Document x86_64-fortanix-unknown-sgx platform

Author: Jethro Beekman

src/doc/rustc/src/SUMMARY.md

@@ -32,6 +32,7 @@
     - [*-unknown-openbsd](platform-support/openbsd.md)
     - [\*-unknown-uefi](platform-support/unknown-uefi.md)
     - [wasm64-unknown-unknown](platform-support/wasm64-unknown-unknown.md)
+    - [x86_64-fortanix-unknown-sgx](platform-support/x86_64-fortanix-unknown-sgx.md)
     - [x86_64-unknown-none](platform-support/x86_64-unknown-none.md)
 - [Targets](targets/index.md)
     - [Built-in Targets](targets/built-in.md)

src/doc/rustc/src/platform-support.md

@@ -174,7 +174,7 @@ target | std | notes
 `wasm32-unknown-unknown` | ✓ | WebAssembly
 `wasm32-wasi` | ✓ | WebAssembly with WASI
 `x86_64-apple-ios` | ✓ | 64-bit x86 iOS
-`x86_64-fortanix-unknown-sgx` | ✓ | [Fortanix ABI] for 64-bit Intel SGX
+[`x86_64-fortanix-unknown-sgx`](platform-support/x86_64-fortanix-unknown-sgx.md) | ✓ | [Fortanix ABI] for 64-bit Intel SGX
 `x86_64-fuchsia` | ✓ | 64-bit Fuchsia
 `x86_64-linux-android` | ✓ | 64-bit x86 Android
 `x86_64-pc-solaris` | ✓ | 64-bit Solaris 10/11, illumos

src/doc/rustc/src/platform-support/x86_64-fortanix-unknown-sgx.md

@@ -0,0 +1,72 @@
+# `x86_64-fortanix-unknown-sgx`
+
+**Tier: 2**
+
+Secure enclaves using [Intel Software Guard Extensions
+(SGX)](https://www.intel.com/content/www/us/en/developer/tools/software-guard-extensions/overview.html)
+based on the ABI defined by Fortanix for the [Enclave Development Platform
+(EDP)](https://edp.fortanix.com/).
+
+## Target maintainers
+
+The [EDP team](mailto:[email protected]) at Fortanix.
+
+- Jethro Beekman [@jethrogb](https://github.com/jethrogb)
+- Raoul Strackx [@raoulstrackx](https://github.com/raoulstrackx)
+- Mohsen Zohrevandi [@mzohreva](https://github.com/mzohreva)
+
+## Requirements
+
+The target supports `std` with a default allocator. Only cross compilation is
+supported.
+
+Binaries support all CPUs that include Intel SGX. Only 64-bit mode is supported.
+
+Not all `std` features are supported, see [Using Rust's
+std](https://edp.fortanix.com/docs/concepts/rust-std/) for details.
+
+The `extern "C"` calling convention is the System V AMD64 ABI.
+
+The supported ABI is the
+[fortanix-sgx-abi](https://edp.fortanix.com/docs/api/fortanix_sgx_abi/index.html).
+
+The compiler output is ELF, but the native format for the platform is the SGX
+stream (SGXS) format. A converter like
+[ftxsgx-elf2sgxs](https://crates.io/crates/fortanix-sgx-tools) is needed.
+
+Programs in SGXS format adhering to the Fortanix SGX ABI can be run with any
+compatible runner, such as
+[ftxsgx-runner](https://crates.io/crates/fortanix-sgx-tools).
+
+See the [EDP installation
+guide](https://edp.fortanix.com/docs/installation/guide/) for recommendations
+on how to setup a development and runtime environment.
+
+## Building the target
+
+As a tier 2 target, the target is built by the Rust project.
+
+You can configure rustbuild like so:
+
+```toml
+[build]
+build-stage = 1
+target = ["x86_64-fortanix-unknown-sgx"]
+```
+
+## Building Rust programs
+
+Standard build flows using `cargo` or `rustc` should work.
+
+## Testing
+
+The Rust test suite as well as custom unit and integration tests will run on
+hardware that has Intel SGX enabled if a cargo runner is configured correctly,
+see the requirements section.
+
+## Cross-compilation toolchains and C code
+
+C code is not generally supported, as there is no libc. C code compiled for
+x86-64 in freestanding mode using the System V AMD64 ABI may work. The
+[rs-libc](https://crates.io/crates/rs-libc) crate contains a subset of libc
+that's known to work with this target.