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, 63 insertions, 0 deletions

diff --git a/drivers/regulator/fixed-helper.c b/drivers/regulator/fixed-helper.c
new file mode 100644
index 000000000..ba5551ac0
--- /dev/null
+++ b/drivers/regulator/fixed-helper.c
@@ -0,0 +1,63 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/slab.h>
+#include <linux/string.h>
+#include <linux/platform_device.h>
+#include <linux/regulator/machine.h>
+#include <linux/regulator/fixed.h>
+
+struct fixed_regulator_data {
+	struct fixed_voltage_config cfg;
+	struct regulator_init_data init_data;
+	struct platform_device pdev;
+};
+
+static void regulator_fixed_release(struct device *dev)
+{
+	struct fixed_regulator_data *data = container_of(dev,
+			struct fixed_regulator_data, pdev.dev);
+	kfree_const(data->cfg.supply_name);
+	kfree(data);
+}
+
+/**
+ * regulator_register_always_on - register an always-on regulator with a fixed name
+ * @id: platform device id
+ * @name: name to be used for the regulator
+ * @supplies: consumers for this regulator
+ * @num_supplies: number of consumers
+ * @uv: voltage in microvolts
+ *
+ * Return: Pointer to registered platform device, or %NULL if memory allocation fails.
+ */
+struct platform_device *regulator_register_always_on(int id, const char *name,
+	struct regulator_consumer_supply *supplies, int num_supplies, int uv)
+{
+	struct fixed_regulator_data *data;
+
+	data = kzalloc_obj(*data);
+	if (!data)
+		return NULL;
+
+	data->cfg.supply_name = kstrdup_const(name, GFP_KERNEL);
+	if (!data->cfg.supply_name) {
+		kfree(data);
+		return NULL;
+	}
+
+	data->cfg.microvolts = uv;
+	data->cfg.enabled_at_boot = 1;
+	data->cfg.init_data = &data->init_data;
+
+	data->init_data.constraints.always_on = 1;
+	data->init_data.consumer_supplies = supplies;
+	data->init_data.num_consumer_supplies = num_supplies;
+
+	data->pdev.name = "reg-fixed-voltage";
+	data->pdev.id = id;
+	data->pdev.dev.platform_data = &data->cfg;
+	data->pdev.dev.release = regulator_fixed_release;
+
+	platform_device_register(&data->pdev);
+
+	return &data->pdev;
+}