Add dedicated platform support page for Redox OS

src/doc/rustc/src/SUMMARY.md

@@ -71,6 +71,7 @@
     - [*-unknown-hermit](platform-support/hermit.md)
     - [\*-unknown-netbsd\*](platform-support/netbsd.md)
     - [*-unknown-openbsd](platform-support/openbsd.md)
+    - [*-unknown-redox](platform-support/redox.md)
     - [\*-unknown-uefi](platform-support/unknown-uefi.md)
     - [wasm32-wasip1](platform-support/wasm32-wasip1.md)
     - [wasm32-wasip1-threads](platform-support/wasm32-wasip1-threads.md)

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

@@ -203,7 +203,7 @@ target | std | notes
 `x86_64-unknown-linux-gnux32` | ✓ | 64-bit Linux (x32 ABI) (kernel 4.15, glibc 2.27)
 [`x86_64-unknown-linux-ohos`](platform-support/openharmony.md) | ✓ | x86_64 OpenHarmony
 [`x86_64-unknown-none`](platform-support/x86_64-unknown-none.md) | * | Freestanding/bare-metal x86_64, softfloat
-`x86_64-unknown-redox` | ✓ | Redox OS
+[`x86_64-unknown-redox`](platform-support/redox.md) | ✓ | Redox OS
 [`x86_64-unknown-uefi`](platform-support/unknown-uefi.md) | ? | 64-bit UEFI
 
 [^x86_32-floats-x87]: Floating-point support on `i586` targets is non-compliant: the `x87` registers and instructions used for these targets do not provide IEEE-754-compliant behavior, in particular when it comes to rounding and NaN payload bits. See [issue #114479][x86-32-float-issue].
@@ -258,7 +258,7 @@ target | std | host | notes
 `aarch64-unknown-linux-gnu_ilp32` | ✓ | ✓ | ARM64 Linux (ILP32 ABI)
 [`aarch64-unknown-netbsd`](platform-support/netbsd.md) | ✓ | ✓ | ARM64 NetBSD
 [`aarch64-unknown-openbsd`](platform-support/openbsd.md) | ✓ | ✓ | ARM64 OpenBSD
-`aarch64-unknown-redox` | ? |  | ARM64 Redox OS
+[`aarch64-unknown-redox`](platform-support/redox.md) | ✓ |  | ARM64 Redox OS
 `aarch64-uwp-windows-msvc` | ✓ |  |
 `aarch64-wrs-vxworks` | ? |  |
 `aarch64_be-unknown-linux-gnu_ilp32` | ✓ | ✓ | ARM64 Linux (big-endian, ILP32 ABI)
@@ -300,7 +300,7 @@ target | std | host | notes
 [`i686-unknown-hurd-gnu`](platform-support/hurd.md) | ✓ | ✓ | 32-bit GNU/Hurd [^x86_32-floats-return-ABI]
 [`i686-unknown-netbsd`](platform-support/netbsd.md) | ✓ | ✓ | NetBSD/i386 with SSE2 [^x86_32-floats-return-ABI]
 [`i686-unknown-openbsd`](platform-support/openbsd.md) | ✓ | ✓ | 32-bit OpenBSD [^x86_32-floats-return-ABI]
-`i686-unknown-redox` | ? |  | i686 Redox OS
+[`i686-unknown-redox`](platform-support/redox.md) | ✓ |  | i686 Redox OS
 `i686-uwp-windows-gnu` | ✓ |  | [^x86_32-floats-return-ABI]
 `i686-uwp-windows-msvc` | ✓ |  | [^x86_32-floats-return-ABI]
 [`i686-win7-windows-msvc`](platform-support/win7-windows-msvc.md) | ✓ |   | 32-bit Windows 7 support [^x86_32-floats-return-ABI]

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

@@ -0,0 +1,53 @@
+# `*-unknown-redox`
+
+**Tier: 2/3**
+
+Targets for the [Redox OS](https://redox-os.org/) operating
+system.
+
+Target triplets available so far:
+
+- `x86_64-unknown-redox` (tier 2)
+- `aarch64-unknown-redox` (tier 3)
+- `i686-unknown-redox` (tier 3)
+
+## Target maintainers
+
+- Jeremy Soller ([@jackpot51](https://github.com/jackpot51))
+
+## Requirements
+
+These targets are natively compiled and can be cross-compiled. Std is fully supported.
+
+The targets are only expected to work with the latest version of Redox OS as the ABI is not yet stable.
+
+`extern "C"` uses the official calling convention of the respective architectures.
+
+Redox OS binaries use ELF as file format.
+
+## Building the target
+
+You can build Rust with support for the targets by adding it to the `target` list in `config.toml`. In addition a copy of [relibc] needs to be present in the linker search path.
+
+```toml
+[build]
+build-stage = 1
+target = [
+    "<HOST_TARGET>",
+    "x86_64-unknown-redox",
+    "aarch64-unknown-redox",
+    "i686-unknown-redox",
+]
+```
+
+[relibc]: https://gitlab.redox-os.org/redox-os/relibc
+
+## Building Rust programs and testing
+
+Rust does not yet ship pre-compiled artifacts for Redox OS except for x86_64-unknown-redox.
+
+The easiest way to build and test programs for Redox OS is using [redoxer](https://gitlab.redox-os.org/redox-os/redoxer) which sets up the required compiler toolchain for building as well as runs programs inside a Redox OS VM using QEMU.
+
+## Cross-compilation toolchains and C code
+
+The target supports C code. Pre-compiled C toolchains can be found at <https://static.redox-os.org/toolchain/>.