Doc: add tutorial about how to use optee-utee-build

1. add document "Writing Rust TAs using optee-utee-build"
2. suggest developers using optee-utee-build in
   "Migrating to new building env"

docs/README.md

@@ -8,3 +8,4 @@ permalink: /trustzone-sdk-docs
 * [Debugging OP-TEE TA](debugging-optee-ta.md)
 * [Expanding TA Secure Memory on QEMUv8](expanding-ta-secure-memory-on-qemuv8.md)
 * [Building Rust CA as Android ELF](building-rust-ca-as-android-elf.md)
+* [Writing Rust TAs using optee-utee-build](writing-rust-tas-using-optee-utee-build.md)

docs/migrating-to-new-building-env.md

@@ -2,6 +2,8 @@
 permalink: /trustzone-sdk-docs/migrating-to-new-building-env.md
 ---
 
+> After optee-utee-build release, this doc is keeping for developers who intend to know the detail of building process, we suggest use optee-utee-build for building instead.
+
 ## Migration Guide: Moving from `master` to `main` Branch (Post-Oct 2024)
 
 Since the `main` branch (after October 2024) introduces breaking changes 

docs/writing-rust-tas-using-optee-utee-build.md

@@ -0,0 +1,182 @@
+---
+permalink: /trustzone-sdk-docs/writing-rust-tas-using-optee-utee-build.md
+---
+
+Currently we provide a `optee-utee-build` crate to simplify the compilcated building process of TA, and we recommend everyone use it in future developement.
+
+# Minimal Example
+Assuming currently we are developing a `hello_world` TA, and we want to build it with `optee-utee-build` crate, we can do it by following steps.
+
+Firstly, we should add `optee-utee-build` in `build-dependencies`:
+```shell
+cargo add --build optee-utee-build
+```
+
+Secondly, we set a `ta_config` and call `optee-utee-build::build` with it in build.rs:
+```rust
+use proto;
+use optee_utee_build::{TAConfig, Error, RustEdition};
+
+fn main() -> Result<(), Error> {
+    let ta_config = TAConfig::new_standard_with_cargo_env(proto::UUID)?;
+    optee_utee_build::build(RustEdition::Before2024, ta_config)
+}
+```
+It will generate a `user_ta_header.rs` file and setup all the required configurations of the linker of rustc.
+
+Finally, we include the generated `user_ta_header.rs` in the source codes, normally we put it in `src/main.rs`
+```rust
+// src/main.rs
+include!(concat!(env!("OUT_DIR"), "/user_ta_header.rs"));
+```
+After that, everything finished, we can start building the TA now.
+
+For full codes, you can check the [`hello_world-rs example`](https://github.com/apache/incubator-teaclave-trustzone-sdk/tree/main/examples/hello_world-rs/ta)
+
+# Explaination of Minimal Example
+
+### 1. The TAConfig
+
+This is a struct that use for the configuration of the TA we are developing, it has some public fields:
+
+|Field Name|Description|
+|----|----|
+|uuid|the identifier of current TA|
+|ta_flags|combination of some bitflags, check [this](https://github.com/OP-TEE/optee_os/blob/c2e42a8f03a5bb6b894ef85ae409f54760c1f50e/lib/libutee/include/user_ta_header.h#L13-L53) for available values|
+|ta_data_size|defines the size in bytes of the TA allocation pool|
+|ta_stack_size|defines the size in bytes of the stack used for TA execution|
+|ta_version|a version string of current TA, must be in semver format|
+|ta_description|the desciption of current TA|
+|trace_level|the default trace level of current TA, check [this](https://github.com/OP-TEE/optee_os/blob/c2e42a8f03a5bb6b894ef85ae409f54760c1f50e/lib/libutils/ext/include/trace_levels.h#L26-L31) for available values|
+|trace_ext|an extra prefix string when output trace log|
+|ta_framework_stack_size|defines the size in bytes of the stack used for Trusted Core Framework, currently used for trace framework and invoke command, should not be less than 2048|
+|ext_properties|the extra custom properties that will be added|
+
+We can construct the `TAConfig` by providing all of the public fields manually, or use our standard constructor.
+|Constructor|Description|
+|----|----|
+|new_standard|construct a standard TAConfig by providing uuid, ta_version and ta_description, with other configurations set to suggested values, you can update those configurations later|
+|new_standard_with_cargo_env|it's a constructor wrapped with new_standard, but take `version` and `description` from cargo.toml so simply providing a uuid as parameter is enough|
+### 2. The RustEdition
+
+The generated `user_ta_header.rs` must be different between `edition of 2024` and `edition before 2024`, and currently there is no official stable way to know what edition we are compiling with, so we provide a argument to set with.
+
+> #### What’s the difference?
+> the generated `user_ta_header.rs` file include some const variables and methods tagged with `no_mangle` and `link_section`, start from rust edition of 2024, they must be wrapped with unsafe, or rustc will output a compilation error(while before edition of 2024 it must not, or rustc will output a syntax error)
+
+# Customization
+
+`optee-utee-build` provide some struct for flexible use.
+
+### 1. Builder
+Expect calling `build` function directly, you can also use Builder for customization.
+
+Usage:
+```Rust
+use proto;
+use optee_utee_build::{TAConfig, Builder, Error, RustEdition, LinkType};
+
+fn main() -> Result<(), Error> {
+    let ta_config = TAConfig::new_standard_with_cargo_env(proto::UUID)?;
+    Builder::new(RustEdition::Before2024, ta_config)
+      .out_dir("/tmp")
+      .header_file_name("my_generated_user_ta_header.rs")
+      .link_type(LinkType::CC)
+      .build()
+}
+```
+As you can see from the codes, there are some customizations of the builder:
+|Configuration|Description|
+|----|----|
+|out_dir|change directory of output files, default to OUT_DIR by cargo|
+|header_file_name|change name of output header file. default to `user_ta_header.rs`|
+|link_type|set link_type manually. <br/>there are some difference in parameters in linkers between `CC` and `LD` types, for example, `--sort-section` in `CC` types of linkers changes to `-Wl,--sort-section`, we will try to detect current linker that cargo using, you can use this function to set it manually if you think our detection mismatch.|
+
+### 2. Linker
+For some developers who want to use a hand-written `user_ta_header.rs` and just want `optee-utee-build` to handle the building stuff only, they can use the `Linker`, otherwise, try `Builder` instead.
+
+Usage:
+``` rust
+use optee_utee_build::{Linker, Error};
+use std::env;
+
+fn main() -> Result<(), Error> {
+  let out_dir = env::var("OUT_DIR")?;
+  Linker::auto().link_all(out_dir)?;
+  Ok(())
+}
+```
+When linking manually, developers construct a `Linker` and calling the `link_all` method by providing the out_dir, and linker will generate some required files (link script, etc) and handle all the linking stuff.
+
+In above codes, we use `auto` to construct the linker, it will detect current linker that cargo using automatically, you can use `new` function to construct the linker manually if you think our detection mismatch.
+```rust
+use optee_utee_build::{Linker, Error, LinkType};
+use std::env;
+
+fn main() -> Result<(), Error> {
+  let out_dir = env::var("OUT_DIR")?;
+  Linker::new(LinkerType::CC).link_all(out_dir)?;
+  Ok(())
+}
+```
+
+### 3. HeaderFileGenerator
+For some developers who want to do the linking themselves and just want `optee-utee-build` to generate a header file only, they can use the `HeaderFileGenerator`, otherwise, try `Builder` instead.
+
+Usage:
+```rust
+use optee_utee_build::{HeaderFileGenerator, TAConfig, RustEdition, Error};
+
+fn main() -> Result<(), Error> {
+  const UUID: &str = "26509cec-4a2b-4935-87ab-762d89fbf0b0";
+  let ta_config = TAConfig::new_standard(UUID, "0.1.0", "example")?;
+  let codes = HeaderFileGenerator::new(RustEdition::Before2024).generate(&ta_config)?;
+  Ok(std::io::Write("/tmp/user_ta_header.rs", codes.as_bytes())?)
+}
+
+```
+
+# Migration Guide
+For developers still using `const configuration values` in `src/main.rs` and `custom build scripts` in `build.rs` (described in [\[migrating-to-new-building-env\]](https://github.com/apache/incubator-teaclave-trustzone-sdk/blob/main/docs/migrating-to-new-building-env.md)), they can upgrade to `optee-utee-build` by following step:
+
+Firstly, add `optee-utee-build` as `build-dependencies`:
+```shell
+cargo add --build optee-utee-build
+```
+
+Secondly, in `build.rs`, remove codes of `custom build scripts`, and use `optee_utee_build::build` instead:
+```rust
+// ... other imports
+use optee_utee_build::{TAConfig, Error}
+
+fn main() -> Result<(), Error> {
+  let ta_config = TAConfig::new_standard_with_cargo_env(proto::UUID)?
+    .ta_stack_size(10 * 1024); // should customize it with the const configuration values in your src/main.rs
+  optee_utee_build::build(RustEdition::Before2024, ta_config)?;
+
+  // ... other build scripts
+}
+```
+
+Thirdly, remove `const configuration values` in `src/main.rs`, keep the line of `include user_ta_header.rs`
+```rust
+/// ... other codes in src/main.rs
+
+/* remove const configuration values, move them to TAConfig in src/main.rs
+// TA configurations
+const TA_FLAGS: u32 = 0;
+const TA_DATA_SIZE: u32 = 32 * 1024;
+const TA_STACK_SIZE: u32 = 2 * 1024;
+const TA_VERSION: &[u8] = b"0.1\0";
+const TA_DESCRIPTION: &[u8] = b"This is a hello world example.\0";
+const EXT_PROP_VALUE_1: &[u8] = b"Hello World TA\0";
+const EXT_PROP_VALUE_2: u32 = 0x0010;
+const TRACE_LEVEL: i32 = 4;
+const TRACE_EXT_PREFIX: &[u8] = b"TA\0";
+const TA_FRAMEWORK_STACK_SIZE: u32 = 2048;
+*/
+
+include!(concat!(env!("OUT_DIR"), "/user_ta_header.rs"));  // keep this line
+```
+Finally, delete the useless `ta_static.rs` and can start building now.
+