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, 162 insertions, 0 deletions

diff --git a/drivers/rtc/rtc-imx-sm-bbm.c b/drivers/rtc/rtc-imx-sm-bbm.c
new file mode 100644
index 000000000..daa472be7
--- /dev/null
+++ b/drivers/rtc/rtc-imx-sm-bbm.c
@@ -0,0 +1,162 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright 2024 NXP.
+ */
+
+#include <linux/jiffies.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/rtc.h>
+#include <linux/scmi_protocol.h>
+#include <linux/scmi_imx_protocol.h>
+
+struct scmi_imx_bbm {
+	const struct scmi_imx_bbm_proto_ops *ops;
+	struct rtc_device *rtc_dev;
+	struct scmi_protocol_handle *ph;
+	struct notifier_block nb;
+};
+
+static int scmi_imx_bbm_read_time(struct device *dev, struct rtc_time *tm)
+{
+	struct scmi_imx_bbm *bbnsm = dev_get_drvdata(dev);
+	struct scmi_protocol_handle *ph = bbnsm->ph;
+	u64 val;
+	int ret;
+
+	ret = bbnsm->ops->rtc_time_get(ph, 0, &val);
+	if (ret)
+		return ret;
+
+	rtc_time64_to_tm(val, tm);
+
+	return 0;
+}
+
+static int scmi_imx_bbm_set_time(struct device *dev, struct rtc_time *tm)
+{
+	struct scmi_imx_bbm *bbnsm = dev_get_drvdata(dev);
+	struct scmi_protocol_handle *ph = bbnsm->ph;
+	u64 val;
+
+	val = rtc_tm_to_time64(tm);
+
+	return bbnsm->ops->rtc_time_set(ph, 0, val);
+}
+
+static int scmi_imx_bbm_alarm_irq_enable(struct device *dev, unsigned int enable)
+{
+	struct scmi_imx_bbm *bbnsm = dev_get_drvdata(dev);
+	struct scmi_protocol_handle *ph = bbnsm->ph;
+
+	/* scmi_imx_bbm_set_alarm enables the irq, just handle disable here */
+	if (!enable)
+		return bbnsm->ops->rtc_alarm_set(ph, 0, false, 0);
+
+	return 0;
+}
+
+static int scmi_imx_bbm_set_alarm(struct device *dev, struct rtc_wkalrm *alrm)
+{
+	struct scmi_imx_bbm *bbnsm = dev_get_drvdata(dev);
+	struct scmi_protocol_handle *ph = bbnsm->ph;
+	struct rtc_time *alrm_tm = &alrm->time;
+	u64 val;
+
+	val = rtc_tm_to_time64(alrm_tm);
+
+	return bbnsm->ops->rtc_alarm_set(ph, 0, true, val);
+}
+
+static const struct rtc_class_ops smci_imx_bbm_rtc_ops = {
+	.read_time = scmi_imx_bbm_read_time,
+	.set_time = scmi_imx_bbm_set_time,
+	.set_alarm = scmi_imx_bbm_set_alarm,
+	.alarm_irq_enable = scmi_imx_bbm_alarm_irq_enable,
+};
+
+static int scmi_imx_bbm_rtc_notifier(struct notifier_block *nb, unsigned long event, void *data)
+{
+	struct scmi_imx_bbm *bbnsm = container_of(nb, struct scmi_imx_bbm, nb);
+	struct scmi_imx_bbm_notif_report *r = data;
+
+	if (r->is_rtc)
+		rtc_update_irq(bbnsm->rtc_dev, 1, RTC_AF | RTC_IRQF);
+	else
+		pr_err("Unexpected bbm event: %s\n", __func__);
+
+	return 0;
+}
+
+static int scmi_imx_bbm_rtc_init(struct scmi_device *sdev)
+{
+	const struct scmi_handle *handle = sdev->handle;
+	struct device *dev = &sdev->dev;
+	struct scmi_imx_bbm *bbnsm = dev_get_drvdata(dev);
+	int ret;
+
+	bbnsm->rtc_dev = devm_rtc_allocate_device(dev);
+	if (IS_ERR(bbnsm->rtc_dev))
+		return PTR_ERR(bbnsm->rtc_dev);
+
+	bbnsm->rtc_dev->ops = &smci_imx_bbm_rtc_ops;
+	bbnsm->rtc_dev->range_max = U32_MAX;
+
+	bbnsm->nb.notifier_call = &scmi_imx_bbm_rtc_notifier;
+	ret = handle->notify_ops->devm_event_notifier_register(sdev, SCMI_PROTOCOL_IMX_BBM,
+							       SCMI_EVENT_IMX_BBM_RTC,
+							       NULL, &bbnsm->nb);
+	if (ret)
+		return ret;
+
+	return devm_rtc_register_device(bbnsm->rtc_dev);
+}
+
+static int scmi_imx_bbm_rtc_probe(struct scmi_device *sdev)
+{
+	const struct scmi_handle *handle = sdev->handle;
+	struct device *dev = &sdev->dev;
+	struct scmi_protocol_handle *ph;
+	struct scmi_imx_bbm *bbnsm;
+	int ret;
+
+	if (!handle)
+		return -ENODEV;
+
+	bbnsm = devm_kzalloc(dev, sizeof(*bbnsm), GFP_KERNEL);
+	if (!bbnsm)
+		return -ENOMEM;
+
+	bbnsm->ops = handle->devm_protocol_get(sdev, SCMI_PROTOCOL_IMX_BBM, &ph);
+	if (IS_ERR(bbnsm->ops))
+		return PTR_ERR(bbnsm->ops);
+
+	bbnsm->ph = ph;
+
+	device_init_wakeup(dev, true);
+
+	dev_set_drvdata(dev, bbnsm);
+
+	ret = scmi_imx_bbm_rtc_init(sdev);
+	if (ret)
+		device_init_wakeup(dev, false);
+
+	return ret;
+}
+
+static const struct scmi_device_id scmi_id_table[] = {
+	{ SCMI_PROTOCOL_IMX_BBM, "imx-bbm-rtc" },
+	{ },
+};
+MODULE_DEVICE_TABLE(scmi, scmi_id_table);
+
+static struct scmi_driver scmi_imx_bbm_rtc_driver = {
+	.name = "scmi-imx-bbm-rtc",
+	.probe = scmi_imx_bbm_rtc_probe,
+	.id_table = scmi_id_table,
+};
+module_scmi_driver(scmi_imx_bbm_rtc_driver);
+
+MODULE_AUTHOR("Peng Fan <peng.fan@nxp.com>");
+MODULE_DESCRIPTION("IMX SM BBM RTC driver");
+MODULE_LICENSE("GPL");