base: changes for GDB monitor

- add a new function 'binary_ready_hook_for_gdb()' in ldso. GDB can set a
  breakpoint at this function to know when ldso has loaded the binary
  into memory.
- get the thread state from the NOVA kernel immediately on 'pause()'

Fixes #1968

repos/base/src/lib/ldso/debug.cc

@@ -14,6 +14,12 @@
 #include <debug.h>
 #include <linker.h>
 
+/*
+ * GDB can set a breakpoint at this function to find out when ldso has loaded
+ * the binary into memory.
+ */
+void binary_ready_hook_for_gdb() { }
+
 /**
  * C-break function for GDB
  */

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

@@ -27,6 +27,11 @@ namespace Linker {
 	void dump_link_map(Object *o);
 }
 
+/*
+ * GDB can set a breakpoint at this function to find out when ldso has loaded
+ * the binary into memory.
+ */
+void binary_ready_hook_for_gdb();
 
 /**
  * LIBC debug support

repos/base/src/lib/ldso/main.cc

@@ -580,6 +580,8 @@ void Component::construct(Genode::Env &env)
 
 	Link_map::dump();
 
+	binary_ready_hook_for_gdb();
+
 	/* start binary */
 	binary->call_entry_point(env);
 }