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, 174 insertions, 0 deletions

diff --git a/drivers/rtc/rtc-pl030.c b/drivers/rtc/rtc-pl030.c
new file mode 100644
index 000000000..5caaa714f
--- /dev/null
+++ b/drivers/rtc/rtc-pl030.c
@@ -0,0 +1,174 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ *  linux/drivers/rtc/rtc-pl030.c
+ *
+ *  Copyright (C) 2000-2001 Deep Blue Solutions Ltd.
+ */
+#include <linux/module.h>
+#include <linux/rtc.h>
+#include <linux/init.h>
+#include <linux/interrupt.h>
+#include <linux/amba/bus.h>
+#include <linux/io.h>
+#include <linux/slab.h>
+
+#define RTC_DR		(0)
+#define RTC_MR		(4)
+#define RTC_STAT	(8)
+#define RTC_EOI		(8)
+#define RTC_LR		(12)
+#define RTC_CR		(16)
+#define RTC_CR_MIE	(1 << 0)
+
+struct pl030_rtc {
+	void __iomem		*base;
+};
+
+static irqreturn_t pl030_interrupt(int irq, void *dev_id)
+{
+	struct pl030_rtc *rtc = dev_id;
+	writel(0, rtc->base + RTC_EOI);
+	return IRQ_HANDLED;
+}
+
+static int pl030_read_alarm(struct device *dev, struct rtc_wkalrm *alrm)
+{
+	struct pl030_rtc *rtc = dev_get_drvdata(dev);
+
+	rtc_time64_to_tm(readl(rtc->base + RTC_MR), &alrm->time);
+	return 0;
+}
+
+static int pl030_set_alarm(struct device *dev, struct rtc_wkalrm *alrm)
+{
+	struct pl030_rtc *rtc = dev_get_drvdata(dev);
+
+	writel(rtc_tm_to_time64(&alrm->time), rtc->base + RTC_MR);
+
+	return 0;
+}
+
+static int pl030_read_time(struct device *dev, struct rtc_time *tm)
+{
+	struct pl030_rtc *rtc = dev_get_drvdata(dev);
+
+	rtc_time64_to_tm(readl(rtc->base + RTC_DR), tm);
+
+	return 0;
+}
+
+/*
+ * Set the RTC time.  Unfortunately, we can't accurately set
+ * the point at which the counter updates.
+ *
+ * Also, since RTC_LR is transferred to RTC_CR on next rising
+ * edge of the 1Hz clock, we must write the time one second
+ * in advance.
+ */
+static int pl030_set_time(struct device *dev, struct rtc_time *tm)
+{
+	struct pl030_rtc *rtc = dev_get_drvdata(dev);
+
+	writel(rtc_tm_to_time64(tm) + 1, rtc->base + RTC_LR);
+
+	return 0;
+}
+
+static const struct rtc_class_ops pl030_ops = {
+	.read_time	= pl030_read_time,
+	.set_time	= pl030_set_time,
+	.read_alarm	= pl030_read_alarm,
+	.set_alarm	= pl030_set_alarm,
+};
+
+static int pl030_probe(struct amba_device *dev, const struct amba_id *id)
+{
+	struct pl030_rtc *rtc;
+	int ret;
+	struct rtc_device *rtc_dev;
+
+	ret = amba_request_regions(dev, NULL);
+	if (ret)
+		goto err_req;
+
+	rtc = devm_kzalloc(&dev->dev, sizeof(*rtc), GFP_KERNEL);
+	if (!rtc) {
+		ret = -ENOMEM;
+		goto err_rtc;
+	}
+
+	rtc_dev = devm_rtc_allocate_device(&dev->dev);
+	if (IS_ERR(rtc_dev)) {
+		ret = PTR_ERR(rtc_dev);
+		goto err_rtc;
+	}
+
+	rtc_dev->ops = &pl030_ops;
+	rtc_dev->range_max = U32_MAX;
+	rtc->base = ioremap(dev->res.start, resource_size(&dev->res));
+	if (!rtc->base) {
+		ret = -ENOMEM;
+		goto err_rtc;
+	}
+
+	__raw_writel(0, rtc->base + RTC_CR);
+	__raw_writel(0, rtc->base + RTC_EOI);
+
+	amba_set_drvdata(dev, rtc);
+
+	ret = request_irq(dev->irq[0], pl030_interrupt, 0,
+			  "rtc-pl030", rtc);
+	if (ret)
+		goto err_irq;
+
+	ret = devm_rtc_register_device(rtc_dev);
+	if (ret)
+		goto err_reg;
+
+	return 0;
+
+ err_reg:
+	free_irq(dev->irq[0], rtc);
+ err_irq:
+	iounmap(rtc->base);
+ err_rtc:
+	amba_release_regions(dev);
+ err_req:
+	return ret;
+}
+
+static void pl030_remove(struct amba_device *dev)
+{
+	struct pl030_rtc *rtc = amba_get_drvdata(dev);
+
+	writel(0, rtc->base + RTC_CR);
+
+	free_irq(dev->irq[0], rtc);
+	iounmap(rtc->base);
+	amba_release_regions(dev);
+}
+
+static const struct amba_id pl030_ids[] = {
+	{
+		.id	= 0x00041030,
+		.mask	= 0x000fffff,
+	},
+	{ 0, 0 },
+};
+
+MODULE_DEVICE_TABLE(amba, pl030_ids);
+
+static struct amba_driver pl030_driver = {
+	.drv		= {
+		.name	= "rtc-pl030",
+	},
+	.probe		= pl030_probe,
+	.remove		= pl030_remove,
+	.id_table	= pl030_ids,
+};
+
+module_amba_driver(pl030_driver);
+
+MODULE_AUTHOR("Russell King <rmk@arm.linux.org.uk>");
+MODULE_DESCRIPTION("ARM AMBA PL030 RTC Driver");
+MODULE_LICENSE("GPL");