Add Workldr trait, use it to load internal wasmldr

In parallel with the Backend trait, this commit adds a Workldr trait for
handling `wasmldr` (and any future workldr implementations.)

We've also got a naive function for picking the "best" workldr (there's
only one, so that's easy) and using that for `exec` if nothing was
passed on the CLI.

Signed-off-by: Will Woods <[email protected]>

src/main.rs

@@ -58,8 +58,10 @@
 
 mod backend;
 mod protobuf;
+mod workldr;
 
 use backend::{Backend, Command};
+use workldr::Workldr;
 
 use std::convert::TryInto;
 use std::path::PathBuf;
@@ -78,7 +80,7 @@ struct Info {}
 #[derive(StructOpt)]
 struct Exec {
     /// The payload to run inside the keep
-    code: PathBuf,
+    code: Option<PathBuf>,
 }
 
 #[derive(StructOpt)]
@@ -95,9 +97,24 @@ fn main() -> Result<()> {
         Box::new(backend::sgx::Backend),
     ];
 
+    let workldrs: &[Box<dyn Workldr>] = &[
+        #[cfg(feature = "wasmldr")]
+        Box::new(workldr::wasmldr::Wasmldr),
+    ];
+
     match Options::from_args() {
         Options::Info(_) => info(backends),
-        Options::Exec(e) => exec(backends, e),
+        Options::Exec(e) => {
+            // FUTURE: accept tenant-provided shim, or fall back to builtin..
+            let backend = backend(backends);
+            let shim_bytes = backend.shim();
+            if let Some(path) = e.code {
+                let map = mmarinus::Kind::Private.load::<mmarinus::perms::Read, _>(&path)?;
+                exec(backend, shim_bytes, map)
+            } else {
+                exec(backend, shim_bytes, workldr(workldrs).exec())
+            }
+        }
     }
 }
 
@@ -149,12 +166,16 @@ fn backend(backends: &[Box<dyn Backend>]) -> &dyn Backend {
     }
 }
 
-fn exec(backends: &[Box<dyn Backend>], opts: Exec) -> Result<()> {
-    let backend = backend(backends);
+#[inline]
+fn workldr(workldrs: &[Box<dyn Workldr>]) -> &dyn Workldr {
+    // NOTE: this is stupid, but we only have one workldr, so... ¯\_(ツ)_/¯
+    &*workldrs[0]
+}
 
-    let map = mmarinus::Kind::Private.load::<mmarinus::perms::Read, _>(&opts.code)?;
+fn exec(backend: &dyn Backend, shim: impl AsRef<[u8]>, exec: impl AsRef<[u8]>) -> Result<()> {
+    //let map = mmarinus::Kind::Private.load::<mmarinus::perms::Read, _>(&opts.code)?;
 
-    let keep = backend.keep(backend.shim(), &map)?;
+    let keep = backend.keep(shim.as_ref(), exec.as_ref())?;
     let mut thread = keep.clone().spawn()?.unwrap();
     loop {
         match thread.enter()? {

src/workldr/mod.rs

@@ -0,0 +1,39 @@
+// SPDX-License-Identifier: Apache-2.0
+
+// FUTURE: right now we only have one Workldr, `wasmldr`.
+// In the future there may be other workload types - in theory we can run
+// any static PIE ELF binary. We could have a Lua interpreter, or a
+// JavaScript interpreter, or whatever.
+// So there's two parts to this trait - call them KeepSetup and Engine.
+//
+// KeepSetup is the part that actually sets up the Keep for the Workload,
+// which might involve setting up network sockets, storage devices, etc.
+// This part must be implemented by any Workldr, since we want the
+// Enarx environment to be platform-agnostic.
+//
+// Engine is the (workload-specific) portion that actually interprets or
+// executes the workload. It's responsible for taking the sockets / devices
+// etc. that were set up by KeepSetup and making them usable in a way that
+// the workload will understand.
+//
+// So: someday we might want to split this into two traits, and we might
+// have multiple Workldrs for different languages/environments, and we
+// might need to examine the workload and determine which Workldr is
+// the right one to use. But first... we gotta make wasmldr work.
+
+#[cfg(feature = "wasmldr")]
+pub mod wasmldr;
+
+/// A trait for the "Workloader" - shortened to Workldr, also known as "exec"
+/// (as in Backend::keep(shim, exec) [q.v.]) and formerly known as the "code"
+/// layer. This is the part that runs inside the keep, prepares the workload
+/// environment, and then actually executes the tenant's workload.
+///
+/// Basically, this is a generic view of wasmldr.
+pub trait Workldr {
+    /// The name of the Workldr
+    fn name(&self) -> &'static str;
+
+    /// The builtin Workldr binary (e.g. wasmldr)
+    fn exec(&self) -> &'static [u8];
+}

src/workldr/wasmldr/mod.rs

@@ -0,0 +1,15 @@
+// SPDX-License-Identifier: Apache-2.0
+
+pub struct Wasmldr;
+
+impl crate::workldr::Workldr for Wasmldr {
+    #[inline]
+    fn name(&self) -> &'static str {
+        "wasmldr"
+    }
+
+    #[inline]
+    fn exec(&self) -> &'static [u8] {
+        include_bytes!(concat!(env!("OUT_DIR"), "/bin/wasmldr"))
+    }
+}