Do not install the VMTraps signal handler if Options::useJIT=false.

https://bugs.webkit.org/show_bug.cgi?id=212543
<rdar://problem/63772519>

Reviewed by Keith Miller.

VMTraps is only needed for JITted code.  Hence, if the JIT is disabled, we should
set Options::usePollingTraps() to true to indicate that we won't be using VMTraps.

With this change, we no longer install any signal handling machinery if
Options::useJIT() is false.

Because we may still disable the JIT even if useJIT() is true (due to failure to
allocate JIT memory or a number of other factors), we will also add a check of
VM::canUseJIT() in initializeThreading(), and disable useJIT() if needed.  Of
course, this also means we need to call Options::recomputeDependentOptions() to
make other options consistent with useJIT() being false.

* runtime/InitializeThreading.cpp:
(JSC::initializeThreading):
* runtime/Options.cpp:
(JSC::disableAllJITOptions):
(JSC::Options::recomputeDependentOptions):
(JSC::recomputeDependentOptions): Deleted.
* runtime/Options.h:
* runtime/VMTraps.cpp:
(JSC::VMTraps::initializeSignals):
* tools/SigillCrashAnalyzer.cpp:
(JSC::SigillCrashAnalyzer::instance):



Canonical link: https://commits.webkit.org/225993@main
git-svn-id: https://svn.webkit.org/repository/webkit/trunk@263055 268f45cc-cd09-0410-ab3c-d52691b4dbfc

Source/JavaScriptCore/ChangeLog

@@ -1,3 +1,35 @@
+2020-06-15  Mark Lam  <mark.lam@apple.com>
+
+        Do not install the VMTraps signal handler if Options::useJIT=false.
+        https://bugs.webkit.org/show_bug.cgi?id=212543
+        <rdar://problem/63772519>
+
+        Reviewed by Keith Miller.
+
+        VMTraps is only needed for JITted code.  Hence, if the JIT is disabled, we should
+        set Options::usePollingTraps() to true to indicate that we won't be using VMTraps.
+
+        With this change, we no longer install any signal handling machinery if
+        Options::useJIT() is false.
+
+        Because we may still disable the JIT even if useJIT() is true (due to failure to
+        allocate JIT memory or a number of other factors), we will also add a check of
+        VM::canUseJIT() in initializeThreading(), and disable useJIT() if needed.  Of
+        course, this also means we need to call Options::recomputeDependentOptions() to
+        make other options consistent with useJIT() being false.
+
+        * runtime/InitializeThreading.cpp:
+        (JSC::initializeThreading):
+        * runtime/Options.cpp:
+        (JSC::disableAllJITOptions):
+        (JSC::Options::recomputeDependentOptions):
+        (JSC::recomputeDependentOptions): Deleted.
+        * runtime/Options.h:
+        * runtime/VMTraps.cpp:
+        (JSC::VMTraps::initializeSignals):
+        * tools/SigillCrashAnalyzer.cpp:
+        (JSC::SigillCrashAnalyzer::instance):
+
 2020-06-15  Keith Miller  <keith_miller@apple.com>
 
         CheckIsConstant should not use BadCache exit kind

Source/JavaScriptCore/runtime/InitializeThreading.cpp

@@ -66,8 +66,12 @@ void initializeThreading()
 
         ExecutableAllocator::initialize();
         VM::computeCanUseJIT();
+        if (!VM::canUseJIT()) {
+            Options::useJIT() = false;
+            Options::recomputeDependentOptions();
+        }
 
-        if (VM::canUseJIT() && Options::useSigillCrashAnalyzer())
+        if (Options::useSigillCrashAnalyzer())
             enableSigillCrashAnalyzer();
 
         LLInt::initialize();

Source/JavaScriptCore/runtime/Options.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2011-2019 Apple Inc. All rights reserved.
+ * Copyright (C) 2011-2020 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
@@ -375,19 +375,24 @@ static void correctOptions()
         Options::thresholdForGlobalLexicalBindingEpoch() = UINT_MAX;
 }
 
-static void recomputeDependentOptions()
+static void disableAllJITOptions()
 {
-#if !defined(NDEBUG)
-    Options::validateDFGExceptionHandling() = true;
-#endif
-#if !ENABLE(JIT)
     Options::useLLInt() = true;
     Options::useJIT() = false;
     Options::useBaselineJIT() = false;
     Options::useDFGJIT() = false;
     Options::useFTLJIT() = false;
     Options::useDOMJIT() = false;
     Options::useRegExpJIT() = false;
+}
+
+void Options::recomputeDependentOptions()
+{
+#if !defined(NDEBUG)
+    Options::validateDFGExceptionHandling() = true;
+#endif
+#if !ENABLE(JIT)
+    disableAllJITOptions();
 #endif
 #if !ENABLE(CONCURRENT_JS)
     Options::useConcurrentJIT() = false;
@@ -407,9 +412,15 @@ static void recomputeDependentOptions()
     Options::useConcurrentGC() = false;
 #endif
 
+    // At initialization time, we may decide that useJIT should be false for any
+    // number of reasons (including failing to allocate JIT memory), and therefore,
+    // will / should not be able to enable any JIT related services.
     if (!Options::useJIT()) {
+        disableAllJITOptions();
+        Options::useConcurrentJIT() = false;
         Options::useSigillCrashAnalyzer() = false;
         Options::useWebAssembly() = false;
+        Options::usePollingTraps() = true;
     }
 
     if (!jitEnabledByDefault() && !Options::useJIT())

Source/JavaScriptCore/runtime/Options.h

@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2011-2019 Apple Inc. All rights reserved.
+ * Copyright (C) 2011-2020 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
@@ -87,6 +87,7 @@ class Options {
     JS_EXPORT_PRIVATE static void dumpAllOptionsInALine(StringBuilder&);
 
     JS_EXPORT_PRIVATE static void ensureOptionsAreCoherent();
+    static void recomputeDependentOptions();
 
 #define DECLARE_OPTION_ACCESSORS(type_, name_, defaultValue_, availability_, description_) \
     ALWAYS_INLINE static OptionsStorage::type_& name_() { return g_jscConfig.options.name_; }  \

Source/JavaScriptCore/runtime/VMTraps.cpp

@@ -297,8 +297,10 @@ class VMTraps::SignalSender final : public AutomaticThread {
 void VMTraps::initializeSignals()
 {
 #if ENABLE(SIGNAL_BASED_VM_TRAPS)
-    if (!Options::usePollingTraps())
+    if (!Options::usePollingTraps()) {
+        ASSERT(Options::useJIT());
         SignalSender::initializeSignals();
+    }
 #endif
 }
 

Source/JavaScriptCore/tools/SigillCrashAnalyzer.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2017-2018 Apple Inc. All rights reserved.
+ * Copyright (C) 2017-2020 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
@@ -199,6 +199,7 @@ SigillCrashAnalyzer& SigillCrashAnalyzer::instance()
     static SigillCrashAnalyzer* analyzer;
     static std::once_flag once;
     std::call_once(once, [] {
+        ASSERT(Options::useJIT());
         installCrashHandler();
         analyzer = new SigillCrashAnalyzer;
     });