From 9fd77ce12f8c6f7fdaa03eaea0dc1d363e84ed2a Mon Sep 17 00:00:00 2001
From: asharma <asharm28@gmu.edu>
Date: Mon, 7 Feb 2022 20:26:28 +0000
Subject: [PATCH] Bug 1752907: Cut over Hardware Concurrency to finer-grained
 RFP Check r=tjr

Differential Revision: https://phabricator.services.mozilla.com/D137481
---
 dom/base/Navigator.cpp          | 3 ++-
 dom/workers/RuntimeService.cpp  | 5 +++--
 dom/workers/RuntimeService.h    | 2 +-
 dom/workers/WorkerNavigator.cpp | 5 ++++-
 4 files changed, 10 insertions(+), 5 deletions(-)

diff --git a/dom/base/Navigator.cpp b/dom/base/Navigator.cpp
index 4d5a1dd6602c..b9b3fe6621d2 100644
--- a/dom/base/Navigator.cpp
+++ b/dom/base/Navigator.cpp
@@ -645,7 +645,8 @@ uint64_t Navigator::HardwareConcurrency() {
     return 1;
   }
 
-  return rts->ClampedHardwareConcurrency();
+  return rts->ClampedHardwareConcurrency(
+      nsContentUtils::ShouldResistFingerprinting(mWindow->GetExtantDoc()));
 }
 
 namespace {
diff --git a/dom/workers/RuntimeService.cpp b/dom/workers/RuntimeService.cpp
index 0ff821a12a6a..43d299aeba98 100644
--- a/dom/workers/RuntimeService.cpp
+++ b/dom/workers/RuntimeService.cpp
@@ -1994,11 +1994,12 @@ void RuntimeService::MemoryPressureAllWorkers() {
   BroadcastAllWorkers([](auto& worker) { worker.MemoryPressure(); });
 }
 
-uint32_t RuntimeService::ClampedHardwareConcurrency() const {
+uint32_t RuntimeService::ClampedHardwareConcurrency(
+    bool aShouldResistFingerprinting) const {
   // The Firefox Hardware Report says 70% of Firefox users have exactly 2 cores.
   // When the resistFingerprinting pref is set, we want to blend into the crowd
   // so spoof navigator.hardwareConcurrency = 2 to reduce user uniqueness.
-  if (MOZ_UNLIKELY(nsContentUtils::ShouldResistFingerprinting())) {
+  if (MOZ_UNLIKELY(aShouldResistFingerprinting)) {
     return 2;
   }
 
diff --git a/dom/workers/RuntimeService.h b/dom/workers/RuntimeService.h
index 0ca5f99fab6f..ecc0bf4a5b91 100644
--- a/dom/workers/RuntimeService.h
+++ b/dom/workers/RuntimeService.h
@@ -178,7 +178,7 @@ class RuntimeService final : public nsIObserver {
 
   void MemoryPressureAllWorkers();
 
-  uint32_t ClampedHardwareConcurrency() const;
+  uint32_t ClampedHardwareConcurrency(bool aShouldResistFingerprinting) const;
 
   void CrashIfHanging();
 
diff --git a/dom/workers/WorkerNavigator.cpp b/dom/workers/WorkerNavigator.cpp
index cb499d6bd7ae..dacef4227f7e 100644
--- a/dom/workers/WorkerNavigator.cpp
+++ b/dom/workers/WorkerNavigator.cpp
@@ -176,7 +176,10 @@ uint64_t WorkerNavigator::HardwareConcurrency() const {
   RuntimeService* rts = RuntimeService::GetService();
   MOZ_ASSERT(rts);
 
-  return rts->ClampedHardwareConcurrency();
+  WorkerPrivate* aWorkerPrivate = GetCurrentThreadWorkerPrivate();
+  bool rfp = aWorkerPrivate->ShouldResistFingerprinting();
+
+  return rts->ClampedHardwareConcurrency(rfp);
 }
 
 StorageManager* WorkerNavigator::Storage() {