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, 71 insertions, 0 deletions

diff --git a/Documentation/tee/ts-tee.rst b/Documentation/tee/ts-tee.rst
new file mode 100644
index 000000000..843e34422
--- /dev/null
+++ b/Documentation/tee/ts-tee.rst
@@ -0,0 +1,71 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+=================================
+TS-TEE (Trusted Services project)
+=================================
+
+This driver provides access to secure services implemented by Trusted Services.
+
+Trusted Services [1] is a TrustedFirmware.org project that provides a framework
+for developing and deploying device Root of Trust services in FF-A [2] S-EL0
+Secure Partitions. The project hosts the reference implementation of the Arm
+Platform Security Architecture [3] for Arm A-profile devices.
+
+The FF-A Secure Partitions (SP) are accessible through the FF-A driver [4] which
+provides the low level communication for this driver. On top of that the Trusted
+Services RPC protocol is used [5]. To use the driver from user space a reference
+implementation is provided at [6], which is part of the Trusted Services client
+library called libts [7].
+
+All Trusted Services (TS) SPs have the same FF-A UUID; it identifies the TS RPC
+protocol. A TS SP can host one or more services (e.g. PSA Crypto, PSA ITS, etc).
+A service is identified by its service UUID; the same type of service cannot be
+present twice in the same SP. During SP boot each service in the SP is assigned
+an "interface ID". This is just a short ID to simplify message addressing.
+
+The generic TEE design is to share memory at once with the Trusted OS, which can
+then be reused to communicate with multiple applications running on the Trusted
+OS. However, in case of FF-A, memory sharing works on an endpoint level, i.e.
+memory is shared with a specific SP. User space has to be able to separately
+share memory with each SP based on its endpoint ID; therefore a separate TEE
+device is registered for each discovered TS SP. Opening the SP corresponds to
+opening the TEE device and creating a TEE context. A TS SP hosts one or more
+services. Opening a service corresponds to opening a session in the given
+tee_context.
+
+Overview of a system with Trusted Services components::
+
+   User space                  Kernel space                   Secure world
+   ~~~~~~~~~~                  ~~~~~~~~~~~~                   ~~~~~~~~~~~~
+   +--------+                                               +-------------+
+   | Client |                                               | Trusted     |
+   +--------+                                               | Services SP |
+      /\                                                    +-------------+
+      ||                                                          /\
+      ||                                                          ||
+      ||                                                          ||
+      \/                                                          \/
+   +-------+                +----------+--------+           +-------------+
+   | libts |                |  TEE     | TS-TEE |           |  FF-A SPMC  |
+   |       |                |  subsys  | driver |           |   + SPMD    |
+   +-------+----------------+----+-----+--------+-----------+-------------+
+   |      Generic TEE API        |     |  FF-A  |     TS RPC protocol     |
+   |      IOCTL (TEE_IOC_*)      |     | driver |        over FF-A        |
+   +-----------------------------+     +--------+-------------------------+
+
+References
+==========
+
+[1] https://www.trustedfirmware.org/projects/trusted-services/
+
+[2] https://developer.arm.com/documentation/den0077/
+
+[3] https://www.arm.com/architecture/security-features/platform-security
+
+[4] drivers/firmware/arm_ffa/
+
+[5] https://trusted-services.readthedocs.io/en/v1.0.0/developer/service-access-protocols.html#abi
+
+[6] https://git.trustedfirmware.org/TS/trusted-services.git/tree/components/rpc/ts_rpc/caller/linux/ts_rpc_caller_linux.c?h=v1.0.0
+
+[7] https://git.trustedfirmware.org/TS/trusted-services.git/tree/deployments/libts/arm-linux/CMakeLists.txt?h=v1.0.0