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, 108 insertions, 0 deletions

diff --git a/drivers/power/reset/qcom-pon.c b/drivers/power/reset/qcom-pon.c
new file mode 100644
index 000000000..7e108982a
--- /dev/null
+++ b/drivers/power/reset/qcom-pon.c
@@ -0,0 +1,108 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2017-18 Linaro Limited
+
+#include <linux/delay.h>
+#include <linux/errno.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_platform.h>
+#include <linux/platform_device.h>
+#include <linux/reboot.h>
+#include <linux/reboot-mode.h>
+#include <linux/regmap.h>
+
+#define PON_SOFT_RB_SPARE		0x8f
+
+#define GEN1_REASON_SHIFT		2
+#define GEN2_REASON_SHIFT		1
+
+#define NO_REASON_SHIFT			0
+
+struct qcom_pon {
+	struct device *dev;
+	struct regmap *regmap;
+	u32 baseaddr;
+	struct reboot_mode_driver reboot_mode;
+	long reason_shift;
+};
+
+static int qcom_pon_reboot_mode_write(struct reboot_mode_driver *reboot,
+				    unsigned int magic)
+{
+	struct qcom_pon *pon = container_of
+			(reboot, struct qcom_pon, reboot_mode);
+	int ret;
+
+	ret = regmap_update_bits(pon->regmap,
+				 pon->baseaddr + PON_SOFT_RB_SPARE,
+				 GENMASK(7, pon->reason_shift),
+				 magic << pon->reason_shift);
+	if (ret < 0)
+		dev_err(pon->dev, "update reboot mode bits failed\n");
+
+	return ret;
+}
+
+static int qcom_pon_probe(struct platform_device *pdev)
+{
+	struct qcom_pon *pon;
+	long reason_shift;
+	int error;
+
+	pon = devm_kzalloc(&pdev->dev, sizeof(*pon), GFP_KERNEL);
+	if (!pon)
+		return -ENOMEM;
+
+	pon->dev = &pdev->dev;
+
+	pon->regmap = dev_get_regmap(pdev->dev.parent, NULL);
+	if (!pon->regmap) {
+		dev_err(&pdev->dev, "failed to locate regmap\n");
+		return -ENODEV;
+	}
+
+	error = of_property_read_u32(pdev->dev.of_node, "reg",
+				     &pon->baseaddr);
+	if (error)
+		return error;
+
+	reason_shift = (long)of_device_get_match_data(&pdev->dev);
+
+	if (reason_shift != NO_REASON_SHIFT) {
+		pon->reboot_mode.dev = &pdev->dev;
+		pon->reason_shift = reason_shift;
+		pon->reboot_mode.write = qcom_pon_reboot_mode_write;
+		error = devm_reboot_mode_register(&pdev->dev, &pon->reboot_mode);
+		if (error) {
+			dev_err(&pdev->dev, "can't register reboot mode\n");
+			return error;
+		}
+	}
+
+	platform_set_drvdata(pdev, pon);
+
+	return devm_of_platform_populate(&pdev->dev);
+}
+
+static const struct of_device_id qcom_pon_id_table[] = {
+	{ .compatible = "qcom,pm8916-pon", .data = (void *)GEN1_REASON_SHIFT },
+	{ .compatible = "qcom,pm8941-pon", .data = (void *)NO_REASON_SHIFT },
+	{ .compatible = "qcom,pms405-pon", .data = (void *)GEN1_REASON_SHIFT },
+	{ .compatible = "qcom,pm8998-pon", .data = (void *)GEN2_REASON_SHIFT },
+	{ .compatible = "qcom,pmk8350-pon", .data = (void *)GEN2_REASON_SHIFT },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, qcom_pon_id_table);
+
+static struct platform_driver qcom_pon_driver = {
+	.probe = qcom_pon_probe,
+	.driver = {
+		.name = "qcom-pon",
+		.of_match_table = qcom_pon_id_table,
+	},
+};
+module_platform_driver(qcom_pon_driver);
+
+MODULE_DESCRIPTION("Qualcomm Power On driver");
+MODULE_LICENSE("GPL v2");