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, 357 insertions, 0 deletions

diff --git a/drivers/power/reset/reboot-mode.c b/drivers/power/reset/reboot-mode.c
new file mode 100644
index 000000000..af00c00ec
--- /dev/null
+++ b/drivers/power/reset/reboot-mode.c
@@ -0,0 +1,357 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (c) 2016, Fuzhou Rockchip Electronics Co., Ltd
+ */
+
+#include <linux/device.h>
+#include <linux/err.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/list.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/property.h>
+#include <linux/reboot.h>
+#include <linux/reboot-mode.h>
+#include <linux/slab.h>
+#include <linux/string.h>
+
+#define PREFIX "mode-"
+
+struct mode_info {
+	const char *mode;
+	u32 magic;
+	struct list_head list;
+};
+
+struct reboot_mode_sysfs_data {
+	struct device *reboot_mode_device;
+	struct list_head head;
+};
+
+static inline void reboot_mode_release_list(struct reboot_mode_sysfs_data *priv)
+{
+	struct mode_info *info;
+	struct mode_info *next;
+
+	list_for_each_entry_safe(info, next, &priv->head, list) {
+		list_del(&info->list);
+		kfree_const(info->mode);
+		kfree(info);
+	}
+}
+
+static ssize_t reboot_modes_show(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	struct reboot_mode_sysfs_data *priv;
+	struct mode_info *sysfs_info;
+	ssize_t size = 0;
+
+	priv = dev_get_drvdata(dev);
+	if (!priv)
+		return -ENODATA;
+
+	list_for_each_entry(sysfs_info, &priv->head, list)
+		size += sysfs_emit_at(buf, size, "%s ", sysfs_info->mode);
+
+	if (!size)
+		return -ENODATA;
+
+	return size + sysfs_emit_at(buf, size - 1, "\n");
+}
+static DEVICE_ATTR_RO(reboot_modes);
+
+static struct attribute *reboot_mode_attrs[] = {
+	&dev_attr_reboot_modes.attr,
+	NULL,
+};
+ATTRIBUTE_GROUPS(reboot_mode);
+
+static const struct class reboot_mode_class = {
+	.name = "reboot-mode",
+	.dev_groups = reboot_mode_groups,
+};
+
+static unsigned int get_reboot_mode_magic(struct reboot_mode_driver *reboot,
+					  const char *cmd)
+{
+	const char *normal = "normal";
+	struct mode_info *info;
+	char cmd_[110];
+
+	if (!cmd)
+		cmd = normal;
+
+	list_for_each_entry(info, &reboot->head, list)
+		if (!strcmp(info->mode, cmd))
+			return info->magic;
+
+	/* try to match again, replacing characters impossible in DT */
+	if (strscpy(cmd_, cmd, sizeof(cmd_)) == -E2BIG)
+		return 0;
+
+	strreplace(cmd_, ' ', '-');
+	strreplace(cmd_, ',', '-');
+	strreplace(cmd_, '/', '-');
+
+	list_for_each_entry(info, &reboot->head, list)
+		if (!strcmp(info->mode, cmd_))
+			return info->magic;
+
+	return 0;
+}
+
+static int reboot_mode_notify(struct notifier_block *this,
+			      unsigned long mode, void *cmd)
+{
+	struct reboot_mode_driver *reboot;
+	unsigned int magic;
+
+	reboot = container_of(this, struct reboot_mode_driver, reboot_notifier);
+	magic = get_reboot_mode_magic(reboot, cmd);
+	if (magic)
+		reboot->write(reboot, magic);
+
+	return NOTIFY_DONE;
+}
+
+static int reboot_mode_create_device(struct reboot_mode_driver *reboot)
+{
+	struct reboot_mode_sysfs_data *priv;
+	struct mode_info *sysfs_info;
+	struct mode_info *info;
+	int ret;
+
+	priv = kzalloc_obj(*priv, GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	INIT_LIST_HEAD(&priv->head);
+
+	list_for_each_entry(info, &reboot->head, list) {
+		sysfs_info = kzalloc_obj(*sysfs_info, GFP_KERNEL);
+		if (!sysfs_info) {
+			ret = -ENOMEM;
+			goto error;
+		}
+
+		sysfs_info->mode = kstrdup_const(info->mode, GFP_KERNEL);
+		if (!sysfs_info->mode) {
+			kfree(sysfs_info);
+			ret = -ENOMEM;
+			goto error;
+		}
+
+		list_add_tail(&sysfs_info->list, &priv->head);
+	}
+
+	priv->reboot_mode_device = device_create(&reboot_mode_class, NULL, 0,
+						 (void *)priv, "%s",
+						 reboot->dev->driver->name);
+	if (IS_ERR(priv->reboot_mode_device)) {
+		ret = PTR_ERR(priv->reboot_mode_device);
+		goto error;
+	}
+
+	return 0;
+
+error:
+	reboot_mode_release_list(priv);
+	kfree(priv);
+	return ret;
+}
+
+/**
+ * reboot_mode_register - register a reboot mode driver
+ * @reboot: reboot mode driver
+ *
+ * Returns: 0 on success or a negative error code on failure.
+ */
+int reboot_mode_register(struct reboot_mode_driver *reboot)
+{
+	struct mode_info *info = NULL;
+	struct property *prop;
+	struct device_node *np = reboot->dev->of_node;
+	size_t len = strlen(PREFIX);
+	u32 magic;
+	int ret;
+
+	INIT_LIST_HEAD(&reboot->head);
+
+	for_each_property_of_node(np, prop) {
+		if (strncmp(prop->name, PREFIX, len))
+			continue;
+
+		if (device_property_read_u32(reboot->dev, prop->name, &magic)) {
+			dev_dbg(reboot->dev, "reboot mode %s without magic number\n",
+				prop->name);
+			continue;
+		}
+
+		info = kzalloc_obj(*info, GFP_KERNEL);
+		if (!info) {
+			ret = -ENOMEM;
+			goto error;
+		}
+
+		info->magic = magic;
+		info->mode = kstrdup_const(prop->name + len, GFP_KERNEL);
+		if (!info->mode) {
+			ret = -ENOMEM;
+			goto error;
+		} else if (info->mode[0] == '\0') {
+			kfree_const(info->mode);
+			ret = -EINVAL;
+			dev_err(reboot->dev, "invalid mode name(%s): too short!\n",
+				prop->name);
+			goto error;
+		}
+
+		list_add_tail(&info->list, &reboot->head);
+		info = NULL;
+	}
+
+	reboot->reboot_notifier.notifier_call = reboot_mode_notify;
+	register_reboot_notifier(&reboot->reboot_notifier);
+
+	ret = reboot_mode_create_device(reboot);
+	if (ret)
+		goto error;
+
+	return 0;
+
+error:
+	kfree(info);
+	reboot_mode_unregister(reboot);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(reboot_mode_register);
+
+static int reboot_mode_match_by_name(struct device *dev, const void *data)
+{
+	const char *name = data;
+
+	if (!dev || !data)
+		return 0;
+
+	return dev_name(dev) && strcmp(dev_name(dev), name) == 0;
+}
+
+static inline void reboot_mode_unregister_device(struct reboot_mode_driver *reboot)
+{
+	struct reboot_mode_sysfs_data *priv;
+	struct device *reboot_mode_device;
+
+	reboot_mode_device = class_find_device(&reboot_mode_class, NULL, reboot->dev->driver->name,
+					       reboot_mode_match_by_name);
+
+	if (!reboot_mode_device)
+		return;
+
+	priv = dev_get_drvdata(reboot_mode_device);
+	device_unregister(reboot_mode_device);
+
+	if (!priv)
+		return;
+
+	reboot_mode_release_list(priv);
+	kfree(priv);
+}
+
+/**
+ * reboot_mode_unregister - unregister a reboot mode driver
+ * @reboot: reboot mode driver
+ */
+int reboot_mode_unregister(struct reboot_mode_driver *reboot)
+{
+	struct mode_info *info;
+	struct mode_info *next;
+
+	unregister_reboot_notifier(&reboot->reboot_notifier);
+	reboot_mode_unregister_device(reboot);
+
+	list_for_each_entry_safe(info, next, &reboot->head, list) {
+		list_del(&info->list);
+		kfree_const(info->mode);
+		kfree(info);
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(reboot_mode_unregister);
+
+static void devm_reboot_mode_release(struct device *dev, void *res)
+{
+	reboot_mode_unregister(*(struct reboot_mode_driver **)res);
+}
+
+/**
+ * devm_reboot_mode_register() - resource managed reboot_mode_register()
+ * @dev: device to associate this resource with
+ * @reboot: reboot mode driver
+ *
+ * Returns: 0 on success or a negative error code on failure.
+ */
+int devm_reboot_mode_register(struct device *dev,
+			      struct reboot_mode_driver *reboot)
+{
+	struct reboot_mode_driver **dr;
+	int rc;
+
+	dr = devres_alloc(devm_reboot_mode_release, sizeof(*dr), GFP_KERNEL);
+	if (!dr)
+		return -ENOMEM;
+
+	rc = reboot_mode_register(reboot);
+	if (rc) {
+		devres_free(dr);
+		return rc;
+	}
+
+	*dr = reboot;
+	devres_add(dev, dr);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(devm_reboot_mode_register);
+
+static int devm_reboot_mode_match(struct device *dev, void *res, void *data)
+{
+	struct reboot_mode_driver **p = res;
+
+	if (WARN_ON(!p || !*p))
+		return 0;
+
+	return *p == data;
+}
+
+/**
+ * devm_reboot_mode_unregister() - resource managed reboot_mode_unregister()
+ * @dev: device to associate this resource with
+ * @reboot: reboot mode driver
+ */
+void devm_reboot_mode_unregister(struct device *dev,
+				 struct reboot_mode_driver *reboot)
+{
+	WARN_ON(devres_release(dev,
+			       devm_reboot_mode_release,
+			       devm_reboot_mode_match, reboot));
+}
+EXPORT_SYMBOL_GPL(devm_reboot_mode_unregister);
+
+static int __init reboot_mode_init(void)
+{
+	return class_register(&reboot_mode_class);
+}
+
+static void __exit reboot_mode_exit(void)
+{
+	class_unregister(&reboot_mode_class);
+}
+
+subsys_initcall(reboot_mode_init);
+module_exit(reboot_mode_exit);
+
+MODULE_AUTHOR("Andy Yan <andy.yan@rock-chips.com>");
+MODULE_DESCRIPTION("System reboot mode core library");
+MODULE_LICENSE("GPL v2");