ftrace: Synchronize the initialization of ftrace_opsgrafted

There's some internal state that ftrace_ops needs to have set, but since
it can be declared outside of the ftrace.c code, it calls
ftrace_ops_init() on the ops in every global function. The issue is that
if two tasks call it on the same ops at the same time it is possible to
have the initialization of one corrupt the initialization of the other
call.

Create a ops_mutex to use to synchronize every initialization of the
ftrace_ops. The mutex is taken within checking the ftrace_ops flag that
states it was initializied but the flag is checked again after the mutex
has been taken. Checking first outside the mutex allows it to shortcut
having to take the mutex. But then the check needs to be done again after
the mute is taken in case of races.

Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260902095501.6b59af20@gandalf.local.home
Fixes: f04f24fb7e48d ("ftrace, kprobes: Fix a deadlock on ftrace_regex_lock")
Reported-by: sashiko-bot@kernel.org
Close: https://lore.kernel.org/all/20260829025528.49A831F000E9@smtp.kernel.org/
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 121 insertions, 0 deletions

diff --git a/tools/perf/tests/stat.c b/tools/perf/tests/stat.c
new file mode 100644
index 000000000..d60983657
--- /dev/null
+++ b/tools/perf/tests/stat.c
@@ -0,0 +1,121 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/compiler.h>
+#include "event.h"
+#include "tests.h"
+#include "stat.h"
+#include "counts.h"
+#include "debug.h"
+#include "util/synthetic-events.h"
+
+static bool has_term(struct perf_record_stat_config *config,
+		     u64 tag, u64 val)
+{
+	unsigned i;
+
+	for (i = 0; i < config->nr; i++) {
+		if ((config->data[i].tag == tag) &&
+		    (config->data[i].val == val))
+			return true;
+	}
+
+	return false;
+}
+
+static int process_stat_config_event(const struct perf_tool *tool __maybe_unused,
+				     union perf_event *event,
+				     struct perf_sample *sample __maybe_unused,
+				     struct machine *machine __maybe_unused)
+{
+	struct perf_record_stat_config *config = &event->stat_config;
+	struct perf_stat_config test_stat_config = {};
+
+#define HAS(term, val) \
+	has_term(config, PERF_STAT_CONFIG_TERM__##term, val)
+
+	TEST_ASSERT_VAL("wrong nr",        config->nr == PERF_STAT_CONFIG_TERM__MAX);
+	TEST_ASSERT_VAL("wrong aggr_mode", HAS(AGGR_MODE, AGGR_CORE));
+	TEST_ASSERT_VAL("wrong scale",     HAS(SCALE, 1));
+	TEST_ASSERT_VAL("wrong interval",  HAS(INTERVAL, 1));
+
+#undef HAS
+
+	perf_event__read_stat_config(&test_stat_config, config);
+
+	TEST_ASSERT_VAL("wrong aggr_mode", test_stat_config.aggr_mode == AGGR_CORE);
+	TEST_ASSERT_VAL("wrong scale",     test_stat_config.scale == 1);
+	TEST_ASSERT_VAL("wrong interval",  test_stat_config.interval == 1);
+	return 0;
+}
+
+static int test__synthesize_stat_config(struct test_suite *test __maybe_unused,
+					int subtest __maybe_unused)
+{
+	struct perf_stat_config test_stat_config = {
+		.aggr_mode	= AGGR_CORE,
+		.scale		= 1,
+		.interval	= 1,
+	};
+
+	TEST_ASSERT_VAL("failed to synthesize stat_config",
+		!perf_event__synthesize_stat_config(NULL, &test_stat_config,
+						    process_stat_config_event,
+						    NULL));
+
+	return 0;
+}
+
+static int process_stat_event(const struct perf_tool *tool __maybe_unused,
+			      union perf_event *event,
+			      struct perf_sample *sample __maybe_unused,
+			      struct machine *machine __maybe_unused)
+{
+	struct perf_record_stat *st = &event->stat;
+
+	TEST_ASSERT_VAL("wrong cpu",    st->cpu    == 1);
+	TEST_ASSERT_VAL("wrong thread", st->thread == 2);
+	TEST_ASSERT_VAL("wrong id",     st->id     == 3);
+	TEST_ASSERT_VAL("wrong val",    st->val    == 100);
+	TEST_ASSERT_VAL("wrong run",    st->ena    == 200);
+	TEST_ASSERT_VAL("wrong ena",    st->run    == 300);
+	return 0;
+}
+
+static int test__synthesize_stat(struct test_suite *test __maybe_unused, int subtest __maybe_unused)
+{
+	struct perf_counts_values count;
+
+	count.val = 100;
+	count.ena = 200;
+	count.run = 300;
+
+	TEST_ASSERT_VAL("failed to synthesize stat_config",
+			!perf_event__synthesize_stat(NULL, (struct perf_cpu){.cpu = 1}, 2, 3,
+						     &count, process_stat_event, NULL));
+
+	return 0;
+}
+
+static int process_stat_round_event(const struct perf_tool *tool __maybe_unused,
+				    union perf_event *event,
+				    struct perf_sample *sample __maybe_unused,
+				    struct machine *machine __maybe_unused)
+{
+	struct perf_record_stat_round *stat_round = &event->stat_round;
+
+	TEST_ASSERT_VAL("wrong time", stat_round->time == 0xdeadbeef);
+	TEST_ASSERT_VAL("wrong type", stat_round->type == PERF_STAT_ROUND_TYPE__INTERVAL);
+	return 0;
+}
+
+static int test__synthesize_stat_round(struct test_suite *test __maybe_unused, int subtest __maybe_unused)
+{
+	TEST_ASSERT_VAL("failed to synthesize stat_config",
+		!perf_event__synthesize_stat_round(NULL, 0xdeadbeef, PERF_STAT_ROUND_TYPE__INTERVAL,
+						   process_stat_round_event, NULL));
+
+	return 0;
+}
+
+DEFINE_SUITE("Synthesize stat config", synthesize_stat_config);
+DEFINE_SUITE("Synthesize stat", synthesize_stat);
+DEFINE_SUITE("Synthesize stat round", synthesize_stat_round);