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, 373 insertions, 0 deletions

diff --git a/drivers/xen/pci.c b/drivers/xen/pci.c
new file mode 100644
index 000000000..385d2587b
--- /dev/null
+++ b/drivers/xen/pci.c
@@ -0,0 +1,373 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (c) 2009, Intel Corporation.
+ *
+ * Author: Weidong Han <weidong.han@intel.com>
+ */
+
+#include <linux/pci.h>
+#include <linux/acpi.h>
+#include <linux/pci-acpi.h>
+#include <xen/pci.h>
+#include <xen/xen.h>
+#include <xen/interface/physdev.h>
+#include <xen/interface/xen.h>
+
+#include <asm/xen/hypervisor.h>
+#include <asm/xen/hypercall.h>
+#include "../pci/pci.h"
+#ifdef CONFIG_PCI_MMCONFIG
+#include <asm/pci_x86.h>
+
+static int xen_mcfg_late(void);
+#endif
+
+static bool __read_mostly pci_seg_supported = true;
+
+static int xen_add_device(struct device *dev)
+{
+	int r;
+	struct pci_dev *pci_dev = to_pci_dev(dev);
+#ifdef CONFIG_PCI_IOV
+	struct pci_dev *physfn = pci_dev->physfn;
+#endif
+#ifdef CONFIG_PCI_MMCONFIG
+	static bool pci_mcfg_reserved = false;
+	/*
+	 * Reserve MCFG areas in Xen on first invocation due to this being
+	 * potentially called from inside of acpi_init immediately after
+	 * MCFG table has been finally parsed.
+	 */
+	if (!pci_mcfg_reserved) {
+		xen_mcfg_late();
+		pci_mcfg_reserved = true;
+	}
+#endif
+
+	if (pci_domain_nr(pci_dev->bus) >> 16) {
+		/*
+		 * The hypercall interface is limited to 16bit PCI segment
+		 * values, do not attempt to register devices with Xen in
+		 * segments greater or equal than 0x10000.
+		 */
+		dev_info(dev,
+			 "not registering with Xen: invalid PCI segment\n");
+		return 0;
+	}
+
+	if (pci_seg_supported) {
+		DEFINE_RAW_FLEX(struct physdev_pci_device_add, add, optarr, 1);
+
+		add->seg = pci_domain_nr(pci_dev->bus);
+		add->bus = pci_dev->bus->number;
+		add->devfn = pci_dev->devfn;
+
+#ifdef CONFIG_ACPI
+		acpi_handle handle;
+#endif
+
+#ifdef CONFIG_PCI_IOV
+		if (pci_dev->is_virtfn) {
+			add->flags = XEN_PCI_DEV_VIRTFN;
+			add->physfn.bus = physfn->bus->number;
+			add->physfn.devfn = physfn->devfn;
+		} else
+#endif
+		if (pci_ari_enabled(pci_dev->bus) && PCI_SLOT(pci_dev->devfn))
+			add->flags = XEN_PCI_DEV_EXTFN;
+
+#ifdef CONFIG_ACPI
+		handle = ACPI_HANDLE(&pci_dev->dev);
+#ifdef CONFIG_PCI_IOV
+		if (!handle && pci_dev->is_virtfn)
+			handle = ACPI_HANDLE(physfn->bus->bridge);
+#endif
+		if (!handle) {
+			/*
+			 * This device was not listed in the ACPI name space at
+			 * all. Try to get acpi handle of parent pci bus.
+			 */
+			struct pci_bus *pbus;
+			for (pbus = pci_dev->bus; pbus; pbus = pbus->parent) {
+				handle = acpi_pci_get_bridge_handle(pbus);
+				if (handle)
+					break;
+			}
+		}
+		if (handle) {
+			acpi_status status;
+
+			do {
+				unsigned long long pxm;
+
+				status = acpi_evaluate_integer(handle, "_PXM",
+							       NULL, &pxm);
+				if (ACPI_SUCCESS(status)) {
+					add->optarr[0] = pxm;
+					add->flags |= XEN_PCI_DEV_PXM;
+					break;
+				}
+				status = acpi_get_parent(handle, &handle);
+			} while (ACPI_SUCCESS(status));
+		}
+#endif /* CONFIG_ACPI */
+
+		r = HYPERVISOR_physdev_op(PHYSDEVOP_pci_device_add, add);
+		if (r != -ENOSYS)
+			return r;
+		pci_seg_supported = false;
+	}
+
+	if (pci_domain_nr(pci_dev->bus))
+		r = -ENOSYS;
+#ifdef CONFIG_PCI_IOV
+	else if (pci_dev->is_virtfn) {
+		struct physdev_manage_pci_ext manage_pci_ext = {
+			.bus		= pci_dev->bus->number,
+			.devfn		= pci_dev->devfn,
+			.is_virtfn 	= 1,
+			.physfn.bus	= physfn->bus->number,
+			.physfn.devfn	= physfn->devfn,
+		};
+
+		r = HYPERVISOR_physdev_op(PHYSDEVOP_manage_pci_add_ext,
+			&manage_pci_ext);
+	}
+#endif
+	else if (pci_ari_enabled(pci_dev->bus) && PCI_SLOT(pci_dev->devfn)) {
+		struct physdev_manage_pci_ext manage_pci_ext = {
+			.bus		= pci_dev->bus->number,
+			.devfn		= pci_dev->devfn,
+			.is_extfn	= 1,
+		};
+
+		r = HYPERVISOR_physdev_op(PHYSDEVOP_manage_pci_add_ext,
+			&manage_pci_ext);
+	} else {
+		struct physdev_manage_pci manage_pci = {
+			.bus	= pci_dev->bus->number,
+			.devfn	= pci_dev->devfn,
+		};
+
+		r = HYPERVISOR_physdev_op(PHYSDEVOP_manage_pci_add,
+			&manage_pci);
+	}
+
+	return r;
+}
+
+static int xen_remove_device(struct device *dev)
+{
+	int r;
+	struct pci_dev *pci_dev = to_pci_dev(dev);
+
+	if (pci_domain_nr(pci_dev->bus) >> 16) {
+		/*
+		 * The hypercall interface is limited to 16bit PCI segment
+		 * values.
+		 */
+		dev_info(dev,
+			 "not unregistering with Xen: invalid PCI segment\n");
+		return 0;
+	}
+
+	if (pci_seg_supported) {
+		struct physdev_pci_device device = {
+			.seg = pci_domain_nr(pci_dev->bus),
+			.bus = pci_dev->bus->number,
+			.devfn = pci_dev->devfn
+		};
+
+		r = HYPERVISOR_physdev_op(PHYSDEVOP_pci_device_remove,
+					  &device);
+	} else if (pci_domain_nr(pci_dev->bus))
+		r = -ENOSYS;
+	else {
+		struct physdev_manage_pci manage_pci = {
+			.bus = pci_dev->bus->number,
+			.devfn = pci_dev->devfn
+		};
+
+		r = HYPERVISOR_physdev_op(PHYSDEVOP_manage_pci_remove,
+					  &manage_pci);
+	}
+
+	return r;
+}
+
+int xen_reset_device(const struct pci_dev *dev)
+{
+	struct pci_device_reset device = {
+		.dev.seg = pci_domain_nr(dev->bus),
+		.dev.bus = dev->bus->number,
+		.dev.devfn = dev->devfn,
+		.flags = PCI_DEVICE_RESET_FLR,
+	};
+
+	if (pci_domain_nr(dev->bus) >> 16) {
+		/*
+		 * The hypercall interface is limited to 16bit PCI segment
+		 * values.
+		 */
+		dev_info(&dev->dev,
+			 "unable to notify Xen of device reset: invalid PCI segment\n");
+		return 0;
+	}
+
+	return HYPERVISOR_physdev_op(PHYSDEVOP_pci_device_reset, &device);
+}
+EXPORT_SYMBOL_GPL(xen_reset_device);
+
+static int xen_pci_notifier(struct notifier_block *nb,
+			    unsigned long action, void *data)
+{
+	struct device *dev = data;
+	int r = 0;
+
+	switch (action) {
+	case BUS_NOTIFY_ADD_DEVICE:
+		r = xen_add_device(dev);
+		break;
+	case BUS_NOTIFY_DEL_DEVICE:
+		r = xen_remove_device(dev);
+		break;
+	default:
+		return NOTIFY_DONE;
+	}
+	if (r)
+		dev_err(dev, "Failed to %s - passthrough or MSI/MSI-X might fail!\n",
+			action == BUS_NOTIFY_ADD_DEVICE ? "add" :
+			(action == BUS_NOTIFY_DEL_DEVICE ? "delete" : "?"));
+	return NOTIFY_OK;
+}
+
+static struct notifier_block device_nb = {
+	.notifier_call = xen_pci_notifier,
+};
+
+static int __init register_xen_pci_notifier(void)
+{
+	if (!xen_initial_domain())
+		return 0;
+
+	return bus_register_notifier(&pci_bus_type, &device_nb);
+}
+
+arch_initcall(register_xen_pci_notifier);
+
+#ifdef CONFIG_PCI_MMCONFIG
+static int xen_mcfg_late(void)
+{
+	struct pci_mmcfg_region *cfg;
+	int rc;
+
+	if (!xen_initial_domain())
+		return 0;
+
+	if ((pci_probe & PCI_PROBE_MMCONF) == 0)
+		return 0;
+
+	if (list_empty(&pci_mmcfg_list))
+		return 0;
+
+	/* Check whether they are in the right area. */
+	list_for_each_entry(cfg, &pci_mmcfg_list, list) {
+		struct physdev_pci_mmcfg_reserved r;
+
+		r.address = cfg->address;
+		r.segment = cfg->segment;
+		r.start_bus = cfg->start_bus;
+		r.end_bus = cfg->end_bus;
+		r.flags = XEN_PCI_MMCFG_RESERVED;
+
+		rc = HYPERVISOR_physdev_op(PHYSDEVOP_pci_mmcfg_reserved, &r);
+		switch (rc) {
+		case 0:
+		case -ENOSYS:
+			continue;
+
+		default:
+			pr_warn("Failed to report MMCONFIG reservation"
+				" state for %s to hypervisor"
+				" (%d)\n",
+				cfg->name, rc);
+		}
+	}
+	return 0;
+}
+#endif
+
+#ifdef CONFIG_XEN_DOM0
+struct xen_device_domain_owner {
+	domid_t domain;
+	struct pci_dev *dev;
+	struct list_head list;
+};
+
+static DEFINE_SPINLOCK(dev_domain_list_spinlock);
+static LIST_HEAD(dev_domain_list);
+
+static struct xen_device_domain_owner *find_device(struct pci_dev *dev)
+{
+	struct xen_device_domain_owner *owner;
+
+	list_for_each_entry(owner, &dev_domain_list, list) {
+		if (owner->dev == dev)
+			return owner;
+	}
+	return NULL;
+}
+
+int xen_find_device_domain_owner(struct pci_dev *dev)
+{
+	struct xen_device_domain_owner *owner;
+	int domain = -ENODEV;
+
+	spin_lock(&dev_domain_list_spinlock);
+	owner = find_device(dev);
+	if (owner)
+		domain = owner->domain;
+	spin_unlock(&dev_domain_list_spinlock);
+	return domain;
+}
+EXPORT_SYMBOL_GPL(xen_find_device_domain_owner);
+
+int xen_register_device_domain_owner(struct pci_dev *dev, uint16_t domain)
+{
+	struct xen_device_domain_owner *owner;
+
+	owner = kzalloc_obj(struct xen_device_domain_owner);
+	if (!owner)
+		return -ENODEV;
+
+	spin_lock(&dev_domain_list_spinlock);
+	if (find_device(dev)) {
+		spin_unlock(&dev_domain_list_spinlock);
+		kfree(owner);
+		return -EEXIST;
+	}
+	owner->domain = domain;
+	owner->dev = dev;
+	list_add_tail(&owner->list, &dev_domain_list);
+	spin_unlock(&dev_domain_list_spinlock);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(xen_register_device_domain_owner);
+
+int xen_unregister_device_domain_owner(struct pci_dev *dev)
+{
+	struct xen_device_domain_owner *owner;
+
+	spin_lock(&dev_domain_list_spinlock);
+	owner = find_device(dev);
+	if (!owner) {
+		spin_unlock(&dev_domain_list_spinlock);
+		return -ENODEV;
+	}
+	list_del(&owner->list);
+	spin_unlock(&dev_domain_list_spinlock);
+	kfree(owner);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(xen_unregister_device_domain_owner);
+#endif