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, 213 insertions, 0 deletions

diff --git a/drivers/rtc/rtc-ds1302.c b/drivers/rtc/rtc-ds1302.c
new file mode 100644
index 000000000..ecc7d0307
--- /dev/null
+++ b/drivers/rtc/rtc-ds1302.c
@@ -0,0 +1,213 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Dallas DS1302 RTC Support
+ *
+ *  Copyright (C) 2002 David McCullough
+ *  Copyright (C) 2003 - 2007 Paul Mundt
+ */
+
+#include <linux/bcd.h>
+#include <linux/init.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/rtc.h>
+#include <linux/spi/spi.h>
+
+#define	RTC_CMD_READ	0x81		/* Read command */
+#define	RTC_CMD_WRITE	0x80		/* Write command */
+
+#define	RTC_CMD_WRITE_ENABLE	0x00		/* Write enable */
+#define	RTC_CMD_WRITE_DISABLE	0x80		/* Write disable */
+
+#define RTC_ADDR_RAM0	0x20		/* Address of RAM0 */
+#define RTC_ADDR_TCR	0x08		/* Address of trickle charge register */
+#define RTC_CLCK_BURST	0x1F		/* Address of clock burst */
+#define	RTC_CLCK_LEN	0x08		/* Size of clock burst */
+#define	RTC_ADDR_CTRL	0x07		/* Address of control register */
+#define	RTC_ADDR_YEAR	0x06		/* Address of year register */
+#define	RTC_ADDR_DAY	0x05		/* Address of day of week register */
+#define	RTC_ADDR_MON	0x04		/* Address of month register */
+#define	RTC_ADDR_DATE	0x03		/* Address of day of month register */
+#define	RTC_ADDR_HOUR	0x02		/* Address of hour register */
+#define	RTC_ADDR_MIN	0x01		/* Address of minute register */
+#define	RTC_ADDR_SEC	0x00		/* Address of second register */
+
+static int ds1302_rtc_set_time(struct device *dev, struct rtc_time *time)
+{
+	struct spi_device	*spi = dev_get_drvdata(dev);
+	u8		buf[1 + RTC_CLCK_LEN];
+	u8		*bp;
+	int		status;
+
+	/* Enable writing */
+	bp = buf;
+	*bp++ = RTC_ADDR_CTRL << 1 | RTC_CMD_WRITE;
+	*bp++ = RTC_CMD_WRITE_ENABLE;
+
+	status = spi_write_then_read(spi, buf, 2,
+			NULL, 0);
+	if (status)
+		return status;
+
+	/* Write registers starting at the first time/date address. */
+	bp = buf;
+	*bp++ = RTC_CLCK_BURST << 1 | RTC_CMD_WRITE;
+
+	*bp++ = bin2bcd(time->tm_sec);
+	*bp++ = bin2bcd(time->tm_min);
+	*bp++ = bin2bcd(time->tm_hour);
+	*bp++ = bin2bcd(time->tm_mday);
+	*bp++ = bin2bcd(time->tm_mon + 1);
+	*bp++ = time->tm_wday + 1;
+	*bp++ = bin2bcd(time->tm_year % 100);
+	*bp++ = RTC_CMD_WRITE_DISABLE;
+
+	/* use write-then-read since dma from stack is nonportable */
+	return spi_write_then_read(spi, buf, sizeof(buf),
+			NULL, 0);
+}
+
+static int ds1302_rtc_get_time(struct device *dev, struct rtc_time *time)
+{
+	struct spi_device	*spi = dev_get_drvdata(dev);
+	u8		addr = RTC_CLCK_BURST << 1 | RTC_CMD_READ;
+	u8		buf[RTC_CLCK_LEN - 1];
+	int		status;
+
+	/* Use write-then-read to get all the date/time registers
+	 * since dma from stack is nonportable
+	 */
+	status = spi_write_then_read(spi, &addr, sizeof(addr),
+			buf, sizeof(buf));
+	if (status < 0)
+		return status;
+
+	/* Decode the registers */
+	time->tm_sec = bcd2bin(buf[RTC_ADDR_SEC]);
+	time->tm_min = bcd2bin(buf[RTC_ADDR_MIN]);
+	time->tm_hour = bcd2bin(buf[RTC_ADDR_HOUR]);
+	time->tm_wday = buf[RTC_ADDR_DAY] - 1;
+	time->tm_mday = bcd2bin(buf[RTC_ADDR_DATE]);
+	time->tm_mon = bcd2bin(buf[RTC_ADDR_MON]) - 1;
+	time->tm_year = bcd2bin(buf[RTC_ADDR_YEAR]) + 100;
+
+	return 0;
+}
+
+static const struct rtc_class_ops ds1302_rtc_ops = {
+	.read_time	= ds1302_rtc_get_time,
+	.set_time	= ds1302_rtc_set_time,
+};
+
+static int ds1302_probe(struct spi_device *spi)
+{
+	struct rtc_device	*rtc;
+	u8		addr;
+	u8		buf[4];
+	u8		*bp;
+	int		status;
+
+	/* Sanity check board setup data.  This may be hooked up
+	 * in 3wire mode, but we don't care.  Note that unless
+	 * there's an inverter in place, this needs SPI_CS_HIGH!
+	 */
+	if (spi->bits_per_word && (spi->bits_per_word != 8)) {
+		dev_err(&spi->dev, "bad word length\n");
+		return -EINVAL;
+	} else if (spi->max_speed_hz > 2000000) {
+		dev_err(&spi->dev, "speed is too high\n");
+		return -EINVAL;
+	} else if (spi->mode & SPI_CPHA) {
+		dev_err(&spi->dev, "bad mode\n");
+		return -EINVAL;
+	}
+
+	addr = RTC_ADDR_CTRL << 1 | RTC_CMD_READ;
+	status = spi_write_then_read(spi, &addr, sizeof(addr), buf, 1);
+	if (status < 0) {
+		dev_err(&spi->dev, "control register read error %d\n",
+				status);
+		return status;
+	}
+
+	if ((buf[0] & ~RTC_CMD_WRITE_DISABLE) != 0) {
+		status = spi_write_then_read(spi, &addr, sizeof(addr), buf, 1);
+		if (status < 0) {
+			dev_err(&spi->dev, "control register read error %d\n",
+					status);
+			return status;
+		}
+
+		if ((buf[0] & ~RTC_CMD_WRITE_DISABLE) != 0) {
+			dev_err(&spi->dev, "junk in control register\n");
+			return -ENODEV;
+		}
+	}
+	if (buf[0] == 0) {
+		bp = buf;
+		*bp++ = RTC_ADDR_CTRL << 1 | RTC_CMD_WRITE;
+		*bp++ = RTC_CMD_WRITE_DISABLE;
+
+		status = spi_write_then_read(spi, buf, 2, NULL, 0);
+		if (status < 0) {
+			dev_err(&spi->dev, "control register write error %d\n",
+					status);
+			return status;
+		}
+
+		addr = RTC_ADDR_CTRL << 1 | RTC_CMD_READ;
+		status = spi_write_then_read(spi, &addr, sizeof(addr), buf, 1);
+		if (status < 0) {
+			dev_err(&spi->dev,
+					"error %d reading control register\n",
+					status);
+			return status;
+		}
+
+		if (buf[0] != RTC_CMD_WRITE_DISABLE) {
+			dev_err(&spi->dev, "failed to detect chip\n");
+			return -ENODEV;
+		}
+	}
+
+	spi_set_drvdata(spi, spi);
+
+	rtc = devm_rtc_device_register(&spi->dev, "ds1302",
+			&ds1302_rtc_ops, THIS_MODULE);
+	if (IS_ERR(rtc)) {
+		status = PTR_ERR(rtc);
+		dev_err(&spi->dev, "error %d registering rtc\n", status);
+		return status;
+	}
+
+	return 0;
+}
+
+#ifdef CONFIG_OF
+static const struct of_device_id ds1302_dt_ids[] = {
+	{ .compatible = "maxim,ds1302", },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, ds1302_dt_ids);
+#endif
+
+static const struct spi_device_id ds1302_spi_ids[] = {
+	{ .name = "ds1302", },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(spi, ds1302_spi_ids);
+
+static struct spi_driver ds1302_driver = {
+	.driver.name	= "rtc-ds1302",
+	.driver.of_match_table = of_match_ptr(ds1302_dt_ids),
+	.probe		= ds1302_probe,
+	.id_table	= ds1302_spi_ids,
+};
+
+module_spi_driver(ds1302_driver);
+
+MODULE_DESCRIPTION("Dallas DS1302 RTC driver");
+MODULE_AUTHOR("Paul Mundt, David McCullough");
+MODULE_LICENSE("GPL v2");