[PATCH 04/19] tracing: Add trampoline/graph selftest

Jiri Olsa
2021-06-05T11:10:58Z

Adding selftest for checking that direct trampoline can
co-exist together with graph tracer on same function.

This is supported for CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS
config option, which is defined only for x86_64 for now.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
kernel/trace/trace_selftest.c | 49 ++++++++++++++++++++++++++++++++++-
1 file changed, 48 insertions(+), 1 deletion(-)

diff --git a/kernel/trace/trace_selftest.c b/kernel/trace/trace_selftest.c
index adf7ef194005..f8e55b949cdd 100644
--- a/kernel/trace/trace_selftest.c
+++ b/kernel/trace/trace_selftest.c
@@ -750,6 +750,8 @@ static struct fgraph_ops fgraph_ops __initdata = {
.retfunc = &trace_graph_return,
};

+noinline __noclone static void trace_direct_tramp(void) { }
+
/*
* Pretty much the same than for the function tracer from which the selftest
* has been borrowed.
@@ -760,6 +762,7 @@ trace_selftest_startup_function_graph(struct tracer *trace,
{
int ret;
unsigned long count;
+ char *func_name __maybe_unused;

#ifdef CONFIG_DYNAMIC_FTRACE
if (ftrace_filter_param) {
@@ -808,8 +811,52 @@ trace_selftest_startup_function_graph(struct tracer *trace,
goto out;
}

- /* Don't test dynamic tracing, the function tracer already did */
+#ifdef CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS
+ tracing_reset_online_cpus(&tr->array_buffer);
+ set_graph_array(tr);

+ /*
+ * Some archs *cough*PowerPC*cough* add characters to the
+ * start of the function names. We simply put a '*' to
+ * accommodate them.
+ */
+ func_name = "*" __stringify(DYN_FTRACE_TEST_NAME);
+ ftrace_set_global_filter(func_name, strlen(func_name), 1);
+
+ /*
+ * Register direct function together with graph tracer
+ * and make sure we get graph trace.
+ */
+ ret = register_ftrace_direct((unsigned long) DYN_FTRACE_TEST_NAME,
+ (unsigned long) trace_direct_tramp);
+ if (ret)
+ goto out;
+
+ ret = register_ftrace_graph(&fgraph_ops);
+ if (ret) {
+ warn_failed_init_tracer(trace, ret);
+ goto out;
+ }
+
+ DYN_FTRACE_TEST_NAME();
+
+ count = 0;
+
+ tracing_stop();
+ /* check the trace buffer */
+ ret = trace_test_buffer(&tr->array_buffer, &count);
+
+ unregister_ftrace_graph(&fgraph_ops);
+
+ tracing_start();
+
+ if (!ret && !count) {
+ ret = -1;
+ goto out;
+ }
+#endif
+
+ /* Don't test dynamic tracing, the function tracer already did */
out:
/* Stop it if we failed */
if (ret)
--
2.31.1