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, 96 insertions, 0 deletions

diff --git a/Documentation/tee/qtee.rst b/Documentation/tee/qtee.rst
new file mode 100644
index 000000000..2fa2c1bf6
--- /dev/null
+++ b/Documentation/tee/qtee.rst
@@ -0,0 +1,96 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+=============================================
+QTEE (Qualcomm Trusted Execution Environment)
+=============================================
+
+The QTEE driver handles communication with Qualcomm TEE [1].
+
+The lowest level of communication with QTEE builds on the ARM SMC Calling
+Convention (SMCCC) [2], which is the foundation for QTEE's Secure Channel
+Manager (SCM) [3] used internally by the driver.
+
+In a QTEE-based system, services are represented as objects with a series of
+operations that can be called to produce results, including other objects.
+
+When an object is hosted within QTEE, executing its operations is referred
+to as "direct invocation". QTEE can also invoke objects hosted in the non-secure
+world using a method known as "callback request".
+
+The SCM provides two functions to support direct invocation and callback requests:
+
+- QCOM_SCM_SMCINVOKE_INVOKE: Used for direct invocation. It can return either
+  a result or initiate a callback request.
+- QCOM_SCM_SMCINVOKE_CB_RSP: Used to submit a response to a callback request
+  triggered by a previous direct invocation.
+
+The QTEE Transport Message [4] is stacked on top of the SCM driver functions.
+
+A message consists of two buffers shared with QTEE: inbound and outbound
+buffers. The inbound buffer is used for direct invocation, and the outbound
+buffer is used to make callback requests. This picture shows the contents of
+a QTEE transport message::
+
+                                      +---------------------+
+                                      |                     v
+    +-----------------+-------+-------+------+--------------------------+
+    | qcomtee_msg_    |object | buffer       |                          |
+    |  object_invoke  |  id   | offset, size |                          | (inbound buffer)
+    +-----------------+-------+--------------+--------------------------+
+    <---- header -----><---- arguments ------><- in/out buffer payload ->
+
+                                      +-----------+
+                                      |           v
+    +-----------------+-------+-------+------+----------------------+
+    | qcomtee_msg_    |object | buffer       |                      |
+    |  callback       |  id   | offset, size |                      | (outbound buffer)
+    +-----------------+-------+--------------+----------------------+
+
+Each buffer is started with a header and array of arguments.
+
+QTEE Transport Message supports four types of arguments:
+
+- Input Object (IO) is an object parameter to the current invocation
+  or callback request.
+- Output Object (OO) is an object parameter from the current invocation
+  or callback request.
+- Input Buffer (IB) is (offset, size) pair to the inbound or outbound region
+  to store parameter to the current invocation or callback request.
+- Output Buffer (OB) is (offset, size) pair to the inbound or outbound region
+  to store parameter from the current invocation or callback request.
+
+Picture of the relationship between the different components in the QTEE
+architecture::
+
+         User space               Kernel                     Secure world
+         ~~~~~~~~~~               ~~~~~~                     ~~~~~~~~~~~~
+   +--------+   +----------+                                +--------------+
+   | Client |   |callback  |                                | Trusted      |
+   +--------+   |server    |                                | Application  |
+      /\        +----------+                                +--------------+
+      ||  +----------+ /\                                          /\
+      ||  |callback  | ||                                          ||
+      ||  |server    | ||                                          \/
+      ||  +----------+ ||                                   +--------------+
+      ||       /\      ||                                   | TEE Internal |
+      ||       ||      ||                                   | API          |
+      \/       \/      \/   +--------+--------+             +--------------+
+   +---------------------+  | TEE    | QTEE   |             | QTEE         |
+   |   libqcomtee [5]    |  | subsys | driver |             | Trusted OS   |
+   +-------+-------------+--+----+-------+----+-------------+--------------+
+   |      Generic TEE API        |       |   QTEE MSG                      |
+   |      IOCTL (TEE_IOC_*)      |       |   SMCCC (QCOM_SCM_SMCINVOKE_*)  |
+   +-----------------------------+       +---------------------------------+
+
+References
+==========
+
+[1] https://docs.qualcomm.com/bundle/publicresource/topics/80-70015-11/qualcomm-trusted-execution-environment.html
+
+[2] http://infocenter.arm.com/help/topic/com.arm.doc.den0028a/index.html
+
+[3] drivers/firmware/qcom/qcom_scm.c
+
+[4] drivers/tee/qcomtee/qcomtee_msg.h
+
+[5] https://github.com/quic/quic-teec