src: move internal loaders out of bootstrap_node.js

- Moves the creation of `process.binding()`, `process._linkedBinding()`
  `internalBinding()` and `NativeModule` into a separate file
  `lib/internal/bootstrap_loaders.js`, and documents them there.
  This file will be compiled and run before `bootstrap_node.js`, which
  means we now bootstrap the internal module & binding system before
  actually bootstrapping Node.js.
- Rename the special ID that can be used to require `NativeModule`
  as `internal/bootstrap_loaders` since it is setup there. Also put
  `internalBinding` in the object exported by `NativeModule.require`
  instead of putting it inside the `NativeModule.wrapper`
- Use the original `getBinding()` to get the source code of native
  modules instead of getting it from `process.binding('native')`
  so that users cannot fake native modules by modifying the binding
  object.
- Names the bootstrapping functions so their names show up
  in the stack trace.

Backport-PR-URL: #19374
PR-URL: #19112
Reviewed-By: Anna Henningsen <[email protected]>
Reviewed-By: Anatoli Papirovski <[email protected]>
Reviewed-By: James M Snell <[email protected]>
Reviewed-By: Gus Caplan <[email protected]>

.eslintrc.yaml

@@ -214,4 +214,3 @@ globals:
   LTTNG_HTTP_SERVER_RESPONSE: false
   LTTNG_NET_SERVER_CONNECTION: false
   LTTNG_NET_STREAM_END: false
-  internalBinding: false

lib/domain.js

@@ -30,6 +30,7 @@ const util = require('util');
 const EventEmitter = require('events');
 const errors = require('internal/errors');
 const { createHook } = require('async_hooks');
+const { internalBinding } = require('internal/bootstrap_loaders');
 
 // overwrite process.domain with a getter/setter that will allow for more
 // effective optimizations

lib/internal/bootstrap_loaders.js

@@ -0,0 +1,216 @@
+// This file creates the internal module & binding loaders used by built-in
+// modules. In contrast, user land modules are loaded using
+// lib/module.js (CommonJS Modules) or lib/internal/loader/* (ES Modules).
+//
+// This file is compiled and run by node.cc before bootstrap_node.js
+// was called, therefore the loaders are bootstraped before we start to
+// actually bootstrap Node.js. It creates the following objects:
+//
+// C++ binding loaders:
+// - process.binding(): the legacy C++ binding loader, accessible from user land
+//   because it is an object attached to the global process object.
+//   These C++ bindings are created using NODE_BUILTIN_MODULE_CONTEXT_AWARE()
+//   and have their nm_flags set to NM_F_BUILTIN. We do not make any guarantees
+//   about the stability of these bindings, but still have to take care of
+//   compatibility issues caused by them from time to time.
+// - process._linkedBinding(): intended to be used by embedders to add
+//   additional C++ bindings in their applications. These C++ bindings
+//   can be created using NODE_MODULE_CONTEXT_AWARE_CPP() with the flag
+//   NM_F_LINKED.
+// - internalBinding(): the private internal C++ binding loader, inaccessible
+//   from user land because they are only available from NativeModule.require()
+//   These C++ bindings are created using NODE_MODULE_CONTEXT_AWARE_INTERNAL()
+//   and have their nm_flags set to NM_F_INTERNAL.
+//
+// Internal JavaScript module loader:
+// - NativeModule: a minimal module system used to load the JavaScript core
+//   modules found in lib/**/*.js and deps/**/*.js. All core modules are
+//   compiled into the node binary via node_javascript.cc generated by js2c.py,
+//   so they can be loaded faster without the cost of I/O. This class makes the
+//   lib/internal/*, deps/internal/* modules and internalBinding() available by
+//   default to core modules, and lets the core modules require itself via
+//   require('internal/bootstrap_loaders') even when this file is not written in
+//   CommonJS style.
+//
+// Other objects:
+// - process.moduleLoadList: an array recording the bindings and the modules
+//   loaded in the process and the order in which they are loaded.
+
+'use strict';
+
+(function bootstrapInternalLoaders(process, getBinding, getLinkedBinding,
+                                   getInternalBinding) {
+
+  // Set up process.moduleLoadList
+  const moduleLoadList = [];
+  Object.defineProperty(process, 'moduleLoadList', {
+    value: moduleLoadList,
+    configurable: true,
+    enumerable: true,
+    writable: false
+  });
+
+  // Set up process.binding() and process._linkedBinding()
+  {
+    const bindingObj = Object.create(null);
+
+    process.binding = function binding(module) {
+      module = String(module);
+      let mod = bindingObj[module];
+      if (typeof mod !== 'object') {
+        mod = bindingObj[module] = getBinding(module);
+        moduleLoadList.push(`Binding ${module}`);
+      }
+      return mod;
+    };
+
+    process._linkedBinding = function _linkedBinding(module) {
+      module = String(module);
+      let mod = bindingObj[module];
+      if (typeof mod !== 'object')
+        mod = bindingObj[module] = getLinkedBinding(module);
+      return mod;
+    };
+  }
+
+  // Set up internalBinding() in the closure
+  let internalBinding;
+  {
+    const bindingObj = Object.create(null);
+    internalBinding = function internalBinding(module) {
+      let mod = bindingObj[module];
+      if (typeof mod !== 'object') {
+        mod = bindingObj[module] = getInternalBinding(module);
+        moduleLoadList.push(`Internal Binding ${module}`);
+      }
+      return mod;
+    };
+  }
+
+  // Minimal sandbox helper
+  const ContextifyScript = process.binding('contextify').ContextifyScript;
+  function runInThisContext(code, options) {
+    const script = new ContextifyScript(code, options);
+    return script.runInThisContext();
+  }
+
+  // Set up NativeModule
+  function NativeModule(id) {
+    this.filename = `${id}.js`;
+    this.id = id;
+    this.exports = {};
+    this.loaded = false;
+    this.loading = false;
+  }
+
+  NativeModule._source = getBinding('natives');
+  NativeModule._cache = {};
+
+  const config = getBinding('config');
+
+  // Think of this as module.exports in this file even though it is not
+  // written in CommonJS style.
+  const loaderExports = { internalBinding, NativeModule };
+  const loaderId = 'internal/bootstrap_loaders';
+  NativeModule.require = function(id) {
+    if (id === loaderId) {
+      return loaderExports;
+    }
+
+    const cached = NativeModule.getCached(id);
+    if (cached && (cached.loaded || cached.loading)) {
+      return cached.exports;
+    }
+
+    if (!NativeModule.exists(id)) {
+      // Model the error off the internal/errors.js model, but
+      // do not use that module given that it could actually be
+      // the one causing the error if there's a bug in Node.js
+      const err = new Error(`No such built-in module: ${id}`);
+      err.code = 'ERR_UNKNOWN_BUILTIN_MODULE';
+      err.name = 'Error [ERR_UNKNOWN_BUILTIN_MODULE]';
+      throw err;
+    }
+
+    moduleLoadList.push(`NativeModule ${id}`);
+
+    const nativeModule = new NativeModule(id);
+
+    nativeModule.cache();
+    nativeModule.compile();
+
+    return nativeModule.exports;
+  };
+
+  NativeModule.getCached = function(id) {
+    return NativeModule._cache[id];
+  };
+
+  NativeModule.exists = function(id) {
+    return NativeModule._source.hasOwnProperty(id);
+  };
+
+  if (config.exposeInternals) {
+    NativeModule.nonInternalExists = function(id) {
+      // Do not expose this to user land even with --expose-internals
+      if (id === loaderId) {
+        return false;
+      }
+      return NativeModule.exists(id);
+    };
+
+    NativeModule.isInternal = function(id) {
+      // Do not expose this to user land even with --expose-internals
+      return id === loaderId;
+    };
+  } else {
+    NativeModule.nonInternalExists = function(id) {
+      return NativeModule.exists(id) && !NativeModule.isInternal(id);
+    };
+
+    NativeModule.isInternal = function(id) {
+      return id.startsWith('internal/');
+    };
+  }
+
+  NativeModule.getSource = function(id) {
+    return NativeModule._source[id];
+  };
+
+  NativeModule.wrap = function(script) {
+    return NativeModule.wrapper[0] + script + NativeModule.wrapper[1];
+  };
+
+  NativeModule.wrapper = [
+    '(function (exports, require, module, process) {',
+    '\n});'
+  ];
+
+  NativeModule.prototype.compile = function() {
+    let source = NativeModule.getSource(this.id);
+    source = NativeModule.wrap(source);
+
+    this.loading = true;
+
+    try {
+      const fn = runInThisContext(source, {
+        filename: this.filename,
+        lineOffset: 0,
+        displayErrors: true
+      });
+      fn(this.exports, NativeModule.require, this, process);
+
+      this.loaded = true;
+    } finally {
+      this.loading = false;
+    }
+  };
+
+  NativeModule.prototype.cache = function() {
+    NativeModule._cache[this.id] = this;
+  };
+
+  // This will be passed to the bootstrapNodeJSCore function in
+  // bootstrap_node.js.
+  return loaderExports;
+});