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, 87 insertions, 0 deletions

diff --git a/lib/dhry_run.c b/lib/dhry_run.c
new file mode 100644
index 000000000..4a6d05ce4
--- /dev/null
+++ b/lib/dhry_run.c
@@ -0,0 +1,87 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Dhrystone benchmark test module
+ *
+ * Copyright (C) 2022 Glider bv
+ */
+
+#include "dhry.h"
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+#include <linux/smp.h>
+
+#define DHRY_VAX	1757
+
+static int dhry_run_set(const char *val, const struct kernel_param *kp);
+static const struct kernel_param_ops run_ops = {
+	.flags = KERNEL_PARAM_OPS_FL_NOARG,
+	.set = dhry_run_set,
+};
+static bool dhry_run;
+module_param_cb(run, &run_ops, &dhry_run, 0200);
+MODULE_PARM_DESC(run, "Run the test (default: false)");
+
+static int iterations = -1;
+module_param(iterations, int, 0644);
+MODULE_PARM_DESC(iterations,
+		"Number of iterations through the benchmark (default: auto)");
+
+static void dhry_benchmark(void)
+{
+	unsigned int cpu = get_cpu();
+	int i, n;
+
+	if (iterations > 0) {
+		n = dhry(iterations);
+		goto report;
+	}
+
+	for (i = DHRY_VAX; i > 0; i <<= 1) {
+		n = dhry(i);
+		if (n != -EAGAIN)
+			break;
+	}
+
+report:
+	put_cpu();
+	if (n >= 0)
+		pr_info("CPU%u: Dhrystones per Second: %d (%d DMIPS)\n", cpu,
+			n, n / DHRY_VAX);
+	else if (n == -EAGAIN)
+		pr_err("Please increase the number of iterations\n");
+	else
+		pr_err("Dhrystone benchmark failed error %pe\n", ERR_PTR(n));
+}
+
+static int dhry_run_set(const char *val, const struct kernel_param *kp)
+{
+	int ret;
+
+	if (val) {
+		ret = param_set_bool(val, kp);
+		if (ret)
+			return ret;
+	} else {
+		dhry_run = true;
+	}
+
+	if (dhry_run && system_state == SYSTEM_RUNNING)
+		dhry_benchmark();
+
+	return 0;
+}
+
+static int __init dhry_init(void)
+{
+	if (dhry_run)
+		dhry_benchmark();
+
+	return 0;
+}
+module_init(dhry_init);
+
+MODULE_AUTHOR("Geert Uytterhoeven <geert+renesas@glider.be>");
+MODULE_DESCRIPTION("Dhrystone benchmark test module");
+MODULE_LICENSE("GPL");