Bug 1471132 - Avoid ASAN padding between NSModules. r=froydnj

--HG--
extra : rebase_source : 480ea315a847ffb63a8cb1e583669a61f1a7f3eb

python/mozbuild/mozbuild/action/check_binary.py

@@ -40,9 +40,7 @@ TARGET = {
     'nm': '{}nm'.format(buildconfig.substs.get('TOOLCHAIN_PREFIX', '')),
 }
 
-if buildconfig.substs.get('MOZ_ASAN'):
-    GUESSED_NSMODULE_SIZE = 64
-elif buildconfig.substs.get('HAVE_64BIT_BUILD'):
+if buildconfig.substs.get('HAVE_64BIT_BUILD'):
     GUESSED_NSMODULE_SIZE = 8
 else:
     GUESSED_NSMODULE_SIZE = 4

xpcom/components/Module.h

@@ -11,6 +11,7 @@
 #include "nsID.h"
 #include "nsIFactory.h"
 #include "nsCOMPtr.h" // for already_AddRefed
+#include "mozilla/Attributes.h"
 
 namespace mozilla {
 
@@ -148,7 +149,12 @@ struct Module
 #  if !defined(NSMODULE_SECTION)
 #    error Do not know how to define sections.
 #  endif
-#  define NSMODULE_DEFN(_name) extern NSMODULE_SECTION mozilla::Module const *const NSMODULE_NAME(_name)
+#  if defined(MOZ_HAVE_ASAN_BLACKLIST)
+#    define NSMODULE_ASAN_BLACKLIST __attribute__((no_sanitize_address))
+#  else
+#    define NSMODULE_ASAN_BLACKLIST
+#  endif
+#  define NSMODULE_DEFN(_name) extern NSMODULE_SECTION NSMODULE_ASAN_BLACKLIST mozilla::Module const *const NSMODULE_NAME(_name)
 #else
 #  define NSMODULE_NAME(_name) NSModule
 #  define NSMODULE_DEFN(_name) extern "C" NS_EXPORT mozilla::Module const *const NSModule

xpcom/components/nsComponentManager.cpp

@@ -250,12 +250,6 @@ nsTArray<const mozilla::Module*>* nsComponentManagerImpl::sStaticModules;
 NSMODULE_DEFN(start_kPStaticModules);
 NSMODULE_DEFN(end_kPStaticModules);
 
-/* The content between start_kPStaticModules and end_kPStaticModules is gathered
- * by the linker from various objects containing symbols in a specific section.
- * ASAN considers (rightfully) the use of this content as a global buffer
- * overflow. But this is a deliberate and well-considered choice, with no proper
- * way to make ASAN happy. */
-MOZ_ASAN_BLACKLIST
 /* static */ void
 nsComponentManagerImpl::InitializeStaticModules()
 {
@@ -267,9 +261,7 @@ nsComponentManagerImpl::InitializeStaticModules()
   for (const mozilla::Module * const* staticModules =
          &NSMODULE_NAME(start_kPStaticModules) + 1;
        staticModules < &NSMODULE_NAME(end_kPStaticModules); ++staticModules)
-    if (*staticModules) { // ASAN adds padding
-      sStaticModules->AppendElement(*staticModules);
-    }
+    sStaticModules->AppendElement(*staticModules);
 }
 
 nsTArray<nsComponentManagerImpl::ComponentLocation>*