wasmldr: exit with a useful exit code

Currently, when wasmldr exits due to ExportNotFound, it returns an exit
code of... 101. Why 101? Great question! I have absolutely no idea.

In order to make things a bit more sensible, I've defined different exit
codes for different errors. They roughly match FreeBSD's "preferable"
exit codes, as defined in `sysexits.h` - see [sysexits(3)] for more
info.

[sysexits(3)]: https://www.freebsd.org/cgi/man.cgi?sektion=3&query=sysexits

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

Author: wgwoods

internal/wasmldr/src/main.rs

@@ -66,8 +66,29 @@ fn main() {
 
     info!("running workload");
     // TODO: pass opts.wasm_features
-    let result = workload::run(bytes, opts.args, opts.envs).expect("Failed to run workload");
+    let result = workload::run(bytes, opts.args, opts.envs);
     info!("got result: {:#?}", result);
-    // TODO: exit with the resulting code, if the result is a return code
+
     // FUTURE: produce attestation report here
+    // TODO: print the returned value(s) in some format (json?)
+
+    // Choose an appropriate exit code
+    // TODO: exit with the resulting code, if the result is a return code
+    std::process::exit(match result {
+        // Success -> EX_OK
+        Ok(_) => 0,
+
+        // wasmtime/WASI/module setup errors -> EX_DATAERR
+        Err(workload::Error::ConfigurationError) => 65,
+        Err(workload::Error::StringTableError) => 65,
+        Err(workload::Error::InstantiationFailed) => 65,
+        Err(workload::Error::ExportNotFound) => 65,
+        Err(workload::Error::CallFailed) => 65,
+
+        // Internal WASI errors -> EX_SOFTWARE
+        Err(workload::Error::WASIError(_)) => 70,
+
+        // General IO errors -> EX_IOERR
+        Err(workload::Error::IoError(_)) => 74,
+    });
 }