Add `dup` syscall

kernel/src/syscall/fs.rs

@@ -520,6 +520,14 @@ impl Syscall<'_> {
         Ok(fd2)
     }
 
+    pub fn sys_dup(&mut self, fd1: usize) -> SysResult {
+        let mut proc = self.process();
+        let file_like = proc.get_file_like(fd1)?.clone();
+        let fd2 = proc.add_file(file_like);
+        info!("dup: from {} to {}", fd1, fd2);
+        Ok(fd2)
+    }
+
     pub fn sys_ioctl(
         &mut self,
         fd: usize,

kernel/src/syscall/mod.rs

@@ -137,6 +137,7 @@ impl Syscall<'_> {
             SYS_FCHOWN => self.unimplemented("fchown", Ok(0)),
             SYS_FCHOWNAT => self.unimplemented("fchownat", Ok(0)),
             SYS_FACCESSAT => self.sys_faccessat(args[0], args[1] as *const u8, args[2], args[3]),
+            SYS_DUP => self.sys_dup(args[0]),
             SYS_DUP3 => self.sys_dup2(args[0], args[1]), // TODO: handle `flags`
             SYS_PIPE2 => self.sys_pipe(args[0] as *mut u32), // TODO: handle `flags`
             SYS_UTIMENSAT => self.unimplemented("utimensat", Ok(0)),