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, 231 insertions, 0 deletions

diff --git a/drivers/base/regmap/regmap-fsi.c b/drivers/base/regmap/regmap-fsi.c
new file mode 100644
index 000000000..3d2f3cb31
--- /dev/null
+++ b/drivers/base/regmap/regmap-fsi.c
@@ -0,0 +1,231 @@
+// SPDX-License-Identifier: GPL-2.0
+//
+// Register map access API - FSI support
+//
+// Copyright 2022 IBM Corp
+//
+// Author: Eddie James <eajames@linux.ibm.com>
+
+#include <linux/fsi.h>
+#include <linux/module.h>
+#include <linux/regmap.h>
+
+#include "internal.h"
+
+static int regmap_fsi32_reg_read(void *context, unsigned int reg, unsigned int *val)
+{
+	u32 v;
+	int ret;
+
+	ret = fsi_slave_read(context, reg, &v, sizeof(v));
+	if (ret)
+		return ret;
+
+	*val = v;
+	return 0;
+}
+
+static int regmap_fsi32_reg_write(void *context, unsigned int reg, unsigned int val)
+{
+	u32 v = val;
+
+	return fsi_slave_write(context, reg, &v, sizeof(v));
+}
+
+static const struct regmap_bus regmap_fsi32 = {
+	.reg_write = regmap_fsi32_reg_write,
+	.reg_read = regmap_fsi32_reg_read,
+};
+
+static int regmap_fsi32le_reg_read(void *context, unsigned int reg, unsigned int *val)
+{
+	__be32 v;
+	int ret;
+
+	ret = fsi_slave_read(context, reg, &v, sizeof(v));
+	if (ret)
+		return ret;
+
+	*val = be32_to_cpu(v);
+	return 0;
+}
+
+static int regmap_fsi32le_reg_write(void *context, unsigned int reg, unsigned int val)
+{
+	__be32 v = cpu_to_be32(val);
+
+	return fsi_slave_write(context, reg, &v, sizeof(v));
+}
+
+static const struct regmap_bus regmap_fsi32le = {
+	.reg_write = regmap_fsi32le_reg_write,
+	.reg_read = regmap_fsi32le_reg_read,
+};
+
+static int regmap_fsi16_reg_read(void *context, unsigned int reg, unsigned int *val)
+{
+	u16 v;
+	int ret;
+
+	ret = fsi_slave_read(context, reg, &v, sizeof(v));
+	if (ret)
+		return ret;
+
+	*val = v;
+	return 0;
+}
+
+static int regmap_fsi16_reg_write(void *context, unsigned int reg, unsigned int val)
+{
+	u16 v;
+
+	if (val > 0xffff)
+		return -EINVAL;
+
+	v = val;
+	return fsi_slave_write(context, reg, &v, sizeof(v));
+}
+
+static const struct regmap_bus regmap_fsi16 = {
+	.reg_write = regmap_fsi16_reg_write,
+	.reg_read = regmap_fsi16_reg_read,
+};
+
+static int regmap_fsi16le_reg_read(void *context, unsigned int reg, unsigned int *val)
+{
+	__be16 v;
+	int ret;
+
+	ret = fsi_slave_read(context, reg, &v, sizeof(v));
+	if (ret)
+		return ret;
+
+	*val = be16_to_cpu(v);
+	return 0;
+}
+
+static int regmap_fsi16le_reg_write(void *context, unsigned int reg, unsigned int val)
+{
+	__be16 v;
+
+	if (val > 0xffff)
+		return -EINVAL;
+
+	v = cpu_to_be16(val);
+	return fsi_slave_write(context, reg, &v, sizeof(v));
+}
+
+static const struct regmap_bus regmap_fsi16le = {
+	.reg_write = regmap_fsi16le_reg_write,
+	.reg_read = regmap_fsi16le_reg_read,
+};
+
+static int regmap_fsi8_reg_read(void *context, unsigned int reg, unsigned int *val)
+{
+	u8 v;
+	int ret;
+
+	ret = fsi_slave_read(context, reg, &v, sizeof(v));
+	if (ret)
+		return ret;
+
+	*val = v;
+	return 0;
+}
+
+static int regmap_fsi8_reg_write(void *context, unsigned int reg, unsigned int val)
+{
+	u8 v;
+
+	if (val > 0xff)
+		return -EINVAL;
+
+	v = val;
+	return fsi_slave_write(context, reg, &v, sizeof(v));
+}
+
+static const struct regmap_bus regmap_fsi8 = {
+	.reg_write = regmap_fsi8_reg_write,
+	.reg_read = regmap_fsi8_reg_read,
+};
+
+static const struct regmap_bus *regmap_get_fsi_bus(struct fsi_device *fsi_dev,
+						   const struct regmap_config *config)
+{
+	const struct regmap_bus *bus = NULL;
+
+	if (config->reg_bits == 8 || config->reg_bits == 16 || config->reg_bits == 32) {
+		switch (config->val_bits) {
+		case 8:
+			bus = &regmap_fsi8;
+			break;
+		case 16:
+			switch (regmap_get_val_endian(&fsi_dev->dev, NULL, config)) {
+			case REGMAP_ENDIAN_LITTLE:
+#ifdef __LITTLE_ENDIAN
+			case REGMAP_ENDIAN_NATIVE:
+#endif
+				bus = &regmap_fsi16le;
+				break;
+			case REGMAP_ENDIAN_DEFAULT:
+			case REGMAP_ENDIAN_BIG:
+#ifdef __BIG_ENDIAN
+			case REGMAP_ENDIAN_NATIVE:
+#endif
+				bus = &regmap_fsi16;
+				break;
+			default:
+				break;
+			}
+			break;
+		case 32:
+			switch (regmap_get_val_endian(&fsi_dev->dev, NULL, config)) {
+			case REGMAP_ENDIAN_LITTLE:
+#ifdef __LITTLE_ENDIAN
+			case REGMAP_ENDIAN_NATIVE:
+#endif
+				bus = &regmap_fsi32le;
+				break;
+			case REGMAP_ENDIAN_DEFAULT:
+			case REGMAP_ENDIAN_BIG:
+#ifdef __BIG_ENDIAN
+			case REGMAP_ENDIAN_NATIVE:
+#endif
+				bus = &regmap_fsi32;
+				break;
+			default:
+				break;
+			}
+			break;
+		}
+	}
+
+	return bus ?: ERR_PTR(-EOPNOTSUPP);
+}
+
+struct regmap *__regmap_init_fsi(struct fsi_device *fsi_dev, const struct regmap_config *config,
+				 struct lock_class_key *lock_key, const char *lock_name)
+{
+	const struct regmap_bus *bus = regmap_get_fsi_bus(fsi_dev, config);
+
+	if (IS_ERR(bus))
+		return ERR_CAST(bus);
+
+	return __regmap_init(&fsi_dev->dev, bus, fsi_dev->slave, config, lock_key, lock_name);
+}
+EXPORT_SYMBOL_GPL(__regmap_init_fsi);
+
+struct regmap *__devm_regmap_init_fsi(struct fsi_device *fsi_dev,
+				      const struct regmap_config *config,
+				      struct lock_class_key *lock_key, const char *lock_name)
+{
+	const struct regmap_bus *bus = regmap_get_fsi_bus(fsi_dev, config);
+
+	if (IS_ERR(bus))
+		return ERR_CAST(bus);
+
+	return __devm_regmap_init(&fsi_dev->dev, bus, fsi_dev->slave, config, lock_key, lock_name);
+}
+EXPORT_SYMBOL_GPL(__devm_regmap_init_fsi);
+
+MODULE_LICENSE("GPL");