diff --git a/lib.rs b/lib.rs
index bda4da9..0c52084 100644
--- a/lib.rs
+++ b/lib.rs
@@ -93,9 +93,9 @@ pub fn cpu_count() -> usize {
 pub extern fn userspace_init() {
     assert_eq!(syscall::chdir(b"initfs:bin"), Ok(0));
 
-    assert_eq!(syscall::open(b"debug:", 0).map(FileHandle::into), Ok(0));
-    assert_eq!(syscall::open(b"debug:", 0).map(FileHandle::into), Ok(1));
-    assert_eq!(syscall::open(b"debug:", 0).map(FileHandle::into), Ok(2));
+    assert_eq!(syscall::open(b"debug:", syscall::flag::O_RDONLY).map(FileHandle::into), Ok(0));
+    assert_eq!(syscall::open(b"debug:", syscall::flag::O_WRONLY).map(FileHandle::into), Ok(1));
+    assert_eq!(syscall::open(b"debug:", syscall::flag::O_WRONLY).map(FileHandle::into), Ok(2));
 
     syscall::exec(b"initfs:bin/init", &[]).expect("failed to execute initfs:init");
 
diff --git a/scheme/user.rs b/scheme/user.rs
index b7355bb..589a8c9 100644
--- a/scheme/user.rs
+++ b/scheme/user.rs
@@ -224,14 +224,6 @@ impl Scheme for UserScheme {
         result
     }
 
-    fn mkdir(&self, path: &[u8], mode: u16, _uid: u32, _gid: u32) -> Result<usize> {
-        let inner = self.inner.upgrade().ok_or(Error::new(ENODEV))?;
-        let address = inner.capture(path)?;
-        let result = inner.call(SYS_MKDIR, address, path.len(), mode as usize);
-        let _ = inner.release(address);
-        result
-    }
-
     fn chmod(&self, path: &[u8], mode: u16, _uid: u32, _gid: u32) -> Result<usize> {
         let inner = self.inner.upgrade().ok_or(Error::new(ENODEV))?;
         let address = inner.capture(path)?;
diff --git a/syscall/fs.rs b/syscall/fs.rs
index 30bd291..6f6a698 100644
--- a/syscall/fs.rs
+++ b/syscall/fs.rs
@@ -49,7 +49,7 @@ pub fn file_op_mut_slice(a: usize, fd: FileHandle, slice: &mut [u8]) -> Result<u
 
 /// Change the current working directory
 pub fn chdir(path: &[u8]) -> Result<usize> {
-    let fd = open(path, 0)?;
+    let fd = open(path, syscall::flag::O_RDONLY | syscall::flag::O_DIRECTORY)?;
     let mut stat = Stat::default();
     let stat_res = file_op_mut_slice(syscall::number::SYS_FSTAT, fd, &mut stat);
     let _ = close(fd);
@@ -144,28 +144,6 @@ pub fn pipe2(fds: &mut [usize], flags: usize) -> Result<usize> {
     }
 }
 
-/// mkdir syscall
-pub fn mkdir(path: &[u8], mode: u16) -> Result<usize> {
-    let (path_canon, uid, gid, scheme_ns) = {
-        let contexts = context::contexts();
-        let context_lock = contexts.current().ok_or(Error::new(ESRCH))?;
-        let context = context_lock.read();
-        (context.canonicalize(path), context.euid, context.egid, context.ens)
-    };
-
-    let mut parts = path_canon.splitn(2, |&b| b == b':');
-    let scheme_name_opt = parts.next();
-    let reference_opt = parts.next();
-
-    let scheme_name = scheme_name_opt.ok_or(Error::new(ENODEV))?;
-    let scheme = {
-        let schemes = scheme::schemes();
-        let (_scheme_id, scheme) = schemes.get_name(scheme_ns, scheme_name).ok_or(Error::new(ENODEV))?;
-        scheme.clone()
-    };
-    scheme.mkdir(reference_opt.unwrap_or(b""), mode, uid, gid)
-}
-
 /// chmod syscall
 pub fn chmod(path: &[u8], mode: u16) -> Result<usize> {
     let (path_canon, uid, gid, scheme_ns) = {
diff --git a/syscall/mod.rs b/syscall/mod.rs
index f197f84..69e53ec 100644
--- a/syscall/mod.rs
+++ b/syscall/mod.rs
@@ -61,7 +61,6 @@ pub extern fn syscall(a: usize, b: usize, c: usize, d: usize, e: usize, f: usize
             },
             SYS_CLASS_PATH => match a {
                 SYS_OPEN => open(validate_slice(b as *const u8, c)?, d).map(FileHandle::into),
-                SYS_MKDIR => mkdir(validate_slice(b as *const u8, c)?, d as u16),
                 SYS_CHMOD => chmod(validate_slice(b as *const u8, c)?, d as u16),
                 SYS_RMDIR => rmdir(validate_slice(b as *const u8, c)?),
                 SYS_UNLINK => unlink(validate_slice(b as *const u8, c)?),
diff --git a/syscall/process.rs b/syscall/process.rs
index 9c1c69a..f6b4b1e 100644
--- a/syscall/process.rs
+++ b/syscall/process.rs
@@ -468,7 +468,7 @@ pub fn exec(path: &[u8], arg_ptrs: &[[usize; 2]]) -> Result<usize> {
             (context.euid, context.egid, context.canonicalize(path))
         };
 
-        let file = syscall::open(&canonical, 0)?;
+        let file = syscall::open(&canonical, syscall::flag::O_RDONLY)?;
         let mut stat = Stat::default();
         syscall::file_op_mut_slice(syscall::number::SYS_FSTAT, file, &mut stat)?;