stacktrace: fix modular build, export print_stack_trace and save_stack_trace

fix:

ERROR: "print_stack_trace" [kernel/backtracetest.ko] undefined!
ERROR: "save_stack_trace" [kernel/backtracetest.ko] undefined!

Signed-off-by: Ingo Molnar <mingo@elte.hu>

and fix:

  Building modules, stage 2.
  MODPOST 376 modules
ERROR: "print_stack_trace" [kernel/backtracetest.ko] undefined!
make[1]: *** [__modpost] Error 1

Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 2 insertions, 0 deletions

diff --git a/kernel/stacktrace.c b/kernel/stacktrace.c
index 7eaea9d02a52..94b527ef1d1e 100644
--- a/kernel/stacktrace.c
+++ b/kernel/stacktrace.c
@@ -6,6 +6,7 @@
  *  Copyright (C) 2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
  */
 #include <linux/sched.h>
+#include <linux/module.h>
 #include <linux/kallsyms.h>
 #include <linux/stacktrace.h>
 
@@ -21,4 +22,5 @@ void print_stack_trace(struct stack_trace *trace, int spaces)
                 print_ip_sym(trace->entries[i]);
         }
 }
+EXPORT_SYMBOL_GPL(print_stack_trace);