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, 152 insertions, 0 deletions

diff --git a/drivers/iio/trigger/stm32-lptimer-trigger.c b/drivers/iio/trigger/stm32-lptimer-trigger.c
new file mode 100644
index 000000000..828890fe3
--- /dev/null
+++ b/drivers/iio/trigger/stm32-lptimer-trigger.c
@@ -0,0 +1,152 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * STM32 Low-Power Timer Trigger driver
+ *
+ * Copyright (C) STMicroelectronics 2017
+ *
+ * Author: Fabrice Gasnier <fabrice.gasnier@st.com>.
+ *
+ * Inspired by Benjamin Gaignard's stm32-timer-trigger driver
+ */
+
+#include <linux/export.h>
+#include <linux/iio/timer/stm32-lptim-trigger.h>
+#include <linux/mfd/stm32-lptimer.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/property.h>
+
+/* Maximum triggers + one trailing null entry to indicate the end of array */
+#define MAX_TRIGGERS 3
+
+struct stm32_lptim_cfg {
+	const char * const (*triggers)[MAX_TRIGGERS];
+	unsigned int nb_triggers;
+};
+
+/* List Low-Power Timer triggers for H7, MP13, MP15 */
+static const char * const stm32_lptim_triggers[][MAX_TRIGGERS] = {
+	{ LPTIM1_OUT,},
+	{ LPTIM2_OUT,},
+	{ LPTIM3_OUT,},
+};
+
+/* List Low-Power Timer triggers for STM32MP25 */
+static const char * const stm32mp25_lptim_triggers[][MAX_TRIGGERS] = {
+	{ LPTIM1_CH1, LPTIM1_CH2, },
+	{ LPTIM2_CH1, LPTIM2_CH2, },
+	{ LPTIM3_CH1,},
+	{ LPTIM4_CH1,},
+	{ LPTIM5_OUT,},
+};
+
+static const struct stm32_lptim_cfg stm32mp15_lptim_cfg = {
+	.triggers = stm32_lptim_triggers,
+	.nb_triggers = ARRAY_SIZE(stm32_lptim_triggers),
+};
+
+static const struct stm32_lptim_cfg stm32mp25_lptim_cfg = {
+	.triggers = stm32mp25_lptim_triggers,
+	.nb_triggers = ARRAY_SIZE(stm32mp25_lptim_triggers),
+};
+
+struct stm32_lptim_trigger {
+	struct device *dev;
+	const char * const *triggers;
+};
+
+static int stm32_lptim_validate_device(struct iio_trigger *trig,
+				       struct iio_dev *indio_dev)
+{
+	if (indio_dev->modes & INDIO_HARDWARE_TRIGGERED)
+		return 0;
+
+	return -EINVAL;
+}
+
+static const struct iio_trigger_ops stm32_lptim_trigger_ops = {
+	.validate_device = stm32_lptim_validate_device,
+};
+
+/**
+ * is_stm32_lptim_trigger
+ * @trig: trigger to be checked
+ *
+ * return true if the trigger is a valid STM32 IIO Low-Power Timer Trigger
+ * either return false
+ */
+bool is_stm32_lptim_trigger(struct iio_trigger *trig)
+{
+	return (trig->ops == &stm32_lptim_trigger_ops);
+}
+EXPORT_SYMBOL(is_stm32_lptim_trigger);
+
+static int stm32_lptim_setup_trig(struct stm32_lptim_trigger *priv)
+{
+	const char * const *cur = priv->triggers;
+	int ret;
+
+	while (cur && *cur) {
+		struct iio_trigger *trig;
+
+		trig = devm_iio_trigger_alloc(priv->dev, "%s", *cur);
+		if  (!trig)
+			return -ENOMEM;
+
+		trig->dev.parent = priv->dev->parent;
+		trig->ops = &stm32_lptim_trigger_ops;
+		iio_trigger_set_drvdata(trig, priv);
+
+		ret = devm_iio_trigger_register(priv->dev, trig);
+		if (ret)
+			return ret;
+		cur++;
+	}
+
+	return 0;
+}
+
+static int stm32_lptim_trigger_probe(struct platform_device *pdev)
+{
+	struct stm32_lptim_trigger *priv;
+	struct stm32_lptim_cfg const *lptim_cfg;
+	u32 index;
+
+	priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	if (device_property_read_u32(&pdev->dev, "reg", &index))
+		return -EINVAL;
+
+	lptim_cfg = device_get_match_data(&pdev->dev);
+
+	if (index >= lptim_cfg->nb_triggers)
+		return -EINVAL;
+
+	priv->dev = &pdev->dev;
+	priv->triggers = lptim_cfg->triggers[index];
+
+	return stm32_lptim_setup_trig(priv);
+}
+
+static const struct of_device_id stm32_lptim_trig_of_match[] = {
+	{ .compatible = "st,stm32-lptimer-trigger", .data = &stm32mp15_lptim_cfg },
+	{ .compatible = "st,stm32mp25-lptimer-trigger", .data = &stm32mp25_lptim_cfg},
+	{ }
+};
+MODULE_DEVICE_TABLE(of, stm32_lptim_trig_of_match);
+
+static struct platform_driver stm32_lptim_trigger_driver = {
+	.probe = stm32_lptim_trigger_probe,
+	.driver = {
+		.name = "stm32-lptimer-trigger",
+		.of_match_table = stm32_lptim_trig_of_match,
+	},
+};
+module_platform_driver(stm32_lptim_trigger_driver);
+
+MODULE_AUTHOR("Fabrice Gasnier <fabrice.gasnier@st.com>");
+MODULE_ALIAS("platform:stm32-lptimer-trigger");
+MODULE_DESCRIPTION("STMicroelectronics STM32 LPTIM trigger driver");
+MODULE_LICENSE("GPL v2");