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, 204 insertions, 0 deletions

diff --git a/drivers/hid/hid-appletb-bl.c b/drivers/hid/hid-appletb-bl.c
new file mode 100644
index 000000000..bad2aead8
--- /dev/null
+++ b/drivers/hid/hid-appletb-bl.c
@@ -0,0 +1,204 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Apple Touch Bar Backlight Driver
+ *
+ * Copyright (c) 2017-2018 Ronald Tschalär
+ * Copyright (c) 2022-2023 Kerem Karabay <kekrby@gmail.com>
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/hid.h>
+#include <linux/backlight.h>
+#include <linux/device.h>
+
+#include "hid-ids.h"
+
+#define APPLETB_BL_ON			1
+#define APPLETB_BL_DIM			3
+#define APPLETB_BL_OFF			4
+
+#define HID_UP_APPLEVENDOR_TB_BL	0xff120000
+
+#define HID_VD_APPLE_TB_BRIGHTNESS	0xff120001
+#define HID_USAGE_AUX1			0xff120020
+#define HID_USAGE_BRIGHTNESS		0xff120021
+
+static int appletb_bl_def_brightness = 2;
+module_param_named(brightness, appletb_bl_def_brightness, int, 0444);
+MODULE_PARM_DESC(brightness, "Default brightness:\n"
+			 "    0 - Touchbar is off\n"
+			 "    1 - Dim brightness\n"
+			 "    [2] - Full brightness");
+
+struct appletb_bl {
+	struct hid_field *aux1_field, *brightness_field;
+	struct backlight_device *bdev;
+
+	bool full_on;
+};
+
+static const u8 appletb_bl_brightness_map[] = {
+	APPLETB_BL_OFF,
+	APPLETB_BL_DIM,
+	APPLETB_BL_ON,
+};
+
+static int appletb_bl_set_brightness(struct appletb_bl *bl, u8 brightness)
+{
+	struct hid_report *report = bl->brightness_field->report;
+	struct hid_device *hdev = report->device;
+	int ret;
+
+	ret = hid_set_field(bl->aux1_field, 0, 1);
+	if (ret) {
+		hid_err(hdev, "Failed to set auxiliary field (%pe)\n", ERR_PTR(ret));
+		return ret;
+	}
+
+	ret = hid_set_field(bl->brightness_field, 0, brightness);
+	if (ret) {
+		hid_err(hdev, "Failed to set brightness field (%pe)\n", ERR_PTR(ret));
+		return ret;
+	}
+
+	if (!bl->full_on) {
+		ret = hid_hw_power(hdev, PM_HINT_FULLON);
+		if (ret < 0) {
+			hid_err(hdev, "Device didn't power on (%pe)\n", ERR_PTR(ret));
+			return ret;
+		}
+
+		bl->full_on = true;
+	}
+
+	hid_hw_request(hdev, report, HID_REQ_SET_REPORT);
+
+	if (brightness == APPLETB_BL_OFF) {
+		hid_hw_power(hdev, PM_HINT_NORMAL);
+		bl->full_on = false;
+	}
+
+	return 0;
+}
+
+static int appletb_bl_update_status(struct backlight_device *bdev)
+{
+	struct appletb_bl *bl = bl_get_data(bdev);
+	u8 brightness;
+
+	if (backlight_is_blank(bdev))
+		brightness = APPLETB_BL_OFF;
+	else
+		brightness = appletb_bl_brightness_map[backlight_get_brightness(bdev)];
+
+	return appletb_bl_set_brightness(bl, brightness);
+}
+
+static const struct backlight_ops appletb_bl_backlight_ops = {
+	.options = BL_CORE_SUSPENDRESUME,
+	.update_status = appletb_bl_update_status,
+};
+
+static int appletb_bl_probe(struct hid_device *hdev, const struct hid_device_id *id)
+{
+	struct hid_field *aux1_field, *brightness_field;
+	struct backlight_properties bl_props = { 0 };
+	struct device *dev = &hdev->dev;
+	struct appletb_bl *bl;
+	int ret;
+
+	ret = hid_parse(hdev);
+	if (ret)
+		return dev_err_probe(dev, ret, "HID parse failed\n");
+
+	aux1_field = hid_find_field(hdev, HID_FEATURE_REPORT,
+				    HID_VD_APPLE_TB_BRIGHTNESS, HID_USAGE_AUX1);
+
+	brightness_field = hid_find_field(hdev, HID_FEATURE_REPORT,
+					  HID_VD_APPLE_TB_BRIGHTNESS, HID_USAGE_BRIGHTNESS);
+
+	if (!aux1_field || !brightness_field)
+		return -ENODEV;
+
+	if (aux1_field->report != brightness_field->report)
+		return dev_err_probe(dev, -ENODEV, "Encountered unexpected report structure\n");
+
+	bl = devm_kzalloc(dev, sizeof(*bl), GFP_KERNEL);
+	if (!bl)
+		return -ENOMEM;
+
+	ret = hid_hw_start(hdev, HID_CONNECT_DRIVER);
+	if (ret)
+		return dev_err_probe(dev, ret, "HID hardware start failed\n");
+
+	ret = hid_hw_open(hdev);
+	if (ret) {
+		dev_err_probe(dev, ret, "HID hardware open failed\n");
+		goto stop_hw;
+	}
+
+	bl->aux1_field = aux1_field;
+	bl->brightness_field = brightness_field;
+
+	ret = appletb_bl_set_brightness(bl,
+		appletb_bl_brightness_map[(appletb_bl_def_brightness > 2) ? 2 : appletb_bl_def_brightness]);
+
+	if (ret) {
+		dev_err_probe(dev, ret, "Failed to set default touch bar brightness to %d\n",
+			      appletb_bl_def_brightness);
+		goto close_hw;
+	}
+
+	bl_props.type = BACKLIGHT_RAW;
+	bl_props.max_brightness = ARRAY_SIZE(appletb_bl_brightness_map) - 1;
+
+	bl->bdev = devm_backlight_device_register(dev, "appletb_backlight", dev, bl,
+						  &appletb_bl_backlight_ops, &bl_props);
+	if (IS_ERR(bl->bdev)) {
+		ret = PTR_ERR(bl->bdev);
+		dev_err_probe(dev, ret, "Failed to register backlight device\n");
+		goto close_hw;
+	}
+
+	hid_set_drvdata(hdev, bl);
+
+	return 0;
+
+close_hw:
+	hid_hw_close(hdev);
+stop_hw:
+	hid_hw_stop(hdev);
+
+	return ret;
+}
+
+static void appletb_bl_remove(struct hid_device *hdev)
+{
+	struct appletb_bl *bl = hid_get_drvdata(hdev);
+
+	appletb_bl_set_brightness(bl, APPLETB_BL_OFF);
+
+	hid_hw_close(hdev);
+	hid_hw_stop(hdev);
+}
+
+static const struct hid_device_id appletb_bl_hid_ids[] = {
+	/* MacBook Pro's 2018, 2019, with T2 chip: iBridge DFR Brightness */
+	{ HID_USB_DEVICE(USB_VENDOR_ID_APPLE, USB_DEVICE_ID_APPLE_TOUCHBAR_BACKLIGHT) },
+	{ }
+};
+MODULE_DEVICE_TABLE(hid, appletb_bl_hid_ids);
+
+static struct hid_driver appletb_bl_hid_driver = {
+	.name = "hid-appletb-bl",
+	.id_table = appletb_bl_hid_ids,
+	.probe = appletb_bl_probe,
+	.remove = appletb_bl_remove,
+};
+module_hid_driver(appletb_bl_hid_driver);
+
+MODULE_AUTHOR("Ronald Tschalär");
+MODULE_AUTHOR("Kerem Karabay <kekrby@gmail.com>");
+MODULE_DESCRIPTION("MacBook Pro Touch Bar Backlight driver");
+MODULE_LICENSE("GPL");