Remove blocking calls from root and parent RPCs

This is a redesign of the root and parent interfaces to eliminate
blocking RPC calls.

- New session representation at the parent (base/session_state.h)
- base-internal root proxy mechanism as migration path
- Redesign of base/service.h
- Removes ancient 'Connection::KEEP_OPEN' feature
- Interface change of 'Child', 'Child_policy', 'Slave', 'Slave_policy'
- New 'Slave::Connection'
- Changed child-construction procedure to be compatible with the
  non-blocking parent interface and to be easier to use
- The child's initial LOG session, its binary ROM session, and the
  linker ROM session have become part of the child's envirenment.
- Session upgrading must now be performed via 'env.upgrade' instead
  of performing a sole RPC call the parent. To make RAM upgrades
  easier, the 'Connection' provides a new 'upgrade_ram' method.

Issue #2120

repos/base/src/lib/ldso/include/file.h

@@ -75,14 +75,32 @@ struct Linker::File
  */
 struct Linker::Elf_file : File
 {
-	Env                     &env;
-	Rom_connection           rom;
-	Ram_dataspace_capability ram_cap[Phdr::MAX_PHDR];
-	bool               const loaded;
+	Env                                 &env;
+	Lazy_volatile_object<Rom_connection> rom_connection;
+	Rom_session_client                   rom;
+	Ram_dataspace_capability             ram_cap[Phdr::MAX_PHDR];
+	bool                           const loaded;
+
+	typedef String<64> Name;
+
+	Rom_session_capability _rom_cap(Name const &name)
+	{
+		/* request the linker and binary from the component environment */
+		Session_capability cap;
+		if (name == binary_name())
+			cap = env.parent().session_cap(Parent::Env::binary());
+		if (name == linker_name())
+			cap = env.parent().session_cap(Parent::Env::linker());
+		if (cap.valid())
+			return reinterpret_cap_cast<Rom_session>(cap);
+
+		rom_connection.construct(env, name.string());
+		return *rom_connection;
+	}
 
 	Elf_file(Env &env, Allocator &md_alloc, char const *name, bool load)
 	:
-		env(env), rom(env, name), loaded(load)
+		env(env), rom(_rom_cap(name)), loaded(load)
 	{
 		load_phdr();
 

repos/base/src/lib/ldso/include/linker.h

@@ -103,12 +103,6 @@ namespace Linker {
 	 * Global ELF access lock
 	 */
 	Lock &lock();
-
-	/**
-	 * Invariants
-	 */
-	constexpr char const *binary_name() { return "binary"; }
-	constexpr char const *linker_name() { return "ld.lib.so"; }
 }
 
 

repos/base/src/lib/ldso/include/region_map.h

@@ -96,7 +96,7 @@ class Linker::Region_map
 				[&] () {
 					return _rm.attach_at(ds, local_addr - _base, size, offset);
 				},
-				[&] () { _env.parent().upgrade(_env.pd_session_cap(), "ram_quota=8K"); });
+				[&] () { _env.upgrade(Parent::Env::pd(), "ram_quota=8K"); });
 		}
 
 		/**
@@ -109,7 +109,7 @@ class Linker::Region_map
 				[&] () {
 					return _rm.attach_executable(ds, local_addr - _base, size, offset);
 				},
-				[&] () { _env.parent().upgrade(_env.pd_session_cap(), "ram_quota=8K"); });
+				[&] () { _env.upgrade(Parent::Env::pd(), "ram_quota=8K"); });
 		}
 
 		void detach(Local_addr local_addr) { _rm.detach((addr_t)local_addr - _base); }

repos/base/src/lib/ldso/include/types.h

@@ -38,6 +38,12 @@ namespace Linker {
 
 	enum Bind { BIND_LAZY = Shared_object::BIND_LAZY,
 	            BIND_NOW  = Shared_object::BIND_NOW };
+
+	/**
+	 * Invariants
+	 */
+	constexpr char const *binary_name() { return "binary"; }
+	constexpr char const *linker_name() { return "ld.lib.so"; }
 }
 
 #endif /* _INCLUDE__TYPES_H_ */