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, 311 insertions, 0 deletions

diff --git a/drivers/rtc/rtc-st-lpc.c b/drivers/rtc/rtc-st-lpc.c
new file mode 100644
index 000000000..ae79ddf24
--- /dev/null
+++ b/drivers/rtc/rtc-st-lpc.c
@@ -0,0 +1,311 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * rtc-st-lpc.c - ST's LPC RTC, powered by the Low Power Timer
+ *
+ * Copyright (C) 2014 STMicroelectronics Limited
+ *
+ * Author: David Paris <david.paris@st.com> for STMicroelectronics
+ *         Lee Jones <lee.jones@linaro.org> for STMicroelectronics
+ *
+ * Based on the original driver written by Stuart Menefy.
+ */
+
+#include <linux/clk.h>
+#include <linux/delay.h>
+#include <linux/init.h>
+#include <linux/io.h>
+#include <linux/irq.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/rtc.h>
+
+#include <dt-bindings/mfd/st-lpc.h>
+
+/* Low Power Timer */
+#define LPC_LPT_LSB_OFF		0x400
+#define LPC_LPT_MSB_OFF		0x404
+#define LPC_LPT_START_OFF	0x408
+
+/* Low Power Alarm */
+#define LPC_LPA_LSB_OFF		0x410
+#define LPC_LPA_MSB_OFF		0x414
+#define LPC_LPA_START_OFF	0x418
+
+/* LPC as WDT */
+#define LPC_WDT_OFF		0x510
+#define LPC_WDT_FLAG_OFF	0x514
+
+struct st_rtc {
+	struct rtc_device *rtc_dev;
+	struct rtc_wkalrm alarm;
+	struct clk *clk;
+	unsigned long clkrate;
+	void __iomem *ioaddr;
+	bool irq_enabled:1;
+	spinlock_t lock;
+	short irq;
+};
+
+static void st_rtc_set_hw_alarm(struct st_rtc *rtc,
+				unsigned long msb, unsigned long  lsb)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&rtc->lock, flags);
+
+	writel_relaxed(1, rtc->ioaddr + LPC_WDT_OFF);
+
+	writel_relaxed(msb, rtc->ioaddr + LPC_LPA_MSB_OFF);
+	writel_relaxed(lsb, rtc->ioaddr + LPC_LPA_LSB_OFF);
+	writel_relaxed(1, rtc->ioaddr + LPC_LPA_START_OFF);
+
+	writel_relaxed(0, rtc->ioaddr + LPC_WDT_OFF);
+
+	spin_unlock_irqrestore(&rtc->lock, flags);
+}
+
+static irqreturn_t st_rtc_handler(int this_irq, void *data)
+{
+	struct st_rtc *rtc = (struct st_rtc *)data;
+
+	rtc_update_irq(rtc->rtc_dev, 1, RTC_AF);
+
+	return IRQ_HANDLED;
+}
+
+static int st_rtc_read_time(struct device *dev, struct rtc_time *tm)
+{
+	struct st_rtc *rtc = dev_get_drvdata(dev);
+	unsigned long lpt_lsb, lpt_msb;
+	unsigned long long lpt;
+	unsigned long flags;
+
+	spin_lock_irqsave(&rtc->lock, flags);
+
+	do {
+		lpt_msb = readl_relaxed(rtc->ioaddr + LPC_LPT_MSB_OFF);
+		lpt_lsb = readl_relaxed(rtc->ioaddr + LPC_LPT_LSB_OFF);
+	} while (readl_relaxed(rtc->ioaddr + LPC_LPT_MSB_OFF) != lpt_msb);
+
+	spin_unlock_irqrestore(&rtc->lock, flags);
+
+	lpt = ((unsigned long long)lpt_msb << 32) | lpt_lsb;
+	do_div(lpt, rtc->clkrate);
+	rtc_time64_to_tm(lpt, tm);
+
+	return 0;
+}
+
+static int st_rtc_set_time(struct device *dev, struct rtc_time *tm)
+{
+	struct st_rtc *rtc = dev_get_drvdata(dev);
+	unsigned long long lpt, secs;
+	unsigned long flags;
+
+	secs = rtc_tm_to_time64(tm);
+
+	lpt = (unsigned long long)secs * rtc->clkrate;
+
+	spin_lock_irqsave(&rtc->lock, flags);
+
+	writel_relaxed(lpt >> 32, rtc->ioaddr + LPC_LPT_MSB_OFF);
+	writel_relaxed(lpt, rtc->ioaddr + LPC_LPT_LSB_OFF);
+	writel_relaxed(1, rtc->ioaddr + LPC_LPT_START_OFF);
+
+	spin_unlock_irqrestore(&rtc->lock, flags);
+
+	return 0;
+}
+
+static int st_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *wkalrm)
+{
+	struct st_rtc *rtc = dev_get_drvdata(dev);
+	unsigned long flags;
+
+	spin_lock_irqsave(&rtc->lock, flags);
+
+	memcpy(wkalrm, &rtc->alarm, sizeof(struct rtc_wkalrm));
+
+	spin_unlock_irqrestore(&rtc->lock, flags);
+
+	return 0;
+}
+
+static int st_rtc_alarm_irq_enable(struct device *dev, unsigned int enabled)
+{
+	struct st_rtc *rtc = dev_get_drvdata(dev);
+
+	if (enabled && !rtc->irq_enabled) {
+		enable_irq(rtc->irq);
+		rtc->irq_enabled = true;
+	} else if (!enabled && rtc->irq_enabled) {
+		disable_irq(rtc->irq);
+		rtc->irq_enabled = false;
+	}
+
+	return 0;
+}
+
+static int st_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *t)
+{
+	struct st_rtc *rtc = dev_get_drvdata(dev);
+	struct rtc_time now;
+	unsigned long long now_secs;
+	unsigned long long alarm_secs;
+	unsigned long long lpa;
+
+	st_rtc_read_time(dev, &now);
+	now_secs = rtc_tm_to_time64(&now);
+	alarm_secs = rtc_tm_to_time64(&t->time);
+
+	memcpy(&rtc->alarm, t, sizeof(struct rtc_wkalrm));
+
+	/* Now many secs to fire */
+	alarm_secs -= now_secs;
+	lpa = (unsigned long long)alarm_secs * rtc->clkrate;
+
+	st_rtc_set_hw_alarm(rtc, lpa >> 32, lpa);
+	st_rtc_alarm_irq_enable(dev, t->enabled);
+
+	return 0;
+}
+
+static const struct rtc_class_ops st_rtc_ops = {
+	.read_time		= st_rtc_read_time,
+	.set_time		= st_rtc_set_time,
+	.read_alarm		= st_rtc_read_alarm,
+	.set_alarm		= st_rtc_set_alarm,
+	.alarm_irq_enable	= st_rtc_alarm_irq_enable,
+};
+
+static int st_rtc_probe(struct platform_device *pdev)
+{
+	struct device_node *np = pdev->dev.of_node;
+	struct st_rtc *rtc;
+	uint32_t mode;
+	int ret = 0;
+
+	ret = of_property_read_u32(np, "st,lpc-mode", &mode);
+	if (ret) {
+		dev_err(&pdev->dev, "An LPC mode must be provided\n");
+		return -EINVAL;
+	}
+
+	/* LPC can either run as a Clocksource or in RTC or WDT mode */
+	if (mode != ST_LPC_MODE_RTC)
+		return -ENODEV;
+
+	rtc = devm_kzalloc(&pdev->dev, sizeof(struct st_rtc), GFP_KERNEL);
+	if (!rtc)
+		return -ENOMEM;
+
+	rtc->rtc_dev = devm_rtc_allocate_device(&pdev->dev);
+	if (IS_ERR(rtc->rtc_dev))
+		return PTR_ERR(rtc->rtc_dev);
+
+	spin_lock_init(&rtc->lock);
+
+	rtc->ioaddr = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(rtc->ioaddr))
+		return PTR_ERR(rtc->ioaddr);
+
+	rtc->irq = platform_get_irq(pdev, 0);
+	if (rtc->irq < 0)
+		return rtc->irq;
+
+	ret = devm_request_irq(&pdev->dev, rtc->irq, st_rtc_handler,
+			       IRQF_NO_AUTOEN, pdev->name, rtc);
+	if (ret) {
+		dev_err(&pdev->dev, "Failed to request irq %i\n", rtc->irq);
+		return ret;
+	}
+
+	enable_irq_wake(rtc->irq);
+
+	rtc->clk = devm_clk_get_enabled(&pdev->dev, NULL);
+	if (IS_ERR(rtc->clk))
+		return dev_err_probe(&pdev->dev, PTR_ERR(rtc->clk),
+				     "Unable to request clock\n");
+
+	rtc->clkrate = clk_get_rate(rtc->clk);
+	if (!rtc->clkrate) {
+		dev_err(&pdev->dev, "Unable to fetch clock rate\n");
+		return -EINVAL;
+	}
+
+	device_set_wakeup_capable(&pdev->dev, 1);
+
+	platform_set_drvdata(pdev, rtc);
+
+	rtc->rtc_dev->ops = &st_rtc_ops;
+	rtc->rtc_dev->range_max = U64_MAX;
+	do_div(rtc->rtc_dev->range_max, rtc->clkrate);
+
+	ret = devm_rtc_register_device(rtc->rtc_dev);
+	if (ret)
+		return ret;
+
+	return 0;
+}
+
+#ifdef CONFIG_PM_SLEEP
+static int st_rtc_suspend(struct device *dev)
+{
+	struct st_rtc *rtc = dev_get_drvdata(dev);
+
+	if (device_may_wakeup(dev))
+		return 0;
+
+	writel_relaxed(1, rtc->ioaddr + LPC_WDT_OFF);
+	writel_relaxed(0, rtc->ioaddr + LPC_LPA_START_OFF);
+	writel_relaxed(0, rtc->ioaddr + LPC_WDT_OFF);
+
+	return 0;
+}
+
+static int st_rtc_resume(struct device *dev)
+{
+	struct st_rtc *rtc = dev_get_drvdata(dev);
+
+	rtc_alarm_irq_enable(rtc->rtc_dev, 0);
+
+	/*
+	 * clean 'rtc->alarm' to allow a new
+	 * .set_alarm to the upper RTC layer
+	 */
+	memset(&rtc->alarm, 0, sizeof(struct rtc_wkalrm));
+
+	writel_relaxed(0, rtc->ioaddr + LPC_LPA_MSB_OFF);
+	writel_relaxed(0, rtc->ioaddr + LPC_LPA_LSB_OFF);
+	writel_relaxed(1, rtc->ioaddr + LPC_WDT_OFF);
+	writel_relaxed(1, rtc->ioaddr + LPC_LPA_START_OFF);
+	writel_relaxed(0, rtc->ioaddr + LPC_WDT_OFF);
+
+	return 0;
+}
+#endif
+
+static SIMPLE_DEV_PM_OPS(st_rtc_pm_ops, st_rtc_suspend, st_rtc_resume);
+
+static const struct of_device_id st_rtc_match[] = {
+	{ .compatible = "st,stih407-lpc" },
+	{}
+};
+MODULE_DEVICE_TABLE(of, st_rtc_match);
+
+static struct platform_driver st_rtc_platform_driver = {
+	.driver = {
+		.name = "st-lpc-rtc",
+		.pm = &st_rtc_pm_ops,
+		.of_match_table = st_rtc_match,
+	},
+	.probe = st_rtc_probe,
+};
+
+module_platform_driver(st_rtc_platform_driver);
+
+MODULE_DESCRIPTION("STMicroelectronics LPC RTC driver");
+MODULE_AUTHOR("David Paris <david.paris@st.com>");
+MODULE_LICENSE("GPL");