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, 297 insertions, 0 deletions

diff --git a/drivers/rtc/rtc-nct6694.c b/drivers/rtc/rtc-nct6694.c
new file mode 100644
index 000000000..35401a0d9
--- /dev/null
+++ b/drivers/rtc/rtc-nct6694.c
@@ -0,0 +1,297 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Nuvoton NCT6694 RTC driver based on USB interface.
+ *
+ * Copyright (C) 2025 Nuvoton Technology Corp.
+ */
+
+#include <linux/bcd.h>
+#include <linux/irqdomain.h>
+#include <linux/kernel.h>
+#include <linux/mfd/nct6694.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/rtc.h>
+#include <linux/slab.h>
+
+/*
+ * USB command module type for NCT6694 RTC controller.
+ * This defines the module type used for communication with the NCT6694
+ * RTC controller over the USB interface.
+ */
+#define NCT6694_RTC_MOD		0x08
+
+/* Command 00h - RTC Time */
+#define NCT6694_RTC_TIME	0x0000
+#define NCT6694_RTC_TIME_SEL	0x00
+
+/* Command 01h - RTC Alarm */
+#define NCT6694_RTC_ALARM	0x01
+#define NCT6694_RTC_ALARM_SEL	0x00
+
+/* Command 02h - RTC Status */
+#define NCT6694_RTC_STATUS	0x02
+#define NCT6694_RTC_STATUS_SEL	0x00
+
+#define NCT6694_RTC_IRQ_INT_EN	BIT(0)	/* Transmit a USB INT-in when RTC alarm */
+#define NCT6694_RTC_IRQ_GPO_EN	BIT(5)	/* Trigger a GPO Low Pulse when RTC alarm */
+
+#define NCT6694_RTC_IRQ_EN	(NCT6694_RTC_IRQ_INT_EN | NCT6694_RTC_IRQ_GPO_EN)
+#define NCT6694_RTC_IRQ_STS	BIT(0)	/* Write 1 clear IRQ status */
+
+struct __packed nct6694_rtc_time {
+	u8 sec;
+	u8 min;
+	u8 hour;
+	u8 week;
+	u8 day;
+	u8 month;
+	u8 year;
+};
+
+struct __packed nct6694_rtc_alarm {
+	u8 sec;
+	u8 min;
+	u8 hour;
+	u8 alarm_en;
+	u8 alarm_pend;
+};
+
+struct __packed nct6694_rtc_status {
+	u8 irq_en;
+	u8 irq_pend;
+};
+
+union __packed nct6694_rtc_msg {
+	struct nct6694_rtc_time time;
+	struct nct6694_rtc_alarm alarm;
+	struct nct6694_rtc_status sts;
+};
+
+struct nct6694_rtc_data {
+	struct nct6694 *nct6694;
+	struct rtc_device *rtc;
+	union nct6694_rtc_msg *msg;
+	int irq;
+};
+
+static int nct6694_rtc_read_time(struct device *dev, struct rtc_time *tm)
+{
+	struct nct6694_rtc_data *data = dev_get_drvdata(dev);
+	struct nct6694_rtc_time *time = &data->msg->time;
+	static const struct nct6694_cmd_header cmd_hd = {
+		.mod = NCT6694_RTC_MOD,
+		.cmd = NCT6694_RTC_TIME,
+		.sel = NCT6694_RTC_TIME_SEL,
+		.len = cpu_to_le16(sizeof(*time))
+	};
+	int ret;
+
+	ret = nct6694_read_msg(data->nct6694, &cmd_hd, time);
+	if (ret)
+		return ret;
+
+	tm->tm_sec = bcd2bin(time->sec);		/* tm_sec expect 0 ~ 59 */
+	tm->tm_min = bcd2bin(time->min);		/* tm_min expect 0 ~ 59 */
+	tm->tm_hour = bcd2bin(time->hour);		/* tm_hour expect 0 ~ 23 */
+	tm->tm_wday = bcd2bin(time->week) - 1;		/* tm_wday expect 0 ~ 6 */
+	tm->tm_mday = bcd2bin(time->day);		/* tm_mday expect 1 ~ 31 */
+	tm->tm_mon = bcd2bin(time->month) - 1;		/* tm_month expect 0 ~ 11 */
+	tm->tm_year = bcd2bin(time->year) + 100;	/* tm_year expect since 1900 */
+
+	return ret;
+}
+
+static int nct6694_rtc_set_time(struct device *dev, struct rtc_time *tm)
+{
+	struct nct6694_rtc_data *data = dev_get_drvdata(dev);
+	struct nct6694_rtc_time *time = &data->msg->time;
+	static const struct nct6694_cmd_header cmd_hd = {
+		.mod = NCT6694_RTC_MOD,
+		.cmd = NCT6694_RTC_TIME,
+		.sel = NCT6694_RTC_TIME_SEL,
+		.len = cpu_to_le16(sizeof(*time))
+	};
+
+	time->sec = bin2bcd(tm->tm_sec);
+	time->min = bin2bcd(tm->tm_min);
+	time->hour = bin2bcd(tm->tm_hour);
+	time->week = bin2bcd(tm->tm_wday + 1);
+	time->day = bin2bcd(tm->tm_mday);
+	time->month = bin2bcd(tm->tm_mon + 1);
+	time->year = bin2bcd(tm->tm_year - 100);
+
+	return nct6694_write_msg(data->nct6694, &cmd_hd, time);
+}
+
+static int nct6694_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alrm)
+{
+	struct nct6694_rtc_data *data = dev_get_drvdata(dev);
+	struct nct6694_rtc_alarm *alarm = &data->msg->alarm;
+	static const struct nct6694_cmd_header cmd_hd = {
+		.mod = NCT6694_RTC_MOD,
+		.cmd = NCT6694_RTC_ALARM,
+		.sel = NCT6694_RTC_ALARM_SEL,
+		.len = cpu_to_le16(sizeof(*alarm))
+	};
+	int ret;
+
+	ret = nct6694_read_msg(data->nct6694, &cmd_hd, alarm);
+	if (ret)
+		return ret;
+
+	alrm->time.tm_sec = bcd2bin(alarm->sec);
+	alrm->time.tm_min = bcd2bin(alarm->min);
+	alrm->time.tm_hour = bcd2bin(alarm->hour);
+	alrm->enabled = alarm->alarm_en;
+	alrm->pending = alarm->alarm_pend;
+
+	return ret;
+}
+
+static int nct6694_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alrm)
+{
+	struct nct6694_rtc_data *data = dev_get_drvdata(dev);
+	struct nct6694_rtc_alarm *alarm = &data->msg->alarm;
+	static const struct nct6694_cmd_header cmd_hd = {
+		.mod = NCT6694_RTC_MOD,
+		.cmd = NCT6694_RTC_ALARM,
+		.sel = NCT6694_RTC_ALARM_SEL,
+		.len = cpu_to_le16(sizeof(*alarm))
+	};
+
+	alarm->sec = bin2bcd(alrm->time.tm_sec);
+	alarm->min = bin2bcd(alrm->time.tm_min);
+	alarm->hour = bin2bcd(alrm->time.tm_hour);
+	alarm->alarm_en = alrm->enabled ? NCT6694_RTC_IRQ_EN : 0;
+	alarm->alarm_pend = 0;
+
+	return nct6694_write_msg(data->nct6694, &cmd_hd, alarm);
+}
+
+static int nct6694_rtc_alarm_irq_enable(struct device *dev, unsigned int enabled)
+{
+	struct nct6694_rtc_data *data = dev_get_drvdata(dev);
+	struct nct6694_rtc_status *sts = &data->msg->sts;
+	static const struct nct6694_cmd_header cmd_hd = {
+		.mod = NCT6694_RTC_MOD,
+		.cmd = NCT6694_RTC_STATUS,
+		.sel = NCT6694_RTC_STATUS_SEL,
+		.len = cpu_to_le16(sizeof(*sts))
+	};
+
+	if (enabled)
+		sts->irq_en |= NCT6694_RTC_IRQ_EN;
+	else
+		sts->irq_en &= ~NCT6694_RTC_IRQ_EN;
+
+	sts->irq_pend = 0;
+
+	return nct6694_write_msg(data->nct6694, &cmd_hd, sts);
+}
+
+static const struct rtc_class_ops nct6694_rtc_ops = {
+	.read_time = nct6694_rtc_read_time,
+	.set_time = nct6694_rtc_set_time,
+	.read_alarm = nct6694_rtc_read_alarm,
+	.set_alarm = nct6694_rtc_set_alarm,
+	.alarm_irq_enable = nct6694_rtc_alarm_irq_enable,
+};
+
+static irqreturn_t nct6694_irq(int irq, void *dev_id)
+{
+	struct nct6694_rtc_data *data = dev_id;
+	struct nct6694_rtc_status *sts = &data->msg->sts;
+	static const struct nct6694_cmd_header cmd_hd = {
+		.mod = NCT6694_RTC_MOD,
+		.cmd = NCT6694_RTC_STATUS,
+		.sel = NCT6694_RTC_STATUS_SEL,
+		.len = cpu_to_le16(sizeof(*sts))
+	};
+	int ret;
+
+	rtc_lock(data->rtc);
+
+	sts->irq_en = NCT6694_RTC_IRQ_EN;
+	sts->irq_pend = NCT6694_RTC_IRQ_STS;
+	ret = nct6694_write_msg(data->nct6694, &cmd_hd, sts);
+	if (ret) {
+		rtc_unlock(data->rtc);
+		return IRQ_NONE;
+	}
+
+	rtc_update_irq(data->rtc, 1, RTC_IRQF | RTC_AF);
+
+	rtc_unlock(data->rtc);
+
+	return IRQ_HANDLED;
+}
+
+static void nct6694_irq_dispose_mapping(void *d)
+{
+	struct nct6694_rtc_data *data = d;
+
+	irq_dispose_mapping(data->irq);
+}
+
+static int nct6694_rtc_probe(struct platform_device *pdev)
+{
+	struct nct6694_rtc_data *data;
+	struct nct6694 *nct6694 = dev_get_drvdata(pdev->dev.parent);
+	int ret;
+
+	data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	data->msg = devm_kzalloc(&pdev->dev, sizeof(union nct6694_rtc_msg),
+				 GFP_KERNEL);
+	if (!data->msg)
+		return -ENOMEM;
+
+	data->irq = irq_create_mapping(nct6694->domain, NCT6694_IRQ_RTC);
+	if (!data->irq)
+		return -EINVAL;
+
+	ret = devm_add_action_or_reset(&pdev->dev, nct6694_irq_dispose_mapping,
+				       data);
+	if (ret)
+		return ret;
+
+	ret = devm_device_init_wakeup(&pdev->dev);
+	if (ret)
+		return dev_err_probe(&pdev->dev, ret, "Failed to init wakeup\n");
+
+	data->rtc = devm_rtc_allocate_device(&pdev->dev);
+	if (IS_ERR(data->rtc))
+		return PTR_ERR(data->rtc);
+
+	data->nct6694 = nct6694;
+	data->rtc->ops = &nct6694_rtc_ops;
+	data->rtc->range_min = RTC_TIMESTAMP_BEGIN_2000;
+	data->rtc->range_max = RTC_TIMESTAMP_END_2099;
+
+	platform_set_drvdata(pdev, data);
+
+	ret = devm_request_threaded_irq(&pdev->dev, data->irq, NULL,
+					nct6694_irq, IRQF_ONESHOT,
+					"rtc-nct6694", data);
+	if (ret < 0)
+		return dev_err_probe(&pdev->dev, ret, "Failed to request irq\n");
+
+	return devm_rtc_register_device(data->rtc);
+}
+
+static struct platform_driver nct6694_rtc_driver = {
+	.driver = {
+		.name	= "nct6694-rtc",
+	},
+	.probe		= nct6694_rtc_probe,
+};
+
+module_platform_driver(nct6694_rtc_driver);
+
+MODULE_DESCRIPTION("USB-RTC driver for NCT6694");
+MODULE_AUTHOR("Ming Yu <tmyu0@nuvoton.com>");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:nct6694-rtc");