Add syscall module

kernel/syscall/fs.rs

@@ -0,0 +1,27 @@
+//! Filesystem syscalls
+
+use super::Result;
+
+/// Read syscall
+pub fn read(fd: usize, buf: &mut [u8]) -> Result<usize> {
+    println!("Read {}: {}", fd, buf.len());
+    Ok(0)
+}
+
+/// Write syscall
+pub fn write(fd: usize, buf: &[u8]) -> Result<usize> {
+    println!("Write {}: {}", fd, buf.len());
+    Ok(0)
+}
+
+/// Open syscall
+pub fn open(path: &[u8], flags: usize) -> Result<usize> {
+    println!("Open {:?}: {:X}", ::core::str::from_utf8(path), flags);
+    Ok(0)
+}
+
+/// Close syscall
+pub fn close(fd: usize) -> Result<usize> {
+    println!("Close {}", fd);
+    Ok(0)
+}