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, 393 insertions, 0 deletions

diff --git a/drivers/pci/slot.c b/drivers/pci/slot.c
new file mode 100644
index 000000000..897223f01
--- /dev/null
+++ b/drivers/pci/slot.c
@@ -0,0 +1,393 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2006 Matthew Wilcox <matthew@wil.cx>
+ * Copyright (C) 2006-2009 Hewlett-Packard Development Company, L.P.
+ *	Alex Chiang <achiang@hp.com>
+ */
+
+#include <linux/kobject.h>
+#include <linux/slab.h>
+#include <linux/pci.h>
+#include <linux/err.h>
+#include "pci.h"
+
+struct kset *pci_slots_kset;
+EXPORT_SYMBOL_GPL(pci_slots_kset);
+
+static ssize_t pci_slot_attr_show(struct kobject *kobj,
+					struct attribute *attr, char *buf)
+{
+	struct pci_slot *slot = to_pci_slot(kobj);
+	struct pci_slot_attribute *attribute = to_pci_slot_attr(attr);
+	return attribute->show ? attribute->show(slot, buf) : -EIO;
+}
+
+static ssize_t pci_slot_attr_store(struct kobject *kobj,
+			struct attribute *attr, const char *buf, size_t len)
+{
+	struct pci_slot *slot = to_pci_slot(kobj);
+	struct pci_slot_attribute *attribute = to_pci_slot_attr(attr);
+	return attribute->store ? attribute->store(slot, buf, len) : -EIO;
+}
+
+static const struct sysfs_ops pci_slot_sysfs_ops = {
+	.show = pci_slot_attr_show,
+	.store = pci_slot_attr_store,
+};
+
+static ssize_t address_read_file(struct pci_slot *slot, char *buf)
+{
+	if (slot->number == PCI_SLOT_PLACEHOLDER)
+		return sysfs_emit(buf, "%04x:%02x\n",
+				  pci_domain_nr(slot->bus),
+				  slot->bus->number);
+
+	/*
+	 * Preserve legacy ABI expectations that hotplug drivers that manage
+	 * multiple devices per slot emit 0 for the device number.
+	 */
+	if (slot->number == PCI_SLOT_ALL_DEVICES)
+		return sysfs_emit(buf, "%04x:%02x:00\n",
+				  pci_domain_nr(slot->bus),
+				  slot->bus->number);
+
+	return sysfs_emit(buf, "%04x:%02x:%02x\n",
+			  pci_domain_nr(slot->bus),
+			  slot->bus->number,
+			  slot->number);
+}
+
+static ssize_t bus_speed_read(enum pci_bus_speed speed, char *buf)
+{
+	return sysfs_emit(buf, "%s\n", pci_speed_string(speed));
+}
+
+static ssize_t max_speed_read_file(struct pci_slot *slot, char *buf)
+{
+	return bus_speed_read(slot->bus->max_bus_speed, buf);
+}
+
+static ssize_t cur_speed_read_file(struct pci_slot *slot, char *buf)
+{
+	return bus_speed_read(slot->bus->cur_bus_speed, buf);
+}
+
+static bool pci_dev_matches_slot(struct pci_dev *dev, struct pci_slot *slot)
+{
+	if (slot->per_func_slot)
+		return dev->devfn == slot->number;
+
+	return slot->number == PCI_SLOT_ALL_DEVICES ||
+		PCI_SLOT(dev->devfn) == slot->number;
+}
+
+static bool pci_slot_enabled_per_func(void)
+{
+	if (IS_ENABLED(CONFIG_S390))
+		return true;
+
+	return false;
+}
+
+static void pci_slot_release(struct kobject *kobj)
+{
+	struct pci_dev *dev;
+	struct pci_slot *slot = to_pci_slot(kobj);
+
+	dev_dbg(&slot->bus->dev, "dev %02x, released physical slot %s\n",
+		slot->number, pci_slot_name(slot));
+
+	down_read(&pci_bus_sem);
+	list_for_each_entry(dev, &slot->bus->devices, bus_list)
+		if (pci_dev_matches_slot(dev, slot))
+			dev->slot = NULL;
+	up_read(&pci_bus_sem);
+
+	list_del(&slot->list);
+	pci_bus_put(slot->bus);
+
+	kfree(slot);
+}
+
+static struct pci_slot_attribute pci_slot_attr_address =
+	__ATTR(address, S_IRUGO, address_read_file, NULL);
+static struct pci_slot_attribute pci_slot_attr_max_speed =
+	__ATTR(max_bus_speed, S_IRUGO, max_speed_read_file, NULL);
+static struct pci_slot_attribute pci_slot_attr_cur_speed =
+	__ATTR(cur_bus_speed, S_IRUGO, cur_speed_read_file, NULL);
+
+static struct attribute *pci_slot_default_attrs[] = {
+	&pci_slot_attr_address.attr,
+	&pci_slot_attr_max_speed.attr,
+	&pci_slot_attr_cur_speed.attr,
+	NULL,
+};
+
+static const struct attribute_group pci_slot_default_group = {
+	.attrs = pci_slot_default_attrs,
+};
+
+static const struct attribute_group *pci_slot_default_groups[] = {
+	&pci_slot_default_group,
+#ifdef ARCH_PCI_SLOT_GROUPS
+	ARCH_PCI_SLOT_GROUPS,
+#endif
+	NULL,
+};
+
+static const struct kobj_type pci_slot_ktype = {
+	.sysfs_ops = &pci_slot_sysfs_ops,
+	.release = &pci_slot_release,
+	.default_groups = pci_slot_default_groups,
+};
+
+static char *make_slot_name(const char *name)
+{
+	char *new_name;
+	int len, max, dup;
+
+	new_name = kstrdup(name, GFP_KERNEL);
+	if (!new_name)
+		return NULL;
+
+	/*
+	 * Make sure we hit the realloc case the first time through the
+	 * loop.  'len' will be strlen(name) + 3 at that point which is
+	 * enough space for "name-X" and the trailing NUL.
+	 */
+	len = strlen(name) + 2;
+	max = 1;
+	dup = 1;
+
+	for (;;) {
+		struct kobject *dup_slot;
+		dup_slot = kset_find_obj(pci_slots_kset, new_name);
+		if (!dup_slot)
+			break;
+		kobject_put(dup_slot);
+		if (dup == max) {
+			len++;
+			max *= 10;
+			kfree(new_name);
+			new_name = kmalloc(len, GFP_KERNEL);
+			if (!new_name)
+				break;
+		}
+		sprintf(new_name, "%s-%d", name, dup++);
+	}
+
+	return new_name;
+}
+
+static int rename_slot(struct pci_slot *slot, const char *name)
+{
+	int result = 0;
+	char *slot_name;
+
+	if (strcmp(pci_slot_name(slot), name) == 0)
+		return result;
+
+	slot_name = make_slot_name(name);
+	if (!slot_name)
+		return -ENOMEM;
+
+	result = kobject_rename(&slot->kobj, slot_name);
+	kfree(slot_name);
+
+	return result;
+}
+
+void pci_dev_assign_slot(struct pci_dev *dev)
+{
+	struct pci_slot *slot;
+
+	mutex_lock(&pci_slot_mutex);
+	list_for_each_entry(slot, &dev->bus->slots, list)
+		if (pci_dev_matches_slot(dev, slot))
+			dev->slot = slot;
+	mutex_unlock(&pci_slot_mutex);
+}
+
+static struct pci_slot *get_slot(struct pci_bus *parent, int slot_nr)
+{
+	struct pci_slot *slot;
+
+	/* We already hold pci_slot_mutex */
+	list_for_each_entry(slot, &parent->slots, list)
+		if (slot->number == slot_nr) {
+			kobject_get(&slot->kobj);
+			return slot;
+		}
+
+	return NULL;
+}
+
+/**
+ * pci_create_slot - create or increment refcount for physical PCI slot
+ * @parent: struct pci_bus of parent bridge
+ * @slot_nr: PCI_SLOT(pci_dev->devfn), PCI_SLOT_PLACEHOLDER for placeholder, or
+ *	PCI_SLOT_ALL_DEVICES
+ * @name: user visible string presented in /sys/bus/pci/slots/<name>
+ * @hotplug: set if caller is hotplug driver, NULL otherwise
+ *
+ * PCI slots have first class attributes such as address, speed, width,
+ * and a &struct pci_slot is used to manage them. This interface will
+ * either return a new &struct pci_slot to the caller, or if the pci_slot
+ * already exists, its refcount will be incremented.
+ *
+ * Slots are uniquely identified by a @pci_bus, @slot_nr tuple.
+ *
+ * There are known platforms with broken firmware that assign the same
+ * name to multiple slots. Workaround these broken platforms by renaming
+ * the slots on behalf of the caller. If firmware assigns name N to
+ * multiple slots:
+ *
+ * The first slot is assigned N
+ * The second slot is assigned N-1
+ * The third slot is assigned N-2
+ * etc.
+ *
+ * Placeholder slots:
+ * In most cases, @pci_bus, @slot_nr will be sufficient to uniquely identify
+ * a slot. There is one notable exception - pSeries (rpaphp), where the
+ * @slot_nr cannot be determined until a device is actually inserted into
+ * the slot. In this scenario, the caller may pass PCI_SLOT_PLACEHOLDER for @slot_nr.
+ *
+ * The following semantics are imposed when the caller passes @slot_nr ==
+ * PCI_SLOT_PLACEHOLDER. First, we no longer check for an existing %struct
+ * pci_slot, as there may be many slots with @slot_nr of
+ * PCI_SLOT_PLACEHOLDER. The other change in semantics is user-visible,
+ * which is the 'address' parameter presented in sysfs will consist solely
+ * of a dddd:bb tuple, where dddd is the PCI domain of the %struct pci_bus
+ * and bb is the bus number. In other words, the devfn of the 'placeholder'
+ * slot will not be displayed.
+ *
+ * Bus-wide slots:
+ * For PCIe hotplug, the physical slot encompasses the entire secondary
+ * bus, not just a single device number. If the device supports ARI and ARI
+ * Forwarding is enabled in the upstream bridge, a multi-function device
+ * may include functions that appear to have several different device
+ * numbers, i.e., PCI_SLOT() values.  Pass @slot_nr == PCI_SLOT_ALL_DEVICES
+ * to create a slot that matches all devices on the bus. Unlike placeholder
+ * slots, bus-wide slots go through normal slot lookup and reuse existing
+ * slots if present.
+ */
+struct pci_slot *pci_create_slot(struct pci_bus *parent, int slot_nr,
+				 const char *name,
+				 struct hotplug_slot *hotplug)
+{
+	struct pci_dev *dev;
+	struct pci_slot *slot;
+	int err = 0;
+	char *slot_name = NULL;
+
+	mutex_lock(&pci_slot_mutex);
+
+	if (slot_nr == PCI_SLOT_PLACEHOLDER)
+		goto placeholder;
+
+	/*
+	 * Hotplug drivers are allowed to rename an existing slot,
+	 * but only if not already claimed.
+	 */
+	slot = get_slot(parent, slot_nr);
+	if (slot) {
+		if (hotplug) {
+			if (slot->hotplug) {
+				err = -EBUSY;
+				goto put_slot;
+			}
+			err = rename_slot(slot, name);
+			if (err)
+				goto put_slot;
+		}
+		goto out;
+	}
+
+placeholder:
+	slot = kzalloc_obj(*slot);
+	if (!slot) {
+		err = -ENOMEM;
+		goto err;
+	}
+
+	slot->bus = pci_bus_get(parent);
+	slot->number = slot_nr;
+
+	if (pci_slot_enabled_per_func())
+		slot->per_func_slot = 1;
+
+	slot->kobj.kset = pci_slots_kset;
+
+	slot_name = make_slot_name(name);
+	if (!slot_name) {
+		err = -ENOMEM;
+		pci_bus_put(slot->bus);
+		kfree(slot);
+		goto err;
+	}
+
+	INIT_LIST_HEAD(&slot->list);
+	list_add(&slot->list, &parent->slots);
+
+	err = kobject_init_and_add(&slot->kobj, &pci_slot_ktype, NULL,
+				   "%s", slot_name);
+	if (err)
+		goto put_slot;
+
+	down_read(&pci_bus_sem);
+	list_for_each_entry(dev, &parent->devices, bus_list)
+		if (pci_dev_matches_slot(dev, slot))
+			dev->slot = slot;
+	up_read(&pci_bus_sem);
+
+	dev_dbg(&parent->dev, "dev %02x, created physical slot %s\n",
+		slot_nr, pci_slot_name(slot));
+
+out:
+	kfree(slot_name);
+	mutex_unlock(&pci_slot_mutex);
+	return slot;
+
+put_slot:
+	kobject_put(&slot->kobj);
+err:
+	slot = ERR_PTR(err);
+	goto out;
+}
+EXPORT_SYMBOL_GPL(pci_create_slot);
+
+/**
+ * pci_destroy_slot - decrement refcount for physical PCI slot
+ * @slot: struct pci_slot to decrement
+ *
+ * %struct pci_slot is refcounted, so destroying them is really easy; we
+ * just call kobject_put on its kobj and let our release methods do the
+ * rest.
+ */
+void pci_destroy_slot(struct pci_slot *slot)
+{
+	dev_dbg(&slot->bus->dev, "dev %02x, dec refcount to %d\n",
+		slot->number, kref_read(&slot->kobj.kref) - 1);
+
+	mutex_lock(&pci_slot_mutex);
+	kobject_put(&slot->kobj);
+	mutex_unlock(&pci_slot_mutex);
+}
+EXPORT_SYMBOL_GPL(pci_destroy_slot);
+
+static int pci_slot_init(void)
+{
+	struct kset *pci_bus_kset;
+
+	pci_bus_kset = bus_get_kset(&pci_bus_type);
+	pci_slots_kset = kset_create_and_add("slots", NULL,
+						&pci_bus_kset->kobj);
+	if (!pci_slots_kset) {
+		pr_err("PCI: Slot initialization failure\n");
+		return -ENOMEM;
+	}
+	return 0;
+}
+
+subsys_initcall(pci_slot_init);