configurable trans-membrance hostcall blocklist

src/wasm/backend.cpp

@@ -53,6 +53,17 @@ static String wasm_backend_ensure_started(Request* context)
 	wc.memory_limit = (int64_t)to_u64(cfg["WASM_MEMORY_LIMIT_BYTES"], 512ull * 1024 * 1024);
 	wc.epoch_deadline_ticks = to_u64(cfg["WASM_EPOCH_DEADLINE_TICKS"], 200);
 	wc.verbose = to_bool(cfg["WASM_BACKEND_VERBOSE"], false);
+	// UCE_HOSTCALL_BLOCKLIST: comma-separated uce_host_* names (with or without
+	// the "uce_host_" prefix) the sysadmin disables; each blocked call traps into
+	// the error page (see make_host_import). Parsed once here, per worker process.
+	for(String entry : split(cfg["UCE_HOSTCALL_BLOCKLIST"], ","))
+	{
+		entry = trim(entry);
+		if(entry.rfind("uce_host_", 0) == 0)
+			entry = entry.substr(9);
+		if(entry != "")
+			wc.hostcall_blocklist.insert(entry);
+	}
 
 	g_wasm_worker = new WasmWorker(wc);
 	g_wasm_init_error = g_wasm_worker->init();
@@ -131,6 +142,12 @@ String wasm_backend_serve(Request& request, const String& entry_unit, const Stri
 	// Raw request body: cli_input() parses a JSON CLI payload from context.in,
 	// and serve_http handlers read it as req->in; carried into the workspace.
 	ctx["in"] = request.in;
+	// Configurable error pages read context.call["error"] (the error_info DValue
+	// set natively in render_wasm_error_page). apply_context binds context.call to
+	// the decoded ctx, so marshal the native request.call children across the
+	// membrane — otherwise the error page renders with no error data.
+	for(auto& entry : request.call._map)
+		ctx[entry.first] = entry.second;
 	// WebSocket event context: the workspace owns no connections, so the frame's
 	// connection identity goes in and the handler's ws_send/ws_close dispatch
 	// commands come back out (below) for the native broker to apply.