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, 339 insertions, 0 deletions

diff --git a/drivers/regulator/max8952.c b/drivers/regulator/max8952.c
new file mode 100644
index 000000000..f8b91a570
--- /dev/null
+++ b/drivers/regulator/max8952.c
@@ -0,0 +1,339 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * max8952.c - Voltage and current regulation for the Maxim 8952
+ *
+ * Copyright (C) 2010 Samsung Electronics
+ * MyungJoo Ham <myungjoo.ham@samsung.com>
+ */
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/i2c.h>
+#include <linux/err.h>
+#include <linux/platform_device.h>
+#include <linux/regulator/driver.h>
+#include <linux/regulator/max8952.h>
+#include <linux/gpio/consumer.h>
+#include <linux/io.h>
+#include <linux/of.h>
+#include <linux/regulator/of_regulator.h>
+#include <linux/slab.h>
+
+/* Registers */
+enum {
+	MAX8952_REG_MODE0,
+	MAX8952_REG_MODE1,
+	MAX8952_REG_MODE2,
+	MAX8952_REG_MODE3,
+	MAX8952_REG_CONTROL,
+	MAX8952_REG_SYNC,
+	MAX8952_REG_RAMP,
+	MAX8952_REG_CHIP_ID1,
+	MAX8952_REG_CHIP_ID2,
+};
+
+struct max8952_data {
+	struct i2c_client	*client;
+	struct max8952_platform_data *pdata;
+	struct gpio_desc *vid0_gpiod;
+	struct gpio_desc *vid1_gpiod;
+	bool vid0;
+	bool vid1;
+};
+
+static int max8952_read_reg(struct max8952_data *max8952, u8 reg)
+{
+	int ret = i2c_smbus_read_byte_data(max8952->client, reg);
+
+	if (ret > 0)
+		ret &= 0xff;
+
+	return ret;
+}
+
+static int max8952_write_reg(struct max8952_data *max8952,
+		u8 reg, u8 value)
+{
+	return i2c_smbus_write_byte_data(max8952->client, reg, value);
+}
+
+static int max8952_list_voltage(struct regulator_dev *rdev,
+		unsigned int selector)
+{
+	struct max8952_data *max8952 = rdev_get_drvdata(rdev);
+
+	if (rdev_get_id(rdev) != 0)
+		return -EINVAL;
+
+	return (max8952->pdata->dvs_mode[selector] * 10 + 770) * 1000;
+}
+
+static int max8952_get_voltage_sel(struct regulator_dev *rdev)
+{
+	struct max8952_data *max8952 = rdev_get_drvdata(rdev);
+	u8 vid = 0;
+
+	if (max8952->vid0)
+		vid += 1;
+	if (max8952->vid1)
+		vid += 2;
+
+	return vid;
+}
+
+static int max8952_set_voltage_sel(struct regulator_dev *rdev,
+				   unsigned selector)
+{
+	struct max8952_data *max8952 = rdev_get_drvdata(rdev);
+
+	if (!max8952->vid0_gpiod || !max8952->vid1_gpiod) {
+		/* DVS not supported */
+		return -EPERM;
+	}
+
+	max8952->vid0 = selector & 0x1;
+	max8952->vid1 = (selector >> 1) & 0x1;
+	gpiod_set_value(max8952->vid0_gpiod, max8952->vid0);
+	gpiod_set_value(max8952->vid1_gpiod, max8952->vid1);
+
+	return 0;
+}
+
+static const struct regulator_ops max8952_ops = {
+	.list_voltage		= max8952_list_voltage,
+	.get_voltage_sel	= max8952_get_voltage_sel,
+	.set_voltage_sel	= max8952_set_voltage_sel,
+};
+
+static const struct regulator_desc regulator = {
+	.name		= "MAX8952_VOUT",
+	.id		= 0,
+	.n_voltages	= MAX8952_NUM_DVS_MODE,
+	.ops		= &max8952_ops,
+	.type		= REGULATOR_VOLTAGE,
+	.owner		= THIS_MODULE,
+};
+
+#ifdef CONFIG_OF
+static const struct of_device_id max8952_dt_match[] = {
+	{ .compatible = "maxim,max8952" },
+	{},
+};
+MODULE_DEVICE_TABLE(of, max8952_dt_match);
+
+static struct max8952_platform_data *max8952_parse_dt(struct device *dev)
+{
+	struct max8952_platform_data *pd;
+	struct device_node *np = dev->of_node;
+	int ret;
+	int i;
+
+	pd = devm_kzalloc(dev, sizeof(*pd), GFP_KERNEL);
+	if (!pd)
+		return NULL;
+
+	if (of_property_read_u32(np, "max8952,default-mode", &pd->default_mode))
+		dev_warn(dev, "Default mode not specified, assuming 0\n");
+
+	ret = of_property_read_u32_array(np, "max8952,dvs-mode-microvolt",
+					pd->dvs_mode, ARRAY_SIZE(pd->dvs_mode));
+	if (ret) {
+		dev_err(dev, "max8952,dvs-mode-microvolt property not specified");
+		return NULL;
+	}
+
+	for (i = 0; i < ARRAY_SIZE(pd->dvs_mode); ++i) {
+		if (pd->dvs_mode[i] < 770000 || pd->dvs_mode[i] > 1400000) {
+			dev_err(dev, "DVS voltage %d out of range\n", i);
+			return NULL;
+		}
+		pd->dvs_mode[i] = (pd->dvs_mode[i] - 770000) / 10000;
+	}
+
+	if (of_property_read_u32(np, "max8952,sync-freq", &pd->sync_freq))
+		dev_warn(dev, "max8952,sync-freq property not specified, defaulting to 26MHz\n");
+
+	if (of_property_read_u32(np, "max8952,ramp-speed", &pd->ramp_speed))
+		dev_warn(dev, "max8952,ramp-speed property not specified, defaulting to 32mV/us\n");
+
+	pd->reg_data = of_get_regulator_init_data(dev, np, &regulator);
+	if (!pd->reg_data) {
+		dev_err(dev, "Failed to parse regulator init data\n");
+		return NULL;
+	}
+
+	return pd;
+}
+#else
+static struct max8952_platform_data *max8952_parse_dt(struct device *dev)
+{
+	return NULL;
+}
+#endif
+
+static int max8952_pmic_probe(struct i2c_client *client)
+{
+	struct i2c_adapter *adapter = client->adapter;
+	struct max8952_platform_data *pdata = dev_get_platdata(&client->dev);
+	struct regulator_config config = { };
+	struct max8952_data *max8952;
+	struct regulator_dev *rdev;
+	struct gpio_desc *gpiod;
+	enum gpiod_flags gflags;
+
+	int ret = 0;
+
+	if (client->dev.of_node)
+		pdata = max8952_parse_dt(&client->dev);
+
+	if (!pdata) {
+		dev_err(&client->dev, "Require the platform data\n");
+		return -EINVAL;
+	}
+
+	if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE))
+		return -EIO;
+
+	max8952 = devm_kzalloc(&client->dev, sizeof(struct max8952_data),
+			       GFP_KERNEL);
+	if (!max8952)
+		return -ENOMEM;
+
+	max8952->client = client;
+	max8952->pdata = pdata;
+
+	config.dev = &client->dev;
+	config.init_data = pdata->reg_data;
+	config.driver_data = max8952;
+	config.of_node = client->dev.of_node;
+
+	if (pdata->reg_data->constraints.boot_on)
+		gflags = GPIOD_OUT_HIGH;
+	else
+		gflags = GPIOD_OUT_LOW;
+	gflags |= GPIOD_FLAGS_BIT_NONEXCLUSIVE;
+	/*
+	 * Do not use devm* here: the regulator core takes over the
+	 * lifecycle management of the GPIO descriptor.
+	 */
+	gpiod = gpiod_get_optional(&client->dev,
+				   "max8952,en",
+				   gflags);
+	if (IS_ERR(gpiod))
+		return PTR_ERR(gpiod);
+	if (gpiod)
+		config.ena_gpiod = gpiod;
+
+	rdev = devm_regulator_register(&client->dev, &regulator, &config);
+	if (IS_ERR(rdev)) {
+		ret = PTR_ERR(rdev);
+		dev_err(&client->dev, "regulator init failed (%d)\n", ret);
+		return ret;
+	}
+
+	max8952->vid0 = pdata->default_mode & 0x1;
+	max8952->vid1 = (pdata->default_mode >> 1) & 0x1;
+
+	/* Fetch vid0 and vid1 GPIOs if available */
+	gflags = max8952->vid0 ? GPIOD_OUT_HIGH : GPIOD_OUT_LOW;
+	max8952->vid0_gpiod = devm_gpiod_get_index_optional(&client->dev,
+							    "max8952,vid",
+							    0, gflags);
+	if (IS_ERR(max8952->vid0_gpiod))
+		return PTR_ERR(max8952->vid0_gpiod);
+	gflags = max8952->vid1 ? GPIOD_OUT_HIGH : GPIOD_OUT_LOW;
+	max8952->vid1_gpiod = devm_gpiod_get_index_optional(&client->dev,
+							    "max8952,vid",
+							    1, gflags);
+	if (IS_ERR(max8952->vid1_gpiod))
+		return PTR_ERR(max8952->vid1_gpiod);
+
+	/* If either VID GPIO is missing just disable this */
+	if (!max8952->vid0_gpiod || !max8952->vid1_gpiod) {
+		dev_warn(&client->dev, "VID0/1 gpio invalid: "
+			 "DVS not available.\n");
+		max8952->vid0 = 0;
+		max8952->vid1 = 0;
+		/* Make sure if we have any descriptors they get set to low */
+		if (max8952->vid0_gpiod)
+			gpiod_set_value(max8952->vid0_gpiod, 0);
+		if (max8952->vid1_gpiod)
+			gpiod_set_value(max8952->vid1_gpiod, 0);
+
+		/* Disable Pulldown of EN only */
+		max8952_write_reg(max8952, MAX8952_REG_CONTROL, 0x60);
+
+		dev_err(&client->dev, "DVS modes disabled because VID0 and VID1"
+				" do not have proper controls.\n");
+	} else {
+		/*
+		 * Disable Pulldown on EN, VID0, VID1 to reduce
+		 * leakage current of MAX8952 assuming that MAX8952
+		 * is turned on (EN==1). Note that without having VID0/1
+		 * properly connected, turning pulldown off can be
+		 * problematic. Thus, turn this off only when they are
+		 * controllable by GPIO.
+		 */
+		max8952_write_reg(max8952, MAX8952_REG_CONTROL, 0x0);
+	}
+
+	max8952_write_reg(max8952, MAX8952_REG_MODE0,
+			(max8952_read_reg(max8952,
+					  MAX8952_REG_MODE0) & 0xC0) |
+			(pdata->dvs_mode[0] & 0x3F));
+	max8952_write_reg(max8952, MAX8952_REG_MODE1,
+			(max8952_read_reg(max8952,
+					  MAX8952_REG_MODE1) & 0xC0) |
+			(pdata->dvs_mode[1] & 0x3F));
+	max8952_write_reg(max8952, MAX8952_REG_MODE2,
+			(max8952_read_reg(max8952,
+					  MAX8952_REG_MODE2) & 0xC0) |
+			(pdata->dvs_mode[2] & 0x3F));
+	max8952_write_reg(max8952, MAX8952_REG_MODE3,
+			(max8952_read_reg(max8952,
+					  MAX8952_REG_MODE3) & 0xC0) |
+			(pdata->dvs_mode[3] & 0x3F));
+
+	max8952_write_reg(max8952, MAX8952_REG_SYNC,
+			(max8952_read_reg(max8952, MAX8952_REG_SYNC) & 0x3F) |
+			((pdata->sync_freq & 0x3) << 6));
+	max8952_write_reg(max8952, MAX8952_REG_RAMP,
+			(max8952_read_reg(max8952, MAX8952_REG_RAMP) & 0x1F) |
+			((pdata->ramp_speed & 0x7) << 5));
+
+	i2c_set_clientdata(client, max8952);
+
+	return 0;
+}
+
+static const struct i2c_device_id max8952_ids[] = {
+	{ .name = "max8952" },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, max8952_ids);
+
+static struct i2c_driver max8952_pmic_driver = {
+	.probe		= max8952_pmic_probe,
+	.driver		= {
+		.name	= "max8952",
+		.probe_type = PROBE_PREFER_ASYNCHRONOUS,
+		.of_match_table = of_match_ptr(max8952_dt_match),
+	},
+	.id_table	= max8952_ids,
+};
+
+static int __init max8952_pmic_init(void)
+{
+	return i2c_add_driver(&max8952_pmic_driver);
+}
+subsys_initcall(max8952_pmic_init);
+
+static void __exit max8952_pmic_exit(void)
+{
+	i2c_del_driver(&max8952_pmic_driver);
+}
+module_exit(max8952_pmic_exit);
+
+MODULE_DESCRIPTION("MAXIM 8952 voltage regulator driver");
+MODULE_AUTHOR("MyungJoo Ham <myungjoo.ham@samsung.com>");
+MODULE_LICENSE("GPL");