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, 119 insertions, 0 deletions

diff --git a/tools/perf/util/clockid.c b/tools/perf/util/clockid.c
new file mode 100644
index 000000000..74365a5d9
--- /dev/null
+++ b/tools/perf/util/clockid.c
@@ -0,0 +1,119 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <subcmd/parse-options.h>
+#include <stdio.h>
+#include <time.h>
+#include <strings.h>
+#include <linux/time64.h>
+#include "debug.h"
+#include "clockid.h"
+#include "record.h"
+
+struct clockid_map {
+	const char *name;
+	int clockid;
+};
+
+#define CLOCKID_MAP(n, c)	\
+	{ .name = n, .clockid = (c), }
+
+#define CLOCKID_END	{ .name = NULL, }
+
+
+/*
+ * Add the missing ones, we need to build on many distros...
+ */
+#ifndef CLOCK_MONOTONIC_RAW
+#define CLOCK_MONOTONIC_RAW 4
+#endif
+#ifndef CLOCK_BOOTTIME
+#define CLOCK_BOOTTIME 7
+#endif
+#ifndef CLOCK_TAI
+#define CLOCK_TAI 11
+#endif
+
+static const struct clockid_map clockids[] = {
+	/* available for all events, NMI safe */
+	CLOCKID_MAP("monotonic", CLOCK_MONOTONIC),
+	CLOCKID_MAP("monotonic_raw", CLOCK_MONOTONIC_RAW),
+
+	/* available for some events */
+	CLOCKID_MAP("realtime", CLOCK_REALTIME),
+	CLOCKID_MAP("boottime", CLOCK_BOOTTIME),
+	CLOCKID_MAP("tai", CLOCK_TAI),
+
+	/* available for the lazy */
+	CLOCKID_MAP("mono", CLOCK_MONOTONIC),
+	CLOCKID_MAP("raw", CLOCK_MONOTONIC_RAW),
+	CLOCKID_MAP("real", CLOCK_REALTIME),
+	CLOCKID_MAP("boot", CLOCK_BOOTTIME),
+
+	CLOCKID_END,
+};
+
+static int get_clockid_res(clockid_t clk_id, u64 *res_ns)
+{
+	struct timespec res;
+
+	*res_ns = 0;
+	if (!clock_getres(clk_id, &res))
+		*res_ns = res.tv_nsec + res.tv_sec * NSEC_PER_SEC;
+	else
+		pr_warning("WARNING: Failed to determine specified clock resolution.\n");
+
+	return 0;
+}
+
+int parse_clockid(const struct option *opt, const char *str, int unset)
+{
+	struct record_opts *opts = (struct record_opts *)opt->value;
+	const struct clockid_map *cm;
+	const char *ostr = str;
+
+	if (unset) {
+		opts->use_clockid = 0;
+		return 0;
+	}
+
+	/* no arg passed */
+	if (!str)
+		return 0;
+
+	/* no setting it twice */
+	if (opts->use_clockid)
+		return -1;
+
+	opts->use_clockid = true;
+
+	/* if its a number, we're done */
+	if (sscanf(str, "%d", &opts->clockid) == 1)
+		return get_clockid_res(opts->clockid, &opts->clockid_res_ns);
+
+	/* allow a "CLOCK_" prefix to the name */
+	if (!strncasecmp(str, "CLOCK_", 6))
+		str += 6;
+
+	for (cm = clockids; cm->name; cm++) {
+		if (!strcasecmp(str, cm->name)) {
+			opts->clockid = cm->clockid;
+			return get_clockid_res(opts->clockid,
+					       &opts->clockid_res_ns);
+		}
+	}
+
+	opts->use_clockid = false;
+	ui__warning("unknown clockid %s, check man page\n", ostr);
+	return -1;
+}
+
+const char *clockid_name(clockid_t clk_id)
+{
+	const struct clockid_map *cm;
+
+	for (cm = clockids; cm->name; cm++) {
+		if (cm->clockid == clk_id)
+			return cm->name;
+	}
+	return "(not found)";
+}