[PATCH 1/3] ftrace: introdue ftrace_call_init

[Jisheng Zhang]

On some arch, the FTRACE_WITH_REGS is implemented with gcc's
 -fpatchable-function-entry (=2), gcc adds 2 NOPs at the beginning
of each function, so this makes the MCOUNT_ADDR useless. In ftrace
common framework, MCOUNT_ADDR is mostly used to "init" the nop, so
let's introcude ftrace_call_init().

Signed-off-by: Jisheng Zhang <Jisheng.Zhang@xxxxxxxxxxxxx>
---
 include/linux/ftrace.h | 1 +
 kernel/trace/ftrace.c  | 4 ++++
 2 files changed, 5 insertions(+)

diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 8a8cb3c401b2..8175ffb671f0 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -458,6 +458,7 @@ extern void ftrace_regs_caller(void);
 extern void ftrace_call(void);
 extern void ftrace_regs_call(void);
 extern void mcount_call(void);
+extern int ftrace_call_init(struct module *mod, struct dyn_ftrace *rec);
 
 void ftrace_modify_all_code(int command);
 
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index eca34503f178..9df5a66a6811 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -2500,7 +2500,11 @@ ftrace_code_disable(struct module *mod, struct dyn_ftrace *rec)
 	if (unlikely(ftrace_disabled))
 		return 0;
 
+#ifdef MCOUNT_ADDR
 	ret = ftrace_make_nop(mod, rec, MCOUNT_ADDR);
+#else
+	ret = ftrace_call_init(mod, rec);
+#endif
 	if (ret) {
 		ftrace_bug_type = FTRACE_BUG_INIT;
 		ftrace_bug(ret, rec);
-- 
2.23.0.rc1