Handle exit status correctly

src/libos/src/lib.rs

@@ -49,10 +49,10 @@ pub extern "C" fn libos_boot(path_buf: *const i8) -> i32 {
         backtrace::__rust_begin_short_backtrace(||{
             match do_boot(&path_str) {
                 Ok(()) => 0,
-                Err(err) => err.errno.as_retval() /* Normal error */,
+                Err(err) => EXIT_STATUS_INTERNAL_ERROR,
             }
         })
-    }).unwrap_or(-1 /* Fatal error */)
+    }).unwrap_or(EXIT_STATUS_INTERNAL_ERROR)
 }
 
 #[no_mangle]
@@ -61,13 +61,16 @@ pub extern "C" fn libos_run() -> i32 {
     panic::catch_unwind(||{
         backtrace::__rust_begin_short_backtrace(||{
             match do_run() {
-                Ok(()) => 0,
+                Ok(exit_status) => exit_status,
-                Err(err) => err.errno.as_retval() /* Normal error */,
+                Err(err) => EXIT_STATUS_INTERNAL_ERROR,
             }
         })
-    }).unwrap_or(-1 /* Fatal error */)
+    }).unwrap_or(EXIT_STATUS_INTERNAL_ERROR)
 }
 
+// Use 127 as a special value to indicate internal error from libos, not from
+// user programs, although it is completely ok for a user program to return 127.
+const EXIT_STATUS_INTERNAL_ERROR : i32 = 127;
 
 // TODO: make sure do_boot can only be called once
 fn do_boot(path_str: &str) -> Result<(), Error> {
@@ -81,7 +84,7 @@ fn do_boot(path_str: &str) -> Result<(), Error> {
 }
 
 // TODO: make sure do_run() cannot be called before do_boot()
-fn do_run() -> Result<(), Error> {
+fn do_run() -> Result<i32, Error> {
-    process::run_task()?;
+    let exit_status = process::run_task()?;
-    Ok(())
+    Ok(exit_status)
 }

src/libos/src/process/mod.rs

@@ -11,21 +11,21 @@ pub fn do_getpid() -> pid_t {
     current_process.get_pid()
 }
 
-pub fn do_exit(exit_code: i32) {
+pub fn do_exit(exit_status: i32) {
     let current_ref = get_current();
     let mut current_process = current_ref.lock().unwrap();
-    current_process.exit(exit_code);
+    current_process.exit(exit_status);
 }
 
 pub fn do_wait4(child_pid: u32) -> Result<i32, Error> {
     let child_process = process_table::get(child_pid)
         .ok_or_else(|| (Errno::ECHILD, "Cannot find child process with the given PID"))?;
 
-    let mut exit_code = 0;
+    let mut exit_status = 0;
     loop {
         let guard = child_process.lock().unwrap();
         if guard.get_status() == Status::ZOMBIE {
-            exit_code = guard.get_exit_code();
+            exit_status = guard.get_exit_status();
             break;
         }
         drop(guard);
@@ -34,7 +34,7 @@ pub fn do_wait4(child_pid: u32) -> Result<i32, Error> {
     let child_pid = child_process.lock().unwrap().get_pid();
     process_table::remove(child_pid);
 
-    Ok(exit_code)
+    Ok(exit_status)
 }
 
 mod task;

src/libos/src/process/process.rs

@@ -12,7 +12,7 @@ pub struct Process {
     status: Status,
     pid: pid_t,
     tgid: pid_t,
-    exit_code: i32,
+    exit_status: i32,
     exec_path: String,
     vm: ProcessVM,
     file_table: FileTable,
@@ -31,7 +31,7 @@ impl Process {
             pid: new_pid,
             tgid: new_pid,
             exec_path: exec_path.to_owned(),
-            exit_code: 0,
+            exit_status: 0,
             vm: vm,
             file_table: file_table,
         }));
@@ -43,15 +43,15 @@ impl Process {
     pub fn get_pid(&self) -> pid_t { self.pid }
     pub fn get_tgid(&self) -> pid_t { self.tgid }
     pub fn get_status(&self) -> Status { self.status }
-    pub fn get_exit_code(&self) -> i32 { self.exit_code }
+    pub fn get_exit_status(&self) -> i32 { self.exit_status }
     pub fn get_exec_path(&self) -> &str { &self.exec_path }
     pub fn get_vm(&self) -> &ProcessVM { &self.vm }
     pub fn get_vm_mut(&mut self) -> &mut ProcessVM { &mut self.vm }
     pub fn get_files(&self) -> &FileTable { &self.file_table }
     pub fn get_files_mut(&mut self) -> &mut FileTable { &mut self.file_table }
 
-    pub fn exit(&mut self, exit_code: i32) {
+    pub fn exit(&mut self, exit_status: i32) {
-        self.exit_code = exit_code;
+        self.exit_status = exit_status;
         self.status = Status::ZOMBIE;
     }
 }

src/libos/src/process/task.rs

@@ -34,7 +34,7 @@ fn dequeue_task() -> Option<ProcessRef> {
 }
 
 
-pub fn run_task() -> Result<(), Error> {
+pub fn run_task() -> Result<i32, Error> {
     let new_process : ProcessRef = dequeue_task()
         .ok_or_else(|| (Errno::EAGAIN, "No new processes to run"))?;
     set_current(&new_process);
@@ -51,13 +51,18 @@ pub fn run_task() -> Result<(), Error> {
         do_run_task(task);
     }
 
+    let exit_status = {
+        let mut process = new_process.lock().unwrap();
+        process.get_exit_status()
+    };
+
     // Init process does not have any parent, so it has to release itself
     if pid == 1 {
         process_table::remove(1);
     }
 
     reset_current();
-    Ok(())
+    Ok(exit_status)
 }
 
 

src/libos/src/syscall/mod.rs

@@ -370,12 +370,12 @@ pub extern "C" fn occlum_spawn(
 }
 
 #[no_mangle]
-pub extern "C" fn occlum_wait4(child_pid: c_int, _exit_code: *mut c_int,
+pub extern "C" fn occlum_wait4(child_pid: c_int, _exit_status: *mut c_int,
     options: c_int/*, rusage: *mut Rusage*/) -> c_int
 {
     match process::do_wait4(child_pid as u32) {
-        Ok(exit_code) => unsafe {
+        Ok(exit_status) => unsafe {
-            *_exit_code = exit_code;
+            *_exit_status = exit_status;
             0
         }
         Err(e) => {

src/pal/pal.c

@@ -225,7 +225,7 @@ int SGX_CDECL main(int argc, char *argv[])
     sgx_ret = libos_boot(global_eid, &status, executable_path);
     if(sgx_ret != SGX_SUCCESS) {
         print_error_message(sgx_ret);
-        return -1;
+        return status;
     }
 
     status = wait_all_tasks();