diff --git a/kernel/Cargo.lock b/kernel/Cargo.lock
index a856fd5..2738127 100644
--- a/kernel/Cargo.lock
+++ b/kernel/Cargo.lock
@@ -282,12 +282,12 @@ dependencies = [
 [[package]]
 name = "rcore-fs"
 version = "0.1.0"
-source = "git+https://github.com/wangrunji0408/rcore-fs?branch=sefs#379a58cd6d5854db31d03c38ddf688adf8c774ed"
+source = "git+https://github.com/wangrunji0408/rcore-fs?branch=sefs#af02ecfb3fb0da641ebe07c37af094c42dd60c2e"
 
 [[package]]
 name = "rcore-fs-sfs"
 version = "0.1.0"
-source = "git+https://github.com/wangrunji0408/rcore-fs?branch=sefs#379a58cd6d5854db31d03c38ddf688adf8c774ed"
+source = "git+https://github.com/wangrunji0408/rcore-fs?branch=sefs#af02ecfb3fb0da641ebe07c37af094c42dd60c2e"
 dependencies = [
  "bitvec 0.9.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.4.6 (registry+https://github.com/rust-lang/crates.io-index)",
diff --git a/kernel/src/syscall/mod.rs b/kernel/src/syscall/mod.rs
index ad2d8f4..953d02c 100644
--- a/kernel/src/syscall/mod.rs
+++ b/kernel/src/syscall/mod.rs
@@ -81,7 +81,7 @@ pub fn syscall(id: usize, args: [usize; 6], tf: &mut TrapFrame) -> isize {
         058 => sys_fork(tf),
         059 => sys_exec(args[0] as *const u8, args[1] as *const *const u8, args[2] as *const *const u8, tf),
         060 => sys_exit(args[0] as isize),
-        061 => sys_wait(args[0], args[1] as *mut i32), // TODO: wait4
+        061 => sys_wait4(args[0] as isize, args[1] as *mut i32), // TODO: wait4
         062 => sys_kill(args[0]),
         063 => sys_uname(args[0] as *mut u8),
 //        072 => sys_fcntl(),
@@ -173,6 +173,10 @@ pub fn syscall(id: usize, args: [usize; 6], tf: &mut TrapFrame) -> isize {
             warn!("sys_exit_group is unimplemented");
             sys_exit(args[0] as isize);
         }
+        280 => {
+            warn!("sys_utimensat is unimplemented");
+            Ok(0)
+        }
         302 => {
             warn!("sys_prlimit64 is unimplemented");
             Ok(0)
diff --git a/kernel/src/syscall/proc.rs b/kernel/src/syscall/proc.rs
index 926b700..0bf6917 100644
--- a/kernel/src/syscall/proc.rs
+++ b/kernel/src/syscall/proc.rs
@@ -12,19 +12,29 @@ pub fn sys_fork(tf: &TrapFrame) -> SysResult {
 
 /// Wait the process exit.
 /// Return the PID. Store exit code to `code` if it's not null.
-pub fn sys_wait(pid: usize, code: *mut i32) -> SysResult {
-    info!("wait: pid {} code {:?}", pid, code);
+pub fn sys_wait4(pid: isize, code: *mut i32) -> SysResult {
+    info!("wait4: pid: {}, code: {:?}", pid, code);
     if !code.is_null() {
         process().memory_set.check_mut_ptr(code)?;
     }
+    #[derive(Debug)]
+    enum WaitFor {
+        AnyChild,
+        Pid(usize),
+    }
+    let target = match pid {
+        -1 => WaitFor::AnyChild,
+        p if p > 0 => WaitFor::Pid(p as usize),
+        _ => unimplemented!(),
+    };
     loop {
         use alloc::vec;
-        let wait_procs = match pid {
-            0 => processor().manager().get_children(thread::current().id()),
-            // check if pid is a child
-            _ => {
+        let wait_procs = match target {
+            WaitFor::AnyChild => processor().manager().get_children(thread::current().id()),
+            WaitFor::Pid(pid) => {
+                // check if pid is a child
                 if processor().manager().get_children(thread::current().id()).iter()
-                    .find(|p| **p == pid).is_some() {
+                    .find(|&&p| p == pid).is_some() {
                     vec![pid]
                 } else {
                     vec![]
@@ -49,14 +59,12 @@ pub fn sys_wait(pid: usize, code: *mut i32) -> SysResult {
                 _ => {}
             }
         }
-        info!("wait: {} -> {}, sleep", thread::current().id(), pid);
-        if pid == 0 {
-            processor().manager().wait_child(thread::current().id());
-            processor().yield_now();
-        } else {
-            processor().manager().wait(thread::current().id(), pid);
-            processor().yield_now();
+        info!("wait: {} -> {:?}, sleep", thread::current().id(), target);
+        match target {
+            WaitFor::AnyChild => processor().manager().wait_child(thread::current().id()),
+            WaitFor::Pid(pid) => processor().manager().wait(thread::current().id(), pid),
         }
+        processor().yield_now();
     }
 }