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, 178 insertions, 0 deletions

diff --git a/sound/drivers/virmidi.c b/sound/drivers/virmidi.c
new file mode 100644
index 000000000..70e16105f
--- /dev/null
+++ b/sound/drivers/virmidi.c
@@ -0,0 +1,178 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *  Dummy soundcard for virtual rawmidi devices
+ *
+ *  Copyright (c) 2000 by Takashi Iwai <tiwai@suse.de>
+ */
+
+/*
+ * VIRTUAL RAW MIDI DEVICE CARDS
+ *
+ * This dummy card contains up to 4 virtual rawmidi devices.
+ * They are not real rawmidi devices but just associated with sequencer
+ * clients, so that any input/output sources can be connected as a raw
+ * MIDI device arbitrary.
+ * Also, multiple access is allowed to a single rawmidi device.
+ *
+ * Typical usage is like following:
+ * - Load snd-virmidi module.
+ *	# modprobe snd-virmidi index=2
+ *   Then, sequencer clients 72:0 to 75:0 will be created, which are
+ *   mapped from /dev/snd/midiC1D0 to /dev/snd/midiC1D3, respectively.
+ *
+ * - Connect input/output via aconnect.
+ *	% aconnect 64:0 72:0	# keyboard input redirection 64:0 -> 72:0
+ *	% aconnect 72:0 65:0	# output device redirection 72:0 -> 65:0
+ *
+ * - Run application using a midi device (eg. /dev/snd/midiC1D0)
+ */
+
+#include <linux/init.h>
+#include <linux/wait.h>
+#include <linux/err.h>
+#include <linux/platform_device.h>
+#include <linux/module.h>
+#include <sound/core.h>
+#include <sound/seq_kernel.h>
+#include <sound/seq_virmidi.h>
+#include <sound/initval.h>
+
+/* hack: OSS defines midi_devs, so undefine it (versioned symbols) */
+#undef midi_devs
+
+MODULE_AUTHOR("Takashi Iwai <tiwai@suse.de>");
+MODULE_DESCRIPTION("Dummy soundcard for virtual rawmidi devices");
+MODULE_LICENSE("GPL");
+
+#define MAX_MIDI_DEVICES	4
+
+static int index[SNDRV_CARDS] = SNDRV_DEFAULT_IDX;	/* Index 0-MAX */
+static char *id[SNDRV_CARDS] = SNDRV_DEFAULT_STR;	/* ID for this card */
+static bool enable[SNDRV_CARDS] = {1, [1 ... (SNDRV_CARDS - 1)] = 0};
+static int midi_devs[SNDRV_CARDS] = {[0 ... (SNDRV_CARDS - 1)] = 4};
+
+module_param_array(index, int, NULL, 0444);
+MODULE_PARM_DESC(index, "Index value for virmidi soundcard.");
+module_param_array(id, charp, NULL, 0444);
+MODULE_PARM_DESC(id, "ID string for virmidi soundcard.");
+module_param_array(enable, bool, NULL, 0444);
+MODULE_PARM_DESC(enable, "Enable this soundcard.");
+module_param_array(midi_devs, int, NULL, 0444);
+MODULE_PARM_DESC(midi_devs, "MIDI devices # (1-4)");
+
+struct snd_card_virmidi {
+	struct snd_card *card;
+	struct snd_rawmidi *midi[MAX_MIDI_DEVICES];
+};
+
+static struct platform_device *devices[SNDRV_CARDS];
+
+
+static int snd_virmidi_probe(struct platform_device *devptr)
+{
+	struct snd_card *card;
+	struct snd_card_virmidi *vmidi;
+	int idx, err;
+	int dev = devptr->id;
+
+	if (dev < 0 || dev >= SNDRV_CARDS) {
+		dev_warn(&devptr->dev,
+			 "Invalid card index %d, using default 0\n", dev);
+		dev = 0;
+	}
+
+	err = snd_devm_card_new(&devptr->dev, index[dev], id[dev], THIS_MODULE,
+				sizeof(struct snd_card_virmidi), &card);
+	if (err < 0)
+		return err;
+	vmidi = card->private_data;
+	vmidi->card = card;
+
+	if (midi_devs[dev] > MAX_MIDI_DEVICES) {
+		dev_warn(&devptr->dev,
+			 "too much midi devices for virmidi %d: force to use %d\n",
+			 dev, MAX_MIDI_DEVICES);
+		midi_devs[dev] = MAX_MIDI_DEVICES;
+	}
+	for (idx = 0; idx < midi_devs[dev]; idx++) {
+		struct snd_rawmidi *rmidi;
+
+		err = snd_virmidi_new(card, idx, &rmidi);
+		if (err < 0)
+			return err;
+		vmidi->midi[idx] = rmidi;
+		strscpy(rmidi->name, "Virtual Raw MIDI");
+	}
+
+	strscpy(card->driver, "VirMIDI");
+	strscpy(card->shortname, "VirMIDI");
+	sprintf(card->longname, "Virtual MIDI Card %i", dev + 1);
+
+	err = snd_card_register(card);
+	if (err)
+		return err;
+
+	platform_set_drvdata(devptr, card);
+	return 0;
+}
+
+#define SND_VIRMIDI_DRIVER	"snd_virmidi"
+
+static struct platform_driver snd_virmidi_driver = {
+	.probe		= snd_virmidi_probe,
+	.driver		= {
+		.name	= SND_VIRMIDI_DRIVER,
+	},
+};
+
+static void snd_virmidi_unregister_all(void)
+{
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(devices); ++i)
+		platform_device_unregister(devices[i]);
+	platform_driver_unregister(&snd_virmidi_driver);
+}
+
+static int __init alsa_card_virmidi_init(void)
+{
+	int i, cards, err;
+
+	err = platform_driver_register(&snd_virmidi_driver);
+	if (err < 0)
+		return err;
+
+	cards = 0;
+	for (i = 0; i < SNDRV_CARDS; i++) {
+		struct platform_device *device;
+
+		if (!enable[i])
+			continue;
+		device = platform_device_register_simple(SND_VIRMIDI_DRIVER,
+							 i, NULL, 0);
+		if (IS_ERR(device))
+			continue;
+		if (!platform_get_drvdata(device)) {
+			platform_device_unregister(device);
+			continue;
+		}
+		devices[i] = device;
+		cards++;
+	}
+	if (!cards) {
+#ifdef MODULE
+		pr_err("Card-VirMIDI soundcard not found or device busy\n");
+#endif
+		snd_virmidi_unregister_all();
+		return -ENODEV;
+	}
+	return 0;
+}
+
+static void __exit alsa_card_virmidi_exit(void)
+{
+	snd_virmidi_unregister_all();
+}
+
+module_init(alsa_card_virmidi_init)
+module_exit(alsa_card_virmidi_exit)