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, 98 insertions, 0 deletions

diff --git a/drivers/power/reset/syscon-poweroff.c b/drivers/power/reset/syscon-poweroff.c
new file mode 100644
index 000000000..203936f4c
--- /dev/null
+++ b/drivers/power/reset/syscon-poweroff.c
@@ -0,0 +1,98 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Generic Syscon Poweroff Driver
+ *
+ * Copyright (c) 2015, National Instruments Corp.
+ * Author: Moritz Fischer <moritz.fischer@ettus.com>
+ */
+
+#include <linux/delay.h>
+#include <linux/io.h>
+#include <linux/notifier.h>
+#include <linux/mfd/syscon.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/pm.h>
+#include <linux/reboot.h>
+#include <linux/regmap.h>
+
+struct syscon_poweroff_data {
+	struct regmap *map;
+	u32 offset;
+	u32 value;
+	u32 mask;
+};
+
+static int syscon_poweroff(struct sys_off_data *off_data)
+{
+	struct syscon_poweroff_data *data = off_data->cb_data;
+
+	/* Issue the poweroff */
+	regmap_update_bits(data->map, data->offset, data->mask, data->value);
+
+	mdelay(1000);
+
+	pr_emerg("Unable to poweroff system\n");
+
+	return NOTIFY_DONE;
+}
+
+static int syscon_poweroff_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct syscon_poweroff_data *data;
+	int mask_err, value_err;
+
+	data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	data->map = syscon_regmap_lookup_by_phandle(dev->of_node, "regmap");
+	if (IS_ERR(data->map)) {
+		data->map = syscon_node_to_regmap(dev->parent->of_node);
+		if (IS_ERR(data->map)) {
+			dev_err(dev, "unable to get syscon");
+			return PTR_ERR(data->map);
+		}
+	}
+
+	if (of_property_read_u32(dev->of_node, "offset", &data->offset)) {
+		dev_err(dev, "unable to read 'offset'");
+		return -EINVAL;
+	}
+
+	value_err = of_property_read_u32(dev->of_node, "value", &data->value);
+	mask_err = of_property_read_u32(dev->of_node, "mask", &data->mask);
+	if (value_err && mask_err) {
+		dev_err(dev, "unable to read 'value' and 'mask'");
+		return -EINVAL;
+	}
+
+	if (value_err) {
+		/* support old binding */
+		data->value = data->mask;
+		data->mask = 0xFFFFFFFF;
+	} else if (mask_err) {
+		/* support value without mask*/
+		data->mask = 0xFFFFFFFF;
+	}
+
+	return devm_register_sys_off_handler(&pdev->dev,
+					     SYS_OFF_MODE_POWER_OFF,
+					     SYS_OFF_PRIO_DEFAULT,
+					     syscon_poweroff, data);
+}
+
+static const struct of_device_id syscon_poweroff_of_match[] = {
+	{ .compatible = "syscon-poweroff" },
+	{}
+};
+
+static struct platform_driver syscon_poweroff_driver = {
+	.probe = syscon_poweroff_probe,
+	.driver = {
+		.name = "syscon-poweroff",
+		.of_match_table = syscon_poweroff_of_match,
+	},
+};
+builtin_platform_driver(syscon_poweroff_driver);