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, 144 insertions, 0 deletions

diff --git a/drivers/base/regmap/regmap-raw-ram.c b/drivers/base/regmap/regmap-raw-ram.c
new file mode 100644
index 000000000..60d6e95cd
--- /dev/null
+++ b/drivers/base/regmap/regmap-raw-ram.c
@@ -0,0 +1,144 @@
+// SPDX-License-Identifier: GPL-2.0
+//
+// Register map access API - Memory region with raw access
+//
+// This is intended for testing only
+//
+// Copyright (c) 2023, Arm Ltd
+
+#include <linux/clk.h>
+#include <linux/err.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/regmap.h>
+#include <linux/slab.h>
+#include <linux/swab.h>
+
+#include "internal.h"
+
+static unsigned int decode_reg(enum regmap_endian endian, const void *reg)
+{
+	const u16 *r = reg;
+
+	if (endian == REGMAP_ENDIAN_BIG)
+		return be16_to_cpu(*r);
+	else
+		return le16_to_cpu(*r);
+}
+
+static int regmap_raw_ram_gather_write(void *context,
+				       const void *reg, size_t reg_len,
+				       const void *val, size_t val_len)
+{
+	struct regmap_ram_data *data = context;
+	unsigned int r;
+	u16 *our_buf = (u16 *)data->vals;
+	int i;
+
+	if (reg_len != 2)
+		return -EINVAL;
+	if (val_len % 2)
+		return -EINVAL;
+
+	r = decode_reg(data->reg_endian, reg);
+	if (data->noinc_reg && data->noinc_reg(data, r)) {
+		memcpy(&our_buf[r], val + val_len - 2, 2);
+		data->written[r] = true;
+	} else {
+		memcpy(&our_buf[r], val, val_len);
+
+		for (i = 0; i < val_len / 2; i++)
+			data->written[r + i] = true;
+	}
+	
+	return 0;
+}
+
+static int regmap_raw_ram_write(void *context, const void *data, size_t count)
+{
+	return regmap_raw_ram_gather_write(context, data, 2,
+					   data + 2, count - 2);
+}
+
+static int regmap_raw_ram_read(void *context,
+			       const void *reg, size_t reg_len,
+			       void *val, size_t val_len)
+{
+	struct regmap_ram_data *data = context;
+	unsigned int r;
+	u16 *our_buf = (u16 *)data->vals;
+	int i;
+
+	if (reg_len != 2)
+		return -EINVAL;
+	if (val_len % 2)
+		return -EINVAL;
+
+	r = decode_reg(data->reg_endian, reg);
+	if (data->noinc_reg && data->noinc_reg(data, r)) {
+		for (i = 0; i < val_len; i += 2)
+			memcpy(val + i, &our_buf[r], 2);
+		data->read[r] = true;
+	} else {
+		memcpy(val, &our_buf[r], val_len);
+
+		for (i = 0; i < val_len / 2; i++)
+			data->read[r + i] = true;
+	}
+
+	return 0;
+}
+
+static void regmap_raw_ram_free_context(void *context)
+{
+	struct regmap_ram_data *data = context;
+
+	kfree(data->vals);
+	kfree(data->read);
+	kfree(data->written);
+	kfree(data);
+}
+
+static const struct regmap_bus regmap_raw_ram = {
+	.fast_io = true,
+	.write = regmap_raw_ram_write,
+	.gather_write = regmap_raw_ram_gather_write,
+	.read = regmap_raw_ram_read,
+	.free_context = regmap_raw_ram_free_context,
+};
+
+struct regmap *__regmap_init_raw_ram(struct device *dev,
+				     const struct regmap_config *config,
+				     struct regmap_ram_data *data,
+				     struct lock_class_key *lock_key,
+				     const char *lock_name)
+{
+	struct regmap *map;
+
+	if (config->reg_bits != 16)
+		return ERR_PTR(-EINVAL);
+
+	if (!config->max_register) {
+		pr_crit("No max_register specified for RAM regmap\n");
+		return ERR_PTR(-EINVAL);
+	}
+
+	data->read = kzalloc_objs(bool, config->max_register + 1);
+	if (!data->read)
+		return ERR_PTR(-ENOMEM);
+
+	data->written = kzalloc_objs(bool, config->max_register + 1);
+	if (!data->written)
+		return ERR_PTR(-ENOMEM);
+
+	data->reg_endian = config->reg_format_endian;
+
+	map = __regmap_init(dev, &regmap_raw_ram, data, config,
+			    lock_key, lock_name);
+
+	return map;
+}
+EXPORT_SYMBOL_GPL(__regmap_init_raw_ram);
+
+MODULE_DESCRIPTION("Register map access API - Memory region with raw access");
+MODULE_LICENSE("GPL v2");