building: add Rust SDK documentation

Add documentation for developing OP-TEE applications in Rust.

Signed-off-by: Yuan Zhuang <zhuangyuan04@baidu.com>
Signed-off-by: Rong Fan <fanrong03@baidu.com>
Acked-by: Etienne Carriere <etienne.carriere@linaro.org>
Reviewed-by: Joakim Bech <joakim.bech@linaro.org>

building/index.rst

@@ -23,3 +23,4 @@ You may also want to look at ":ref:`faq_try_optee`".
    toolchains
    trusted_applications
    efi_vars/stmm
+   optee_with_rust

building/optee_with_rust.rst

@@ -0,0 +1,99 @@
+.. _optee_with_rust:
+
+################ 
+OP-TEE with Rust
+################
+
+This document describes how to build OP-TEE client and trusted applications
+written in `Rust <https://www.rust-lang.org>`_ with `Teaclave TrustZone SDK
+<https://github.com/apache/incubator-teaclave-trustzone-sdk>`_.
+
+Clone OP-TEE repo 
+*****************
+
+Currently, Teaclave TrustZone SDK is compatible with QEMUv8 (aarch64).
+
+Before building examples written with Teaclave TrustZone SDK, you should 
+clone the OP-TEE repo first. For QEMUv8, run:
+
+.. code-block:: bash
+
+    $ mkdir YOUR_OPTEE_DIR && cd YOUR_OPTEE_DIR
+    $ repo init -u https://github.com/OP-TEE/manifest.git -m qemu_v8.xml 
+    $ repo sync
+
+The source code of Teaclave TrustZone SDK is located in 
+``YOUR_OPTEE_DIR/optee_rust/`` containing a set of examples written in Rust
+using the SDK.
+
+For more information about building OP-TEE using QEMUv8, see `run OP-TEE using
+QEMU
+<https://optee.readthedocs.io/en/latest/building/devices/qemu.html#qemu-v8>`_ .
+
+Compile Rust examples 
+*********************
+
+Rust example applications are located in ``optee_rust/examples/``. To build
+and install them with Buildroot, run:
+
+.. code-block:: bash
+
+    $ (cd build && make toolchains && make OPTEE_RUST_ENABLE=y CFG_TEE_RAM_VA_SIZE=0x00300000)
+
+Then start QEMUv8:
+
+.. code-block:: bash
+
+    $ (cd build && make run-only)
+
+.. hint::
+
+    Note that if you are under the environment without GUI, you can use
+    ``soc_term`` instead.
+
+    Access to normal world terminal:
+
+    .. code-block:: bash
+
+       $ ./build/soc_term.py 54320
+
+    Access to secure world terminal:
+
+    .. code-block:: bash
+
+       $ ./build/soc_term.py 54321
+
+    Run QEMU:
+
+    .. code-block:: bash
+
+       $ (cd build && make run-only)
+
+To differentiate from client applications generated by `optee_examples
+<https://optee.readthedocs.io/en/latest/building/gits/optee_examples/optee_examples.html#>`_
+, OP-TEE Rust examples are not prefixed with ``optee_example_`` but suffixed with
+``-rs``. More description about Rust examples can be found in `Overview of
+OP-TEE Rust Examples
+<https://teaclave.apache.org/trustzone-sdk-docs/overview-of-optee-rust-examples/>`_
+.
+
+During the build process, host applications are installed to ``/usr/bin/`` and
+TAs are installed to ``/lib/optee_armtz/``. After QEMU boots up, you can run
+host applications in normal world terminal. For example:
+
+.. code-block:: bash
+
+    $ hello_world-rs 
+    original value is 29 
+    inc value is 129 
+    dec value is 29
+    Success
+
+TA log will be printed correspondingly in the secure terminal.
+
+Development Documents
+*********************
+
+More information about developing OP-TEE applications in Rust can be found in
+`Teaclave TrustZone SDK Documentation
+<https://teaclave.apache.org/trustzone-sdk-docs/>`_.