chromium/extensions/browser/process_map.h

// Copyright 2013 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef EXTENSIONS_BROWSER_PROCESS_MAP_H_
#define EXTENSIONS_BROWSER_PROCESS_MAP_H_

#include <stddef.h>

#include <optional>

#include "base/containers/flat_map.h"
#include "components/keyed_service/core/keyed_service.h"
#include "content/public/browser/site_instance.h"
#include "extensions/common/extension_id.h"
#include "extensions/common/features/feature.h"
#include "extensions/common/mojom/context_type.mojom-forward.h"

namespace content {
class BrowserContext;
}  // namespace content

namespace extensions {
class Extension;

// Contains information about which extensions are assigned to which processes.
//
// The relationship between extensions and processes is complex:
//
// - Extensions can be either "split" mode or "spanning" mode.
// - In spanning mode, extensions *generally* share a single process between all
//   incognito and normal windows. This was the original mode for extensions.
// - In split mode, extensions have separate processes in incognito windows.
// - There are also hosted apps, which are a kind of extensions, and those
//   usually have a process model similar to normal web sites: multiple
//   processes per-profile.
// - An extension can also opt into Cross Origin Isolation in which case it can
//   have multiple processes per profile since cross-origin-isolated and
//   non-cross-origin-isolated contexts don't share a process.
//
// Under the current model, a single extension can correspond to multiple
// processes (see explanation below), but a single process cannot be shared by
// multiple extensions.
//
// Note that because of content scripts, frames, and other edge cases in
// Chrome's process isolation, extension code can still end up running outside
// an assigned process.
//
// But we only allow high-privilege operations to be performed by an extension
// when it is running in an assigned process.
//
// ===========================================================================
// WARNINGS - PLEASE UNDERSTAND THESE BEFORE CALLING OR MODIFYING THIS CLASS
// ===========================================================================
//
// 1. This class contains the processes for hosted apps as well as extensions
//    and packaged apps. Just because a process is present here *does not* mean
//    it is an "extension process" (e.g., for UI purposes). It may contain only
//    hosted apps. See crbug.com/102533.
//
// 2. An extension can show up in multiple processes. That is why there is no
//    GetExtensionProcess() method here. There are multiple such cases:
//      a) The extension is actually a hosted app.
//      b) There is an incognito window open and the extension is "split mode".
//      c) The extension is cross origin isolated but has
//         non-cross-origin-isolated contexts.
//    It is *not safe* to assume that there is one process per extension.
//
// 3. The process ids contained in this class are *not limited* to the Profile
//    you got this map from. They can also be associated with that profile's
//    incognito/normal twin. If you care about this, use
//    RenderProcessHost::FromID() and check the profile of the resulting object.
//
// TODO(aa): The above warnings suggest this class could use improvement :).
//
// TODO(kalman): This class is not threadsafe, but is used on both the UI and IO
//               threads. Somebody should fix that, either make it threadsafe or
//               enforce single thread. Investigation required.
class ProcessMap : public KeyedService { … };

}  // namespace extensions

#endif  // EXTENSIONS_BROWSER_PROCESS_MAP_H_