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/nvmem/max77759-nvmem.c b/drivers/nvmem/max77759-nvmem.c
new file mode 100644
index 000000000..283000ec3
--- /dev/null
+++ b/drivers/nvmem/max77759-nvmem.c
@@ -0,0 +1,144 @@
+// SPDX-License-Identifier: GPL-2.0-only
+//
+// Copyright 2020 Google Inc
+// Copyright 2025 Linaro Ltd.
+//
+// NVMEM driver for Maxim MAX77759
+
+#include <linux/dev_printk.h>
+#include <linux/device.h>
+#include <linux/device/driver.h>
+#include <linux/err.h>
+#include <linux/mfd/max77759.h>
+#include <linux/module.h>
+#include <linux/nvmem-provider.h>
+#include <linux/overflow.h>
+#include <linux/platform_device.h>
+#include <linux/string.h>
+
+#define MAX77759_NVMEM_OPCODE_HEADER_LEN 3
+/*
+ * NVMEM commands have a three byte header (which becomes part of the command),
+ * so we need to subtract that.
+ */
+#define MAX77759_NVMEM_SIZE (MAX77759_MAXQ_OPCODE_MAXLENGTH \
+			     - MAX77759_NVMEM_OPCODE_HEADER_LEN)
+
+struct max77759_nvmem {
+	struct device *dev;
+	struct max77759 *max77759;
+};
+
+static int max77759_nvmem_reg_read(void *priv, unsigned int offset,
+				   void *val, size_t bytes)
+{
+	struct max77759_nvmem *nvmem = priv;
+	DEFINE_FLEX(struct max77759_maxq_command, cmd, cmd, length,
+		    MAX77759_NVMEM_OPCODE_HEADER_LEN);
+	DEFINE_FLEX(struct max77759_maxq_response, rsp, rsp, length,
+		    MAX77759_MAXQ_OPCODE_MAXLENGTH);
+	int ret;
+
+	cmd->cmd[0] = MAX77759_MAXQ_OPCODE_USER_SPACE_READ;
+	cmd->cmd[1] = offset;
+	cmd->cmd[2] = bytes;
+	rsp->length = bytes + MAX77759_NVMEM_OPCODE_HEADER_LEN;
+
+	ret = max77759_maxq_command(nvmem->max77759, cmd, rsp);
+	if (ret < 0)
+		return ret;
+
+	if (memcmp(cmd->cmd, rsp->rsp, MAX77759_NVMEM_OPCODE_HEADER_LEN)) {
+		dev_warn(nvmem->dev, "protocol error (read)\n");
+		return -EIO;
+	}
+
+	memcpy(val, &rsp->rsp[MAX77759_NVMEM_OPCODE_HEADER_LEN], bytes);
+
+	return 0;
+}
+
+static int max77759_nvmem_reg_write(void *priv, unsigned int offset,
+				    void *val, size_t bytes)
+{
+	struct max77759_nvmem *nvmem = priv;
+	DEFINE_FLEX(struct max77759_maxq_command, cmd, cmd, length,
+		    MAX77759_MAXQ_OPCODE_MAXLENGTH);
+	DEFINE_FLEX(struct max77759_maxq_response, rsp, rsp, length,
+		    MAX77759_MAXQ_OPCODE_MAXLENGTH);
+	int ret;
+
+	cmd->cmd[0] = MAX77759_MAXQ_OPCODE_USER_SPACE_WRITE;
+	cmd->cmd[1] = offset;
+	cmd->cmd[2] = bytes;
+	memcpy(&cmd->cmd[MAX77759_NVMEM_OPCODE_HEADER_LEN], val, bytes);
+	cmd->length = bytes + MAX77759_NVMEM_OPCODE_HEADER_LEN;
+	rsp->length = cmd->length;
+
+	ret = max77759_maxq_command(nvmem->max77759, cmd, rsp);
+	if (ret < 0)
+		return ret;
+
+	if (memcmp(cmd->cmd, rsp->rsp, cmd->length)) {
+		dev_warn(nvmem->dev, "protocol error (write)\n");
+		return -EIO;
+	}
+
+	return 0;
+}
+
+static int max77759_nvmem_probe(struct platform_device *pdev)
+{
+	struct nvmem_config config = {
+		.dev = &pdev->dev,
+		.name = dev_name(&pdev->dev),
+		.id = NVMEM_DEVID_NONE,
+		.type = NVMEM_TYPE_EEPROM,
+		.ignore_wp = true,
+		.size = MAX77759_NVMEM_SIZE,
+		.word_size = sizeof(u8),
+		.stride = sizeof(u8),
+		.reg_read = max77759_nvmem_reg_read,
+		.reg_write = max77759_nvmem_reg_write,
+	};
+	struct max77759_nvmem *nvmem;
+
+	nvmem = devm_kzalloc(&pdev->dev, sizeof(*nvmem), GFP_KERNEL);
+	if (!nvmem)
+		return -ENOMEM;
+
+	nvmem->dev = &pdev->dev;
+	nvmem->max77759 = dev_get_drvdata(pdev->dev.parent);
+
+	config.priv = nvmem;
+
+	return PTR_ERR_OR_ZERO(devm_nvmem_register(config.dev, &config));
+}
+
+static const struct of_device_id max77759_nvmem_of_id[] = {
+	{ .compatible = "maxim,max77759-nvmem", },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, max77759_nvmem_of_id);
+
+static const struct platform_device_id max77759_nvmem_platform_id[] = {
+	{ "max77759-nvmem", },
+	{ }
+};
+MODULE_DEVICE_TABLE(platform, max77759_nvmem_platform_id);
+
+static struct platform_driver max77759_nvmem_driver = {
+	.driver = {
+		.name = "max77759-nvmem",
+		.probe_type = PROBE_PREFER_ASYNCHRONOUS,
+		.of_match_table = max77759_nvmem_of_id,
+	},
+	.probe = max77759_nvmem_probe,
+	.id_table = max77759_nvmem_platform_id,
+};
+
+module_platform_driver(max77759_nvmem_driver);
+
+MODULE_AUTHOR("André Draszik <andre.draszik@linaro.org>");
+MODULE_DESCRIPTION("NVMEM driver for Maxim MAX77759");
+MODULE_LICENSE("GPL");