From 74b296a2bfc34de1c6dcd34f9372380d9d523e0b Mon Sep 17 00:00:00 2001
From: Gabriel Kaszewski <gabrielkaszewski@gmail.com>
Date: Sun, 18 Oct 2026 00:16:38 +0200
Subject: [PATCH] feat(kernel): add Exit and ExitThread syscalls with process
 cleanup

---
 crates/kernel/src/lib.rs        |  4 +++
 crates/kernel/src/syscall.rs    | 50 +++++++++++++++++++++++++++++++++
 crates/kernel/src/tests/exit.rs | 25 +++++++++++++++++
 crates/kernel/src/tests/mod.rs  |  1 +
 4 files changed, 80 insertions(+)
 create mode 100644 crates/kernel/src/tests/exit.rs

diff --git a/crates/kernel/src/lib.rs b/crates/kernel/src/lib.rs
index dd29b91..ac7539a 100644
--- a/crates/kernel/src/lib.rs
+++ b/crates/kernel/src/lib.rs
@@ -125,6 +125,10 @@ impl<P: Platform> Kernel<P> {
         }
     }
 
+    pub fn process_exists(&self, pid: ProcessId) -> bool {
+        self.processes.get(pid).is_ok()
+    }
+
     fn check_cap(
         &self,
         owner: ProcessId,
diff --git a/crates/kernel/src/syscall.rs b/crates/kernel/src/syscall.rs
index a1e2af2..ce18d93 100644
--- a/crates/kernel/src/syscall.rs
+++ b/crates/kernel/src/syscall.rs
@@ -14,6 +14,8 @@ impl<P: Platform> Kernel<P> {
             Syscall::GetTime => self.handle_get_time(),
             Syscall::GetProcessId => self.handle_get_process_id(pid),
             Syscall::Yield => self.handle_yield(tid),
+            Syscall::Exit => self.handle_exit(tid, pid),
+            Syscall::ExitThread => self.handle_exit_thread(tid, pid),
             _ => SyscallOutcome::Complete(SyscallResult::Error(
                 domain::error::KernelError::WouldBlock,
             )),
@@ -29,6 +31,54 @@ impl<P: Platform> Kernel<P> {
         SyscallOutcome::Complete(SyscallResult::Value(pid.raw() as usize))
     }
 
+    fn handle_exit(&mut self, caller_tid: types::id::ThreadId, pid: types::id::ProcessId) -> SyscallOutcome {
+        use domain::scheduler::Scheduler;
+
+        // Kill all threads of this process
+        let thread_ids: [Option<types::id::ThreadId>; 4] = {
+            match self.processes.get(pid) {
+                Ok(p) => {
+                    let mut ids = [None; 4];
+                    for (i, tid) in p.thread_ids().enumerate() {
+                        if i < 4 {
+                            ids[i] = Some(tid);
+                        }
+                    }
+                    ids
+                }
+                Err(_) => return SyscallOutcome::TerminateCaller,
+            }
+        };
+
+        for slot in &thread_ids {
+            if let Some(tid) = slot {
+                self.scheduler.remove(*tid);
+                let _ = self.threads.destroy(*tid);
+            }
+        }
+
+        let _ = self.processes.destroy(pid);
+        self.process_memory[pid.raw() as usize] = None;
+        SyscallOutcome::TerminateCaller
+    }
+
+    fn handle_exit_thread(&mut self, caller_tid: types::id::ThreadId, pid: types::id::ProcessId) -> SyscallOutcome {
+        use domain::scheduler::Scheduler;
+
+        self.scheduler.remove(caller_tid);
+        let _ = self.threads.destroy(caller_tid);
+
+        if let Ok(process) = self.processes.get_mut(pid) {
+            process.remove_thread(caller_tid);
+            if process.thread_ids().count() == 0 {
+                let _ = self.processes.destroy(pid);
+                self.process_memory[pid.raw() as usize] = None;
+            }
+        }
+
+        SyscallOutcome::TerminateCaller
+    }
+
     fn handle_yield(&mut self, caller_tid: types::id::ThreadId) -> SyscallOutcome {
         use domain::scheduler::Scheduler;
 
diff --git a/crates/kernel/src/tests/exit.rs b/crates/kernel/src/tests/exit.rs
new file mode 100644
index 0000000..423d134
--- /dev/null
+++ b/crates/kernel/src/tests/exit.rs
@@ -0,0 +1,25 @@
+use super::*;
+use crate::{SyscallOutcome, SyscallResult};
+use domain::syscall::Syscall;
+
+#[test]
+fn exit_thread_terminates_caller() {
+    let (mut k, _) = kernel_with_process();
+    let outcome = k.handle_syscall(Syscall::ExitThread);
+    assert!(matches!(outcome, SyscallOutcome::TerminateCaller));
+}
+
+#[test]
+fn exit_terminates_process_and_all_threads() {
+    let (mut k, _) = kernel_with_process();
+    let outcome = k.handle_syscall(Syscall::Exit);
+    assert!(matches!(outcome, SyscallOutcome::TerminateCaller));
+}
+
+#[test]
+fn exit_thread_last_thread_destroys_process() {
+    let (mut k, pid) = kernel_with_process();
+    k.handle_syscall(Syscall::ExitThread);
+    // Process should be gone since it had only one thread
+    assert!(k.process_exists(pid) == false);
+}
diff --git a/crates/kernel/src/tests/mod.rs b/crates/kernel/src/tests/mod.rs
index 6aacb27..2a94df6 100644
--- a/crates/kernel/src/tests/mod.rs
+++ b/crates/kernel/src/tests/mod.rs
@@ -1,3 +1,4 @@
+mod exit;
 mod simple;
 
 use domain::memory::page_pool::PagePool;