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, 111 insertions, 0 deletions

diff --git a/arch/m68k/lib/modsi3.S b/arch/m68k/lib/modsi3.S
new file mode 100644
index 000000000..1bcb742d0
--- /dev/null
+++ b/arch/m68k/lib/modsi3.S
@@ -0,0 +1,111 @@
+/* libgcc1 routines for 68000 w/o floating-point hardware.
+   Copyright (C) 1994, 1996, 1997, 1998 Free Software Foundation, Inc.
+
+This file is part of GNU CC.
+
+GNU CC is free software; you can redistribute it and/or modify it
+under the terms of the GNU General Public License as published by the
+Free Software Foundation; either version 2, or (at your option) any
+later version.
+
+In addition to the permissions in the GNU General Public License, the
+Free Software Foundation gives you unlimited permission to link the
+compiled version of this file with other programs, and to distribute
+those programs without any restriction coming from the use of this
+file.  (The General Public License restrictions do apply in other
+respects; for example, they cover modification of the file, and
+distribution when not linked into another program.)
+
+This file is distributed in the hope that it will be useful, but
+WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+General Public License for more details. */
+
+/* As a special exception, if you link this library with files
+   compiled with GCC to produce an executable, this does not cause
+   the resulting executable to be covered by the GNU General Public License.
+   This exception does not however invalidate any other reasons why
+   the executable file might be covered by the GNU General Public License.  */
+
+/* Use this one for any 680x0; assumes no floating point hardware.
+   The trailing " '" appearing on some lines is for ANSI preprocessors.  Yuk.
+   Some of this code comes from MINIX, via the folks at ericsson.
+   D. V. Henkel-Wallace (gumby@cygnus.com) Fete Bastille, 1992
+*/
+
+#include <linux/export.h>
+
+/* These are predefined by new versions of GNU cpp.  */
+
+#ifndef __USER_LABEL_PREFIX__
+#define __USER_LABEL_PREFIX__ _
+#endif
+
+#ifndef __REGISTER_PREFIX__
+#define __REGISTER_PREFIX__
+#endif
+
+#ifndef __IMMEDIATE_PREFIX__
+#define __IMMEDIATE_PREFIX__ #
+#endif
+
+/* ANSI concatenation macros.  */
+
+#define CONCAT1(a, b) CONCAT2(a, b)
+#define CONCAT2(a, b) a ## b
+
+/* Use the right prefix for global labels.  */
+
+#define SYM(x) CONCAT1 (__USER_LABEL_PREFIX__, x)
+
+/* Use the right prefix for registers.  */
+
+#define REG(x) CONCAT1 (__REGISTER_PREFIX__, x)
+
+/* Use the right prefix for immediate values.  */
+
+#define IMM(x) CONCAT1 (__IMMEDIATE_PREFIX__, x)
+
+#define d0 REG (d0)
+#define d1 REG (d1)
+#define d2 REG (d2)
+#define d3 REG (d3)
+#define d4 REG (d4)
+#define d5 REG (d5)
+#define d6 REG (d6)
+#define d7 REG (d7)
+#define a0 REG (a0)
+#define a1 REG (a1)
+#define a2 REG (a2)
+#define a3 REG (a3)
+#define a4 REG (a4)
+#define a5 REG (a5)
+#define a6 REG (a6)
+#define fp REG (fp)
+#define sp REG (sp)
+
+	.text
+	.proc
+	.globl	SYM (__modsi3)
+SYM (__modsi3):
+	movel	sp@(8), d1	/* d1 = divisor */
+	movel	sp@(4), d0	/* d0 = dividend */
+	movel	d1, sp@-
+	movel	d0, sp@-
+	jbsr	SYM (__divsi3)
+	addql	IMM (8), sp
+	movel	sp@(8), d1	/* d1 = divisor */
+#if !(defined(__mcf5200__) || defined(__mcoldfire__))
+	movel	d1, sp@-
+	movel	d0, sp@-
+	jbsr	SYM (__mulsi3)	/* d0 = (a/b)*b */
+	addql	IMM (8), sp
+#else
+	mulsl	d1,d0
+#endif
+	movel	sp@(4), d1	/* d1 = dividend */
+	subl	d0, d1		/* d1 = a - (a/b)*b */
+	movel	d1, d0
+	rts
+
+	EXPORT_SYMBOL(__modsi3)