Add sys:exe to get current executable

kernel/scheme/sys/exe.rs

@@ -0,0 +1,16 @@
+use collections::Vec;
+
+use context;
+use syscall::error::{Error, ESRCH, Result};
+
+pub fn resource() -> Result<Vec<u8>> {
+    let mut name = {
+        let contexts = context::contexts();
+        let context_lock = contexts.current().ok_or(Error::new(ESRCH))?;
+        let context = context_lock.read();
+        let name = context.name.lock();
+        name.clone()
+    };
+    name.push(b'\n');
+    Ok(name)
+}