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, 74 insertions, 0 deletions

diff --git a/tools/include/nolibc/fcntl.h b/tools/include/nolibc/fcntl.h
new file mode 100644
index 000000000..d4b6af60d
--- /dev/null
+++ b/tools/include/nolibc/fcntl.h
@@ -0,0 +1,74 @@
+/* SPDX-License-Identifier: LGPL-2.1 OR MIT */
+/*
+ * fcntl definition for NOLIBC
+ * Copyright (C) 2017-2021 Willy Tarreau <w@1wt.eu>
+ */
+
+/* make sure to include all global symbols */
+#include "nolibc.h"
+
+#ifndef _NOLIBC_FCNTL_H
+#define _NOLIBC_FCNTL_H
+
+#include "arch.h"
+#include "types.h"
+#include "sys.h"
+
+#define __nolibc_open_flags(_flags) ((_flags) | O_LARGEFILE)
+
+#define __nolibc_open_mode(_flags)							\
+({											\
+	mode_t _mode;									\
+	va_list args;									\
+											\
+	va_start(args, (_flags));							\
+	_mode = va_arg(args, mode_t);							\
+	va_end(args);									\
+											\
+	_mode;										\
+})
+
+/*
+ * int openat(int dirfd, const char *path, int flags[, mode_t mode]);
+ */
+
+static __attribute__((unused))
+int _sys_openat(int dirfd, const char *path, int flags, mode_t mode)
+{
+	return __nolibc_syscall4(__NR_openat, dirfd, path, flags, mode);
+}
+
+static __attribute__((unused))
+int openat(int dirfd, const char *path, int flags, ...)
+{
+	return __sysret(_sys_openat(dirfd, path, __nolibc_open_flags(flags),
+						 __nolibc_open_mode(flags)));
+}
+
+/*
+ * int open(const char *path, int flags[, mode_t mode]);
+ */
+
+static __attribute__((unused))
+int _sys_open(const char *path, int flags, mode_t mode)
+{
+	return __nolibc_syscall4(__NR_openat, AT_FDCWD, path, flags, mode);
+}
+
+static __attribute__((unused))
+int open(const char *path, int flags, ...)
+{
+	return __sysret(_sys_open(path, __nolibc_open_flags(flags), __nolibc_open_mode(flags)));
+}
+
+/*
+ * int creat(const char *path, mode_t mode);
+ */
+
+static __attribute__((unused))
+int creat(const char *path, mode_t mode)
+{
+	return open(path, O_CREAT | O_WRONLY | O_TRUNC, mode);
+}
+
+#endif /* _NOLIBC_FCNTL_H */