NOVA: add single-step support used by gdb

Fixes #336

base-nova/include/base/pager.h

@@ -62,6 +62,7 @@ namespace Genode {
 				addr_t sel_client_ec;
 				bool valid;
 				bool dead;
+				bool singlestep;
 			} _state;
 
 			void _copy_state(Nova::Utcb * utcb);
@@ -173,6 +174,8 @@ namespace Genode {
 
 			uint8_t client_recall();
 			void    client_set_ec(addr_t ec) { _state.sel_client_ec = ec; }
+
+			void single_step(bool on) { _state.singlestep = on; }
 	};
 
 

base-nova/src/base/pager/pager.cc

@@ -124,8 +124,18 @@ void Pager_object::_recall_handler()
 
 	obj->_state.valid = false;
 
+	bool singlestep_state = obj->_state.thread.eflags & 0x100UL;
+	if (obj->_state.singlestep && !singlestep_state) {
+		utcb->flags = obj->_state.thread.eflags | 0x100UL;
+		utcb->mtd = Nova::Mtd(Mtd::EFL).value();
+	} else
+	if (!obj->_state.singlestep && singlestep_state) {
+		utcb->flags = obj->_state.thread.eflags & ~0x100UL;
+		utcb->mtd = Nova::Mtd(Mtd::EFL).value();
+	} else
+		utcb->mtd = 0;
 	utcb->set_msg_word(0);
-	utcb->mtd = 0;
+	
 	reply(myself->stack_top());
 }
 
@@ -201,6 +211,7 @@ Pager_object::Pager_object(unsigned long badge)
 	_sm_state_notify     = cap_selector_allocator()->alloc();
 	_state.valid         = false;
 	_state.dead          = false;
+	_state.singlestep    = false;
 	_state.sel_client_ec = Native_thread::INVALID_INDEX;
 
 	/* Create portal for exception handlers 0x0 - 0xd */

base-nova/src/core/cpu_session_extension.cc

@@ -23,7 +23,7 @@ Native_capability
 Cpu_session_component::native_cap(Thread_capability thread_cap)
 {
 	Cpu_thread_component *thread = _lookup_thread(thread_cap);
-	if (!thread)
+	if (!thread || !thread->platform_thread())
 		return Native_capability::invalid_cap();
 
 	return thread->platform_thread()->native_cap();
@@ -38,3 +38,15 @@ Cpu_session_component::pause_sync(Thread_capability target_thread_cap)
 
 	return thread->platform_thread()->pause();
 }
+
+void
+Cpu_session_component::single_step(Thread_capability thread_cap, bool enable)
+{
+	using namespace Genode;
+
+	Cpu_thread_component *thread = _lookup_thread(thread_cap);
+	if (!thread || !thread->platform_thread())
+		return;
+
+	thread->platform_thread()->single_step(enable);
+}

base-nova/src/core/include/cpu_session_component.h

@@ -137,6 +137,7 @@ namespace Genode {
 			int start(Thread_capability, addr_t, addr_t);
 			void pause(Thread_capability thread_cap);
 			void resume(Thread_capability thread_cap);
+			void single_step(Thread_capability thread_cap, bool enable);
 			void cancel_blocking(Thread_capability);
 			int name(Thread_capability, char *, size_t);
 			int state(Thread_capability, Thread_state *);

base-nova/src/core/include/platform_thread.h

@@ -152,6 +152,8 @@ namespace Genode {
 					_sel_ec(), Obj_crd::RIGHT_EC_RECALL);
 			}
 
+			void single_step(bool on);
+
 	};
 }
 

base-nova/src/core/platform_thread.cc

@@ -294,6 +294,12 @@ void Platform_thread::cancel_blocking()
 	_pager->client_cancel_blocking();
 }
 
+void Platform_thread::single_step(bool on)
+{
+	if (!_pager) return;
+
+	_pager->single_step(on);
+}
 
 unsigned long Platform_thread::pager_object_badge() const
 {