feat: add SavedContext::with_entry_and_stack, wire SpawnThread to preserve entry point and stack

crates/kernel/src/tests/lifecycle.rs

@@ -3,6 +3,7 @@ use crate::{SyscallOutcome, SyscallResult};
 use domain::syscall::Syscall;
 use types::address::{DataRef, EntryPoint, StackPointer};
 use types::bounded::CapSlot;
+use types::id::ThreadId;
 
 #[test]
 fn spawn_thread_creates_ready_thread() {
@@ -17,6 +18,21 @@ fn spawn_thread_creates_ready_thread() {
     ));
 }
 
+#[test]
+fn spawn_thread_preserves_entry_and_stack() {
+    let (mut k, _) = kernel_with_process();
+    let tid = match k.handle_syscall(Syscall::SpawnThread {
+        entry: EntryPoint::from_raw(0xDEAD),
+        stack: StackPointer::from_raw(0xBEEF),
+    }) {
+        SyscallOutcome::Complete(SyscallResult::Value(v)) => ThreadId::from_raw(v as u16),
+        _ => panic!("expected Value"),
+    };
+    let ctx = k.thread_context(tid);
+    assert_eq!(ctx.program_counter(), 0xDEAD);
+    assert_eq!(ctx.stack_pointer(), 0xBEEF);
+}
+
 #[test]
 fn create_process_with_cap_succeeds() {
     let (mut k, _) = kernel_with_process();