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>

4 files changed, 74 insertions, 0 deletions

diff --git a/compiler/rustc_target/src/spec/base/mod.rs b/compiler/rustc_target/src/spec/base/mod.rs
index be15da7329d..6ab8597a4ec 100644
--- a/compiler/rustc_target/src/spec/base/mod.rs
+++ b/compiler/rustc_target/src/spec/base/mod.rs
@@ -21,6 +21,7 @@ pub(crate) mod linux_uclibc;
 pub(crate) mod linux_wasm;
 pub(crate) mod lynxos178;
 pub(crate) mod managarm_mlibc;
+pub(crate) mod motor;
 pub(crate) mod msvc;
 pub(crate) mod netbsd;
 pub(crate) mod nto_qnx;
diff --git a/compiler/rustc_target/src/spec/base/motor.rs b/compiler/rustc_target/src/spec/base/motor.rs
new file mode 100644
index 00000000000..18485b2cef2
--- /dev/null
+++ b/compiler/rustc_target/src/spec/base/motor.rs
@@ -0,0 +1,34 @@
+use crate::spec::{
+    Cc, FramePointer, LinkerFlavor, Lld, PanicStrategy, StackProbeType, TargetOptions,
+};
+
+pub(crate) fn opts() -> TargetOptions {
+    let pre_link_args = TargetOptions::link_args(
+        LinkerFlavor::Gnu(Cc::No, Lld::No),
+        &[
+            "-e",
+            "motor_start",
+            "--no-undefined",
+            "--error-unresolved-symbols",
+            "--no-undefined-version",
+            "-u",
+            "__rust_abort",
+        ],
+    );
+    TargetOptions {
+        os: "motor".into(),
+        executables: true,
+        // TLS is false below because if true, the compiler assumes
+        // we handle TLS at the ELF loading level, which we don't.
+        // We use "OS level" TLS (see thread/local.rs in stdlib).
+        has_thread_local: false,
+        frame_pointer: FramePointer::NonLeaf,
+        linker_flavor: LinkerFlavor::Gnu(Cc::No, Lld::No),
+        main_needs_argc_argv: true,
+        panic_strategy: PanicStrategy::Abort,
+        pre_link_args,
+        stack_probes: StackProbeType::Inline,
+        supports_stack_protector: true,
+        ..Default::default()
+    }
+}
diff --git a/compiler/rustc_target/src/spec/mod.rs b/compiler/rustc_target/src/spec/mod.rs
index f705af52bd8..c40358af593 100644
--- a/compiler/rustc_target/src/spec/mod.rs
+++ b/compiler/rustc_target/src/spec/mod.rs
@@ -1642,6 +1642,7 @@ supported_targets! {
     ("aarch64-unknown-hermit", aarch64_unknown_hermit),
     ("riscv64gc-unknown-hermit", riscv64gc_unknown_hermit),
     ("x86_64-unknown-hermit", x86_64_unknown_hermit),
+    ("x86_64-unknown-motor", x86_64_unknown_motor),
 
     ("x86_64-unikraft-linux-musl", x86_64_unikraft_linux_musl),
 
diff --git a/compiler/rustc_target/src/spec/targets/x86_64_unknown_motor.rs b/compiler/rustc_target/src/spec/targets/x86_64_unknown_motor.rs
new file mode 100644
index 00000000000..0fd43357a76
--- /dev/null
+++ b/compiler/rustc_target/src/spec/targets/x86_64_unknown_motor.rs
@@ -0,0 +1,38 @@
+use crate::spec::{
+    CodeModel, LinkSelfContainedDefault, LldFlavor, RelocModel, RelroLevel, Target, base,
+};
+
+pub(crate) fn target() -> Target {
+    let mut base = base::motor::opts();
+    base.cpu = "x86-64".into();
+    base.max_atomic_width = Some(64);
+    base.code_model = Some(CodeModel::Small);
+
+    // We want fully static relocatable binaries. It was surprisingly
+    // difficult to make it happen reliably, especially various
+    // linker-related options below. Mostly trial and error.
+    base.position_independent_executables = true;
+    base.relro_level = RelroLevel::Full;
+    base.static_position_independent_executables = true;
+    base.relocation_model = RelocModel::Pic;
+    base.lld_flavor_json = LldFlavor::Ld;
+    base.link_self_contained = LinkSelfContainedDefault::True;
+    base.dynamic_linking = false;
+    base.crt_static_default = true;
+    base.crt_static_respected = true;
+
+    Target {
+        llvm_target: "x86_64-unknown-none-elf".into(),
+        metadata: crate::spec::TargetMetadata {
+            description: Some("Motor OS".into()),
+            tier: Some(3),
+            host_tools: None,
+            std: None,
+        },
+        pointer_width: 64,
+        data_layout:
+            "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128".into(),
+        arch: "x86_64".into(),
+        options: base,
+    }
+}