From f0c84ea9eb9bd43f0428aa739bc037f75eb4c941 Mon Sep 17 00:00:00 2001
From: Bill McCloskey <wmccloskey@mozilla.com>
Date: Wed, 28 Jan 2015 11:53:46 -0800
Subject: [PATCH] Bug 1126042 - Use different window IDs for different
 processes (r=smaug)

---
 dom/base/nsGlobalWindow.cpp | 10 ++++++++--
 dom/ipc/ContentChild.cpp    | 35 +++++++++++++++++++++++++++++++++++
 dom/ipc/ContentChild.h      |  3 +++
 3 files changed, 46 insertions(+), 2 deletions(-)

diff --git a/dom/base/nsGlobalWindow.cpp b/dom/base/nsGlobalWindow.cpp
index c8d03dd35f5d..042d7ea265ae 100644
--- a/dom/base/nsGlobalWindow.cpp
+++ b/dom/base/nsGlobalWindow.cpp
@@ -274,7 +274,6 @@ static int32_t              gRunningTimeoutDepth       = 0;
 static bool                 gMouseDown                 = false;
 static bool                 gDragServiceDisabled       = false;
 static FILE                *gDumpFile                  = nullptr;
-static uint64_t             gNextWindowID              = 0;
 static uint32_t             gSerialCounter             = 0;
 static uint32_t             gTimeoutsRecentlySet       = 0;
 static TimeStamp            gLastRecordedRecentTimeouts;
@@ -562,6 +561,13 @@ nsTimeout::HasRefCntOne()
   return mRefCnt.get() == 1;
 }
 
+namespace mozilla {
+namespace dom {
+extern uint64_t
+NextWindowID();
+}
+}
+
 nsPIDOMWindow::nsPIDOMWindow(nsPIDOMWindow *aOuterWindow)
 : mFrameElement(nullptr), mDocShell(nullptr), mModalStateDepth(0),
   mRunningTimeout(nullptr), mMutationBits(0), mIsDocumentLoaded(false),
@@ -576,7 +582,7 @@ nsPIDOMWindow::nsPIDOMWindow(nsPIDOMWindow *aOuterWindow)
   mAudioMuted(false), mAudioVolume(1.0),
   mInnerWindow(nullptr), mOuterWindow(aOuterWindow),
   // Make sure no actual window ends up with mWindowID == 0
-  mWindowID(++gNextWindowID), mHasNotifiedGlobalCreated(false),
+  mWindowID(NextWindowID()), mHasNotifiedGlobalCreated(false),
   mMarkedCCGeneration(0), mSendAfterRemotePaint(false)
  {}
 
diff --git a/dom/ipc/ContentChild.cpp b/dom/ipc/ContentChild.cpp
index 21021a9426d3..690becc1d95a 100644
--- a/dom/ipc/ContentChild.cpp
+++ b/dom/ipc/ContentChild.cpp
@@ -2524,6 +2524,41 @@ ContentChild::GetBrowserOrId(TabChild* aTabChild)
     }
 }
 
+// This code goes here rather than nsGlobalWindow.cpp because nsGlobalWindow.cpp
+// can't include ContentChild.h since it includes windows.h.
+
+static uint64_t gNextWindowID = 0;
+
+// We use only 53 bits for the window ID so that it can be converted to and from
+// a JS value without loss of precision. The upper bits of the window ID hold the
+// process ID. The lower bits identify the window.
+static const uint64_t kWindowIDTotalBits = 53;
+static const uint64_t kWindowIDProcessBits = 22;
+static const uint64_t kWindowIDWindowBits = kWindowIDTotalBits - kWindowIDProcessBits;
+
+// Try to return a window ID that is unique across processes and that will never
+// be recycled.
+uint64_t
+NextWindowID()
+{
+  uint64_t processID = 0;
+  if (XRE_GetProcessType() == GeckoProcessType_Content) {
+    ContentChild* cc = ContentChild::GetSingleton();
+    processID = cc->GetID();
+  }
+
+  MOZ_RELEASE_ASSERT(processID < (uint64_t(1) << kWindowIDProcessBits));
+  uint64_t processBits = processID & ((uint64_t(1) << kWindowIDProcessBits) - 1);
+
+  // Make sure no actual window ends up with mWindowID == 0.
+  uint64_t windowID = ++gNextWindowID;
+
+  MOZ_RELEASE_ASSERT(windowID < (uint64_t(1) << kWindowIDWindowBits));
+  uint64_t windowBits = windowID & ((uint64_t(1) << kWindowIDWindowBits) - 1);
+
+  return (processBits << kWindowIDWindowBits) | windowBits;
+}
+
 } // namespace dom
 } // namespace mozilla
 
diff --git a/dom/ipc/ContentChild.h b/dom/ipc/ContentChild.h
index cf9b7e7434b2..cc850c39cd32 100644
--- a/dom/ipc/ContentChild.h
+++ b/dom/ipc/ContentChild.h
@@ -481,6 +481,9 @@ private:
     DISALLOW_EVIL_CONSTRUCTORS(ContentChild);
 };
 
+uint64_t
+NextWindowID();
+
 } // namespace dom
 } // namespace mozilla