panicless default fs implement

kernel/src/fs.rs

@@ -108,16 +108,16 @@ lazy_static! {
 // TODO: better way to provide default impl?
 macro_rules! impl_inode {
     () => {
-        fn info(&self) -> Result<FileInfo> { unimplemented!() }
-        fn sync(&self) -> Result<()> { unimplemented!() }
-        fn resize(&self, _len: usize) -> Result<()> { unimplemented!() }
-        fn create(&self, _name: &str, _type_: FileType) -> Result<Arc<INode>> { unimplemented!() }
-        fn unlink(&self, _name: &str) -> Result<()> { unimplemented!() }
-        fn link(&self, _name: &str, _other: &Arc<INode>) -> Result<()> { unimplemented!() }
-        fn rename(&self, _old_name: &str, _new_name: &str) -> Result<()> { unimplemented!() }
-        fn move_(&self, _old_name: &str, _target: &Arc<INode>, _new_name: &str) -> Result<()> { unimplemented!() }
-        fn find(&self, _name: &str) -> Result<Arc<INode>> { unimplemented!() }
-        fn get_entry(&self, _id: usize) -> Result<String> { unimplemented!() }
+        fn info(&self) -> Result<FileInfo> { Err(FsError::NotSupported) }
+        fn sync(&self) -> Result<()> { Ok(()) }
+        fn resize(&self, _len: usize) -> Result<()> { Err(FsError::NotSupported) }
+        fn create(&self, _name: &str, _type_: FileType) -> Result<Arc<INode>> { Err(FsError::NotDir) }
+        fn unlink(&self, _name: &str) -> Result<()> { Err(FsError::NotDir) }
+        fn link(&self, _name: &str, _other: &Arc<INode>) -> Result<()> { Err(FsError::NotDir) }
+        fn rename(&self, _old_name: &str, _new_name: &str) -> Result<()> { Err(FsError::NotDir) }
+        fn move_(&self, _old_name: &str, _target: &Arc<INode>, _new_name: &str) -> Result<()> { Err(FsError::NotDir) }
+        fn find(&self, _name: &str) -> Result<Arc<INode>> { Err(FsError::NotDir) }
+        fn get_entry(&self, _id: usize) -> Result<String> { Err(FsError::NotDir) }
         fn fs(&self) -> Arc<FileSystem> { unimplemented!() }
         fn as_any_ref(&self) -> &Any { self }
     };

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),
     }
 }
 
@@ -286,7 +286,8 @@ pub type SysResult = Result<i32, SysError>;
 #[repr(i32)]
 #[derive(Debug)]
 pub enum SysError {
-    // ucore compatible error code, which is a modified version of the ones used in linux
+    // 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
     // name conversion E_XXXXX -> SysError::Xxxxx
     // see https://github.com/oscourse-tsinghua/ucore_plus/blob/master/ucore/src/libs-user-ucore/common/error.h
     // we only add current used errors here