microblaze: ftrace: add static function tracer
If -pg of gcc is enabled with CONFIG_FUNCTION_TRACER=y. a calling to
_mcount will be inserted into each kernel function. so, there is a
possibility to trace the kernel functions in _mcount.
This patch add the specific _mcount support for static function
tracing. by default, ftrace_trace_function is initialized as
ftrace_stub(an empty function), so, the default _mcount will introduce
very little overhead. after enabling ftrace in user-space, it will jump
to a real tracing function and do static function tracing for us.
Commit message from Wu Zhangjin <wuzhangjin@gmail.com>
Signed-off-by: Michal Simek <monstr@monstr.eu>
diff --git a/arch/microblaze/kernel/microblaze_ksyms.c b/arch/microblaze/kernel/microblaze_ksyms.c
index 59ff20e..bc4dcb7 100644
--- a/arch/microblaze/kernel/microblaze_ksyms.c
+++ b/arch/microblaze/kernel/microblaze_ksyms.c
@@ -18,6 +18,7 @@
#include <linux/io.h>
#include <asm/page.h>
#include <asm/system.h>
+#include <linux/ftrace.h>
#include <linux/uaccess.h>
/*
@@ -47,3 +48,7 @@
EXPORT_SYMBOL(__umodsi3);
extern char *_ebss;
EXPORT_SYMBOL_GPL(_ebss);
+#ifdef CONFIG_FUNCTION_TRACER
+extern void _mcount(void);
+EXPORT_SYMBOL(_mcount);
+#endif