Bug 1908725 - Part 3: Use GeckoChildID as the value for ContentParentId, r=smaug,ipc-reviewers,mccr8

The type for ContentParentId is uint64_t, however only at most 22 bits
are allowed to be used (as it is used in the high bits of nsContentUtils
process-specific IDs, which need to fit within a JS double). Switching to use
the same existing ChildID reduces the risk of confusion, but this patch doesn't
attempt to update the types used for ContentParentId/ChildID to match
GeckoChildID.

In the future, we probably will want to align these types more closely, and
perhaps de-duplicate some code which currently passes around both.

Differential Revision: https://phabricator.services.mozilla.com/D217119

dom/ipc/ContentChild.cpp

@@ -603,10 +603,7 @@ ContentChild* ContentChild::sSingleton;
 StaticAutoPtr<ContentChild::ShutdownCanary> ContentChild::sShutdownCanary;
 
 ContentChild::ContentChild()
-    : mID(uint64_t(-1)),
-      mIsForBrowser(false),
-      mIsAlive(true),
-      mShuttingDown(false) {
+    : mIsForBrowser(false), mIsAlive(true), mShuttingDown(false) {
   // This process is a content process, so it's clearly running in
   // multiprocess mode!
   nsDebugImpl::SetMultiprocessMode("Child");
@@ -705,8 +702,7 @@ class nsGtkNativeInitRunnable : public Runnable {
 };
 
 void ContentChild::Init(mozilla::ipc::UntypedEndpoint&& aEndpoint,
-                        const char* aParentBuildID, uint64_t aChildID,
-                        bool aIsForBrowser) {
+                        const char* aParentBuildID, bool aIsForBrowser) {
 #ifdef MOZ_WIDGET_GTK
   // When running X11 only build we need to pass a display down
   // to gtk_init because it's not going to use the one from the environment
@@ -795,7 +791,6 @@ void ContentChild::Init(mozilla::ipc::UntypedEndpoint&& aEndpoint,
 
   CrashReporterClient::InitSingleton(this);
 
-  mID = aChildID;
   mIsForBrowser = aIsForBrowser;
 
   SetProcessName("Web Content"_ns);
@@ -4572,7 +4567,7 @@ mozilla::ipc::IPCResult ContentChild::RecvInitSandboxTesting(
 #endif
 
 NS_IMETHODIMP ContentChild::GetChildID(uint64_t* aOut) {
-  *aOut = mID;
+  *aOut = XRE_GetChildID();
   return NS_OK;
 }
 

dom/ipc/ContentChild.h

@@ -114,7 +114,7 @@ class ContentChild final : public PContentChild,
       BrowsingContext** aReturn);
 
   void Init(mozilla::ipc::UntypedEndpoint&& aEndpoint,
-            const char* aParentBuildID, uint64_t aChildID, bool aIsForBrowser);
+            const char* aParentBuildID, bool aIsForBrowser);
 
   void InitXPCOM(XPCOMInitData&& aXPCOMInit,
                  const mozilla::dom::ipc::StructuredCloneData& aInitialData,
@@ -446,7 +446,9 @@ class ContentChild final : public PContentChild,
   // cache the value
   nsString& GetIndexedDBPath();
 
-  ContentParentId GetID() const { return mID; }
+  ContentParentId GetID() const {
+    return ContentParentId{static_cast<uint64_t>(XRE_GetChildID())};
+  }
 
   bool IsForBrowser() const { return mIsForBrowser; }
 
@@ -827,15 +829,6 @@ class ContentChild final : public PContentChild,
   // Temporary storage for list of shared-fontlist memory blocks.
   nsTArray<base::SharedMemoryHandle> mSharedFontListBlocks;
 
-  /**
-   * An ID unique to the process containing our corresponding
-   * content parent.
-   *
-   * We expect our content parent to set this ID immediately after opening a
-   * channel to us.
-   */
-  ContentParentId mID;
-
   AppInfo mAppInfo;
 
   bool mIsForBrowser;

dom/ipc/ContentParent.cpp

@@ -553,9 +553,6 @@ static bool sCreatedFirstContentProcess = false;
 static bool sInProcessSelector = false;
 #endif
 
-// The first content child has ID 1, so the chrome process can have ID 0.
-static uint64_t gContentChildID = 1;
-
 static const char* sObserverTopics[] = {
     NS_IPC_IOSERVICE_SET_OFFLINE_TOPIC,
     NS_IPC_IOSERVICE_SET_CONNECTIVITY_TOPIC,
@@ -2368,7 +2365,6 @@ bool ContentParent::BeginSubprocessLaunch(ProcessPriority aPriority) {
   }
 
   std::vector<std::string> extraArgs;
-  geckoargs::sChildID.Put(mChildID, extraArgs);
   geckoargs::sIsForBrowser.Put(IsForBrowser(), extraArgs);
   geckoargs::sNotForBrowser.Put(!IsForBrowser(), extraArgs);
 
@@ -2541,14 +2537,19 @@ bool ContentParent::LaunchSubprocessResolve(bool aIsSync,
   return true;
 }
 
+static bool IsFileContent(const nsACString& aRemoteType) {
+  return aRemoteType == FILE_REMOTE_TYPE;
+}
+
 ContentParent::ContentParent(const nsACString& aRemoteType)
-    : mSubprocess(nullptr),
+    : mSubprocess(new GeckoChildProcessHost(GeckoProcessType_Content,
+                                            IsFileContent(aRemoteType))),
       mLaunchTS(TimeStamp::Now()),
       mLaunchYieldTS(mLaunchTS),
       mActivateTS(mLaunchTS),
       mIsAPreallocBlocker(false),
       mRemoteType(aRemoteType),
-      mChildID(gContentChildID++),
+      mChildID(mSubprocess->GetChildID()),
       mGeolocationWatchID(-1),
       mThreadsafeHandle(
           new ThreadsafeContentParentHandle(this, mChildID, mRemoteType)),
@@ -2569,6 +2570,8 @@ ContentParent::ContentParent(const nsACString& aRemoteType)
       mBlockShutdownCalled(false),
 #endif
       mHangMonitorActor(nullptr) {
+  MOZ_ASSERT(NS_IsMainThread(), "Wrong thread!");
+
   mRemoteTypeIsolationPrincipal =
       CreateRemoteTypeIsolationPrincipal(aRemoteType);
 
@@ -2588,13 +2591,9 @@ ContentParent::ContentParent(const nsACString& aRemoteType)
       MessageChannel::REQUIRE_DEFERRED_MESSAGE_PROTECTION);
 #endif
 
-  NS_ASSERTION(NS_IsMainThread(), "Wrong thread!");
-  bool isFile = mRemoteType == FILE_REMOTE_TYPE;
-  mSubprocess = new GeckoChildProcessHost(GeckoProcessType_Content, isFile);
   MOZ_LOG(ContentParent::GetLog(), LogLevel::Verbose,
-          ("CreateSubprocess: ContentParent %p mSubprocess %p handle %" PRIuPTR,
-           this, mSubprocess,
-           mSubprocess ? (uintptr_t)mSubprocess->GetChildProcessHandle() : -1));
+          ("CreateSubprocess: ContentParent %p mSubprocess %p childID %d", this,
+           mSubprocess, mSubprocess->GetChildID()));
 }
 
 ContentParent::~ContentParent() {
@@ -3248,7 +3247,6 @@ mozilla::ipc::IPCResult ContentParent::RecvClipboardHasType(
 }
 
 namespace {
-
 static Result<ClipboardReadRequest, nsresult> CreateClipboardReadRequest(
     ContentParent& aContentParent,
     nsIClipboardDataSnapshot& aClipboardDataSnapshot) {

dom/ipc/ContentParent.h

@@ -464,6 +464,13 @@ class ContentParent final : public PContentParent,
    */
   void KillHard(const char* aReason);
 
+  /**
+   * Get a unique identifier for this child process. This ID is unique across
+   * all types of child processes.
+   *
+   * NOTE: The `ContentParentId` wrapper type is a historical artifact from when
+   * the ID was only specific to content processes.
+   */
   ContentParentId ChildID() const { return mChildID; }
 
   /**

dom/ipc/ContentProcess.cpp

@@ -67,7 +67,6 @@ ContentProcess::ContentProcess(ProcessId aParentPid,
 ContentProcess::~ContentProcess() { NS_LogTerm(); }
 
 bool ContentProcess::Init(int aArgc, char* aArgv[]) {
-  Maybe<uint64_t> childID = geckoargs::sChildID.Get(aArgc, aArgv);
   Maybe<bool> isForBrowser = Nothing();
   Maybe<const char*> parentBuildID =
       geckoargs::sParentBuildID.Get(aArgc, aArgv);
@@ -122,8 +121,7 @@ bool ContentProcess::Init(int aArgc, char* aArgv[]) {
 #endif /* XP_MACOSX && MOZ_SANDBOX */
 
   // Did we find all the mandatory flags?
-  if (childID.isNothing() || isForBrowser.isNothing() ||
-      parentBuildID.isNothing()) {
+  if (isForBrowser.isNothing() || parentBuildID.isNothing()) {
     return false;
   }
 
@@ -136,7 +134,7 @@ bool ContentProcess::Init(int aArgc, char* aArgv[]) {
     return false;
   }
 
-  mContent.Init(TakeInitialEndpoint(), *parentBuildID, *childID, *isForBrowser);
+  mContent.Init(TakeInitialEndpoint(), *parentBuildID, *isForBrowser);
 
   nsCOMPtr<nsIFile> greDir;
   nsresult rv = GetGREDir(getter_AddRefs(greDir));

toolkit/xre/GeckoArgs.h

@@ -121,8 +121,6 @@ static CommandLineArg<uint64_t> sPrefMapHandle{"-prefMapHandle",
                                                "prefmaphandle"};
 static CommandLineArg<uint64_t> sPrefMapSize{"-prefMapSize", "prefmapsize"};
 
-static CommandLineArg<uint64_t> sChildID{"-childID", "childid"};
-
 static CommandLineArg<uint64_t> sSandboxingKind{"-sandboxingKind",
                                                 "sandboxingkind"};