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ftrace/x86: Add a counter to test function_graph with direct

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As testing for direct calls from the function graph tracer adds a little
overhead (which is a lot when tracing every function), add a counter that
can be used to test if function_graph tracer needs to test for a direct
caller or not.

It would have been nicer if we could use a static branch, but the static
branch logic fails when used within the function graph tracer trampoline.

Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
This commit is contained in:
Steven Rostedt (VMware) 2019-11-08 13:12:57 -05:00
parent 562955fe6a
commit a3ad1a7e39
3 changed files with 11 additions and 3 deletions
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2
include/linux/ftrace.h
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@ -247,10 +247,12 @@ static inline void ftrace_free_mem(struct module *mod, void *start, void *end) {
#endif /* CONFIG_FUNCTION_TRACER */
#ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
extern int ftrace_direct_func_count;
int register_ftrace_direct(unsigned long ip, unsigned long addr);
int unregister_ftrace_direct(unsigned long ip, unsigned long addr);
struct ftrace_direct_func *ftrace_find_direct_func(unsigned long addr);
#else
# define ftrace_direct_func_count 0
static inline int register_ftrace_direct(unsigned long ip, unsigned long addr)
{
return -ENODEV;