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, 147 insertions, 0 deletions

diff --git a/drivers/clk/qcom/apcs-sdx55.c b/drivers/clk/qcom/apcs-sdx55.c
new file mode 100644
index 000000000..90dd1f185
--- /dev/null
+++ b/drivers/clk/qcom/apcs-sdx55.c
@@ -0,0 +1,147 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Qualcomm SDX55 APCS clock controller driver
+ *
+ * Copyright (c) 2020, Linaro Limited
+ * Author: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
+ */
+
+#include <linux/clk.h>
+#include <linux/clk-provider.h>
+#include <linux/cpu.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/pm_domain.h>
+#include <linux/regmap.h>
+#include <linux/slab.h>
+
+#include "clk-regmap.h"
+#include "clk-regmap-mux-div.h"
+
+static const u32 apcs_mux_clk_parent_map[] = { 0, 1, 5 };
+
+static const struct clk_parent_data pdata[] = {
+	{ .fw_name = "ref" },
+	{ .fw_name = "aux" },
+	{ .fw_name = "pll" },
+};
+
+/*
+ * We use the notifier function for switching to a temporary safe configuration
+ * (mux and divider), while the A7 PLL is reconfigured.
+ */
+static int a7cc_notifier_cb(struct notifier_block *nb, unsigned long event,
+			    void *data)
+{
+	int ret = 0;
+	struct clk_regmap_mux_div *md = container_of(nb,
+						     struct clk_regmap_mux_div,
+						     clk_nb);
+	if (event == PRE_RATE_CHANGE)
+		/* set the mux and divider to safe frequency (400mhz) */
+		ret = mux_div_set_src_div(md, 1, 2);
+
+	return notifier_from_errno(ret);
+}
+
+static int qcom_apcs_sdx55_clk_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct device *parent = dev->parent;
+	struct device *cpu_dev;
+	struct clk_regmap_mux_div *a7cc;
+	struct regmap *regmap;
+	struct clk_init_data init = { };
+	int ret;
+
+	regmap = dev_get_regmap(parent, NULL);
+	if (!regmap) {
+		dev_err(dev, "Failed to get parent regmap\n");
+		return -ENODEV;
+	}
+
+	a7cc = devm_kzalloc(dev, sizeof(*a7cc), GFP_KERNEL);
+	if (!a7cc)
+		return -ENOMEM;
+
+	init.name = "a7mux";
+	init.parent_data = pdata;
+	init.num_parents = ARRAY_SIZE(pdata);
+	init.ops = &clk_regmap_mux_div_ops;
+
+	a7cc->clkr.hw.init = &init;
+	a7cc->clkr.regmap = regmap;
+	a7cc->reg_offset = 0x8;
+	a7cc->hid_width = 5;
+	a7cc->hid_shift = 0;
+	a7cc->src_width = 3;
+	a7cc->src_shift = 8;
+	a7cc->parent_map = apcs_mux_clk_parent_map;
+
+	a7cc->pclk = devm_clk_get(parent, "pll");
+	if (IS_ERR(a7cc->pclk))
+		return dev_err_probe(dev, PTR_ERR(a7cc->pclk),
+				     "Failed to get PLL clk\n");
+
+	a7cc->clk_nb.notifier_call = a7cc_notifier_cb;
+	ret = clk_notifier_register(a7cc->pclk, &a7cc->clk_nb);
+	if (ret)
+		return dev_err_probe(dev, ret,
+				     "Failed to register clock notifier\n");
+
+	ret = devm_clk_register_regmap(dev, &a7cc->clkr);
+	if (ret) {
+		dev_err_probe(dev, ret, "Failed to register regmap clock\n");
+		goto err;
+	}
+
+	ret = devm_of_clk_add_hw_provider(dev, of_clk_hw_simple_get,
+					  &a7cc->clkr.hw);
+	if (ret) {
+		dev_err_probe(dev, ret, "Failed to add clock provider\n");
+		goto err;
+	}
+
+	platform_set_drvdata(pdev, a7cc);
+
+	/*
+	 * Attach the power domain to cpudev. Since there is no dedicated driver
+	 * for CPUs and the SDX55 platform lacks hardware specific CPUFreq
+	 * driver, there seems to be no better place to do this. So do it here!
+	 */
+	cpu_dev = get_cpu_device(0);
+	ret = dev_pm_domain_attach(cpu_dev, PD_FLAG_ATTACH_POWER_ON);
+	if (ret) {
+		dev_err_probe(dev, ret, "can't get PM domain: %d\n", ret);
+		goto err;
+	}
+
+	return 0;
+
+err:
+	clk_notifier_unregister(a7cc->pclk, &a7cc->clk_nb);
+	return ret;
+}
+
+static void qcom_apcs_sdx55_clk_remove(struct platform_device *pdev)
+{
+	struct device *cpu_dev = get_cpu_device(0);
+	struct clk_regmap_mux_div *a7cc = platform_get_drvdata(pdev);
+
+	clk_notifier_unregister(a7cc->pclk, &a7cc->clk_nb);
+	dev_pm_domain_detach(cpu_dev, true);
+}
+
+static struct platform_driver qcom_apcs_sdx55_clk_driver = {
+	.probe = qcom_apcs_sdx55_clk_probe,
+	.remove = qcom_apcs_sdx55_clk_remove,
+	.driver = {
+		.name = "qcom-sdx55-acps-clk",
+	},
+};
+module_platform_driver(qcom_apcs_sdx55_clk_driver);
+
+MODULE_AUTHOR("Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>");
+MODULE_LICENSE("GPL v2");
+MODULE_DESCRIPTION("Qualcomm SDX55 APCS clock driver");