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, 157 insertions, 0 deletions

diff --git a/drivers/mcb/mcb-pci.c b/drivers/mcb/mcb-pci.c
new file mode 100644
index 000000000..f1353da6e
--- /dev/null
+++ b/drivers/mcb/mcb-pci.c
@@ -0,0 +1,157 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * MEN Chameleon Bus.
+ *
+ * Copyright (C) 2014 MEN Mikroelektronik GmbH (www.men.de)
+ * Author: Johannes Thumshirn <johannes.thumshirn@men.de>
+ */
+
+#include <linux/module.h>
+#include <linux/pci.h>
+#include <linux/mcb.h>
+
+#include "mcb-internal.h"
+
+struct priv {
+	struct mcb_bus *bus;
+	phys_addr_t mapbase;
+	void __iomem *base;
+};
+
+static int mcb_pci_get_irq(struct mcb_device *mdev)
+{
+	struct mcb_bus *mbus = mdev->bus;
+	struct device *dev = mbus->carrier;
+	struct pci_dev *pdev = to_pci_dev(dev);
+
+	return pdev->irq;
+}
+
+static int mcb_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
+{
+	struct resource *res;
+	struct priv *priv;
+	int ret, table_size;
+	unsigned long flags;
+
+	priv = devm_kzalloc(&pdev->dev, sizeof(struct priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	ret = pci_enable_device(pdev);
+	if (ret) {
+		dev_err(&pdev->dev, "Failed to enable PCI device\n");
+		return -ENODEV;
+	}
+	pci_set_master(pdev);
+
+	flags = pci_resource_flags(pdev, 0);
+	if (flags & IORESOURCE_IO) {
+		ret = -ENOTSUPP;
+		dev_err(&pdev->dev,
+			"IO mapped PCI devices are not supported\n");
+		goto out_disable;
+	}
+
+	priv->mapbase = pci_resource_start(pdev, 0);
+	if (!priv->mapbase) {
+		dev_err(&pdev->dev, "No PCI resource\n");
+		ret = -ENODEV;
+		goto out_disable;
+	}
+
+	res = devm_request_mem_region(&pdev->dev, priv->mapbase,
+				      CHAM_HEADER_SIZE,
+				      KBUILD_MODNAME);
+	if (!res) {
+		dev_err(&pdev->dev, "Failed to request PCI memory\n");
+		ret = -EBUSY;
+		goto out_disable;
+	}
+
+	priv->base = devm_ioremap(&pdev->dev, priv->mapbase, CHAM_HEADER_SIZE);
+	if (!priv->base) {
+		dev_err(&pdev->dev, "Cannot ioremap\n");
+		ret = -ENOMEM;
+		goto out_disable;
+	}
+
+	pci_set_drvdata(pdev, priv);
+
+	priv->bus = mcb_alloc_bus(&pdev->dev);
+	if (IS_ERR(priv->bus)) {
+		ret = PTR_ERR(priv->bus);
+		goto out_disable;
+	}
+
+	priv->bus->get_irq = mcb_pci_get_irq;
+
+	ret = chameleon_parse_cells(priv->bus, priv->mapbase, priv->base);
+	if (ret < 0)
+		goto out_mcb_bus;
+
+	table_size = ret;
+
+	if (table_size < CHAM_HEADER_SIZE) {
+		/* Release the previous resources */
+		devm_iounmap(&pdev->dev, priv->base);
+		devm_release_mem_region(&pdev->dev, priv->mapbase, CHAM_HEADER_SIZE);
+
+		/* Then, allocate it again with the actual chameleon table size */
+		res = devm_request_mem_region(&pdev->dev, priv->mapbase,
+						table_size,
+						KBUILD_MODNAME);
+		if (!res) {
+			dev_err(&pdev->dev, "Failed to request PCI memory\n");
+			ret = -EBUSY;
+			goto out_mcb_bus;
+		}
+
+		priv->base = devm_ioremap(&pdev->dev, priv->mapbase, table_size);
+		if (!priv->base) {
+			dev_err(&pdev->dev, "Cannot ioremap\n");
+			ret = -ENOMEM;
+			goto out_mcb_bus;
+		}
+	}
+
+	mcb_bus_add_devices(priv->bus);
+
+	return 0;
+
+out_mcb_bus:
+	mcb_release_bus(priv->bus);
+out_disable:
+	pci_disable_device(pdev);
+	return ret;
+}
+
+static void mcb_pci_remove(struct pci_dev *pdev)
+{
+	struct priv *priv = pci_get_drvdata(pdev);
+
+	mcb_release_bus(priv->bus);
+
+	pci_disable_device(pdev);
+}
+
+static const struct pci_device_id mcb_pci_tbl[] = {
+	{ PCI_DEVICE(PCI_VENDOR_ID_MEN, PCI_DEVICE_ID_MEN_CHAMELEON) },
+	{ PCI_DEVICE(PCI_VENDOR_ID_ALTERA, PCI_DEVICE_ID_MEN_CHAMELEON) },
+	{ 0 },
+};
+MODULE_DEVICE_TABLE(pci, mcb_pci_tbl);
+
+static struct pci_driver mcb_pci_driver = {
+	.name = "mcb-pci",
+	.id_table = mcb_pci_tbl,
+	.probe = mcb_pci_probe,
+	.remove = mcb_pci_remove,
+};
+
+module_pci_driver(mcb_pci_driver);
+
+MODULE_AUTHOR("Johannes Thumshirn <johannes.thumshirn@men.de>");
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("MCB over PCI support");
+MODULE_IMPORT_NS("MCB");