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Subject[PATCH V7 08/15] ftrace: Add perf text poke events for ftrace trampolines
Date
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>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
kernel/trace/ftrace.c | 14 ++++++++++++++
1 file changed, 14 insertions(+)

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 1103a8fcf142..abdf8f415a6e 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -2802,6 +2802,13 @@ 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);
@@ -6826,6 +6833,13 @@ 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);
}
}

--
2.17.1
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