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, 71 insertions, 0 deletions

diff --git a/drivers/base/regmap/regmap-i3c.c b/drivers/base/regmap/regmap-i3c.c
new file mode 100644
index 000000000..5af583d47
--- /dev/null
+++ b/drivers/base/regmap/regmap-i3c.c
@@ -0,0 +1,71 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2018 Synopsys, Inc. and/or its affiliates.
+
+#include <linux/array_size.h>
+#include <linux/regmap.h>
+#include <linux/i3c/device.h>
+#include <linux/i3c/master.h>
+#include <linux/module.h>
+
+static int regmap_i3c_write(void *context, const void *data, size_t count)
+{
+	struct device *dev = context;
+	struct i3c_device *i3c = dev_to_i3cdev(dev);
+	struct i3c_xfer xfers[] = {
+		{
+			.rnw = false,
+			.len = count,
+			.data.out = data,
+		},
+	};
+
+	return i3c_device_do_xfers(i3c, xfers, ARRAY_SIZE(xfers), I3C_SDR);
+}
+
+static int regmap_i3c_read(void *context,
+			   const void *reg, size_t reg_size,
+			   void *val, size_t val_size)
+{
+	struct device *dev = context;
+	struct i3c_device *i3c = dev_to_i3cdev(dev);
+	struct i3c_xfer xfers[2];
+
+	xfers[0].rnw = false;
+	xfers[0].len = reg_size;
+	xfers[0].data.out = reg;
+
+	xfers[1].rnw = true;
+	xfers[1].len = val_size;
+	xfers[1].data.in = val;
+
+	return i3c_device_do_xfers(i3c, xfers, ARRAY_SIZE(xfers), I3C_SDR);
+}
+
+static const struct regmap_bus regmap_i3c = {
+	.write = regmap_i3c_write,
+	.read = regmap_i3c_read,
+};
+
+struct regmap *__regmap_init_i3c(struct i3c_device *i3c,
+				 const struct regmap_config *config,
+				 struct lock_class_key *lock_key,
+				 const char *lock_name)
+{
+	return __regmap_init(&i3c->dev, &regmap_i3c, &i3c->dev, config,
+				  lock_key, lock_name);
+}
+EXPORT_SYMBOL_GPL(__regmap_init_i3c);
+
+struct regmap *__devm_regmap_init_i3c(struct i3c_device *i3c,
+				      const struct regmap_config *config,
+				      struct lock_class_key *lock_key,
+				      const char *lock_name)
+{
+	return __devm_regmap_init(&i3c->dev, &regmap_i3c, &i3c->dev, config,
+				  lock_key, lock_name);
+}
+EXPORT_SYMBOL_GPL(__devm_regmap_init_i3c);
+
+MODULE_AUTHOR("Vitor Soares <vitor.soares@synopsys.com>");
+MODULE_DESCRIPTION("regmap I3C Module");
+MODULE_LICENSE("GPL v2");