Finish port

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

@@ -1,11 +1,15 @@
-use crate::spec::{PanicStrategy, RelocModel, TargetOptions, crt_objects};
+use crate::spec::{
+    Cc, LinkerFlavor, Lld, PanicStrategy, RelocModel, StackProbeType, TargetOptions,
+};
 
 pub(crate) fn opts() -> TargetOptions {
     TargetOptions {
         os: "os".into(),
+        linker: Some("rust-lld".into()),
+        linker_flavor: LinkerFlavor::Gnu(Cc::No, Lld::Yes),
         relocation_model: RelocModel::Static,
         panic_strategy: PanicStrategy::Abort,
-        pre_link_objects: crt_objects::pre_os(),
+        stack_probes: StackProbeType::Inline,
         ..Default::default()
     }
 }

compiler/rustc_target/src/spec/crt_objects.rs

@@ -122,7 +122,3 @@ pub(super) fn pre_wasi_self_contained() -> CrtObjects {
 pub(super) fn post_wasi_self_contained() -> CrtObjects {
     new(&[])
 }
-
-pub(super) fn pre_os() -> CrtObjects {
-    all("crt0.o")
-}

library/std/src/sys/pal/osstd/mod.rs

@@ -1,5 +1,7 @@
 #![deny(unsafe_op_in_unsafe_fn)]
 
+use core::arch::global_asm;
+
 pub mod args;
 pub mod env;
 pub mod fs;
@@ -14,3 +16,20 @@ pub mod time;
 
 mod common;
 pub use common::*;
+
+global_asm!(
+    "
+.text
+
+.global _start
+_start:
+  mov $stack, %rsp
+  call main
+
+.section .bss
+.align 16
+.skip 0x10000
+stack:
+",
+    options(att_syntax)
+);

src/bootstrap/src/lib.rs

@@ -665,7 +665,7 @@ impl Build {
         }
         // Generate memcpy, etc.  FIXME: Remove this once compiler-builtins
         // automatically detects this target.
-        if target.contains("zkvm") {
+        if target.contains("zkvm") || target.contains("os") {
             features.insert("compiler-builtins-mem");
         }