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, 74 insertions, 0 deletions

diff --git a/drivers/hid/hid-primax.c b/drivers/hid/hid-primax.c
new file mode 100644
index 000000000..8db054280
--- /dev/null
+++ b/drivers/hid/hid-primax.c
@@ -0,0 +1,74 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * HID driver for primax and similar keyboards with in-band modifiers
+ *
+ * Copyright 2011 Google Inc. All Rights Reserved
+ *
+ * Author:
+ *	Terry Lambert <tlambert@google.com>
+ */
+
+#include <linux/device.h>
+#include <linux/hid.h>
+#include <linux/module.h>
+
+#include "hid-ids.h"
+
+static int px_raw_event(struct hid_device *hid, struct hid_report *report,
+	 u8 *data, int size)
+{
+	int idx = size;
+
+	switch (report->id) {
+	case 0:		/* keyboard input */
+		/*
+		 * Convert in-band modifier key values into out of band
+		 * modifier bits and pull the key strokes from the report.
+		 * Thus a report data set which looked like:
+		 *
+		 * [00][00][E0][30][00][00][00][00]
+		 * (no modifier bits + "Left Shift" key + "1" key)
+		 *
+		 * Would be converted to:
+		 *
+		 * [01][00][00][30][00][00][00][00]
+		 * (Left Shift modifier bit + "1" key)
+		 *
+		 * As long as it's in the size range, the upper level
+		 * drivers don't particularly care if there are in-band
+		 * 0-valued keys, so they don't stop parsing.
+		 */
+		while (--idx > 1) {
+			if (data[idx] < 0xE0 || data[idx] > 0xE7)
+				continue;
+			data[0] |= (1 << (data[idx] - 0xE0));
+			data[idx] = 0;
+		}
+		hid_report_raw_event(hid, HID_INPUT_REPORT, data, size, size, 0);
+		return 1;
+
+	default:	/* unknown report */
+		/* Unknown report type; pass upstream */
+		hid_info(hid, "unknown report type %d\n", report->id);
+		break;
+	}
+
+	return 0;
+}
+
+static const struct hid_device_id px_devices[] = {
+	{ HID_USB_DEVICE(USB_VENDOR_ID_PRIMAX, USB_DEVICE_ID_PRIMAX_KEYBOARD) },
+	{ }
+};
+MODULE_DEVICE_TABLE(hid, px_devices);
+
+static struct hid_driver px_driver = {
+	.name = "primax",
+	.id_table = px_devices,
+	.raw_event = px_raw_event,
+};
+module_hid_driver(px_driver);
+
+MODULE_AUTHOR("Terry Lambert <tlambert@google.com>");
+MODULE_DESCRIPTION("HID driver for primax and similar keyboards with in-band modifiers");
+MODULE_LICENSE("GPL");