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, 148 insertions, 0 deletions

diff --git a/drivers/uio/uio_aec.c b/drivers/uio/uio_aec.c
new file mode 100644
index 000000000..dafcc5f44
--- /dev/null
+++ b/drivers/uio/uio_aec.c
@@ -0,0 +1,148 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * uio_aec.c -- simple driver for Adrienne Electronics Corp time code PCI device
+ *
+ * Copyright (C) 2008 Brandon Philips <brandon@ifup.org>
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/pci.h>
+#include <linux/init.h>
+#include <linux/interrupt.h>
+#include <linux/cdev.h>
+#include <linux/fs.h>
+#include <linux/io.h>
+#include <linux/uaccess.h>
+#include <linux/uio_driver.h>
+#include <linux/slab.h>
+
+#define PCI_VENDOR_ID_AEC 0xaecb
+#define PCI_DEVICE_ID_AEC_VITCLTC 0x6250
+
+#define INT_ENABLE_ADDR		0xFC
+#define INT_ENABLE		0x10
+#define INT_DISABLE		0x0
+
+#define INT_MASK_ADDR		0x2E
+#define INT_MASK_ALL		0x3F
+
+#define INTA_DRVR_ADDR		0xFE
+#define INTA_ENABLED_FLAG	0x08
+#define INTA_FLAG		0x01
+
+#define MAILBOX			0x0F
+
+static const struct pci_device_id ids[] = {
+	{ PCI_DEVICE(PCI_VENDOR_ID_AEC, PCI_DEVICE_ID_AEC_VITCLTC), },
+	{ 0, }
+};
+MODULE_DEVICE_TABLE(pci, ids);
+
+static irqreturn_t aectc_irq(int irq, struct uio_info *dev_info)
+{
+	void __iomem *int_flag = dev_info->priv + INTA_DRVR_ADDR;
+	unsigned char status = ioread8(int_flag);
+
+
+	if ((status & INTA_ENABLED_FLAG) && (status & INTA_FLAG)) {
+		/* application writes 0x00 to 0x2F to get next interrupt */
+		status = ioread8(dev_info->priv + MAILBOX);
+		return IRQ_HANDLED;
+	}
+
+	return IRQ_NONE;
+}
+
+static void print_board_data(struct pci_dev *pdev, struct uio_info *i)
+{
+	dev_info(&pdev->dev, "PCI-TC board vendor: %x%x number: %x%x"
+		" revision: %c%c\n",
+		ioread8(i->priv + 0x01),
+		ioread8(i->priv + 0x00),
+		ioread8(i->priv + 0x03),
+		ioread8(i->priv + 0x02),
+		ioread8(i->priv + 0x06),
+		ioread8(i->priv + 0x07));
+}
+
+static int probe(struct pci_dev *pdev, const struct pci_device_id *id)
+{
+	struct uio_info *info;
+	int ret;
+
+	info = devm_kzalloc(&pdev->dev, sizeof(struct uio_info), GFP_KERNEL);
+	if (!info)
+		return -ENOMEM;
+
+	if (pci_enable_device(pdev))
+		return -ENODEV;
+
+	if (pci_request_regions(pdev, "aectc"))
+		goto out_disable;
+
+	info->name = "aectc";
+	info->port[0].start = pci_resource_start(pdev, 0);
+	if (!info->port[0].start)
+		goto out_release;
+	info->priv = pci_iomap(pdev, 0, 0);
+	if (!info->priv)
+		goto out_release;
+	info->port[0].size = pci_resource_len(pdev, 0);
+	info->port[0].porttype = UIO_PORT_GPIO;
+
+	info->version = "0.0.1";
+	info->irq = pdev->irq;
+	info->irq_flags = IRQF_SHARED;
+	info->handler = aectc_irq;
+
+	print_board_data(pdev, info);
+	ret = uio_register_device(&pdev->dev, info);
+	if (ret)
+		goto out_unmap;
+
+	iowrite32(INT_ENABLE, info->priv + INT_ENABLE_ADDR);
+	iowrite8(INT_MASK_ALL, info->priv + INT_MASK_ADDR);
+	if (!(ioread8(info->priv + INTA_DRVR_ADDR)
+			& INTA_ENABLED_FLAG))
+		dev_err(&pdev->dev, "aectc: interrupts not enabled\n");
+
+	pci_set_drvdata(pdev, info);
+
+	return 0;
+
+out_unmap:
+	pci_iounmap(pdev, info->priv);
+out_release:
+	pci_release_regions(pdev);
+out_disable:
+	pci_disable_device(pdev);
+	return -ENODEV;
+}
+
+static void remove(struct pci_dev *pdev)
+{
+	struct uio_info *info = pci_get_drvdata(pdev);
+
+	/* disable interrupts */
+	iowrite8(INT_DISABLE, info->priv + INT_MASK_ADDR);
+	iowrite32(INT_DISABLE, info->priv + INT_ENABLE_ADDR);
+	/* read mailbox to ensure board drops irq */
+	ioread8(info->priv + MAILBOX);
+
+	uio_unregister_device(info);
+	pci_release_regions(pdev);
+	pci_disable_device(pdev);
+	pci_iounmap(pdev, info->priv);
+}
+
+static struct pci_driver pci_driver = {
+	.name = "aectc",
+	.id_table = ids,
+	.probe = probe,
+	.remove = remove,
+};
+
+module_pci_driver(pci_driver);
+MODULE_DESCRIPTION("Adrienne Electronics Corp time code PCI device");
+MODULE_LICENSE("GPL");