Bug 199399 – [JSC][Win] Support unwind information for LLInt ASM by using MASM directives to get callstack in debugger

• Component: JavaScriptCore
• Status: NEW

[Fujii Hironori]

[JSC][Win] Support unwind information for LLInt ASM by using MASM directives to get callstack in debugger

MASM has directives for debug information.

.SETFRAME | Microsoft Docs
https://docs.microsoft.com/ja-jp/cpp/assembler/masm/dot-setframe?view=vs-2019

VS debugger can't get callstack under JSC. It looks like the following:

> WebKit.dll!WebCore::Node::appendChild(WebCore::Node & newChild) Line 493	C++
> WebKit.dll!WebCore::jsNodePrototypeFunctionAppendChildBody(JSC::ExecState * state, WebCore::JSNode * castedThis, JSC::ThrowScope & throwScope) Line 860	C++
> WebKit.dll!WebCore::IDLOperation<WebCore::JSNode>::call<&WebCore::jsNodePrototypeFunctionAppendChildBody,WebCore::CastedThisErrorBehavior::Throw>(JSC::ExecState & state, const char * operationName) Line 53	C++
> WebKit.dll!WebCore::jsNodePrototypeFunctionAppendChild(JSC::ExecState * state) Line 866	C++
> [External Code]

[Fujii Hironori]

Created attachment 373312 [details]
WIP patch

This WIP patch doens't work as expected, but sometimes debugger can show full callstack like the following:

> WebKit.dll!WebCore::Node::appendChild(WebCore::Node & newChild) Line 493	C++
> WebKit.dll!WebCore::jsNodePrototypeFunctionAppendChildBody(JSC::ExecState * state, WebCore::JSNode * castedThis, JSC::ThrowScope & throwScope) Line 860	C++
> WebKit.dll!WebCore::IDLOperation<WebCore::JSNode>::call<&WebCore::jsNodePrototypeFunctionAppendChildBody,WebCore::CastedThisErrorBehavior::Throw>(JSC::ExecState & state, const char * operationName) Line 53	C++
> WebKit.dll!WebCore::jsNodePrototypeFunctionAppendChild(JSC::ExecState * state) Line 866	C++
> [External Code]	
> JavaScriptCore.dll!JSC::JITCode::execute(JSC::VM * vm, JSC::ProtoCallFrame * protoCallFrame) Line 38	C++
> JavaScriptCore.dll!JSC::Interpreter::executeProgram(const JSC::SourceCode & source, JSC::ExecState * callFrame, JSC::JSObject * thisObj) Line 845	C++
> JavaScriptCore.dll!JSC::evaluate(JSC::ExecState * exec, const JSC::SourceCode & source, JSC::JSValue thisValue, WTF::NakedPtr<JSC::Exception> & returnedException) Line 149	C++
> JavaScriptCore.dll!JSC::profiledEvaluate(JSC::ExecState * exec, JSC::ProfilingReason reason, const JSC::SourceCode & source, JSC::JSValue thisValue, WTF::NakedPtr<JSC::Exception> & returnedException) Line 164	C++
> WebKit.dll!WebCore::JSExecState::profiledEvaluate(JSC::ExecState * exec, JSC::ProfilingReason reason, const JSC::SourceCode & source, JSC::JSValue thisValue, WTF::NakedPtr<JSC::Exception> & returnedException) Line 81	C++
> WebKit.dll!WebCore::ScriptController::evaluateInWorld(const WebCore::ScriptSourceCode & sourceCode, WebCore::DOMWrapperWorld & world, WebCore::ExceptionDetails * exceptionDetails) Line 133	C++
> WebKit.dll!WebCore::ScriptController::evaluate(const WebCore::ScriptSourceCode & sourceCode, WebCore::ExceptionDetails * exceptionDetails) Line 149	C++
> WebKit.dll!WebCore::ScriptElement::executeClassicScript(const WebCore::ScriptSourceCode & sourceCode) Line 388	C++
> WebKit.dll!WebCore::LoadableClassicScript::execute(WebCore::ScriptElement & scriptElement) Line 123	C++
> WebKit.dll!WebCore::ScriptElement::executeScriptAndDispatchEvent(WebCore::LoadableScript & loadableScript) Line 426	C++
> WebKit.dll!WebCore::ScriptElement::executePendingScript(WebCore::PendingScript & pendingScript) Line 434	C++
> WebKit.dll!WebCore::ScriptRunner::timerFired() Line 131	C++
> [External Code]	
> WebKit.dll!WTF::Detail::CallableWrapper<std::_Binder<std::_Unforced,void (WebCore::ScriptRunner::*&)(),WebCore::ScriptRunner *>,void>::call() Line 52	C++
> WebKit.dll!WTF::Function<void ()>::operator()() Line 79	C++
> WebKit.dll!WebCore::Timer::fired() Line 127	C++
> WebKit.dll!WebCore::ThreadTimers::sharedTimerFiredInternal() Line 129	C++
> WebKit.dll!WebCore::ThreadTimers::setSharedTimer::<unnamed-tag>::operator()() Line 69	C++
> WebKit.dll!WTF::Detail::CallableWrapper<`lambda at ..\..\Source\WebCore\platform/ThreadTimers.cpp:69:41',void>::call() Line 52	C++
> WebKit.dll!WTF::Function<void ()>::operator()() Line 79	C++
> WebKit.dll!WebCore::MainThreadSharedTimer::fired() Line 84	C++
> WebKit.dll!WebCore::TimerWindowWndProc(HWND__ * hWnd, unsigned int message, unsigned __int64 wParam, __int64 lParam) Line 89	C++
> [External Code]	
> WebKit.dll!WebKitMessageLoop::run(HACCEL__ * hAccelTable) Line 94	C++
> MiniBrowserLib.dll!wWinMain(HINSTANCE__ * hInstance, HINSTANCE__ * hPrevInstance, wchar_t * lpstrCmdLine, int nCmdShow) Line 97	C++
> MiniBrowserLib.dll!dllLauncherEntryPoint(HINSTANCE__ * hInstance, HINSTANCE__ * hPrevInstance, wchar_t * lpstrCmdLine, int nCmdShow) Line 115	C++
> MiniBrowser.exe!wWinMain(HINSTANCE__ * hInstance, HINSTANCE__ * hPrevInstance, wchar_t * lpstrCmdLine, int nCmdShow) Line 232	C++
> [External Code]

[Fujii Hironori]

https://docs.microsoft.com/en-us/cpp/assembler/masm/dot-setframe

[Fujii Hironori]

Umm, this doesn't seem an easy task. It manipulates the stack pointer outside of epilogue and prologue.