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, 217 insertions, 0 deletions

diff --git a/drivers/hwmon/lm70.c b/drivers/hwmon/lm70.c
new file mode 100644
index 000000000..8b525725f
--- /dev/null
+++ b/drivers/hwmon/lm70.c
@@ -0,0 +1,217 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * lm70.c
+ *
+ * The LM70 is a temperature sensor chip from National Semiconductor (NS).
+ * Copyright (C) 2006 Kaiwan N Billimoria <kaiwan@designergraphix.com>
+ *
+ * The LM70 communicates with a host processor via an SPI/Microwire Bus
+ * interface. The complete datasheet is available at TI's website
+ * here:
+ * https://www.ti.com/product/LM70
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/device.h>
+#include <linux/err.h>
+#include <linux/sysfs.h>
+#include <linux/hwmon.h>
+#include <linux/mutex.h>
+#include <linux/of.h>
+#include <linux/property.h>
+#include <linux/spi/spi.h>
+#include <linux/slab.h>
+
+#define DRVNAME		"lm70"
+
+#define LM70_CHIP_LM70		0	/* original NS LM70 */
+#define LM70_CHIP_TMP121	1	/* TI TMP121/TMP123 */
+#define LM70_CHIP_LM71		2	/* NS LM71 */
+#define LM70_CHIP_LM74		3	/* NS LM74 */
+#define LM70_CHIP_TMP122	4	/* TI TMP122/TMP124 */
+#define LM70_CHIP_TMP125	5	/* TI TMP125 */
+
+struct lm70 {
+	struct spi_device *spi;
+	struct mutex lock;
+	unsigned int chip;
+};
+
+/* sysfs hook function */
+static ssize_t temp1_input_show(struct device *dev,
+				struct device_attribute *attr, char *buf)
+{
+	struct lm70 *p_lm70 = dev_get_drvdata(dev);
+	struct spi_device *spi = p_lm70->spi;
+	int status, val = 0;
+	u8 rxbuf[2];
+	s16 raw = 0;
+
+	if (mutex_lock_interruptible(&p_lm70->lock))
+		return -ERESTARTSYS;
+
+	/*
+	 * spi_read() requires a DMA-safe buffer; so we use
+	 * spi_write_then_read(), transmitting 0 bytes.
+	 */
+	status = spi_write_then_read(spi, NULL, 0, &rxbuf[0], 2);
+	if (status < 0) {
+		dev_warn(dev, "spi_write_then_read failed with status %d\n",
+			 status);
+		goto out;
+	}
+	raw = (rxbuf[0] << 8) + rxbuf[1];
+	dev_dbg(dev, "rxbuf[0] : 0x%02x rxbuf[1] : 0x%02x raw=0x%04x\n",
+		rxbuf[0], rxbuf[1], raw);
+
+	/*
+	 * LM70:
+	 * The "raw" temperature read into rxbuf[] is a 16-bit signed 2's
+	 * complement value. Only the MSB 11 bits (1 sign + 10 temperature
+	 * bits) are meaningful; the LSB 5 bits are to be discarded.
+	 * See the datasheet.
+	 *
+	 * Further, each bit represents 0.25 degrees Celsius; so, multiply
+	 * by 0.25. Also multiply by 1000 to represent in millidegrees
+	 * Celsius.
+	 * So it's equivalent to multiplying by 0.25 * 1000 = 250.
+	 *
+	 * LM74 and TMP121/TMP122/TMP123/TMP124:
+	 * 13 bits of 2's complement data, discard LSB 3 bits,
+	 * resolution 0.0625 degrees celsius.
+	 *
+	 * LM71:
+	 * 14 bits of 2's complement data, discard LSB 2 bits,
+	 * resolution 0.0312 degrees celsius.
+	 *
+	 * TMP125:
+	 * MSB/D15 is a leading zero. D14 is the sign-bit. This is
+	 * followed by 9 temperature bits (D13..D5) in 2's complement
+	 * data format with a resolution of 0.25 degrees celsius per unit.
+	 * LSB 5 bits (D4..D0) share the same value as D5 and get discarded.
+	 */
+	switch (p_lm70->chip) {
+	case LM70_CHIP_LM70:
+		val = ((int)raw / 32) * 250;
+		break;
+
+	case LM70_CHIP_TMP121:
+	case LM70_CHIP_TMP122:
+	case LM70_CHIP_LM74:
+		val = ((int)raw / 8) * 625 / 10;
+		break;
+
+	case LM70_CHIP_LM71:
+		val = ((int)raw / 4) * 3125 / 100;
+		break;
+
+	case LM70_CHIP_TMP125:
+		val = (sign_extend32(raw, 14) / 32) * 250;
+		break;
+	}
+
+	status = sprintf(buf, "%d\n", val); /* millidegrees Celsius */
+out:
+	mutex_unlock(&p_lm70->lock);
+	return status;
+}
+
+static DEVICE_ATTR_RO(temp1_input);
+
+static struct attribute *lm70_attrs[] = {
+	&dev_attr_temp1_input.attr,
+	NULL
+};
+
+ATTRIBUTE_GROUPS(lm70);
+
+/*----------------------------------------------------------------------*/
+
+#ifdef CONFIG_OF
+static const struct of_device_id lm70_of_ids[] = {
+	{
+		.compatible = "ti,lm70",
+		.data = (void *) LM70_CHIP_LM70,
+	},
+	{
+		.compatible = "ti,tmp121",
+		.data = (void *) LM70_CHIP_TMP121,
+	},
+	{
+		.compatible = "ti,tmp122",
+		.data = (void *) LM70_CHIP_TMP122,
+	},
+	{
+		.compatible = "ti,tmp125",
+		.data = (void *) LM70_CHIP_TMP125,
+	},
+	{
+		.compatible = "ti,lm71",
+		.data = (void *) LM70_CHIP_LM71,
+	},
+	{
+		.compatible = "ti,lm74",
+		.data = (void *) LM70_CHIP_LM74,
+	},
+	{},
+};
+MODULE_DEVICE_TABLE(of, lm70_of_ids);
+#endif
+
+static int lm70_probe(struct spi_device *spi)
+{
+	struct device *hwmon_dev;
+	struct lm70 *p_lm70;
+	int chip;
+
+	chip = (kernel_ulong_t)spi_get_device_match_data(spi);
+
+	/* signaling is SPI_MODE_0 */
+	if ((spi->mode & SPI_MODE_X_MASK) != SPI_MODE_0)
+		return -EINVAL;
+
+	/* NOTE:  we assume 8-bit words, and convert to 16 bits manually */
+
+	p_lm70 = devm_kzalloc(&spi->dev, sizeof(*p_lm70), GFP_KERNEL);
+	if (!p_lm70)
+		return -ENOMEM;
+
+	mutex_init(&p_lm70->lock);
+	p_lm70->chip = chip;
+	p_lm70->spi = spi;
+
+	hwmon_dev = devm_hwmon_device_register_with_groups(&spi->dev,
+							   spi->modalias,
+							   p_lm70, lm70_groups);
+	return PTR_ERR_OR_ZERO(hwmon_dev);
+}
+
+static const struct spi_device_id lm70_ids[] = {
+	{ "lm70",   LM70_CHIP_LM70 },
+	{ "tmp121", LM70_CHIP_TMP121 },
+	{ "tmp122", LM70_CHIP_TMP122 },
+	{ "tmp125", LM70_CHIP_TMP125 },
+	{ "lm71",   LM70_CHIP_LM71 },
+	{ "lm74",   LM70_CHIP_LM74 },
+	{ },
+};
+MODULE_DEVICE_TABLE(spi, lm70_ids);
+
+static struct spi_driver lm70_driver = {
+	.driver = {
+		.name	= "lm70",
+		.of_match_table	= of_match_ptr(lm70_of_ids),
+	},
+	.id_table = lm70_ids,
+	.probe	= lm70_probe,
+};
+
+module_spi_driver(lm70_driver);
+
+MODULE_AUTHOR("Kaiwan N Billimoria");
+MODULE_DESCRIPTION("NS LM70 and compatibles Linux driver");
+MODULE_LICENSE("GPL");