Add ability to contain a process in a scheme sandbox

kernel/scheme/sys/scheme.rs

@@ -1,13 +1,21 @@
 use collections::Vec;
 
+use context;
 use scheme;
-use syscall::error::Result;
+use syscall::error::{Error, ESRCH, Result};
 
 pub fn resource() -> Result<Vec<u8>> {
+    let scheme_ns = {
+        let contexts = context::contexts();
+        let context_lock = contexts.current().ok_or(Error::new(ESRCH))?;
+        let context = context_lock.read();
+        context.scheme_ns
+    };
+
     let mut data = Vec::new();
 
     let schemes = scheme::schemes();
-    for (name, _scheme_lock) in schemes.iter_name() {
+    for (name, _scheme_lock) in schemes.iter_name(scheme_ns) {
         data.extend_from_slice(name);
         data.push(b'\n');
     }