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, 231 insertions, 0 deletions

diff --git a/drivers/input/joystick/fsia6b.c b/drivers/input/joystick/fsia6b.c
new file mode 100644
index 000000000..b0d736484
--- /dev/null
+++ b/drivers/input/joystick/fsia6b.c
@@ -0,0 +1,231 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * FS-iA6B iBus RC receiver driver
+ *
+ * This driver provides all 14 channels of the FlySky FS-ia6B RC receiver
+ * as analog values.
+ *
+ * Additionally, the channels can be converted to discrete switch values.
+ * By default, it is configured for the offical FS-i6 remote control.
+ * If you use a different hardware configuration, you can configure it
+ * using the `switch_config` parameter.
+ */
+
+#include <linux/device.h>
+#include <linux/input.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/serio.h>
+#include <linux/slab.h>
+#include <linux/types.h>
+
+#define DRIVER_DESC		"FS-iA6B iBus RC receiver"
+
+MODULE_AUTHOR("Markus Koch <markus@notsyncing.net>");
+MODULE_DESCRIPTION(DRIVER_DESC);
+MODULE_LICENSE("GPL");
+
+#define IBUS_SERVO_COUNT	14
+
+static char *switch_config = "00000022320000";
+module_param(switch_config, charp, 0444);
+MODULE_PARM_DESC(switch_config,
+		 "Amount of switch positions per channel (14 characters, 0-3)");
+
+static int fsia6b_axes[IBUS_SERVO_COUNT] = {
+	ABS_X, ABS_Y,
+	ABS_Z, ABS_RX,
+	ABS_RY, ABS_RZ,
+	ABS_HAT0X, ABS_HAT0Y,
+	ABS_HAT1X, ABS_HAT1Y,
+	ABS_HAT2X, ABS_HAT2Y,
+	ABS_HAT3X, ABS_HAT3Y
+};
+
+enum ibus_state { SYNC, COLLECT, PROCESS };
+
+struct ibus_packet {
+	enum ibus_state state;
+
+	int offset;
+	u16 ibuf;
+	u16 channel[IBUS_SERVO_COUNT];
+};
+
+struct fsia6b {
+	struct input_dev *dev;
+	struct ibus_packet packet;
+
+	char phys[32];
+};
+
+static irqreturn_t fsia6b_serio_irq(struct serio *serio,
+				    unsigned char data, unsigned int flags)
+{
+	struct fsia6b *fsia6b = serio_get_drvdata(serio);
+	int i;
+	int sw_state;
+	int sw_id = BTN_0;
+
+	fsia6b->packet.ibuf = (data << 8) | ((fsia6b->packet.ibuf >> 8) & 0xFF);
+
+	switch (fsia6b->packet.state) {
+	case SYNC:
+		if (fsia6b->packet.ibuf == 0x4020)
+			fsia6b->packet.state = COLLECT;
+		break;
+
+	case COLLECT:
+		fsia6b->packet.state = PROCESS;
+		break;
+
+	case PROCESS:
+		fsia6b->packet.channel[fsia6b->packet.offset] =
+				fsia6b->packet.ibuf;
+		fsia6b->packet.offset++;
+
+		if (fsia6b->packet.offset == IBUS_SERVO_COUNT) {
+			fsia6b->packet.offset = 0;
+			fsia6b->packet.state = SYNC;
+			for (i = 0; i < IBUS_SERVO_COUNT; ++i) {
+				input_report_abs(fsia6b->dev, fsia6b_axes[i],
+						 fsia6b->packet.channel[i]);
+
+				sw_state = 0;
+				if (fsia6b->packet.channel[i] > 1900)
+					sw_state = 1;
+				else if (fsia6b->packet.channel[i] < 1100)
+					sw_state = 2;
+
+				switch (switch_config[i]) {
+				case '3':
+					input_report_key(fsia6b->dev,
+							 sw_id++,
+							 sw_state == 0);
+					fallthrough;
+				case '2':
+					input_report_key(fsia6b->dev,
+							 sw_id++,
+							 sw_state == 1);
+					fallthrough;
+				case '1':
+					input_report_key(fsia6b->dev,
+							 sw_id++,
+							 sw_state == 2);
+				}
+			}
+			input_sync(fsia6b->dev);
+		} else {
+			fsia6b->packet.state = COLLECT;
+		}
+		break;
+	}
+
+	return IRQ_HANDLED;
+}
+
+static int fsia6b_serio_connect(struct serio *serio, struct serio_driver *drv)
+{
+	struct fsia6b *fsia6b;
+	struct input_dev *input_dev;
+	int err;
+	int i, j;
+	int sw_id = 0;
+
+	fsia6b = kzalloc_obj(*fsia6b);
+	if (!fsia6b)
+		return -ENOMEM;
+
+	fsia6b->packet.ibuf = 0;
+	fsia6b->packet.offset = 0;
+	fsia6b->packet.state = SYNC;
+
+	serio_set_drvdata(serio, fsia6b);
+
+	input_dev = input_allocate_device();
+	if (!input_dev) {
+		err = -ENOMEM;
+		goto fail1;
+	}
+	fsia6b->dev = input_dev;
+
+	scnprintf(fsia6b->phys, sizeof(fsia6b->phys), "%s/input0", serio->phys);
+
+	input_dev->name = DRIVER_DESC;
+	input_dev->phys = fsia6b->phys;
+	input_dev->id.bustype = BUS_RS232;
+	input_dev->id.vendor = SERIO_FSIA6B;
+	input_dev->id.product = serio->id.id;
+	input_dev->id.version = 0x0100;
+	input_dev->dev.parent = &serio->dev;
+
+	for (i = 0; i < IBUS_SERVO_COUNT; i++)
+		input_set_abs_params(input_dev, fsia6b_axes[i],
+				     1000, 2000, 2, 2);
+
+	/* Register switch configuration */
+	for (i = 0; i < IBUS_SERVO_COUNT; i++) {
+		if (switch_config[i] < '0' || switch_config[i] > '3') {
+			dev_err(&fsia6b->dev->dev,
+				"Invalid switch configuration supplied for fsia6b.\n");
+			err = -EINVAL;
+			goto fail2;
+		}
+
+		for (j = '1'; j <= switch_config[i]; j++) {
+			input_set_capability(input_dev, EV_KEY, BTN_0 + sw_id);
+			sw_id++;
+		}
+	}
+
+	err = serio_open(serio, drv);
+	if (err)
+		goto fail2;
+
+	err = input_register_device(fsia6b->dev);
+	if (err)
+		goto fail3;
+
+	return 0;
+
+fail3:	serio_close(serio);
+fail2:	input_free_device(input_dev);
+fail1:	serio_set_drvdata(serio, NULL);
+	kfree(fsia6b);
+	return err;
+}
+
+static void fsia6b_serio_disconnect(struct serio *serio)
+{
+	struct fsia6b *fsia6b = serio_get_drvdata(serio);
+
+	serio_close(serio);
+	serio_set_drvdata(serio, NULL);
+	input_unregister_device(fsia6b->dev);
+	kfree(fsia6b);
+}
+
+static const struct serio_device_id fsia6b_serio_ids[] = {
+	{
+		.type	= SERIO_RS232,
+		.proto	= SERIO_FSIA6B,
+		.id	= SERIO_ANY,
+		.extra	= SERIO_ANY,
+	},
+	{ 0 }
+};
+
+MODULE_DEVICE_TABLE(serio, fsia6b_serio_ids);
+
+static struct serio_driver fsia6b_serio_drv = {
+	.driver		= {
+		.name	= "fsia6b"
+	},
+	.description	= DRIVER_DESC,
+	.id_table	= fsia6b_serio_ids,
+	.interrupt	= fsia6b_serio_irq,
+	.connect	= fsia6b_serio_connect,
+	.disconnect	= fsia6b_serio_disconnect
+};
+
+module_serio_driver(fsia6b_serio_drv)