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, 376 insertions, 0 deletions

diff --git a/sound/drivers/serial-generic.c b/sound/drivers/serial-generic.c
new file mode 100644
index 000000000..766206c6c
--- /dev/null
+++ b/sound/drivers/serial-generic.c
@@ -0,0 +1,376 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *   serial-generic.c
+ *   Copyright (c) by Daniel Kaehn <kaehndan@gmail.com
+ *   Based on serial-u16550.c by Jaroslav Kysela <perex@perex.cz>,
+ *		                 Isaku Yamahata <yamahata@private.email.ne.jp>,
+ *		                 George Hansper <ghansper@apana.org.au>,
+ *		                 Hannu Savolainen
+ *
+ * Generic serial MIDI driver using the serdev serial bus API for hardware interaction
+ */
+
+#include <linux/err.h>
+#include <linux/init.h>
+#include <linux/interrupt.h>
+#include <linux/io.h>
+#include <linux/ioport.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/serdev.h>
+#include <linux/serial_reg.h>
+#include <linux/slab.h>
+#include <linux/dev_printk.h>
+
+#include <sound/core.h>
+#include <sound/rawmidi.h>
+#include <sound/initval.h>
+
+MODULE_DESCRIPTION("Generic serial MIDI driver");
+MODULE_LICENSE("GPL");
+
+#define SERIAL_MODE_INPUT_OPEN		1
+#define SERIAL_MODE_OUTPUT_OPEN	2
+#define SERIAL_MODE_INPUT_TRIGGERED	3
+#define SERIAL_MODE_OUTPUT_TRIGGERED	4
+
+#define SERIAL_TX_STATE_ACTIVE	1
+#define SERIAL_TX_STATE_WAKEUP	2
+
+#define INTERNAL_BUF_SIZE 256
+
+struct snd_serial_generic {
+	struct serdev_device *serdev;
+
+	struct snd_card *card;
+	struct snd_rawmidi *rmidi;
+	struct snd_rawmidi_substream *midi_output;
+	struct snd_rawmidi_substream *midi_input;
+
+	unsigned int baudrate;
+
+	unsigned long filemode;		/* open status of file */
+	struct work_struct tx_work;
+	unsigned long tx_state;
+
+	char tx_buf[INTERNAL_BUF_SIZE];
+};
+
+static void snd_serial_generic_tx_wakeup(struct snd_serial_generic *drvdata)
+{
+	if (test_and_set_bit(SERIAL_TX_STATE_ACTIVE, &drvdata->tx_state))
+		set_bit(SERIAL_TX_STATE_WAKEUP, &drvdata->tx_state);
+
+	schedule_work(&drvdata->tx_work);
+}
+
+static void snd_serial_generic_tx_work(struct work_struct *work)
+{
+	int num_bytes;
+	struct snd_serial_generic *drvdata = container_of(work, struct snd_serial_generic,
+						   tx_work);
+	struct snd_rawmidi_substream *substream = drvdata->midi_output;
+
+	clear_bit(SERIAL_TX_STATE_WAKEUP, &drvdata->tx_state);
+
+	while (!snd_rawmidi_transmit_empty(substream)) {
+
+		if (!test_bit(SERIAL_MODE_OUTPUT_OPEN, &drvdata->filemode))
+			break;
+
+		num_bytes = snd_rawmidi_transmit_peek(substream, drvdata->tx_buf,
+						      INTERNAL_BUF_SIZE);
+		num_bytes = serdev_device_write_buf(drvdata->serdev, drvdata->tx_buf,
+						    num_bytes);
+
+		if (!num_bytes)
+			break;
+
+		snd_rawmidi_transmit_ack(substream, num_bytes);
+
+		if (!test_bit(SERIAL_TX_STATE_WAKEUP, &drvdata->tx_state))
+			break;
+	}
+
+	clear_bit(SERIAL_TX_STATE_ACTIVE, &drvdata->tx_state);
+}
+
+static void snd_serial_generic_write_wakeup(struct serdev_device *serdev)
+{
+	struct snd_serial_generic *drvdata = serdev_device_get_drvdata(serdev);
+
+	snd_serial_generic_tx_wakeup(drvdata);
+}
+
+static size_t snd_serial_generic_receive_buf(struct serdev_device *serdev,
+					     const u8 *buf, size_t count)
+{
+	int ret;
+	struct snd_serial_generic *drvdata = serdev_device_get_drvdata(serdev);
+
+	if (!test_bit(SERIAL_MODE_INPUT_OPEN, &drvdata->filemode))
+		return 0;
+
+	ret = snd_rawmidi_receive(drvdata->midi_input, buf, count);
+	return ret < 0 ? 0 : ret;
+}
+
+static const struct serdev_device_ops snd_serial_generic_serdev_device_ops = {
+	.receive_buf = snd_serial_generic_receive_buf,
+	.write_wakeup = snd_serial_generic_write_wakeup
+};
+
+static int snd_serial_generic_ensure_serdev_open(struct snd_serial_generic *drvdata)
+{
+	int err;
+	unsigned int actual_baud;
+
+	if (drvdata->filemode)
+		return 0;
+
+	dev_dbg(drvdata->card->dev, "Opening serial port for card %s\n",
+		drvdata->card->shortname);
+	err = serdev_device_open(drvdata->serdev);
+	if (err < 0)
+		return err;
+
+	actual_baud = serdev_device_set_baudrate(drvdata->serdev,
+		drvdata->baudrate);
+	if (actual_baud != drvdata->baudrate) {
+		dev_warn(drvdata->card->dev, "requested %d baud for card %s but it was actually set to %d\n",
+			drvdata->baudrate, drvdata->card->shortname, actual_baud);
+	}
+
+	return 0;
+}
+
+static int snd_serial_generic_input_open(struct snd_rawmidi_substream *substream)
+{
+	int err;
+	struct snd_serial_generic *drvdata = substream->rmidi->card->private_data;
+
+	dev_dbg(drvdata->card->dev, "Opening input for card %s\n",
+		drvdata->card->shortname);
+
+	err = snd_serial_generic_ensure_serdev_open(drvdata);
+	if (err < 0)
+		return err;
+
+	set_bit(SERIAL_MODE_INPUT_OPEN, &drvdata->filemode);
+	drvdata->midi_input = substream;
+	return 0;
+}
+
+static int snd_serial_generic_input_close(struct snd_rawmidi_substream *substream)
+{
+	struct snd_serial_generic *drvdata = substream->rmidi->card->private_data;
+
+	dev_dbg(drvdata->card->dev, "Closing input for card %s\n",
+		drvdata->card->shortname);
+
+	clear_bit(SERIAL_MODE_INPUT_OPEN, &drvdata->filemode);
+	clear_bit(SERIAL_MODE_INPUT_TRIGGERED, &drvdata->filemode);
+
+	drvdata->midi_input = NULL;
+
+	if (!drvdata->filemode)
+		serdev_device_close(drvdata->serdev);
+	return 0;
+}
+
+static void snd_serial_generic_input_trigger(struct snd_rawmidi_substream *substream,
+					int up)
+{
+	struct snd_serial_generic *drvdata = substream->rmidi->card->private_data;
+
+	if (up)
+		set_bit(SERIAL_MODE_INPUT_TRIGGERED, &drvdata->filemode);
+	else
+		clear_bit(SERIAL_MODE_INPUT_TRIGGERED, &drvdata->filemode);
+}
+
+static int snd_serial_generic_output_open(struct snd_rawmidi_substream *substream)
+{
+	struct snd_serial_generic *drvdata = substream->rmidi->card->private_data;
+	int err;
+
+	dev_dbg(drvdata->card->dev, "Opening output for card %s\n",
+		drvdata->card->shortname);
+
+	err = snd_serial_generic_ensure_serdev_open(drvdata);
+	if (err < 0)
+		return err;
+
+	set_bit(SERIAL_MODE_OUTPUT_OPEN, &drvdata->filemode);
+
+	drvdata->midi_output = substream;
+	return 0;
+};
+
+static int snd_serial_generic_output_close(struct snd_rawmidi_substream *substream)
+{
+	struct snd_serial_generic *drvdata = substream->rmidi->card->private_data;
+
+	dev_dbg(drvdata->card->dev, "Closing output for card %s\n",
+		drvdata->card->shortname);
+
+	clear_bit(SERIAL_MODE_OUTPUT_OPEN, &drvdata->filemode);
+	clear_bit(SERIAL_MODE_OUTPUT_TRIGGERED, &drvdata->filemode);
+
+	if (!drvdata->filemode)
+		serdev_device_close(drvdata->serdev);
+
+	drvdata->midi_output = NULL;
+
+	return 0;
+};
+
+static void snd_serial_generic_output_trigger(struct snd_rawmidi_substream *substream,
+					 int up)
+{
+	struct snd_serial_generic *drvdata = substream->rmidi->card->private_data;
+
+	if (up)
+		set_bit(SERIAL_MODE_OUTPUT_TRIGGERED, &drvdata->filemode);
+	else
+		clear_bit(SERIAL_MODE_OUTPUT_TRIGGERED, &drvdata->filemode);
+
+	if (up)
+		snd_serial_generic_tx_wakeup(drvdata);
+}
+
+static void snd_serial_generic_output_drain(struct snd_rawmidi_substream *substream)
+{
+	struct snd_serial_generic *drvdata = substream->rmidi->card->private_data;
+
+	/* Flush any pending characters */
+	serdev_device_write_flush(drvdata->serdev);
+	cancel_work_sync(&drvdata->tx_work);
+}
+
+static const struct snd_rawmidi_ops snd_serial_generic_output = {
+	.open =		snd_serial_generic_output_open,
+	.close =	snd_serial_generic_output_close,
+	.trigger =	snd_serial_generic_output_trigger,
+	.drain =	snd_serial_generic_output_drain,
+};
+
+static const struct snd_rawmidi_ops snd_serial_generic_input = {
+	.open =		snd_serial_generic_input_open,
+	.close =	snd_serial_generic_input_close,
+	.trigger =	snd_serial_generic_input_trigger,
+};
+
+static void snd_serial_generic_parse_dt(struct serdev_device *serdev,
+				struct snd_serial_generic *drvdata)
+{
+	int err;
+
+	err = of_property_read_u32(serdev->dev.of_node, "current-speed",
+		&drvdata->baudrate);
+	if (err < 0) {
+		dev_dbg(drvdata->card->dev,
+			"MIDI device reading of current-speed DT param failed with error %d, using default of 38400\n",
+			err);
+		drvdata->baudrate = 38400;
+	}
+
+}
+
+static void snd_serial_generic_substreams(struct snd_rawmidi_str *stream, int dev_num)
+{
+	struct snd_rawmidi_substream *substream;
+
+	list_for_each_entry(substream, &stream->substreams, list) {
+		sprintf(substream->name, "Serial MIDI %d-%d", dev_num, substream->number);
+	}
+}
+
+static int snd_serial_generic_rmidi(struct snd_serial_generic *drvdata,
+				int outs, int ins, struct snd_rawmidi **rmidi)
+{
+	struct snd_rawmidi *rrawmidi;
+	int err;
+
+	err = snd_rawmidi_new(drvdata->card, drvdata->card->driver, 0,
+				outs, ins, &rrawmidi);
+
+	if (err < 0)
+		return err;
+
+	snd_rawmidi_set_ops(rrawmidi, SNDRV_RAWMIDI_STREAM_INPUT,
+				&snd_serial_generic_input);
+	snd_rawmidi_set_ops(rrawmidi, SNDRV_RAWMIDI_STREAM_OUTPUT,
+				&snd_serial_generic_output);
+	strscpy(rrawmidi->name, drvdata->card->shortname);
+
+	snd_serial_generic_substreams(&rrawmidi->streams[SNDRV_RAWMIDI_STREAM_OUTPUT],
+					drvdata->serdev->ctrl->nr);
+	snd_serial_generic_substreams(&rrawmidi->streams[SNDRV_RAWMIDI_STREAM_INPUT],
+					drvdata->serdev->ctrl->nr);
+
+	rrawmidi->info_flags = SNDRV_RAWMIDI_INFO_OUTPUT |
+			       SNDRV_RAWMIDI_INFO_INPUT |
+			       SNDRV_RAWMIDI_INFO_DUPLEX;
+
+	if (rmidi)
+		*rmidi = rrawmidi;
+	return 0;
+}
+
+static int snd_serial_generic_probe(struct serdev_device *serdev)
+{
+	struct snd_card *card;
+	struct snd_serial_generic *drvdata;
+	int err;
+
+	err  = snd_devm_card_new(&serdev->dev, SNDRV_DEFAULT_IDX1,
+				SNDRV_DEFAULT_STR1, THIS_MODULE,
+				sizeof(struct snd_serial_generic), &card);
+
+	if (err < 0)
+		return err;
+
+	strscpy(card->driver, "SerialMIDI");
+	sprintf(card->shortname, "SerialMIDI-%d", serdev->ctrl->nr);
+	sprintf(card->longname, "Serial MIDI device at serial%d", serdev->ctrl->nr);
+
+	drvdata = card->private_data;
+
+	drvdata->serdev = serdev;
+	drvdata->card = card;
+
+	snd_serial_generic_parse_dt(serdev, drvdata);
+
+	INIT_WORK(&drvdata->tx_work, snd_serial_generic_tx_work);
+
+	err = snd_serial_generic_rmidi(drvdata, 1, 1, &drvdata->rmidi);
+	if (err < 0)
+		return err;
+
+	serdev_device_set_client_ops(serdev, &snd_serial_generic_serdev_device_ops);
+	serdev_device_set_drvdata(drvdata->serdev, drvdata);
+
+	err = snd_card_register(card);
+	if (err < 0)
+		return err;
+
+	return 0;
+}
+
+static const struct of_device_id snd_serial_generic_dt_ids[] = {
+	{ .compatible = "serial-midi" },
+	{},
+};
+
+MODULE_DEVICE_TABLE(of, snd_serial_generic_dt_ids);
+
+static struct serdev_device_driver snd_serial_generic_driver = {
+	.driver	= {
+		.name		= "snd-serial-generic",
+		.of_match_table	= snd_serial_generic_dt_ids,
+	},
+	.probe	= snd_serial_generic_probe,
+};
+
+module_serdev_device_driver(snd_serial_generic_driver);