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, 166 insertions, 0 deletions

diff --git a/drivers/devfreq/imx-bus.c b/drivers/devfreq/imx-bus.c
new file mode 100644
index 000000000..49798f542
--- /dev/null
+++ b/drivers/devfreq/imx-bus.c
@@ -0,0 +1,166 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright 2019 NXP
+ */
+
+#include <linux/clk.h>
+#include <linux/devfreq.h>
+#include <linux/device.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/pm_opp.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+
+struct imx_bus {
+	struct devfreq_dev_profile profile;
+	struct devfreq *devfreq;
+	struct clk *clk;
+	struct platform_device *icc_pdev;
+};
+
+static int imx_bus_target(struct device *dev,
+		unsigned long *freq, u32 flags)
+{
+	struct dev_pm_opp *new_opp;
+	int ret;
+
+	new_opp = devfreq_recommended_opp(dev, freq, flags);
+	if (IS_ERR(new_opp)) {
+		ret = PTR_ERR(new_opp);
+		dev_err(dev, "failed to get recommended opp: %d\n", ret);
+		return ret;
+	}
+	dev_pm_opp_put(new_opp);
+
+	return dev_pm_opp_set_rate(dev, *freq);
+}
+
+static int imx_bus_get_cur_freq(struct device *dev, unsigned long *freq)
+{
+	struct imx_bus *priv = dev_get_drvdata(dev);
+
+	*freq = clk_get_rate(priv->clk);
+
+	return 0;
+}
+
+static void imx_bus_exit(struct device *dev)
+{
+	struct imx_bus *priv = dev_get_drvdata(dev);
+
+	dev_pm_opp_of_remove_table(dev);
+	platform_device_unregister(priv->icc_pdev);
+}
+
+/* imx_bus_init_icc() - register matching icc provider if required */
+static int imx_bus_init_icc(struct device *dev)
+{
+	struct imx_bus *priv = dev_get_drvdata(dev);
+	const char *icc_driver_name;
+
+	if (!of_property_present(dev->of_node, "#interconnect-cells"))
+		return 0;
+	if (!IS_ENABLED(CONFIG_INTERCONNECT_IMX)) {
+		dev_warn(dev, "imx interconnect drivers disabled\n");
+		return 0;
+	}
+
+	icc_driver_name = of_device_get_match_data(dev);
+	if (!icc_driver_name) {
+		dev_err(dev, "unknown interconnect driver\n");
+		return 0;
+	}
+
+	priv->icc_pdev = platform_device_register_data(
+			dev, icc_driver_name, -1, NULL, 0);
+	if (IS_ERR(priv->icc_pdev)) {
+		dev_err(dev, "failed to register icc provider %s: %ld\n",
+				icc_driver_name, PTR_ERR(priv->icc_pdev));
+		return PTR_ERR(priv->icc_pdev);
+	}
+
+	return 0;
+}
+
+static int imx_bus_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct imx_bus *priv;
+	const char *gov = DEVFREQ_GOV_USERSPACE;
+	int ret;
+
+	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	/*
+	 * Fetch the clock to adjust but don't explicitly enable.
+	 *
+	 * For imx bus clock clk_set_rate is safe no matter if the clock is on
+	 * or off and some peripheral side-buses might be off unless enabled by
+	 * drivers for devices on those specific buses.
+	 *
+	 * Rate adjustment on a disabled bus clock just takes effect later.
+	 */
+	priv->clk = devm_clk_get(dev, NULL);
+	if (IS_ERR(priv->clk)) {
+		ret = PTR_ERR(priv->clk);
+		dev_err(dev, "failed to fetch clk: %d\n", ret);
+		return ret;
+	}
+	platform_set_drvdata(pdev, priv);
+
+	ret = dev_pm_opp_of_add_table(dev);
+	if (ret < 0) {
+		dev_err(dev, "failed to get OPP table\n");
+		return ret;
+	}
+
+	priv->profile.target = imx_bus_target;
+	priv->profile.exit = imx_bus_exit;
+	priv->profile.get_cur_freq = imx_bus_get_cur_freq;
+	priv->profile.initial_freq = clk_get_rate(priv->clk);
+
+	priv->devfreq = devm_devfreq_add_device(dev, &priv->profile,
+						gov, NULL);
+	if (IS_ERR(priv->devfreq)) {
+		ret = PTR_ERR(priv->devfreq);
+		dev_err(dev, "failed to add devfreq device: %d\n", ret);
+		goto err;
+	}
+
+	ret = imx_bus_init_icc(dev);
+	if (ret)
+		goto err;
+
+	return 0;
+
+err:
+	dev_pm_opp_of_remove_table(dev);
+	return ret;
+}
+
+static const struct of_device_id imx_bus_of_match[] = {
+	{ .compatible = "fsl,imx8mq-noc", .data = "imx8mq-interconnect", },
+	{ .compatible = "fsl,imx8mm-noc", .data = "imx8mm-interconnect", },
+	{ .compatible = "fsl,imx8mn-noc", .data = "imx8mn-interconnect", },
+	{ .compatible = "fsl,imx8mp-noc", .data = "imx8mp-interconnect", },
+	{ .compatible = "fsl,imx8m-noc", },
+	{ .compatible = "fsl,imx8m-nic", },
+	{ /* sentinel */ },
+};
+MODULE_DEVICE_TABLE(of, imx_bus_of_match);
+
+static struct platform_driver imx_bus_platdrv = {
+	.probe		= imx_bus_probe,
+	.driver = {
+		.name	= "imx-bus-devfreq",
+		.of_match_table = imx_bus_of_match,
+	},
+};
+module_platform_driver(imx_bus_platdrv);
+
+MODULE_DESCRIPTION("Generic i.MX bus frequency scaling driver");
+MODULE_AUTHOR("Leonard Crestez <leonard.crestez@nxp.com>");
+MODULE_LICENSE("GPL v2");