Remove the shim kernel crate

kernel/src/device/zero.rs

@@ -0,0 +1,39 @@
+// SPDX-License-Identifier: MPL-2.0
+
+#![allow(unused_variables)]
+
+use super::*;
+use crate::{events::IoEvents, fs::inode_handle::FileIo, prelude::*, process::signal::Poller};
+
+pub struct Zero;
+
+impl Device for Zero {
+    fn type_(&self) -> DeviceType {
+        DeviceType::CharDevice
+    }
+
+    fn id(&self) -> DeviceId {
+        // Same value with Linux
+        DeviceId::new(1, 5)
+    }
+}
+
+impl FileIo for Zero {
+    fn read(&self, writer: &mut VmWriter) -> Result<usize> {
+        // TODO: Use more efficient way when need to read a bunch of zeros once.
+        let read_len = writer.avail();
+        for _ in 0..read_len {
+            writer.write_val(&0u8)?;
+        }
+        Ok(read_len)
+    }
+
+    fn write(&self, reader: &mut VmReader) -> Result<usize> {
+        Ok(reader.remain())
+    }
+
+    fn poll(&self, mask: IoEvents, poller: Option<&mut Poller>) -> IoEvents {
+        let events = IoEvents::IN | IoEvents::OUT;
+        events & mask
+    }
+}