diff --git a/user/rcore-ulib/src/io.rs b/user/rcore-ulib/src/io.rs
index fa456a6..cf6c4a1 100644
--- a/user/rcore-ulib/src/io.rs
+++ b/user/rcore-ulib/src/io.rs
@@ -2,7 +2,7 @@ use alloc::string::String;
 use core::fmt::{self, Write};
 use core::option::Option;
 
-use crate::syscall::{sys_putc, sys_read, sys_write};
+use crate::syscall::{sys_read, sys_write};
 
 pub const STDIN: usize = 0;
 pub const STDOUT: usize = 1;
@@ -24,10 +24,6 @@ pub fn print(args: fmt::Arguments) {
     StdOut.write_fmt(args).unwrap();
 }
 
-pub fn print_putc(args: fmt::Arguments) {
-    SysPutc.write_fmt(args).unwrap();
-}
-
 pub fn getc() -> Option<u8> {
     let mut c = 0u8;
     let ret = sys_read(STDIN, &mut c, 1);
@@ -68,13 +64,11 @@ pub fn get_line() -> String {
 }
 
 pub fn putc(c: u8) {
-    sys_putc(c);
+    sys_write(STDOUT, &c, 1);
 }
 
 struct StdOut;
 
-struct SysPutc;
-
 impl fmt::Write for StdOut {
     fn write_str(&mut self, s: &str) -> fmt::Result {
         if sys_write(STDOUT, s.as_ptr(), s.len()) >= 0 {
@@ -85,15 +79,6 @@ impl fmt::Write for StdOut {
     }
 }
 
-impl fmt::Write for SysPutc {
-    fn write_str(&mut self, s: &str) -> fmt::Result {
-        for c in s.bytes() {
-            sys_putc(c);
-        }
-        Ok(())
-    }
-}
-
 /* VFS flags */
 // TODO: use bitflags
 // flags for open: choose one of these
diff --git a/user/rcore-ulib/src/lang_items.rs b/user/rcore-ulib/src/lang_items.rs
index 613db41..f125f8c 100644
--- a/user/rcore-ulib/src/lang_items.rs
+++ b/user/rcore-ulib/src/lang_items.rs
@@ -1,17 +1,10 @@
-use crate::syscall::{sys_close, sys_dup, sys_exit, sys_open};
+use crate::syscall::{sys_close, sys_dup2, sys_exit, sys_open};
 use crate::io::{O_RDONLY, O_WRONLY, STDIN, STDOUT};
 use crate::ALLOCATOR;
 
 use core::alloc::Layout;
 use core::panic::PanicInfo;
 
-// used for panic
-macro_rules! print {
-    ($($arg:tt)*) => ({
-        $crate::io::print_putc(format_args!($($arg)*));
-    });
-}
-
 #[linkage = "weak"]
 #[no_mangle]
 fn main() {
@@ -27,7 +20,7 @@ fn initfd(fd2: usize, path: &str, open_flags: usize) -> i32 {
     let fd1 = fd1 as usize;
     if fd1 != fd2 {
         sys_close(fd2);
-        ret = sys_dup(fd1, fd2);
+        ret = sys_dup2(fd1, fd2);
         sys_close(fd1);
     }
     return ret;
diff --git a/user/rcore-ulib/src/syscall.rs b/user/rcore-ulib/src/syscall.rs
index 5c21bcd..b674201 100644
--- a/user/rcore-ulib/src/syscall.rs
+++ b/user/rcore-ulib/src/syscall.rs
@@ -17,7 +17,7 @@ fn sys_call(syscall_id: SyscallId, arg0: usize, arg1: usize, arg2: usize, arg3:
             : "memory"
             : "intel" "volatile");
         #[cfg(target_arch = "x86_64")]
-            asm!("int 0x40"
+            asm!("syscall"
             : "={rax}" (ret)
             : "{rax}" (id), "{rdi}" (arg0), "{rsi}" (arg1), "{rdx}" (arg2), "{rcx}" (arg3), "{r8}" (arg4), "{r9}" (arg5)
             : "memory"
@@ -64,8 +64,8 @@ pub fn sys_close(fd: usize) -> i32 {
     sys_call(SyscallId::Close, fd, 0, 0, 0, 0, 0)
 }
 
-pub fn sys_dup(fd1: usize, fd2: usize) -> i32 {
-    sys_call(SyscallId::Dup, fd1, fd2, 0, 0, 0, 0)
+pub fn sys_dup2(fd1: usize, fd2: usize) -> i32 {
+    sys_call(SyscallId::Dup2, fd1, fd2, 0, 0, 0, 0)
 }
 
 /// Fork the current process. Return the child's PID.
@@ -101,40 +101,33 @@ pub fn sys_get_time() -> i32 {
     sys_call(SyscallId::GetTime, 0, 0, 0, 0, 0, 0)
 }
 
-pub fn sys_lab6_set_priority(priority: usize) -> i32 {
-    sys_call(SyscallId::Lab6SetPriority, priority, 0, 0, 0, 0, 0)
-}
-
-pub fn sys_putc(c: u8) -> i32 {
-    sys_call(SyscallId::Putc, c as usize, 0, 0, 0, 0, 0)
+pub fn sys_set_priority(priority: usize) -> i32 {
+    sys_call(SyscallId::SetPriority, priority, 0, 0, 0, 0, 0)
 }
 
 #[allow(dead_code)]
-enum SyscallId{
-    Exit = 1,
-    Fork = 2,
-    Wait = 3,
-    Exec = 4,
-    Clone = 5,
-    Yield = 10,
-    Sleep = 11,
-    Kill = 12,
-    GetTime = 17,
-    GetPid = 18,
-    Mmap = 20,
-    Munmap = 21,
-    Shmem = 22,
-    Putc = 30,
-    Pgdir = 31,
-    Open = 100,
-    Close = 101,
-    Read = 102,
-    Write = 103,
-    Seek = 104,
-    Fstat = 110,
-    Fsync = 111,
-    GetCwd = 121,
-    GetDirEntry = 128,
-    Dup = 130,
-    Lab6SetPriority = 255,
+enum SyscallId {
+    Exit = 60,
+    Fork = 57,
+    Wait = 61,
+    Exec = 59,
+    Clone = 56,
+    Yield = 24,
+    Sleep = 35,
+    Kill = 62,
+    GetTime = 96,
+    GetPid = 39,
+    Mmap = 9,
+    Munmap = 11,
+    Open = 2,
+    Close = 3,
+    Read = 0,
+    Write = 1,
+    Seek = 8,
+    Fstat = 4,
+    Fsync = 74,
+    GetCwd = 79,
+    GetDirEntry = 78,
+    Dup2 = 33,
+    SetPriority = 141,
 }