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, 73 insertions, 0 deletions

diff --git a/drivers/power/reset/rmobile-reset.c b/drivers/power/reset/rmobile-reset.c
new file mode 100644
index 000000000..7dbc51c32
--- /dev/null
+++ b/drivers/power/reset/rmobile-reset.c
@@ -0,0 +1,73 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Renesas R-Mobile Reset Driver
+ *
+ * Copyright (C) 2014 Glider bvba
+ */
+
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/notifier.h>
+#include <linux/of_address.h>
+#include <linux/platform_device.h>
+#include <linux/printk.h>
+#include <linux/reboot.h>
+
+/* SYSC Register Bank 2 */
+#define RESCNT2		0x20		/* Reset Control Register 2 */
+
+/* Reset Control Register 2 */
+#define RESCNT2_PRES	0x80000000	/* Soft power-on reset */
+
+static int rmobile_reset_handler(struct sys_off_data *data)
+{
+	void __iomem *sysc_base2 = (void __iomem *)data->cb_data;
+
+	/* Let's assume we have acquired the HPB semaphore */
+	writel(RESCNT2_PRES, sysc_base2 + RESCNT2);
+
+	return NOTIFY_DONE;
+}
+
+static int rmobile_reset_probe(struct platform_device *pdev)
+{
+	void __iomem *sysc_base2;
+	int error;
+
+	sysc_base2 = devm_platform_ioremap_resource(pdev, 1);
+	if (IS_ERR(sysc_base2))
+		return PTR_ERR(sysc_base2);
+
+	error = devm_register_sys_off_handler(&pdev->dev,
+					      SYS_OFF_MODE_RESTART,
+					      SYS_OFF_PRIO_HIGH,
+					      rmobile_reset_handler,
+					      (__force void *)sysc_base2);
+	if (error) {
+		dev_err(&pdev->dev,
+			"cannot register restart handler (err=%d)\n", error);
+		return error;
+	}
+
+	return 0;
+}
+
+static const struct of_device_id rmobile_reset_of_match[] = {
+	{ .compatible = "renesas,sysc-rmobile", },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, rmobile_reset_of_match);
+
+static struct platform_driver rmobile_reset_driver = {
+	.probe = rmobile_reset_probe,
+	.driver = {
+		.name = "rmobile_reset",
+		.of_match_table = rmobile_reset_of_match,
+	},
+};
+
+module_platform_driver(rmobile_reset_driver);
+
+MODULE_DESCRIPTION("Renesas R-Mobile Reset Driver");
+MODULE_AUTHOR("Geert Uytterhoeven <geert+renesas@glider.be>");
+MODULE_LICENSE("GPL v2");