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>

1 files changed, 4 insertions, 0 deletions

diff --git a/arch/microblaze/kernel/cpu/Makefile b/arch/microblaze/kernel/cpu/Makefile
index 20646e549271..59cc7bceaf8c 100644
--- a/arch/microblaze/kernel/cpu/Makefile
+++ b/arch/microblaze/kernel/cpu/Makefile
@@ -2,6 +2,10 @@
 # Build the appropriate CPU version support
 #
 
+ifdef CONFIG_FUNCTION_TRACER
+CFLAGS_REMOVE_cache.o = -pg
+endif
+
 EXTRA_CFLAGS += -DCPU_MAJOR=$(CPU_MAJOR) -DCPU_MINOR=$(CPU_MINOR) \
                 -DCPU_REV=$(CPU_REV)