tracing/probes: Avoid setting TPARG_FL_FENTRY and TPARG_FL_RETURN

When parsing a kprobe event, the return probe always sets both
TPARG_FL_RETURN and TPARG_FL_FENTRY, but this is not useful because
some fetchargs are only for return probe and some others only for
function entry. Make it obviously mutual exclusive.

Link: https://lore.kernel.org/all/168507468731.913472.11354553441385410734.stgit@mhiramat.roam.corp.google.com/
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>

diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index 59cda19a9033302bfa50a575e6aad091edf34498..867ffb7ee31dbfa357fdfb9b336e72a3583550cf 100644 (file)
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -825,7 +825,7 @@ static int __trace_kprobe_create(int argc, const char *argv[])
                if (is_return)
                        flags |= TPARG_FL_RETURN;
                ret = kprobe_on_func_entry(NULL, symbol, offset);
-               if (ret == 0)
+               if (ret == 0 && !is_return)
                        flags |= TPARG_FL_FENTRY;
                /* Defer the ENOENT case until register kprobe */
                if (ret == -EINVAL && is_return) {

diff --git a/kernel/trace/trace_probe.h b/kernel/trace/trace_probe.h
index 6a4ecfb1da438743d4b8fc3c0182b22bd135c134..5df59714f9f5cd502354211f5d8e4741146ca2df 100644 (file)
--- a/kernel/trace/trace_probe.h
+++ b/kernel/trace/trace_probe.h
@@ -357,6 +357,11 @@ int trace_probe_print_args(struct trace_seq *s, struct probe_arg *args, int nr_a
 #define trace_probe_for_each_link_rcu(pos, tp) \
        list_for_each_entry_rcu(pos, &(tp)->event->files, list)
 
+/*
+ * The flags used for parsing trace_probe arguments.
+ * TPARG_FL_RETURN, TPARG_FL_FENTRY and TPARG_FL_TPOINT are mutually exclusive.
+ * TPARG_FL_KERNEL and TPARG_FL_USER are also mutually exclusive.
+ */
 #define TPARG_FL_RETURN BIT(0)
 #define TPARG_FL_KERNEL BIT(1)
 #define TPARG_FL_FENTRY BIT(2)