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, 220 insertions, 0 deletions

diff --git a/drivers/gpio/gpio-latch.c b/drivers/gpio/gpio-latch.c
new file mode 100644
index 000000000..88757402e
--- /dev/null
+++ b/drivers/gpio/gpio-latch.c
@@ -0,0 +1,220 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * GPIO latch driver
+ *
+ *  Copyright (C) 2022 Sascha Hauer <s.hauer@pengutronix.de>
+ *
+ * This driver implements a GPIO (or better GPO as there is no input)
+ * multiplexer based on latches like this:
+ *
+ * CLK0 ----------------------.        ,--------.
+ * CLK1 -------------------.  `--------|>    #0 |
+ *                         |           |        |
+ * OUT0 ----------------+--|-----------|D0    Q0|-----|<
+ * OUT1 --------------+-|--|-----------|D1    Q1|-----|<
+ * OUT2 ------------+-|-|--|-----------|D2    Q2|-----|<
+ * OUT3 ----------+-|-|-|--|-----------|D3    Q3|-----|<
+ * OUT4 --------+-|-|-|-|--|-----------|D4    Q4|-----|<
+ * OUT5 ------+-|-|-|-|-|--|-----------|D5    Q5|-----|<
+ * OUT6 ----+-|-|-|-|-|-|--|-----------|D6    Q6|-----|<
+ * OUT7 --+-|-|-|-|-|-|-|--|-----------|D7    Q7|-----|<
+ *        | | | | | | | |  |           `--------'
+ *        | | | | | | | |  |
+ *        | | | | | | | |  |           ,--------.
+ *        | | | | | | | |  `-----------|>    #1 |
+ *        | | | | | | | |              |        |
+ *        | | | | | | | `--------------|D0    Q0|-----|<
+ *        | | | | | | `----------------|D1    Q1|-----|<
+ *        | | | | | `------------------|D2    Q2|-----|<
+ *        | | | | `--------------------|D3    Q3|-----|<
+ *        | | | `----------------------|D4    Q4|-----|<
+ *        | | `------------------------|D5    Q5|-----|<
+ *        | `--------------------------|D6    Q6|-----|<
+ *        `----------------------------|D7    Q7|-----|<
+ *                                     `--------'
+ *
+ * The above is just an example. The actual number of number of latches and
+ * the number of inputs per latch is derived from the number of GPIOs given
+ * in the corresponding device tree properties.
+ */
+
+#include <linux/cleanup.h>
+#include <linux/err.h>
+#include <linux/gpio/consumer.h>
+#include <linux/gpio/driver.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/property.h>
+#include <linux/delay.h>
+
+struct gpio_latch_priv {
+	struct gpio_chip gc;
+	struct gpio_descs *clk_gpios;
+	struct gpio_descs *latched_gpios;
+	int n_latched_gpios;
+	unsigned int setup_duration_ns;
+	unsigned int clock_duration_ns;
+	unsigned long *shadow;
+	/*
+	 * Depending on whether any of the underlying GPIOs may sleep we either
+	 * use a mutex or a spinlock to protect our shadow map.
+	 */
+	union {
+		struct mutex mutex; /* protects @shadow */
+		spinlock_t spinlock; /* protects @shadow */
+	};
+};
+
+static int gpio_latch_get_direction(struct gpio_chip *gc, unsigned int offset)
+{
+	return GPIO_LINE_DIRECTION_OUT;
+}
+
+static int gpio_latch_set_unlocked(struct gpio_latch_priv *priv,
+				   int (*set)(struct gpio_desc *desc, int value),
+				   unsigned int offset, bool val)
+{
+	int latch = offset / priv->n_latched_gpios, i, ret;
+
+	assign_bit(offset, priv->shadow, val);
+
+	for (i = 0; i < priv->n_latched_gpios; i++) {
+		ret = set(priv->latched_gpios->desc[i],
+			  test_bit(latch * priv->n_latched_gpios + i,
+				   priv->shadow));
+		if (ret)
+			return ret;
+	}
+
+	ndelay(priv->setup_duration_ns);
+	set(priv->clk_gpios->desc[latch], 1);
+	ndelay(priv->clock_duration_ns);
+	set(priv->clk_gpios->desc[latch], 0);
+
+	return 0;
+}
+
+static int gpio_latch_set(struct gpio_chip *gc, unsigned int offset, int val)
+{
+	struct gpio_latch_priv *priv = gpiochip_get_data(gc);
+
+	guard(spinlock_irqsave)(&priv->spinlock);
+
+	return gpio_latch_set_unlocked(priv, gpiod_set_value, offset, val);
+}
+
+static int gpio_latch_set_can_sleep(struct gpio_chip *gc, unsigned int offset, int val)
+{
+	struct gpio_latch_priv *priv = gpiochip_get_data(gc);
+
+	guard(mutex)(&priv->mutex);
+
+	return gpio_latch_set_unlocked(priv, gpiod_set_value_cansleep, offset, val);
+}
+
+static bool gpio_latch_can_sleep(struct gpio_latch_priv *priv, unsigned int n_latches)
+{
+	int i;
+
+	for (i = 0; i < n_latches; i++)
+		if (gpiod_cansleep(priv->clk_gpios->desc[i]))
+			return true;
+
+	for (i = 0; i < priv->n_latched_gpios; i++)
+		if (gpiod_cansleep(priv->latched_gpios->desc[i]))
+			return true;
+
+	return false;
+}
+
+/*
+ * Some value which is still acceptable to delay in atomic context.
+ * If we need to go higher we might have to switch to usleep_range(),
+ * but that cannot ne used in atomic context and the driver would have
+ * to be adjusted to support that.
+ */
+#define DURATION_NS_MAX 5000
+
+static int gpio_latch_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct gpio_latch_priv *priv;
+	unsigned int n_latches;
+
+	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	priv->clk_gpios = devm_gpiod_get_array(dev, "clk", GPIOD_OUT_LOW);
+	if (IS_ERR(priv->clk_gpios))
+		return PTR_ERR(priv->clk_gpios);
+
+	priv->latched_gpios = devm_gpiod_get_array(dev, "latched", GPIOD_OUT_LOW);
+	if (IS_ERR(priv->latched_gpios))
+		return PTR_ERR(priv->latched_gpios);
+
+	n_latches = priv->clk_gpios->ndescs;
+	priv->n_latched_gpios = priv->latched_gpios->ndescs;
+
+	priv->shadow = devm_bitmap_zalloc(dev, n_latches * priv->n_latched_gpios,
+					  GFP_KERNEL);
+	if (!priv->shadow)
+		return -ENOMEM;
+
+	if (gpio_latch_can_sleep(priv, n_latches)) {
+		priv->gc.can_sleep = true;
+		priv->gc.set = gpio_latch_set_can_sleep;
+		mutex_init(&priv->mutex);
+	} else {
+		priv->gc.can_sleep = false;
+		priv->gc.set = gpio_latch_set;
+		spin_lock_init(&priv->spinlock);
+	}
+
+	device_property_read_u32(dev, "setup-duration-ns",
+				 &priv->setup_duration_ns);
+	if (priv->setup_duration_ns > DURATION_NS_MAX) {
+		dev_warn(dev, "setup-duration-ns too high, limit to %d\n",
+			 DURATION_NS_MAX);
+		priv->setup_duration_ns = DURATION_NS_MAX;
+	}
+
+	device_property_read_u32(dev, "clock-duration-ns",
+				 &priv->clock_duration_ns);
+	if (priv->clock_duration_ns > DURATION_NS_MAX) {
+		dev_warn(dev, "clock-duration-ns too high, limit to %d\n",
+			 DURATION_NS_MAX);
+		priv->clock_duration_ns = DURATION_NS_MAX;
+	}
+
+	priv->gc.get_direction = gpio_latch_get_direction;
+	priv->gc.ngpio = n_latches * priv->n_latched_gpios;
+	priv->gc.owner = THIS_MODULE;
+	priv->gc.base = -1;
+	priv->gc.parent = dev;
+
+	platform_set_drvdata(pdev, priv);
+
+	return devm_gpiochip_add_data(dev, &priv->gc, priv);
+}
+
+static const struct of_device_id gpio_latch_ids[] = {
+	{
+		.compatible = "gpio-latch",
+	},
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, gpio_latch_ids);
+
+static struct platform_driver gpio_latch_driver = {
+	.driver	= {
+		.name		= "gpio-latch",
+		.of_match_table	= gpio_latch_ids,
+	},
+	.probe	= gpio_latch_probe,
+};
+module_platform_driver(gpio_latch_driver);
+
+MODULE_LICENSE("GPL v2");
+MODULE_AUTHOR("Sascha Hauer <s.hauer@pengutronix.de>");
+MODULE_DESCRIPTION("GPIO latch driver");