add compilation support for first HelenOS targets

Author: mvolfik

compiler/rustc_target/src/spec/base/helenos.rs

@@ -0,0 +1,18 @@
+use crate::spec::{PanicStrategy, RelroLevel, TargetOptions};
+
+pub(crate) fn opts() -> TargetOptions {
+    TargetOptions {
+        os: "helenos".into(),
+
+        dynamic_linking: true,
+        // FIXME: this actually is supported by HelenOS, but then we run into issues
+        // with linking libstartfiles.a (parts of which obviously can't be at randomized
+        // positions). The crt_* flags also have some effect on this.
+        // position_independent_executables: true,
+
+        relro_level: RelroLevel::Full,
+        panic_strategy: PanicStrategy::Abort,
+
+        ..Default::default()
+    }
+}

compiler/rustc_target/src/spec/base/mod.rs

@@ -8,6 +8,7 @@ pub(crate) mod dragonfly;
 pub(crate) mod freebsd;
 pub(crate) mod fuchsia;
 pub(crate) mod haiku;
+pub(crate) mod helenos;
 pub(crate) mod hermit;
 pub(crate) mod hurd;
 pub(crate) mod hurd_gnu;

compiler/rustc_target/src/spec/mod.rs

@@ -1838,6 +1838,9 @@ supported_targets! {
     ("i686-unknown-haiku", i686_unknown_haiku),
     ("x86_64-unknown-haiku", x86_64_unknown_haiku),
 
+    ("i686-unknown-helenos", i686_unknown_helenos),
+    ("x86_64-unknown-helenos", x86_64_unknown_helenos),
+
     ("i686-unknown-hurd-gnu", i686_unknown_hurd_gnu),
     ("x86_64-unknown-hurd-gnu", x86_64_unknown_hurd_gnu),
 

compiler/rustc_target/src/spec/targets/i686_unknown_helenos.rs

@@ -0,0 +1,26 @@
+use crate::spec::{Cc, LinkerFlavor, Lld, StackProbeType, Target, base};
+
+pub(crate) fn target() -> Target {
+    let mut base = base::helenos::opts();
+    base.cpu = "pentium4".into();
+    base.max_atomic_width = Some(64);
+    base.stack_probes = StackProbeType::Inline;
+    base.linker = Some("i686-helenos-gcc".into());
+    base.add_pre_link_args(LinkerFlavor::Gnu(Cc::Yes, Lld::No), &["-m32"]);
+
+    Target {
+        llvm_target: "i686-unknown-helenos".into(),
+        metadata: crate::spec::TargetMetadata {
+            description: Some("IA-32 (i686) HelenOS".into()),
+            tier: Some(3),
+            host_tools: Some(false),
+            std: None,
+        },
+        pointer_width: 32,
+        data_layout: "e-m:e-p:32:32-p270:32:32-p271:32:32-p272:64:64-\
+            i128:128-f64:32:64-f80:32-n8:16:32-S128"
+            .into(),
+        arch: "x86".into(),
+        options: base,
+    }
+}

compiler/rustc_target/src/spec/targets/x86_64_unknown_helenos.rs

@@ -0,0 +1,26 @@
+use crate::spec::{Cc, LinkerFlavor, Lld, StackProbeType, Target, base};
+
+pub(crate) fn target() -> Target {
+    let mut base = base::helenos::opts();
+    base.cpu = "x86-64".into();
+    base.plt_by_default = false;
+    base.max_atomic_width = Some(64);
+    base.stack_probes = StackProbeType::Inline;
+    base.linker = Some("amd64-helenos-gcc".into());
+    base.add_pre_link_args(LinkerFlavor::Gnu(Cc::Yes, Lld::No), &["-m64"]);
+
+    Target {
+        llvm_target: "x86_64-unknown-helenos".into(),
+        metadata: crate::spec::TargetMetadata {
+            description: Some("64-bit HelenOS".into()),
+            tier: Some(3),
+            host_tools: Some(false),
+            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,
+    }
+}

src/bootstrap/src/core/sanity.rs

@@ -33,6 +33,8 @@ pub struct Finder {
 //
 // Targets can be removed from this list once they are present in the stage0 compiler (usually by updating the beta compiler of the bootstrap).
 const STAGE0_MISSING_TARGETS: &[&str] = &[
+    "i686-unknown-helenos",
+    "x86_64-unknown-helenos",
     // just a dummy comment so the list doesn't get onelined
     "x86_64-lynx-lynxos178",
 ];

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

@@ -313,6 +313,7 @@ target | std | host | notes
 [`i686-apple-darwin`](platform-support/apple-darwin.md) | ✓ | ✓ | 32-bit macOS (10.12+, Sierra+, Penryn) [^x86_32-floats-return-ABI]
 [`i686-pc-nto-qnx700`](platform-support/nto-qnx.md) | * |  | 32-bit x86 QNX Neutrino 7.0 RTOS (Pentium 4) [^x86_32-floats-return-ABI]
 `i686-unknown-haiku` | ✓ | ✓ | 32-bit Haiku (Pentium 4) [^x86_32-floats-return-ABI]
+[`i686-unknown-helenos`](platform-support/helenos.md) | ? |  | HelenOS IA-32
 [`i686-unknown-hurd-gnu`](platform-support/hurd.md) | ✓ | ✓ | 32-bit GNU/Hurd (Pentium 4) [^x86_32-floats-return-ABI]
 [`i686-unknown-netbsd`](platform-support/netbsd.md) | ✓ | ✓ | NetBSD/i386 (Pentium 4) [^x86_32-floats-return-ABI]
 [`i686-unknown-openbsd`](platform-support/openbsd.md) | ✓ | ✓ | 32-bit OpenBSD (Pentium 4) [^x86_32-floats-return-ABI]
@@ -416,6 +417,7 @@ target | std | host | notes
 `x86_64-unknown-dragonfly` | ✓ | ✓ | 64-bit DragonFlyBSD
 `x86_64-unknown-haiku` | ✓ | ✓ | 64-bit Haiku
 [`x86_64-unknown-hermit`](platform-support/hermit.md) | ✓ |  | x86_64 Hermit
+[`x86_64-unknown-helenos`](platform-support/helenos.md) | ? |  | x86_64 (amd64) HelenOS
 [`x86_64-unknown-hurd-gnu`](platform-support/hurd.md) | ✓ | ✓ | 64-bit GNU/Hurd
 `x86_64-unknown-l4re-uclibc` | ? |  |
 [`x86_64-unknown-linux-none`](platform-support/x86_64-unknown-linux-none.md) | * |  | 64-bit Linux with no libc

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

@@ -0,0 +1,52 @@
+# `*-unknown-helenos`
+
+**Tier: 3**
+
+Targets for [HelenOS](https://www.helenos.org).
+These targets allow compiling user-space applications, that you can then copy into your HelenOS ISO image to run them.
+
+Target triplets available so far:
+
+- `x86_64-unknown-helenos`
+- `i686-unknown-helenos`
+
+## Target maintainers
+
+- Matěj Volf ([@mvolfik](https://github.com/mvolfik))
+
+## Requirements
+
+These targets only support cross-compilation. The targets will[^1] support libstd, although support of some platform features (filesystem, networking) may be limited.
+
+You need to have a local clone of the HelenOS repository and the HelenOS toolchain set up, no HelenOS-Rust development artifacts are available.
+
+[^1]: The support is not yet available, because it needs to be done in a separate PR, because compiler support needs to be merged first to allow creating libc bindings
+
+## Building
+
+### HelenOS toolchain setup
+
+For compilation of standard library, you need to build the HelenOS toolchain (because Rust needs to use `*-helenos-gcc` as linker) and shared libraries. See [this HelenOS wiki page](https://www.helenos.org/wiki/UsersGuide/CompilingFromSource#a2.Buildasupportedcross-compiler) for instruction on setting up the build. At the end of step 4 (_Configure and build_), invoke `ninja export-dev` to build the shared libraries.
+
+Then copy these shared libraries from `export-dev/lib` to the path where the compiler automatically searches for them. This will be the directory where you installed the toolchain (for example `~/.local/share/HelenOS/cross/i686-helenos/lib`). You can see this path with this command:
+
+```sh
+touch /tmp/test.c
+i686-helenos-gcc -v -c /tmp/test.c 2>&1 | grep LIBRARY_PATH
+```
+
+## Building the target
+
+When you have the HelenOS toolchain set up and installed in your path, you can build the Rust toolchain using the standard procedure. See [rustc dev guide](https://rustc-dev-guide.rust-lang.org/building/how-to-build-and-run.html).
+
+## Building Rust programs
+
+No special setup is needed. Simply use the toolchain you built above and run `cargo build --target <arch>-unknown-helenos`.
+
+## Testing
+
+Running the Rust test suite has not been attempted yet.
+
+## Cross-compilation toolchains and C code
+
+You should be able to cross-compile and link any needed C code using `<arch>-helenos-gcc` that you built above. However, note that clang support is highly lacking. Therefore, to run tools such as `bindgen`, you will need to provide flag `-nostdinc` and manually specify the include paths to HelenOS headers, which you will find in the `export-dev` + in the cross-compilation toolchain (e.g. `~/.local/share/HelenOS/cross/lib/gcc/i686-helenos/14.2.0/include`).