diff --git a/kernel/include/process.h b/kernel/include/process.h
index bfc9fb17..ce5cca09 100644
--- a/kernel/include/process.h
+++ b/kernel/include/process.h
@@ -62,8 +62,45 @@
 #define PT_TRACED 0x1     /* The process is ptraced */
 #define PT_TRACE_EXEC 0x2 /* Trace execve(2) */
 
+#define	PTRACE_TRACEME 0
+#define	PTRACE_PEEKTEXT 1
+#define	PTRACE_PEEKDATA 2
+#define	PTRACE_PEEKUSER 3
+#define	PTRACE_POKETEXT 4
+#define	PTRACE_POKEDATA 5
+#define	PTRACE_POKEUSER 6
 #define PTRACE_CONT 7
 #define PTRACE_KILL 8
+#define	PTRACE_SINGLESTEP 9
+#define	PTRACE_GETREGS 12
+#define	PTRACE_SETREGS 13
+#define	PTRACE_GETFPREGS 14
+#define	PTRACE_SETFPREGS 15
+#define	PTRACE_ATTACH 16
+#define	PTRACE_DETACH 17
+#define	PTRACE_GETFPXREGS 18
+#define	PTRACE_SETFPXREGS 19
+#define	PTRACE_SYSCALL 24
+#define	PTRACE_SETOPTIONS 0x4200
+#define	PTRACE_GETEVENTMSG 0x4201
+#define	PTRACE_GETSIGINFO 0x4202
+#define	PTRACE_SETSIGINFO 0x4203
+
+#define PTRACE_O_TRACESYSGOOD 1
+#define PTRACE_O_TRACEFORK 2
+#define PTRACE_O_TRACEVFORK 4
+#define PTRACE_O_TRACECLONE 8
+#define PTRACE_O_TRACEEXEC 0x10
+#define PTRACE_O_TRACEVFORKDONE 0x20
+#define PTRACE_O_TRACEEXIT 0x40
+#define PTRACE_O_MASK 0x7f
+
+#define	PTRACE_EVENT_FORK 1
+#define	PTRACE_EVENT_VFORK 2
+#define	PTRACE_EVENT_CLONE 3
+#define	PTRACE_EVENT_EXEC 4
+#define	PTRACE_EVENT_VFORK_DONE 5
+#define	PTRACE_EVENT_EXIT 6
 
 #define SIGNAL_STOP_STOPPED   0x1 /* The process has been stopped by SIGSTOP */
 #define SIGNAL_STOP_CONTINUED 0x2 /* The process has been resumed by SIGCONT */
diff --git a/kernel/process.c b/kernel/process.c
index b41b1d43..60bed7d2 100644
--- a/kernel/process.c
+++ b/kernel/process.c
@@ -84,12 +84,11 @@ void init_fork_tree_node(struct fork_tree_node *ftn,
 	/* These will be filled out when changing status */
 	ftn->pid = -1;
 	ftn->exit_status = -1;
-    ftn->group_exit_status = 0;
 	ftn->status = PS_RUNNING;
-#if 1
-	ftn->ptrace = parent ? PT_TRACED : 0; /*debug*//*takagi*/
-#endif
-    ftn->signal_flags = 0;
+
+	ftn->group_exit_status = 0;
+	ftn->ptrace = 0;
+	ftn->signal_flags = 0;
 
 	ftn->parent = NULL;
 	if (parent) {
@@ -98,9 +97,6 @@ void init_fork_tree_node(struct fork_tree_node *ftn,
 	INIT_LIST_HEAD(&ftn->children);
 	INIT_LIST_HEAD(&ftn->siblings_list);
 
-	if (parent) {
-        ftn->ppid_parent = parent; /*debug*//*takagi*/
-    }
 	INIT_LIST_HEAD(&ftn->ptrace_children);
 	INIT_LIST_HEAD(&ftn->ptrace_siblings_list);
 	
@@ -297,12 +293,6 @@ struct process *clone_process(struct process *org, unsigned long pc,
 		list_add_tail(&proc->ftn->siblings_list, &org->ftn->children);
 		ihk_mc_spinlock_unlock_noirq(&org->ftn->lock);	
 
-        /*takagi*//*debug*/
-#if 1
-		ihk_mc_spinlock_lock_noirq(&org->ftn->lock);
-		list_add_tail(&proc->ftn->ptrace_siblings_list, &org->ftn->ptrace_children);
-		ihk_mc_spinlock_unlock_noirq(&org->ftn->lock);	
-#endif
 		/* We hold a reference to parent */
 		hold_fork_tree_node(proc->ftn->parent);
 		
@@ -327,6 +317,25 @@ err_free_proc:
 	return NULL;
 }
 
+int ptrace_traceme(void){
+        struct process *proc = cpu_local_var(current);
+        struct fork_tree_node *ftn = proc->ftn, *parent;
+
+	ftn->ptrace = PT_TRACED;
+
+	parent = ftn->parent;
+	if (parent != NULL) {
+		ftn->ppid_parent = parent;
+
+		ihk_mc_spinlock_lock_noirq(&parent->lock);
+		list_add_tail(&ftn->ptrace_siblings_list, &parent->ptrace_children);
+		ihk_mc_spinlock_unlock_noirq(&parent->lock);
+	}
+
+	return 0;
+}
+
+
 static int copy_user_ranges(struct process *proc, struct process *org) 
 {
 	struct vm_range *src_range;
diff --git a/kernel/syscall.c b/kernel/syscall.c
index df6d1f38..d7b1ee9e 100644
--- a/kernel/syscall.c
+++ b/kernel/syscall.c
@@ -459,7 +459,7 @@ rescan:
             }
 
             if(child_iter->status & (PS_STOPPED | PS_TRACED)) {
-                /* ptraced and in stopeed or trace-stopped state */
+                /* ptraced and in stopped or trace-stopped state */
                 ret = wait_stopped(proc, child_iter, status, options);
                 if(ret) {
                     goto out_found;
@@ -2277,6 +2277,8 @@ SYSCALL_DECLARE(getrlimit)
 	return ret;
 }
 
+extern int ptrace_traceme(void);
+
 static int ptrace_wakeup_sig(int pid, long request, long data) {
 	dkprintf("ptrace_wakeup_sig,pid=%d,data=%08x\n", pid, data);
 	int error;
@@ -2353,6 +2355,8 @@ SYSCALL_DECLARE(ptrace)
     int error;
 
     switch(request) {
+    case PTRACE_TRACEME:
+	error = ptrace_traceme();
     case PTRACE_KILL:
     case PTRACE_CONT:
         error = ptrace_wakeup_sig(pid, request, data);