redesign of the interface to the unikernel HermitCore

- the old interface between HermitCore and the Rust Standard Library
  based on a small C library (newlib)
- remove this interface and call directly the unikernel
- remove the dependency to the HermitCore linker
- use rust-lld as linker

src/bootstrap/lib.rs

@@ -160,7 +160,7 @@ mod job {
     }
 }
 
-#[cfg(any(target_os = "haiku", not(any(unix, windows))))]
+#[cfg(any(target_os = "haiku", target_os = "hermit", not(any(unix, windows))))]
 mod job {
     pub unsafe fn setup(_build: &mut crate::Build) {
     }

src/libpanic_abort/lib.rs

@@ -54,7 +54,8 @@ pub unsafe extern fn __rust_start_panic(_payload: usize) -> u32 {
         core::intrinsics::abort();
     }
 
-    #[cfg(all(target_vendor="fortanix", target_env="sgx"))]
+    #[cfg(any(target_os = "hermit",
+              all(target_vendor="fortanix", target_env="sgx")))]
     unsafe fn abort() -> ! {
         // call std::sys::abort_internal
         extern "C" { pub fn __rust_abort() -> !; }

src/libpanic_unwind/hermit.rs

@@ -0,0 +1,21 @@
+//! Unwinding for *hermit* target.
+//!
+//! Right now we don't support this, so this is just stubs.
+
+use alloc::boxed::Box;
+use core::ptr;
+use core::any::Any;
+
+pub fn payload() -> *mut u8 {
+    ptr::null_mut()
+}
+
+pub unsafe fn cleanup(_ptr: *mut u8) -> Box<dyn Any + Send> {
+    extern "C" { pub fn __rust_abort() -> !; }
+    __rust_abort();
+}
+
+pub unsafe fn panic(_data: Box<dyn Any + Send>) -> u32 {
+    extern "C" { pub fn __rust_abort() -> !; }
+    __rust_abort();
+}

src/libpanic_unwind/lib.rs

@@ -43,6 +43,9 @@ cfg_if::cfg_if! {
     } else if #[cfg(target_arch = "wasm32")] {
         #[path = "dummy.rs"]
         mod imp;
+    } else if #[cfg(target_os = "hermit")] {
+        #[path = "hermit.rs"]
+        mod imp;
     } else if #[cfg(all(target_env = "msvc", target_arch = "aarch64"))] {
         #[path = "dummy.rs"]
         mod imp;

src/librustc_target/spec/hermit_base.rs

@@ -1,26 +1,26 @@
-use crate::spec::{LinkArgs, LinkerFlavor, PanicStrategy, TargetOptions};
+use crate::spec::{LldFlavor, LinkArgs, LinkerFlavor, PanicStrategy, TargetOptions};
 use std::default::Default;
 
 pub fn opts() -> TargetOptions {
-    let mut args = LinkArgs::new();
-    args.insert(LinkerFlavor::Gcc, vec![
-        "-Wl,-Bstatic".to_string(),
-        "-Wl,--no-dynamic-linker".to_string(),
-        "-Wl,--gc-sections".to_string(),
-        "-Wl,--as-needed".to_string(),
+    let mut pre_link_args = LinkArgs::new();
+    pre_link_args.insert(LinkerFlavor::Lld(LldFlavor::Ld), vec![
+        "--build-id".to_string(),
+        "--hash-style=gnu".to_string(),
+        "--Bstatic".to_string(),
     ]);
 
     TargetOptions {
+        linker: Some("rust-lld".to_owned()),
         executables: true,
         has_elf_tls: true,
         linker_is_gnu: true,
-        no_default_libraries: false,
+        pre_link_args,
+        no_default_libraries: true,
         panic_strategy: PanicStrategy::Abort,
-        position_independent_executables: false,
-        pre_link_args: args,
+        position_independent_executables: true,
         relocation_model: "static".to_string(),
-        target_family: Some("unix".to_string()),
-        tls_model: "local-exec".to_string(),
+        target_family: None,
+        tls_model: "initial-exec".to_string(),
         .. Default::default()
     }
 }

src/librustc_target/spec/x86_64_unknown_hermit.rs

@@ -1,11 +1,11 @@
-use crate::spec::{LinkerFlavor, Target, TargetResult};
+use crate::spec::{LldFlavor, LinkerFlavor, Target, TargetResult};
 
 pub fn target() -> TargetResult {
     let mut base = super::hermit_base::opts();
     base.cpu = "x86-64".to_string();
-    base.pre_link_args.get_mut(&LinkerFlavor::Gcc).unwrap().push("-m64".to_string());
-    base.linker = Some("x86_64-hermit-gcc".to_string());
     base.max_atomic_width = Some(64);
+    base.features = "+rdrnd,+rdseed".to_string();
+    base.stack_probes = true;
 
     Ok(Target {
         llvm_target: "x86_64-unknown-hermit".to_string(),
@@ -17,7 +17,7 @@ pub fn target() -> TargetResult {
         target_os: "hermit".to_string(),
         target_env: String::new(),
         target_vendor: "unknown".to_string(),
-        linker_flavor: LinkerFlavor::Gcc,
+        linker_flavor: LinkerFlavor::Lld(LldFlavor::Ld),
         options: base,
     })
 }

src/librustdoc/clean/cfg.rs

@@ -346,6 +346,7 @@ impl<'a> fmt::Display for Html<'a> {
                         "freebsd" => "FreeBSD",
                         "fuchsia" => "Fuchsia",
                         "haiku" => "Haiku",
+                        "hermit" => "HermitCore",
                         "ios" => "iOS",
                         "l4re" => "L4Re",
                         "linux" => "Linux",

src/libstd/build.rs

@@ -54,5 +54,7 @@ fn main() {
         }
         println!("cargo:rustc-link-lib=c");
         println!("cargo:rustc-link-lib=compiler_rt");
+    } else if target.contains("hermit") {
+        println!("cargo:rustc-link-lib=hermit");
     }
 }