JSC should use a shadow stack version of CHICKEN so that debuggers have the option of retrieving tail-deleted frames
https://bugs.webkit.org/show_bug.cgi?id=155598
Reviewed by Saam Barati.
PerformanceTests/SunSpider:
* shadow-chicken.yaml: Added.
Source/JavaScriptCore:
JSC is the first JSVM to have proper tail calls. This means that error.stack and the
debugger will appear to "delete" strict mode stack frames, if the call that this frame made
was in tail position. This is exactly what functional programmers expect - they don't want
the VM to waste resources on tail-deleted frames to ensure that it's legal to loop forever
using tail calls. It's also something that non-functional programmers fear. It's not clear
that tail-deleted frames would actually degrade the debugging experience, but the fear is
real, so it's worthwhile to do something about it.
It turns out that there is at least one tail call implementation that doesn't suffer from
this problem. It implements proper tail calls in the sense that you won't run out of memory
by tail-looping. It also has the power to show you tail-deleted frames in a backtrace, so
long as you haven't yet run out of memory. It's called CHICKEN Scheme, and it's one of my
favorite hacks:
http://www.more-magic.net/posts/internals-gc.html
CHICKEN does many awesome things. The intuition from CHICKEN that we use here is a simple
one: what if a tail call still kept the tail-deleted frame, and the GC actually deleted that
frame only once we proved that there was insufficient memory to keep it around.
CHICKEN does this by reshaping the C stack with longjmp/setjmp. We can't do that because we
can have arbitrary native code, and that native code does not have relocatable stack frames.
But we can do something almost like CHICKEN on a shadow stack. It's a common trick to have a
VM maintain two stacks - the actual execution stack plus a shadow stack that has some extra
information. The shadow stack can be reshaped, moved, etc, since the VM tightly controls its
layout. The main stack can then continue to obey ABI rules.
This patch implements a mechanism for being able to display stack traces that include
tail-deleted frames. It uses a shadow stack that behaves like a CHICKEN stack: it has all
frames all the time, though we will collect the tail-deleted ones if the stack gets too big.
This new mechanism is called ShadowChicken, obviously: it's CHICKEN on a shadow stack.
ShadowChicken is always on, but individual CodeBlocks may make their own choices about
whether to opt into it. They will do that at bytecompile time based on the debugger mode on
their global object.
When no CodeBlock opts in, there is no overhead, since ShadowChicken ends up doing nothing
in that case. Well, except when exceptions are thrown. Then it might do some work, but it's
minor.
When all CodeBlocks opt in, there is about 6% overhead. That's too much overhead to enable
this all the time, but it's low enough to justify enabling in the Inspector. It's currently
enabled on all CodeBlocks only when you use an Option. Otherwise it will auto-enable if the
debugger is on.
Note that ShadowChicken attempts to gracefully handle the presence of stack frames that have
no logging. This is essential since we *can* have debugging enabled in one GlobalObject and
disabled in another. Also, some frames don't do ShadowChicken because they just haven't been
hacked to do it yet. Native frames fall into this category, as do the VM entry frames.
This doesn't yet wire ShadowChicken into DebuggerCallFrame. That will take more work. It
just makes a ShadowChicken stack walk function available to jsc. It's used from the
shadow-chicken tests.
* API/JSContextRef.cpp:
(BacktraceFunctor::BacktraceFunctor):
(BacktraceFunctor::operator()):
(JSContextCreateBacktrace):
* CMakeLists.txt:
* JavaScriptCore.xcodeproj/project.pbxproj:
* bytecode/BytecodeList.json:
* bytecode/BytecodeUseDef.h:
(JSC::computeUsesForBytecodeOffset):
(JSC::computeDefsForBytecodeOffset):
* bytecode/CodeBlock.cpp:
(JSC::CodeBlock::dumpBytecode):
(JSC::RecursionCheckFunctor::RecursionCheckFunctor):
(JSC::RecursionCheckFunctor::operator()):
(JSC::CodeBlock::noticeIncomingCall):
* bytecompiler/BytecodeGenerator.cpp:
(JSC::BytecodeGenerator::emitEnter):
(JSC::BytecodeGenerator::emitCallInTailPosition):
(JSC::BytecodeGenerator::emitCallVarargsInTailPosition):
(JSC::BytecodeGenerator::emitCallVarargs):
(JSC::BytecodeGenerator::emitLogShadowChickenPrologueIfNecessary):
(JSC::BytecodeGenerator::emitLogShadowChickenTailIfNecessary):
(JSC::BytecodeGenerator::emitCallDefineProperty):
* bytecompiler/BytecodeGenerator.h:
* debugger/DebuggerCallFrame.cpp:
(JSC::LineAndColumnFunctor::operator()):
(JSC::LineAndColumnFunctor::column):
(JSC::FindCallerMidStackFunctor::FindCallerMidStackFunctor):
(JSC::FindCallerMidStackFunctor::operator()):
(JSC::DebuggerCallFrame::DebuggerCallFrame):
* dfg/DFGAbstractInterpreterInlines.h:
(JSC::DFG::AbstractInterpreter<AbstractStateType>::executeEffects):
* dfg/DFGByteCodeParser.cpp:
(JSC::DFG::ByteCodeParser::parseBlock):
* dfg/DFGClobberize.h:
(JSC::DFG::clobberize):
* dfg/DFGDoesGC.cpp:
(JSC::DFG::doesGC):
* dfg/DFGFixupPhase.cpp:
(JSC::DFG::FixupPhase::fixupNode):
* dfg/DFGNodeType.h:
* dfg/DFGPredictionPropagationPhase.cpp:
(JSC::DFG::PredictionPropagationPhase::propagate):
* dfg/DFGSafeToExecute.h:
(JSC::DFG::safeToExecute):
* dfg/DFGSpeculativeJIT32_64.cpp:
(JSC::DFG::SpeculativeJIT::compile):
* dfg/DFGSpeculativeJIT64.cpp:
(JSC::DFG::SpeculativeJIT::compile):
* ftl/FTLAbstractHeapRepository.cpp:
* ftl/FTLAbstractHeapRepository.h:
* ftl/FTLCapabilities.cpp:
(JSC::FTL::canCompile):
* ftl/FTLLowerDFGToB3.cpp:
(JSC::FTL::DFG::LowerDFGToB3::compileNode):
(JSC::FTL::DFG::LowerDFGToB3::compileSetRegExpObjectLastIndex):
(JSC::FTL::DFG::LowerDFGToB3::compileLogShadowChickenPrologue):
(JSC::FTL::DFG::LowerDFGToB3::compileLogShadowChickenTail):
(JSC::FTL::DFG::LowerDFGToB3::didOverflowStack):
(JSC::FTL::DFG::LowerDFGToB3::allocateJSArray):
(JSC::FTL::DFG::LowerDFGToB3::setupShadowChickenPacket):
(JSC::FTL::DFG::LowerDFGToB3::boolify):
* heap/Heap.cpp:
(JSC::Heap::markRoots):
(JSC::Heap::visitSamplingProfiler):
(JSC::Heap::visitShadowChicken):
(JSC::Heap::traceCodeBlocksAndJITStubRoutines):
(JSC::Heap::collectImpl):
* heap/Heap.h:
* inspector/ScriptCallStackFactory.cpp:
(Inspector::CreateScriptCallStackFunctor::CreateScriptCallStackFunctor):
(Inspector::CreateScriptCallStackFunctor::operator()):
(Inspector::createScriptCallStack):
* interpreter/CallFrame.h:
(JSC::ExecState::iterate):
* interpreter/Interpreter.cpp:
(JSC::DumpRegisterFunctor::DumpRegisterFunctor):
(JSC::DumpRegisterFunctor::operator()):
(JSC::GetStackTraceFunctor::GetStackTraceFunctor):
(JSC::GetStackTraceFunctor::operator()):
(JSC::Interpreter::getStackTrace):
(JSC::GetCatchHandlerFunctor::handler):
(JSC::GetCatchHandlerFunctor::operator()):
(JSC::notifyDebuggerOfUnwinding):
(JSC::UnwindFunctor::UnwindFunctor):
(JSC::UnwindFunctor::operator()):
(JSC::UnwindFunctor::copyCalleeSavesToVMCalleeSavesBuffer):
* interpreter/ShadowChicken.cpp: Added.
(JSC::ShadowChicken::Packet::dump):
(JSC::ShadowChicken::Frame::dump):
(JSC::ShadowChicken::ShadowChicken):
(JSC::ShadowChicken::~ShadowChicken):
(JSC::ShadowChicken::log):
(JSC::ShadowChicken::update):
(JSC::ShadowChicken::visitChildren):
(JSC::ShadowChicken::reset):
(JSC::ShadowChicken::dump):
(JSC::ShadowChicken::functionsOnStack):
* interpreter/ShadowChicken.h: Added.
(JSC::ShadowChicken::Packet::Packet):
(JSC::ShadowChicken::Packet::tailMarker):
(JSC::ShadowChicken::Packet::throwMarker):
(JSC::ShadowChicken::Packet::prologue):
(JSC::ShadowChicken::Packet::tail):
(JSC::ShadowChicken::Packet::throwPacket):
(JSC::ShadowChicken::Packet::operator bool):
(JSC::ShadowChicken::Packet::isPrologue):
(JSC::ShadowChicken::Packet::isTail):
(JSC::ShadowChicken::Packet::isThrow):
(JSC::ShadowChicken::Frame::Frame):
(JSC::ShadowChicken::Frame::operator==):
(JSC::ShadowChicken::Frame::operator!=):
(JSC::ShadowChicken::log):
(JSC::ShadowChicken::logSize):
(JSC::ShadowChicken::addressOfLogCursor):
(JSC::ShadowChicken::logEnd):
* interpreter/ShadowChickenInlines.h: Added.
(JSC::ShadowChicken::iterate):
* interpreter/StackVisitor.h:
(JSC::StackVisitor::Frame::callee):
(JSC::StackVisitor::Frame::codeBlock):
(JSC::StackVisitor::Frame::bytecodeOffset):
(JSC::StackVisitor::Frame::inlineCallFrame):
(JSC::StackVisitor::Frame::isJSFrame):
(JSC::StackVisitor::Frame::isInlinedFrame):
(JSC::StackVisitor::visit):
* jit/CCallHelpers.cpp: Added.
(JSC::CCallHelpers::logShadowChickenProloguePacket):
(JSC::CCallHelpers::logShadowChickenTailPacket):
(JSC::CCallHelpers::setupShadowChickenPacket):
* jit/CCallHelpers.h:
(JSC::CCallHelpers::prepareForTailCallSlow):
* jit/JIT.cpp:
(JSC::JIT::privateCompileMainPass):
* jit/JIT.h:
* jit/JITExceptions.cpp:
(JSC::genericUnwind):
* jit/JITOpcodes.cpp:
(JSC::JIT::emit_op_resume):
(JSC::JIT::emit_op_log_shadow_chicken_prologue):
(JSC::JIT::emit_op_log_shadow_chicken_tail):
* jit/JITOperations.cpp:
* jit/JITOperations.h:
* jsc.cpp:
(GlobalObject::finishCreation):
(FunctionJSCStackFunctor::FunctionJSCStackFunctor):
(FunctionJSCStackFunctor::operator()):
(functionClearSamplingFlags):
(functionShadowChickenFunctionsOnStack):
(functionReadline):
* llint/LLIntOffsetsExtractor.cpp:
* llint/LLIntSlowPaths.cpp:
(JSC::LLInt::LLINT_SLOW_PATH_DECL):
(JSC::LLInt::llint_throw_stack_overflow_error):
* llint/LLIntSlowPaths.h:
* llint/LowLevelInterpreter.asm:
* profiler/ProfileGenerator.cpp:
(JSC::AddParentForConsoleStartFunctor::foundParent):
(JSC::AddParentForConsoleStartFunctor::operator()):
* runtime/Error.cpp:
(JSC::FindFirstCallerFrameWithCodeblockFunctor::FindFirstCallerFrameWithCodeblockFunctor):
(JSC::FindFirstCallerFrameWithCodeblockFunctor::operator()):
(JSC::addErrorInfoAndGetBytecodeOffset):
* runtime/JSFunction.cpp:
(JSC::RetrieveArgumentsFunctor::result):
(JSC::RetrieveArgumentsFunctor::operator()):
(JSC::retrieveArguments):
(JSC::RetrieveCallerFunctionFunctor::result):
(JSC::RetrieveCallerFunctionFunctor::operator()):
(JSC::retrieveCallerFunction):
* runtime/JSGlobalObjectFunctions.cpp:
(JSC::GlobalFuncProtoGetterFunctor::result):
(JSC::GlobalFuncProtoGetterFunctor::operator()):
(JSC::globalFuncProtoGetter):
(JSC::GlobalFuncProtoSetterFunctor::allowsAccess):
(JSC::GlobalFuncProtoSetterFunctor::operator()):
* runtime/NullSetterFunction.cpp:
(JSC::GetCallerStrictnessFunctor::GetCallerStrictnessFunctor):
(JSC::GetCallerStrictnessFunctor::operator()):
(JSC::GetCallerStrictnessFunctor::callerIsStrict):
(JSC::callerIsStrict):
* runtime/ObjectConstructor.cpp:
(JSC::ObjectConstructorGetPrototypeOfFunctor::result):
(JSC::ObjectConstructorGetPrototypeOfFunctor::operator()):
(JSC::objectConstructorGetPrototypeOf):
* runtime/Options.h:
* runtime/VM.cpp:
(JSC::VM::VM):
(JSC::SetEnabledProfilerFunctor::operator()):
* runtime/VM.h:
(JSC::VM::shouldBuilderPCToCodeOriginMapping):
(JSC::VM::bytecodeIntrinsicRegistry):
(JSC::VM::shadowChicken):
* tests/stress/resources/shadow-chicken-support.js: Added.
(describeFunction):
(describeArray):
(expectStack):
(initialize):
* tests/stress/shadow-chicken-disabled.js: Added.
(test1.foo):
(test1.bar):
(test1.baz):
(test1):
(test2.foo):
(test2.bar):
(test2.baz):
(test2):
(test3.foo):
(test3.bar):
(test3.baz):
(test3):
* tests/stress/shadow-chicken-enabled.js: Added.
(test1.foo):
(test1.bar):
(test1.baz):
(test1):
(test2.foo):
(test2.bar):
(test2.baz):
(test2):
(test3.bob):
(test3.thingy):
(test3.foo):
(test3.bar):
(test3.baz):
(test3):
(test4.bob):
(test4.thingy):
(test4.foo):
(test4.bar):
(test4.baz):
(test4):
(test5.foo):
(test5):
* tools/JSDollarVMPrototype.cpp:
(JSC::CallerFrameJITTypeFunctor::CallerFrameJITTypeFunctor):
(JSC::CallerFrameJITTypeFunctor::operator()):
(JSC::CallerFrameJITTypeFunctor::jitType):
(JSC::functionLLintTrue):
(JSC::CellAddressCheckFunctor::CellAddressCheckFunctor):
(JSC::CellAddressCheckFunctor::operator()):
(JSC::JSDollarVMPrototype::isValidCell):
(JSC::JSDollarVMPrototype::isValidCodeBlock):
(JSC::JSDollarVMPrototype::codeBlockForFrame):
(JSC::PrintFrameFunctor::PrintFrameFunctor):
(JSC::PrintFrameFunctor::operator()):
(JSC::printCallFrame):
Source/WebCore:
Fixed some uses of the stack walking functor to obey the new lambda-friendly API, which
requires that operator() is const.
No new tests because no change in behavior.
* bindings/js/JSXMLHttpRequestCustom.cpp:
(WebCore::SendFunctor::column):
(WebCore::SendFunctor::url):
(WebCore::SendFunctor::operator()):
(WebCore::JSXMLHttpRequest::send):
* testing/Internals.cpp:
(WebCore::GetCallerCodeBlockFunctor::GetCallerCodeBlockFunctor):
(WebCore::GetCallerCodeBlockFunctor::operator()):
(WebCore::GetCallerCodeBlockFunctor::codeBlock):
(WebCore::Internals::parserMetaData):
git-svn-id: http://svn.webkit.org/repository/webkit/trunk@199076 268f45cc-cd09-0410-ab3c-d52691b4dbfc
diff --git a/Source/JavaScriptCore/dfg/DFGAbstractInterpreterInlines.h b/Source/JavaScriptCore/dfg/DFGAbstractInterpreterInlines.h
index f284d18..7ca6bbc 100644
--- a/Source/JavaScriptCore/dfg/DFGAbstractInterpreterInlines.h
+++ b/Source/JavaScriptCore/dfg/DFGAbstractInterpreterInlines.h
@@ -2626,6 +2626,8 @@
break;
case CheckWatchdogTimer:
+ case LogShadowChickenPrologue:
+ case LogShadowChickenTail:
break;
case ProfileWillCall:
