Bug 1814798 - pt 2. Add a PHCManager component to control PHC r=glandium,emilio

This change adds the PHCManager class which observes a pref to control PHC.
The pref can be changed at runtime and will affect the parent and content
processes.

Differential Revision: https://phabricator.services.mozilla.com/D178754

memory/replace/phc/PHC.cpp

@@ -324,7 +324,7 @@ static const size_t kAllPagesSize = kNumAllPages * kPageSize;
 static const size_t kAllPagesJemallocSize = kAllPagesSize - kPageSize;
 
 // The default state for PHC.  Either Enabled or OnlyFree.
-#define DEFAULT_STATE mozilla::phc::Enabled
+#define DEFAULT_STATE mozilla::phc::OnlyFree
 
 // The junk value used to fill new allocation in debug builds. It's same value
 // as the one used by mozjemalloc. PHC applies it unconditionally in debug

modules/libpref/init/StaticPrefList.yaml

@@ -11010,6 +11010,19 @@
     mirror: always
 #endif
 
+#---------------------------------------------------------------------------
+# Prefs starting with "memory."
+#---------------------------------------------------------------------------
+
+- name: memory.phc.enabled
+  type: bool
+#if defined(MOZ_PHC)
+  value: true
+#else
+  value: false
+#endif
+  mirror: always
+
 #---------------------------------------------------------------------------
 # Prefs starting with "midi."
 #---------------------------------------------------------------------------

modules/libpref/moz.build

@@ -62,6 +62,7 @@ pref_groups = [
     "layout",
     "mathml",
     "media",
+    "memory",
     "midi",
     "mousewheel",
     "mozilla",
@@ -172,3 +173,6 @@ else:
     FINAL_TARGET_PP_FILES += [
         "greprefs.js",
     ]
+
+if CONFIG["MOZ_PHC"]:
+    DEFINES["MOZ_PHC"] = True

xpcom/base/PHCManager.cpp

@@ -0,0 +1,35 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim:set ts=2 sw=2 sts=2 et cindent: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "PHCManager.h"
+
+#include "replace_malloc_bridge.h"
+#include "mozilla/Preferences.h"
+#include "mozilla/StaticPrefs_memory.h"
+
+namespace mozilla {
+
+using namespace phc;
+
+static const char kPHCPref[] = "memory.phc.enabled";
+
+static PHCState GetPHCStateFromPref() {
+  return StaticPrefs::memory_phc_enabled() ? Enabled : OnlyFree;
+}
+
+static void PrefChangeCallback(const char* aPrefName, void* aNull) {
+  MOZ_ASSERT(0 == strcmp(aPrefName, kPHCPref));
+
+  ReplaceMalloc::SetPHCState(GetPHCStateFromPref());
+}
+
+void InitPHCState() {
+  ReplaceMalloc::SetPHCState(GetPHCStateFromPref());
+
+  Preferences::RegisterCallback(PrefChangeCallback, kPHCPref);
+}
+
+};  // namespace mozilla

xpcom/base/PHCManager.h

@@ -0,0 +1,18 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim:set ts=2 sw=2 sts=2 et cindent: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_PHCManager_h
+#define mozilla_PHCManager_h
+
+namespace mozilla {
+
+// Read the PHC pref and potentially initialise PHC.  Also register a
+// callback for the pref to update PHC as the pref changes.
+void InitPHCState();
+
+};  // namespace mozilla
+
+#endif  // mozilla_PHCManager_h

xpcom/base/moz.build

@@ -257,3 +257,15 @@ LOCAL_INCLUDES += [
 
 if CONFIG["MOZ_WIDGET_TOOLKIT"] == "gtk":
     CXXFLAGS += CONFIG["MOZ_GTK3_CFLAGS"]
+
+if CONFIG["MOZ_PHC"]:
+    EXPORTS.mozilla += [
+        "PHCManager.h",
+    ]
+
+    DEFINES["MOZ_PHC"] = 1
+
+    UNIFIED_SOURCES += ["PHCManager.cpp"]
+
+with Files("PHCManager.*"):
+    BUG_COMPONENT = ("Core", "Memory Allocator")

xpcom/build/XPCOMInit.cpp

@@ -89,6 +89,9 @@
 #include "mozilla/AvailableMemoryTracker.h"
 #include "mozilla/ClearOnShutdown.h"
 #include "mozilla/CountingAllocatorBase.h"
+#ifdef MOZ_PHC
+#  include "mozilla/PHCManager.h"
+#endif
 #include "mozilla/UniquePtr.h"
 #include "mozilla/ServoStyleConsts.h"
 
@@ -448,6 +451,12 @@ NS_InitXPCOM(nsIServiceManager** aResult, nsIFile* aBinDirectory,
     NS_ADDREF(*aResult = nsComponentManagerImpl::gComponentManager);
   }
 
+#ifdef MOZ_PHC
+  // This is the earliest possible moment we can start PHC while still being
+  // able to read prefs.
+  mozilla::InitPHCState();
+#endif
+
   // After autoreg, but before we actually instantiate any components,
   // add any services listed in the "xpcom-directory-providers" category
   // to the directory service.

xpcom/build/moz.build

@@ -103,3 +103,6 @@ if CONFIG["MOZ_VPX"]:
     LOCAL_INCLUDES += [
         "/media/libvpx",
     ]
+
+if CONFIG["MOZ_PHC"]:
+    DEFINES["MOZ_PHC"] = 1