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, 253 insertions, 0 deletions

diff --git a/drivers/input/touchscreen/hynitron-cst816x.c b/drivers/input/touchscreen/hynitron-cst816x.c
new file mode 100644
index 000000000..47d9cd741
--- /dev/null
+++ b/drivers/input/touchscreen/hynitron-cst816x.c
@@ -0,0 +1,253 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Driver for I2C connected Hynitron CST816x Series Touchscreen
+ *
+ * Copyright (C) 2025 Oleh Kuzhylnyi <kuzhylol@gmail.com>
+ */
+
+#include <linux/delay.h>
+#include <linux/device.h>
+#include <linux/err.h>
+#include <linux/gpio/consumer.h>
+#include <linux/i2c.h>
+#include <linux/input.h>
+#include <linux/unaligned.h>
+#include <linux/interrupt.h>
+#include <linux/module.h>
+
+#define CST816X_RD_REG		0x01
+#define CST816X_NUM_KEYS	5
+
+struct cst816x_touch {
+	u8 gest;
+	u8 active;
+	u16 abs_x;
+	u16 abs_y;
+} __packed;
+
+struct cst816x_priv {
+	struct i2c_client *client;
+	struct gpio_desc *reset;
+	struct input_dev *input;
+	unsigned int keycode[CST816X_NUM_KEYS];
+	unsigned int keycodemax;
+};
+
+static int cst816x_parse_keycodes(struct device *dev, struct cst816x_priv *priv)
+{
+	int count;
+	int error;
+
+	if (device_property_present(dev, "linux,keycodes")) {
+		count = device_property_count_u32(dev, "linux,keycodes");
+		if (count < 0) {
+			error = count;
+			dev_err(dev, "failed to count keys: %d\n", error);
+			return error;
+		} else if (count > ARRAY_SIZE(priv->keycode)) {
+			dev_err(dev, "too many keys defined: %d\n", count);
+			return -EINVAL;
+		}
+		priv->keycodemax = count;
+
+		error = device_property_read_u32_array(dev, "linux,keycodes",
+						       priv->keycode,
+						       priv->keycodemax);
+		if (error) {
+			dev_err(dev, "failed to read keycodes: %d\n", error);
+			return error;
+		}
+	}
+
+	return 0;
+}
+
+static int cst816x_i2c_read_register(struct cst816x_priv *priv, u8 reg,
+				     void *buf, size_t len)
+{
+	struct i2c_msg xfer[] = {
+		{
+			.addr = priv->client->addr,
+			.flags = 0,
+			.buf = &reg,
+			.len = sizeof(reg),
+		},
+		{
+			.addr = priv->client->addr,
+			.flags = I2C_M_RD,
+			.buf = buf,
+			.len = len,
+		},
+	};
+	int error;
+	int ret;
+
+	ret = i2c_transfer(priv->client->adapter, xfer, ARRAY_SIZE(xfer));
+	if (ret != ARRAY_SIZE(xfer)) {
+		error = ret < 0 ? ret : -EIO;
+		dev_err(&priv->client->dev, "i2c rx err: %d\n", error);
+		return error;
+	}
+
+	return 0;
+}
+
+static u8 cst816x_gest_idx(u8 gest)
+{
+	u8 index;
+
+	switch (gest) {
+	case 0x01: /* Slide up gesture */
+	case 0x02: /* Slide down gesture */
+	case 0x03: /* Slide left gesture */
+	case 0x04: /* Slide right gesture */
+		index = gest;
+		break;
+	case 0x0c: /* Long press gesture */
+	default:
+		index = CST816X_NUM_KEYS;
+		break;
+	}
+
+	return index - 1;
+}
+
+static bool cst816x_process_touch(struct cst816x_priv *priv,
+				  struct cst816x_touch *tch)
+{
+	if (cst816x_i2c_read_register(priv, CST816X_RD_REG, tch, sizeof(*tch)))
+		return false;
+
+	tch->abs_x = get_unaligned_be16(&tch->abs_x) & GENMASK(11, 0);
+	tch->abs_y = get_unaligned_be16(&tch->abs_y) & GENMASK(11, 0);
+
+	dev_dbg(&priv->client->dev, "x: %u, y: %u, t: %u, g: 0x%x\n",
+		tch->abs_x, tch->abs_y, tch->active, tch->gest);
+
+	return true;
+}
+
+static int cst816x_register_input(struct cst816x_priv *priv)
+{
+	priv->input = devm_input_allocate_device(&priv->client->dev);
+	if (!priv->input)
+		return -ENOMEM;
+
+	priv->input->name = "Hynitron CST816x Series Touchscreen";
+	priv->input->phys = "input/ts";
+	priv->input->id.bustype = BUS_I2C;
+
+	input_set_drvdata(priv->input, priv);
+
+	input_set_abs_params(priv->input, ABS_X, 0, 240, 0, 0);
+	input_set_abs_params(priv->input, ABS_Y, 0, 240, 0, 0);
+	input_set_capability(priv->input, EV_KEY, BTN_TOUCH);
+
+	priv->input->keycode = priv->keycode;
+	priv->input->keycodesize = sizeof(priv->keycode[0]);
+	priv->input->keycodemax = priv->keycodemax;
+
+	for (int i = 0; i < priv->keycodemax; i++) {
+		if (priv->keycode[i] == KEY_RESERVED)
+			continue;
+
+		input_set_capability(priv->input, EV_KEY, priv->keycode[i]);
+	}
+
+	return input_register_device(priv->input);
+}
+
+static void cst816x_reset(struct cst816x_priv *priv)
+{
+	gpiod_set_value_cansleep(priv->reset, 1);
+	msleep(50);
+	gpiod_set_value_cansleep(priv->reset, 0);
+	msleep(100);
+}
+
+static irqreturn_t cst816x_irq_cb(int irq, void *cookie)
+{
+	struct cst816x_priv *priv = cookie;
+	struct cst816x_touch tch;
+
+	if (!cst816x_process_touch(priv, &tch))
+		return IRQ_HANDLED;
+
+	input_report_abs(priv->input, ABS_X, tch.abs_x);
+	input_report_abs(priv->input, ABS_Y, tch.abs_y);
+
+	if (tch.gest)
+		input_report_key(priv->input,
+				 priv->keycode[cst816x_gest_idx(tch.gest)],
+				 tch.active);
+
+	input_report_key(priv->input, BTN_TOUCH, tch.active);
+
+	input_sync(priv->input);
+
+	return IRQ_HANDLED;
+}
+
+static int cst816x_probe(struct i2c_client *client)
+{
+	struct device *dev = &client->dev;
+	struct cst816x_priv *priv;
+	int error;
+
+	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	priv->client = client;
+
+	priv->reset = devm_gpiod_get_optional(dev, "reset", GPIOD_OUT_HIGH);
+	if (IS_ERR(priv->reset))
+		return dev_err_probe(dev, PTR_ERR(priv->reset),
+				     "gpio reset request failed\n");
+
+	if (priv->reset)
+		cst816x_reset(priv);
+
+	error = cst816x_parse_keycodes(dev, priv);
+	if (error)
+		dev_warn(dev, "no gestures found in dt\n");
+
+	error = cst816x_register_input(priv);
+	if (error)
+		return dev_err_probe(dev, error, "input register failed\n");
+
+	error = devm_request_threaded_irq(dev, client->irq,
+					  NULL, cst816x_irq_cb, IRQF_ONESHOT,
+					  dev_driver_string(dev), priv);
+	if (error)
+		return dev_err_probe(dev, error, "irq request failed\n");
+
+	return 0;
+}
+
+static const struct i2c_device_id cst816x_id[] = {
+	{ .name = "cst816s" },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, cst816x_id);
+
+static const struct of_device_id cst816x_of_match[] = {
+	{ .compatible = "hynitron,cst816s", },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, cst816x_of_match);
+
+static struct i2c_driver cst816x_driver = {
+	.driver = {
+		.name = "cst816x",
+		.of_match_table = cst816x_of_match,
+	},
+	.id_table = cst816x_id,
+	.probe = cst816x_probe,
+};
+
+module_i2c_driver(cst816x_driver);
+
+MODULE_AUTHOR("Oleh Kuzhylnyi <kuzhylol@gmail.com>");
+MODULE_DESCRIPTION("Hynitron CST816x Series Touchscreen Driver");
+MODULE_LICENSE("GPL");