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, 97 insertions, 0 deletions

diff --git a/drivers/dma/idxd/bus.c b/drivers/dma/idxd/bus.c
new file mode 100644
index 000000000..e647a6844
--- /dev/null
+++ b/drivers/dma/idxd/bus.c
@@ -0,0 +1,97 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright(c) 2021 Intel Corporation. All rights rsvd. */
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/device.h>
+#include "idxd.h"
+
+
+int __idxd_driver_register(struct idxd_device_driver *idxd_drv, struct module *owner,
+			   const char *mod_name)
+{
+	struct device_driver *drv = &idxd_drv->drv;
+
+	if (!idxd_drv->type) {
+		pr_debug("driver type not set (%ps)\n", __builtin_return_address(0));
+		return -EINVAL;
+	}
+
+	drv->name = idxd_drv->name;
+	drv->bus = &dsa_bus_type;
+	drv->owner = owner;
+	drv->mod_name = mod_name;
+
+	return driver_register(drv);
+}
+EXPORT_SYMBOL_GPL(__idxd_driver_register);
+
+void idxd_driver_unregister(struct idxd_device_driver *idxd_drv)
+{
+	driver_unregister(&idxd_drv->drv);
+}
+EXPORT_SYMBOL_GPL(idxd_driver_unregister);
+
+static int idxd_config_bus_match(struct device *dev,
+				 const struct device_driver *drv)
+{
+	const struct idxd_device_driver *idxd_drv =
+		container_of_const(drv, struct idxd_device_driver, drv);
+	struct idxd_dev *idxd_dev = confdev_to_idxd_dev(dev);
+	int i = 0;
+
+	while (idxd_drv->type[i] != IDXD_DEV_NONE) {
+		if (idxd_dev->type == idxd_drv->type[i])
+			return 1;
+		i++;
+	}
+
+	return 0;
+}
+
+static int idxd_config_bus_probe(struct device *dev)
+{
+	struct idxd_device_driver *idxd_drv =
+		container_of(dev->driver, struct idxd_device_driver, drv);
+	struct idxd_dev *idxd_dev = confdev_to_idxd_dev(dev);
+
+	return idxd_drv->probe(idxd_dev);
+}
+
+static void idxd_config_bus_remove(struct device *dev)
+{
+	struct idxd_device_driver *idxd_drv =
+		container_of(dev->driver, struct idxd_device_driver, drv);
+	struct idxd_dev *idxd_dev = confdev_to_idxd_dev(dev);
+
+	idxd_drv->remove(idxd_dev);
+}
+
+static int idxd_bus_uevent(const struct device *dev, struct kobj_uevent_env *env)
+{
+	return add_uevent_var(env, "MODALIAS=" IDXD_DEVICES_MODALIAS_FMT, 0);
+}
+
+const struct bus_type dsa_bus_type = {
+	.name = "dsa",
+	.match = idxd_config_bus_match,
+	.probe = idxd_config_bus_probe,
+	.remove = idxd_config_bus_remove,
+	.uevent = idxd_bus_uevent,
+};
+EXPORT_SYMBOL_GPL(dsa_bus_type);
+
+static int __init dsa_bus_init(void)
+{
+	return bus_register(&dsa_bus_type);
+}
+module_init(dsa_bus_init);
+
+static void __exit dsa_bus_exit(void)
+{
+	bus_unregister(&dsa_bus_type);
+}
+module_exit(dsa_bus_exit);
+
+MODULE_DESCRIPTION("IDXD driver dsa_bus_type driver");
+MODULE_LICENSE("GPL v2");