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, 202 insertions, 0 deletions

diff --git a/drivers/rtc/rtc-bq4802.c b/drivers/rtc/rtc-bq4802.c
new file mode 100644
index 000000000..472e75668
--- /dev/null
+++ b/drivers/rtc/rtc-bq4802.c
@@ -0,0 +1,202 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/* rtc-bq4802.c: TI BQ4802 RTC driver.
+ *
+ * Copyright (C) 2008 David S. Miller <davem@davemloft.net>
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/io.h>
+#include <linux/platform_device.h>
+#include <linux/rtc.h>
+#include <linux/bcd.h>
+#include <linux/slab.h>
+
+MODULE_AUTHOR("David S. Miller <davem@davemloft.net>");
+MODULE_DESCRIPTION("TI BQ4802 RTC driver");
+MODULE_LICENSE("GPL");
+
+struct bq4802 {
+	void __iomem		*regs;
+	unsigned long		ioport;
+	struct rtc_device	*rtc;
+	spinlock_t		lock;
+	struct resource		*r;
+	u8 (*read)(struct bq4802 *, int);
+	void (*write)(struct bq4802 *, int, u8);
+};
+
+static u8 bq4802_read_io(struct bq4802 *p, int off)
+{
+	return inb(p->ioport + off);
+}
+
+static void bq4802_write_io(struct bq4802 *p, int off, u8 val)
+{
+	outb(val, p->ioport + off);
+}
+
+static u8 bq4802_read_mem(struct bq4802 *p, int off)
+{
+	return readb(p->regs + off);
+}
+
+static void bq4802_write_mem(struct bq4802 *p, int off, u8 val)
+{
+	writeb(val, p->regs + off);
+}
+
+static int bq4802_read_time(struct device *dev, struct rtc_time *tm)
+{
+	struct bq4802 *p = dev_get_drvdata(dev);
+	unsigned long flags;
+	unsigned int century;
+	u8 val;
+
+	spin_lock_irqsave(&p->lock, flags);
+
+	val = p->read(p, 0x0e);
+	p->write(p, 0xe, val | 0x08);
+
+	tm->tm_sec = p->read(p, 0x00);
+	tm->tm_min = p->read(p, 0x02);
+	tm->tm_hour = p->read(p, 0x04);
+	tm->tm_mday = p->read(p, 0x06);
+	tm->tm_mon = p->read(p, 0x09);
+	tm->tm_year = p->read(p, 0x0a);
+	tm->tm_wday = p->read(p, 0x08);
+	century = p->read(p, 0x0f);
+
+	p->write(p, 0x0e, val);
+
+	spin_unlock_irqrestore(&p->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);
+	tm->tm_wday = bcd2bin(tm->tm_wday);
+	century = bcd2bin(century);
+
+	tm->tm_year += (century * 100);
+	tm->tm_year -= 1900;
+
+	tm->tm_mon--;
+
+	return 0;
+}
+
+static int bq4802_set_time(struct device *dev, struct rtc_time *tm)
+{
+	struct bq4802 *p = dev_get_drvdata(dev);
+	u8 sec, min, hrs, day, mon, yrs, century, val;
+	unsigned long flags;
+	unsigned int year;
+
+	year = tm->tm_year + 1900;
+	century = year / 100;
+	yrs = year % 100;
+
+	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;
+
+	sec = bin2bcd(sec);
+	min = bin2bcd(min);
+	hrs = bin2bcd(hrs);
+	day = bin2bcd(day);
+	mon = bin2bcd(mon);
+	yrs = bin2bcd(yrs);
+	century = bin2bcd(century);
+
+	spin_lock_irqsave(&p->lock, flags);
+
+	val = p->read(p, 0x0e);
+	p->write(p, 0x0e, val | 0x08);
+
+	p->write(p, 0x00, sec);
+	p->write(p, 0x02, min);
+	p->write(p, 0x04, hrs);
+	p->write(p, 0x06, day);
+	p->write(p, 0x09, mon);
+	p->write(p, 0x0a, yrs);
+	p->write(p, 0x0f, century);
+
+	p->write(p, 0x0e, val);
+
+	spin_unlock_irqrestore(&p->lock, flags);
+
+	return 0;
+}
+
+static const struct rtc_class_ops bq4802_ops = {
+	.read_time	= bq4802_read_time,
+	.set_time	= bq4802_set_time,
+};
+
+static int bq4802_probe(struct platform_device *pdev)
+{
+	struct bq4802 *p = devm_kzalloc(&pdev->dev, sizeof(*p), GFP_KERNEL);
+	int err = -ENOMEM;
+
+	if (!p)
+		goto out;
+
+	spin_lock_init(&p->lock);
+
+	p->r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (!p->r) {
+		p->r = platform_get_resource(pdev, IORESOURCE_IO, 0);
+		err = -EINVAL;
+		if (!p->r)
+			goto out;
+	}
+	if (p->r->flags & IORESOURCE_IO) {
+		p->ioport = p->r->start;
+		p->read = bq4802_read_io;
+		p->write = bq4802_write_io;
+	} else if (p->r->flags & IORESOURCE_MEM) {
+		p->regs = devm_ioremap(&pdev->dev, p->r->start,
+					resource_size(p->r));
+		if (!p->regs){
+			err = -ENOMEM;
+			goto out;
+		}
+		p->read = bq4802_read_mem;
+		p->write = bq4802_write_mem;
+	} else {
+		err = -EINVAL;
+		goto out;
+	}
+
+	platform_set_drvdata(pdev, p);
+
+	p->rtc = devm_rtc_device_register(&pdev->dev, "bq4802",
+					&bq4802_ops, THIS_MODULE);
+	if (IS_ERR(p->rtc)) {
+		err = PTR_ERR(p->rtc);
+		goto out;
+	}
+
+	err = 0;
+out:
+	return err;
+
+}
+
+/* work with hotplug and coldplug */
+MODULE_ALIAS("platform:rtc-bq4802");
+
+static struct platform_driver bq4802_driver = {
+	.driver		= {
+		.name	= "rtc-bq4802",
+	},
+	.probe		= bq4802_probe,
+};
+
+module_platform_driver(bq4802_driver);