Commit 548e1f6c authored May 12, 2020 by Adrian Hunter Committed by Peter Zijlstra Jun 15, 2020

ftrace: Add perf text poke events for ftrace trampolines



Add perf text poke events for ftrace trampolines when created and when
freed.

There can be 3 text_poke events for ftrace trampolines:

1. NULL -> trampoline
   By ftrace_update_trampoline() when !ops->trampoline
   Trampoline created

2. [e.g. on x86] CALL rel32 -> CALL rel32
   By arch_ftrace_update_trampoline() when ops->trampoline and
                        ops->flags & FTRACE_OPS_FL_ALLOC_TRAMP
   [e.g. on x86] via text_poke_bp() which generates text poke events
   Trampoline-called function target updated

3. trampoline -> NULL
   By ftrace_trampoline_free() when ops->trampoline and
                 ops->flags & FTRACE_OPS_FL_ALLOC_TRAMP
   Trampoline freed

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200512121922.8997-9-adrian.hunter@intel.com

parent dd9ddf46

kernel/trace/ftrace.c

+14 −0

Original line number	Diff line number	Diff line
		@@ -2791,6 +2791,13 @@ static void ftrace_trampoline_free(struct ftrace_ops *ops)
		{
		if (ops && (ops->flags & FTRACE_OPS_FL_ALLOC_TRAMP) &&
		ops->trampoline) {
		/*
		* Record the text poke event before the ksymbol unregister
		* event.
		*/
		perf_event_text_poke((void *)ops->trampoline,
		(void *)ops->trampoline,
		ops->trampoline_size, NULL, 0);
		perf_event_ksymbol(PERF_RECORD_KSYMBOL_TYPE_OOL,
		ops->trampoline, ops->trampoline_size,
		true, FTRACE_TRAMPOLINE_SYM);
		@@ -6816,6 +6823,13 @@ static void ftrace_update_trampoline(struct ftrace_ops *ops)
		perf_event_ksymbol(PERF_RECORD_KSYMBOL_TYPE_OOL,
		ops->trampoline, ops->trampoline_size, false,
		FTRACE_TRAMPOLINE_SYM);
		/*
		* Record the perf text poke event after the ksymbol register
		* event.
		*/
		perf_event_text_poke((void *)ops->trampoline, NULL, 0,
		(void *)ops->trampoline,
		ops->trampoline_size);
		}
		}

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