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, 121 insertions, 0 deletions

diff --git a/drivers/base/regmap/regmap-mdio.c b/drivers/base/regmap/regmap-mdio.c
new file mode 100644
index 000000000..9573bf3b5
--- /dev/null
+++ b/drivers/base/regmap/regmap-mdio.c
@@ -0,0 +1,121 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/errno.h>
+#include <linux/mdio.h>
+#include <linux/module.h>
+#include <linux/regmap.h>
+
+#define REGVAL_MASK		GENMASK(15, 0)
+#define REGNUM_C22_MASK		GENMASK(4, 0)
+/* Clause-45 mask includes the device type (5 bit) and actual register number (16 bit) */
+#define REGNUM_C45_MASK		GENMASK(20, 0)
+
+static int regmap_mdio_c22_read(void *context, unsigned int reg, unsigned int *val)
+{
+	struct mdio_device *mdio_dev = context;
+	int ret;
+
+	if (unlikely(reg & ~REGNUM_C22_MASK))
+		return -ENXIO;
+
+	ret = mdiodev_read(mdio_dev, reg);
+	if (ret < 0)
+		return ret;
+
+	*val = ret & REGVAL_MASK;
+
+	return 0;
+}
+
+static int regmap_mdio_c22_write(void *context, unsigned int reg, unsigned int val)
+{
+	struct mdio_device *mdio_dev = context;
+
+	if (unlikely(reg & ~REGNUM_C22_MASK))
+		return -ENXIO;
+
+	return mdiodev_write(mdio_dev, reg, val);
+}
+
+static const struct regmap_bus regmap_mdio_c22_bus = {
+	.reg_write = regmap_mdio_c22_write,
+	.reg_read = regmap_mdio_c22_read,
+};
+
+static int regmap_mdio_c45_read(void *context, unsigned int reg, unsigned int *val)
+{
+	struct mdio_device *mdio_dev = context;
+	unsigned int devad;
+	int ret;
+
+	if (unlikely(reg & ~REGNUM_C45_MASK))
+		return -ENXIO;
+
+	devad = reg >> REGMAP_MDIO_C45_DEVAD_SHIFT;
+	reg = reg & REGMAP_MDIO_C45_REGNUM_MASK;
+
+	ret = mdiodev_c45_read(mdio_dev, devad, reg);
+	if (ret < 0)
+		return ret;
+
+	*val = ret & REGVAL_MASK;
+
+	return 0;
+}
+
+static int regmap_mdio_c45_write(void *context, unsigned int reg, unsigned int val)
+{
+	struct mdio_device *mdio_dev = context;
+	unsigned int devad;
+
+	if (unlikely(reg & ~REGNUM_C45_MASK))
+		return -ENXIO;
+
+	devad = reg >> REGMAP_MDIO_C45_DEVAD_SHIFT;
+	reg = reg & REGMAP_MDIO_C45_REGNUM_MASK;
+
+	return mdiodev_c45_write(mdio_dev, devad, reg, val);
+}
+
+static const struct regmap_bus regmap_mdio_c45_bus = {
+	.reg_write = regmap_mdio_c45_write,
+	.reg_read = regmap_mdio_c45_read,
+};
+
+struct regmap *__regmap_init_mdio(struct mdio_device *mdio_dev,
+	const struct regmap_config *config, struct lock_class_key *lock_key,
+	const char *lock_name)
+{
+	const struct regmap_bus *bus;
+
+	if (config->reg_bits == 5 && config->val_bits == 16)
+		bus = &regmap_mdio_c22_bus;
+	else if (config->reg_bits == 21 && config->val_bits == 16)
+		bus = &regmap_mdio_c45_bus;
+	else
+		return ERR_PTR(-EOPNOTSUPP);
+
+	return __regmap_init(&mdio_dev->dev, bus, mdio_dev, config, lock_key, lock_name);
+}
+EXPORT_SYMBOL_GPL(__regmap_init_mdio);
+
+struct regmap *__devm_regmap_init_mdio(struct mdio_device *mdio_dev,
+	const struct regmap_config *config, struct lock_class_key *lock_key,
+	const char *lock_name)
+{
+	const struct regmap_bus *bus;
+
+	if (config->reg_bits == 5 && config->val_bits == 16)
+		bus = &regmap_mdio_c22_bus;
+	else if (config->reg_bits == 21 && config->val_bits == 16)
+		bus = &regmap_mdio_c45_bus;
+	else
+		return ERR_PTR(-EOPNOTSUPP);
+
+	return __devm_regmap_init(&mdio_dev->dev, bus, mdio_dev, config, lock_key, lock_name);
+}
+EXPORT_SYMBOL_GPL(__devm_regmap_init_mdio);
+
+MODULE_AUTHOR("Sander Vanheule <sander@svanheule.net>");
+MODULE_DESCRIPTION("regmap MDIO Module");
+MODULE_LICENSE("GPL v2");