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, 195 insertions, 0 deletions

diff --git a/drivers/xen/platform-pci.c b/drivers/xen/platform-pci.c
new file mode 100644
index 000000000..f24382325
--- /dev/null
+++ b/drivers/xen/platform-pci.c
@@ -0,0 +1,195 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/******************************************************************************
+ * platform-pci.c
+ *
+ * Xen platform PCI device driver
+ *
+ * Authors: ssmith@xensource.com and stefano.stabellini@eu.citrix.com
+ *
+ * Copyright (c) 2005, Intel Corporation.
+ * Copyright (c) 2007, XenSource Inc.
+ * Copyright (c) 2010, Citrix
+ */
+
+
+#include <linux/interrupt.h>
+#include <linux/io.h>
+#include <linux/init.h>
+#include <linux/pci.h>
+
+#include <xen/platform_pci.h>
+#include <xen/grant_table.h>
+#include <xen/xenbus.h>
+#include <xen/events.h>
+#include <xen/hvm.h>
+#include <xen/xen-ops.h>
+
+#define DRV_NAME    "xen-platform-pci"
+
+#define PCI_DEVICE_ID_XEN_PLATFORM_XS61	0x0002
+
+static unsigned long platform_mmio;
+static unsigned long platform_mmio_alloc;
+static unsigned long platform_mmiolen;
+static uint64_t callback_via;
+
+static unsigned long alloc_xen_mmio(unsigned long len)
+{
+	unsigned long addr;
+
+	addr = platform_mmio + platform_mmio_alloc;
+	platform_mmio_alloc += len;
+	BUG_ON(platform_mmio_alloc > platform_mmiolen);
+
+	return addr;
+}
+
+static uint64_t get_callback_via(struct pci_dev *pdev)
+{
+	u8 pin;
+	int irq;
+
+	irq = pdev->irq;
+	if (irq < 16)
+		return irq; /* ISA IRQ */
+
+	pin = pdev->pin;
+
+	/* We don't know the GSI. Specify the PCI INTx line instead. */
+	return ((uint64_t)HVM_PARAM_CALLBACK_TYPE_PCI_INTX <<
+			  HVM_CALLBACK_VIA_TYPE_SHIFT) |
+		((uint64_t)pci_domain_nr(pdev->bus) << 32) |
+		((uint64_t)pdev->bus->number << 16) |
+		((uint64_t)(pdev->devfn & 0xff) << 8) |
+		((uint64_t)(pin - 1) & 3);
+}
+
+static irqreturn_t do_hvm_evtchn_intr(int irq, void *dev_id)
+{
+	return xen_evtchn_do_upcall();
+}
+
+static int xen_allocate_irq(struct pci_dev *pdev)
+{
+	return request_irq(pdev->irq, do_hvm_evtchn_intr,
+			IRQF_NOBALANCING | IRQF_SHARED,
+			"xen-platform-pci", pdev);
+}
+
+static int platform_pci_resume(struct device *dev)
+{
+	int err;
+
+	if (xen_have_vector_callback)
+		return 0;
+
+	err = xen_set_callback_via(callback_via);
+	if (err) {
+		dev_err(dev, "platform_pci_resume failure!\n");
+		return err;
+	}
+	return 0;
+}
+
+static int platform_pci_probe(struct pci_dev *pdev,
+			      const struct pci_device_id *ent)
+{
+	int i, ret;
+	long ioaddr;
+	long mmio_addr, mmio_len;
+	unsigned int max_nr_gframes;
+	unsigned long grant_frames;
+
+	if (!xen_domain())
+		return -ENODEV;
+
+	i = pci_enable_device(pdev);
+	if (i)
+		return i;
+
+	ioaddr = pci_resource_start(pdev, 0);
+
+	mmio_addr = pci_resource_start(pdev, 1);
+	mmio_len = pci_resource_len(pdev, 1);
+
+	if (mmio_addr == 0 || ioaddr == 0) {
+		dev_err(&pdev->dev, "no resources found\n");
+		ret = -ENOENT;
+		goto pci_out;
+	}
+
+	ret = pci_request_region(pdev, 1, DRV_NAME);
+	if (ret < 0)
+		goto pci_out;
+
+	ret = pci_request_region(pdev, 0, DRV_NAME);
+	if (ret < 0)
+		goto mem_out;
+
+	platform_mmio = mmio_addr;
+	platform_mmiolen = mmio_len;
+	if (!xen_have_vector_callback) {
+		ret = xen_allocate_irq(pdev);
+		if (ret) {
+			dev_warn(&pdev->dev, "request_irq failed err=%d\n", ret);
+			goto out;
+		}
+		/*
+		 * It doesn't strictly *have* to run on CPU0 but it sure
+		 * as hell better process the event channel ports delivered
+		 * to CPU0.
+		 */
+		irq_set_affinity(pdev->irq, cpumask_of(0));
+
+		callback_via = get_callback_via(pdev);
+		ret = xen_set_callback_via(callback_via);
+		if (ret) {
+			dev_warn(&pdev->dev, "Unable to set the evtchn callback "
+					 "err=%d\n", ret);
+			goto irq_out;
+		}
+	}
+
+	max_nr_gframes = gnttab_max_grant_frames();
+	grant_frames = alloc_xen_mmio(PAGE_SIZE * max_nr_gframes);
+	ret = gnttab_setup_auto_xlat_frames(grant_frames);
+	if (ret)
+		goto irq_out;
+	ret = gnttab_init();
+	if (ret)
+		goto grant_out;
+	return 0;
+grant_out:
+	gnttab_free_auto_xlat_frames();
+irq_out:
+	if (!xen_have_vector_callback)
+		free_irq(pdev->irq, pdev);
+out:
+	pci_release_region(pdev, 0);
+mem_out:
+	pci_release_region(pdev, 1);
+pci_out:
+	pci_disable_device(pdev);
+	return ret;
+}
+
+static const struct pci_device_id platform_pci_tbl[] = {
+	{ PCI_VDEVICE(XEN, PCI_DEVICE_ID_XEN_PLATFORM) },
+	{ PCI_VDEVICE(XEN, PCI_DEVICE_ID_XEN_PLATFORM_XS61) },
+	{ }
+};
+
+static const struct dev_pm_ops platform_pm_ops = {
+	.resume_noirq =   platform_pci_resume,
+};
+
+static struct pci_driver platform_driver = {
+	.name =           DRV_NAME,
+	.probe =          platform_pci_probe,
+	.id_table =       platform_pci_tbl,
+	.driver = {
+		.pm =     &platform_pm_ops,
+	},
+};
+
+builtin_pci_driver(platform_driver);