diff --git a/kernel/src/syscall.rs b/kernel/src/syscall.rs
index 00971e3..4f60ca2 100644
--- a/kernel/src/syscall.rs
+++ b/kernel/src/syscall.rs
@@ -53,7 +53,7 @@ pub fn syscall(id: usize, args: [usize; 6], tf: &mut TrapFrame) -> i32 {
     };
     match ret {
         Ok(code) => code,
-        Err(err) => (err as i32),
+        Err(err) => -(err as i32),
     }
 }
 
@@ -96,7 +96,7 @@ fn sys_close(fd: usize) -> SysResult {
     info!("close: fd: {:?}", fd);
     match process().files.remove(&fd) {
         Some(_) => Ok(0),
-        None => Err(SysError::Badf),
+        None => Err(SysError::Inval),
     }
 }
 
@@ -133,7 +133,7 @@ fn sys_dup(fd1: usize, fd2: usize) -> SysResult {
     info!("dup: {} {}", fd1, fd2);
     let file = get_file(fd1)?;
     if process().files.contains_key(&fd2) {
-        return Err(SysError::Badf);
+        return Err(SysError::Inval);
     }
     process().files.insert(fd2, file.clone());
     Ok(0)
@@ -278,7 +278,7 @@ fn sys_putc(c: char) -> SysResult {
 }
 
 fn get_file(fd: usize) -> Result<&'static Arc<Mutex<File>>, SysError> {
-    process().files.get(&fd).ok_or(SysError::Badf)
+    process().files.get(&fd).ok_or(SysError::Inval)
 }
 
 pub type SysResult = Result<i32, SysError>;
@@ -286,23 +286,23 @@ pub type SysResult = Result<i32, SysError>;
 #[repr(i32)]
 #[derive(Debug)]
 pub enum SysError {
-    // ucore_plus compatible error code, which is a modified version of the ones used in linux
-    // note that ucore_os_lab use another error code table
+    // ucore compatible error code
+    // note that ucore_plus use another error code table, which is a modified version of the ones used in linux
     // name conversion E_XXXXX -> SysError::Xxxxx
-    // see https://github.com/oscourse-tsinghua/ucore_plus/blob/master/ucore/src/libs-user-ucore/common/error.h
+    // see https://github.com/oscourse-tsinghua/ucore_os_lab/blob/master/labcodes/lab8/libs/error.h
     // we only add current used errors here
-    Noent = 2,// No such file or directory
-    Badf = 9,// Invaild fd number
-    Nomem = 12,// Out of memory, also used as no device space in ucore
-    Exist = 17,// File exists
-    Xdev = 18,// Cross-device link
-    Notdir = 20,// Fd is not a directory
-    Isdir = 21,// Fd is a directory
-    Inval = 22,// Invalid argument.
-    Unimp = 35,// Not implemented operation
+    Inval = 3,// Invalid argument, also Invaild fd number.
+    Nomem = 4,// Out of memory, also used as no device space in ucore
+    Noent = 16,// No such file or directory
+    Isdir = 17,// Fd is a directory
+    Notdir = 18,// Fd is not a directory
+    Xdev = 19,// Cross-device link
+    Unimp = 20,// Not implemented
+    Exists = 23,// File exists
+    Notempty = 24,// Directory is not empty
 
     #[allow(dead_code)]
-    Unknown = 65535,// A really really unknown error.
+    Unspcified = 1,// A really really unknown error.
 }
 
 impl From<FsError> for SysError {
@@ -313,12 +313,12 @@ impl From<FsError> for SysError {
             FsError::IsDir => SysError::Isdir,
             FsError::NotDir => SysError::Notdir,
             FsError::EntryNotFound => SysError::Noent,
-            FsError::EntryExist => SysError::Exist,
+            FsError::EntryExist => SysError::Exists,
             FsError::NotSameFs => SysError::Xdev,
             FsError::InvalidParam => SysError::Inval,
             FsError::NoDeviceSpace => SysError::Nomem,
             FsError::DirRemoved => SysError::Noent,
-            FsError::DirNotEmpty => SysError::Isdir,// It should be E_NOTEMPTY in linux, but in ucore it is equal to E_Isdir
+            FsError::DirNotEmpty => SysError::Notempty,
             FsError::WrongFs => SysError::Inval,
         }
     }