Add mode to open operation

src/main.rs

@@ -3,7 +3,7 @@ mod ext2;
 use std::{
     borrow::Cow,
     fs::File,
-    os::mikros::{ipc, syscalls, Errno},
+    os::mikros::{ipc, syscalls, Errno, FileOpenMode},
     sync::Arc, usize,
 };
 
@@ -34,7 +34,11 @@ impl fs_rpc::Server for Serv {
         res
     }
 
-    fn open(&self, path: &std::path::Path, mount_id: u64) -> Result<(Option<u64>, u64), Errno> {
+    fn open(&self, path: &std::path::Path, mode: FileOpenMode, mount_id: u64) -> Result<(Option<u64>, u64), Errno> {
+        if !mode.readable() || mode.writable() {
+            // WRiting isn't supported yet, so the only sensible mode is readonly.
+            return Err(Errno::EACCES);
+        }
         let mounts = self.mounts.read();
         let mount = &mounts[mount_id as usize];
         let file = mount.open(path)?;