Add x86_64-unknown-motor (Motor OS) tier 3 target

Add the initial no-std Motor OS compiler target.

Motor OS has been developed for several years in the open:
https://github.com/moturus/motor-os.

It has a more or less full implementation of Rust std library,
as well as tokio/mio ports.

Build instructions can be found here:
https://github.com/moturus/motor-os/blob/main/docs/build.md.

Signed-off-by: U. Lasiotus <lasiotus@motor-os.org>

3 files changed, 51 insertions, 0 deletions

diff --git a/src/bootstrap/src/core/sanity.rs b/src/bootstrap/src/core/sanity.rs
index 68202500d97..91d80c96e42 100644
--- a/src/bootstrap/src/core/sanity.rs
+++ b/src/bootstrap/src/core/sanity.rs
@@ -38,6 +38,7 @@ const STAGE0_MISSING_TARGETS: &[&str] = &[
     // just a dummy comment so the list doesn't get onelined
     "aarch64_be-unknown-hermit",
     "aarch64_be-unknown-none-softfloat",
+    "x86_64-unknown-motor",
 ];
 
 /// Minimum version threshold for libstdc++ required when using prebuilt LLVM
@@ -239,6 +240,10 @@ than building it.
             continue;
         }
 
+        if target.contains("motor") {
+            continue;
+        }
+
         // skip check for cross-targets
         if skip_target_sanity && target != &build.host_target {
             continue;
diff --git a/src/doc/rustc/src/platform-support.md b/src/doc/rustc/src/platform-support.md
index e5e46f72637..99c8e365f5c 100644
--- a/src/doc/rustc/src/platform-support.md
+++ b/src/doc/rustc/src/platform-support.md
@@ -431,6 +431,7 @@ target | std | host | notes
 `x86_64-unknown-l4re-uclibc` | ? |  |
 [`x86_64-unknown-linux-none`](platform-support/x86_64-unknown-linux-none.md) | * |  | 64-bit Linux with no libc
 [`x86_64-unknown-managarm-mlibc`](platform-support/managarm.md) | ? |   | x86_64 Managarm
+[`x86_64-unknown-motor`[(platform-support/motor.md) | ? |  | x86_64 Motor OS
 [`x86_64-unknown-openbsd`](platform-support/openbsd.md) | ✓ | ✓ | 64-bit OpenBSD
 [`x86_64-unknown-trusty`](platform-support/trusty.md) | ✓ |  |
 `x86_64-uwp-windows-gnu` | ✓ |  |
diff --git a/src/doc/rustc/src/platform-support/motor.md b/src/doc/rustc/src/platform-support/motor.md
new file mode 100644
index 00000000000..e7aa7b23f3a
--- /dev/null
+++ b/src/doc/rustc/src/platform-support/motor.md
@@ -0,0 +1,45 @@
+# `x86_64-unknown-motor`
+
+**Tier: 3**
+
+[Motor OS](https://github.com/moturus/motor-os) is a new operating system
+for virtualized environments.
+
+## Target maintainers
+
+[@lasiotus](https://github.com/lasiotus)
+
+## Requirements
+
+This target is cross-compiled. There are no special requirements for the host.
+
+Motor OS uses the ELF file format.
+
+## Building the target
+
+The target can be built by enabling it for a `rustc` build, for example:
+
+```toml
+[build]
+build-stage = 2
+target = ["x86_64-unknown-motor"]
+```
+
+## Building Rust programs
+
+Rust standard library is fully supported/implemented, but is not yet part of
+the official Rust repo, so an out-of-tree building process should be
+followed, as described in the
+[build doc](https://github.com/moturus/motor-os/blob/main/docs/build.md).
+
+## Testing
+
+Cross-compiled Rust binaries and test artifacts can be executed in Motor OS VMs,
+as described in e.g.
+[Hello Motor OS](https://github.com/moturus/motor-os/blob/main/docs/recipes/hello-motor-os.md)
+example.
+
+## Cross-compilation toolchains and C code
+
+C code can be compiled as part of Rust cargo projects. However, there is
+no libc support.