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, 70 insertions, 0 deletions

diff --git a/Documentation/admin-guide/mono.rst b/Documentation/admin-guide/mono.rst
new file mode 100644
index 000000000..c6dab5680
--- /dev/null
+++ b/Documentation/admin-guide/mono.rst
@@ -0,0 +1,70 @@
+Mono(tm) Binary Kernel Support for Linux
+-----------------------------------------
+
+To configure Linux to automatically execute Mono-based .NET binaries
+(in the form of .exe files) without the need to use the mono CLR
+wrapper, you can use the BINFMT_MISC kernel support.
+
+This will allow you to execute Mono-based .NET binaries just like any
+other program after you have done the following:
+
+1) You MUST FIRST install the Mono CLR support, either by downloading
+   a binary package, a source tarball or by installing from Git. Binary
+   packages for several distributions can be found at:
+
+	https://www.mono-project.com/download/
+
+   Instructions for compiling Mono can be found at:
+
+	https://www.mono-project.com/docs/compiling-mono/linux/
+
+   Once the Mono CLR support has been installed, just check that
+   ``/usr/bin/mono`` (which could be located elsewhere, for example
+   ``/usr/local/bin/mono``) is working.
+
+2) You have to compile BINFMT_MISC either as a module or into
+   the kernel (``CONFIG_BINFMT_MISC``) and set it up properly.
+   If you choose to compile it as a module, you will have
+   to insert it manually with modprobe/insmod, as kmod
+   cannot be easily supported with binfmt_misc.
+   Read the file ``binfmt_misc.txt`` in this directory to know
+   more about the configuration process.
+
+3) Add the following entries to ``/etc/rc.local`` or similar script
+   to be run at system startup:
+
+   .. code-block:: sh
+
+    # Insert BINFMT_MISC module into the kernel
+    if [ ! -e /proc/sys/fs/binfmt_misc/register ]; then
+        /sbin/modprobe binfmt_misc
+	# Some distributions, like Fedora Core, perform
+	# the following command automatically when the
+	# binfmt_misc module is loaded into the kernel
+	# or during normal boot up (systemd-based systems).
+	# Thus, it is possible that the following line
+	# is not needed at all.
+	mount -t binfmt_misc none /proc/sys/fs/binfmt_misc
+    fi
+
+    # Register support for .NET CLR binaries
+    if [ -e /proc/sys/fs/binfmt_misc/register ]; then
+	# Replace /usr/bin/mono with the correct pathname to
+	# the Mono CLR runtime (usually /usr/local/bin/mono
+	# when compiling from sources or CVS).
+        echo ':CLR:M::MZ::/usr/bin/mono:' > /proc/sys/fs/binfmt_misc/register
+    else
+        echo "No binfmt_misc support"
+        exit 1
+    fi
+
+4) Check that ``.exe`` binaries can be ran without the need of a
+   wrapper script, simply by launching the ``.exe`` file directly
+   from a command prompt, for example::
+
+	/usr/bin/xsd.exe
+
+   .. note::
+
+      If this fails with a permission denied error, check
+      that the ``.exe`` file has execute permissions.