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, 358 insertions, 0 deletions

diff --git a/drivers/rtc/rtc-ds1286.c b/drivers/rtc/rtc-ds1286.c
new file mode 100644
index 000000000..7acf849d4
--- /dev/null
+++ b/drivers/rtc/rtc-ds1286.c
@@ -0,0 +1,358 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * DS1286 Real Time Clock interface for Linux
+ *
+ * Copyright (C) 1998, 1999, 2000 Ralf Baechle
+ * Copyright (C) 2008 Thomas Bogendoerfer
+ *
+ * Based on code written by Paul Gortmaker.
+ */
+
+#include <linux/module.h>
+#include <linux/rtc.h>
+#include <linux/platform_device.h>
+#include <linux/bcd.h>
+#include <linux/rtc/ds1286.h>
+#include <linux/io.h>
+#include <linux/slab.h>
+
+struct ds1286_priv {
+	struct rtc_device *rtc;
+	u32 __iomem *rtcregs;
+	spinlock_t lock;
+};
+
+static inline u8 ds1286_rtc_read(struct ds1286_priv *priv, int reg)
+{
+	return __raw_readl(&priv->rtcregs[reg]) & 0xff;
+}
+
+static inline void ds1286_rtc_write(struct ds1286_priv *priv, u8 data, int reg)
+{
+	__raw_writel(data, &priv->rtcregs[reg]);
+}
+
+
+static int ds1286_alarm_irq_enable(struct device *dev, unsigned int enabled)
+{
+	struct ds1286_priv *priv = dev_get_drvdata(dev);
+	unsigned long flags;
+	unsigned char val;
+
+	/* Allow or mask alarm interrupts */
+	spin_lock_irqsave(&priv->lock, flags);
+	val = ds1286_rtc_read(priv, RTC_CMD);
+	if (enabled)
+		val &=  ~RTC_TDM;
+	else
+		val |=  RTC_TDM;
+	ds1286_rtc_write(priv, val, RTC_CMD);
+	spin_unlock_irqrestore(&priv->lock, flags);
+
+	return 0;
+}
+
+#ifdef CONFIG_RTC_INTF_DEV
+
+static int ds1286_ioctl(struct device *dev, unsigned int cmd, unsigned long arg)
+{
+	struct ds1286_priv *priv = dev_get_drvdata(dev);
+	unsigned long flags;
+	unsigned char val;
+
+	switch (cmd) {
+	case RTC_WIE_OFF:
+		/* Mask watchdog int. enab. bit	*/
+		spin_lock_irqsave(&priv->lock, flags);
+		val = ds1286_rtc_read(priv, RTC_CMD);
+		val |= RTC_WAM;
+		ds1286_rtc_write(priv, val, RTC_CMD);
+		spin_unlock_irqrestore(&priv->lock, flags);
+		break;
+	case RTC_WIE_ON:
+		/* Allow watchdog interrupts.	*/
+		spin_lock_irqsave(&priv->lock, flags);
+		val = ds1286_rtc_read(priv, RTC_CMD);
+		val &= ~RTC_WAM;
+		ds1286_rtc_write(priv, val, RTC_CMD);
+		spin_unlock_irqrestore(&priv->lock, flags);
+		break;
+	default:
+		return -ENOIOCTLCMD;
+	}
+	return 0;
+}
+
+#else
+#define ds1286_ioctl    NULL
+#endif
+
+#ifdef CONFIG_PROC_FS
+
+static int ds1286_proc(struct device *dev, struct seq_file *seq)
+{
+	struct ds1286_priv *priv = dev_get_drvdata(dev);
+	unsigned char month, cmd, amode;
+	const char *s;
+
+	month = ds1286_rtc_read(priv, RTC_MONTH);
+	seq_printf(seq,
+		   "oscillator\t: %s\n"
+		   "square_wave\t: %s\n",
+		   (month & RTC_EOSC) ? "disabled" : "enabled",
+		   (month & RTC_ESQW) ? "disabled" : "enabled");
+
+	amode = ((ds1286_rtc_read(priv, RTC_MINUTES_ALARM) & 0x80) >> 5) |
+		((ds1286_rtc_read(priv, RTC_HOURS_ALARM) & 0x80) >> 6) |
+		((ds1286_rtc_read(priv, RTC_DAY_ALARM) & 0x80) >> 7);
+	switch (amode) {
+	case 7:
+		s = "each minute";
+		break;
+	case 3:
+		s = "minutes match";
+		break;
+	case 1:
+		s = "hours and minutes match";
+		break;
+	case 0:
+		s = "days, hours and minutes match";
+		break;
+	default:
+		s = "invalid";
+		break;
+	}
+	seq_printf(seq, "alarm_mode\t: %s\n", s);
+
+	cmd = ds1286_rtc_read(priv, RTC_CMD);
+	seq_printf(seq,
+		   "alarm_enable\t: %s\n"
+		   "wdog_alarm\t: %s\n"
+		   "alarm_mask\t: %s\n"
+		   "wdog_alarm_mask\t: %s\n"
+		   "interrupt_mode\t: %s\n"
+		   "INTB_mode\t: %s_active\n"
+		   "interrupt_pins\t: %s\n",
+		   (cmd & RTC_TDF) ? "yes" : "no",
+		   (cmd & RTC_WAF) ? "yes" : "no",
+		   (cmd & RTC_TDM) ? "disabled" : "enabled",
+		   (cmd & RTC_WAM) ? "disabled" : "enabled",
+		   (cmd & RTC_PU_LVL) ? "pulse" : "level",
+		   (cmd & RTC_IBH_LO) ? "low" : "high",
+		   (cmd & RTC_IPSW) ? "unswapped" : "swapped");
+	return 0;
+}
+
+#else
+#define ds1286_proc     NULL
+#endif
+
+static int ds1286_read_time(struct device *dev, struct rtc_time *tm)
+{
+	struct ds1286_priv *priv = dev_get_drvdata(dev);
+	unsigned char save_control;
+	unsigned long flags;
+	unsigned long uip_watchdog = jiffies;
+
+	/*
+	 * read RTC once any update in progress is done. The update
+	 * can take just over 2ms. We wait 10 to 20ms. There is no need to
+	 * to poll-wait (up to 1s - eeccch) for the falling edge of RTC_UIP.
+	 * If you need to know *exactly* when a second has started, enable
+	 * periodic update complete interrupts, (via ioctl) and then
+	 * immediately read /dev/rtc which will block until you get the IRQ.
+	 * Once the read clears, read the RTC time (again via ioctl). Easy.
+	 */
+
+	if (ds1286_rtc_read(priv, RTC_CMD) & RTC_TE)
+		while (time_before(jiffies, uip_watchdog + 2*HZ/100))
+			barrier();
+
+	/*
+	 * Only the values that we read from the RTC are set. We leave
+	 * tm_wday, tm_yday and tm_isdst untouched. Even though the
+	 * RTC has RTC_DAY_OF_WEEK, we ignore it, as it is only updated
+	 * by the RTC when initially set to a non-zero value.
+	 */
+	spin_lock_irqsave(&priv->lock, flags);
+	save_control = ds1286_rtc_read(priv, RTC_CMD);
+	ds1286_rtc_write(priv, (save_control|RTC_TE), RTC_CMD);
+
+	tm->tm_sec = ds1286_rtc_read(priv, RTC_SECONDS);
+	tm->tm_min = ds1286_rtc_read(priv, RTC_MINUTES);
+	tm->tm_hour = ds1286_rtc_read(priv, RTC_HOURS) & 0x3f;
+	tm->tm_mday = ds1286_rtc_read(priv, RTC_DATE);
+	tm->tm_mon = ds1286_rtc_read(priv, RTC_MONTH) & 0x1f;
+	tm->tm_year = ds1286_rtc_read(priv, RTC_YEAR);
+
+	ds1286_rtc_write(priv, save_control, RTC_CMD);
+	spin_unlock_irqrestore(&priv->lock, flags);
+
+	tm->tm_sec = bcd2bin(tm->tm_sec);
+	tm->tm_min = bcd2bin(tm->tm_min);
+	tm->tm_hour = bcd2bin(tm->tm_hour);
+	tm->tm_mday = bcd2bin(tm->tm_mday);
+	tm->tm_mon = bcd2bin(tm->tm_mon);
+	tm->tm_year = bcd2bin(tm->tm_year);
+
+	/*
+	 * Account for differences between how the RTC uses the values
+	 * and how they are defined in a struct rtc_time;
+	 */
+	if (tm->tm_year < 45)
+		tm->tm_year += 30;
+	tm->tm_year += 40;
+	if (tm->tm_year < 70)
+		tm->tm_year += 100;
+
+	tm->tm_mon--;
+
+	return 0;
+}
+
+static int ds1286_set_time(struct device *dev, struct rtc_time *tm)
+{
+	struct ds1286_priv *priv = dev_get_drvdata(dev);
+	unsigned char mon, day, hrs, min, sec;
+	unsigned char save_control;
+	unsigned int yrs;
+	unsigned long flags;
+
+	yrs = tm->tm_year + 1900;
+	mon = tm->tm_mon + 1;   /* tm_mon starts at zero */
+	day = tm->tm_mday;
+	hrs = tm->tm_hour;
+	min = tm->tm_min;
+	sec = tm->tm_sec;
+
+	if (yrs < 1970)
+		return -EINVAL;
+
+	yrs -= 1940;
+	if (yrs > 255)    /* They are unsigned */
+		return -EINVAL;
+
+	if (yrs >= 100)
+		yrs -= 100;
+
+	sec = bin2bcd(sec);
+	min = bin2bcd(min);
+	hrs = bin2bcd(hrs);
+	day = bin2bcd(day);
+	mon = bin2bcd(mon);
+	yrs = bin2bcd(yrs);
+
+	spin_lock_irqsave(&priv->lock, flags);
+	save_control = ds1286_rtc_read(priv, RTC_CMD);
+	ds1286_rtc_write(priv, (save_control|RTC_TE), RTC_CMD);
+
+	ds1286_rtc_write(priv, yrs, RTC_YEAR);
+	ds1286_rtc_write(priv, mon, RTC_MONTH);
+	ds1286_rtc_write(priv, day, RTC_DATE);
+	ds1286_rtc_write(priv, hrs, RTC_HOURS);
+	ds1286_rtc_write(priv, min, RTC_MINUTES);
+	ds1286_rtc_write(priv, sec, RTC_SECONDS);
+	ds1286_rtc_write(priv, 0, RTC_HUNDREDTH_SECOND);
+
+	ds1286_rtc_write(priv, save_control, RTC_CMD);
+	spin_unlock_irqrestore(&priv->lock, flags);
+	return 0;
+}
+
+static int ds1286_read_alarm(struct device *dev, struct rtc_wkalrm *alm)
+{
+	struct ds1286_priv *priv = dev_get_drvdata(dev);
+	unsigned long flags;
+
+	/*
+	 * Only the values that we read from the RTC are set. That
+	 * means only tm_wday, tm_hour, tm_min.
+	 */
+	spin_lock_irqsave(&priv->lock, flags);
+	alm->time.tm_min = ds1286_rtc_read(priv, RTC_MINUTES_ALARM) & 0x7f;
+	alm->time.tm_hour = ds1286_rtc_read(priv, RTC_HOURS_ALARM)  & 0x1f;
+	alm->time.tm_wday = ds1286_rtc_read(priv, RTC_DAY_ALARM)    & 0x07;
+	ds1286_rtc_read(priv, RTC_CMD);
+	spin_unlock_irqrestore(&priv->lock, flags);
+
+	alm->time.tm_min = bcd2bin(alm->time.tm_min);
+	alm->time.tm_hour = bcd2bin(alm->time.tm_hour);
+	alm->time.tm_sec = 0;
+	return 0;
+}
+
+static int ds1286_set_alarm(struct device *dev, struct rtc_wkalrm *alm)
+{
+	struct ds1286_priv *priv = dev_get_drvdata(dev);
+	unsigned char hrs, min, sec;
+
+	hrs = alm->time.tm_hour;
+	min = alm->time.tm_min;
+	sec = alm->time.tm_sec;
+
+	if (hrs >= 24)
+		hrs = 0xff;
+
+	if (min >= 60)
+		min = 0xff;
+
+	if (sec != 0)
+		return -EINVAL;
+
+	min = bin2bcd(min);
+	hrs = bin2bcd(hrs);
+
+	spin_lock(&priv->lock);
+	ds1286_rtc_write(priv, hrs, RTC_HOURS_ALARM);
+	ds1286_rtc_write(priv, min, RTC_MINUTES_ALARM);
+	spin_unlock(&priv->lock);
+
+	return 0;
+}
+
+static const struct rtc_class_ops ds1286_ops = {
+	.ioctl		= ds1286_ioctl,
+	.proc		= ds1286_proc,
+	.read_time	= ds1286_read_time,
+	.set_time	= ds1286_set_time,
+	.read_alarm	= ds1286_read_alarm,
+	.set_alarm	= ds1286_set_alarm,
+	.alarm_irq_enable = ds1286_alarm_irq_enable,
+};
+
+static int ds1286_probe(struct platform_device *pdev)
+{
+	struct rtc_device *rtc;
+	struct ds1286_priv *priv;
+
+	priv = devm_kzalloc(&pdev->dev, sizeof(struct ds1286_priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	priv->rtcregs = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(priv->rtcregs))
+		return PTR_ERR(priv->rtcregs);
+
+	spin_lock_init(&priv->lock);
+	platform_set_drvdata(pdev, priv);
+	rtc = devm_rtc_device_register(&pdev->dev, "ds1286", &ds1286_ops,
+					THIS_MODULE);
+	if (IS_ERR(rtc))
+		return PTR_ERR(rtc);
+	priv->rtc = rtc;
+	return 0;
+}
+
+static struct platform_driver ds1286_platform_driver = {
+	.driver		= {
+		.name	= "rtc-ds1286",
+	},
+	.probe		= ds1286_probe,
+};
+
+module_platform_driver(ds1286_platform_driver);
+
+MODULE_AUTHOR("Thomas Bogendoerfer <tsbogend@alpha.franken.de>");
+MODULE_DESCRIPTION("DS1286 RTC driver");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:rtc-ds1286");