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, 327 insertions, 0 deletions

diff --git a/drivers/auxdisplay/arm-charlcd.c b/drivers/auxdisplay/arm-charlcd.c
new file mode 100644
index 000000000..70efda4f7
--- /dev/null
+++ b/drivers/auxdisplay/arm-charlcd.c
@@ -0,0 +1,327 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Driver for the on-board character LCD found on some ARM reference boards
+ * This is basically an Hitachi HD44780 LCD with a custom IP block to drive it
+ * https://en.wikipedia.org/wiki/HD44780_Character_LCD
+ * Currently it will just display the text "ARM Linux" and the linux version
+ *
+ * Author: Linus Walleij <triad@df.lth.se>
+ */
+#include <linux/completion.h>
+#include <linux/container_of.h>
+#include <linux/delay.h>
+#include <linux/err.h>
+#include <linux/init.h>
+#include <linux/interrupt.h>
+#include <linux/iopoll.h>
+#include <linux/platform_device.h>
+#include <linux/string.h>
+#include <linux/types.h>
+#include <linux/workqueue.h>
+#include <generated/utsrelease.h>
+
+#define DRIVERNAME "arm-charlcd"
+#define CHARLCD_TIMEOUT (msecs_to_jiffies(1000))
+
+/* Offsets to registers */
+#define CHAR_COM	0x00U
+#define CHAR_DAT	0x04U
+#define CHAR_RD		0x08U
+#define CHAR_RAW	0x0CU
+#define CHAR_MASK	0x10U
+#define CHAR_STAT	0x14U
+
+#define CHAR_RAW_CLEAR	0x00000000U
+#define CHAR_RAW_VALID	0x00000100U
+
+/* Hitachi HD44780 display commands */
+#define HD_CLEAR			0x01U
+#define HD_HOME				0x02U
+#define HD_ENTRYMODE			0x04U
+#define HD_ENTRYMODE_INCREMENT		0x02U
+#define HD_ENTRYMODE_SHIFT		0x01U
+#define HD_DISPCTRL			0x08U
+#define HD_DISPCTRL_ON			0x04U
+#define HD_DISPCTRL_CURSOR_ON		0x02U
+#define HD_DISPCTRL_CURSOR_BLINK	0x01U
+#define HD_CRSR_SHIFT			0x10U
+#define HD_CRSR_SHIFT_DISPLAY		0x08U
+#define HD_CRSR_SHIFT_DISPLAY_RIGHT	0x04U
+#define HD_FUNCSET			0x20U
+#define HD_FUNCSET_8BIT			0x10U
+#define HD_FUNCSET_2_LINES		0x08U
+#define HD_FUNCSET_FONT_5X10		0x04U
+#define HD_SET_CGRAM			0x40U
+#define HD_SET_DDRAM			0x80U
+#define HD_BUSY_FLAG			0x80U
+
+/**
+ * struct charlcd - Private data structure
+ * @dev: a pointer back to containing device
+ * @virtbase: the offset to the controller in virtual memory
+ * @irq: reserved interrupt number
+ * @complete: completion structure for the last LCD command
+ * @init_work: delayed work structure to initialize the display on boot
+ */
+struct charlcd {
+	struct device *dev;
+	void __iomem *virtbase;
+	int irq;
+	struct completion complete;
+	struct delayed_work init_work;
+};
+
+static irqreturn_t charlcd_interrupt(int irq, void *data)
+{
+	struct charlcd *lcd = data;
+	u8 status;
+
+	status = readl(lcd->virtbase + CHAR_STAT) & 0x01;
+	/* Clear IRQ */
+	writel(CHAR_RAW_CLEAR, lcd->virtbase + CHAR_RAW);
+	if (status)
+		complete(&lcd->complete);
+	else
+		dev_info(lcd->dev, "Spurious IRQ (%02x)\n", status);
+	return IRQ_HANDLED;
+}
+
+
+static void charlcd_wait_complete_irq(struct charlcd *lcd)
+{
+	int ret;
+
+	ret = wait_for_completion_interruptible_timeout(&lcd->complete,
+							CHARLCD_TIMEOUT);
+	/* Disable IRQ after completion */
+	writel(0x00, lcd->virtbase + CHAR_MASK);
+
+	if (ret < 0) {
+		dev_err(lcd->dev,
+			"wait_for_completion_interruptible_timeout() returned %d waiting for ready\n",
+			ret);
+		return;
+	}
+
+	if (ret == 0) {
+		dev_err(lcd->dev, "charlcd controller timed out waiting for ready\n");
+		return;
+	}
+}
+
+static u8 charlcd_4bit_read_char(struct charlcd *lcd)
+{
+	u8 data;
+	u32 val;
+
+	/* If we can, use an IRQ to wait for the data, else poll */
+	if (lcd->irq >= 0)
+		charlcd_wait_complete_irq(lcd);
+	else {
+		udelay(100);
+		readl_poll_timeout_atomic(lcd->virtbase + CHAR_RAW, val,
+					  val & CHAR_RAW_VALID, 100, 1000);
+		writel(CHAR_RAW_CLEAR, lcd->virtbase + CHAR_RAW);
+	}
+	msleep(1);
+
+	/* Read the 4 high bits of the data */
+	data = readl(lcd->virtbase + CHAR_RD) & 0xf0;
+
+	/*
+	 * The second read for the low bits does not trigger an IRQ
+	 * so in this case we have to poll for the 4 lower bits
+	 */
+	udelay(100);
+	readl_poll_timeout_atomic(lcd->virtbase + CHAR_RAW, val,
+				  val & CHAR_RAW_VALID, 100, 1000);
+	writel(CHAR_RAW_CLEAR, lcd->virtbase + CHAR_RAW);
+	msleep(1);
+
+	/* Read the 4 low bits of the data */
+	data |= (readl(lcd->virtbase + CHAR_RD) >> 4) & 0x0f;
+
+	return data;
+}
+
+static bool charlcd_4bit_read_bf(struct charlcd *lcd)
+{
+	if (lcd->irq >= 0) {
+		/*
+		 * If we'll use IRQs to wait for the busyflag, clear any
+		 * pending flag and enable IRQ
+		 */
+		writel(CHAR_RAW_CLEAR, lcd->virtbase + CHAR_RAW);
+		init_completion(&lcd->complete);
+		writel(0x01, lcd->virtbase + CHAR_MASK);
+	}
+	readl(lcd->virtbase + CHAR_COM);
+
+	return charlcd_4bit_read_char(lcd) & HD_BUSY_FLAG;
+}
+
+static void charlcd_4bit_wait_busy(struct charlcd *lcd)
+{
+	int retries = 50;
+
+	udelay(100);
+	while (charlcd_4bit_read_bf(lcd) && retries)
+		retries--;
+	if (!retries)
+		dev_err(lcd->dev, "timeout waiting for busyflag\n");
+}
+
+static void charlcd_4bit_command(struct charlcd *lcd, u8 cmd)
+{
+	u32 cmdlo = (cmd << 4) & 0xf0;
+	u32 cmdhi = (cmd & 0xf0);
+
+	writel(cmdhi, lcd->virtbase + CHAR_COM);
+	udelay(10);
+	writel(cmdlo, lcd->virtbase + CHAR_COM);
+	charlcd_4bit_wait_busy(lcd);
+}
+
+static void charlcd_4bit_char(struct charlcd *lcd, u8 ch)
+{
+	u32 chlo = (ch << 4) & 0xf0;
+	u32 chhi = (ch & 0xf0);
+
+	writel(chhi, lcd->virtbase + CHAR_DAT);
+	udelay(10);
+	writel(chlo, lcd->virtbase + CHAR_DAT);
+	charlcd_4bit_wait_busy(lcd);
+}
+
+static void charlcd_4bit_print(struct charlcd *lcd, int line, const char *str)
+{
+	u8 offset;
+	int i;
+
+	/*
+	 * We support line 0, 1
+	 * Line 1 runs from 0x00..0x27
+	 * Line 2 runs from 0x28..0x4f
+	 */
+	if (line == 0)
+		offset = 0;
+	else if (line == 1)
+		offset = 0x28;
+	else
+		return;
+
+	/* Set offset */
+	charlcd_4bit_command(lcd, HD_SET_DDRAM | offset);
+
+	/* Send string */
+	for (i = 0; i < strlen(str) && i < 0x28; i++)
+		charlcd_4bit_char(lcd, str[i]);
+}
+
+static void charlcd_4bit_init(struct charlcd *lcd)
+{
+	/* These commands cannot be checked with the busy flag */
+	writel(HD_FUNCSET | HD_FUNCSET_8BIT, lcd->virtbase + CHAR_COM);
+	msleep(5);
+	writel(HD_FUNCSET | HD_FUNCSET_8BIT, lcd->virtbase + CHAR_COM);
+	udelay(100);
+	writel(HD_FUNCSET | HD_FUNCSET_8BIT, lcd->virtbase + CHAR_COM);
+	udelay(100);
+	/* Go to 4bit mode */
+	writel(HD_FUNCSET, lcd->virtbase + CHAR_COM);
+	udelay(100);
+	/*
+	 * 4bit mode, 2 lines, 5x8 font, after this the number of lines
+	 * and the font cannot be changed until the next initialization sequence
+	 */
+	charlcd_4bit_command(lcd, HD_FUNCSET | HD_FUNCSET_2_LINES);
+	charlcd_4bit_command(lcd, HD_DISPCTRL | HD_DISPCTRL_ON);
+	charlcd_4bit_command(lcd, HD_ENTRYMODE | HD_ENTRYMODE_INCREMENT);
+	charlcd_4bit_command(lcd, HD_CLEAR);
+	charlcd_4bit_command(lcd, HD_HOME);
+	/* Put something useful in the display */
+	charlcd_4bit_print(lcd, 0, "ARM Linux");
+	charlcd_4bit_print(lcd, 1, UTS_RELEASE);
+}
+
+static void charlcd_init_work(struct work_struct *work)
+{
+	struct charlcd *lcd =
+		container_of(work, struct charlcd, init_work.work);
+
+	charlcd_4bit_init(lcd);
+}
+
+static int __init charlcd_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	int ret;
+	struct charlcd *lcd;
+
+	lcd = devm_kzalloc(dev, sizeof(*lcd), GFP_KERNEL);
+	if (!lcd)
+		return -ENOMEM;
+
+	lcd->dev = &pdev->dev;
+
+	lcd->virtbase = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(lcd->virtbase))
+		return PTR_ERR(lcd->virtbase);
+
+	lcd->irq = platform_get_irq(pdev, 0);
+	/* If no IRQ is supplied, we'll survive without it */
+	if (lcd->irq >= 0) {
+		ret = devm_request_irq(dev, lcd->irq, charlcd_interrupt, 0, DRIVERNAME, lcd);
+		if (ret)
+			return ret;
+	}
+
+	platform_set_drvdata(pdev, lcd);
+
+	/*
+	 * Initialize the display in a delayed work, because
+	 * it is VERY slow and would slow down the boot of the system.
+	 */
+	INIT_DELAYED_WORK(&lcd->init_work, charlcd_init_work);
+	schedule_delayed_work(&lcd->init_work, 0);
+
+	return 0;
+}
+
+static int charlcd_suspend(struct device *dev)
+{
+	struct charlcd *lcd = dev_get_drvdata(dev);
+
+	/* Power the display off */
+	charlcd_4bit_command(lcd, HD_DISPCTRL);
+	return 0;
+}
+
+static int charlcd_resume(struct device *dev)
+{
+	struct charlcd *lcd = dev_get_drvdata(dev);
+
+	/* Turn the display back on */
+	charlcd_4bit_command(lcd, HD_DISPCTRL | HD_DISPCTRL_ON);
+	return 0;
+}
+
+static const struct dev_pm_ops charlcd_pm_ops = {
+	.suspend = charlcd_suspend,
+	.resume = charlcd_resume,
+};
+
+static const struct of_device_id charlcd_match[] = {
+	{ .compatible = "arm,versatile-lcd", },
+	{}
+};
+
+static struct platform_driver charlcd_driver = {
+	.driver = {
+		.name = DRIVERNAME,
+		.pm = &charlcd_pm_ops,
+		.suppress_bind_attrs = true,
+		.of_match_table = charlcd_match,
+	},
+};
+builtin_platform_driver_probe(charlcd_driver, charlcd_probe);