diff --git a/src/lib/debug.c b/src/lib/debug.c
new file mode 100644
index 0000000000000000000000000000000000000000..b4f8c2d0b66ff0fc5542d213dc829101afdc0358
--- /dev/null
+++ b/src/lib/debug.c
@@ -0,0 +1,32 @@
+#include <debug.h>
+#include <stdarg.h>
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <string.h>
+
+/* Prints the call stack, that is, a list of addresses, one in
+   each of the functions we are nested within.  gdb or addr2line
+   may be applied to kernel.o to translate these into file names,
+   line numbers, and function names.  */
+void
+debug_backtrace (void) 
+{
+  static bool explained;
+  void **frame;
+  
+  printf ("Call stack: %p", __builtin_return_address (0));
+  for (frame = __builtin_frame_address (1);
+       (uintptr_t) frame >= 0x1000 && frame[0] != NULL;
+       frame = frame[0]) 
+    printf (" %p", frame[1]);
+  printf (".\n");
+
+  if (!explained) 
+    {
+      explained = true;
+      printf ("The `backtrace' program can make call stacks useful.\n"
+              "Read \"Backtraces\" in the \"Debugging Tools\" chapter\n"
+              "of the Pintos documentation for more information.\n");
+    }
+}