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, 142 insertions, 0 deletions

diff --git a/drivers/dio/dio-driver.c b/drivers/dio/dio-driver.c
new file mode 100644
index 000000000..12fa2d209
--- /dev/null
+++ b/drivers/dio/dio-driver.c
@@ -0,0 +1,142 @@
+/*
+ *  DIO Driver Services
+ *
+ *  Copyright (C) 2004 Jochen Friedrich
+ *
+ *  Loosely based on drivers/pci/pci-driver.c and drivers/zorro/zorro-driver.c
+ *
+ *  This file is subject to the terms and conditions of the GNU General Public
+ *  License.  See the file COPYING in the main directory of this archive
+ *  for more details.
+ */
+
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/dio.h>
+
+
+/**
+ *  dio_match_device - Tell if a DIO device structure has a matching DIO device id structure
+ *  @ids: array of DIO device id structures to search in
+ *  @d: the DIO device structure to match against
+ *
+ *  Used by a driver to check whether a DIO device present in the
+ *  system is in its list of supported devices. Returns the matching
+ *  dio_device_id structure or %NULL if there is no match.
+ */
+
+static const struct dio_device_id *
+dio_match_device(const struct dio_device_id *ids,
+		   const struct dio_dev *d)
+{
+	while (ids->id) {
+		if (ids->id == DIO_WILDCARD)
+			return ids;
+		if (DIO_NEEDSSECID(ids->id & 0xff)) {
+			if (ids->id == d->id)
+				return ids;
+		} else {
+			if ((ids->id & 0xff) == (d->id & 0xff))
+				return ids;
+		}
+		ids++;
+	}
+	return NULL;
+}
+
+static int dio_device_probe(struct device *dev)
+{
+	int error = 0;
+	struct dio_driver *drv = to_dio_driver(dev->driver);
+	struct dio_dev *d = to_dio_dev(dev);
+
+	if (!d->driver && drv->probe) {
+		const struct dio_device_id *id;
+
+		id = dio_match_device(drv->id_table, d);
+		if (id)
+			error = drv->probe(d, id);
+		if (error >= 0) {
+			d->driver = drv;
+			error = 0;
+		}
+	}
+	return error;
+}
+
+
+/**
+ *  dio_register_driver - register a new DIO driver
+ *  @drv: the driver structure to register
+ *
+ *  Adds the driver structure to the list of registered drivers
+ *  Returns zero or a negative error value.
+ */
+
+int dio_register_driver(struct dio_driver *drv)
+{
+	/* initialize common driver fields */
+	drv->driver.name = drv->name;
+	drv->driver.bus = &dio_bus_type;
+
+	/* register with core */
+	return driver_register(&drv->driver);
+}
+
+
+/**
+ *  dio_unregister_driver - unregister a DIO driver
+ *  @drv: the driver structure to unregister
+ *
+ *  Deletes the driver structure from the list of registered DIO drivers,
+ *  gives it a chance to clean up by calling its remove() function for
+ *  each device it was responsible for, and marks those devices as
+ *  driverless.
+ */
+
+void dio_unregister_driver(struct dio_driver *drv)
+{
+	driver_unregister(&drv->driver);
+}
+
+
+/**
+ *  dio_bus_match - Tell if a DIO device structure has a matching DIO device id structure
+ *  @dev: the DIO device structure to match against
+ *  @drv: the &device_driver that points to the array of DIO device id structures to search
+ *
+ *  Used by the driver core to check whether a DIO device present in the
+ *  system is in a driver's list of supported devices. Returns 1 if supported,
+ *  and 0 if there is no match.
+ */
+
+static int dio_bus_match(struct device *dev, const struct device_driver *drv)
+{
+	struct dio_dev *d = to_dio_dev(dev);
+	const struct dio_driver *dio_drv = to_dio_driver(drv);
+	const struct dio_device_id *ids = dio_drv->id_table;
+
+	if (!ids)
+		return 0;
+
+	return dio_match_device(ids, d) ? 1 : 0;
+}
+
+
+const struct bus_type dio_bus_type = {
+	.name	= "dio",
+	.match	= dio_bus_match,
+	.probe	= dio_device_probe,
+};
+
+
+static int __init dio_driver_init(void)
+{
+	return bus_register(&dio_bus_type);
+}
+
+postcore_initcall(dio_driver_init);
+
+EXPORT_SYMBOL(dio_register_driver);
+EXPORT_SYMBOL(dio_unregister_driver);
+EXPORT_SYMBOL(dio_bus_type);