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, 175 insertions, 0 deletions

diff --git a/drivers/nfc/s3fwrn5/uart.c b/drivers/nfc/s3fwrn5/uart.c
new file mode 100644
index 000000000..8f142a255
--- /dev/null
+++ b/drivers/nfc/s3fwrn5/uart.c
@@ -0,0 +1,175 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * UART Link Layer for S3FWRN82 NCI based Driver
+ *
+ * Copyright (C) 2015 Samsung Electronics
+ * Robert Baldyga <r.baldyga@samsung.com>
+ * Copyright (C) 2020 Samsung Electronics
+ * Bongsu Jeon <bongsu.jeon@samsung.com>
+ */
+
+#include <linux/device.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/nfc.h>
+#include <linux/netdevice.h>
+#include <linux/serdev.h>
+#include <linux/gpio/consumer.h>
+
+#include "phy_common.h"
+
+#define S3FWRN82_NCI_HEADER 3
+#define S3FWRN82_NCI_IDX 2
+#define NCI_SKB_BUFF_LEN 258
+
+struct s3fwrn82_uart_phy {
+	struct phy_common common;
+	struct serdev_device *ser_dev;
+	struct sk_buff *recv_skb;
+};
+
+static int s3fwrn82_uart_write(void *phy_id, struct sk_buff *out)
+{
+	struct s3fwrn82_uart_phy *phy = phy_id;
+	int err;
+
+	err = serdev_device_write(phy->ser_dev,
+				  out->data, out->len,
+				  MAX_SCHEDULE_TIMEOUT);
+	if (err < 0)
+		return err;
+
+	return 0;
+}
+
+static const struct s3fwrn5_phy_ops uart_phy_ops = {
+	.set_wake = s3fwrn5_phy_set_wake,
+	.set_mode = s3fwrn5_phy_set_mode,
+	.get_mode = s3fwrn5_phy_get_mode,
+	.write = s3fwrn82_uart_write,
+};
+
+static size_t s3fwrn82_uart_read(struct serdev_device *serdev,
+				 const u8 *data, size_t count)
+{
+	struct s3fwrn82_uart_phy *phy = serdev_device_get_drvdata(serdev);
+	size_t i;
+
+	for (i = 0; i < count; i++) {
+		if (!phy->recv_skb) {
+			phy->recv_skb = alloc_skb(NCI_SKB_BUFF_LEN, GFP_KERNEL);
+			if (!phy->recv_skb)
+				return i;
+		}
+
+		skb_put_u8(phy->recv_skb, *data++);
+
+		if (phy->recv_skb->len < S3FWRN82_NCI_HEADER)
+			continue;
+
+		if ((phy->recv_skb->len - S3FWRN82_NCI_HEADER)
+				< phy->recv_skb->data[S3FWRN82_NCI_IDX])
+			continue;
+
+		s3fwrn5_recv_frame(phy->common.ndev, phy->recv_skb,
+				   phy->common.mode);
+		phy->recv_skb = NULL;
+	}
+
+	return i;
+}
+
+static const struct serdev_device_ops s3fwrn82_serdev_ops = {
+	.receive_buf = s3fwrn82_uart_read,
+	.write_wakeup = serdev_device_write_wakeup,
+};
+
+static const struct of_device_id s3fwrn82_uart_of_match[] = {
+	{ .compatible = "samsung,s3fwrn82" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, s3fwrn82_uart_of_match);
+
+static int s3fwrn82_uart_probe(struct serdev_device *serdev)
+{
+	struct s3fwrn82_uart_phy *phy;
+	int ret = -ENOMEM;
+
+	phy = devm_kzalloc(&serdev->dev, sizeof(*phy), GFP_KERNEL);
+	if (!phy)
+		goto err_exit;
+
+	phy->recv_skb = alloc_skb(NCI_SKB_BUFF_LEN, GFP_KERNEL);
+	if (!phy->recv_skb)
+		goto err_exit;
+
+	mutex_init(&phy->common.mutex);
+	phy->common.mode = S3FWRN5_MODE_COLD;
+
+	phy->ser_dev = serdev;
+	serdev_device_set_drvdata(serdev, phy);
+	serdev_device_set_client_ops(serdev, &s3fwrn82_serdev_ops);
+	ret = serdev_device_open(serdev);
+	if (ret) {
+		dev_err(&serdev->dev, "Unable to open device\n");
+		goto err_skb;
+	}
+
+	ret = serdev_device_set_baudrate(serdev, 115200);
+	if (ret != 115200) {
+		ret = -EINVAL;
+		goto err_serdev;
+	}
+
+	serdev_device_set_flow_control(serdev, false);
+
+	phy->common.gpio_en = devm_gpiod_get(&serdev->dev, "en", GPIOD_OUT_HIGH);
+	if (IS_ERR(phy->common.gpio_en)) {
+		ret = PTR_ERR(phy->common.gpio_en);
+		goto err_serdev;
+	}
+
+	phy->common.gpio_fw_wake = devm_gpiod_get(&serdev->dev, "wake", GPIOD_OUT_LOW);
+	if (IS_ERR(phy->common.gpio_fw_wake)) {
+		ret = PTR_ERR(phy->common.gpio_fw_wake);
+		goto err_serdev;
+	}
+
+	ret = s3fwrn5_probe(&phy->common.ndev, phy, &phy->ser_dev->dev,
+			    &uart_phy_ops);
+	if (ret < 0)
+		goto err_serdev;
+
+	return ret;
+
+err_serdev:
+	serdev_device_close(serdev);
+err_skb:
+	kfree_skb(phy->recv_skb);
+err_exit:
+	return ret;
+}
+
+static void s3fwrn82_uart_remove(struct serdev_device *serdev)
+{
+	struct s3fwrn82_uart_phy *phy = serdev_device_get_drvdata(serdev);
+
+	s3fwrn5_remove(phy->common.ndev);
+	serdev_device_close(serdev);
+	kfree_skb(phy->recv_skb);
+}
+
+static struct serdev_device_driver s3fwrn82_uart_driver = {
+	.probe = s3fwrn82_uart_probe,
+	.remove = s3fwrn82_uart_remove,
+	.driver = {
+		.name = "s3fwrn82_uart",
+		.of_match_table = s3fwrn82_uart_of_match,
+	},
+};
+
+module_serdev_device_driver(s3fwrn82_uart_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("UART driver for Samsung NFC");
+MODULE_AUTHOR("Bongsu Jeon <bongsu.jeon@samsung.com>");