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, 321 insertions, 0 deletions

diff --git a/drivers/hwmon/pcf8591.c b/drivers/hwmon/pcf8591.c
new file mode 100644
index 000000000..c0220ebfd
--- /dev/null
+++ b/drivers/hwmon/pcf8591.c
@@ -0,0 +1,321 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (C) 2001-2004 Aurelien Jarno <aurelien@aurel32.net>
+ * Ported to Linux 2.6 by Aurelien Jarno <aurelien@aurel32.net> with
+ * the help of Jean Delvare <jdelvare@suse.de>
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/slab.h>
+#include <linux/i2c.h>
+#include <linux/mutex.h>
+#include <linux/err.h>
+#include <linux/hwmon.h>
+#include <linux/kstrtox.h>
+
+/* Insmod parameters */
+
+static int input_mode;
+module_param(input_mode, int, 0);
+MODULE_PARM_DESC(input_mode,
+	"Analog input mode:\n"
+	" 0 = four single ended inputs\n"
+	" 1 = three differential inputs\n"
+	" 2 = single ended and differential mixed\n"
+	" 3 = two differential inputs\n");
+
+/*
+ * The PCF8591 control byte
+ *      7    6    5    4    3    2    1    0
+ *   |  0 |AOEF|   AIP   |  0 |AINC|  AICH   |
+ */
+
+/* Analog Output Enable Flag (analog output active if 1) */
+#define PCF8591_CONTROL_AOEF		0x40
+
+/*
+ * Analog Input Programming
+ * 0x00 = four single ended inputs
+ * 0x10 = three differential inputs
+ * 0x20 = single ended and differential mixed
+ * 0x30 = two differential inputs
+ */
+#define PCF8591_CONTROL_AIP_MASK	0x30
+
+/* Autoincrement Flag (switch on if 1) */
+#define PCF8591_CONTROL_AINC		0x04
+
+/*
+ * Channel selection
+ * 0x00 = channel 0
+ * 0x01 = channel 1
+ * 0x02 = channel 2
+ * 0x03 = channel 3
+ */
+#define PCF8591_CONTROL_AICH_MASK	0x03
+
+/* Initial values */
+#define PCF8591_INIT_CONTROL	((input_mode << 4) | PCF8591_CONTROL_AOEF)
+#define PCF8591_INIT_AOUT	0	/* DAC out = 0 */
+
+/* Conversions */
+#define REG_TO_SIGNED(reg)	(((reg) & 0x80) ? ((reg) - 256) : (reg))
+
+struct pcf8591_data {
+	struct device *hwmon_dev;
+	struct mutex update_lock;
+
+	u8 control;
+	u8 aout;
+};
+
+static void pcf8591_init_client(struct i2c_client *client);
+static int pcf8591_read_channel(struct device *dev, int channel);
+
+/* following are the sysfs callback functions */
+#define show_in_channel(channel)					\
+static ssize_t show_in##channel##_input(struct device *dev,		\
+					struct device_attribute *attr,	\
+					char *buf)			\
+{									\
+	return sprintf(buf, "%d\n", pcf8591_read_channel(dev, channel));\
+}									\
+static DEVICE_ATTR(in##channel##_input, S_IRUGO,			\
+		   show_in##channel##_input, NULL);
+
+show_in_channel(0);
+show_in_channel(1);
+show_in_channel(2);
+show_in_channel(3);
+
+static ssize_t out0_output_show(struct device *dev,
+				struct device_attribute *attr, char *buf)
+{
+	struct pcf8591_data *data = i2c_get_clientdata(to_i2c_client(dev));
+	return sprintf(buf, "%d\n", data->aout * 10);
+}
+
+static ssize_t out0_output_store(struct device *dev,
+				 struct device_attribute *attr,
+				 const char *buf, size_t count)
+{
+	unsigned long val;
+	struct i2c_client *client = to_i2c_client(dev);
+	struct pcf8591_data *data = i2c_get_clientdata(client);
+	int err;
+
+	err = kstrtoul(buf, 10, &val);
+	if (err)
+		return err;
+
+	val /= 10;
+	if (val > 255)
+		return -EINVAL;
+
+	data->aout = val;
+	i2c_smbus_write_byte_data(client, data->control, data->aout);
+	return count;
+}
+
+static DEVICE_ATTR_RW(out0_output);
+
+static ssize_t out0_enable_show(struct device *dev,
+				struct device_attribute *attr, char *buf)
+{
+	struct pcf8591_data *data = i2c_get_clientdata(to_i2c_client(dev));
+	return sprintf(buf, "%u\n", !(!(data->control & PCF8591_CONTROL_AOEF)));
+}
+
+static ssize_t out0_enable_store(struct device *dev,
+				 struct device_attribute *attr,
+				 const char *buf, size_t count)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	struct pcf8591_data *data = i2c_get_clientdata(client);
+	unsigned long val;
+	int err;
+
+	err = kstrtoul(buf, 10, &val);
+	if (err)
+		return err;
+
+	mutex_lock(&data->update_lock);
+	if (val)
+		data->control |= PCF8591_CONTROL_AOEF;
+	else
+		data->control &= ~PCF8591_CONTROL_AOEF;
+	i2c_smbus_write_byte(client, data->control);
+	mutex_unlock(&data->update_lock);
+	return count;
+}
+
+static DEVICE_ATTR_RW(out0_enable);
+
+static struct attribute *pcf8591_attributes[] = {
+	&dev_attr_out0_enable.attr,
+	&dev_attr_out0_output.attr,
+	&dev_attr_in0_input.attr,
+	&dev_attr_in1_input.attr,
+	NULL
+};
+
+static const struct attribute_group pcf8591_attr_group = {
+	.attrs = pcf8591_attributes,
+};
+
+static struct attribute *pcf8591_attributes_opt[] = {
+	&dev_attr_in2_input.attr,
+	&dev_attr_in3_input.attr,
+	NULL
+};
+
+static const struct attribute_group pcf8591_attr_group_opt = {
+	.attrs = pcf8591_attributes_opt,
+};
+
+/*
+ * Real code
+ */
+
+static int pcf8591_probe(struct i2c_client *client)
+{
+	struct pcf8591_data *data;
+	int err;
+
+	data = devm_kzalloc(&client->dev, sizeof(struct pcf8591_data),
+			    GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	i2c_set_clientdata(client, data);
+	mutex_init(&data->update_lock);
+
+	/* Initialize the PCF8591 chip */
+	pcf8591_init_client(client);
+
+	/* Register sysfs hooks */
+	err = sysfs_create_group(&client->dev.kobj, &pcf8591_attr_group);
+	if (err)
+		return err;
+
+	/* Register input2 if not in "two differential inputs" mode */
+	if (input_mode != 3) {
+		err = device_create_file(&client->dev, &dev_attr_in2_input);
+		if (err)
+			goto exit_sysfs_remove;
+	}
+
+	/* Register input3 only in "four single ended inputs" mode */
+	if (input_mode == 0) {
+		err = device_create_file(&client->dev, &dev_attr_in3_input);
+		if (err)
+			goto exit_sysfs_remove;
+	}
+
+	data->hwmon_dev = hwmon_device_register(&client->dev);
+	if (IS_ERR(data->hwmon_dev)) {
+		err = PTR_ERR(data->hwmon_dev);
+		goto exit_sysfs_remove;
+	}
+
+	return 0;
+
+exit_sysfs_remove:
+	sysfs_remove_group(&client->dev.kobj, &pcf8591_attr_group_opt);
+	sysfs_remove_group(&client->dev.kobj, &pcf8591_attr_group);
+	return err;
+}
+
+static void pcf8591_remove(struct i2c_client *client)
+{
+	struct pcf8591_data *data = i2c_get_clientdata(client);
+
+	hwmon_device_unregister(data->hwmon_dev);
+	sysfs_remove_group(&client->dev.kobj, &pcf8591_attr_group_opt);
+	sysfs_remove_group(&client->dev.kobj, &pcf8591_attr_group);
+}
+
+/* Called when we have found a new PCF8591. */
+static void pcf8591_init_client(struct i2c_client *client)
+{
+	struct pcf8591_data *data = i2c_get_clientdata(client);
+	data->control = PCF8591_INIT_CONTROL;
+	data->aout = PCF8591_INIT_AOUT;
+
+	i2c_smbus_write_byte_data(client, data->control, data->aout);
+
+	/*
+	 * The first byte transmitted contains the conversion code of the
+	 * previous read cycle. FLUSH IT!
+	 */
+	i2c_smbus_read_byte(client);
+}
+
+static int pcf8591_read_channel(struct device *dev, int channel)
+{
+	u8 value;
+	struct i2c_client *client = to_i2c_client(dev);
+	struct pcf8591_data *data = i2c_get_clientdata(client);
+
+	mutex_lock(&data->update_lock);
+
+	if ((data->control & PCF8591_CONTROL_AICH_MASK) != channel) {
+		data->control = (data->control & ~PCF8591_CONTROL_AICH_MASK)
+			      | channel;
+		i2c_smbus_write_byte(client, data->control);
+
+		/*
+		 * The first byte transmitted contains the conversion code of
+		 * the previous read cycle. FLUSH IT!
+		 */
+		i2c_smbus_read_byte(client);
+	}
+	value = i2c_smbus_read_byte(client);
+
+	mutex_unlock(&data->update_lock);
+
+	if ((channel == 2 && input_mode == 2) ||
+	    (channel != 3 && (input_mode == 1 || input_mode == 3)))
+		return 10 * REG_TO_SIGNED(value);
+	else
+		return 10 * value;
+}
+
+static const struct i2c_device_id pcf8591_id[] = {
+	{ .name = "pcf8591" },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, pcf8591_id);
+
+static struct i2c_driver pcf8591_driver = {
+	.driver = {
+		.name	= "pcf8591",
+	},
+	.probe		= pcf8591_probe,
+	.remove		= pcf8591_remove,
+	.id_table	= pcf8591_id,
+};
+
+static int __init pcf8591_init(void)
+{
+	if (input_mode < 0 || input_mode > 3) {
+		pr_warn("invalid input_mode (%d)\n", input_mode);
+		input_mode = 0;
+	}
+	return i2c_add_driver(&pcf8591_driver);
+}
+
+static void __exit pcf8591_exit(void)
+{
+	i2c_del_driver(&pcf8591_driver);
+}
+
+MODULE_AUTHOR("Aurelien Jarno <aurelien@aurel32.net>");
+MODULE_DESCRIPTION("PCF8591 driver");
+MODULE_LICENSE("GPL");
+
+module_init(pcf8591_init);
+module_exit(pcf8591_exit);