diff --git a/src/kxos-std/src/lib.rs b/src/kxos-std/src/lib.rs
index 187cfd8d..5c13357d 100644
--- a/src/kxos-std/src/lib.rs
+++ b/src/kxos-std/src/lib.rs
@@ -6,7 +6,7 @@
 #![feature(const_btree_new)]
 #![feature(cstr_from_bytes_until_nul)]
 
-use kxos_frame::println;
+use kxos_frame::{println, info, task::Task};
 use process::Process;
 
 extern crate alloc;
@@ -20,15 +20,26 @@ pub fn init() {
     process::fifo_scheduler::init();
 }
 
-pub fn run_first_kernel_task() {
-    Process::spawn_kernel_task(|| {
-        println!("hello world from kernel");
+pub fn init_task() {
+    println!("[kernel] Hello world from init task!");
+
+    let process = Process::spawn_kernel_task(|| {
+        println!("[kernel] Hello world from kernel!");
     });
+    info!("spawn kernel process, pid = {}", process.pid());
+
+    let elf_file_content = read_elf_content();
+    let process = Process::spawn_from_elf(elf_file_content);
+    info!("spwan user process, pid = {}", process.pid());
+    
+    loop {}
 }
 
-pub fn run_first_process() {
+/// first process never return
+pub fn run_first_process() -> ! {
     let elf_file_content = read_elf_content();
-    Process::spawn_from_elf(elf_file_content);
+    Task::spawn(init_task, None::<u8>, None).expect("Spawn first task failed");
+    unreachable!()
 }
 
 fn read_elf_content() -> &'static [u8] {
diff --git a/src/kxos-std/src/memory/user_stack.rs b/src/kxos-std/src/memory/user_stack.rs
index 321be355..e7c57b92 100644
--- a/src/kxos-std/src/memory/user_stack.rs
+++ b/src/kxos-std/src/memory/user_stack.rs
@@ -1,4 +1,3 @@
-use alloc::sync::Arc;
 use kxos_frame::vm::{Vaddr, VmPerm, VmSpace};
 
 use super::vm_page::VmPageRange;
@@ -8,9 +7,8 @@ pub const USER_STACK_SIZE: usize = 0x1000 * 16; // 64KB
 
 pub struct UserStack {
     /// The low address of user stack
-    pub stack_base: Vaddr,
+    stack_base: Vaddr,
     stack_size: usize,
-    vm_space: Option<Arc<VmSpace>>,
 }
 
 impl UserStack {
@@ -19,7 +17,6 @@ impl UserStack {
         Self {
             stack_base,
             stack_size,
-            vm_space: None,
         }
     }
 
@@ -28,7 +25,6 @@ impl UserStack {
         Self {
             stack_base: USER_STACK_BASE,
             stack_size: USER_STACK_SIZE,
-            vm_space: None,
         }
     }
 
diff --git a/src/kxos-std/src/process/mod.rs b/src/kxos-std/src/process/mod.rs
index b9445d2c..f5fc912a 100644
--- a/src/kxos-std/src/process/mod.rs
+++ b/src/kxos-std/src/process/mod.rs
@@ -2,7 +2,7 @@ use core::sync::atomic::{AtomicUsize, Ordering};
 
 use alloc::sync::Arc;
 // use kxos_frame::{sync::SpinLock, task::Task, user::UserSpace};
-use kxos_frame::{debug, task::Task};
+use kxos_frame::task::Task;
 
 use self::task::spawn_user_task_from_elf;
 
@@ -39,8 +39,7 @@ impl Process {
         F: Fn() + Send + Sync + 'static,
     {
         let pid = new_pid();
-        debug!("pid = {}", pid);
-        let task = Task::spawn(task_fn, None::<u8>, None).expect("spawn kernel task failed");
+        let task = Task::spawn(task_fn, pid, None).expect("spawn kernel task failed");
         let exit_code = 0;
         Self {
             pid,
@@ -48,6 +47,10 @@ impl Process {
             exit_code,
         }
     }
+
+    pub fn pid(&self) -> usize {
+        self.pid
+    }
 }
 
 /// create a new pid for new process
diff --git a/src/kxos-std/src/process/task.rs b/src/kxos-std/src/process/task.rs
index 16807f22..86b84eb0 100644
--- a/src/kxos-std/src/process/task.rs
+++ b/src/kxos-std/src/process/task.rs
@@ -25,6 +25,7 @@ pub fn spawn_user_task_from_elf(elf_file_content: &[u8]) -> Arc<Task> {
         let cur = Task::current();
         let user_space = cur.user_space().expect("user task should have user space");
         let mut user_mode = UserMode::new(user_space);
+        debug!("in user task");
         loop {
             let user_event = user_mode.execute();
             debug!("return from user mode");
diff --git a/src/kxos-user/hello_world/hello_world.s b/src/kxos-user/hello_world/hello_world.s
index 0baea631..58e8783c 100644
--- a/src/kxos-user/hello_world/hello_world.s
+++ b/src/kxos-user/hello_world/hello_world.s
@@ -2,20 +2,18 @@
 
 .section .text
 _start:
-    call print_message
-    call print_message
-    call print_message
+    call    print_message
+    call    print_message
+    call    print_message
     mov     $60, %rax               # syscall number of exit
-    mov     $0, %rdi                 # exit code
+    mov     $0, %rdi                # exit code
     syscall     
 print_message:
     mov     $1, %rax                # syscall number of write
     mov     $1, %rdi                # stdout
-    mov     $message, %rsi          # address of message
-    mov     $message, %r11          
-    mov     $message_end, %r12
-    sub     %r11, %r12               # calculate message len
-    mov     %r12, %rdx               # number of bytes
+    mov     $message, %rsi          # address of message         
+    mov     $message_end, %rdx
+    sub     %rsi, %rdx              # calculate message len
     syscall
     ret
 .section .rodata            
diff --git a/src/src/main.rs b/src/src/main.rs
index 6ec11ab8..4c4cfc9d 100644
--- a/src/src/main.rs
+++ b/src/src/main.rs
@@ -20,8 +20,6 @@ fn kernel_main(boot_info: &'static mut BootInfo) -> ! {
 
     kxos_std::init();
     kxos_std::run_first_process();
-
-    loop {}
 }
 #[cfg(not(test))]
 #[panic_handler]