Auto merge of #65167 - hermitcore:rusty-hermit, r=alexcrichton

Redesign the interface to the unikernel HermitCore

We are developing the unikernel HermitCore, where the kernel is written in Rust and is already part of the Rust Standard Library. The interface between the standard library and the kernel based on a small C library. With this pull request, we remove completely the dependency to C and use lld as linker. Currently, the kernel will be linked to the application as static library, which is published at https://github.com/hermitcore/libhermit-rs.

We don’t longer support the C interface to the kernel. Consequently, we remove this part from the Rust Standard Library.

Cargo.lock

@@ -1328,6 +1328,17 @@ dependencies = [
  "unicode-segmentation",
 ]
 
+[[package]]
+name = "hermit-abi"
+version = "0.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f22b8f315b98f415780ddbe9163c7dbbc5a07225b6d102ace1d8aeef85775140"
+dependencies = [
+ "compiler_builtins",
+ "libc",
+ "rustc-std-workspace-core",
+]
+
 [[package]]
 name = "hex"
 version = "0.3.2"
@@ -4159,6 +4170,7 @@ dependencies = [
  "dlmalloc",
  "fortanix-sgx-abi",
  "hashbrown 0.6.2",
+ "hermit-abi",
  "libc",
  "panic_abort",
  "panic_unwind",

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/Cargo.toml

@@ -50,6 +50,9 @@ dlmalloc = { version = "0.1", features = ['rustc-dep-of-std'] }
 [target.x86_64-fortanix-unknown-sgx.dependencies]
 fortanix-sgx-abi = { version = "0.3.2", features = ['rustc-dep-of-std'] }
 
+[target.'cfg(all(any(target_arch = "x86_64", target_arch = "aarch64"), target_os = "hermit"))'.dependencies]
+hermit-abi = { version = "0.1", features = ['rustc-dep-of-std'] }
+
 [target.wasm32-wasi.dependencies]
 wasi = { version = "0.7.0", features = ['rustc-dep-of-std', 'alloc'] }
 

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");
     }
 }