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, 187 insertions, 0 deletions

diff --git a/drivers/mcb/mcb-lpc.c b/drivers/mcb/mcb-lpc.c
new file mode 100644
index 000000000..070aa787a
--- /dev/null
+++ b/drivers/mcb/mcb-lpc.c
@@ -0,0 +1,187 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * MEN Chameleon Bus.
+ *
+ * Copyright (C) 2014 MEN Mikroelektronik GmbH (www.men.de)
+ * Author: Andreas Werner <andreas.werner@men.de>
+ */
+
+#include <linux/platform_device.h>
+#include <linux/module.h>
+#include <linux/dmi.h>
+#include <linux/mcb.h>
+#include <linux/io.h>
+#include "mcb-internal.h"
+
+struct priv {
+	struct mcb_bus *bus;
+	struct resource *mem;
+	void __iomem *base;
+};
+
+static int mcb_lpc_probe(struct platform_device *pdev)
+{
+	struct resource *res;
+	struct priv *priv;
+	int ret = 0, table_size;
+
+	priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	priv->mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (!priv->mem) {
+		dev_err(&pdev->dev, "No Memory resource\n");
+		return -ENODEV;
+	}
+
+	res = devm_request_mem_region(&pdev->dev, priv->mem->start,
+				      resource_size(priv->mem),
+				      KBUILD_MODNAME);
+	if (!res) {
+		dev_err(&pdev->dev, "Failed to request IO memory\n");
+		return -EBUSY;
+	}
+
+	priv->base = devm_ioremap(&pdev->dev, priv->mem->start,
+				  resource_size(priv->mem));
+	if (!priv->base) {
+		dev_err(&pdev->dev, "Cannot ioremap\n");
+		return -ENOMEM;
+	}
+
+	platform_set_drvdata(pdev, priv);
+
+	priv->bus = mcb_alloc_bus(&pdev->dev);
+	if (IS_ERR(priv->bus))
+		return PTR_ERR(priv->bus);
+
+	ret = chameleon_parse_cells(priv->bus, priv->mem->start, 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->mem->start, resource_size(priv->mem));
+
+		/* Then, allocate it again with the actual chameleon table size */
+		res = devm_request_mem_region(&pdev->dev, priv->mem->start,
+					      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->mem->start, table_size);
+		if (!priv->base) {
+			dev_err(&pdev->dev, "Cannot ioremap\n");
+			ret = -ENOMEM;
+			goto out_mcb_bus;
+		}
+
+		platform_set_drvdata(pdev, priv);
+	}
+
+	mcb_bus_add_devices(priv->bus);
+
+	return 0;
+
+out_mcb_bus:
+	mcb_release_bus(priv->bus);
+	return ret;
+}
+
+static void mcb_lpc_remove(struct platform_device *pdev)
+{
+	struct priv *priv = platform_get_drvdata(pdev);
+
+	mcb_release_bus(priv->bus);
+}
+
+static struct platform_device *mcb_lpc_pdev;
+
+static int mcb_lpc_create_platform_device(const struct dmi_system_id *id)
+{
+	struct resource *res = id->driver_data;
+	int ret;
+
+	mcb_lpc_pdev = platform_device_alloc("mcb-lpc", -1);
+	if (!mcb_lpc_pdev)
+		return -ENOMEM;
+
+	ret = platform_device_add_resources(mcb_lpc_pdev, res, 1);
+	if (ret)
+		goto out_put;
+
+	ret = platform_device_add(mcb_lpc_pdev);
+	if (ret)
+		goto out_put;
+
+	return 0;
+
+out_put:
+	platform_device_put(mcb_lpc_pdev);
+	return ret;
+}
+
+static struct resource sc24_fpga_resource = DEFINE_RES_MEM(0xe000e000, CHAM_HEADER_SIZE);
+static struct resource sc31_fpga_resource = DEFINE_RES_MEM(0xf000e000, CHAM_HEADER_SIZE);
+
+static struct platform_driver mcb_lpc_driver = {
+	.driver		= {
+		.name = "mcb-lpc",
+	},
+	.probe		= mcb_lpc_probe,
+	.remove		= mcb_lpc_remove,
+};
+
+static const struct dmi_system_id mcb_lpc_dmi_table[] = {
+	{
+		.ident = "SC24",
+		.matches = {
+			DMI_MATCH(DMI_SYS_VENDOR, "MEN"),
+			DMI_MATCH(DMI_PRODUCT_VERSION, "14SC24"),
+		},
+		.driver_data = (void *)&sc24_fpga_resource,
+		.callback = mcb_lpc_create_platform_device,
+	},
+	{
+		.ident = "SC31",
+		.matches = {
+			DMI_MATCH(DMI_SYS_VENDOR, "MEN"),
+			DMI_MATCH(DMI_PRODUCT_VERSION, "14SC31"),
+		},
+		.driver_data = (void *)&sc31_fpga_resource,
+		.callback = mcb_lpc_create_platform_device,
+	},
+	{}
+};
+MODULE_DEVICE_TABLE(dmi, mcb_lpc_dmi_table);
+
+static int __init mcb_lpc_init(void)
+{
+	if (!dmi_check_system(mcb_lpc_dmi_table))
+		return -ENODEV;
+
+	return platform_driver_register(&mcb_lpc_driver);
+}
+
+static void __exit mcb_lpc_exit(void)
+{
+	platform_device_unregister(mcb_lpc_pdev);
+	platform_driver_unregister(&mcb_lpc_driver);
+}
+
+module_init(mcb_lpc_init);
+module_exit(mcb_lpc_exit);
+
+MODULE_AUTHOR("Andreas Werner <andreas.werner@men.de>");
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("MCB over LPC support");
+MODULE_IMPORT_NS("MCB");