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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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8
arch/x86/kernel/ftrace.c
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@ -1049,9 +1049,11 @@ void prepare_ftrace_return(unsigned long self_addr, unsigned long *parent,
* return address is actually off by one word, and we
* need to adjust for that.
*/
if (ftrace_find_direct_func(self_addr + MCOUNT_INSN_SIZE)) {
self_addr = *parent;
parent++;
if (ftrace_direct_func_count) {
if (ftrace_find_direct_func(self_addr + MCOUNT_INSN_SIZE)) {
self_addr = *parent;
parent++;
}
}
/*