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, 127 insertions, 0 deletions

diff --git a/tools/perf/util/trace-event.c b/tools/perf/util/trace-event.c
new file mode 100644
index 000000000..000c1e1d6
--- /dev/null
+++ b/tools/perf/util/trace-event.c
@@ -0,0 +1,127 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <stdio.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <errno.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <linux/kernel.h>
+#include <linux/err.h>
+#include <event-parse.h>
+#include <api/fs/tracing_path.h>
+#include <api/fs/fs.h>
+#include "trace-event.h"
+#include "machine.h"
+
+/*
+ * global trace_event object used by trace_event__tp_format
+ *
+ * TODO There's no cleanup call for this. Add some sort of
+ * __exit function support and call trace_event__cleanup
+ * there.
+ */
+static struct trace_event tevent;
+static bool tevent_initialized;
+
+int trace_event__init(struct trace_event *t)
+{
+	struct tep_handle *pevent;
+
+	trace_event__cleanup(t);
+
+	pevent = tep_alloc();
+
+	if (pevent) {
+		t->plugin_list = tep_load_plugins(pevent);
+		t->pevent  = pevent;
+	}
+
+	return pevent ? 0 : -1;
+}
+
+static int trace_event__init2(void)
+{
+	int be = tep_is_bigendian();
+	struct tep_handle *pevent;
+
+	if (trace_event__init(&tevent))
+		return -1;
+
+	pevent = tevent.pevent;
+	tep_set_flag(pevent, TEP_NSEC_OUTPUT);
+	tep_set_file_bigendian(pevent, be);
+	tep_set_local_bigendian(pevent, be);
+	tevent_initialized = true;
+	return 0;
+}
+
+int trace_event__register_resolver(struct machine *machine,
+				   tep_func_resolver_t *func)
+{
+	if (!tevent_initialized && trace_event__init2())
+		return -1;
+
+	return tep_set_function_resolver(tevent.pevent, func, machine);
+}
+
+void trace_event__cleanup(struct trace_event *t)
+{
+	if (!t->pevent)
+		return;
+
+	tep_unload_plugins(t->plugin_list, t->pevent);
+	tep_free(t->pevent);
+	t->pevent = NULL;
+	t->plugin_list = NULL;
+}
+
+/*
+ * Returns pointer with encoded error via <linux/err.h> interface.
+ */
+static struct tep_event*
+tp_format(const char *sys, const char *name)
+{
+	char *tp_dir = get_events_file(sys);
+	struct tep_handle *pevent = tevent.pevent;
+	struct tep_event *event = NULL;
+	char path[PATH_MAX];
+	size_t size;
+	char *data;
+	int err;
+
+	if (!tp_dir)
+		return ERR_PTR(-errno);
+
+	scnprintf(path, PATH_MAX, "%s/%s/format", tp_dir, name);
+	put_events_file(tp_dir);
+
+	err = filename__read_str(path, &data, &size);
+	if (err)
+		return ERR_PTR(err);
+
+	tep_parse_format(pevent, &event, data, size, sys);
+
+	free(data);
+	return event;
+}
+
+/*
+ * Returns pointer with encoded error via <linux/err.h> interface.
+ */
+struct tep_event*
+trace_event__tp_format(const char *sys, const char *name)
+{
+	if (!tevent_initialized && trace_event__init2())
+		return ERR_PTR(-ENOMEM);
+
+	return tp_format(sys, name);
+}
+
+struct tep_event *trace_event__tp_format_id(int id)
+{
+	if (!tevent_initialized && trace_event__init2())
+		return ERR_PTR(-ENOMEM);
+
+	return tep_find_event(tevent.pevent, id);
+}