/os/run/report_rom.run

@@ -68,6 +68,7 @@ compare_output_to {
 	[init -> test-report_rom] Reporter: start reporting (while the ROM client still listens)
 	[init -> test-report_rom] ROM client: wait for update notification
 	[init -> test-report_rom] ROM client: try to open the same report again
+	[init -> test-report_rom] Error: Report-session creation failed (label="brightness", ram_quota=12288, buffer_size=4096)
 	[init -> test-report_rom] ROM client: catched Parent::Service_denied - OK
 	[init -> test-report_rom] --- test-report_rom finished ---
 }