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, 156 insertions, 0 deletions

diff --git a/drivers/input/keyboard/dlink-dir685-touchkeys.c b/drivers/input/keyboard/dlink-dir685-touchkeys.c
new file mode 100644
index 000000000..bf94367f6
--- /dev/null
+++ b/drivers/input/keyboard/dlink-dir685-touchkeys.c
@@ -0,0 +1,156 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * D-Link DIR-685 router I2C-based Touchkeys input driver
+ * Copyright (C) 2017 Linus Walleij <linus.walleij@linaro.org>
+ *
+ * This is a one-off touchkey controller based on the Cypress Semiconductor
+ * CY8C214 MCU with some firmware in its internal 8KB flash. The circuit
+ * board inside the router is named E119921
+ */
+
+#include <linux/module.h>
+#include <linux/i2c.h>
+#include <linux/interrupt.h>
+#include <linux/delay.h>
+#include <linux/input.h>
+#include <linux/slab.h>
+#include <linux/string_choices.h>
+#include <linux/bitops.h>
+
+struct dir685_touchkeys {
+	struct device		*dev;
+	struct i2c_client	*client;
+	struct input_dev	*input;
+	unsigned long		cur_key;
+	u16			codes[7];
+};
+
+static irqreturn_t dir685_tk_irq_thread(int irq, void *data)
+{
+	struct dir685_touchkeys *tk = data;
+	const int num_bits = min_t(int, ARRAY_SIZE(tk->codes), 16);
+	unsigned long changed;
+	u8 buf[6];
+	unsigned long key;
+	int i;
+	int err;
+
+	memset(buf, 0, sizeof(buf));
+	err = i2c_master_recv(tk->client, buf, sizeof(buf));
+	if (err != sizeof(buf)) {
+		dev_err(tk->dev, "short read %d\n", err);
+		return IRQ_HANDLED;
+	}
+
+	dev_dbg(tk->dev, "IN: %*ph\n", (int)sizeof(buf), buf);
+	key = be16_to_cpup((__be16 *) &buf[4]);
+
+	/* Figure out if any bits went high or low since last message */
+	changed = tk->cur_key ^ key;
+	for_each_set_bit(i, &changed, num_bits) {
+		dev_dbg(tk->dev, "key %d is %s\n", i,
+			str_down_up(test_bit(i, &key)));
+		input_report_key(tk->input, tk->codes[i], test_bit(i, &key));
+	}
+
+	/* Store currently down keys */
+	tk->cur_key = key;
+	input_sync(tk->input);
+
+	return IRQ_HANDLED;
+}
+
+static int dir685_tk_probe(struct i2c_client *client)
+{
+	static const u8 bl_data[] = { 0xa7, 0x40 };
+	struct device *dev = &client->dev;
+	struct dir685_touchkeys *tk;
+	int err;
+	int i;
+
+	tk = devm_kzalloc(&client->dev, sizeof(*tk), GFP_KERNEL);
+	if (!tk)
+		return -ENOMEM;
+
+	tk->input = devm_input_allocate_device(dev);
+	if (!tk->input)
+		return -ENOMEM;
+
+	tk->client = client;
+	tk->dev = dev;
+
+	tk->input->keycodesize = sizeof(u16);
+	tk->input->keycodemax = ARRAY_SIZE(tk->codes);
+	tk->input->keycode = tk->codes;
+	tk->codes[0] = KEY_UP;
+	tk->codes[1] = KEY_DOWN;
+	tk->codes[2] = KEY_LEFT;
+	tk->codes[3] = KEY_RIGHT;
+	tk->codes[4] = KEY_ENTER;
+	tk->codes[5] = KEY_WPS_BUTTON;
+	/*
+	 * This key appears in the vendor driver, but I have
+	 * not been able to activate it.
+	 */
+	tk->codes[6] = KEY_RESERVED;
+
+	__set_bit(EV_KEY, tk->input->evbit);
+	for (i = 0; i < ARRAY_SIZE(tk->codes); i++)
+		__set_bit(tk->codes[i], tk->input->keybit);
+	__clear_bit(KEY_RESERVED, tk->input->keybit);
+
+	tk->input->name = "D-Link DIR-685 touchkeys";
+	tk->input->id.bustype = BUS_I2C;
+
+	err = input_register_device(tk->input);
+	if (err)
+		return err;
+
+	/* Set the brightness to max level */
+	err = i2c_master_send(client, bl_data, sizeof(bl_data));
+	if (err != sizeof(bl_data))
+		dev_warn(tk->dev, "error setting brightness level\n");
+
+	if (!client->irq) {
+		dev_err(dev, "no IRQ on the I2C device\n");
+		return -ENODEV;
+	}
+	err = devm_request_threaded_irq(dev, client->irq,
+					NULL, dir685_tk_irq_thread,
+					IRQF_ONESHOT,
+					"dir685-tk", tk);
+	if (err) {
+		dev_err(dev, "can't request IRQ\n");
+		return err;
+	}
+
+	return 0;
+}
+
+static const struct i2c_device_id dir685_tk_id[] = {
+	{ .name = "dir685tk" },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, dir685_tk_id);
+
+#ifdef CONFIG_OF
+static const struct of_device_id dir685_tk_of_match[] = {
+	{ .compatible = "dlink,dir685-touchkeys" },
+	{},
+};
+MODULE_DEVICE_TABLE(of, dir685_tk_of_match);
+#endif
+
+static struct i2c_driver dir685_tk_i2c_driver = {
+	.driver = {
+		.name	= "dlink-dir685-touchkeys",
+		.of_match_table = of_match_ptr(dir685_tk_of_match),
+	},
+	.probe		= dir685_tk_probe,
+	.id_table	= dir685_tk_id,
+};
+module_i2c_driver(dir685_tk_i2c_driver);
+
+MODULE_AUTHOR("Linus Walleij <linus.walleij@linaro.org>");
+MODULE_DESCRIPTION("D-Link DIR-685 touchkeys driver");
+MODULE_LICENSE("GPL");