diff -ruN porting05/Makefile porting06/Makefile
--- porting05/Makefile	Sun Apr 12 12:09:59 2009
+++ porting06/Makefile	Sun Apr 19 21:53:32 2009
@@ -6,6 +6,7 @@
 OBJS += extintr.o
 OBJS += kozos.o command.o
 OBJS += stublib.o ppc-stub.o
+OBJS += mcount.o logging.o
 
 LIB = libc.a
 TARGET ?= sample
@@ -26,6 +27,9 @@
 
 $(TARGET) :	$(OBJS) $(LIB)
 		$(CC) $(OBJS) -o $(TARGET) $(CFLAGS) $(LFLAGS)
+
+extintr.o :	extintr.c
+		$(CC) -c $< $(CFLAGS) -pg
 
 .c.o :		$<
 #		$(CC) -S $< $(CFLAGS)
diff -ruN porting05/command.c porting06/command.c
--- porting05/command.c	Sun Apr 12 12:09:59 2009
+++ porting06/command.c	Sun Apr 19 21:53:32 2009
@@ -1,6 +1,7 @@
 #include "kozos.h"
 #include "thread.h"
 #include "extintr.h"
+#include "logging.h"
 
 #include "lib.h"
 
@@ -67,7 +68,7 @@
 {
   char *p;
   char buffer[128];
-  int len, size;
+  int len, size, i, log;
 
   len = 0;
   send_write(index, "> ");
@@ -105,13 +106,21 @@
       kz_break();
     } else if (!strncmp(buffer, "threads", 7)) {
       kz_thread *thp;
-      int i;
       for (i = 0; i < THREAD_NUM; i++) {
 	thp = &threads[i];
 	if (!thp->id) continue;
 	send_write(index, thp->name);
 	send_write(index, "\n");
       }
+    } else if (!strncmp(buffer, "log", 3)) {
+      logging_disable = 1;
+      log = logging_cur;
+      for (i = 0; i < LOGGING_BUF_SIZE; i++) {
+	ub_printf("%08x%c", logging_buf[log++], ((i % 8) == 7) ? '\n' : ' ');
+	if (log >= LOGGING_BUF_SIZE)
+	  log = 0;
+      }
+      logging_disable = 0;
     } else if (!strncmp(buffer, "exit", 4)) {
       break;
     }
diff -ruN porting05/logging.c porting06/logging.c
--- porting05/logging.c	Thu Jan  1 09:00:00 1970
+++ porting06/logging.c	Sun Apr 19 21:53:32 2009
@@ -0,0 +1,15 @@
+#include "kozos.h"
+#include "logging.h"
+
+int logging_disable = 0;
+int logging_cur = 0;
+int logging_buf[LOGGING_BUF_SIZE];
+
+void logging(int addr)
+{
+  if (!logging_disable) {
+    logging_buf[logging_cur++] = addr;
+    if (logging_cur >= LOGGING_BUF_SIZE)
+      logging_cur = 0;
+  }
+}
diff -ruN porting05/logging.h porting06/logging.h
--- porting05/logging.h	Thu Jan  1 09:00:00 1970
+++ porting06/logging.h	Sun Apr 19 21:53:32 2009
@@ -0,0 +1,9 @@
+#ifndef _KOZOS_LOGGING_H_INCLUDED_
+#define _KOZOS_LOGGING_H_INCLUDED_
+
+#define LOGGING_BUF_SIZE 64
+extern int logging_disable;
+extern int logging_cur;
+extern int logging_buf[];
+
+#endif
diff -ruN porting05/mcount.s porting06/mcount.s
--- porting05/mcount.s	Thu Jan  1 09:00:00 1970
+++ porting06/mcount.s	Sun Apr 19 21:53:32 2009
@@ -0,0 +1,31 @@
+	.text
+	.globl	_mcount
+	.type	_mcount,@function
+_mcount:
+	stwu	1,-48(1)
+	stw	 3,16(1)
+	stw	 4,20(1)
+	stw	 5,24(1)
+	stw	 6,28(1)
+	stw	 7,32(1)
+	stw	 8,36(1)
+	stw	 9,40(1)
+	stw	10,44(1)
+	mflr	3
+	stw	3,8(1)
+	bl	logging
+
+	lwz	9,8(1)
+	mtctr	9
+	lwz	10,52(1)
+	mtlr	10
+	lwz	 3,16(1)
+	lwz	 4,20(1)
+	lwz	 5,24(1)
+	lwz	 6,28(1)
+	lwz	 7,32(1)
+	lwz	 8,36(1)
+	lwz	 9,40(1)
+	lwz	10,44(1)
+	addi	1,1,48
+	bctr