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, 183 insertions, 0 deletions

diff --git a/drivers/rtc/rtc-ds1347.c b/drivers/rtc/rtc-ds1347.c
new file mode 100644
index 000000000..a40c1a52d
--- /dev/null
+++ b/drivers/rtc/rtc-ds1347.c
@@ -0,0 +1,183 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/* rtc-ds1347.c
+ *
+ * Driver for Dallas Semiconductor DS1347 Low Current, SPI Compatible
+ * Real Time Clock
+ *
+ * Author : Raghavendra Chandra Ganiga <ravi23ganiga@gmail.com>
+ */
+
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/device.h>
+#include <linux/platform_device.h>
+#include <linux/rtc.h>
+#include <linux/spi/spi.h>
+#include <linux/bcd.h>
+#include <linux/regmap.h>
+
+/* Registers in ds1347 rtc */
+
+#define DS1347_SECONDS_REG	0x01
+#define DS1347_MINUTES_REG	0x03
+#define DS1347_HOURS_REG	0x05
+#define DS1347_DATE_REG		0x07
+#define DS1347_MONTH_REG	0x09
+#define DS1347_DAY_REG		0x0B
+#define DS1347_YEAR_REG		0x0D
+#define DS1347_CONTROL_REG	0x0F
+#define DS1347_CENTURY_REG	0x13
+#define DS1347_STATUS_REG	0x17
+#define DS1347_CLOCK_BURST	0x3F
+
+#define DS1347_WP_BIT		BIT(7)
+
+#define DS1347_NEOSC_BIT	BIT(7)
+#define DS1347_OSF_BIT		BIT(2)
+
+static const struct regmap_range ds1347_ranges[] = {
+	{
+		.range_min = DS1347_SECONDS_REG,
+		.range_max = DS1347_STATUS_REG,
+	},
+};
+
+static const struct regmap_access_table ds1347_access_table = {
+	.yes_ranges = ds1347_ranges,
+	.n_yes_ranges = ARRAY_SIZE(ds1347_ranges),
+};
+
+static int ds1347_read_time(struct device *dev, struct rtc_time *dt)
+{
+	struct regmap *map = dev_get_drvdata(dev);
+	unsigned int status, century, secs;
+	unsigned char buf[8];
+	int err;
+
+	err = regmap_read(map, DS1347_STATUS_REG, &status);
+	if (err)
+		return err;
+
+	if (status & DS1347_OSF_BIT)
+		return -EINVAL;
+
+	do {
+		err = regmap_bulk_read(map, DS1347_CLOCK_BURST, buf, 8);
+		if (err)
+			return err;
+
+		err = regmap_read(map, DS1347_CENTURY_REG, &century);
+		if (err)
+			return err;
+
+		err = regmap_read(map, DS1347_SECONDS_REG, &secs);
+		if (err)
+			return err;
+	} while (buf[0] != secs);
+
+	dt->tm_sec = bcd2bin(buf[0]);
+	dt->tm_min = bcd2bin(buf[1] & 0x7f);
+	dt->tm_hour = bcd2bin(buf[2] & 0x3F);
+	dt->tm_mday = bcd2bin(buf[3]);
+	dt->tm_mon = bcd2bin(buf[4]) - 1;
+	dt->tm_wday = bcd2bin(buf[5]) - 1;
+	dt->tm_year = (bcd2bin(century) * 100) + bcd2bin(buf[6]) - 1900;
+
+	return 0;
+}
+
+static int ds1347_set_time(struct device *dev, struct rtc_time *dt)
+{
+	struct regmap *map = dev_get_drvdata(dev);
+	unsigned int century;
+	unsigned char buf[8];
+	int err;
+
+	err = regmap_update_bits(map, DS1347_STATUS_REG,
+				 DS1347_NEOSC_BIT, DS1347_NEOSC_BIT);
+	if (err)
+		return err;
+
+	buf[0] = bin2bcd(dt->tm_sec);
+	buf[1] = bin2bcd(dt->tm_min);
+	buf[2] = (bin2bcd(dt->tm_hour) & 0x3F);
+	buf[3] = bin2bcd(dt->tm_mday);
+	buf[4] = bin2bcd(dt->tm_mon + 1);
+	buf[5] = bin2bcd(dt->tm_wday + 1);
+	buf[6] = bin2bcd(dt->tm_year % 100);
+	buf[7] = bin2bcd(0x00);
+
+	err = regmap_bulk_write(map, DS1347_CLOCK_BURST, buf, 8);
+	if (err)
+		return err;
+
+	century = (dt->tm_year / 100) + 19;
+	err = regmap_write(map, DS1347_CENTURY_REG, bin2bcd(century));
+	if (err)
+		return err;
+
+	return regmap_update_bits(map, DS1347_STATUS_REG,
+				  DS1347_NEOSC_BIT | DS1347_OSF_BIT, 0);
+}
+
+static const struct rtc_class_ops ds1347_rtc_ops = {
+	.read_time = ds1347_read_time,
+	.set_time = ds1347_set_time,
+};
+
+static int ds1347_probe(struct spi_device *spi)
+{
+	struct rtc_device *rtc;
+	struct regmap_config config;
+	struct regmap *map;
+	int err;
+
+	memset(&config, 0, sizeof(config));
+	config.reg_bits = 8;
+	config.val_bits = 8;
+	config.read_flag_mask = 0x80;
+	config.max_register = 0x3F;
+	config.wr_table = &ds1347_access_table;
+
+	/* spi setup with ds1347 in mode 3 and bits per word as 8 */
+	spi->mode = SPI_MODE_3;
+	spi->bits_per_word = 8;
+	spi_setup(spi);
+
+	map = devm_regmap_init_spi(spi, &config);
+
+	if (IS_ERR(map)) {
+		dev_err(&spi->dev, "ds1347 regmap init spi failed\n");
+		return PTR_ERR(map);
+	}
+
+	spi_set_drvdata(spi, map);
+
+	/* Disable the write protect of rtc */
+	err = regmap_update_bits(map, DS1347_CONTROL_REG, DS1347_WP_BIT, 0);
+	if (err)
+		return err;
+
+	rtc = devm_rtc_allocate_device(&spi->dev);
+	if (IS_ERR(rtc))
+		return PTR_ERR(rtc);
+
+	rtc->ops = &ds1347_rtc_ops;
+	rtc->range_min = RTC_TIMESTAMP_BEGIN_0000;
+	rtc->range_max = RTC_TIMESTAMP_END_9999;
+
+	return devm_rtc_register_device(rtc);
+}
+
+static struct spi_driver ds1347_driver = {
+	.driver = {
+		.name = "ds1347",
+	},
+	.probe = ds1347_probe,
+};
+
+module_spi_driver(ds1347_driver);
+
+MODULE_DESCRIPTION("DS1347 SPI RTC DRIVER");
+MODULE_AUTHOR("Raghavendra C Ganiga <ravi23ganiga@gmail.com>");
+MODULE_LICENSE("GPL v2");