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, 265 insertions, 0 deletions

diff --git a/drivers/counter/interrupt-cnt.c b/drivers/counter/interrupt-cnt.c
new file mode 100644
index 000000000..694292051
--- /dev/null
+++ b/drivers/counter/interrupt-cnt.c
@@ -0,0 +1,265 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2021 Pengutronix, Oleksij Rempel <kernel@pengutronix.de>
+ */
+
+#include <linux/cleanup.h>
+#include <linux/counter.h>
+#include <linux/gpio/consumer.h>
+#include <linux/interrupt.h>
+#include <linux/irq.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/platform_device.h>
+#include <linux/types.h>
+
+#define INTERRUPT_CNT_NAME "interrupt-cnt"
+
+struct interrupt_cnt_priv {
+	atomic_long_t count;
+	struct gpio_desc *gpio;
+	int irq;
+	bool enabled;
+	struct mutex lock;
+	struct counter_signal signals;
+	struct counter_synapse synapses;
+	struct counter_count cnts;
+};
+
+static irqreturn_t interrupt_cnt_isr(int irq, void *dev_id)
+{
+	struct counter_device *counter = dev_id;
+	struct interrupt_cnt_priv *priv = counter_priv(counter);
+
+	atomic_long_inc(&priv->count);
+
+	counter_push_event(counter, COUNTER_EVENT_CHANGE_OF_STATE, 0);
+
+	return IRQ_HANDLED;
+}
+
+static int interrupt_cnt_enable_read(struct counter_device *counter,
+				     struct counter_count *count, u8 *enable)
+{
+	struct interrupt_cnt_priv *priv = counter_priv(counter);
+
+	guard(mutex)(&priv->lock);
+
+	*enable = priv->enabled;
+
+	return 0;
+}
+
+static int interrupt_cnt_enable_write(struct counter_device *counter,
+				      struct counter_count *count, u8 enable)
+{
+	struct interrupt_cnt_priv *priv = counter_priv(counter);
+
+	guard(mutex)(&priv->lock);
+
+	if (priv->enabled == enable)
+		return 0;
+
+	if (enable) {
+		priv->enabled = true;
+		enable_irq(priv->irq);
+	} else {
+		disable_irq(priv->irq);
+		priv->enabled = false;
+	}
+
+	return 0;
+}
+
+static struct counter_comp interrupt_cnt_ext[] = {
+	COUNTER_COMP_ENABLE(interrupt_cnt_enable_read,
+			    interrupt_cnt_enable_write),
+};
+
+static const enum counter_synapse_action interrupt_cnt_synapse_actions[] = {
+	COUNTER_SYNAPSE_ACTION_RISING_EDGE,
+};
+
+static int interrupt_cnt_action_read(struct counter_device *counter,
+				     struct counter_count *count,
+				     struct counter_synapse *synapse,
+				     enum counter_synapse_action *action)
+{
+	*action = COUNTER_SYNAPSE_ACTION_RISING_EDGE;
+
+	return 0;
+}
+
+static int interrupt_cnt_read(struct counter_device *counter,
+			      struct counter_count *count, u64 *val)
+{
+	struct interrupt_cnt_priv *priv = counter_priv(counter);
+
+	*val = atomic_long_read(&priv->count);
+
+	return 0;
+}
+
+static int interrupt_cnt_write(struct counter_device *counter,
+			       struct counter_count *count, const u64 val)
+{
+	struct interrupt_cnt_priv *priv = counter_priv(counter);
+
+	if (val != (typeof(priv->count.counter))val)
+		return -ERANGE;
+
+	atomic_long_set(&priv->count, val);
+
+	return 0;
+}
+
+static const enum counter_function interrupt_cnt_functions[] = {
+	COUNTER_FUNCTION_INCREASE,
+};
+
+static int interrupt_cnt_function_read(struct counter_device *counter,
+				       struct counter_count *count,
+				       enum counter_function *function)
+{
+	*function = COUNTER_FUNCTION_INCREASE;
+
+	return 0;
+}
+
+static int interrupt_cnt_signal_read(struct counter_device *counter,
+				     struct counter_signal *signal,
+				     enum counter_signal_level *level)
+{
+	struct interrupt_cnt_priv *priv = counter_priv(counter);
+	int ret;
+
+	if (!priv->gpio)
+		return -EINVAL;
+
+	ret = gpiod_get_value(priv->gpio);
+	if (ret < 0)
+		return ret;
+
+	*level = ret ? COUNTER_SIGNAL_LEVEL_HIGH : COUNTER_SIGNAL_LEVEL_LOW;
+
+	return 0;
+}
+
+static int interrupt_cnt_watch_validate(struct counter_device *counter,
+					const struct counter_watch *watch)
+{
+	if (watch->channel != 0 ||
+	    watch->event != COUNTER_EVENT_CHANGE_OF_STATE)
+		return -EINVAL;
+
+	return 0;
+}
+
+static const struct counter_ops interrupt_cnt_ops = {
+	.action_read = interrupt_cnt_action_read,
+	.count_read = interrupt_cnt_read,
+	.count_write = interrupt_cnt_write,
+	.function_read = interrupt_cnt_function_read,
+	.signal_read  = interrupt_cnt_signal_read,
+	.watch_validate  = interrupt_cnt_watch_validate,
+};
+
+static int interrupt_cnt_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct counter_device *counter;
+	struct interrupt_cnt_priv *priv;
+	int ret;
+
+	counter = devm_counter_alloc(dev, sizeof(*priv));
+	if (!counter)
+		return -ENOMEM;
+	priv = counter_priv(counter);
+
+	priv->irq = platform_get_irq_optional(pdev,  0);
+	if (priv->irq == -ENXIO)
+		priv->irq = 0;
+	else if (priv->irq < 0)
+		return dev_err_probe(dev, priv->irq, "failed to get IRQ\n");
+
+	priv->gpio = devm_gpiod_get_optional(dev, NULL, GPIOD_IN);
+	if (IS_ERR(priv->gpio))
+		return dev_err_probe(dev, PTR_ERR(priv->gpio), "failed to get GPIO\n");
+
+	if (!priv->irq && !priv->gpio) {
+		dev_err(dev, "IRQ and GPIO are not found. At least one source should be provided\n");
+		return -ENODEV;
+	}
+
+	if (!priv->irq) {
+		int irq = gpiod_to_irq(priv->gpio);
+
+		if (irq < 0)
+			return dev_err_probe(dev, irq, "failed to get IRQ from GPIO\n");
+
+		priv->irq = irq;
+	}
+
+	priv->signals.name = devm_kasprintf(dev, GFP_KERNEL, "IRQ %d",
+					    priv->irq);
+	if (!priv->signals.name)
+		return -ENOMEM;
+
+	counter->signals = &priv->signals;
+	counter->num_signals = 1;
+
+	priv->synapses.actions_list = interrupt_cnt_synapse_actions;
+	priv->synapses.num_actions = ARRAY_SIZE(interrupt_cnt_synapse_actions);
+	priv->synapses.signal = &priv->signals;
+
+	priv->cnts.name = "Channel 0 Count";
+	priv->cnts.functions_list = interrupt_cnt_functions;
+	priv->cnts.num_functions = ARRAY_SIZE(interrupt_cnt_functions);
+	priv->cnts.synapses = &priv->synapses;
+	priv->cnts.num_synapses = 1;
+	priv->cnts.ext = interrupt_cnt_ext;
+	priv->cnts.num_ext = ARRAY_SIZE(interrupt_cnt_ext);
+
+	counter->name = dev_name(dev);
+	counter->parent = dev;
+	counter->ops = &interrupt_cnt_ops;
+	counter->counts = &priv->cnts;
+	counter->num_counts = 1;
+
+	irq_set_status_flags(priv->irq, IRQ_NOAUTOEN);
+	ret = devm_request_irq(dev, priv->irq, interrupt_cnt_isr,
+			       IRQF_TRIGGER_RISING, dev_name(dev), counter);
+	if (ret)
+		return ret;
+
+	ret = devm_mutex_init(dev, &priv->lock);
+	if (ret)
+		return ret;
+
+	ret = devm_counter_add(dev, counter);
+	if (ret < 0)
+		return dev_err_probe(dev, ret, "Failed to add counter\n");
+
+	return 0;
+}
+
+static const struct of_device_id interrupt_cnt_of_match[] = {
+	{ .compatible = "interrupt-counter", },
+	{}
+};
+MODULE_DEVICE_TABLE(of, interrupt_cnt_of_match);
+
+static struct platform_driver interrupt_cnt_driver = {
+	.probe = interrupt_cnt_probe,
+	.driver = {
+		.name = INTERRUPT_CNT_NAME,
+		.of_match_table = interrupt_cnt_of_match,
+	},
+};
+module_platform_driver(interrupt_cnt_driver);
+
+MODULE_ALIAS("platform:interrupt-counter");
+MODULE_AUTHOR("Oleksij Rempel <o.rempel@pengutronix.de>");
+MODULE_DESCRIPTION("Interrupt counter driver");
+MODULE_LICENSE("GPL v2");
+MODULE_IMPORT_NS("COUNTER");