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, 235 insertions, 0 deletions

diff --git a/drivers/hwmon/surface_temp.c b/drivers/hwmon/surface_temp.c
new file mode 100644
index 000000000..cd21f331f
--- /dev/null
+++ b/drivers/hwmon/surface_temp.c
@@ -0,0 +1,235 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Thermal sensor subsystem driver for Surface System Aggregator Module (SSAM).
+ *
+ * Copyright (C) 2022-2023 Maximilian Luz <luzmaximilian@gmail.com>
+ */
+
+#include <linux/bitops.h>
+#include <linux/hwmon.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/types.h>
+
+#include <linux/surface_aggregator/controller.h>
+#include <linux/surface_aggregator/device.h>
+
+/* -- SAM interface. -------------------------------------------------------- */
+
+/*
+ * Available sensors are indicated by a 16-bit bitfield, where a 1 marks the
+ * presence of a sensor. So we have at most 16 possible sensors/channels.
+ */
+#define SSAM_TMP_SENSOR_MAX_COUNT	16
+
+/*
+ * All names observed so far are 6 characters long, but there's only
+ * zeros after the name, so perhaps they can be longer. This number reflects
+ * the maximum zero-padded space observed in the returned buffer.
+ */
+#define SSAM_TMP_SENSOR_NAME_LENGTH	18
+
+struct ssam_tmp_get_name_rsp {
+	__le16 unknown1;
+	char unknown2;
+	char name[SSAM_TMP_SENSOR_NAME_LENGTH];
+} __packed;
+
+static_assert(sizeof(struct ssam_tmp_get_name_rsp) == 21);
+
+SSAM_DEFINE_SYNC_REQUEST_CL_R(__ssam_tmp_get_available_sensors, __le16, {
+	.target_category = SSAM_SSH_TC_TMP,
+	.command_id      = 0x04,
+});
+
+SSAM_DEFINE_SYNC_REQUEST_MD_R(__ssam_tmp_get_temperature, __le16, {
+	.target_category = SSAM_SSH_TC_TMP,
+	.command_id      = 0x01,
+});
+
+SSAM_DEFINE_SYNC_REQUEST_MD_R(__ssam_tmp_get_name, struct ssam_tmp_get_name_rsp, {
+	.target_category = SSAM_SSH_TC_TMP,
+	.command_id      = 0x0e,
+});
+
+static int ssam_tmp_get_available_sensors(struct ssam_device *sdev, s16 *sensors)
+{
+	__le16 sensors_le;
+	int status;
+
+	status = __ssam_tmp_get_available_sensors(sdev, &sensors_le);
+	if (status)
+		return status;
+
+	*sensors = le16_to_cpu(sensors_le);
+	return 0;
+}
+
+static int ssam_tmp_get_temperature(struct ssam_device *sdev, u8 iid, long *temperature)
+{
+	__le16 temp_le;
+	int status;
+
+	status = __ssam_tmp_get_temperature(sdev->ctrl, sdev->uid.target, iid, &temp_le);
+	if (status)
+		return status;
+
+	/* Convert 1/10 °K to 1/1000 °C */
+	*temperature = (le16_to_cpu(temp_le) - 2731) * 100L;
+	return 0;
+}
+
+static int ssam_tmp_get_name(struct ssam_device *sdev, u8 iid, char *buf, size_t buf_len)
+{
+	struct ssam_tmp_get_name_rsp name_rsp;
+	int status;
+
+	status =  __ssam_tmp_get_name(sdev->ctrl, sdev->uid.target, iid, &name_rsp);
+	if (status)
+		return status;
+
+	/*
+	 * This should not fail unless the name in the returned struct is not
+	 * null-terminated or someone changed something in the struct
+	 * definitions above, since our buffer and struct have the same
+	 * capacity by design. So if this fails, log an error message. Since
+	 * the more likely cause is that the returned string isn't
+	 * null-terminated, we might have received garbage (as opposed to just
+	 * an incomplete string), so also fail the function.
+	 */
+	status = strscpy(buf, name_rsp.name, buf_len);
+	if (status < 0) {
+		dev_err(&sdev->dev, "received non-null-terminated sensor name string\n");
+		return status;
+	}
+
+	return 0;
+}
+
+/* -- Driver.---------------------------------------------------------------- */
+
+struct ssam_temp {
+	struct ssam_device *sdev;
+	s16 sensors;
+	char names[SSAM_TMP_SENSOR_MAX_COUNT][SSAM_TMP_SENSOR_NAME_LENGTH];
+};
+
+static umode_t ssam_temp_hwmon_is_visible(const void *data,
+					  enum hwmon_sensor_types type,
+					  u32 attr, int channel)
+{
+	const struct ssam_temp *ssam_temp = data;
+
+	if (!(ssam_temp->sensors & BIT(channel)))
+		return 0;
+
+	return 0444;
+}
+
+static int ssam_temp_hwmon_read(struct device *dev,
+				enum hwmon_sensor_types type,
+				u32 attr, int channel, long *value)
+{
+	const struct ssam_temp *ssam_temp = dev_get_drvdata(dev);
+
+	return ssam_tmp_get_temperature(ssam_temp->sdev, channel + 1, value);
+}
+
+static int ssam_temp_hwmon_read_string(struct device *dev,
+				       enum hwmon_sensor_types type,
+				       u32 attr, int channel, const char **str)
+{
+	const struct ssam_temp *ssam_temp = dev_get_drvdata(dev);
+
+	*str = ssam_temp->names[channel];
+	return 0;
+}
+
+static const struct hwmon_channel_info * const ssam_temp_hwmon_info[] = {
+	HWMON_CHANNEL_INFO(chip,
+			   HWMON_C_REGISTER_TZ),
+	HWMON_CHANNEL_INFO(temp,
+			   HWMON_T_INPUT | HWMON_T_LABEL,
+			   HWMON_T_INPUT | HWMON_T_LABEL,
+			   HWMON_T_INPUT | HWMON_T_LABEL,
+			   HWMON_T_INPUT | HWMON_T_LABEL,
+			   HWMON_T_INPUT | HWMON_T_LABEL,
+			   HWMON_T_INPUT | HWMON_T_LABEL,
+			   HWMON_T_INPUT | HWMON_T_LABEL,
+			   HWMON_T_INPUT | HWMON_T_LABEL,
+			   HWMON_T_INPUT | HWMON_T_LABEL,
+			   HWMON_T_INPUT | HWMON_T_LABEL,
+			   HWMON_T_INPUT | HWMON_T_LABEL,
+			   HWMON_T_INPUT | HWMON_T_LABEL,
+			   HWMON_T_INPUT | HWMON_T_LABEL,
+			   HWMON_T_INPUT | HWMON_T_LABEL,
+			   HWMON_T_INPUT | HWMON_T_LABEL,
+			   HWMON_T_INPUT | HWMON_T_LABEL),
+	NULL
+};
+
+static const struct hwmon_ops ssam_temp_hwmon_ops = {
+	.is_visible = ssam_temp_hwmon_is_visible,
+	.read = ssam_temp_hwmon_read,
+	.read_string = ssam_temp_hwmon_read_string,
+};
+
+static const struct hwmon_chip_info ssam_temp_hwmon_chip_info = {
+	.ops = &ssam_temp_hwmon_ops,
+	.info = ssam_temp_hwmon_info,
+};
+
+static int ssam_temp_probe(struct ssam_device *sdev)
+{
+	struct ssam_temp *ssam_temp;
+	struct device *hwmon_dev;
+	s16 sensors;
+	int channel;
+	int status;
+
+	status = ssam_tmp_get_available_sensors(sdev, &sensors);
+	if (status)
+		return status;
+
+	ssam_temp = devm_kzalloc(&sdev->dev, sizeof(*ssam_temp), GFP_KERNEL);
+	if (!ssam_temp)
+		return -ENOMEM;
+
+	ssam_temp->sdev = sdev;
+	ssam_temp->sensors = sensors;
+
+	/* Retrieve the name for each available sensor. */
+	for (channel = 0; channel < SSAM_TMP_SENSOR_MAX_COUNT; channel++) {
+		if (!(sensors & BIT(channel)))
+			continue;
+
+		status = ssam_tmp_get_name(sdev, channel + 1, ssam_temp->names[channel],
+					   SSAM_TMP_SENSOR_NAME_LENGTH);
+		if (status)
+			return status;
+	}
+
+	hwmon_dev = devm_hwmon_device_register_with_info(&sdev->dev, "surface_thermal", ssam_temp,
+							 &ssam_temp_hwmon_chip_info, NULL);
+	return PTR_ERR_OR_ZERO(hwmon_dev);
+}
+
+static const struct ssam_device_id ssam_temp_match[] = {
+	{ SSAM_SDEV(TMP, SAM, 0x00, 0x02) },
+	{ },
+};
+MODULE_DEVICE_TABLE(ssam, ssam_temp_match);
+
+static struct ssam_device_driver ssam_temp = {
+	.probe = ssam_temp_probe,
+	.match_table = ssam_temp_match,
+	.driver = {
+		.name = "surface_temp",
+		.probe_type = PROBE_PREFER_ASYNCHRONOUS,
+	},
+};
+module_ssam_device_driver(ssam_temp);
+
+MODULE_AUTHOR("Maximilian Luz <luzmaximilian@gmail.com>");
+MODULE_DESCRIPTION("Thermal sensor subsystem driver for Surface System Aggregator Module");
+MODULE_LICENSE("GPL");