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, 107 insertions, 0 deletions

diff --git a/drivers/auxdisplay/charlcd.h b/drivers/auxdisplay/charlcd.h
new file mode 100644
index 000000000..d10b89740
--- /dev/null
+++ b/drivers/auxdisplay/charlcd.h
@@ -0,0 +1,107 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * Character LCD driver for Linux
+ *
+ * Copyright (C) 2000-2008, Willy Tarreau <w@1wt.eu>
+ * Copyright (C) 2016-2017 Glider bvba
+ */
+
+#ifndef _CHARLCD_H
+#define _CHARLCD_H
+
+#define LCD_FLAG_B		0x0004	/* Blink on */
+#define LCD_FLAG_C		0x0008	/* Cursor on */
+#define LCD_FLAG_D		0x0010	/* Display on */
+#define LCD_FLAG_F		0x0020	/* Large font mode */
+#define LCD_FLAG_N		0x0040	/* 2-rows mode */
+#define LCD_FLAG_L		0x0080	/* Backlight enabled */
+
+enum charlcd_onoff {
+	CHARLCD_OFF = 0,
+	CHARLCD_ON,
+};
+
+enum charlcd_shift_dir {
+	CHARLCD_SHIFT_LEFT,
+	CHARLCD_SHIFT_RIGHT,
+};
+
+enum charlcd_fontsize {
+	CHARLCD_FONTSIZE_SMALL,
+	CHARLCD_FONTSIZE_LARGE,
+};
+
+enum charlcd_lines {
+	CHARLCD_LINES_1,
+	CHARLCD_LINES_2,
+};
+
+struct charlcd_ops;
+
+struct charlcd {
+	const struct charlcd_ops *ops;
+	const unsigned char *char_conv;	/* Optional */
+
+	int height;
+	int width;
+
+	/* Contains the LCD X and Y offset */
+	struct {
+		unsigned long x;
+		unsigned long y;
+	} addr;
+
+	void *drvdata;			/* Set by charlcd_alloc() */
+};
+
+/**
+ * struct charlcd_ops - Functions used by charlcd. Drivers have to implement
+ * these.
+ * @backlight: Turn backlight on or off. Optional.
+ * @print: Print one character to the display at current cursor position.
+ * The buffered cursor position is advanced by charlcd. The cursor should not
+ * wrap to the next line at the end of a line.
+ * @gotoxy: Set cursor to x, y. The x and y values to set the cursor to are
+ * previously set in addr.x and addr.y by charlcd.
+ * @home: Set cursor to 0, 0. The values in addr.x and addr.y are set to 0, 0 by
+ * charlcd prior to calling this function.
+ * @clear_display: Clear the whole display and set the cursor to 0, 0. The
+ * values in addr.x and addr.y are set to 0, 0 by charlcd after to calling this
+ * function.
+ * @init_display: Initialize the display.
+ * @shift_cursor: Shift cursor left or right one position.
+ * @shift_display: Shift whole display content left or right.
+ * @display: Turn display on or off.
+ * @cursor: Turn cursor on or off.
+ * @blink: Turn cursor blink on or off.
+ * @lines: One or two lines.
+ * @redefine_char: Redefine the actual pixel matrix of character.
+ */
+struct charlcd_ops {
+	void (*backlight)(struct charlcd *lcd, enum charlcd_onoff on);
+	int (*print)(struct charlcd *lcd, int c);
+	int (*gotoxy)(struct charlcd *lcd, unsigned int x, unsigned int y);
+	int (*home)(struct charlcd *lcd);
+	int (*clear_display)(struct charlcd *lcd);
+	int (*init_display)(struct charlcd *lcd);
+	int (*shift_cursor)(struct charlcd *lcd, enum charlcd_shift_dir dir);
+	int (*shift_display)(struct charlcd *lcd, enum charlcd_shift_dir dir);
+	int (*display)(struct charlcd *lcd, enum charlcd_onoff on);
+	int (*cursor)(struct charlcd *lcd, enum charlcd_onoff on);
+	int (*blink)(struct charlcd *lcd, enum charlcd_onoff on);
+	int (*fontsize)(struct charlcd *lcd, enum charlcd_fontsize size);
+	int (*lines)(struct charlcd *lcd, enum charlcd_lines lines);
+	int (*redefine_char)(struct charlcd *lcd, char *esc);
+};
+
+void charlcd_backlight(struct charlcd *lcd, enum charlcd_onoff on);
+
+struct charlcd *charlcd_alloc(unsigned int drvdata_size);
+void charlcd_free(struct charlcd *lcd);
+
+int charlcd_register(struct charlcd *lcd);
+int charlcd_unregister(struct charlcd *lcd);
+
+void charlcd_poke(struct charlcd *lcd);
+
+#endif /* CHARLCD_H */