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, 171 insertions, 0 deletions

diff --git a/drivers/auxdisplay/ks0108.c b/drivers/auxdisplay/ks0108.c
new file mode 100644
index 000000000..51587f0fd
--- /dev/null
+++ b/drivers/auxdisplay/ks0108.c
@@ -0,0 +1,171 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ *    Filename: ks0108.c
+ *     Version: 0.1.0
+ * Description: ks0108 LCD Controller driver
+ *     Depends: parport
+ *
+ *      Author: Copyright (C) Miguel Ojeda <ojeda@kernel.org>
+ *        Date: 2006-10-31
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/delay.h>
+#include <linux/parport.h>
+#include <linux/ks0108.h>
+
+#define KS0108_NAME "ks0108"
+
+/*
+ * Module Parameters
+ */
+
+static unsigned int ks0108_port = CONFIG_KS0108_PORT;
+module_param(ks0108_port, uint, 0444);
+MODULE_PARM_DESC(ks0108_port, "Parallel port where the LCD is connected");
+
+static unsigned int ks0108_delay = CONFIG_KS0108_DELAY;
+module_param(ks0108_delay, uint, 0444);
+MODULE_PARM_DESC(ks0108_delay, "Delay between each control writing (microseconds)");
+
+/*
+ * Device
+ */
+
+static struct parport *ks0108_parport;
+static struct pardevice *ks0108_pardevice;
+
+/*
+ * ks0108 Exported Commands (don't lock)
+ *
+ *   You _should_ lock in the top driver: This functions _should not_
+ *   get race conditions in any way. Locking for each byte here would be
+ *   so slow and useless.
+ *
+ *   There are not bit definitions because they are not flags,
+ *   just arbitrary combinations defined by the documentation for each
+ *   function in the ks0108 LCD controller. If you want to know what means
+ *   a specific combination, look at the function's name.
+ *
+ *   The ks0108_writecontrol bits need to be reverted ^(0,1,3) because
+ *   the parallel port also revert them using a "not" logic gate.
+ */
+
+#define bit(n) (((unsigned char)1)<<(n))
+
+void ks0108_writedata(unsigned char byte)
+{
+	parport_write_data(ks0108_parport, byte);
+}
+
+void ks0108_writecontrol(unsigned char byte)
+{
+	udelay(ks0108_delay);
+	parport_write_control(ks0108_parport, byte ^ (bit(0) | bit(1) | bit(3)));
+}
+
+void ks0108_displaystate(unsigned char state)
+{
+	ks0108_writedata((state ? bit(0) : 0) | bit(1) | bit(2) | bit(3) | bit(4) | bit(5));
+}
+
+void ks0108_startline(unsigned char startline)
+{
+	ks0108_writedata(min_t(unsigned char, startline, 63) | bit(6) |
+			 bit(7));
+}
+
+void ks0108_address(unsigned char address)
+{
+	ks0108_writedata(min_t(unsigned char, address, 63) | bit(6));
+}
+
+void ks0108_page(unsigned char page)
+{
+	ks0108_writedata(min_t(unsigned char, page, 7) | bit(3) | bit(4) |
+			 bit(5) | bit(7));
+}
+
+EXPORT_SYMBOL_GPL(ks0108_writedata);
+EXPORT_SYMBOL_GPL(ks0108_writecontrol);
+EXPORT_SYMBOL_GPL(ks0108_displaystate);
+EXPORT_SYMBOL_GPL(ks0108_startline);
+EXPORT_SYMBOL_GPL(ks0108_address);
+EXPORT_SYMBOL_GPL(ks0108_page);
+
+/*
+ * Is the module inited?
+ */
+
+static unsigned char ks0108_inited;
+unsigned char ks0108_isinited(void)
+{
+	return ks0108_inited;
+}
+EXPORT_SYMBOL_GPL(ks0108_isinited);
+
+static void ks0108_parport_attach(struct parport *port)
+{
+	struct pardev_cb ks0108_cb;
+
+	if (port->base != ks0108_port)
+		return;
+
+	memset(&ks0108_cb, 0, sizeof(ks0108_cb));
+	ks0108_cb.flags = PARPORT_DEV_EXCL;
+	ks0108_pardevice = parport_register_dev_model(port, KS0108_NAME,
+						      &ks0108_cb, 0);
+	if (!ks0108_pardevice) {
+		pr_err("ERROR: parport didn't register new device\n");
+		return;
+	}
+	if (parport_claim(ks0108_pardevice)) {
+		pr_err("could not claim access to parport %i. Aborting.\n",
+		       ks0108_port);
+		goto err_unreg_device;
+	}
+
+	ks0108_parport = port;
+	ks0108_inited = 1;
+	return;
+
+err_unreg_device:
+	parport_unregister_device(ks0108_pardevice);
+	ks0108_pardevice = NULL;
+}
+
+static void ks0108_parport_detach(struct parport *port)
+{
+	if (port->base != ks0108_port)
+		return;
+
+	if (!ks0108_pardevice) {
+		pr_err("%s: already unregistered.\n", KS0108_NAME);
+		return;
+	}
+
+	parport_release(ks0108_pardevice);
+	parport_unregister_device(ks0108_pardevice);
+	ks0108_pardevice = NULL;
+	ks0108_parport = NULL;
+}
+
+/*
+ * Module Init & Exit
+ */
+
+static struct parport_driver ks0108_parport_driver = {
+	.name = "ks0108",
+	.match_port = ks0108_parport_attach,
+	.detach = ks0108_parport_detach,
+};
+module_parport_driver(ks0108_parport_driver);
+
+MODULE_LICENSE("GPL v2");
+MODULE_AUTHOR("Miguel Ojeda <ojeda@kernel.org>");
+MODULE_DESCRIPTION("ks0108 LCD Controller driver");
+