refactor: gate x86_64-specific code in hyperlight-guest-bin

- Gate paging and exception modules on target_arch = x86_64
- Gate ProfiledLockedHeap (uses x86 out asm) on x86_64
- Skip musl/printf C compilation in build.rs on non-x86_64

Signed-off-by: Ludvig Liljenberg <4257730+ludfjig@users.noreply.github.com>

Author: ludfjig

src/hyperlight_guest_bin/build.rs

@@ -42,12 +42,17 @@ fn copy_includes<P: AsRef<Path>, Q: AsRef<Path> + std::fmt::Debug>(include_dir:
 fn cargo_main() {
     println!("cargo:rerun-if-changed=third_party");
 
-    let mut cfg = cc::Build::new();
+    let target = env::var("TARGET").unwrap_or_default();
+    let is_x86_64 = target.starts_with("x86_64");
 
-    if cfg!(feature = "printf") {
-        cfg.include("third_party/printf")
-            .file("third_party/printf/printf.c");
-    }
+    // Skip C/musl compilation on aarch64 — no musl support yet
+    if is_x86_64 {
+        let mut cfg = cc::Build::new();
+
+        if cfg!(feature = "printf") {
+            cfg.include("third_party/printf")
+                .file("third_party/printf/printf.c");
+        }
 
     if cfg!(feature = "libc") {
         let entries = glob::glob("third_party/musl/**/*.[cs]") // .c and .s files
@@ -108,19 +113,22 @@ fn cargo_main() {
         }
         cfg.compile("hyperlight_guest_bin");
     }
+    } // end if is_x86_64
 
     let out_dir = env::var("OUT_DIR").expect("cargo OUT_DIR not set");
     let include_dir = PathBuf::from(&out_dir).join("include");
     fs::create_dir_all(&include_dir)
         .unwrap_or_else(|e| panic!("Could not create include dir {:?}: {}", &include_dir, e));
-    if cfg!(feature = "printf") {
-        copy_includes(&include_dir, "third_party/printf/");
-    }
-    if cfg!(feature = "libc") {
-        copy_includes(&include_dir, "third_party/musl/include");
-        copy_includes(&include_dir, "third_party/musl/arch/generic");
-        copy_includes(&include_dir, "third_party/musl/arch/x86_64");
-        copy_includes(&include_dir, "third_party/musl/src/internal");
+    if is_x86_64 {
+        if cfg!(feature = "printf") {
+            copy_includes(&include_dir, "third_party/printf/");
+        }
+        if cfg!(feature = "libc") {
+            copy_includes(&include_dir, "third_party/musl/include");
+            copy_includes(&include_dir, "third_party/musl/arch/generic");
+            copy_includes(&include_dir, "third_party/musl/arch/x86_64");
+            copy_includes(&include_dir, "third_party/musl/src/internal");
+        }
     }
     /* do not canonicalize: clang has trouble with UNC paths */
     let include_str = include_dir

src/hyperlight_guest_bin/src/lib.rs

@@ -34,6 +34,7 @@ use hyperlight_guest::guest_handle::handle::GuestHandle;
 
 // === Modules ===
 #[cfg_attr(target_arch = "x86_64", path = "arch/amd64/mod.rs")]
+#[cfg_attr(target_arch = "aarch64", path = "arch/aarch64/mod.rs")]
 mod arch;
 // temporarily expose the architecture-specific exception interface;
 // this should be replaced with something a bit more abstract in the
@@ -49,12 +50,13 @@ pub mod guest_function {
 pub mod guest_logger;
 pub mod host_comm;
 pub mod memory;
+#[cfg(target_arch = "x86_64")]
 pub mod paging;
 
 // Globals
-#[cfg(feature = "mem_profile")]
+#[cfg(all(feature = "mem_profile", target_arch = "x86_64"))]
 struct ProfiledLockedHeap<const ORDER: usize>(LockedHeap<ORDER>);
-#[cfg(feature = "mem_profile")]
+#[cfg(all(feature = "mem_profile", target_arch = "x86_64"))]
 unsafe impl<const ORDER: usize> alloc::alloc::GlobalAlloc for ProfiledLockedHeap<ORDER> {
     unsafe fn alloc(&self, layout: core::alloc::Layout) -> *mut u8 {
         let addr = unsafe { self.0.alloc(layout) };
@@ -107,10 +109,10 @@ unsafe impl<const ORDER: usize> alloc::alloc::GlobalAlloc for ProfiledLockedHeap
 }
 
 // === Globals ===
-#[cfg(not(feature = "mem_profile"))]
+#[cfg(not(all(feature = "mem_profile", target_arch = "x86_64")))]
 #[global_allocator]
 pub(crate) static HEAP_ALLOCATOR: LockedHeap<32> = LockedHeap::<32>::empty();
-#[cfg(feature = "mem_profile")]
+#[cfg(all(feature = "mem_profile", target_arch = "x86_64"))]
 #[global_allocator]
 pub(crate) static HEAP_ALLOCATOR: ProfiledLockedHeap<32> =
     ProfiledLockedHeap(LockedHeap::<32>::empty());
@@ -191,9 +193,9 @@ pub(crate) extern "C" fn generic_init(
 
         let heap_start = (*peb_ptr).guest_heap.ptr as usize;
         let heap_size = (*peb_ptr).guest_heap.size as usize;
-        #[cfg(not(feature = "mem_profile"))]
+        #[cfg(not(all(feature = "mem_profile", target_arch = "x86_64")))]
         let heap_allocator = &HEAP_ALLOCATOR;
-        #[cfg(feature = "mem_profile")]
+        #[cfg(all(feature = "mem_profile", target_arch = "x86_64"))]
         let heap_allocator = &HEAP_ALLOCATOR.0;
         heap_allocator
             .try_lock()