GDB monitor: find out page faulting thread

Fixes #898.

base-foc/include/base/thread_state.h

@@ -18,11 +18,11 @@
 
 #include <base/capability.h>
 #include <base/lock.h>
-#include <cpu/cpu_state.h>
+#include <base/thread_state_base.h>
 
 namespace Genode {
 
-	struct Thread_state : public Cpu_state
+	struct Thread_state : Thread_state_base
 	{
 		Native_thread         kcap;         /* thread's gate cap in its pd */
 		int                   id;           /* id of gate capability */

base-foc/src/base/pager/pager.cc

@@ -81,6 +81,8 @@ void Pager_activation_base::entry()
 				/* handle request */
 				if (obj->pager(pager)) {
 					/* could not resolv - leave thread in pagefault */
+					Lock::Guard guard(obj->state.lock);
+					obj->state.unresolved_page_fault = true;
 					PDBG("Could not resolve pf=%p ip=%p",
 					     (void*)pager.fault_addr(), (void*)pager.fault_ip());
 				} else {

base-nova/include/base/thread_state.h

@@ -16,16 +16,16 @@
 #ifndef _INCLUDE__BASE__THREAD_STATE_H_
 #define _INCLUDE__BASE__THREAD_STATE_H_
 
-#include <cpu/cpu_state.h>
+#include <base/thread_state_base.h>
 
 namespace Genode {
 
-	struct Thread_state : public Cpu_state
+	struct Thread_state : Thread_state_base
 	{
 		bool is_vcpu;
 		addr_t sel_exc_base;
 
-		Thread_state() : Cpu_state(), is_vcpu(false), sel_exc_base(~0UL) { }
+		Thread_state() : is_vcpu(false), sel_exc_base(~0UL) { }
 
 		Thread_state(bool is_vcpu, addr_t sel_exc_base)
 		: is_vcpu(is_vcpu), sel_exc_base(sel_exc_base) { }

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

@@ -80,6 +80,8 @@ void Pager_object::_page_fault_handler()
 		}
 
 		if (ret == 1) {
+			obj->_state.thread.unresolved_page_fault = true;
+
 			char client_name[Context::NAME_LEN];
 			myself->name(client_name, sizeof(client_name));
 

base-okl4/include/base/thread_state.h

@@ -20,11 +20,11 @@ namespace Okl4 { extern "C" {
 #include <l4/types.h>
 } }
 
-#include <cpu/cpu_state.h>
+#include <base/thread_state_base.h>
 
 namespace Genode {
 
-	struct Thread_state : public Cpu_state
+	struct Thread_state : Thread_state_base
 	{
 		Okl4::L4_ThreadId_t tid;     /* OKL4 specific thread id */
 	};

base/include/base/thread_state.h

@@ -3,7 +3,8 @@
  * \author Norman Feske
  * \date   2007-07-30
  *
- * This file contains the generic part of the thread state.
+ * This file provides a generic implementation of the 'Thread state' class.
+ * Base platforms can provide their own version of this file.
  */
 
 /*
@@ -16,11 +17,11 @@
 #ifndef _INCLUDE__BASE__THREAD_STATE_H_
 #define _INCLUDE__BASE__THREAD_STATE_H_
 
-#include <cpu/cpu_state.h>
+#include <base/thread_state_base.h>
 
 namespace Genode {
 
-	struct Thread_state : public Cpu_state { };
+	struct Thread_state : Thread_state_base { };
 }
 
 #endif /* _INCLUDE__BASE__THREAD_STATE_H_ */

base/include/base/thread_state_base.h

@@ -0,0 +1,31 @@
+/*
+ * \brief  Thread state base class
+ * \author Norman Feske
+ * \date   2007-07-30
+ *
+ * This file contains the generic part of the thread state.
+ */
+
+/*
+ * Copyright (C) 2007-2013 Genode Labs GmbH
+ *
+ * This file is part of the Genode OS framework, which is distributed
+ * under the terms of the GNU General Public License version 2.
+ */
+
+#ifndef _INCLUDE__BASE__THREAD_STATE_BASE_H_
+#define _INCLUDE__BASE__THREAD_STATE_BASE_H_
+
+#include <cpu/cpu_state.h>
+
+namespace Genode {
+
+	struct Thread_state_base : Cpu_state
+	{
+		bool unresolved_page_fault;
+
+		Thread_state_base() : unresolved_page_fault(false) { };
+	};
+}
+
+#endif /* _INCLUDE__BASE__THREAD_STATE_BASE_H_ */

ports/src/app/gdb_monitor/gdbserver/genode-low.cc

@@ -181,6 +181,23 @@ void genode_continue_thread(unsigned long lwpid, int single_step)
 }
 
 
+unsigned long genode_find_segfault_lwpid()
+{
+	Cpu_session_component *csc = gdb_stub_thread()->cpu_session_component();
+
+	Thread_capability thread_cap = csc->first();
+
+	while (thread_cap.valid()) {
+		Thread_state thread_state = csc->state(thread_cap);
+		if (thread_state.unresolved_page_fault)
+			return csc->lwpid(thread_cap);
+		thread_cap = csc->next(thread_cap);
+	}
+
+	PDBG("could not determine thread which caused the page fault");
+	return 1;
+}
+
 
 class Memory_model
 {

ports/src/app/gdb_monitor/gdbserver/genode-low.h

@@ -31,6 +31,8 @@ void genode_resume_all_threads();
 ptid_t genode_wait_for_signal_or_gdb_interrupt(struct target_waitstatus *status);
 void genode_continue_thread(unsigned long lwpid, int single_step);
 
+unsigned long genode_find_segfault_lwpid();
+
 int genode_fetch_register(int regno, unsigned long *reg_content);
 void genode_store_register(int regno, unsigned long reg_content);
 unsigned char genode_read_memory_byte(void *addr);

ports/src/app/gdb_monitor/gdbserver_genode.patch

@@ -651,7 +651,7 @@ index 69c6b57..cffa803 100644
    x86_supports_tracepoints,
    x86_get_thread_area,
 diff --git a/gdb/gdbserver/remote-utils.c b/gdb/gdbserver/remote-utils.c
-index 650ddf8..046dd2e 100644
+index 650ddf8..728da30 100644
 --- a/gdb/gdbserver/remote-utils.c
 +++ b/gdb/gdbserver/remote-utils.c
 @@ -18,11 +18,14 @@
@@ -756,11 +756,11 @@ index 650ddf8..046dd2e 100644
 +		  genode_stop_all_threads();
 +
 +		  if (sig > 0) {
-+			  event_ptid.lwp = sig;
++			  event_ptid.lwp    = sig;
 +			  status->kind      = TARGET_WAITKIND_STOPPED;
 +			  status->value.sig = TARGET_SIGNAL_TRAP;
 +		  } else {
-+			  event_ptid.lwp    = 1;
++			  event_ptid.lwp    = genode_find_segfault_lwpid();
 +			  status->kind      = TARGET_WAITKIND_STOPPED;
 +			  status->value.sig = TARGET_SIGNAL_SEGV;
 +		  }