diff --git a/src/kxos-frame/src/vm/space.rs b/src/kxos-frame/src/vm/space.rs
index 07c54b2df..a081cd109 100644
--- a/src/kxos-frame/src/vm/space.rs
+++ b/src/kxos-frame/src/vm/space.rs
@@ -48,9 +48,9 @@ impl VmSpace {
         if options.perm.contains(VmPerm::W) {
             flags.insert(PTFlags::WRITABLE);
         }
-        if options.perm.contains(VmPerm::U) {
+        // if options.perm.contains(VmPerm::U) {
             flags.insert(PTFlags::USER);
-        }
+        // }
         if options.addr.is_none() {
             return Err(Error::InvalidArgs);
         }
diff --git a/src/kxos-std/src/syscall/mod.rs b/src/kxos-std/src/syscall/mod.rs
index c1f80f822..bff5ad64b 100644
--- a/src/kxos-std/src/syscall/mod.rs
+++ b/src/kxos-std/src/syscall/mod.rs
@@ -70,8 +70,7 @@ pub fn sys_write(fd: u64, user_buf_ptr: u64, user_buf_len: u64) -> SyscallResult
         let user_buffer =
             copy_bytes_from_user(user_space, user_buf_ptr as usize, user_buf_len as usize)
                 .expect("read user buffer failed");
-        let content = CString::from_vec_with_nul(user_buffer).expect("read string failed");
-        // TODO: print content
+        let content = alloc::str::from_utf8(user_buffer.as_slice()).expect("Invalid content");        // TODO: print content
         info!("Message from user mode: {:?}", content);
         SyscallResult::Return(0)
     } else {
diff --git a/src/kxos-user/hello_world/hello_world.s b/src/kxos-user/hello_world/hello_world.s
index 5765e27a8..c55da226b 100644
--- a/src/kxos-user/hello_world/hello_world.s
+++ b/src/kxos-user/hello_world/hello_world.s
@@ -3,7 +3,7 @@ global _start
 section .text
 
 _start:
-  mov rax, 64        ; syswrite
+  mov rax, 1        ; syswrite
   mov rdi, 1        ; fd
   mov rsi, msg      ; "Hello, world!\n",
   mov rdx, msglen   ; sizeof("Hello, world!\n")