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, 344 insertions, 0 deletions

diff --git a/drivers/auxdisplay/hd44780.c b/drivers/auxdisplay/hd44780.c
new file mode 100644
index 000000000..3383d2fcf
--- /dev/null
+++ b/drivers/auxdisplay/hd44780.c
@@ -0,0 +1,344 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * HD44780 Character LCD driver for Linux
+ *
+ * Copyright (C) 2000-2008, Willy Tarreau <w@1wt.eu>
+ * Copyright (C) 2016-2017 Glider bvba
+ */
+
+#include <linux/delay.h>
+#include <linux/gpio/consumer.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/property.h>
+#include <linux/slab.h>
+
+#include "charlcd.h"
+#include "hd44780_common.h"
+
+enum hd44780_pin {
+	/* Order does matter due to writing to GPIO array subsets! */
+	PIN_DATA0,	/* Optional */
+	PIN_DATA1,	/* Optional */
+	PIN_DATA2,	/* Optional */
+	PIN_DATA3,	/* Optional */
+	PIN_DATA4,
+	PIN_DATA5,
+	PIN_DATA6,
+	PIN_DATA7,
+	PIN_CTRL_RS,
+	PIN_CTRL_RW,	/* Optional */
+	PIN_CTRL_E,
+	PIN_CTRL_BL,   /* Optional */
+	PIN_NUM
+};
+
+struct hd44780 {
+	struct gpio_desc *pins[PIN_NUM];
+};
+
+static void hd44780_backlight(struct charlcd *lcd, enum charlcd_onoff on)
+{
+	struct hd44780_common *hdc = lcd->drvdata;
+	struct hd44780 *hd = hdc->hd44780;
+
+	if (hd->pins[PIN_CTRL_BL])
+		gpiod_set_value_cansleep(hd->pins[PIN_CTRL_BL], on);
+}
+
+static void hd44780_strobe_gpio(struct hd44780 *hd)
+{
+	/* Maintain the data during 20 us before the strobe */
+	udelay(20);
+
+	gpiod_set_value_cansleep(hd->pins[PIN_CTRL_E], 1);
+
+	/* Maintain the strobe during 40 us */
+	udelay(40);
+
+	gpiod_set_value_cansleep(hd->pins[PIN_CTRL_E], 0);
+}
+
+/* write to an LCD panel register in 8 bit GPIO mode */
+static void hd44780_write_gpio8(struct hd44780 *hd, u8 val, unsigned int rs)
+{
+	DECLARE_BITMAP(values, 10); /* for DATA[0-7], RS, RW */
+	unsigned int n;
+
+	values[0] = val;
+	__assign_bit(8, values, rs);
+	n = hd->pins[PIN_CTRL_RW] ? 10 : 9;
+
+	/* Present the data to the port */
+	gpiod_set_array_value_cansleep(n, &hd->pins[PIN_DATA0], NULL, values);
+
+	hd44780_strobe_gpio(hd);
+}
+
+/* write to an LCD panel register in 4 bit GPIO mode */
+static void hd44780_write_gpio4(struct hd44780 *hd, u8 val, unsigned int rs)
+{
+	DECLARE_BITMAP(values, 6); /* for DATA[4-7], RS, RW */
+	unsigned int n;
+
+	/* High nibble + RS, RW */
+	values[0] = val >> 4;
+	__assign_bit(4, values, rs);
+	n = hd->pins[PIN_CTRL_RW] ? 6 : 5;
+
+	/* Present the data to the port */
+	gpiod_set_array_value_cansleep(n, &hd->pins[PIN_DATA4], NULL, values);
+
+	hd44780_strobe_gpio(hd);
+
+	/* Low nibble */
+	values[0] &= ~0x0fUL;
+	values[0] |= val & 0x0f;
+
+	/* Present the data to the port */
+	gpiod_set_array_value_cansleep(n, &hd->pins[PIN_DATA4], NULL, values);
+
+	hd44780_strobe_gpio(hd);
+}
+
+/* Send a command to the LCD panel in 8 bit GPIO mode */
+static void hd44780_write_cmd_gpio8(struct hd44780_common *hdc, int cmd)
+{
+	struct hd44780 *hd = hdc->hd44780;
+
+	hd44780_write_gpio8(hd, cmd, 0);
+
+	/* The shortest command takes at least 120 us */
+	udelay(120);
+}
+
+/* Send data to the LCD panel in 8 bit GPIO mode */
+static void hd44780_write_data_gpio8(struct hd44780_common *hdc, int data)
+{
+	struct hd44780 *hd = hdc->hd44780;
+
+	hd44780_write_gpio8(hd, data, 1);
+
+	/* The shortest data takes at least 45 us */
+	udelay(45);
+}
+
+static const struct charlcd_ops hd44780_ops_gpio8 = {
+	.backlight	= hd44780_backlight,
+	.print		= hd44780_common_print,
+	.gotoxy		= hd44780_common_gotoxy,
+	.home		= hd44780_common_home,
+	.clear_display	= hd44780_common_clear_display,
+	.init_display	= hd44780_common_init_display,
+	.shift_cursor	= hd44780_common_shift_cursor,
+	.shift_display	= hd44780_common_shift_display,
+	.display	= hd44780_common_display,
+	.cursor		= hd44780_common_cursor,
+	.blink		= hd44780_common_blink,
+	.fontsize	= hd44780_common_fontsize,
+	.lines		= hd44780_common_lines,
+	.redefine_char	= hd44780_common_redefine_char,
+};
+
+/* Send a command to the LCD panel in 4 bit GPIO mode */
+static void hd44780_write_cmd_gpio4(struct hd44780_common *hdc, int cmd)
+{
+	struct hd44780 *hd = hdc->hd44780;
+
+	hd44780_write_gpio4(hd, cmd, 0);
+
+	/* The shortest command takes at least 120 us */
+	udelay(120);
+}
+
+/* Send 4-bits of a command to the LCD panel in raw 4 bit GPIO mode */
+static void hd44780_write_cmd_raw_gpio4(struct hd44780_common *hdc, int cmd)
+{
+	DECLARE_BITMAP(values, 6); /* for DATA[4-7], RS, RW */
+	struct hd44780 *hd = hdc->hd44780;
+	unsigned int n;
+
+	/* Command nibble + RS, RW */
+	values[0] = cmd & 0x0f;
+	n = hd->pins[PIN_CTRL_RW] ? 6 : 5;
+
+	/* Present the data to the port */
+	gpiod_set_array_value_cansleep(n, &hd->pins[PIN_DATA4], NULL, values);
+
+	hd44780_strobe_gpio(hd);
+}
+
+/* Send data to the LCD panel in 4 bit GPIO mode */
+static void hd44780_write_data_gpio4(struct hd44780_common *hdc, int data)
+{
+	struct hd44780 *hd = hdc->hd44780;
+
+	hd44780_write_gpio4(hd, data, 1);
+
+	/* The shortest data takes at least 45 us */
+	udelay(45);
+}
+
+static const struct charlcd_ops hd44780_ops_gpio4 = {
+	.backlight	= hd44780_backlight,
+	.print		= hd44780_common_print,
+	.gotoxy		= hd44780_common_gotoxy,
+	.home		= hd44780_common_home,
+	.clear_display	= hd44780_common_clear_display,
+	.init_display	= hd44780_common_init_display,
+	.shift_cursor	= hd44780_common_shift_cursor,
+	.shift_display	= hd44780_common_shift_display,
+	.display	= hd44780_common_display,
+	.cursor		= hd44780_common_cursor,
+	.blink		= hd44780_common_blink,
+	.fontsize	= hd44780_common_fontsize,
+	.lines		= hd44780_common_lines,
+	.redefine_char	= hd44780_common_redefine_char,
+};
+
+static int hd44780_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	unsigned int i, base;
+	struct charlcd *lcd;
+	struct hd44780_common *hdc;
+	struct hd44780 *hd;
+	int ifwidth, ret = -ENOMEM;
+
+	/* Required pins */
+	ifwidth = gpiod_count(dev, "data");
+	if (ifwidth < 0)
+		return ifwidth;
+
+	switch (ifwidth) {
+	case 4:
+		base = PIN_DATA4;
+		break;
+	case 8:
+		base = PIN_DATA0;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	lcd = hd44780_common_alloc();
+	if (!lcd)
+		return -ENOMEM;
+
+	hd = kzalloc_obj(*hd);
+	if (!hd)
+		goto fail2;
+
+	hdc = lcd->drvdata;
+	hdc->hd44780 = hd;
+
+	for (i = 0; i < ifwidth; i++) {
+		hd->pins[base + i] = devm_gpiod_get_index(dev, "data", i,
+							  GPIOD_OUT_LOW);
+		if (IS_ERR(hd->pins[base + i])) {
+			ret = PTR_ERR(hd->pins[base + i]);
+			goto fail3;
+		}
+	}
+
+	hd->pins[PIN_CTRL_E] = devm_gpiod_get(dev, "enable", GPIOD_OUT_LOW);
+	if (IS_ERR(hd->pins[PIN_CTRL_E])) {
+		ret = PTR_ERR(hd->pins[PIN_CTRL_E]);
+		goto fail3;
+	}
+
+	hd->pins[PIN_CTRL_RS] = devm_gpiod_get(dev, "rs", GPIOD_OUT_HIGH);
+	if (IS_ERR(hd->pins[PIN_CTRL_RS])) {
+		ret = PTR_ERR(hd->pins[PIN_CTRL_RS]);
+		goto fail3;
+	}
+
+	/* Optional pins */
+	hd->pins[PIN_CTRL_RW] = devm_gpiod_get_optional(dev, "rw",
+							GPIOD_OUT_LOW);
+	if (IS_ERR(hd->pins[PIN_CTRL_RW])) {
+		ret = PTR_ERR(hd->pins[PIN_CTRL_RW]);
+		goto fail3;
+	}
+
+	hd->pins[PIN_CTRL_BL] = devm_gpiod_get_optional(dev, "backlight",
+							GPIOD_OUT_LOW);
+	if (IS_ERR(hd->pins[PIN_CTRL_BL])) {
+		ret = PTR_ERR(hd->pins[PIN_CTRL_BL]);
+		goto fail3;
+	}
+
+	/* Required properties */
+	ret = device_property_read_u32(dev, "display-height-chars",
+				       &lcd->height);
+	if (ret)
+		goto fail3;
+	ret = device_property_read_u32(dev, "display-width-chars", &lcd->width);
+	if (ret)
+		goto fail3;
+
+	/*
+	 * On displays with more than two rows, the internal buffer width is
+	 * usually equal to the display width
+	 */
+	if (lcd->height > 2)
+		hdc->bwidth = lcd->width;
+
+	/* Optional properties */
+	device_property_read_u32(dev, "internal-buffer-width", &hdc->bwidth);
+
+	hdc->ifwidth = ifwidth;
+	if (ifwidth == 8) {
+		lcd->ops = &hd44780_ops_gpio8;
+		hdc->write_data = hd44780_write_data_gpio8;
+		hdc->write_cmd = hd44780_write_cmd_gpio8;
+	} else {
+		lcd->ops = &hd44780_ops_gpio4;
+		hdc->write_data = hd44780_write_data_gpio4;
+		hdc->write_cmd = hd44780_write_cmd_gpio4;
+		hdc->write_cmd_raw4 = hd44780_write_cmd_raw_gpio4;
+	}
+
+	ret = charlcd_register(lcd);
+	if (ret)
+		goto fail3;
+
+	platform_set_drvdata(pdev, lcd);
+	return 0;
+
+fail3:
+	kfree(hd);
+fail2:
+	hd44780_common_free(lcd);
+	return ret;
+}
+
+static void hd44780_remove(struct platform_device *pdev)
+{
+	struct charlcd *lcd = platform_get_drvdata(pdev);
+	struct hd44780_common *hdc = lcd->drvdata;
+
+	charlcd_unregister(lcd);
+	kfree(hdc->hd44780);
+	hd44780_common_free(lcd);
+}
+
+static const struct of_device_id hd44780_of_match[] = {
+	{ .compatible = "hit,hd44780" },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, hd44780_of_match);
+
+static struct platform_driver hd44780_driver = {
+	.probe = hd44780_probe,
+	.remove = hd44780_remove,
+	.driver		= {
+		.name	= "hd44780",
+		.of_match_table = hd44780_of_match,
+	},
+};
+
+module_platform_driver(hd44780_driver);
+MODULE_DESCRIPTION("HD44780 Character LCD driver");
+MODULE_AUTHOR("Geert Uytterhoeven <geert@linux-m68k.org>");
+MODULE_LICENSE("GPL");